NASA/SP-2010-577

Evaluation of the NASA Arc Jet 

Capabilities to Support Mission 

Requirements

Office of the Chief Engineer

May 2010
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Preface

NASA accomplishes its strategic goals through human and robotic exploration missions. Many 

of these missions require launching and landing or returning spacecraft with human or return 

samples through Earth’s and other planetary atmospheres. Spacecraft entering an atmosphere are 

subjected to extreme aerothermal loads. Protecting against these extreme loads is a critical 

element of spacecraft design. The safety and success of the planned mission is a prime concern 

for the Agency, and risk mitigation requires the knowledgeable use of thermal protection systems 

to successfully withstand the high-energy states imposed on the vehicle. Arc jets provide groundbased testing for development and flight validation of re-entry vehicle thermal protection 

materials and are a critical capability and core competency of NASA.

The Agency’s primary hypersonic thermal testing capability resides at the Ames Research Center 

and the Johnson Space Center and was developed and built in the 1960s and 1970s. This 

capability was critical to the success of Apollo, Shuttle, Pioneer, Galileo, Mars Pathfinder, and 

Orion. But the capability and the infrastructure are beyond their design lives. The complexes 

urgently need strategic attention and investment to meet the future needs of the Agency. 

The Office of Chief Engineer (OCE) chartered the Arc Jet Evaluation Working Group (AJEWG), 

a team of experienced individuals from across the Nation, to capture perspectives and 

requirements from the arc jet user community and from the community that operates and 

maintains this capability and capacity. This report offers the AJEWG’s findings and conclusions 

that are intended to inform the discussion surrounding potential strategic technical and 

investment strategies. The AJEWG was directed to employ a 30-year Agency-level view so that 

near-term issues did not cloud the findings and conclusions and did not dominate or limit any of 

the strategic options. 

The OCE would like to thank the members of the user community who gave presentations, 

interviews, responded to questions, and offered their vision of the future. The OCE thanks the 

facility managers and personnel who hosted the AJEWG at their Center, conducted tours of their 

arc jet complexes, and gave presentations, answered questions, and offered their vision of the 

future. The OCE also extends its appreciation to the AJEWG for their time and effort in 

developing this report: Anthony Calomino, Lead, GRC; Walt Bruce, LaRC; Peter Gage, Neerim 

Corp.; Dennis Horn, AEDC (Retired); Mike Mastaler, HQ; Don Rigali, DOE (Retired); Judee 

Robey, HQ; Linda Voss, Dell-Perot; Jerry Wahlberg, LaRC and NC State (Retired); and Calvin 

Williams, HQ.

Mike Ryschkewitsch

May 4, 2010
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Executive Summary

The Arc Jet Evaluation Working Group (AJEWG) was chartered by the NASA Office of the 

Chief Engineer to provide an independent technical evaluation of NASA arc jet testing capability 

considering existing test complexes and the need to support planned and future NASA mission 

requirements. Future mission classes considered include human return from low Earth orbit, 

human return from beyond low Earth orbit, both human and robotic exploration of Mars, and 

deep space robotic exploration and Earth return. Arc jet testing support for all mission phases,

from precursor technology maturation through sustaining engineering of operational systems,

was to be included in the evaluation. The AJEWG considered the availability and use of arc jet 

test facilities, focusing on the Johnson Space Center, the Ames Research Center, the Arnold 

Engineering Development Center, and the Boeing Large Core Arc Tunnel, and generated 

findings and conclusions to inform long-term investment strategies for NASA. The AJEWG 

considered use of foreign facilities unacceptable due to restrictions imposed by International 

Traffic in Arms Regulations, security, and lack of control of facility access. The Nation could not 

preserve its leadership in the development and modeling of thermal protection materials if it 

depends on the arc jet testing facilities of a foreign country. The AJEWG findings and 

conclusions are derived from a variety of resources, including a review of maintenance plans, 

site visits, reference documents, and invited presentations from the user community.

The AJEWG determined that proposed NASA missions over the next 30 years will require arc 

jet capabilities beyond what exists today. Based on evaluation of available information, 

described in Section 6.0 of the report, the AJEWG concludes that a new build offers functional 

advantages over upgrading existing aging complexes without appreciable cost penalty when 

considering a 30-year investment. Furthermore, no current facility, including those at Arnold 

Engineering Development Center and the Large Core Arc Tunnel, can deliver the heating rates, 

pressures, and shear levels at the scale and duration needed for cost-effective, weight-efficient,

and reliable design of thermal protection systems for safe return from Mars or near-Earth objects. 

The AJEWG determined that NASA has a critical and strategic need for arc jet ground 

test capability to meet its unique mission set, and must make its own investment to support

future needs.

The NASA arc jet complexes at Johnson and Ames are aging and major infrastructure 

investment decisions must be made soon. The condition of the equipment and infrastructure that 

comprise and support these complexes are typical of research and test systems constructed 30 to 

40 years ago. Maintenance and recapitalization have been erratic due to fluctuating project and 

complex maintenance funding levels, resulting in a mix of old and new equipment. Both 

complexes have identified a near-term need for boiler upgrades; however, both boilers have been 

recently inspected and certified safe to operate and will meet emissions requirements for the next 

5 years. Based on a review of the existing infrastructure, discussions with complex managers,

and the availability metrics, the AJWEG expects that both the Ames and Johnson arc jet 

complexes are capable of sustaining safe operations for a 5-year period, which provides NASA 

with a critical opportunity to institute appropriate action to establish an arc jet complex to meet 

NASA’s 30-year needs. Although the older equipment has been adequately maintained for safe 

operation, the real and increasing risk of a major system failure and extended complex down 

time highlights the need for immediate action.
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Within five years, NASA must be building a single arc jet testing complex with a robust 

infrastructure and capability to support thermal protection system certification for largemass Mars entry and safe return to Earth. 

NASA must start immediately to gain advocacy and establish funding and design plans for the 

test complex infrastructure and perform the technology development needed for advanced 

capability. A design team comprised of NASA, DOD, and industry arc jet experts should be 

convened and tasked to complete preliminary design review for the test complex within 12 

months. The team should identify designs that optimize test efficiency, enhance instrumentation 

access, and improve diagnostic capability for test models. The design team should consider a 

number of possible sites and assess current and expected future restrictions on power, water, 

noise, pollution, and availability of suitable personnel. To optimize operational robustness, the 

team should also consider the potential for natural disasters that could threaten extended 

downtime. A detailed cost analysis for the construction and 40-year operation of the complex for 

all site locations considered should be a primary factor for a final build decision. Once a new 

capability is established, NASA needs to commit to continuous and consistent institutionalized 

funding to avoid the adverse effects of erratic program funding for maintenance and upgrades 

and to maximize value to the Agency.

A focused activity to define complex infrastructure requirements, establish technology 

enhancements and design plans, and acquire financial support and construction approval 

should start immediately and be scheduled to support building within the next 5 years.

Operations at existing complexes should be sustained, until a final investment decision has been 

made and funds obligated, to support current missions and the development of advanced 

capability for the new build. Mothballing either complex is effectively a decision to close that 

complex. Sustaining operation at both complexes offers NASA an opportunity to use existing 

facilities to develop the arc jet technology needed to meet the future capability by exploiting 

expected short-term reductions in arc jet test demand. During this period, no major infrastructure 

investment should be made that is not necessary for safe operation. The AJEWG agrees with a 

cooperative management structure proposed by Johnson and Ames for the two existing 

complexes, as discussed in Section 5.0. The AJEWG noted that current operations staff is a 

highly valuable NASA resource. They possess unique knowledge and skills that are integral to 

successful operation and NASA should maximize the opportunity to retain and transition this 

staff to the new complex. However, also discussed in Section 5.0, the AJEWG concluded that 

current staff levels at both NASA complexes could be lower. To reduce operation costs, an 

independent assessment of minimum staffing levels required for safe and effective operation 

should be completed at both the Ames and Johnson complexes and appropriate reductions 

instituted within a year. 

NASA should maintain testing capability at both the Johnson and Ames arc jet complexes 

for the time period required to begin building the new complex. NASA should reduce 

current staff levels at Johnson and Ames and manage a scheduled phase-out plan that 

offers an efficient transition to test operation at the new complex.

The AJEWG considers these immediate actions to be positive steps that will transition NASA 

from having a high-risk reliance on the existing, aged arc jet test infrastructure and capability to 

a single robust complex with improved and cost-effective capability that meets future critical 

testing needs for NASA and the Nation for the next 30 years.
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Table of Contents

PREFACE ....................................................................................................................................................................2

EXECUTIVE SUMMARY .........................................................................................................................................3

1.0 INTRODUCTION ..........................................................................................................................................9

1.1 SCOPE ...........................................................................................................................................................9

1.2 BACKGROUND...............................................................................................................................................9

1.3 EVALUATION APPROACH ............................................................................................................................10

1.4 CURRENT CHANGING CLIMATE FOR FUNDING AND REQUIREMENTS ..........................................................11

1.5 DOCUMENT ORGANIZATION .......................................................................................................................11

2.0 ENGINEERING USES AND ACCOMPLISHMENTS OF ARC JETS..................................................12

2.1 MATERIAL RESPONSE MODELING...............................................................................................................14

2.2 COMPUTATIONAL FLUID DYNAMICS MODELING ........................................................................................15

2.3 MAXIMIZING VALUE OF ARC JET TESTING .................................................................................................17

2.4 SUMMARY...................................................................................................................................................18

3.0 MISSION/FUTURE REQUIREMENTS/NATIONAL NEEDS...............................................................19

3.1 RETURN FROM LOW EARTH ORBIT .............................................................................................................19

3.2 MARS ENTRY..............................................................................................................................................21

3.3 EARTH RETURN FROM BEYOND LEO..........................................................................................................22

3.4 EXPLORATION OF VENUS AND OUTER PLANETS .........................................................................................24

3.5 EXPLORATION OF TITAN .............................................................................................................................25

3.6 MATERIAL TECHNOLOGY ADVANCEMENT..................................................................................................26

4.0 CURRENT CAPABILITIES AND LIMITATIONS.................................................................................28

4.1 BASIC ARC JET OPERATION ........................................................................................................................29

4.2 SIMULATION REGIME..................................................................................................................................30

4.3 STAGNATION TESTING ................................................................................................................................32

4.4 SHEAR TESTING ..........................................................................................................................................34

4.5 PANEL TESTING ..........................................................................................................................................37

4.6 POWER SUPPLY...........................................................................................................................................39

4.7 SUMMARY...................................................................................................................................................40

5.0 ARC JET CAPACITY.................................................................................................................................41

5.1 WORKFORCE...............................................................................................................................................41

5.2 THROUGHPUT .............................................................................................................................................42

5.2.1 Ames Research Center...........................................................................................................................42

5.2.2 Johnson Space Center............................................................................................................................44

5.2.3 Air Force Arnold Engineering Development Center.............................................................................44

5.2.4 Boeing Large Core Arc Tunnel..............................................................................................................45

5.2.5 Testing Costs..........................................................................................................................................45

5.2.6 Lunar Environment Arc Jet Facility ..........................................................................................................45

5.3 INFRASTRUCTURE CONDITION ....................................................................................................................46

5.3.1 Ames Research Center...........................................................................................................................46

5.3.2 Johnson Space Center............................................................................................................................48

5.3.3 Air Force Arnold Engineering Development Center.............................................................................50

5.4 MOTHBALLING THE EXISTING ARC JET COMPLEXES AT ARC AND JSC .....................................................51

5.5 THROUGHPUT EFFICIENCIES .......................................................................................................................52

5.6 SUMMARY...................................................................................................................................................52

6.0 CONCLUSIONS AND PLAN FORWARD FOR NASA INVESTMENT IN ARC JET FACILITIES54

6.1 REQUIRED CAPABILITY...............................................................................................................................54

6.2 OPTIONS FOR NEW CAPABILITY..................................................................................................................57
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6.3 CONSIDERATIONS FOR UPGRADING TO FUTURE CAPABILITY......................................................................60

6.4 TECHNOLOGY DEVELOPMENT REQUIREMENTS...........................................................................................61

6.5 CERTIFICATION AND MISSION ASSURANCE ROADMAP ...............................................................................63

6.6 TRANSITION AND INSTITUTIONAL MANAGEMENT.......................................................................................63

6.7 DEVELOPMENT SCHEDULE..........................................................................................................................64

6.8 SUMMARY...................................................................................................................................................65

7.0 FINDINGS AND CONCLUSIONS.............................................................................................................67

APPENDIX A: ACRONYMS...................................................................................................................................70

APPENDIX B: GLOSSARY.....................................................................................................................................73

APPENDIX C: REFERENCES................................................................................................................................74

APPENDIX D: STUDY INFORMATION ..............................................................................................................75

APPENDIX E: AJEWG TEAM BIOS.....................................................................................................................78

APPENDIX F: CURRENT ARC JET CAPABILITIES........................................................................................85

AMES RESEARCH CENTER ARC JET COMPLEX.........................................................................................................85

Interaction Heating Facility (IHF) .....................................................................................................................86

Aerodynamic Heating Facility (AHF).................................................................................................................90

Panel Test Facility (PTF) ...................................................................................................................................93

Turbulent Flow Duct (TFD)................................................................................................................................95

JOHNSON SPACE CENTER ARC JET COMPLEX ..........................................................................................................96

Test Position-1 (TP-1).........................................................................................................................................98

Test Position-2 (TP-2).......................................................................................................................................100

ARNOLD ENGINEERING DEVELOPMENT CENTER ARC JET COMPLEX.....................................................................100

BOEING LCAT ARC JET COMPLEX ........................................................................................................................103

APPENDIX G: INVESTMENT OPTIONS...........................................................................................................106

1.1 CLOSE THE EXISTING ARC JET COMPLEXES AT JSC AND ARC ........................................................................106

1.2 CONTINUE OPERATING BOTH ARC JET COMPLEXES BUT PROVIDE NO ADDITIONAL INVESTMENT FOR 

REVITALIZATION AND RECAPITALIZATION ............................................................................................................107

1.3 MAKE BOTH ARC AND JSC COMPLEXES HEALTHY, INCLUDING INVESTMENT FOR REVITALIZATION AND 

RECAPITALIZATION................................................................................................................................................107

1.4 CLOSE THE ARC COMPLEX AND MAKE THE JSC COMPLEX HEALTHY ............................................................108

1.5 CLOSE THE JSC COMPLEX AND MAKE THE ARC COMPLEX HEALTHY ............................................................108

APPENDIX H: WORK STATEMENT.................................................................................................................110

List of Figures

FIGURE 2.1. PERFORMANCE COMPARISON OF VARIOUS GROUND-BASED SIMULATION FACILITIES .............................13

FIGURE 2.2. DESIGN MARGIN POLICY FOR PROTECTING AGAINST BOND-LINE OVER TEMPERATURE. ............................14

FIGURE 2.3. CFD WAS USED TO IDENTIFY SOURCE OF INTERFERENCE AND TO IDENTIFY A SHAPE CHANGE THAT 

ADDRESSES THE PROBLEM ...................................................................................................................................17

FIGURE 3.1. EXISTING ARC JETS PROVIDE ADEQUATE CAPABILITY FOR LEO RETURN VEHICLES ..................................20

FIGURE 3.2. HEAT FLUX AND SHEAR LEVELS FOR MDR, LDR AND LEO RETURN TRAJECTORIES ................................23

FIGURE 3.3. ENTHALPY LEVELS FOR MDR TRAJECTORY ARE DOUBLE THE CAPABILITY OF EXISTING FACILITIES ........23

FIGURE 3.4. PROPOSED TESTING REQUIREMENTS FOR QUALIFICATION OF AN ABLATIVE TPS.......................................26

FIGURE 4.1. ARC JET SCHEMATIC .................................................................................................................................29

FIGURE 4.2. ARC JET FACILITY COMPONENTS...............................................................................................................30

FIGURE 4.3. COMPARISON OF NASA, AEDC, AND BOEING ARC JET FACILITY PERFORMANCE WITH SEVERAL NOMINAL 

EARTH RETURN TRAJECTORIES. ...........................................................................................................................31

FIGURE 4.4. STAGNATION POINT HEAT FLUX VS. STAGNATION PRESSURE FOR A 10-CM HEMISPHERE...........................33
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FIGURE 4.5. STAGNATION FACILITY COMPARISON, CENTERLINE ENTHALPY VS. WALL PRESSURE FOR 10-CM 

HEMISPHERE. .......................................................................................................................................................34

FIGURE 4.6. SHEAR TEST FACILITY COMPARISON, COLD WALL HEAT FLUX VS. WALL PRESSURE ..................................35

FIGURE 4.7. SHEAR TEST FACILITY COMPARISON, COLD WALL HEAT FLUX VS. SHEAR FORCE.......................................36

FIGURE 4.8. SHEAR TEST FACILITY CAPABILITY COMPARED WITH SEVERAL BALLISTIC TRAJECTORIES (TRAJECTORIES 

SHOWN WITH FULL MARGINS). .............................................................................................................................37

FIGURE 4.9. PANEL TEST CAPABILITY SHOWING HEAT FLUX VS. PRESSURE. .................................................................38

FIGURE 4.10. PANEL TEST CAPABILITY SHOWING HEAT FLUX VS. PRESSURE WITH ADDITION OF THE TFD...................39

FIGURE 5.1. ARC ARC JET COMPLEX CUSTOMER BASE .................................................................................................43

FIGURE 5.2. AEDC PROPOSED UPGRADE TO MID-PRESSURE ARC HEATER ....................................................................51

FIGURE 6.1. ESTIMATED 30-YEAR COST OF OPTIONS ....................................................................................................60

FIGURE F-1. AERIAL VIEW OF AMES ARC JET COMPLEX. ............................................................................................85

FIGURE F-2. AMES INTERACTION HEATING FACILITY (IHF). .......................................................................................87

FIGURE F-3. 10-DEGREE CONICAL NOZZLE SEGMENTS FOR IHF..................................................................................87

FIGURE F-4. MODEL INJECTION SYSTEM SHOWING TWO STING ARMS. .......................................................................87

FIGURE F-5. IHF STAGNATION PERFORMANCE FOR COLD WALL HEAT FLUX VS. PRESSURE. .....................................88

FIGURE F-6. IHF STAGNATION PERFORMANCE FOR CENTERLINE ENTHALPY VS. PRESSURE. ......................................88

FIGURE F-7. IHF WEDGE TEST CAPABILITY ON A 4-IN X 4-IN SAMPLE, HEAT FLUX VS. WALL PRESSURE. .................89

FIGURE F-8. IHF WEDGE TEST CAPABILITY ON A 4-IN X 4-IN SAMPLE, HEAT FLUX VS. SHEAR FORCE. ......................89

FIGURE F-9. IHF PANEL TEST PERFORMANCE ON A 24-IN X 24-IN SAMPLE, HEAT FLUX VS. WALL PRESSURE............90

FIGURE F-10. AMES AERODYNAMIC HEATING FACILITY (AHF)..................................................................................91

FIGURE F-11. AHF MODEL INJECTION SYSTEM............................................................................................................91

FIGURE F-12. AHF STAGNATION PERFORMANCE, HEAT FLUX VS. PRESSURE..............................................................92

FIGURE F-13. AHF STAGNATION PERFORMANCE, CENTERLINE ENTHALPY VS. PRESSURE..........................................92

FIGURE F-14. PANEL TEST FACILITY TEST CABIN SHOWING SEMI-ELLIPTIC NOZZLE AND TEST PANEL......................93

FIGURE F-15. PTF PANEL TEST PERFORMANCE ON A 24-IN X 24-IN SAMPLE, HEAT FLUX VS. WALL PRESSURE. ........94

FIGURE F-16. TPTF PANEL TEST PERFORMANCE ON A 4-IN X 4-IN SAMPLE, HEAT FLUX VS. WALL PRESSURE...........94

FIGURE F-17. TPTF TEST PERFORMANCE ON A 4-IN X 4-IN SAMPLE, HEAT FLUX VS. SHEAR FORCE...........................95

FIGURE F-18. TURBULENT FLOW DUCT. ......................................................................................................................96

FIGURE F-19. TFD PERFORMANCE ON A 2-IN X 9-IN SAMPLE, HEAT FLUX VS. WALL PRESSURE.................................96

FIGURE F-20. SKETCH OF THE JSC ARC JET COMPLEX.................................................................................................97

FIGURE F-21. JSC ARC JET FACILITY SHOWING TP-1 ON THE LEFT AND TP-2 ON THE RIGHT.....................................98

FIGURE F-22. TP-1 CHANNEL NOZZLE SHOWING THREE TEST LOCATIONS. ................................................................99

FIGURE F-23. TP-1 PANEL TEST PERFORMANCE FOR HEAT FLUX VS. WALL PRESSURE. .............................................99

FIGURE F-24. TP-2 40-IN. EXIT DIAMETER NOZZLE CONFIGURATION........................................................................100

FIGURE F-25. AEDC H2 HUELS TYPE ARC HEATER..................................................................................................101

FIGURE F-26. VIEW OF AEDC H2 FACILITY TEST CABIN AND MODEL INJECTION SYSTEM. ......................................101

FIGURE F-27. H2 WEDGE TEST PERFORMANCE COMPARED WITH NASA WEDGE TEST PERFORMANCE. ..................102

FIGURE F-28. H2 STAGNATION TEST PERFORMANCE COMPARED WITH NASA FACILITY PERFORMANCE.................102

FIGURE F-29. VIEW OF BOEING LCAT FACILITY. ......................................................................................................103

FIGURE F-30. VIEW OF LCAT TEST CABIN INTERIOR AND MODEL INJECTION SYSTEM.............................................103

FIGURE F-31. LCAT STAGNATION PERFORMANCE OF HEAT FLUX VS. PRESSURE. ....................................................104

FIGURE F-32. LCAT STAGNATION PERFORMANCE OF CENTERLINE ENTHALPY VS. PRESSURE..................................104

FIGURE F-33. LCAT WEDGE TEST PERFORMANCE, HEAT FLUX VS. WALL PRESSURE. .............................................105

FIGURE F-34. LCAT WEDGE TEST PERFORMANCE, HEAT FLUX VS. SHEAR FORCE...................................................105

List of Tables

Table 3.1. Parameters..................................................................................................19

Table 3.2. Representative Earth Entry Conditions for Various Missions.......................................24

Table 5.1. Throughput for ARC Arc Jet Complex..................................................................43

Table 5.2. Throughput for JSC Arc Jet Complex...................................................................44

Table 5.3. The Cost of Arc Jet Testing..............................................................................45
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Table 5.4. ARC Arc Jet Complex Subsystem Summary..........................................................47

Table 5.5. JSC Arc Jet Complex Subsystem Summary...........................................................49

Table 5.6. JSC Arc Jet Complex System Upgrades...............................................................49

Table 6.1 Future Arc Jet Needs: Summary of Responses from End Users.....................................55

Table 6.2. Regional Construction Cost Index.......................................................................59

Table 6.3. Estimated 30-Year Costs for a New Arc Jet Complex................................................60

Table 6.4. Notional Schedule for Transition to New Arc Jet Capability........................................66

Table F-1. ARC Arc Jet Complex Active Configuration Summary.............................................87

Table G-1. Comparing Costs of Various Options.................................................................111

Table H-1: Program and Project Requirements for Arc Jet Capability........................................114
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1.0 Introduction

The Arc Jet Evaluation Working Group (AJEWG) was chartered to provide engineering support 

to the NASA Chief Engineer, Mike Ryschkewitsch, in evaluating the availability and use of 

hypersonic thermal arc jet test facilities to meet NASA’s planned and future mission 

requirements over the next 30 years. NASA has a sustained mission to develop and certify entry 

systems technology for these mission categories:

 LEO return

 Mars entry 

 Earth return from beyond LEO 

 Exploration of Venus and outer planets

 Titan

In addition, the Nation has a sustained interest in long-duration hypersonic flight and airbreathing space access, including the activities of the National Partnership for Aeronautical 

Testing (NPAT) and the Hypersonic Propulsion Integrated Testing Team (HPITT). Congress 

mandated that DOD and NASA work together on hypersonics with the Joint Technology Office 

on Hypersonics (JTOH).1

The AJEWG was to provide findings to inform possible long-term investment strategy 

alternatives for NASA’s arc jet capability. 

1.1 Scope

The AJEWG was asked to consider both NASA and non-NASA arc jet hypersonic thermal test 

facilities to meet NASA mission requirements. The AJEWG looked at existing facilities and 

evaluated the capabilities of facilities capable of supporting large-scale thermal protection 

system (TPS) development and certification. Smaller research and development arc jets and arc 

jets used for materials screening at the NASA Langley Research Center (LaRC), the Arc Heated 

Scramjet Test Facility (AHSTF), and the Hypersonic Material Environmental Test System 

(HyMETS) were not considered viable possibilities. The AJEWG considered it unrealistic to rely 

on foreign facilities like Scirocco in Italy to support NASA’s leadership in development and 

modeling of TPS materials. Aside from issues of logistics and control of schedule, restrictions 

imposed by the International Traffic in Arms Regulations (ITAR) and security considerations 

make use of the complex untenable.

1.2 Background

Arc jets facilities are designed to simulate conditions for space vehicles entering through a 

planetary atmosphere. They provide ground-based testing for re-entry vehicle thermal protection 

materials, by electrically heating air or other test gases to a flight-like enthalpy. This high-energy 

 

1 The John Warner National Defense Authorization Act for Fiscal Year 2007, P.L. 109-364, Section 218, directed 

the Secretary of Defense to establish within the Office of the Secretary of Defense the JTOH. The JTOH is to 

coordinate with the programs on hypersonics of the National Aeronautics and Space Administration and is 

required to report to the Congressional Defense Committees a roadmap for the hypersonics programs of the 

Department of Defense every two years. The first roadmap came out in February 2008.
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gas is expanded through a nozzle at high velocity into a vacuum test chamber where a test article 

or articles are exposed to the heat rate, pressure, and shear that simulate the conditions of a given 

flight trajectory.

The Ames Research Center (ARC) and the Johnson Space Center (JSC) facilities were brought 

online in the mid-1960s for development of thermal protection material and mission support. The 

JSC facilities were funded through the Space Transportation System (STS) Program (U.S. Space 

Shuttle program) until 2002, but the amount of sustaining engineering testing at that time was 

significantly decreased, and the JSC arc jets were designated to be mothballed. Following the 

Columbia accident, both JSC and ARC facilities were heavily utilized in the investigation and in 

the subsequent Return to Flight (RTF) activities. The Columbia Accident Investigation Board 

(CAIB) recommendations included development of a TPS repair capability. The arc jets played a 

major role in demonstrating the effectiveness of proposed repairs, including tests of “the fullscale repair components at maximum heating for the full duration of the flight trajectory.” [ARC, 

Basis of Need] (References are listed in Appendix C: References.)

1.3 Evaluation Approach

The Office of the Chief Engineer (OCE) asked the AJEWG to identify and document 

requirements for NASA missions and aeronautics research that would necessitate the use of arc 

jet facilities that perform hypersonic thermal testing and to evaluate these requirements against 

the performance capability and throughput capacities of existing facilities. 

To accomplish the objective, the AJEWG conducted site visits at both JSC and ARC and listened 

to presentations on the facilities and from users. (See Appendix D: Study Information.) The 

working group also reviewed previous arc jet evaluations, relevant reference documents, current 

maintenance plans, and written justifications and plans for the proposed upgrade to the Lunar 

Environment Arc Jet Facility (LEAF). 

During the site visits, interviews were also conducted with key technical leads working all stages 

of the TPS life cycle, from entry system precursor technologies, through flight vehicle 

development, to sustaining engineering of operational vehicles. On site, the working group 

observed and assessed existing arc jet complex support infrastructure, facility hardware, test 

diagnostics, workforce, operational efficiency, maintenance schedules, and upgrade 

requirements. 

Arc jet operations at the Arnold Engineering Development Center (AEDC) and Boeing Large 

Core Arc Tunnel (LCAT) were reviewed by interviewing key operators from both complexes. A 

visual comparison of the capabilities and trajectories covered by these different facilities is made 

in Section 4.0, Current Capabilities. 

The AJEWG also assessed requirements for future arc jet testing capability and capacity by 

interviewing current and potential users of arc jet services from the NASA Exploration Systems, 

Space Operations, Science, and Aeronautics Mission Directorates; the Air Force; and SpaceX 

and commercial organizations contracted with NASA for entry systems.

The amount of testing accomplished, or throughput; planned maintenance; and facility upgrades 

were considered. The findings and conclusions of this analysis are captured in Section 5.0 of this 

report. The way forward for a possible investment strategy for NASA’s hypersonic thermal test 

facility capability is considered in Section 6.0.
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The AJEWG members were selected from among national experts in arc jet technology and entry 

technology to provide an unbiased perspective and a focused, independent evaluation to inform 

NASA’s long-term investment strategy toward arc jet capability. (See Appendix E: Team Bios.)

1.4 Current Changing Climate for Funding and Requirements

The assignment of this evaluation report occurred at a time of flux in Agency mission 

requirements and funding. The context for this report includes the recent establishment of the 

Facilities Program Board (FPB), whose charter is to provide a comprehensive Agency facility 

strategic direction. (“Facilities” is used here to indicate Agency buildings, assets, and other 

infrastructure. The arc jet community uses “complex” and “facility” interchangeably, but this 

document attempts to consistently use “complex” to refer to the arc jets and their supportive 

infrastructure and “facility” to refer to an arc jet tunnel.) The FPB established an Agency facility 

strategy to reduce the proportion of facilities within the Agency that are older than 40 years and 

beyond their design life. Despite such program planning challenges as the Constellation 

redirection and retirement of the U.S. Space Shuttle, the AJEWG concluded that NASA1s arc jet 

capability serves a persistent strategic need for the Agency.

1.5 Document Organization

This report lays out the engineering uses of arc jets in Section 2.0. Section 3.0 describes the 

requirements of different mission categories. The current state of the main national arc jet 

complexes is described in Section 4.0, along with the gaps in arc jet technology that should be 

addressed. 

The analysis of the throughput and a comparison of the workforce at different arc jet complexes 

is captured in Section 5.0. Section 6.0 explores investment options for the Agency, focusing on 

future capability and capacity that would meet the needs for a safe return from Mars. Findings 

and conclusions appear at the end of each section and are collected in the final Section 7.0 of the 

report.
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2.0 Engineering Uses and Accomplishments of Arc Jets

Spacecraft entering into a planet’s atmosphere at high velocity are subjected to extreme 

aerothermal loads. Protecting against these extreme loads is a critical element of spacecraft 

design. With the possible exception of very limited locations on Shuttle, entry vehicle thermal 

protection failure is single point and catastrophic to mission success. Human-rating requirements 

for space systems generally specify that systems should be fault tolerant to catastrophic events 

[NPR 8705]. Fault tolerance design avoids failure through redundancy or other compensation. 

However, vehicle TPS is often exempted from this requirement because redundancy is not 

possible. The risk is instead controlled through defined standards for increased design margin. 

For robotic missions, mission assurance requirements will drive similar approaches to TPS for 

increased margin. The environments that arc jets can simulate allow material engineers and 

spacecraft designers to:

• Design, develop, qualify, and certify spacecraft thermal protection systems (TPS), 

including the heat shield, backshell, and seal design;

• Screen and develop new thermal protection materials;

• Certify vehicles for flight and establish performance margins for the TPS design during 

entry, descent, and landing (EDL);

• Re-qualify materials that have new manufacturing facilities, processes, vendors, or 

constituent materials;

• Perform sustaining engineering throughout the TPS mission life, including advancing and 

improving the TPS;

• Test, analyze, and perform trades to support decisions on safe return or repair alternatives 

to on-orbit anomalies in the TPS; and

• Support the investigation of TPS failures or mishaps.

For more than 40 years, arc jet testing has been the primary basis for characterizing TPS in 

support of material development and response model validation. Every NASA atmospheric entry 

mission has relied on arc jet testing for TPS development. Arc jet facilities provide the only 

ground-based means of simulating entry heating rates in a reacting flow environment for flightrelevant durations, as shown in the Figure 2.1 below. Although shock tunnels can more 

accurately simulate the aerothermal environment, they do so for too short a period to permit 

accurate assessment of the material response to that environment. Exposure durations 

approximating those expected during flight are required to screen and qualify thermal protection 

materials. Screening typically subjects material samples to flight-relevant heat fluxes and 

pressures, but rarely addresses all aspects of the load environment that might contribute to 

material failure. In the Apollo era, for example, when arc jet power levels did not exceed 20 

MW, stagnation testing of small models was performed, but shear testing of large models was 

not attempted.
Evaluation of Arc Jet Facilities Report

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Figure 2.1. Performance Comparison of Various Ground-based Simulation Facilities

[Curry, Past Experience Using Arc Jet Testing for Human Spacecraft TPS]

Thermal protection failure modes are typically of two types: bond-line over temperature due to 

under-predicted heat loads or over-predicted material response, or catastrophic overheating due 

to mechanical failure [Steltzner, Mars Exploration Program Use Profile]. Bond-line temperature 

can generally be margined by increasing material thickness, at the expense of increased mass.

Arc jet testing provides data for detailed material response models that can reduce uncertainty 

and the magnitude of thickness margins. Arc jets can also uncover mechanical failure modes 

including erosion, spallation, and loss of liquid layer due to shear or failure around a heat shield 

penetration. Heat shield penetration failures are difficult to identify, characterize, and control, but 

arc jet testing can help to expose subsystem feature failure modes early in the design. 

In the recent Constellation TPS Advanced Development Project, a formal margins policy, which 

is summarized in Figure 2.2 below, was generated to support estimation of subsystem reliability, 

but it addresses only a bond-line over temperature failure mode. Arc jet testing was also

conducted to provide qualitative information on other failure modes, including local burn 

through from damage, flow within a porous low-density ablator material, and flow ingestion due 

to seal failure.

5,000

10,000

15,000

20,000

10 10 10 10 10 1 10 10 10 10 -5 -4 -3 -2 -1 2 3 4

Seconds

Microseconds Milliseconds Seconds Minutes Hours

•5

0

10

15

20

0

1

2

3

4

6

8

10

Shock Tunnels

Operating Limit of 

Non-Arc Heated Tunnels

Hotshots Arc Heated Tunnels

Shock Tubes

VKI Longshot

Gun Tunnels

Hypervelocity

Tunnel 9

Ludweig Tubes

Blowdown

Tunnels

Continuous

Tunnel

Limit

ONERA

R4CII

Flow Duration

Total Enthalpy (1000 Btu/lbm)

Equivalent Velocity (1000 ft/sec)

Stagnation Temperature, o

R
Evaluation of Arc Jet Facilities Report

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Figure 2.2. Design margin policy for protecting against bond-line over temperature.

[Wright, Anticipated Arc Jet Usage]

2.1 Material Response Modeling

The design and qualification of thermal protection materials for entry vehicles and probes 

requires consideration of complex thermal and aerodynamic loads, which are strongly affected 

by the chemical state of the atmospheric gases and their interaction with the vehicle surface. The 

primary driving need for NASA to have arc jet test capability is to support the development of 

thermal protection materials, and the qualification of those materials for flight, by providing the 

best possible ground test simulation of the flight environment. Extensive arc jet tests have 

supported the development of all thermal protection materials used by NASA. Concurrent with 

material development, numerous arc jet tests were needed to anchor response models, which are 

used to assess material behavior and establish design margins. The development of thermal 

protection materials and response models will be persistent strategic needs for NASA well into 

the future. Arc jets provide essential ground test support for these needs. 

The selection of appropriate TPS material is driven by mission environment and thermal 

management needs of a vehicle. Material selection is typically governed by entry conditions for 

peak heat flux, stagnation pressure, and shear force; whereas material thickness is dictated by the 

integrated heat load and bond-line temperature capability. For modeling purposes, the total 

calculated heat flux must include augmented heating from surface catalytic reactions, roughness 

effects, turbulent flow, and shock layer radiation. Thermal protection materials basically fall into 

either a single-use or multi-use category. Single-use materials are typically ablators, which 

accommodate high-entry heat load conditions, 100 to 30,000 W/cm2

, through phase change, 

mass loss, and char radiation. Multi-use materials are typically refractory materials that manage 
Evaluation of Arc Jet Facilities Report

15

more moderate heating conditions, 10 to 100 W/cm2, by radiating heat back into a flow field with 

limited chemical reaction or mass loss. 

For single-use materials, modeling ablation is extremely complex because the process often 

involves pyrolysis of organic constituents, in-depth production of volatile gases, and oxidationreduction of carbon and silicon. Therefore, ablation behavior is strongly affected by material 

constituents, in-depth microstructure, and surface interaction with the entry flow [Laub et al., 

Past Experience: A Different Perspective]. The complexities of phase change at the pyrolysis 

zone, diffusion of gases through a char layer, and gas ejection into the flow boundary layer 

present significant challenges to state-of-the-art TPS design methodology. Current design models 

that are used to characterize ablators for heat shields rely on phenomenological calibration with a 

database of arc jet test results. Although no ground-based thermal test can simulate actual flight 

conditions, the high-temperature reacting flow within an arc jet is recognized as the best 

capability for characterizing ablator response and calibrating design models.

A current limitation with ablation modeling is the often important design requirement to 

characterize failure thresholds. Unfortunately, the rigorous experiments needed to define those 

thresholds and identify critical failure mechanisms are rarely performed. As a result, defining 

design “margin” is quite arbitrary since the conditions leading to failure are not known

[Venkatapathy et al., Capabilities Needed]. Improved understanding of the physical processes 

underlying ablation will enable a greater understanding of the margin between safe operation and 

failure. More accurate models combined with a fundamental understanding of ablator failure 

physics may be the only means of reducing heat shield mass without sacrificing operational 

reliability. Accomplishing this end will require carefully controlled arc jet experiments.

In contrast, with ablators, the failure thresholds for multi-use materials are typically well known,

due in large part to the fact that heating loads are moderate and material property changes are 

minor after successive mission exposures. Although far simpler than ablator materials, arc jet 

testing is still critical for characterizing multi-use materials and calibrating design models. 

Multiple exposures are needed to support life cycle analyses, which rely on known and wellcharacterized failure thresholds. Multi-use materials are tested to establish a failure threshold and 

the heat shield is then designed to operate with a safe margin from that threshold. This design 

approach played a strong role in the CAIB failure reconstruction effort and the subsequent RTF 

activities. Based on CAIB recommendations, extensive arc jet tests were performed to assess the 

thermal protection system’s ability to sustain flight debris damage and safely return to Earth.

2.2 Computational Fluid Dynamics Modeling

Computational Fluid Dynamics (CFD) is used routinely in TPS design. Reacting flow codes, 

such as Data-Parallel Line Relaxation (DPLR) and Laura, are used to predict environments 

around the vehicle throughout entry. The predicted thermal, pressure, and shear loads are input to 

material response codes, such as Fan/Inlet Acoustic Technology (FIAT), Cryogenic Moisture 

Apparatus (CMA), and Structural and Thermal Analysis Branch (STAB), to calculate the 

thickness of material required to keep the underlying vehicle structure at acceptable 

temperatures. These same CFD codes can be applied to simulate the flow in an arc jet facility. 

Good correlation between simulated and measured conditions in the arc jets generates confidence 

in the predictive power of the CFD codes and strengthens the traceability for flight simulation. 

Furthermore, success in modeling the flow in these facilities may extend their role beyond data 

generation for material characterization and into aerothermodynamic flow testing.
Evaluation of Arc Jet Facilities Report

16

Since CFD does not address material response (which is modeled separately), it is unrealistic to 

imagine that CFD can replace ground testing for TPS design. Instead, CFD can be used in two 

ways to improve the material response information that is generated in arc jet tests:

• Reduce uncertainty in the environment to which the model is exposed;

• Predict conditions for a range of arc jet power and mass flow settings, to assist in 

designing a test series that subjects the material to conditions that exercise all failure 

modes

The current state of the art in facility simulation does not model the arc heater directly, but 

assumes that it provides high-enthalpy gas into a plenum, and this slug of gas is expanded 

through a convergent-divergent nozzle into the test section. This way, the computational process 

is no different than one would employ for hypersonic wind tunnels, although the thermochemical 

modeling of the gas is considerably more complex. Arc-heated flow fields are computed and 

calibrated against calorimetric and pitot measurements, and optical measurements (when 

available). Apart from providing details of the flow fields and flow structures, the important 

results of the simulations are the nozzle centerline total enthalpy (a key parameter used in 

computing a material’s thermal response), shear stress, and hot-wall heat flux, all three of which 

are not measured directly in arc jet tests. By reducing the uncertainty in these parameters, the 

CFD supports more precise modeling of material response sensitivity to these quantities.

The contributions of CFD can be enhanced through greater use of flow diagnostics in the arc jet 

facilities, both in the plenum and the test section. Techniques such as optical emission 

spectroscopy and laser-induced fluorescence (LIF) provide knowledge of the thermochemical 

state of the gas/gas mixture and produce valuable information on flow non-uniformities and 

asymmetries that are currently not modeled. Measurement of thermal losses in the core will 

characterize the validity of the current assumption that the core is adiabatic: if measurements 

indicate significant losses, the assumption will need to be modified.

Apart from characterizing the flow in a particular test, CFD can be used to design models and 

test conditions that produce desired heating, pressure, and shear at the model surface. An early 

example of successful three-dimensional flow modeling [Prabhu, Modeling as an Alternative] is 

illustrated in Figure 2.3 below. A nose tip model at angle of attack had serious flow interference 

at the base of the model. Through a series of simulations for a range of sting and model shapes, 

CFD provided insight into a geometry change that fixed the interference issue.

It is anticipated that CFD will be used more routinely in the future to design models that 

maximize the flight relevance of conditions produced in an arc jet facility of a given capability. 
Evaluation of Arc Jet Facilities Report

17

Figure 2.3. CFD was used to identify source of interference 

and to identify a shape change that addresses the problem

[Prabhu, Modeling as an Alternative]

2.3 Maximizing Value of Arc Jet Testing

TPS design is typically regarded as trading subsystem reliability against mass. This is a 

reasonable perspective when failure mechanisms are well understood, and the required margin is 

driven by the level of uncertainty, both in the applied load and the material response. 

Instrumentation and flow diagnostic schemes that measure in-situ arc jet conditions can drive 

down uncertainty in the applied load. Techniques that provide a more detailed view of material 

response, including species identification downstream of the test article, video of the model 

surface that indicates time-accurate ablation behavior, and interior instrumentation of the test 

article can provide physical insight to drive improvements in the material and the response 

model. 

Several flow diagnostic tools have been available for two decades, and low-level research 

activities have been conducted for much of that period, but the diagnostics have not been 

integrated into standard arc jet test practices. This situation appears to be largely driven by the 

lack of access that researchers have had to the arc jet facilities, due to a lack of funding, and to 

higher prioritization being given to tests that directly support mission development and 

operations. Diagnostics have not been sufficiently mature to be adopted by individual missions. 

Strategic management of arc jet facilities as agency assets can reprioritize instrumentation 

development to increase the value of arc jet testing for all missions.

Where failure mechanisms are not fully characterized, additional mass may not improve 

reliability. A failure that quickly removes material after it is initiated, such as shear-induced 

erosion, or one which bypasses the bulk material, such as failure of gap fillers, must be addressed 

by altering the design concept rather than by simply increasing thickness. A comprehensive 

margin policy must address all failure modes, which requires testing that establishes performance 

bounds for all modes. Such testing has not been routinely conducted by missions, which are 

primarily concerned with performance at, or slightly above, the conditions predicted for their 

specific mission trajectories. The scope of screening tests can be expanded and the level of 

instrumentation can be increased, to identify and understand failure mechanisms. Comprehensive 
Evaluation of Arc Jet Facilities Report

18

failure investigation can be conducted as part of a material development activity. As with 

instrumentation and facility improvements, such testing is best managed at the agency level, to 

establish a suite of fully characterized materials that are available to all missions. 

2.4 Summary

Finding 2.1: Arc jet testing has proven to be a core competency and required capability of 

NASA. 

Finding 2.2: Every NASA atmospheric entry mission has relied on arc jet testing for TPS 

development.

Finding 2.3: Arc jet facilities provide the only ground-based means of simulating entry heating 

rates in a reacting flow environment for flight-relevant durations.

Finding 2.4: Ablator design policy currently applies large margins to cover uncertainty in 

applied loads and material response. Improvements in arc jet diagnostics and test article 

instrumentation can reduce uncertainties and hence reduce margins.

Conclusion 2.1: Existing ablator design policy is incomplete, because some failure modes are 

not fully understood, so their contribution to system reliability is not quantified. More rigorous 

examination of material failure modes will enable more defensible mission assurance 

assessment. Characterization of failure modes is better managed as a material development 

activity rather than being conducted for individual missions. 

Conclusion 2.2: Currently available diagnostic capabilities and instrumentation techniques 

should be infused into NASA arc jet standard practice. This infusion is best managed as an 

Agency strategic investment rather than as a programmatic responsibility.
Evaluation of Arc Jet Facilities Report

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3.0 Mission/Future Requirements/National Needs

The thermal protection needs for different mission classes are strongly affected by the entry 

velocities and atmospheric properties that prevail for each class. The mission parameters that 

drive arc jet capability are summarized in Table 3.1 below and discussed in more detail in the 

following subsections.

The acceptable level of risk and the certification strategy for each mission type will drive the 

amount of testing that is required, and hence, the arc jet capacity requirements for the Agency.

Table 3.1. Parameters

[Constructed with data from Munk, Future Missions;

Venkatapathy et al., Outer Planet Missions]

Characteristics LEO Return Mars entry Earth return 

from beyond 

LEO (comet)

Exploration 

of gas giants 

(Saturn)

Titan

Pressure 85 kPa 25 kPa 170 kPa 300 kPa 10 kPa

Heat Flux

 Convective 400 W/cm2 500 W/cm2 3000 W/cm2 4500 W/cm2 60 W/cm2

 Radiative N/A 100 W/cm2 7500 W/cm2 100 W/cm2 40 W/cm2

Shear 200 Pa 250 Pa 500 Pa 100 Pa

Flow State

 Turbulent Nice to have Yes Yes Nice to have Nice to 

have

 Laminar Yes Yes Yes Yes Yes

Enthalpy 25MJ/kg 30MJ/kg 100 MJ/kg 15MJ/kg

Gas 

Constituents

Air CO2 Air H2/He N2/CH4

Model Size 50 cm Large enough 

to test system 

features and 

closeouts

Large enough 

to test system 

features and 

closeouts

10 cm 10 cm

3.1 Return from Low Earth Orbit

Capabilities of existing NASA arc jet facilities are well matched to LEO return mission 

requirements. Figure 3.1 shows that typical trajectories for lifting bodies entering the atmosphere 

at about 7 km/s lie well within the range of conditions that can be simulated in these facilities. 

Existing facilities have also been used throughout the life cycle of crew transportation vehicles, 

and are still used for real-time support of each Shuttle mission (testing was conducted in support 

of STS 117 and 118 to guide decision makers on the need for TPS repair prior to re-entry).

The amount of testing that will be required for LEO return is highly uncertain, because human 

rating requirements (HRR) for commercial crew transport and cargo are not well-defined. The 

2009 report from the NASA Aerospace Safety Advisory Panel (ASAP) states:

“It is the Panel’s position that no COTS manufacturer is currently HRR qualified, 

despite some claims and beliefs to the contrary. Questions that must be answered 
Evaluation of Arc Jet Facilities Report

20

are: What is the process for certifying that potential COTS vehicles are airworthy 

and capable of carrying astronauts into space safely? How is compliance assured 

over the life of the activity? The same questions would apply to any potential 

international orbital transportation systems.”

In response to the Panel’s report, NASA agreed “to perform additional research to support 

development of the HRR implementation handbook.”2

If the HRR practice from previous programs is applied for commercial crew vehicles, the amount

of testing will be significant and will continue through the operational phase of the life cycle.

NASA Administrator Bolden suggests that NASA will “support ... the commercial spaceflight 

industry to enable hundreds, even thousands of people to visit or live in LEO.”3 Certainly, arc jet 

test capability will be required for such operations. Certification guidelines must be established 

before the required test capacity can be accurately predicted.

Figure 3.1. Existing arc jets provide adequate capability for LEO return vehicles

[Smith, AEDC Arc Jet Facility Capabilities]

In addition to NASA mission needs, the Air Force Research Laboratory (AFRL) has identified 

an ongoing need for testing in NASA facilities [Bowman, Arc Jet Testing Perspective]. In recent 

years, they have had 3 or 4 weeks at ARC for tests of hypersonic glide and cruise vehicles. 

Although these are not strictly orbital entry vehicles, they operate in an altitude and velocity 

regime that is better matched to NASA arc jet test capabilities than to the high pressure facilities 

at AEDC. AFRL anticipates a similar need in the next decade, with the possibility of moderate 

increases.

 

2 HRR Handbook described in NASA’s response to ASAP recommendation 2008-04-03. 3 Bolden comments on budget proposal for 2011.
Evaluation of Arc Jet Facilities Report

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3.2 Mars Entry

Entry velocity at Mars is relatively modest, with a maximum of 7.5 km/s for a direct trajectory. 

The challenge is to decelerate sufficiently quickly in the thin Martian atmosphere, which is about 

1% of the density of Earth’s atmosphere, to permit parachute deployment at a safe altitude for 

terminal descent. In order to generate adequate drag during hypersonic entry, a rigid aeroshell

must have a large cone angle which has the adverse effect of increasing the heating rate and 

turbulent shear stress on the leeward sections of the heat shield.

There have been six successful U.S. landings on Mars, beginning in 1976 with the successful 

deployment of Viking 1 and 2. The Viking mission, and the EDL technology developed for it, 

established the backbone for all U.S. Mars missions to date. All U.S. Mars missions have utilized 

a spherically blunted 70-degree half-angle cone for the forebody and Super Lightweight Ablator 

(SLA)-561V ablator as the heat shield material. The SLA-561V material has had extensive arc 

jet testing that, together with the experience gained from successful flights, has qualified it for 

flight in the thin carbon dioxide atmosphere of Mars.

The Mars Science Laboratory (MSL) mission, currently planned to land in 2012, is the largest 

and heaviest vehicle yet designed for Mars entry. The mission also has the highest entry velocity 

of 7.5 km/s, and requires a large-diameter aeroshell for drag. The combination of high-entry 

velocity, large-diameter aeroshell, and lift ratio is expected to produce conditions where, for the 

first time, a Mars entry capsule had to be designed for a completely turbulent heat pulse with 

significant levels of shear stress. Arc jet tests conducted on SLA-561V to assess its capability to 

sustain conditions predicted for MSL revealed a critical failure mode in which the protective 

surface layer is swept away by shear loads. Arc jet testing was essential for characterizing this 

material limitation and additional thickness would not margin against failure. Although SLA561V had been used successfully on several apparently similar previous missions, its limitation 

under turbulent shear required a material change from SLA-561 to the Phenolic Impregnated 

Carbon Ablator (PICA) material for the MSL mission. The change in thermal protection material 

required significantly more arc jet tests to qualify a new ablator material for Mars, including 

additional tests to examine the effects of the CO2 atmosphere on ablation rates

To date, no viable Mars EDL architecture has been put forward that can safely place more than 2 

metric tons at the higher surface elevations in close proximity to scientifically interesting terrain. 

The development of new EDL systems and technologies must begin before human-scale 

missions to the surface of Mars can be seriously considered. The Entry Descent Landing Systems 

Analysis (EDL-SA) group recently completed a study to define architecture requirements for 

delivering 40 metric tons, as will be needed for a crewed Mars mission. The study concluded that 

both an aerocapture and subsequent entry stage will be required, and that two basic systems, a 

mid lift-to-drag rigid aeroshell and a Hypersonic Inflatable Atmospheric Decelerator (HIAD), 

have the potential to land the required mass. 

A high lift-to-drag rigid aeroshell vehicle will have a higher ballistic coefficient than the 70-

degree sphere cone used to date. At the scale required to deliver large masses to the surface, 

predicted heating rates are close to 600 W/cm2

, with about 20% of the total heating being 

radiation from the shock layer. This heat rate is much higher than any previous experience at 

Mars and will require the development of new thermal protection materials and an 

aerothermodynamic database, for which a large number of arc jet tests will be required. In 

addition to the high heat pulse associated with aerocapture, thermal protection materials will also 
Evaluation of Arc Jet Facilities Report

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endure an extended cold soak while on orbit before the entry stage is commenced. Thermal 

protection concepts are proposed to handle the new requirement for dual heat pulse capability, 

and arc jet tests will be critically important for developing and qualifying those concepts with the 

required materials for an aerocapture application in the CO2 atmosphere of Mars.

Deployable decelerators for hypersonic entry are an emerging technology envisioned to provide 

very large drag area at high altitudes. Just before atmospheric entry, the HIAD is deployed with a 

flexible TPS cover. The EDL-SA study predicts peak heating rates could be as high as 115

W/cm2 during the aerocapture stage for a 23-meter diameter HIAD, including a predicted 

radiative heating level of 40 W/cm2. The current demonstrated capability for a suitable HAID 

flexible TPS is less than 30 W/cm2. Research development efforts funded under the NASA 

Fundamental Aeronautics Program are pursuing technologies that may extend performance 

capability to greater than 100 W/cm2, but arc jet testing support will be a critical assessment tool 

for capturing the effects of catalysis, chemistry, and flow dynamics. In an effort to reduce 

uncertainty, thermal performance within a CO2 environment should be completed to assess the 

effects of higher oxygen concentrations than Earth.

3.3 Earth Return from Beyond LEO

Entry into Earth’s atmosphere from beyond orbit involves velocities of 11 km/s or higher. 

Conversion of the kinetic energy—which is more than double that for entry from LEO at 7 

km/s—to heat involves much higher heating rates. For large, blunt vehicles, the radiative 

component from the detached shock wave is a significant fraction of the total heating. Figure 3.2

compares the heat flux and shear stress for Lunar Direct Return (LDR) and Mars Direct Return 

(MDR) with the levels required for LEO return [Reuther presentation of Hash]. Clearly the 

conditions to be simulated for entry from beyond LEO are far more severe. Also, since a large 

fraction of the heat flux is radiative, a suitable test facility must produce high levels of both 

radiative and convective heating to reduce performance uncertainties. Furthermore, radiation 

absorption by ablation products is an important component of the ablator response so that the 

radiative heat flux must have representative spectral distributions. Figure 3.3 indicates that 

enthalpy levels for Mars return are double the levels achievable in existing arc jets. Hence, 

significant advances in test facility design, beyond the capability of a LEAF-type facility, will be 

required.
Evaluation of Arc Jet Facilities Report

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Figure 3.2. Heat flux and shear levels for MDR, LDR and LEO return trajectories 

[Hash, Capabilities and Lunar Return Certification Requirements]

Figure 3.3. Enthalpy levels for MDR trajectory are double the capability of existing facilities

[Wright, Anticipated Arc Jet Usage]

Although the entry conditions for return from beyond LEO exceed the capabilities of existing 

facilities, it does not follow immediately that such missions cannot be undertaken by NASA 

without upgraded facilities. The Apollo program used multiple uncrewed flight tests of the fullscale flight vehicle to certify the heat shield for crewed operations. The Orion Project intended a 
Evaluation of Arc Jet Facilities Report

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combination of enhanced ground facilities, with the proposed LEAF complex, and flight test to 

certify the heat shield. The Galileo probe entered the Jovian atmosphere successfully, although 

the Giant Planet Facility, now defunct, did not generate total heating levels equivalent to those 

experienced in the mission. Nevertheless, serious consideration of Earth return missions will 

require significant arc jet capability augmentation, to provide combined convective-radiative 

heating at elevated heating rates.

Table 3.2. Representative Earth Entry Conditions for Various Missions

[Created using data from Munk, Future Missions]

Mission/Destination Entry 

Velocity, 

km/s 

Peak 

Convective 

Heating, 

W/cm2 

Peak 

Radiative 

Heating, 

W/cm2 

% 

Radiative 

Heating of 

Total 

Heating 

Peak 

Stagnation 

Pressure 

Estimate, Pa 

Peak Heating 

Stagnation 

Pressure 

Estimate, Pa 

Comet ~14-16 2000-3000 3000-

7500 

70% 30kPa300kPa 30kPa180kPa 

Asteroid ~11.5 1250 350 22% 4kPa150kPa 4kPa-95kPa 

Moon ~10-11 700-1000 50-150 15% 4kPa140kPa4kPa-85kPa

Mars (Science)

Mars (Human)

~11-12

~11-12

1300

3000

600

1400

30%

70%

170 kPa 100kPa

Stardust* 12.8 1200 130 10% 27kPa

Genesis* 11.0 700 30 4% 

3.4 Exploration of Venus and Outer Planets

Future exploration missions to Venus and the Outer Planets that require atmospheric entry will 

place a demanding challenge on the TPS to assure success, with the most demanding 

requirements being for the Gas Giants. Entry probes circumvent current limitations of remote 

sensing the inner depths of the atmosphere. To be successful, entry probes must be designed to 

tolerate the most demanding entry conditions for peak heat rate, total heat load, and dynamic 

pressure. Enabling future entry probe missions to the Gas Giants will require improvements in 

both aerothermodynamic modeling and TPS design. Due to extremely high entry velocities, giant 

planet probes require the most robust thermal protection materials.
Evaluation of Arc Jet Facilities Report

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The Galileo probe, which was launched with its orbiter in 1989 and entered the Jovian

atmosphere in December 1995, was exposed to what is regarded as the most extreme conditions 

for a TPS material to date. Almost half of the Galileo probe mass of 335 kg was dedicated to the 

heat shield (152 kg). The probe forebody was a 45-degree angle blunt cone configuration and 

entered the atmosphere at slightly more than 47 km/sec. In terms of recession tolerance under 

extreme heating rates and pressure, carbon phenolic, developed by the DOD for ballistic missile 

entry more than 40 years ago, is still considered to be the most robust ablator today. The 

combination of entry speed and dense Jovian atmosphere was estimated to yield a combined 

convective and radiative heating rate as high as 35,000 W/cm2

, and a significant portion of peak 

heating was due to radiant heating from the bow shock. As was predicted by CFD analyses, heat 

shield TPS performance flight data relayed from the Galileo probe to the orbiter demonstrated 

high recession rates, and more than half the mass of ablator heat shield was removed during the 

180-second heat pulse. Given the flight experience of Galileo, if the mission were done again, 

heat shield mass margins would probably grow, leaving less mass for science. 

Both the Galileo and Pioneer Venus probes used FM-5055 carbon phenolic for the heat shield 

material. If possible, it would be prudent to employ the same TPS material for future missions

that would encounter severe entry heating environments. Unfortunately, there is a very limited 

supply of the Avtex precursor rayon needed to make FM-5055 carbon phenolic. Since this 

material has a strong flight legacy with extensive support through ground-based arc jet tests, it is 

the only material capable of meeting the failure probability requirements for a Mars sample 

return to Earth. Unless alternative carbon phenolic materials for the legacy FM-5055 can be 

qualified for such severe environments, a Gas Giant probe mission will require development and 

qualification of a new TPS material. 

Following completion of the Galileo mission, the Giant Planets Facility at ARC used to qualify 

the FM-5055 material for flight was decommissioned. As a result, the United States does not 

currently have any arc jet test capability that can be used to simulate the entry conditions relevant 

to giant planet entry probes.

3.5 Exploration of Titan

Entry conditions at Titan are relatively benign. Entry velocity is only 6–6.5 km/s, with maximum 

heating rate of about 100 W/cm2 (up to 50% radiative) and stagnation pressures only about 0.1 

atmospheres. Existing arc jet facilities should be adequate for proposed missions to this 

destination. 

The Huygens probe, developed by the European Space Agency, used a tiled heat shield. It was 

tested in a plasma wind tunnel at the University of Stuttgart, both in a simulated Titan 

environment (77% N2, 20% Ar, 3% CH4) and in a pure nitrogen environment. After the mission 

was launched, new models for the atmosphere and adjustments to the planned trajectory 

indicated that heating could exceed the design levels, with a larger radiative contribution. NASA 

undertook a review of the heat shield, to determine whether the design was adequate and whether 

modifications to the entry trajectory might improve heat shield margins. Review activities 

included radiation testing, arc jet testing, and material response modeling. Ultimately, design 

adequacy was confirmed, but this was an example of the value of arc jet testing, even during 

mission operations.
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3.6 Material Technology Advancement

Flight projects typically select thermal protection materials that have a high Technical Readiness 

Level (TRL), and cannot afford to invest in material development. Mass-efficient TPS solutions 

are not available for many of the mission opportunities in the next 30 years and material 

technology development will be required. Current research projects are employing a functional 

design approach for materials development. Innovative materials concepts, which involve graded

densities, new polymer chemistries, and dispersed additives to improve insulation and radiation 

properties, are being considered. Since these concepts are new, arc jet testing will be essential for 

generating insight into material response across a range of mission-relevant environments. As 

material development proceeds to higher TRLs, advanced thermal protection technologies will 

reflect a clearer potential benefit as a vehicle subsystem.

Traditionally, low-TRL materials have been subjected to simple screening tests, in which 

developmental samples are exposed to flight-relevant environments with binary “pass-fail” 

performance criteria. More than 8000 arc jet tests were performed in the decade leading to 

Apollo flights, with a large percentage concentrated in the early development phase. It is 

estimated that modern simulation capabilities can help to reduce that total to around 2000, as 

shown in Figure 3.4, but flight-relevant testing will remain critical. 

Figure 3.4. Proposed testing requirements for qualification of an ablative TPS

[Wright, Anticipated Arc Jet Usage]

The efficient use of simple, less costly thermal tests combined with more scientific 

understanding can be used to screen candidates in this manner prior to arc jet testing. New arc jet 

facilities that provide more precise control and knowledge of the test conditions, and that have 

enhanced diagnostics to analyze gas species will increase the insight that can be derived from 

testing early in the development cycle. Instrumentation that records time-accurate surface 

behavior, recession rates, and species concentrations downstream of the test article are needed to 
Evaluation of Arc Jet Facilities Report

27

promote understanding of material response and more accurate prediction models. Deeper 

appreciation of functional performance and failure modes will define the potential of novel 

materials for mission applications.

In recent decades, new material development has competed for arc jet access with missioncritical subsystem development and sustaining engineering. Without the time-critical delivery 

requirements of the competing work, material development tests are commonly rescheduled, 

which complicates planning and milestone performance for these efforts. In a new complex, 

dedicated facilities should be made available for low-TRL material development activities.

3.6 Summary

Finding 3.1: Arc jet testing will be needed even for LEO return missions, for which materials 

already exist and operational experience is in hand. Existing test capability is adequate for this 

mission type. Capacity requirements to support LEO return are dependent on certification 

philosophy.

Finding 3.2: NASA and DOD share a mutual reliance on arc jet test capability. Air Force 

strategic planning relies on the availability of NASA arc jets for testing of hypersonic cruise 

vehicles. AEDC supports high-shear test conditions that are relevant to NASA.

Finding 3.3: Greater arc jet capability will be required for missions that NASA intends to fly 

within 30 years. Enthalpy, combined convective-radiative heating, test gas, shear, pressure, 

turbulence, and model size are among facility features to be addressed.

Finding 3.4: Arc jet facilities that provide more precise control and knowledge of the test 

conditions, and that have enhanced diagnostics to analyze gas species will benefit the maturation 

of low-TRL thermal protection concepts and materials technologies.

Finding 3.5: The available TPS choices for flight consideration are not optimal for many 

missions, and the TPS choices could be increased with improved accessibility and lower cost to 

use arc jets to develop low TRL concepts. 
Evaluation of Arc Jet Facilities Report

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4.0 Current Capabilities and Limitations

This section describes basic arc jet operation (Section 4.1) and then compares the performance 

capabilities of arc jet complexes that can support larger scale TPS development and certification. 

Additional description of the arc jet complexes can be found in Appendix F. Not evaluated here 

are small research and development arc jets and arc jet facilities that are not used for TPS 

material testing such as the arc facilities at the Langley Research Center, AHSTF, and HyMETS.

In addition, foreign (non-US) facilities were not considered as viable alternatives as a primary 

testing source for many reasons, including ITAR restrictions, control of access, control of 

schedule, and logistics.

Four arc jet complexes that can support TPS development and certification are:

1. Ames Research Center Arc Jet Complex

a. Interaction Heating Facility (IHF)

b. Aerodynamic Heating Facility (AHF)

c. Panel Test Facility (PTF) [includes the Truncated-PTF (TPTF)]

d. 2” x 9” Turbulent Flow Duct (TFD)

2. Johnson Space Center Atmospheric Re-entry Materials and Structures Evaluation Facility 

(ARMSEF)

a. Test Position 1 (TP-1)

b. Test Position 2 (TP-2)

3. Arnold Engineering Development Center Arc Jet Complex

a. High Enthalpy Ablation Test Unit H1 (HEAT-H1)

b. HEAT-H2

c. HEAT-H3

4. Boeing Large Core Arc Tunnel Arc Jet Facility (St. Louis)

Comparisons will be made for the various types of testing techniques in the individual arc jet 

facilities, specifically, free-jet stagnation testing, free-jet shear testing, and panel testing. For 

each of these three types of testing, comparisons will be shown for test model surface heat flux 

versus surface pressure. In addition, for stagnation testing, a comparison will be shown for 

centerline enthalpy versus pressure, and for shear testing, a comparison will be shown for heat 

flux versus shear force.

Although the vacuum system, high pressure gas system, and cooling water systems are important 

for determining the complex capability, the power supply size will typically limit the maximum 

capability of a facility in terms of flow-field size, enthalpy, heat flux, and run time. Therefore, 

only the power supply capabilities at the various complexes will be compared here.

All of the facility performance data and mission trajectories presented in the figures below were 

obtained from Howard, Summary of Current NASA Facility Maps; Venkatapathy, Capabilities 

Needed for Future Venus and Outer Planet Missions; Wright, Anticipated Arc Jet Usage; Raiche, 

NASA Ames Arc Jet Complex Overview; Kardell, Boeing LCAT Facility Capability; Smith, 

AEDC Arc Jet Facility Capabilities; Ares, Arc-Heated Test Facility Investment; Shepard and 

Carlson, Upgrading of NASA-Ames High-Energy Hypersonic Facilities; NASA SP-8014, Entry 

Thermal Protection.
Evaluation of Arc Jet Facilities Report

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4.1 Basic Arc jet Operation

Arc jets are one part of NASA’s hypersonic thermal testing capability and are used to provide 

critical data for the research and development of TPS materials and techniques; to qualify, 

certify, and validate the suitability of TPS materials and processes for flight; and to support TPS 

damage assessment and the verification of repair techniques. The basic operation of an arc jet, 

depicted in Figure 4.1, involves using a high-power electric arc to heat a test gas to very high 

temperature and then expanding and accelerating this heated test gas through a nozzle and onto a 

stationary test model or calibration probe located in a vacuum environment. This high-energy 

flow of ionized gases simulates the surface pressure, convective heating, and shear force 

conditions associated with hypersonic flight, and the vacuum environment allows the highaltitude conditions to be established and maintained.

Figure 4.1. Arc jet schematic 

[Raiche, ARC Overview]

Several systems are required for an arc jet, as shown in Figure 4.2. The test medium is air, a 

specialty gas, or a combination of gases, which require pressurized storage and delivery systems. 

A high-voltage, high-current electrical distribution system is necessary to generate the arc. The 

arc heater must be actively cooled to protect against the high-temperature conditions, and this is 

accomplished through a cooling water system. The vacuum in the test chamber is established and 

maintained through the use of a steam ejector system or mechanical pumps. The steam ejector 

system uses a boiler to generate the steam. Some facilities have pollution control systems which 

require capture and condensing of the exhaust products from the ejector system. The test article 
Evaluation of Arc Jet Facilities Report

30

is inserted into and retracted from the test stream through a model support system. All of these 

tunnel systems are operated through a facility control system. Test chamber conditions and 

model reactions are captured and processed through a data acquisition system that collects and 

stores the raw data and then reduces it to usable information.

Figure 4.2. Arc jet facility components 

[Raiche, ARC Overview]

4.2 Simulation Regime

The overall arc jet complex performance is shown in Figure 4.3 as a function of simulated 

altitude and velocity for stagnation-type testing. Several system entry trajectories are also shown 

on the plot for the Shuttle (similar to Crew Exploration Vehicle (CEV) and International Space 

Station (ISS) return), the Apollo (similar to CEV Lunar return), a Mars return, a far solar system 

probe return, and an Intercontinental Ballistic Missile (ICBM). In addition, the peak heating 

point for each mission trajectory is shown. Notice that the present facility envelopes do an 

adequate job of covering a LEO entry (Shuttle return) and almost capture the Apollo Lunar 

return peak heating point; however, they are inadequate for simulating the peak heating regions 

for Mars and far solar system returns. The present facilities are also inadequate for simulating 

other planet entry peak heating points, such as Saturn and Jupiter.
Evaluation of Arc Jet Facilities Report

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Figure 4.3. Comparison of NASA, AEDC, and Boeing arc jet facility 

performance with several nominal Earth return trajectories.

The ARC, JSC, and LCAT simulation envelopes are at the higher altitudes, which capture the 

major portion of the Shuttle and CEV trajectories, while the AEDC facilities are primarily in the 

lower altitude regime, suitable for DOD weapon trajectory simulation, and capture the maximum 

heating point of an ICBM entry. However, the AEDC H2 facility does have a region of interest 

for NASA missions: it captures a portion of the CEV (Apollo), Mars return, and far solar system 

return trajectories that are generally associated with higher pressure and shear conditions. 

Notice that the ARC facilities’ combined simulation envelope is larger and encompasses most of 

the JSC simulation envelope. Also notice that the LCAT facility has a significant overlap with 

the NASA facilities and the AEDC H2 facility. The AEDC H2 facility captures only a small 

portion of the simulation envelope that is relevant to NASA missions; therefore, most of the 

discussion in the following sections will focus primarily on comparing the capabilities of the 

three complexes that are of most interest: ARC, JSC, and Boeing LCAT. In addition, the H1 and 

H3 facilities at AEDC do not have any regime that is of interest to NASA missions, and these 

two facilities will not be considered further.

In the sections below, the performance capabilities of each complex will be compared for three 

different types of testing: stagnation, shear, and panel.

Stagnation-type testing generally uses a circular model with a flat face, rounded face (ISO-Q), or 

hemispherical shape. In addition, stagnation-type testing can be performed on special features 

0

10

20

30

40

50

60

70

80

90

0 2 4 6 8 10 12 14 16 18

Pressure Altitude (k m)

Simulated Velocity (km/sec)

Arc Jet Complex Envelopes and Nominal Earth Return Trajectories MarsReturn

Far Solar System Return

ICBM Entry AEDC

Complex

Ames

Complex

LCAT

Complex

JSC

Complex

= Max Heating
Evaluation of Arc Jet Facilities Report

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such as pressure ports in TPS, nose tips, or leading edges. The model is usually positioned in the 

free-jet downstream of the nozzle so that it experiences stagnation flow on the region of interest. 

Facilities that generally perform stagnation testing are TP-2, IHF, AHF, LCAT, and H2.

Shear testing generally uses wedge type models that are injected into the free-jet flow 

downstream of the nozzle exit. The test samples are usually flat material panels that can be fixed 

to the wedge surface. The wedge angle of the model holder is tailored to provide a specific 

heating rate, pressure, and shear force on the test sample surface. Facilities that generally 

perform shear testing are the same as the facilities that perform stagnation-type testing: TP-2, 

IHF, AHF, LCAT, and H2.

Panel testing generally involves larger models than either stagnation or shear testing and 

generally involves testing of special features in the TPS, such as gaps or seams between TPS 

blocks or tiles or protuberances on the external mold line. There are two basic types of panel test 

facilities. One type uses a channel flow where the test article makes up one wall of the channel. It 

is usually difficult or impossible to have visual access to the sample during the test in a channeltype facility. In addition, the test sample has to be relatively flat to conform to the channel 

profile; therefore, these facilities are not generally used to test outer mold line protuberances. 

Facilities that perform panel testing using a channel flow are TP-1 and the TFD.

The second type of panel testing facility generally uses a semi-elliptic nozzle to expand the flow 

as wide as possible to cover a larger test surface, and so the nozzle has a flat lower surface. The 

test article is attached to the lower, flat surface at the exit of the semi-elliptic nozzle and can be 

pitched into the flow. This type of panel facility has good optical access during the test, can test 

protuberance-type of features, and can change pitch, even during the run to provide a larger 

range of test conditions. Facilities that perform this type of testing are the PTF and IHF.

4.3 Stagnation Testing

Stagnation performance testing envelopes are shown in Figure 4.4 for a 10-cm (~4-in.) 

hemisphere for the IHF, AHF, TP-2, and LCAT in terms of cold wall heat flux on the model 

surface and model surface wall pressure (stagnation pressure). Note that a 10-cm hemisphere size 

is used only as a comparison between facilities. One of the LCAT nozzles can only support a 

8.9-cm (3.5-in.) diameter model; and therefore, a portion of the LCAT envelope, shown in

Figure 4.4, cannot support a model as large as 10 cm. Figure 4.5 shows stagnation performance 

in terms of centerline enthalpy and model wall pressure. Similar to the overall comparison 

envelopes shown in Figure 4.3, the ARC facilities, IHF and AHF, encompass most of the JSC 

TP-2 performance envelope and a significant portion of the LCAT envelope. Two trajectories are 

shown in the two figures below for reference: a Shuttle return (ISS return) and an Apollo return 

(Lunar return). In addition, the peak heating conditions are also shown in Figure 4.4 for a Saturn 

aerocapture and Saturn hyperbolic Entry. Present arc jet facilities are inadequate for simulating 

Saturn and other Gas Giant entries.

In general, the NASA facilities and the AEDC facility can test larger models than the Boeing 

facility because they have a family of larger nozzles. However, flow-field size for a given 

condition is determined by arc heater power. Therefore, if the power delivered to the test gas is 

higher, the flow field can be expanded to a larger size for a specific test condition, assuming 

larger nozzles are available.
Evaluation of Arc Jet Facilities Report

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Figure 4.4. Stagnation point heat flux vs. stagnation pressure for a 10-cm hemisphere

1

10

100

1000

10000

0.1 1 10 100 1000

Cold Wall Heat Flux (W/cm2)

10cm Hemisphere

Wall Pressure (kPa)

C.W. Stagnation Point Heat Flux vs. Stagnation Pressure

IHF

AHF

TP-2, 10-Pack

TP-2, 5-Pack

LCAT

Saturn Hyper

Saturn Aero

Shuttle Return

Apollo Return

TP-2, 10-Pack

LCAT

IHF

AHF

TP-2, 5-Pack

Saturn

Hyperbolic

Entry

Saturn

Aerocapture
Evaluation of Arc Jet Facilities Report

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Figure 4.5. Stagnation facility comparison, 

centerline enthalpy vs. wall pressure for 10-cm hemisphere.

4.4 Shear Testing

Free-jet shear testing is primarily performed using a wedge model. The wedge angle can be 

varied to acquire the desired heat flux, pressure, and shear on the test article. Figure 4.6 and 

Figure 4.7 show comparisons of shear testing among various facilities. Notice that the NASA 

and Boeing facilities have a considerable overlap, while the AEDC facility can obtain higher 

pressures and shear forces typically required for weapons systems testing. The TP-2 facility is 

not shown in these figures, but is expected to have an envelope slightly smaller than the IHF 

facility.

Free-jet shear testing differs from panel testing in the area of test conditions and sample sizes. 

The test conditions, pressure, heat flux, and shear are higher for free-jet shear testing than for 

panel-type facilities; however, the sample sizes are typically smaller. Notice that the sample sizes 

shown in figures 4.6 and 4.7 are on the order of 4 inches by 4 inches where panel samples are 

much larger. The TPTF, although technically a panel test facility, is included with the shear test 

facility envelopes in the figures below, because it has sample sizes and test conditions 

comparable to the free-jet facilities.

1

10

100

0.1 1 10 100 1000

Centerline Enthalpy (MJ/kg)

Wall Pressure (kPa)

Centerline Enthalpy vs. Stagnation Pressure

IHF

AHF

TP-2, 10-Pack

TP-2, 5-Pack

LCAT

LEO Return Lifting

Lunar Return

IHF

AHF

LCAT

TP-2, 10-Pack

TP-2, 5-Pack

Shuttle Return

Apollo Return
Evaluation of Arc Jet Facilities Report

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Figure 4.6. Shear test facility comparison, cold wall heat flux vs. wall pressure

0

100

200

300

400

500

600

0 10 20 30 40 50 60 70 80 90 100

Cold Wall Heat Flux (W/cm2)

Wall Pressure (kPa)

Shear Test Facilities - Heat Flux vs. Wall Pressure

IHF 4-in x 4-in

TPTF 4-in x 4-in

LCAT 4.5-in x 5-in

LCAT 3-in x 3-in

H2 4-in x 4-in

H2, 4-in x 4-in

IHF, 4-in x 4-in

LCAT, 3-in x 3-in

LCAT, 

4.5-in x 5-in

TPTF, 4-in x 4-in
Evaluation of Arc Jet Facilities Report

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Figure 4.7. Shear test facility comparison, cold wall heat flux vs. shear force.

Figure 4.8 shows the shear test performance for the facilities shown in the figures above 

compared with three trajectories: ISS direct return, Lunar direct return, and Mars direct return. 

All three of these are ballistic trajectories with full margins applied. Notice that the facilities 

adequately cover an ISS return, but are not adequate for simulating a Lunar or Mars return.

The MSL test program used arc jet facilities at JSC, ARC, AEDC, and Boeing to perform shear 

testing. None of the facilities could adequately match all of the required testing regimes of 

interest; however, among all of the facilities, a sufficient coverage of the conditions was 

accomplished to evaluate the TPS under appropriate shearing conditions.

0

50

100

150

200

250

300

350

400

450

500

0 100 200 300 400 500 600 700 800 900

Cold Wall Heat Flux (W/cm2)

Shear Force (Pa)

Shear Test Facilities - Heat Flux vs. Shear Force

IHF 4-in x 4-in

TPTF 4-in x 4-in

LCAT 4.5-in x 5-in

LCAT 3-in x 3-in

H2 4-in x 4-in

H2, 4-in x 4-in

IHF, 4-in x 4-in

LCAT, 3-in x 3-in

LCAT, 4.5-in x 5-in

TPTF, 4-in x 4-in
Evaluation of Arc Jet Facilities Report

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Figure 4.8. Shear test facility capability compared with several ballistic trajectories 

(trajectories shown with full margins).

4.5 Panel Testing

Four facilities in NASA are specifically configured for panel testing. They are the JSC TP-1 and 

ARC TFD, which are both channel flow facilities, and the IHF and PTF, which are configured 

with semi-elliptic nozzles and test plates, which can be pitched into the flow. Figure 4.9 and 

Figure 4.10 show the performance capability of the four facilities in terms of heat flux versus 

pressure. Figure 4.10 is the same as Figure 4.9 with the addition of the TFD. Not shown is the 

new 4-inch by 4-inch test capability in the TP-1 facility, which should have higher heat flux and 

pressure similar to the TPTF shown in figures 4.6 and 4.7.

0

500

1000

1500

2000

2500

0 100 200 300 400 500 600 700 800 900

Cold Wall Heat Flux (W/cm2)

Shear Force (Pa)

Shear Test Facilities - Heat Flux vs. Shear Force

IHF 4-in x 4-in

TPTF 4-in x 4-in

LCAT 4.5-in x 5-in

LCAT 3-in x 3-in

H2 4-in x 4-in

ISS Return

Lunar Return

Mars Return

H2, 4-in x 4-in

IHF, 4-in x 4-in

LCAT, 3-in x 3-in

LCAT, 4.5-in x 5-in

TPTF, 4-in x 4-in

ISS Return
Evaluation of Arc Jet Facilities Report

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Figure 4.9. Panel test capability showing heat flux vs. pressure.

0

10

20

30

40

50

60

70

80

0 1 2 3 4 5 6

Cold Wall Heat Flux (W/cm2)

Wall Pressure (kPa)

Panel Test Facilities - Heat Flux vs. Wall Pressure

IHF 24-in x 24-in

PTF 14-in x 14-in

TP-1 12-in x 12-in

TP-1 24-in x 24-in

IHF, 24-in x 24-in

TP-1 12-in x 12-in

PTF, 14-in x 14-in

TP-1 24-in x 24-in
Evaluation of Arc Jet Facilities Report

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Figure 4.10. Panel test capability showing heat flux vs. pressure with addition of the TFD.

4.6 Power Supply

The larger of the two power supplies at ARC, which is rated at 60 MW continuous operation, can 

also operate at 75 MW for 30 minutes and 150 MW for 15 seconds. However, the power supply 

is presently operating under reduced capacity because of a fire which destroyed one of the six 

rectifier modules. This reduction in capability does not affect performance of the IHF facility, as 

it runs at power levels below the maximum capability. The JSC power supply is rated at 10 MW 

continuous operation and can operate at 12 MW for 15 minutes. The AEDC power supply is 

rated at 60 MW continuous operation and has operated at 77 MW for approximately one minute. 

The LCAT facility has a 12 MW power supply.

The ARC and AEDC power supplies are both 60 MW continuous output-rated power supplies; 

however, the ARC power supply is configured to operate at higher current and lower voltage 

(which is suitable for low pressure flow environments), while the AEDC power supply operates 

at higher voltage and lower current (which are suitable for high pressure operations). The 

different configurations of the ARC and the AEDC power supplies is significant if consideration 

is given in the future for installing a new arc heater capability at AEDC to operate in the range of 

interest for NASA missions. The AEDC power supply cannot be reconfigured to operate at low 

pressure conditions (high current and lower voltage) and, therefore, a new power supply would

need to be procured if a NASA-type heater were to be operated at AEDC. The JSC and LCAT 

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25

Cold Wall Heat Flux (W/cm2)

Wall Pressure (kPa)

Panel Test Facilities - Heat Flux vs. Wall Pressure

IHF 24-in x 24-in

PTF 14-in x 14-in

TP-1 12-in x 12-in

TP-1 24-in x 24-in

TFD 2-in x 9-in

IHF, 24-in x 24-in TP-1 12-in x 12-in

PTF, 14-in x 14-in

TP-1 24-in x 24-in

TFD 2-in x 9-in
Evaluation of Arc Jet Facilities Report

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facilities are both much lower in power output. This will be a consideration if upgrading an 

existing facility or installing a new facility in an existing complex is considered.

4.7 Summary

Finding 4.1: The simulation regimes of the present facilities are sufficient for simulating low 

Earth orbit entries and certain regimes for Lunar return. However, these facilities are inadequate 

to fully evaluate the TPS for a Mars or deep space Earth return or certain planet entries such as 

the Gas Giants.

Finding 4.2: Existing NASA facilities have capability in terms of model size and performance 

that is not duplicated by DOD or commercial facilities.

Finding 4.3: An inspection of the performance envelopes shows that the JSC capability is 

basically a subset of the ARC combined capability.

Finding 4.4: Incremental improvements in arc heaters will not deliver the higher test capability 

needed for more ambitious NASA exploration missions to Gas Giants and human return from 

Mars.

Finding 4.5: The AEDC power supply cannot operate at low voltage and high current, which is 

required to power a NASA-type arc heater which operates at low pressure. Therefore, if AEDC 

is considered as a potential site for operating NASA-type arc heaters, a new power supply will 

need to be procured.

Conclusion 4.1: NASA must bear the responsibility of designing and developing facilities with 

improved capability in order to successfully support future NASA missions.

Conclusion 4.2: A focused technology development effort is required to establish the arc jet 

testing capability required by NASA for future missions.
Evaluation of Arc Jet Facilities Report

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5.0 Arc Jet Capacity

Section 5.1, Workforce, compares the workforces at ARC, JSC, and AEDC arc jet complexes. 

Section 5.2, Throughput, evaluates the operations at the ARC, JSC, AEDC, and LCAT facilities, 

the throughput, the customer base, and types of testing performed by these customers. The 

proposed LEAF facility is considered in the context of capability gaps for mission requirements 

in Section 5.2. Section 5.3 considers the condition of the arc jet infrastructure. Section 5.4 

evaluates mothballing existing facilities. Section 5.5 identifies options for increasing throughput.

5.1 Workforce

Arc jet facilities require a workforce with unique skills and qualifications. Both the ARC and 

JSC arc jet test facilities use segmented arc heaters, which are considered to be state of the art. 

The operation and maintenance of segmented arc heaters at both facilities is complex and 

requires a staff with special knowledge and skills. Detailed attention must be given to the

assembly of the segments, insulators, tie rods, water, and air hoses to insure safe and reliable

operation. The high pressure air and cooling water supply systems are relatively standard at both 

facilities, but the water must be de-ionized to reduce electrical conductivity and scaling within 

the heater. 

Arc jet power supplies operate at very high AC voltages and currents that must be rectified to 

provide necessary DC current and that require special current controls to maintain stable arc 

operation. A reliable operation of high power electrical systems requires special attention to

maintenance, repair, test, and safety procedures. 

Both the ARC and JSC arc jet facilities operate with dedicated boiler and steam systems to 

generate the vacuum pressures needed for simulating entry conditions. The steam vacuum 

systems for arc jet facilities must be well maintained to ensure safe and efficient operation. These 

facilities also produce gas flows with extremely high temperatures and heat transfer rates, which 

require special knowledge of handling hot gas flow to prevent facility damage. Unique hightemperature instrumentation is necessary for test model measurements, and this includes nonintrusive instrumentation often needed to characterize the flow field.

Arc jet operation personnel must be knowledgeable about the special procedures and precautions 

required to ensure both personnel and plant safety. Safe operation of these systems and 

subsystems requires a staff with special qualifications and training. Extensive training and 

experience is necessary to be qualified for performing required tasks. The special skills and 

knowledge required have been gained through years of operational experience, teaming, and 

continuity of training. Continuity for training new facility personnel is necessary for successful 

operation.

Simply relocating existing personnel is not always possible, and the availability of workforce 

should be considered when choosing a site for a new construction facility. 

While a workforce with special skills is necessary, the staff need not be large. Both ARC and 

JSC have the appearance of excess staffing at both facilities. Since operational infrastructure 

support systems (power, steam, coolant water, and gas supply) are common to all test units, an 

operating crew of 15 to 20 people should be sufficient staffing for a single shift operation. The 

primary responsibility of this test operations crew is to support the day-to-day test programs in 

the arc jet facility.
Evaluation of Arc Jet Facilities Report

42

Other activities associated with an arc jet facility, but which are not part of the daily operations, 

would include arc jet technology and development, hardware design, fabrication services, plant 

maintenance and repairs, minor facility modifications, procurement, safety, configuration 

management, and quality assurance. The personnel who perform these tasks may or may not be 

dedicated to the arc jet facility. Preferably, some of the more closely related activities such as arc 

technology and facility design would be staffed by full-time dedicated personnel. Other arc jet 

facility support of a less technical nature may be accomplished by personnel who also support 

other Center test facilities. The cost of these services may be shared, thus reducing the overall 

budget required for these services. 

The ARC arc jet staff is composed of 20 test operations personnel for day-to-day activities, 

which include model preparation, arc heater and test cell readiness, pre-operational set up, test, 

and post-operational efforts. Of these 20 people, 5 are civil service employees and 15 are 

contractor employees. This level of staffing is reasonable for a single-shift operation. There are 

33 personnel providing operational support. This support includes engineering (design, drafting, 

documentation, project support, and quality assurance), maintenance and repair (plant 

maintenance and fabrication services), and administrative services (safety, configuration 

management, procurement, and contract support). Resources could be saved by allowing 

administrative and maintenance personnel to share their time with other Center facilities. This 

would allow these personnel to charge to arc jet facility projects only when they are provide 

direct support. At other times, these personnel would be available for other Center tasks and 

should charge to these tasks. An independent review of the entire arc jet operation can reduce 

staffing levels by up to 30%.

The JSC staff has 3 civil service employees and 33 contractor employees in a two-shift 

operation. The contractor staff is evenly divided between engineers and technicians. The JSC arc 

jet facility is presently booked full time with Space Shuttle testing. Once the Shuttle tests have 

ended, the JSC arc jet facility should return to a single-shift operation. This would allow the 

contractor staff to be reduced by about one-third [Madden, JSC Arc Jet].

The operations workforce at AEDC consists of 20 personnel plus 2 engineers supporting the arc 

facility technology development projects. In addition, high-pressure air and the mechanical 

vacuum source are provided through AEDC’s central base support.

5.2 Throughput

5.2.1 Ames Research Center

The ARC arc jet complex comprises four tunnels: the 20 MW AHF, the 60 MW IHF, the 20 MW

PTF, and the 12 MW TFD. The ARC arc jet complex has a staff of 53; and for workforce 

planning, uses a single-shift operation 40 weeks per year, or 160 available calendar days. 

Multiple facilities can operate on the same calendar day, which gives the facility manager 

flexibility in scheduling and accomplishing revenue-generating Occupancy Days (OD). ARC 

targets 220 ODs per year for operations and 2 facility runs per OD. Thus, a single calendar day 

can generate more than one OD, and approximately 50% of the operational days for the AHF and 

IHF yield two or more runs per day.

Test operations are conducted Monday through Thursday for nine hours each day. The first 

Friday of the two-week schedule is reserved for maintenance, and the second Friday is utilized 
Evaluation of Arc Jet Facilities Report

43

for alternative work schedules. For high-occupancy periods, extended shifts and weekend 

maintenance are used. 

For the last five fiscal years, ARC’s throughput was as shown in Table 5.1.

Table 5.1. Throughput for ARC Arc Jet Complex

[Raiche, ARC Overview]

Data for test models, calibration probes, and Occupancy Days (OD) is tabulated per fiscal year (FY)

The table captures the variability in annual hypersonic thermal testing requirements. The AHF 

and IHF are the most utilized of the four facilities, and these two facilities are approximately 

equally active and account for over 90% of the test models and calibration probes through the 

five-year period. Approximately 40% of the testing is for models and 60% is for calibration 

probes. The number of calibration probes was unusually high during this period because of the 

Orion Project’s need to establish new operating conditions in the facility. To provide a look at 

recent users, FY08 and FY09 utilization was approximately 80% NASA (4% Aeronautics 

Research Mission Directorate (ARMD); 6% Space Operations Mission Directorate (SOMD); 

20% Science Mission Directorate (SMD); and 50% Exploration Sciences Mission Directorate 

(ESMD)); 12% other U.S. Government; and 6% from the commercial sector. This distribution is 

graphically represented in Figure 5.1.

Figure 5.1. ARC arc jet complex customer base

Not captured in Figure 5.1 is the significant increase in the commercial sector percentage from 

FY08 to FY09.

Test Calibration Charged Actual

Year Models Probes OD OD Models Probes Models Probes Models Probes Models Probes

FY05 555 460 175 215 220 289 335 170 0 1 0 0

FY06 292 434 135 205 43 144 219 261 26 23 4 6

FY07 404 748 218 265 209 445 125 223 68 25 2 55

FY08 423 786 171 242 223 437 194 332 0 9 6 8

FY09 404 435 143 206 139 214 171 197 94 24 0 0

Totals 2078 2863 842 1133 834 1529 1044 1183 188 82 12 69

Averages 416 573 168 227 167 306 209 237 38 16 2 14

AHF IHF PTF TFD

Commercial

Other US Government

NASA ARMD

NASA SOMD

NASA SMD

NASA ESMD
Evaluation of Arc Jet Facilities Report

44

5.2.2 Johnson Space Center

The ARMSEF comprises the channel nozzle TP-1 and the conical nozzle TP-2; both are 10 MW 

facilities. The ARMSEF has a staff of 36 personnel working two shifts, 5 days a work week. The 

staff operates both the ARMSEF and the separate Radiant Heat Transfer Facility (RHTF). The 

simultaneous operation of TP-1 and TP-2 is not possible because of electrical power and 

workforce constraints. It is possible to operate either TP-1 or TP-2 and RHTF at the same time, 

though, but this is not done due to workforce constraints.

For the last four calendar years, JSC’s throughput was as shown in Table 5.2:

Table 5.2. Throughput for JSC Arc Jet Complex

[Del Papa, ARMSEF and Madden, JSC]

Data for test models and calibration probes is tabulated per calendar year

The TP-2 is used more than TP-1 and accounts for 85% of the models and probes tested through 

the four-year period. This is due to the prime customer being the Shuttle Program, and panel 

testing of tiles has been more critical than stagnation testing to Shuttle-related activities. 

Approximately 65% of the testing is for models and 35% is for calibration probes. The ARMSEF 

is overwhelmingly dedicated to the Shuttle and Constellation Programs.

5.2.3 Air Force Arnold Engineering Development Center 

The arc jet complex at AEDC comprises three tunnels: the 30- MW H1 segmented arc heater, the 

42 MW H2 arc-heated wind tunnel, and the 70 MW H3 arc heater. 

The AEDC complex has a staff of 20 plus additional personnel for support systems. Test 

operations are conducted through a single shift, 40 hours per week, and 50 weeks per year. 

AEDC utilizes overtime as needed to maintain schedule, and annual overtime requirements do 

not exceed 10-15% of the standard shift work hours. AEDC accomplishes 60-90 runs in a typical 

year, which equates to 300-400 test articles per year (each run involves 4-7 test articles). Eighty 

percent of the runs are test articles and 20% are calibration probes. Approximately 80% of the 

runs are for reimbursable customer runs, 15% are for technology development, and 5% are for 

facility checkout and validation. The arc jet complex at AEDC supports the Air Force, Army, 

Navy, the Defense Advanced Research Projects Agency (DARPA), the Missile Defense Agency, 

and NASA (SMD and ESMD).

Test Calibration

Year Tests Models Probes Models Probes Models Probes

2006 229 143 86 35 11 108 75

2007 158 94 64 29 5 65 59

2008 192 141 51 19 5 123 46

2009 187 128 59 8 8 120 51

Totals 766 506 260 91 29 416 231

Averages 192 127 65 23 7 104 58

TP-1 TP-2
Evaluation of Arc Jet Facilities Report

45

5.2.4 Boeing Large Core Arc Tunnel

The 5 MW Boeing LCAT is a limited-operations facility with a test staff of four, plus additional 

personnel who provide maintenance and operational support. The arc jet facility is available 

during normal working hours. The number of tests Boeing accomplishes each year is a highly 

variable number ranging from 50 to 1000, and approximately 65% of the testing is for models 

and 35% is for calibration probes. The facility occupancy is cyclical, but typically ranges from

about 25% to 100% with an average availability of about 50%. When not engaged with arc jet 

testing, the facility staff supports other projects. Boeing projects account for 20-30% of the 

facility occupancy. The facility also supports NASA, the Air Force Research Lab, and small 

business innovation research contractors.

5.2.5 Testing Costs

Comparing costs and throughput provides insight into the cost of testing at the ARC, JSC, 

AEDC, and LCAT facilities. Table 5.3 [deleted from public version of report] contains 

information on annual operations and maintenance costs and average throughput used to 

calculate an average cost per test at these four complexes. This cost is not what a customer will 

pay; rather, it is the average cost the combined funders (the owning organization, any 

subsidizers, and all customers) pay per test. To provide a more consistent comparison with ARC 

and JSC, the “Annual Cost” and “Associated Personnel” numbers for AEDC and LCAT are 

adjusted to capture the additional personnel that provide engineering, maintenance, and 

operational support. It is not surprising that the average cost per test at the Boeing LCAT is 

lower than at the Government facilities. Worth noting is the value used for the number of tests 

(200) at LCAT is conservative, based on Boeing's description of the tests varying from 50 

(described as “very lean”) to 1000 (“busy”). If a higher number for tests were used, it would 

decrease the cost per test at LCAT. 

5.2.6 Lunar Environment Arc Jet Facility 

The Orion Project team undertook the TPS Advanced Development Project Analysis of

Alternatives (AoA) Study to determine the most cost-effective means to meet the CEV heat 

shield certification needs. Their solution was the Lunar Environment Arc Jet Facility (LEAF)

Project, a new arc heater with radiant lamp augmentation added to the NASA Ames arc jet 

complex.

To certify the heat shield for lunar direct return entry velocity, a ground test program must 

demonstrate the TPS material and system performance and validate thermal response models 

across a range of flight-like aerothermal conditions. General CEV Lunar return certification 

needs include 300 W/cm2 radiant heating capability combined with 400 W/cm2 of convective 

heating, shear test capability at heat flux levels greater than 350 W/cm2, turbulent heating 

capability, and relevant system responses from panel and integrated system test articles for 

features on the order of 30 cm. 

The LEAF Project was established to develop a combined electric arc jet-heated blow down

wind tunnel and radiant heating system capable of simulating much of the aerothermal 

environment that Orion would experience during returns into the Earth’s atmosphere. The 

general requirements were high radiant and convective heating rates over large stagnation and 

panel test specimens and combined high heating, high shear, high enthalpy, and low pressure 

environments. The design included a 75 MW segmented arc heater with conical and semielliptical nozzles for stagnation and wedge testing, an independent radiant light source for 
Evaluation of Arc Jet Facilities Report

46

coupled convective-radiant heating, and installation in a vacant test bay connected to the existing 

power, vacuum, air, and water infrastructure to minimize initial costs.

LEAF is a technical capability enhancement funded by the Constellation Program with technical 

requirements determined by and specific to the Orion Project. In the opinion of the AJEWG, the 

LEAF Project raises two important issues for the Agency. The project analysis indicated that an 

arc jet capability greater than that which currently exists is needed to meet the requirements of 

the CEV. And the LEAF Project also illustrates a piecemeal approach to meeting program 

requirements that does not serve the Agency. Programs are empowered to construct capability 

without regard to total facility life cycle support, cost, and the impact of that capability on the 

institution. The narrow focus on Orion requirements for the LEAF facility also allowed no cost 

latitude for enhancements that could address requirements from other missions. The Preliminary 

Design Review (PDR) was held in September 2009, the Critical Design Review (CDR) is 

scheduled for June 2012, and LEAF is scheduled to be operational in October 2015. 

5.3 Infrastructure Condition

The condition of the equipment and infrastructure that comprise and support the ARC arc jet 

complex and the JSC ARMSEF is typical of research systems that were installed in the 1960s 

and 1970s and have experienced uneven maintenance and recapitalization funding. It is a mix of 

new, old but maintained, and end-of-life equipment with data acquisition and facility automated 

control systems ranging between state of the art and (not so recently) obsolete. As will be seen, 

several systems and components in the ARC and JSC complexes are at or beyond their nominal

service life. But this is typical for Government technical facilities; these systems and components 

are not considered to be in critical condition. The revitalization plans proposed are justified by 

reliability improvements and meeting expected regulatory constraints and are not by risks to 

basic operation. It should be noted that there is no commercial supplier base for integrated arc jet

service solutions, and that arc jet requirements are unique, they involve high energy, and the 

tolerance for mistakes is low. 

5.3.1 Ames Research Center

The deferred maintenance for the arc jet complex is ~$67 million, and the overall health and 

estimated life expectancy of the ARC arc jet complex is shown in Table 5.4.
Evaluation of Arc Jet Facilities Report

47

Table 5.4. ARC Arc Jet Complex Subsystem Summary

[Raiche, ARC Overview]

Several systems and components in the table are near or at their nominal service life. This is 

typical for Government technical facilities; these systems and components are not considered to 

be in critical condition. This analysis was endorsed by ARC in the March 18, 2010, presentation 

to the AJEWG. 

ARC tracks unplanned downtime, and this measure can provide a basis from which facility 

condition can be inferred. In FY08, ARC experienced 684 hours of unplanned downtime in the 

AHF and IHF, which translated into an availability of 85% and 82%, respectively. For the first 

quarter of FY09, the numbers for the AHF and IHF were 36 hours of combined unplanned 

downtime and an availability (how often the facility is operational when planned) of 90%.

ARC has developed an investment strategy for the arc jet complex, and the objective for the 

strategy is to achieve an availability of 95%+. This plan identifies: (a) investments to reduce 

deferred maintenance and maintain operational capability; (b) future infrastructure refurbishment 

which emphasizes maintainability and robustness; (c) designs to improve energy and resource 

efficiency; and (d) compliance with all current air and water environmental regulations. This 

plan integrates a recent facility condition assessment, which identified $5.4 million in reliability 

and safety issues that need to be addressed quickly and another $15 million that should be 

addressed within 4 years. These reliability and safety recommendations focus on the preservation 

of existing operational capability, and not on design changes to significantly improve reliability
Evaluation of Arc Jet Facilities Report

48

or to provide an upgrade to technical capability. In addition, capital investment projects 

identified to address issues with large systems and increase systems capability are as follows:

• Replace Steam Vacuum System (SVS) Boiler. The current boiler was fabricated in 1946 

and installed in 1961, is obsolete, has low efficiency, and will not meet expected future 

NOx emissions regulations. The ARC boiler is currently operating in compliance with 

Bay Area air quality limits of 30 ppm for NOx emissions, but these emission limits are 

expected to be lowered to 5 ppm in 2012, which might require a negotiated waiver to 

maintain operations at current performance levels. However, an Air Quality District 

regulation states that boilers operated at less than 10% of their annualized maximum 

power are exempt from this emission requirement, and the maximum annualized power 

usage for the ARC boiler has been 7%. This implies that ARC will have no problem with 

this regulation unless their current capacity increases by more than 30%. If the Air 

Quality District changes this exemption or if a negotiated waiver cannot be obtained for 

the expected lower NOx level limit, the ARC arc jet complex will have to cease 

operations. Although the ARC boiler is old, it was inspected in 2009 and found to be in 

sufficient condition to operate for an additional ten years. 

• 150 MW Power Supply. Health monitoring of the power supply has detected initial 

component breakdown for these long-lead items. 

• IHF Flow Controls, Test Chamber, Diffuser, and Gate Valve. Increasing heating and flow 

rates, non-optimized condition and configuration feedback, and longer run durations are 

causing failures in undersized components.

• AHF and PTF Diffusers and Heat Exchangers. To address vacuum and water leaks from 

corroded and fatigued components and seismic regulations.

• SVS Plenum, Piping, and Tanks Seismic Upgrades. To address potential personnel 

injury, vacuum and water leaks, and structural failures from aged plenums, pipes, and 

water tanks during earthquakes and seismic regulations.

5.3.2 Johnson Space Center

The current age and estimated life expectancy and remaining service for the subsystems that 

support the ARMSEF are shown in Table 5.5.
Evaluation of Arc Jet Facilities Report

49

Table 5.5. JSC Arc Jet Complex Subsystem Summary

[Riccio, JSC Experimental Heat Transfer and Upgrade Status]

Several systems and components in the summary are at or beyond their nominal service life. This 

is typical for Government technical facilities; these systems and components are not considered 

to be in critical condition. This analysis was endorsed by JSC in the March 18, 2010, 

presentation to the AJEWG. 

JSC tracks unplanned downtime, and this measure can provide a basis from which facility 

condition can be inferred. In 2006, 2007, 2008, and 2009, JSC experienced approximately 11 

weeks, 0 weeks, 4 weeks, and 0 weeks, respectively, of unplanned downtime. This equates to an 

average availability of 90% over the four-year period. 

JSC has developed a plan to revitalize the ARMSEF, and systems upgrades and estimated costs 

are shown in Table 5.6.

Table 5.6. JSC Arc Jet Complex System Upgrades

[Riccio, JSC Experimental Heat Transfer and Upgrade Status]

JSC’s investment strategy for the ARMSEF also identifies several areas of concern, and these are

as follows:

Subsystem Component

Life 

Expectancy

Current 

Age

Remaining 

Service

Steam Generation Boiler 20 20 0

Heat Rejection Cooling Tower 15 1 14

Heat Rejection Pond 20 2 18

Arc Heater Coolant Pump 20 0 20

Test Gas Storage & Delivery Digital Valves 20 20 0

Test Gas Storage & Delivery LN2 20 30 -10

Test Gas Storage & Delivery GN2, GO2 20 2 18

Data Acquisition & Control Modcomp 15 30 -15

Data Acquisition & Control ABB/ASEA 15 6 9

Model Control Insertion 20 30 -10

Power Conditioning Load Bank 30 5 25

Power Conditioning Transformer 30 1 29

Power Conditioning Rectifier 30 43 -13

Vacuum Ejector 20 20 0

ARMSEF Upgrades Purpose/Improvement Area Cost ($K)

Steam Ejector Tune-up Reliability & Performance 350

Parallel Digital Valves Reliability & Performance 200

Data System Modernization Reliability 500

Test Position 2 Multi Arm Model Throughput 250

High Capacity Steam Ejector New Capability, Reliability 1800

Test Position 1 Real Time Channel View New Capability 100

Test Position 3 Design & Fabrication New Capability, Model Throughput 1000

Mars CO2 Test Gas System New Capability 800

Rectifier Component Modernization Improved Capability, Reliability 1000

Test Position 1 Plug & Play Models New Capability, Model Throughput 250

Coolant System Redundant Pump Leg Reliability 500

Total ARMSEF Upgrades 6750
Evaluation of Arc Jet Facilities Report

50

• Vacuum and Ejector System. Many components are aged and this system is in need of 

complete overhaul. The redesign will include increased capability to permit a higher mass 

flow rate. 

• Boiler System. The boiler causes frequent outages and downtime for the facility, and the 

harsh operating cycles lead to an ongoing risk. A direct boiler replacement has been 

designed, and a Pre-Phase A design for an alternate system to provide steam from Building 

24 has been completed. Although the JSC steam boiler is currently operating at the end of its 

20-year design life, the boiler was inspected and certified in January 2010 and is in sufficient 

condition to operate for another 7 to 10 years.

• Diffuser System. The diffuser system is aged, and a failure puts the facility at risk for long 

downtime. A replacement is required, but is difficult to implement without an extended 

downtime. 

5.3.3 Air Force Arnold Engineering Development Center

The Air Force developed an investment strategy to address revitalization needs and to increase 

technical capability. These investments will close the current gap between AEDC and NASA arc 

jet capability. Included in this plan are the following:

• H2/H3 Stilling and Mixing Chamber. Design and fabricate a stilling and mixing chamber 

and housing compatible with both the H2 and H3 heater stacks to provide additional total 

temperature control at lower enthalpy with mixing air, and to provide improved flow 

enthalpy profiles.

• H2 Diffuser Replacement. Replace the existing 1960s-vintage diffuser to provide higher 

thermal efficiency and capacity.

• H2 Model Positioner System (MPS) Axial Controls Upgrade. Replace the 1980s-vintage 

MPS axial controls.

• Mid-Pressure Arc Heater. Replace the existing Huels heater in the H2 arc tunnel with a 

high-performance, segmented arc heater utilizing the demonstrated technology of the 

operational H3 heater to provide improved simulations for many DOD hypersonics test 

points, with higher enthalpy, efficiency, and cleaner flow. Upgrades to existing facility 

power supply and cooling water systems will be required to support the higherperformance, segmented arc heater for longer run times. As shown in Figure 5.2 below, 

the implementation of this investment (the light blue dotted area) will expand AEDC’s 

arc jet performance to fill much of the pressure/enthalpy gap between the Air Force’s and 

NASA’s current capabilities. 
Evaluation of Arc Jet Facilities Report

51

Figure 5.2. AEDC proposed upgrade to mid-pressure arc heater

[Smith, AEDC Arc Jet Facility Capabilities]

5.4 Mothballing the Existing Arc Jet Complexes at ARC and JSC

Discussions with arc jet operators at ARC, JSC, and LCAT made it clear that mothballing a 

facility for more than three years effectively equates to closing that facility. Costly infrastructure, 

especially boilers and steam vacuum system, deteriorates rapidly when it is not operated.

Mothballing generally removes 85% of the annual cost to operate and maintain a facility, but 

requires an initial investment for the basic preservation of the systems and equipment that might 

later be reactivated. Mothballing requires an annual investment to provide safety and fire 

protection for the complex and a minimal level of equipment and system maintenance and 

operation. If a mothballed facility is reactivated, a subsequent investment in maintenance, repair, 

revitalization, and staff training will also be required before the re-energized equipment and 

systems can become recertified for operation.

Mothballing of both complexes for more than 3 years is essentially the same as closing the 

facilities. The estimated cost for mothballing the existing arc jet complexes over a 30-year period 

is located in a table of cost comparisons in Appendix G: Investment Options, although it is 

unlikely that NASA would continue to mothball a facility for that long. JSC evaluated the 

possibility of mothballing and reactivating their arc jet complex, and their estimates are several 

million to mothball and several million to reactivate. They also estimated that reactivation will

take 18 to 24 months and will be driven by the loss and replacement of critical skills and the 

training required.

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180

Po, atm

Ho, Btu/lb

m

AEDC Segmented 

High-Pressure Arc

(Atmospheric Exhaust)

AEDC Segmented 

Mid-Pressure Arc 

(Subatmospheric

Exhaust)

NASA Segmented LowPressure Arcs

(Subatmospheric Exhaust)

AEDC H2 Huels

(Subatmospheric

Exhaust)

DoD MPA Hypersonic Systems Test Points

PROPOSED UPGRADE:
Evaluation of Arc Jet Facilities Report

52

5.5 Throughput Efficiencies

Existing NASA arc jet throughput can be increased in multiple ways. The implementation of the 

investment strategies developed by ARC and JSC will improve the reliability and the availability 

of the tunnels and supporting systems and will enable the tunnels to be test ready more often. 

Adding a second shift at the ARC arc jet complex and utilizing extended shifts and overtime at 

both Centers would help manage a variable work load. (Note: This is not being advocated by the 

AJEWG, but is considered an option to maintain testing schedules and increase capacity.)

An option that can increase throughput with existing workforce and work schedules is to replace 

a single-model insertion system with an insertion system capable of holding multiple models so 

that, for example, a five-model insertion system could hold one calibration probe and four test 

articles. This type of arrangement could increase throughput by simply increasing the number of 

items that can be cycled through the test stream and by decreasing the number of calibration 

probes required for the test articles and the test stream. 

Another option to increase throughput is via a more efficient method to prepare, mount, and 

check out calibration probes and test articles before they are introduced into the tunnel test bay. 

The installation of a “plug and play” system that has a model/probe assembly room with 

instrumentation and cooling water system checkout capability adjacent to the test bays will 

improve the movement of test articles from delivery box to final test data. A significant 

improvement to this option is through the addition of a chamber or room attached to the test 

chamber where a second or third assembly stand of multiple-model insertion systems could be 

ready to “plug in” to replace the assembly coming out of the chamber. This chamber/room could 

be pumped down to match the test chamber pressure for remote insertion and removal of the test 

model assembly or vented to atmospheric pressure to facilitate model changes while the arc jet 

continues to operate. The adjacent chamber/room could contain two or three multiple-model 

assemblies that would allow many repeat runs at a set condition or allow minor changes in test 

conditions without de-energizing the arc jet. This would minimize or eliminate the recalibration 

that is often required when trying to match a previous set point or when interpolating data 

between runs that had similar set points, and would allow many more test models to be run for 

any given arc jet operation. 

An additional area of improvement is redesigning the arc heaters for maintainability to provide a 

more stable arc operation, reduce the amount of time and effort required to replace electrodes, 

and to allow the easier diagnosis and repair of water leaks. 

All of these options will improve the throughput efficiency. However, NASA should carefully 

assess future testing requirements and the costs associated with meeting these requirements 

before implementing any improvements designed to increase throughput. 

5.6 Summary

Finding 5.1: Facilities need to retain operational status, as mothballing an arc jet complex 

beyond 3 years is tantamount to closure because of the degraded nature of the supporting 

infrastructure.

Finding 5.2: There are opportunities for improving capacity at both complexes. 

Finding 5.3: Staffing levels at both NASA complexes appear to be high.
Evaluation of Arc Jet Facilities Report

53

Conclusion 5.1: Experienced personnel with specialized arc jet training and skills are valuable 

and irreplaceable. Arc jet facilities must maintain a skilled workforce for safe and reliable 

operation. 

Conclusion 5.2: A more thoughtful approach to building new arc jet capability should consider 

the larger, long-term Agency mission requirements, as presented in Section 3.0 of this report; 

integrate the full institutional cost, capability, sustainment, and life cycle into Agency strategic 

planning; and consider the difference between what is known about arc jet technology and the 

knowledge needed to advance the state of the art to design an arc jet facility for future capability.

Conclusion 5.3: In an effort to reduce costs, an independent assessment of roles and 

responsibilities at both the Ames and Johnson complexes should be completed and staffing levels 

reduced by up to 30%.
Evaluation of Arc Jet Facilities Report

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6.0 Conclusions and Plan Forward for NASA Investment in Arc Jet Facilities

NASA needs to invest in an arc jet complex that can support certification of missions that deliver 

crew to the Martian surface and return them safely to Earth, as well as sample return missions 

from beyond LEO. These missions remain the long-term centerpiece of NASA’s exploration 

vision. The AJEWG considered numerous possible options for NASA’s investment, which are 

discussed in Appendix G: Investment Options. The AJEWG concluded that the required test 

conditions are beyond the capability of any existing facility, so new construction is required. In 

fact, the required combination of convective and radiative heating rate is beyond current state of 

the art, so technology development is required for the arc heaters themselves. Although the 

details of the heaters are not defined, there is enough information to define the infrastructure 

required to support the tests, and to begin to design it.

6.1 Required Capability

The AJEWG asked the user community to identify features that should be included in a new arc

jet complex. Their responses are summarized in Table 6.1. The test specifications for safe return 

from Mars indicate that 3,000 W/cm2 of convective heating and 1,400 W/cm2 of radiative 

heating applied to a 6-inch stagnation model at 40 kPa pressure would provide excellent 

simulation of anticipated conditions. This is a reasonable starting point for sizing facility 

infrastructure. Heating and shear levels that can be applied to wedges and panels of similar scale 

should also be considered. Earth return of small science payloads at very high velocity and entry 

to Jupiter require very high heating rates, both convective and radiative, but relatively small 

models are acceptable and larger deviations from nominal conditions may be accepted for 

robotic missions. If the arc jet complex infrastructure is sized for crewed Mars return, science 

missions to other destinations will need to test in non-optimal environments, but they will be 

much more relevant than anything that can be done in existing facilities.

Arc heaters that can deliver these heating levels at these scales do not exist today. A technology 

program is required to develop new capabilities. Important elements of technology development 

are discussed Section 6.3. Even without knowing the details of the arc heaters that will need to 

be housed in the complex, much of the infrastructure design can begin immediately and complex 

construction can begin before the new heaters are fully designed.

In 2007, an AOA study was conducted by Ares Corporation to evaluate options for arc jet 

support for certification of Orion at Lunar return conditions for the LEAF project. A similar 

study is recommended for Mars Direct Return certification requirements. Since certification 

requirements for this mission are not yet defined, a parallel effort should be conducted to lay out 

a certification and mission assurance roadmap for all missions to be supported by arc jet testing. 

Elements of the proposed roadmap are discussed briefly in Section 6.4. Even before a 

comprehensive study is performed, we can state that a power supply of at least 100 MW will be 

needed, which is substantially larger than the supplies at existing complexes.

A single arc facility will not support all mission types. Arc jet complex infrastructure should 

have multiple bays to accommodate different arc heaters. There should be at least one bay 

dedicated to arc test technology development and low-TRL material evaluation, so that these 

activities can be continuously pursued in parallel with mission support testing. A minimum of 

four bays will be required, and six bays would be preferred.
Evaluation of Arc Jet Facilities Report

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Table 6.1 Future Arc Jet Needs: Summary of Responses from End Users

Test Conditions Model Size Test 

Gases

Combined 

Convective 

Radiative 

Heating

Control of 

Flow 

Conditions

Knowledge of 

Test 

Conditions

Instrumen

tation

Cost, Access, 

Throughput

Operations

Commercial 

LEO

Thermally similar 

to current facilities

~ 10 cm dia x 40 

cm long

Cost and access 

wise, improved 

access and cost 

structure to ease 

barriers to testing 

and material 

development 

iteration

Test prep and 

instrumentation area 

and check-out 

independent of the 

facility to facilitate 

quick, accurate and 

efficient testing and 

use of the facility.

ISPT 

(Munk)

At least the 

existing capability 

(PTF through IHF)

Increased sample 

size is a nice-tohave; significant 

scale-up is not 

necessary (but 

we may have 

come to that 

conclusion based 

on facility 

limitations)

Alter

nate 

gases

Combined 

environments

Improve quality 

(repeatability of 

test conditions)

Improve test 

condition 

knowledge, 

especially shear

Improve 

instrumenta

tion

Improve cost and 

throughput

Orion 

(Durrant)

Flexibility and 

control of heat rate, 

enthalpy, pressure, 

shear and boundary 

layer thickness

Larger model 

size (20" x 20" 

panel for OML 

features). 

Adequate 

accommodation 

of curved panels.

Yes More 

automated test 

condition 

settings

Better flow

monitoring 

capabilities

Improved 

instrumenta

tion

Improved test 

throughput: 

improved model 

installation 

approaches, more 

models per run

Don 

Curry

Restore capability 

for lunar and 

planetary missions

Improve 

uniformity, 

reduce 

contamination

Orion 

(Bouslog)

Expanded test 

envelop

Panel models 18" 

x 18" to 30" x 

30" ; Stagnation 

models 4" - 10" 

diameter; Wedge 

models 5" to 12" 

square

New 

gas 

mixtures

Run 

temperature and 

pressure 

profiles 

simultaneously. 

Radiant heater 

zones for 

Match timedependent 

heating profile 

for mission 

trajectory

Different arc 

heater designs 

to compare 

differences in 

nominally 

identical 

conditions. 

Facilitate nozzle 

changes, plenum 

changes, arc heater 

modifications
Evaluation of Arc Jet Facilities Report

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Test Conditions Model Size Test 

Gases

Combined 

Convective 

Radiative 

Heating

Control of 

Flow 

Conditions

Knowledge of 

Test 

Conditions

Instrumen

tation

Cost, Access, 

Throughput

Operations

thermal 

gradient effects.

Heat flux and 

pressure probes, 

flow chemistry.

Mars 

Entry 

(Steltzner)

0-3,000 W/cm2 

convective + 1-

3,000 W/ cm2

radiative, 1-1,000 

Pa shear, 0-20 atm

CO2

"nice 

to 

have"

0-3000 W/cm2

convective + 1-

3000 W/cm2 

radiative

HIADS 

(Cheatwood)

More uniform 

freestream (PTF 

has swirl)

Better 

characterization 

of freestream

Increase 

throughput

Better adherence to 

facility schedule via 

more reliable 

facilities

Ability to dial 

in flux and 

surface pressure 

to match 

desired profile

Gas 

Giants 

(Venkatapathy)

Up to 20,000 

W/cm2 convective, 

40,000 W/cm2 

radiative (Jupiter). 

Up to 8,000 W/cm2

convective, 5,000 

W/cm2 radiative 

other gas giants

2-4" stagnation; 

turbulent flow at 

moderate 

conditions on 

large samples

Air, 

CO2, 

H2/

He

10,000 W/cm2

convective, 

10,000 W/cm2

radiative

Turbulent flow Improved 

knowledge of 

test 

environment

If the cost/run 

formula is 

modified, we will 

see increased use 

and reduced risk 

(or better mass)

ETDP -

Wright

Earth return: 1,500 

W/cm2 convective, 

2,200 W/cm2

radiative, 40 kPa 

pressure, 450 Pa 

shear, 100 MJ/kg 

enthalpy

Turbulent flow 

on larger models 

at flight-relevant 

conditions. 

Models >6" with 

high heat rate, 

pressure, shear

CO2, 

Air

Yes Trajectorybased testingIntegrated 

analysis/testing 

services to 

maximize 

understanding 

of results

Cost/sample no 

more than current, 

throughput at least 

matching current 

complexes

Clean separation 

between research 

and production 

facilities (R&D 

needs currently 

sacrificed for 

sustaining 

engineering testing)
Evaluation of Arc Jet Facilities Report

57

Support for different test gases is needed, although individual bays do not need to be plumbed 

for all gases. Pure air, pure nitrogen, and mixtures of oxygen, nitrogen and argon should all be 

provided. Large-scale testing in CO2 at moderate combined heating rates and small-scale testing 

in H2/He at very high heating rates should be supported.

Several respondents stressed the importance of test profiles that mimic the variation of heating 

and pressure throughout an entry trajectory. The complex infrastructure should support variation 

of power and pressure throughout a test entry.

Beyond the requirements for mission-relevant test conditions, responses in Table 6.1 consistently 

note the importance of having better knowledge of the conditions to which the model is exposed. 

New test boxes must be designed with adequate optical access for flow diagnostics and particle 

identification. They should also support thermal and pressure surveys of the core flow.

Respondents further noted that cost per test-article exposure is an important metric. Several 

indicated they would perform more tests if throughput were increased. In recent years, 60% of 

exposures at ARC and 40% of exposures at JSC have been calibration probes. The most effective 

way to improve throughput is to increase the number of stings. The proposed design for LEAF 

included six model arms, with two additional arms for calorimeter and pitot probe. A similar 

configuration is appropriate for new tunnels. 

6.2 Options for New Capability

Options for providing upgraded capability include:

• Add a new arc jet facility to an existing complex

• Build a new arc jet complex with one arc jet facility to augment existing capability

• Build a new arc jet complex with multiple arc jet facilities to augment and replace 

existing capability

The LEAF AoA compared the first two of these options. It concluded that the preferred option 

for delivering Lunar return capability was the first option, to add a new arc heater to an existing 

complex (ARC’s), but noted in passing that construction of a new complex would be required for 

Mars return capability. That conclusion should be reviewed in a new study focused on Mars 

return requirements, but it is driven primarily by the combination of model size and heating rate 

requirements: existing arc tunnels cannot deliver sufficiently heated gas to models of the 

required scale. Furthermore, some compromises related to power supply, test box layout, 

diffuser, and steam generation were made to accommodate LEAF at ARC. Schedule was a 

driver, because an extra year of construction for a new complex did not permit adequate ground 

testing prior to Orion test flights. With more schedule latitude, such compromises should be 

revisited in a new study.

When new construction is evaluated, several sites should be considered as viable options. The 

location should be chosen to ensure ready access to plentiful and cheap power and water, low 

impact on air and water quality, convenient access for qualified personnel and test customers, 

and minimal intrusion of operations into the surrounding communities. A site that has other 

major test complexes provides greatest flexibility for sharing support personnel when test 

demand is low, thereby mitigating annual operating costs. It is expected that NASA would 

consider both ARC and JSC, but other sites, such as AEDC, might be considered if they clearly 
Evaluation of Arc Jet Facilities Report

58

offer advantages in these criteria. Although existing arc jets at AEDC do not support NASA 

mission profiles, the Air Force is interested in extending their capability into a range of 

conditions that more closely approach NASA needs. However, sharing infrastructure would 

require collaboration across agencies for strategic planning and management and to ensure 

adequate accessibility.

New construction provides the best opportunity to deliver state-of-the-art technical capability 

with efficient infrastructure and operations. These efficiencies can deliver a life-cycle value that 

is competitive with the upgrade of existing facilities. New construction will also allow NASA to 

eliminate the deferred maintenance accumulated in existing complexes and will help reduce the 

overall average facility age and improve overall facility condition. 

The estimate of the 30-year cost for new construction of an arc jet complex comprises the initial 

investment, the annual operations and maintenance, and the periodic refurbishment necessary to 

keep a complex viable and recapitalized. Two cost estimates were developed for the initial 

investment to build a new construction arc jet complex that included the LEAF capability and 

three other tunnels that would duplicate the existing capability at ARC. The first was developed 

by the ARES Corporation and was included in the original LEAF AoA. The second estimate was 

for the same capability identified in the AoA but was performed by facilities engineering 

personnel at ARC. The estimates were based on a narrow focus on Orion requirements, however, 

which did not consider the cost of enhancements that could address requirements from other 

missions. A tunnel to support higher-energy requirements would cost more. Since the 

requirements for a new tunnel have yet to be determined, the 30-year cost estimate is provided as 

a range of the costs that would likely be involved. The initial investments identified are the basis 

for this estimate, but are considered to be the lower bounds of the range, and a 50% premium on 

the escalated ARC estimate is used to determine a reasonable higher bound. 

Regional differences in construction costs would also be a factor in the estimate for the initial 

investment required, and these differences are captured in Table 6.2 below. This data is from the 

Engineering New-Record, 20-City National Index, and regional differences for several cities are 

captured in the Construction Cost Index (CCI) and then normalized to construction in San 

Francisco (the CCI Factor). The CCI uses local prices for general construction materials, such as 

concrete, lumber, and structural steel and local union wages. However, it does not account for 

specialized equipment, such as boilers, steam ejectors, and high-power electrical distribution 

components, since the cost of this type of equipment does not have a regional bias and 

differences in installed cost are primarily due to transportation factors. From the CCI Factor 

column, general construction materials and labor costs in Dallas and Birmingham (AEDC) are 

40% lower than in San Francisco and Cleveland. This 40% difference will be reduced when 

high-cost, specialized equipment is included in a construction cost estimate, and a reasonable 

difference for total construction costs is 25%. 
Evaluation of Arc Jet Facilities Report

59

Table 6.2. Regional Construction Cost Index

Data from Engineering News-Record, 20-City National Index

Construction Cost Index (CCI) as of March 2010

CCI Factor relative to San Francisco

The second component of the 30-year estimate is the annual cost for operations and maintenance, 

and there are also regional differences for labor costs. Half of the current ARC arc jet complex 

annual operation and maintenance costs is labor (12% for civil servants and 37% for 

contractors). This annual number provides a basis for the cost of operations and maintenance in a 

new complex, since the upstream and downstream infrastructure will still be shared, and the 

simultaneous operation of multiple tunnels is unlikely. A range is used for a new complex at 

ARC to reflect the implementation of Conclusion 5.3 and to allow for the possibility the new 

complex will require more resources to operate and maintain, and this range is escalated at 2% 

per year for inflation. The cost of labor will also reflect regional differences, and two data 

sources exist to determine regional discounts for NASA locations. The first is the data NASA 

accumulates for its workforce and reports on nasapeople.nasa.gov. Average annual salary data 

can be found by linking through The NASA Workforce Profile to Workforce Measures, and 

average salaries at ARC are 12% higher than at JSC. The second source is presentations provided 

during the Center visits. Each presentation contained current contractor labor costs, and a 

comparison of these costs reveals that the average salary at ARC is 4% higher. A reasonable 

estimate of the regional discount at JSC for the combined workforce is 5%. This regional 

difference is more pronounced for AEDC. The AJEWG contacted the AEDC procurement office 

to identify the labor rate associated with the Aerospace Testing Alliance contract the Air Force 

uses to operate and maintain their wind tunnels and testing capability. The Air Force pays an 

average contractor labor rate that is 22% lower than NASA pays at the ARC arc jet complex. A 

reasonable estimate of the regional discount for a workforce at AEDC is 20%.

The last component of the 30-year estimate is the cost to revitalize and recapitalize the complex. 

The facility presentation from ARC includes the projects accomplished since 1990 and an 

investment strategy intended to refurbish, upgrade, or replace capability (revitalization) and 

infrastructure (recapitalization). These items form the basis for the ARC revitalization and 

recapitalization estimate. Accounting for procurement of specialized equipment and for the labor 

required for installation and activation, the effective regional discount at JSC and AEDC for 

revitalization and recapitalization is estimated to be 20%. Such a discount would probably not be 

fully realized in a new build, but it points to potentially significant cost differences by location.

All of these estimated costs are captured in Table 6.3 [deleted in public version of report] and are 

graphed in Figure 6.1. These data indicate regional labor differences are worthy of consideration 

in the selection of location for a new complex. 

City CCI CCI Factor

Baltimore 6011 0.62

Birmingham 5720 0.59

Cleveland 9989 1.03

Dallas 5339 0.55

Los Angeles 9770 1.00

New Orleans 4935 0.51

San Francisco 9728 1.00
Evaluation of Arc Jet Facilities Report

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6.3 Considerations for Upgrading to Future Capability

The first option in this section, add a new arc jet facility to an existing complex, assumed 

utilizing the existing complex as is. While building augmented capability that takes advantage of 

existing infrastructure was reasonable to consider at the ARC arc jet complex, the AJEWG did 

not consider this option to be technically reasonable at JSC. Making ARC healthy would involve 

refurbishing and repairing the arc jet systems and components. To bring JSC to an equivalent 

technical capability to ARC’s would require replacing most of the complex, including the arc 

heaters, water systems, vacuum systems, and power supply and adding tunnels. It would be 

possible to make JSC’s existing complex healthy, but upgrading the capability would be 

equivalent to a new build. So for JSC, the equivalent to “Make ARC healthy, build a new tunnel 

at ARC” would be “Make JSC healthy, build a new complex at JSC.” There were no existing 

estimates to use for this option, so it was extrapolated from the data available to the AJEWG. 

Figure 6.1. Estimated 30-year cost of options

The cost analysis predicts that both options where existing NASA arc jet complexes are made 

healthy and upgraded with new capability to meet the 30-year future requirements would be 

more expensive than building a new complex at that Center, and neither is considered a good 

investment strategy.

The estimates of the 30-year costs of the options indicate that trying to take advantage of existing 

capability will be the most expensive of the options. Also, over the 30-year period of interest, 

investment differences between locations for new construction are significant enough to be a 

factor in the location decision.

$0 

$500 

$1,000 

$1,500 

$2,000 

$2,500 

ARC JSC AEDC Existing ARC Existing JSC

Cost ($M)

Options

30-Year Cost of Options 

Higher

Lower

Estimated

Build New

Arc Jet Complex

at ARC

Build New

Arc Jet Complex

at JSC

Make ARC Healthy,

Build New Tunnel at ARC

Build New

Arc Jet Complex

at AEDC

Make JSC Healthy,

Build New Arc Jet

Complex atJSC
Evaluation of Arc Jet Facilities Report

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6.4 Technology Development Requirements

To provide the performance capability needed for a future arc jet complex, a significant 

investment in arc heater technology will be required. There are sizable gaps between the current 

state of the art in arc heater performance and that required for missions beyond LEO. Also, arc 

technology is needed to provide a better understanding of the arc jet flow field. Some of the 

issues and possible ways to address them are presented below.

6.3.1 Understanding the Arc Jet Flow Field

There have been long-standing differences in the results obtained from testing the same materials 

in the ARC and the JSC arc jet facilities. It is important to know which facility produces the flow 

field that more closely approximates the true entry environment and to understand the source of

the differences. Possible causes for the difference in material response are the incomplete mixing 

of O2 and N2 at JSC, the addition of argon at ARC, or the difference in enthalpy and pressure 

profiles between the two facilities. To resolve this issue, a number of activities are proposed:

1. Perform a “round robin” series of tests at ARC, JSC, and Boeing LCAT using the same 

test material, flow-field conditions, and configuration. This will permit a comparison of 

the effects of simulated air (JSC), air with a small percentage of argon (ARC), and pure 

air (LCAT).

2. After the test series above, JSC should reconfigure either their TP-1 or TP-2 arc heater by 

adding a ring electrode at the cathode and operate this heater first with pure air and then 

on air with argon added in the same ratio as that used at ARC, and compare the results. 

3. Compare arc heater configurations, enthalpy and pressure profiles, and test conditions 

(pressure, heat flux, and Mach number) between the two facilities.

For simulation of entry into the atmosphere of other planets, arc jet operation will be required 

with other test gases such as CO2, He/H2, and N2. Again, the TP-1 or TP-2 arc heater at JSC 

would be ideal for this development to learn how to operate with these test gases and to obtain 

arc reliability and performance data. JSC personnel should draw upon the ARC experience with 

He/H2 from the previous operation of the Giant Planet Facility and upon Marshall Space Flight 

Center’s ongoing experience with a 1 MW He/H2 heater.

Development of improved flow-field instrumentation is critical to the understanding of material 

test results. This includes both intrusive and nonintrusive measurements. Nonintrusive 

diagnostics are particularly important because the flow field is left undisturbed. The challenge 

has always been to obtain meaningful measurements in an unsteady, high temperature, luminous, 

ionized flow produced by arc heaters. The development and use of these advanced instruments is 

critical to a better understanding of the arc jet flow.

6.3.2 Closing the Simulation Gap for Future Missions

For missions beyond LEO, the gap is significant between present day arc jet facility capabilities 

and those required for future missions (see Section 4). Major advances beyond current state of

the art in arc heater performance and facility capability are needed. Several avenues for arc 

facility technology and development are suggested below:

1. Arc Heater Performance Improvement: The segmented arc heater design is considered 

mature. It has been incrementally improved over the past 50 years in both performance 

(enthalpy) and reliability. However, additional minor improvements are still possible and 
Evaluation of Arc Jet Facilities Report

62

should be pursued. Development of improved cooling techniques for the electrodes and 

segments will allow hardware survival at higher wall heat flux and higher arc current,

which will produce higher enthalpy. However, no more than a 10% to 20% increase in 

performance can be expected from improved component cooling.

2. Arc Jet Flow Field Augmentation:

a. Many of the missions to Mars and beyond will experience significant radiative 

heating, in addition to the high convective heating that arc jets can provide. 

Augmentation of the flow field with an external radiation source will be required. 

Arc lamps with beams focused on the test model surface provide one possible 

method for radiant heating. Laser beams provide an alternative way to provide 

substantial radiative heating, but the effect of a single wave length source would 

need to be investigated and understood. ARC personnel are already studying 

radiation augmentation methods as part of the planning process for the LEAF arc 

heater. 

b. Another method of adding energy to the flow is through magneto hydrodynamics 

(MHD). This method has the advantage of accelerating the flow velocity directly 

in the supersonic region of the nozzle without adding significant heat. In 

principle, the MHD method is sound. In the past, significant hardware problems 

(wall arcing) and non-symmetric flow field acceleration have resulted in limited 

operational success.

3. Non-Standard Test Techniques: One test technique that has been demonstrated is to 

allow the arc discharge to pass through the nozzle and attach downstream, either to the 

downstream face of the nozzle (ARC concept used on the Giant Planet Facility) or at the 

base of the model sting (Boeing concept). This technique can increase both the 

convective and radiative heating simultaneously, since the arc temperature is 10,000 to 

12,000 degrees Kelvin and the arc is either near or surrounding the model. This technique 

may be suitable only for light gases, but should be studied for air and other gases as well, 

because of its potential for providing significantly higher heat flux on the test model. 

4. Non-Standard Arc Heater Configurations: One method used in the past to build larger 

(higher power) arc heated facilities was to manifold the flow from several arc heaters 

together. In one concept, either four or five arc heaters are located at 90 degrees to each 

other with the flow from each combined and discharged through a single nozzle. Another 

arc heater configuration has incorporated an anode on one end and a cathode on the other 

end in a transverse direction to the flow exiting from the nozzle in the center. LaRC 

previously developed this type of “double-ended” arc heater. However, while these 

devices provide a means to scale to larger sizes, they do not produce higher performance 

(enthalpy).

6.3.3 Sustained Arc Technology Program Required

To better understand the arc jet flow field and to provide the enabling technologies to narrow the 

gap in arc facility performance, a dedicated arc jet development effort is required. NASA should 

provide continuous funding over the next 5-10 years to advance the arc jet simulation capability 

and develop the enhanced performance necessary to produce the next generation of arc heaters. 
Evaluation of Arc Jet Facilities Report

63

ARC and JSC should jointly manage the technology development effort with a common purpose 

and goal. The actual development tests can be performed at either or both complexes to 

maximize the progress toward improving arc jet flow field performance and understanding. 

6.5 Certification and Mission Assurance Roadmap

The level of ground testing for proposed missions depends on NASA’s risk posture, commitment 

to flight testing, and the level of confidence in numerical simulation of the entry physics and 

material chemistry. In the past, these issues have been treated differently by individual missions 

and have sometimes been addressed only qualitatively. Recent programs, including Orion and 

COTS, have specified mission reliability requirements, and allocations have flowed down to 

TPS. Verifying compliance with these allocations is proving to be extremely challenging. If 

planetary protection requirements for return to Earth from Mars continue to impose 1:1,000,000 

failure probability for entry, descent, and landing, as specified for Mars Sample Return, it is not 

clear that even the most rigorous ground test campaign can retire the mission risk. 

NASA needs urgently to review certification requirements and mission reliability allocations for 

TPS. To meet the technology development schedule, this effort should be completed in the next 

year and integrated into the capability requirements to ensure they are consistent with 

certification needs. Recent work on certification strategy for Orion and current work on human 

rating requirements for commercial crew transportation should be generalized into a common 

framework for assuring TPS reliability for all missions. Required levels of reliability may differ 

among missions, and choice of verification approach may also vary, but the methodology should 

be consistent. The certification approach should address the contributions of analysis, ground 

test, and flight test toward understanding material and subsystem behavior. 

Several respondents to the AJEWG survey on arc jet needs stressed the value of flight data that 

provides traceability for ground test and analysis. The optimal arc jet complex must be defined in 

the context of the complete TPS development and design process. As an example, the cost of the 

proposed LEAF facility is about 20% of the estimated cost of a single subscale flight test 

dedicated to retiring TPS risks for Orion (LEX flight test project) [McDonald, LEX Study Team 

Report]). It might not replace the flight test, but the flight test project manager indicated that it 

would help him to sign the Certificate of Flight Test Readiness and it would augment the value 

of the flight test by providing a much larger data set for comparison and correlation. Technology 

programs can balance investment among ground facilities, analysis methodology improvements, 

and engineering instrumentation on missions and dedicated flight tests. 

Optimal use of an arc jet complex must include low-TRL development work with direct support 

of missions. Much of the effort required to qualify materials can be managed through material 

and subsystem development programs, rather than being borne by individual missions. NASA 

should develop a family of qualified materials for a range of entry environments, to be adopted 

and carried to certification by individual missions.

6.6 Transition and Institutional Management

The skills and knowledge of the technicians, engineers, and managers at existing arc jet 

complexes will be needed to develop the next level of arc jet capability and, subsequently, to 

operate the new complex. Provision will need to be made to maintain safe operations while 

drawing down or transferring workforce to support the new build. A break in continuity, which 

could result from the immediate threats to maintenance and operation (M&O) funding for 
Evaluation of Arc Jet Facilities Report

64

Johnson, could create an unnecessary loss in personnel that would compromise the introduction 

of new arc jet capability.

Existing infrastructure and arc heaters must also be managed efficiently through the period of 

transition. The agency has benefited from strong cooperation between the two NASA complexes 

in recent years. This positive relationship should be encouraged and supported. The arc jet 

managers at ARC and JSC proposed to the AJEWG that their complexes should be managed 

cooperatively as one Agency portfolio. They indicated that the requirement for individual facility 

robustness could be relaxed by leveraging the capacity of the two complexes. They suggested

deferring all proposed refurbishments until calendar year 2016. This proposal fits well with the 

AJEWG conclusions and timeline describing the transition of the facilities’ technology in the 

following section. The AJEWG supports this creative solution to stabilizing near-term arc jet 

operations.

Common management of agency arc jets will apply a common cost basis for testing. Until now, 

separate complexes have been funded by different organizations within NASA, so they have had 

distinct cost recovery practices. Furthermore, customers collocated with the facilities have 

benefited from convenient access and low-cost test opportunities. More equitable access to the 

test complex for all customers could engage a larger community and would foster additional 

innovative TPS solutions. Facility operators and customers all recognize that full-cost recovery 

decreases utilization and stifles low-TRL material development. On the other hand, suggestions 

that users should not be responsible for any of the facility cost would reduce incentive to 

rigorously plan and execute their test programs. NASA needs to generate a cost recovery 

structure that maximizes the strategic benefit of the arc jets.

NASA’s funding and governance of this critical institutional technical capability has been 

inadequate. The current list of deferred maintenance provides evidence that the lack of reliable 

and sustained funding has contributed to deterioration of arc jet systems. Revitalization activities 

have often been funded by individual projects or missions, so that capability has been focused on 

specific needs rather than being optimized for maximum value to the agency. To ensure 

sustainable and efficient operation of a new arc jet capability, NASA needs to commit to 

continuous and consistent institutionalized funding and resource management. 

6.7 Development Schedule

The AJEWG concludes that the Agency should immediately begin efforts leading to the 

construction of a new arc jet complex, and the notional schedule shown in Table 6.4 identifies 

the top-level activities that will lead to this new complex becoming operational. The 

requirements definition necessary for the infrastructure design should begin immediately. The 

project milestones include a PDR in 12 months, a CDR 12 months later, construction groundbreaking 12 months beyond that, and the new complex becoming operational 5 years from now. 

In parallel with the infrastructure build is the technology development required for a new arc jet 

complex. This technology development will focus on the radiative capability associated with 

high-energy entry conditions and how this level of external radiative heating will be generated 

and focused on a test model; extend the state of the art in arc jet heater operation at continuous, 

high power levels through improved cooling methods and nonstandard configurations and test 

techniques; and improve the flow field capability required for condition validation, data 

acquisition, and test sample certification through alternate cathode configurations, alternate test 
Evaluation of Arc Jet Facilities Report

65

gases and gas combinations, intrusive and non-intrusive instrumentation, and increasing enthalpy 

through the use of magneto hydrodynamics.

Also shown in Table 6.4 is the transition of the existing ARC and JSC arc jet complexes through 

the infrastructure build. The last Shuttle program launch, STS-133, is scheduled for September 

2010, and the JSC complex should transition to one-shift operations immediately after this 

launch. JSC should also transition into support for the technology development required for the 

new complex, and should plan for an orderly phase-out after the completion of the technology 

development efforts. ARC should reduce their operations by December 2010 to a capacity 

required by the Agency. Operations at the ARC complex should continue through construction of 

the new complex to provide a capability to address issues associated with integrated systems 

testing, but the phase-out of the ARC complex should coincide with the new arc jet complex 

becoming operational. 

Table 6.4. Notional Schedule for Transition to New Arc Jet Capability

6.8 Summary

Finding 6.1: The return on investment of rehabilitating and upgrading existing complexes, or 

building a new complex, would be positive. Although arc jet test cost is significant, it is a 

necessary cost for achieving many of NASA’s proposed missions. The total cost of construction 

is on the same order as one or two subscale flight tests.

Finding 6.2: Arc jet users are cost sensitive, especially commercial customers. They will do 

more testing if the cost per test is reduced.

Finding 6.3: NASA must have skilled and knowledgeable personnel to develop and operate the 

next generation of arc heaters. 

Finding 6.4: NASA funding and governance of critical institutional technical capability is 

inadequate. Arc jets have had intermittent funding over several decades, and preventative 

maintenance has suffered. Strategic Capabilities Assets Program (SCAP) funding to Ames 

Task Name Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Comment

Infrastructure Build

 Requirements definition Begin immediately

 Preliminary Design Review ◊ September 2011

 Critical Design Review ◊ September 2012

 Break ground ◊ September 2013

 Construction

 Arc Jet complex operational ◊ September 2015

Technology Development

 Radiative capability

 Arc heater capability

 Flow field capability

 Implementation

Transition of Existing Complexes

 STS-133 ◊ September 2010

 JSC to one-shift operation ◊ December 2010

 JSC technology development

 JSC phase out

 ARC restructuring ◊ December 2010

 ARC operations and technology development

 ARC phase out

FY10 FY11 FY12 FY13 FY14 FY15
Evaluation of Arc Jet Facilities Report

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Research Center has allowed them to work down a backlog of deferred maintenance, resulting in 

improved availability. JSC has benefited from Shuttle and Constellation program funding, which 

is expected to go away in 2010.

Conclusion 6.1: NASA needs to make a serious investment in arc jet infrastructure. Investment 

in the range of $200-500 million in addition to continuing operating costs will be needed in the 

next 10 years. Resource requirements will be diligently challenged and will limit future technical 

options.

Conclusion 6.2: Decisions on transition to a new complex need to consider retention and 

sustainment of highly-qualified staff. Recent cooperation between ARC and JSC has had positive 

benefits for the Agency and that relationship should be fostered and supported during the 

transition.

Conclusion 6.3: Cooperative management of JSC and ARC complexes is recommended while a 

new complex is being developed. 
Evaluation of Arc Jet Facilities Report

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7.0 Findings and Conclusions

Finding 2.1: Arc jet testing has proven to be a core competency and required capability of 

NASA. 

Finding 2.2: Every NASA atmospheric entry mission has relied on arc jet testing for TPS 

development.

Finding 2.3: Arc jet facilities provide the only ground-based means of simulating entry heating 

rates in a reacting flow environment for flight-relevant durations.

Finding 2.4: Ablator design policy currently applies large margins to cover uncertainty in 

applied loads and material response. Improvements in arc jet diagnostics and test article 

instrumentation can reduce uncertainties and hence reduce margins

Conclusion 2.1: Existing ablator design policy is incomplete, because some failure modes are 

not fully understood, so their contribution to system reliability is not quantified. More rigorous 

examination of material failure modes will enable more defensible mission assurance 

assessment. Characterization of failure modes is better managed as a material development 

activity rather than being conducted for individual missions. 

Conclusion 2.2: Currently available diagnostic capabilities and instrumentation techniques 

should be infused into NASA arc jet standard practice. This infusion is best managed as an 

Agency strategic investment rather than as a programmatic responsibility.

Finding 3.1: Arc jet testing will be needed even for LEO return missions, for which materials 

already exist and operational experience is in hand. Existing test capability is adequate for this 

mission type. Capacity requirements to support LEO return are dependent on certification 

philosophy.

Finding 3.2: NASA and DOD share a mutual reliance on arc jet test capability. Air Force 

strategic planning relies on the availability of NASA arc jets for testing of hypersonic cruise 

vehicles. AEDC supports high-shear test conditions that are relevant to NASA.

Finding 3.3: Greater arc jet capability will be required for missions that NASA intends to fly 

within 30 years. Enthalpy, combined convective-radiative heating, test gas, shear, pressure, 

turbulence, and model size are among facility features to be addressed.

Finding 3.4: Arc jet facilities that provide more precise control and knowledge of the test 

conditions, and that have enhanced diagnostics to analyze gas species will benefit the maturation 

of low-TRL thermal protection concepts and materials technologies.

Finding 3.5: The available TPS choices for flight consideration are not optimal for many 

missions, and the TPS choices could be increased with improved accessibility and lower cost to 

use arc jets to develop low TRL concepts.

Finding 4.1: The simulation regimes of the present facilities are sufficient for simulating low 

Earth orbit entries and certain regimes for Lunar return. However, these facilities are inadequate 

to fully evaluate the TPS for a Mars or deep space Earth return or certain planet entries such as 

the Gas Giants.

Finding 4.2: Existing NASA facilities have capability in terms of model size and performance 

that is not duplicated by DOD or commercial facilities.
Evaluation of Arc Jet Facilities Report

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Finding 4.3: An inspection of the performance envelopes shows that the JSC capability is 

basically a subset of the ARC combined capability.

Finding 4.4: Incremental improvements in arc heaters will not deliver the higher test capability 

needed for more ambitious NASA exploration missions to Gas Giants and human return from 

Mars.

Finding 4.5: The AEDC power supply cannot operate at low voltage and high current, which is 

required to power a NASA-type arc heater which operates at low pressure. Therefore, if AEDC 

is considered as a potential site for operating NASA-type arc heaters, a new power supply will 

need to be procured.

Conclusion 4.1: NASA must bear the responsibility of designing and developing facilities with 

improved capability in order to successfully support future NASA missions.

Conclusion 4.2: A focused technology development effort is required to establish the arc jet 

testing capability required by NASA for future missions.

Finding 5.1: Facilities need to retain operational status, as mothballing an arc jet complex 

beyond 3 years is tantamount to closure because of the degraded nature of the supporting 

infrastructure.

Finding 5.2: There are opportunities for improving capacity at both complexes. 

Finding 5.3: Staffing levels at both NASA complexes appear to be high.

Conclusion 5.1: Experienced personnel with specialized arc jet training and skills are valuable 

and irreplaceable. Arc jet facilities must maintain a skilled workforce for safe and reliable 

operation. 

Conclusion 5.2: A more thoughtful approach to building new arc jet capability should consider 

the larger, long-term Agency mission requirements, as presented in Section 3.0 of this report; 

integrate the full institutional cost, capability, sustainment, and life cycle into Agency strategic 

planning; and consider the difference between what is known about arc jet technology and the 

knowledge needed to advance the state of the art to design an arc jet facility for future capability.

Conclusion 5.3: In an effort to reduce costs, an independent assessment of roles and 

responsibilities at both the Ames and Johnson complexes should be completed and staffing levels 

reduced by up to 30%.

Finding 6.1: The return on investment of rehabilitating and upgrading existing complexes, or 

building a new complex, would be positive. Although arc jet test cost is significant, it is a 

necessary cost for achieving many of NASA’s proposed missions. The total cost of construction 

is on the same order as one or two subscale flight tests.

Finding 6.2: Arc jet users are cost sensitive, especially commercial customers. They will do 

more testing if the cost per test is reduced.

Finding 6.3: NASA must have skilled and knowledgeable personnel to develop and operate the 

next generation of arc heaters. 

Finding 6.4: NASA funding and governance of critical institutional technical capability is 

inadequate. Arc jets have had intermittent funding over several decades, and preventative 

maintenance has suffered. Strategic Capabilities Assets Program (SCAP) funding to Ames 
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Research Center has allowed them to work down a backlog of deferred maintenance, resulting in 

improved availability. JSC has benefited from Shuttle and Constellation program funding, which 

is expected to go away in 2010.

Conclusion 6.1: NASA needs to make a serious investment in arc jet infrastructure. Investment 

in the range of $200-500 million in addition to continuing operating costs will be needed in the 

next 10 years. Resource requirements will be diligently challenged and will limit future technical 

options.

Conclusion 6.2: Decisions on transition to a new complex need to consider retention and 

sustainment of highly-qualified staff. Recent cooperation between ARC and JSC has had positive 

benefits for the Agency and that relationship should be fostered and supported during the 

transition.

Conclusion 6.3: Cooperative management of JSC and ARC complexes is recommended while a 

new complex is being developed.
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Appendix A: Acronyms

AEDC Arnold Engineering Development Center

AFRL Air Force Research Laboratory

AHF Aerodynamic Heating Facility

AHSTF Arc Heated Scramjet Test Facility

AJEWG Arc Jet Evaluation Working Group 

AoA Analysis of Alternatives

ARC Ames Research Center

ARMD Aeronautics Research Mission Directorate

ARMSEF Atmospheric Re-entry Materials and Structures Evaluation Facility

ASAP Aerospace Safety Advisory Panel

ATP Aeronautics Test Program

CAD Computer Aided Design

CAIB Columbia Accident Investigation Board

CCI Construction Cost Index

CDI Critical Design Review

CEV Crew Exploration Vehicle

CFD Computational Fluid Dynamics

COTS Commercial Orbital Transportation Services

CMA Cryogenic Moisture Apparatus

DARPA Defense Advanced Research Projects Agency

DOD Department of Defense

DPLR Date-Parallel Line Relaxation

EDL Entry, Descent, and Landing

EDL-SA Entry, Descent, and Landing – Systems Analysis

ESMD Exploration Systems Mission Directorate

FIAT Fan/Inlet Acoustic Technology

HEAT-H1 High Enthalpy Ablation Test Unit H1

HEAT-H2 High Enthalpy Ablation Test Unit H2

HEAT-H3 High Enthalpy Ablation Test Unit H3

HIAD Hypersonic Inflatable Atmospheric Decelerator

HPITT Hypersonic Propulsion Integrated Testing Team
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HRR Human Rating Requirements

HyMETS Hypersonic Material Environmental Test System

ICBM Intercontinental Ballistic Missile

IHF Interaction Heating Facility

ISS International Space Station

ITAR International Traffic in Arms Regulation

JSC Johnson Space Center

JTOH Joint Technology Office on Hypersonics

LaRC Langley Research Center

LAURA can’t find on NASA Web site

LCAT (Boeing) Large Core Arc Tunnel

L/D Lift to Drag ratio

LEAF Lunar Environment Arc Jet Facility

LEO Low Earth Orbit

LDR Lunar Direct Return

LIF Laser-Induced Fluorescence

MDR Mars Direct Return

MHD Magneto Hydrodynamics

MOLA Mars Orbiter Laser Altimeter

MSL Mars Science Laboratory

NASA National Aeronautics and Space Agency

NOx Nitrogen Oxide

NPAT National Partnership for Aeronautical Testing

OCE Office of the Chief Engineer

OD Occupancy Days

PDR Preliminary Design Review

PICA Phenolic Impregnated Carbon Ablator

PTF Panel Test Facility

RHTF Radiant Heat Transfer Facility

RCC Reinforced Carbon Carbon

RTF Return to Flight

SLA Super Lightweight Ablator 

SMD Science Mission Directorate
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SOMD Space Operations Mission Directorate

STAB Structural and Technical Analysis Board

STS Space Transportation System (Program)

SVS Steam Vacuum System

TFD Turbulent Flow Duct

TRL Technical Readiness Level

TPS Thermal Protection System

TPTF Truncated Panel Test Facility
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Appendix B: Glossary

Availability: the planned uptime of a facility or asset; the definition of availability is generally 

the sum of planned uptime (operational schedule and planned downtime) divided by the sum of 

planned uptime plus unplanned downtime.

Capability: the set of test conditions that can be achieved at an individual facility or an entire 

complex or complexes.

Capacity: full throughput utilization of a facility or complex, a property of a complex and 

associated staff.

Complex: a location with one or more facilities that includes the supportive infrastructure 

(power, boilers) plus the arc jet(s). 

Facilities Maintenance: The recurring day-to-day work required to preserve real properties 

(land, buildings, structures, utility systems, collateral equipment, and other permanent 

improvements) in such a condition that they may be used for their designated purpose over an 

intended service life. It includes the cost of labor, materials, and parts. Maintenance minimizes or 

corrects wear and tear, forestalling major repairs.

Facility: an arc jet tunnel. 

Greenfield: new construction of a complex.

Maintenance: the recurring actions, funded through an annual and planned budget, necessary to 

keep equipment and systems operational. Includes routine care, preventive maintenance (or 

predictive maintenance), trouble calls, and repair. [NPR 8831.1E] 

Operations: the recurring actions, funded through an annual and planned budget, necessary to 

exercise equipment and systems for some pre-determined purpose. For the Arc Jets, "operations"

involves simultaneously running the equipment and systems required to create the thermal 

simulation environment necessary to capture data on the performance of a calibration probed or 

test model under those test conditions.

Recapitalization: the renewal and modernization of infrastructure to ensure its ability to meet 

current and future program and institutional requirements. Recapitalization projects typically are 

large (costs and schedule) and are designed to last 20-30 years. 

Revitalization: the renewal and modernization of research equipment and systems to ensure its 

ability to meet current and future program requirements. Revitalization projects typically are 

small to medium (costs and schedule) and are designed to last 3-10 years.
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Appendix C: References

- ARC, Basis of Need document for ARC boiler, FPMD Project #15959, July 30, 2009

- Ares Corporation, “Arc-Heated Test Facility Investment and Risk Reduction Analysis of 

Alternatives Study for Orion Heat Shield Development”, Report No. 063010514-001, May 2007.

- Austin, Howard, “Summary of Current NASA Facility Maps,” Eloret Corp., NASA Ames 

Research Center.

- Bowman, Keith, Air Force Research Laboratory: Arc Jet Testing Perspective, HQ presentation, 

February 16, 2010

- Curry, Don, Past Experience Using Arc Jet Testing for Human Spacecraft TPS. JSC presentation, 

February 8, 2010

- Del Papa, Steven, “Atmospheric Reentry Materials and Structures Evaluation Facility,” presented 

February 8, 2010.

- Kardell, Matt, “Boeing LCAT Facility Arc-Jet Test Capability”, Presentation to AJEWG, 

February 16, 2010.

- Laub, Bernie, et al., Past Experience: A Different Perspective, ARC presentation, February 10, 

2010

- McDonald, Mark, Lunar re-Entry eXperiment (LEX) Study Team Final Report, March 2008

- Munk, Michelle, User Briefing: Future Missions, JSC presentation, February 8, 2010

- NASA, “Entry Thermal Protection,” NASA SP-8014, August 1968

- Prabhu, Dinesh, Modeling as an Alternative or Augmentation to Testing, ARC presentation, 

February 17, 2010

- Raiche, George, “NASA Ames Arc Jet Complex Overview”, Presentation to AJEWG, February 

10, 2010.

- Shepard, Charles E. and Wm. C.A. Carlson, “Upgrading of NASA-Ames High-Energy 

Hypersonic Facilities – a Study,” Contract No. NCC2-503, February 1988.

- Smith, Mark D., “AEDC Arc Jet Facility Capabilities and Test Environments”, Presentation to 

AJEWG, February 16, 2010.

- Steltzner, Adam, Mars Exploration Program Arc Jet Use Profile, ARC presentation, February 10, 

2010

- Venkatapathy, Ethiraj, “Arc Jet Capabilities Needed for Future Venus and Outer Planet 

Missions”, Presentation to AJEWG, February 10, 2010.

- Wright, Michael, “Anticipated Arc Jet Usage, Thermal Protection System Technology 

Development in Support of High Mass Planetary Entry and Safe Return of Crew to Earth,” 

Presentation to AJEWG, February 10, 2010.
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Appendix D: Study Information

A.1 Arc Jet Evaluation Working Group

- Mike Ryschkewitsch, NASA HQ, Chief Engineer, Study Lead

- Anthony Calomino, NASA GRC, Working Group Lead

- Mike Mastaler, NASA ATP, Study Executive

- Hal Bell, NASA HQ, Planning and Execution Support

- Walter Bruce, NASA LaRC, Arc Jet Subject Matter Expert

- Peter Gage, Neerim Corp, Arc Jet Subject Matter Expert

- Dennis Horn, AEDC (retired), Arc Jet Subject Matter Expert

- Don Rigali, Sandia National Laboratory (retired), Arc Jet Subject Matter Expert

- Judith Robey, NASA HQ, Independent Program and Cost Evaluation

- Jerry Wahlberg, NASA LaRC and NC State University (retired), Arc Jet Subject Matter Expert

- Calvin Williams, NASA HQ, Facilities Subject Matter Expert

- Linda Voss, Dell-Perot, Report Editor

- Glen Campbell, Dell-Perot, Planning and Execution Support

- Judith Jacobs, Dell-Perot, Support

A.2 Review Schedule and Presentations

Work Statement November 2009

First Draft Report Due February 26, 2010

Final Report Due March 26, 2010

Team On-site at JSC February 8 and 9, 2010

Meetings

Team On-site at ARC February 10 and 11, 2010 

Team On-site at HQ February 16 and 17, 2010

Team On-site at HQ March 18 and 19, 2010

Team On-site at JSC February 8 and 9, 2010

Presentations

- Stan Bouslog, Why Do TPS Engineers Need Arc Jets?

- Andrew Chambers and John Crumpler, SpaceX Thermal Protection Systems

- Don Curry, Past Experience Using Arc Jet Testing for Human Spacecraft TPS

- Steven Del Papa, Atmospheric Reentry Materials and Structures Evaluation Facility

- Scott Durrant, Arc Jet for TPS Design

- James Reuther, presenter, Orion, David Hash, Arc Jet Facility Capabilities and Lunar Return Certification 

Requirements

- E. Heddles, Orbiter TPS Development and Certification Testing At the NASA/JSC 10 MW Atmospheric

- E. Heddles, Alternate Use of the Atmospheric Re-entry Materials and Structures Evaluation Facility (ARMSEF) 

Due to NASA Program Changes 

- John Kowal, Space Shuttle Orbiter and Orion TPS Arc Jet Testing

- John Kowal, Orion TPS Advanced Development Project (ADP) Arc Jet Testing

- Chris Madden, JSC Arc Jet - Introduction

- Chris Madden, EHTF Background

- Jim Milhoun, JSC Arc Jet Tour, Summary of Informal Presentation on Historical Background of JSC Arc Jets, 

February 2010

- Michelle Munk, User Briefing: Future Missions

- Joe Riccio, JSC Experimental Heat Transfer Facilities and Upgrade Status

- W.C. Rochelle, Orbiter TPS Development and Certification Testing at the NASA/JSC 10 MW

- Jeremy Vander Kam and E. Heddles, Facility-to-Facility PICA Recession Comparisons (TP2 vs. IHF/AHF)

- Jeremy Vander Kam, Orion DAC 3 ISS Ascending Node Trajectories
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- Reentry Materials and Structures Evaluation Facility

Team On-site at ARC February 10 and 11, 2010

- Jim Arnold, Past Experience with ARC Arc Jet Complex and Benefits of their Being Integrated with TPS R&D 

and Aerothermodynamics

- Neil Cheatwood, Development of Flexible TPS for Hypersonic Inflatable Aerodynamic Decelerators

- Bernie Laub, Past Experience: A Different Perspective

- Dinesh Prabhu, Modeling as an Alternative or Augmentation to Testing

- George Raiche, Ames Arc Jet Complex Overview Power Supply Configuration Update

- George Raiche, NASA Ames Arc Jet Complex Overview

- Adam Steltzner, Mars Exploration Program Arc Jet Use Profile

- Jeremy Vander Kam, Orion TPS I/O, Reliability as a Function of Test Quantity

- Raj Venkatapathy, Arc Jet Capabilities Needed for Future Venus and Outer Planet Missions

- Mike Wright, Anticipated Arc Jet Usage: Thermal Protection System Technology Development in Support 

of High Mass Planetary Entry and Safe Return of Crew to Earth (ARMD/ETDP Technology Programs)

Team On-site at HQ February 16 and 17, 2010

- Keith Bowman, USAF, Air Force Research Laboratory (AFRL): Arc Jet Testing Perspective

- Matt Kardell, Boeing LCAT Facility Arc Jet Test Capabilities

- Mark McDonald, LEX Study Report

- George Raiche, Ames Arc Jet Complex Overview: Additional Requested Information

- Steve Rickman, Considerations for the Arc Jet Evaluation Working Group (AJEWG)

- Mark Smith, AEDC Arc Jet Facilities Overview

Team On-site at HQ March 18 and 19, 2010

- Christopher Madden and George Raiche, Cooperative Arc-Jet Management Proposal Brief to NASA AJEWG 

A.3 Other Reference Documents

- ARC, Basis of Need document, July 30, 2009

- ARC Basis of Need Document for Boiler, January 29, 2009

- ARC Boiler Replacement Facility Project Document, September 2, 2009

- ARC/JSC Facility Assessment Study for Aeronautics Test Program and Shared Capability Asset Program-Final 

Report, January 2009

- ARC Master Plan, April 2009

- ARC: The Arc Jet Complex (technical brochure), 2000

- Don Ellerby, Orion TPS Thermal Test Plant Facility Status, October 26, 2009

- Steve Frankel, ARC Boiler Replacement Project Paper, April 7, 2006

- Joe Hartman, ARC Complex Overview, March 2, 2006

- Impacts to Agency Mission of Closure of JSC Arc Jet Facility

- JSC Atmospheric Re-entry Materials, October 12, 2009

- JSC Boiler System Upgrade – Economic Analysis, April 24, 2009

- JSC Facility Project Document Describing Boiler, August 31, 2009

- JSC Mechanical and Boiler Systems Upgrade – Economic Analysis, April 4, 2009

- JSC Mechanical and Boiler Systems Upgrade - Economic Analysis, April 24, 2009

- Jacobs Facility Assessment Study for Aeronautics Test Program and SCAP: Final Report, January 2009

- Chris Madden and Steve Rickman, JSC Infrastructure Improvement Plan, September 8, 2008

- Mark McDonald, Lunar re-Entry eXperiment (LEX) Study Team Final Report, March 2008

- Optimization of Agency’s Arc Jet Capacity, Utilization, and Cost

- George Raiche, ARC Complex Capability Description, September 2009

- George Raiche, ARC Infrastructure Planning and Status, September 1, 2009

- George Raiche and Peter Chan, Arc Jet Capability Revitalization Options, January 2010

- SCAP Issues Paper for FY2011-2016
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- D. Mark Smith, AEDC Arc Jet Facility Capabilities and Test Environments, February 16, 2010

- Strategic Capabilities Assets Program Issue Paper

- Strategic Capabilities Assets Program: An Overview, November 30, 2009

- Sverdrup Arc-Heated Facility Investment and Risk Reduction Analysis of Alternatives Study for Orion Heat 

Shield Development
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Appendix E: AJEWG Team Bios

Arc Jet Evaluation Working Group

• Michael (Mike) Ryschkewitsch, Lead

Chief Engineer, Office of the Chief Engineer

NASA HQ

(202) 358-1823

As Chief Engineer, Mr. Michael Ryschkewitsch is responsible for the overall review and 

technical readiness of all NASA programs. The Office of the Chief Engineer ensures that the 

agency's development efforts and mission operations are planned and conducted on a sound 

engineering basis with proper controls and management of technical risks.

Previously, Mr. Ryschkewitsch served as the Deputy Director for NASA's Goddard Space 

Flight Center in Greenbelt, Md., and Director of the Applied Engineering and Technology 

Directorate at Goddard. He joined the Center in 1982 as a cryogenics engineer to work on the 

Cosmic Background Explorer mission. Between those jobs, Ryschkewitsch held several 

management positions and supported projects from the first servicing mission of the Hubble 

Space Telescope in 1993 to the Aeronomy of Ice in the Mesosphere mission launched in April 

2007.

Mr. Ryschkewitsch earned his B.S. in Physics from the University of Florida in 1973 and his 

Ph.D. from Duke University in 1978. 

Arc Jet Evaluation Team

• Dr. Peter Gage

Neerim Corporation (Mountain View, CA)

(650) 646-2897 (office)

(650) 269-9328 (cell)

pgage@neerimcorp.com

Dr. Peter Gage is the Founder and President of Neerim Corp., Mountain View, California, 

which provides systems engineering and design support to government and industry.

Prior to that, Dr. Gage was a Senior Engineer at Valador Inc., where he was the 

Thermostructural Analysis Team Lead for NASA's Advanced Development Project for Orion 

heat shield. He also supported NASA's Simulation-Assisted Risk Assessment (SARA) project 

on Ares 1 Abort Effectiveness. Previously, Dr Gage worked on-site at NASA Ames, where he 

was Technical Director of ELORET Corp.

Dr. Gage has a proven track record in vehicle design for NASA, primarily on Entry, Descent, 

and Landing, and with recent experience on launch vehicles and mission architecture. He also 

has long involvement in development of software and systems to support aerospace design 

teams, having worked on NASA’s Advanced Engineering Environment and several similar 

programs. 
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Dr. Gage is an Associate Editor for Journal of Spacecraft and Rockets. He is an Associate 

Fellow of AIAA, a member of AUVSI and a member of INCOSE. He earned a Ph.D. in 

Aeronautics and Astronautics from Stanford University in 1994.

• Dennis Horn

AEDC (retired; Tennessee)

(931) 461-0262 (home)

931-581-9901 (cell)

horndd@lighttube.net, horndd2@lighttube.net

Dennis Horn is retired (1997) from the Air Force Arnold Engineering Development Center 

(AEDC) and provides consulting work for NASA, AEDC, and Lytec, LLC. 

Dennis is an engineering specialist with over 50 years experience in the field of hypersonics 

and aerothermodynamics. During his 38 year career at the AEDC, he worked 35 years 

developing electric arc heaters used to simulate hypersonic and re-entry flight conditions. He 

was the principal investigator for all segmented arc heaters developed and operated at the 

AEDC. These arc heaters operate at pressure levels up to five times higher than other 

segmented arc heaters worldwide. The largest heater has operated at power levels up to 68 

MWs. His experience at the AEDC includes arc heater performance predictions, hardware 

development, including segment design and fabrication, and arc stability studies. Dennis was 

named an AEDC Fellow in 1989 by the U. S. Government for his contributions in advancing 

the “state of the art” in segmented arc heater technology. 

Dennis earned a B.S. in Mechanical Engineering from the University of Illinois in 1957 and an

M.S. in Theoretical and Applied Mechanics from the University of Illinois in 1958.

• Don Rigali

Sandia National Laboratory (retired; New Mexico)

(505) 856-1620 (home)

(505) 270-5191 (cell)

djrigali@att.net

Mr. Donald (Don) Rigali is retired (1998) from the Department of Energy’s Sandia National 

Laboratories (SNL) and is a consultant to SNL, the Air Force Research Lab (AFRL), Ball 

Aerospace and Tech. Corp., and NASA, including the Columbia Accident Investigation Board 

(CAIB).

Before retiring, Don was the Director for the Aerospace Systems Development Center at SNL 

where he directed work in the areas of National Missile Defense, Theater Missile Defense, 

smart targeting, hypersonic weapons and technology, and access to space. Under Don’s 

direction, the Center became a recognized, national leader for conducting rapid, proof-ofprinciple/pre-prototype demonstrations of re-entry, weapons, countermeasures, space, rocket, 

aerodynamic flight, and handicap mobility systems. Don provided program direction and 

oversight of reimbursable programs for various agencies, including the Ballistic Missile 
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Defense Organization, U.S. Army Space & Strategic Defense Command, Advanced Research 

Projects Agency, U.S. Navy Strategic Systems Project Office, Defense Nuclear Agency, and 

U.S. Air Force Phillips Lab. Other work areas in Don’s history include re-entry systems 

research and development; high speed vehicle research and development; novel reentry 

systems penetration aides; SWERVE (hypersonic glide vehicle flight tested to M=13); highaltitude sounding rocket research and development; high speed (M=7) rocket sled design, 

development, and testing; and wind tunnel testing.

Don earned a B.A. in Liberal Arts from the University of St. Thomas in 1955, a 

B.S. in Aeronautical Engineering from the University of Notre Dame in 1957, 

and an M.S. in Mechanical Engineering from the University of New Mexico in 

1968.

 

• Dr. Gerald (Jerry) Walberg

NASA Langley Research Center (retired)

(757) 723-4607

gwalberg@gmail.com

Dr. Gerald (Jerry) Walberg is retired (2009) from Walberg Aerospace, a research company 

specializing in entry aerothermodynamics, trajectory optimization, and planetary mission 

analysis. After establishing Walberg Aerospace in 1999, Dr. Walberg consulted for the NASA 

Langley Research Center on the Revolutionary Aerospace Concepts Program and carried out 

re-entry safety analyses on the Stirling Radioisotope Power System for Teledyne Energy 

Systems and the Multimission Radioisotope Thermoelectric Generator System for 

Boeing/Rocketdyne. 

From 1957 to 1989, Dr. Walberg was employed at Langley Research Center where he held 

positions ranging from Research Engineer to Deputy Director for Space. Following retirement 

from NASA, he taught at the NASA/George Washington University Joint Institute for 

Advancement of Flight Sciences and then at North Carolina State University, where he was the 

Director of the Mars Mission Research Center in the Department of Mechanical and Aerospace 

Engineering. In this capacity, he provided overall administration for the Center programs, led 

the Center’s mission analysis and design activities, and taught graduate and undergraduate 

courses in hypersonic aerodynamics, celestial and orbital mechanics, and spacecraft design.

As Deputy Director for Space for Langley Research Center, Dr. Walberg planned, directed, 

and coordinated the space-related research, science, and technology activities of the Center. As 

Chief of the Space Systems Division there, he planned and directed the Division’s support of 

current and planned NASA missions and emphasized the aerothermodynamics of advanced 

space vehicles, space energy systems, the development of computer-aided analysis techniques, 

and systems analyses of spacecraft for future missions. In 1979, Dr. Walberg was selected to 

participate in the NASA Executive Development Program at NASA Headquarters. In this role, 

he was responsible for overall long-range planning for space transportation technology, and he 

served as Deputy Chairman for the F.Y. 1981 OAST Space Technology Assessment. As Head 

of the Thermodynamics and Combustion Section, the Gas Radiation Section, and the 

Aerothermodynamics Branch at Langley, Dr. Walberg was responsible for directing a broadbased program of theoretical and experimental research on high-temperature gas dynamics and 
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ablation. He played a lead role in the analysis and testing of the Apollo heat shield. He led a 

team that developed some of the first rigorous analyses of radiatively-coupled flow fields, and 

he supported the Viking, Pioneer Venus, and Galileo Probe missions.

From 1970 to 1987, Dr. Walberg served as Chairman of the Re-entry Sub-Panel of the 

Interagency Nuclear Safety Review Panel. In this capacity, he played a key role in the nuclear 

safety reviews for all U.S. missions that involved the use of nuclear power sources in Earth 

orbit and beyond, directed the reviews of all re-entry analyses, and participated in the 

development of the Safety Evaluation Reports for the Pioneer, Viking, LES, Voyager, and 

Galileo missions.

Arc Jet Evaluation Technical Experts 

• Walter (Walt) Bruce

Langley Research Center; NASA Engineering and Safety Center

(757) 864-7024 (office)

(757) 871-0377 (cell)

walter.e.bruce@nasa.gov

Mr. Walter (Walt) Bruce is a Senior Thermal Engineer in the Langley Research Center’s 

Systems Engineering Directorate. Walt has extensive experience with hypersonic thermal 

testing including test planning for the Flexible Thermal Protection System Project in the Ames 

Panel Test Facility. He was the arc jet test lead for the Mars Science Laboratory Entry, Descent 

and Landing Instrumentation (MEDLI) Project, where he tested 156 models in the Boeing 

LCAT Facility; and the technical lead for the Falcon leading edge material arc jet test in the 

AEDC H2 Facility. He served on the MSL Heat Shield Tiger Team and was the arc jet test lead 

for the Hyper-X (X-43A) nose leading edge, where he tested two models in the AEDC H2 

Facility. He was also the arc jet test lead for the Shuttle leading edge patch repair, where he 

tested 85 models in the Boeing LCAT Facility and 22 models in the ARC IHF.

Prior to this, Walt worked at AEDC in the arc jet facilities, where he performed arc heater 

technology and development testing and managed the development of the AEDC H3 arc heater 

facility, a large, high-pressure, segmented arc heater. He also performed technology testing in 

the Aerospatiale multi-arc heater JP-200 facility and the High Pressure (HP) arc facility in 

Bordeaux, France.

Walt received his B.S. in Mechanical Engineering from North Carolina State University in 

1983 and his M.S. in Mechanical Engineering from North Carolina State University in 1985.

• Dr. Anthony Calomino, Lead

Glenn Research Center 

(216) 433-3311 (office)

(216) 513-0489 (cell)

anthony.m.calomino@nasa.gov
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Dr. Anthony Calomino spent 20 years as a research engineer within the Mechanics and Life 

Prediction Branch at the Glenn Research Center. Dr. Calomino’s primary research interests and 

experience have been in damage analysis and materials behavior modeling for high 

temperature aerospace materials, including refractory materials and composites used in 

commercial, military, and space applications. He worked with the Columbia Accident 

Investigation Board and Return to Flight investigating the mechanical behavior of the 

composite leading edge. For the last four years, Dr. Calomino has served as Hypersonics 

Materials and Structures Lead Engineer within the Fundamental Aeronautics Program’s 

Hypersonics Project under the Aeronautics Research Mission Directorate. 

Dr. Calomino received his B.S. in Structural Engineering from the University of Colorado at 

Boulder, completed an M.S. in Engineering Mechanics at Case Western Reserve University in 

Cleveland, and was awarded a Ph.D. in Materials Science from Northwestern University in 

Evanston. 

• Michael (Mike) D. Mastaler, Working Group Technical Representative

ARMD Aeronautics Test Program; NASA HQ 

(202) 358-1105 (office)

(202) 236-0437 (cell) 

michael.d.mastaler@nasa.gov

For the last 20 months, Michael (Mike) Mastaler has worked as the HQ Liaison for the 

Aeronautics Research Mission Directorate’s Aeronautics Test Program (ATP). He is a 

permanent employee of the Langley Research Center on detail to NASA HQ. In this position, 

he is responsible for all ATP-related activities at HQ and for facilities-related activities for 

ARMD.

Prior to that, Mike was the Deputy Director for Business Management, Center Operations 

Directorate, where he was responsible for the management of $120 million per year budget

associated with wind tunnel operations, facility capital investments and sustainment, and the 

day-to-day operation of the Langley Research Center. Mike has 26 years of experience with 

NASA and has served as a process and fluid systems engineer, Project Manager, and as the 

head of process engineering, mechanical engineering and design, and resources management 

groups. 

Mike earned a B.S. in Mechanical Engineering from Old Dominion University in 1983, an

M.S. in Mechanical Engineering from Old Dominion University in 1989, and an MBA from 

the College of William and Mary in 2001.

• Judith (Judee) Robey

Program Analysis and Evaluation

NASA HQ

(202) 358-0823 (office)

(443) 875-8913 (cell)

judith.l.robey@nasa.gov
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Judith Robey is currently a study manager in the Program Analysis and Evaluation Office and 

manager of the Agency Mission Planning Manifest. Ms. Robey worked for 16 years on the 

International Space Station Program (ISS). This included defining requirements for Destiny 

and International Laboratories for Physical Science research. Additionally, she was the 

program manager for the development of research instruments for several Spacelab missions 

and the fluids, combustion and materials science racks currently on the ISS. She also 

conducted negotiations and agreements with international partners on cooperative ISS research. 

Prior to this Ms. Robey worked for 6 years as a research scientist at the Jet Propulsion 

Laboratory. Ms. Robey received her degree in physics at the University of California, Los 

Angeles.

• Calvin Williams

Facilities Engineering and Real Property Division

NASA HQ

(202) 358-2322 (office)

(301) 442-2380 (cell)

calvin.williams@nasa.gov

Calvin Williams is the Chief of the Planning and Real Estate Branch in the Facilities 

Engineering and Real Property Division, where he manages the Agency’s real property 

portfolio and Agency master planning efforts. He has recently assumed the responsibility to 

manage the Strategic Capabilities Asset Program Branch in addition to his other 

responsibilities.

Mr. Williams joined NASA in 2002, where he served as the Code OJX’s Lead Program 

Manager for Code R (Aeronautics) Centers. His responsibilities included managing the 

Construction of Facilities projects at NASA’s Venters. He also served as the Sustainable 

Design Champion at NASA Headquarters, leading the Agency’s efforts in sustainable designs 

and certifications under the U.S. Green Building Council’s Leadership in Energy and 

Environmental Designs program.

Before coming to NASA, Mr. Williams worked for the National Institutes of Health (NIH) in 

Bethesda, Maryland for 12 years. He held several positions, including program manager, 

business manager, and management representative for ISO 9001 in the Design, Construction, 

and Alterations Branch. Mr. Williams managed both technical and administrative staff in 

support of design and construction activities at the NIH. As the Design Project Director of the 

Infrastructure Modernization Program, Mr. Williams managed the Master Utility Plan for 

upgrading the entire major utility infrastructure for the NIH Bethesda Campus.

Prior to joining NIH, Mr. Williams worked for the Department of the Navy. He worked in 

facilities engineering positions for both shore activities and on nuclear submarines. He held the 

position of Program Manager at the Chesapeake Division of the Naval Facilities Engineering 

Command, responsible for managing energy and other facility engineering projects. As a 

Program Manager for the Naval Sea System Command, Mr. Williams was responsible for 

testing, monitoring, and extending the operating life of HVAC systems onboard the Navy’s 

nuclear class submarines. 
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Mr. Williams graduated from Howard University with a B.S in Mechanical Engineering. He 

also obtained an M.S. in Engineering from the Johns Hopkins University.

• Hal Bell

Office of the Chief Engineer; NASA HQ

(202) 358-1040 (office)

(202) 391-3935 (cell)

harold.m.bell@nasa.gov

• Linda Voss

Report Editor

Dell Perot Systems

(703) 524-3554 (phone and fax)

(703) 867-1817 (secondary number)

Linda.Voss@psgs.com
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Appendix F: Current Arc Jet Capabilities

This appendix assesses and compares the performance capabilities of the overall arc jet

complexes support equipment and individual arc jet facility capabilities.

Ames Research Center Arc Jet Complex

The ARC arc jet complex consists of eight available test bays, all with vacuum exhaust 

capability located in two separate buildings as shown in Figure F-1. Four of the test bays contain 

operational arc jet facilities: IHF, AHF, PTF, and TFD. All of the test bays share a common 

steam-ejector driven vacuum system, a water cooling system, high-pressure gas system, and 

other auxiliary systems. Two power supplies are available—a nominal 60MW power supply and 

a 20MW power supply. The IHF facility uses the 60-MW power supply while the other three 

facilities use the 20-MW power supply. 

Figure F-1. Aerial View of Ames Arc Jet Complex.

The current configurations for each of the four facilities are presented in Table F-1. Note that the 

AHF facility can be operated with a segmented or Huels type heater, resulting in different overall 

test capabilities.

PTF

IHF

Spare

TFD

AHF

Spare Spare

Spare

Steam Boiler SVS Cooling

Ejector-Condenser

Pollution

Control

Power Supply

HP Air

Water Cooling
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Table F-1. ARC Arc Jet Complex Active Configuration Summary

Each of the four active arc jet facilities are described in detail in the sections below.

Interaction Heating Facility (IHF)

The IHF uses a segmented type arc heater with multiple ring electrodes on either end of the 

heater as shown in Figure F-2. The heater operates off the 60-MW power supply; however, the 

typical maximum operating power is approximately 45 MW. The facility is equipped to run off 

of air or nitrogen test gas and uses argon shield gas over the electrodes to help with arc 

attachment on the electrodes. The heater has cold-air injection capability on the downstream end 

of the heater, prior to the nozzle entrance, to provide a lower-enthalpy test gas.

A 10-degree half-angle conical nozzle with five individual segments is available (Figure F-3),

which results in a range of nozzle exit diameters from 6 in. to 41 in. Several throat diameters are 

available, which results in a wide range of area ratios with minimal hardware. Free-jet stagnation 

type testing or free-jet shear type testing can be performed using the conical nozzles. The model 

injection system was recently updated and now has four independent sting arms similar to the 

ones shown in Figure F-4. A 8-in. by 32-in. semi-elliptic nozzle is also available, which is 

typically used for large panel (up to 24 in. by 24 in.) shear type testing. Performance envelopes 

for each of these types of testing are shown in Figure F-5 through Figure F-9.

*Heating Rate is a cold wall, fully catalytic value on a 4-inch diameter hemisphere
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Figure F-2. Ames Interaction Heating Facility (IHF).

Figure F-3. 10-degree Conical Nozzle Segments for IHF.

Figure F-4. Model Injection System Showing Two Sting Arms.

Flow
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Figure F-5. IHF Stagnation Performance for Cold Wall Heat Flux vs. Pressure.

Figure F-6. IHF Stagnation Performance for Centerline Enthalpy vs. Pressure.

1

10

100

1000

10000

0.1 1 10 100 1000

Cold Wall Heat Flux (W/cm2)

10cm Hemisphere

Wall Pressure (kPa)

IHF, C.W. Stagnation Point Heat Flux vs. Stagnation Pressure

1

10

100

0.1 1 10 100 1000

Centerline Enthalpy (MJ/kg)

Wall Pressure (kPa)

IHF, Centerline Enthalpy vs. Stagnation Pressure
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Figure F-7. IHF Wedge Test Capability on a 4-in x 4-in Sample, Heat Flux vs. Wall Pressure.

Figure F-8. IHF Wedge test Capability on a 4-in x 4-in Sample, Heat Flux vs. Shear Force.

0

50

100

150

200

250

300

350

400

450

500

0 10 20 30 40 50 60

Cold Wall Heat Flux (W/cm2)

Wall Pressure (kPa)

IHF Wedge Test, 4-in x 4-in Sample

Heat Flux vs. Wall Pressure

0

50

100

150

200

250

300

350

400

450

500

0 100 200 300 400 500 600

Cold Wall Heat Flux (W/cm2)

Shear Force (Pa)

IHF Wedge Test, 4-in x 4-in Sample

Heat Flux vs. Shear Force
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Figure F-9. IHF Panel Test Performance on a 24-in x 24-in Sample, Heat Flux vs. Wall Pressure.

Aerodynamic Heating Facility (AHF)

The AHF can operate with a segmented arc heater, as shown in Figure F-10, or with a Huels arc 

heater. This results in different test capabilities as shown in Table F-1. The facility is typically 

operated with the segmented heater, which has multiple ring electrodes on either end of the 

heater. The heater, segmented or Huels, operates off of the 20-MW power supply and can 

operate using air or nitrogen. The segmented heater uses argon shield gas over the electrodes. 

An 8-degree half-angle conical nozzle with five individual segments, similar to the IHF conical 

nozzle shown in Figure F-3, is available. This results in a range of nozzle exit diameters from 12

in. to 36 in. Several throat diameters are available, which results in a wide range of area ratios 

with minimal hardware. Free-jet stagnation type testing or free-jet shear type testing can be 

performed in this facility. Stagnation models can be as large as 8-in. diameter and wedge models 

as large as 26 in. by 26 in. Five sting arms are available on a linear injection system, as shown in 

Figure F-11, with one swept type sting arm, which is typically used for an instrumentation probe. 

The five-arm model injection system is fully programmable and has the capability of injecting 

the model nearly vertical into the flow or injecting in a transverse motion.

The segmented heater operates at chamber pressures from 1 to 9 atm and bulk enthalpy levels 

from 500 to 14,000 BTU/lbm. Convective heating rates can range from a low value of 0.05 

BTU/ft2

-sec with wedge type testing to a high value of 225 BTU/ft2-sec with the 12-in. diameter 

conical nozzle. The Huels type heater operates at chamber pressures from 1 to 40 atm and bulk 

enthalpy levels from 1,500 to 4,500 BTU/lbm. Convective heating rates are approximately the 

same as the segmented because the surface pressures on the model tend to be higher, which 

offsets the lower enthalpy typically associated with a Huels type heater. 

0

10

20

30

40

50

60

70

0 0.5 1 1.5 2 2.5

Cold Wall Heat Flux (W/cm2)

Wall Pressure (kPa)

IHF Panel Test, 24-in x 24-in Sample

Heat Flux vs. Wall Pressure
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Figure F-10. Ames Aerodynamic Heating Facility (AHF)

Figure F-11. AHF model Injection System.
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Figure F-12. AHF Stagnation Performance, Heat Flux vs. Pressure.

Figure F-13. AHF Stagnation Performance, Centerline Enthalpy vs. Pressure.

1

10

100

1000

0.1 1 10

Cold Wall Heat Flux (W/cm2)

10cm Hemisphere

Wall Pressure (kPa)

AHF, C.W. Stagnation Point Heat Flux vs. Stagnation Pressure

1

10

100

0.1 1 10

Centerline Enthalpy (MJ/kg)

Wall Pressure (kPa)

AHF, Centerline Enthalpy vs. Stagnation Pressure
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Panel Test Facility (PTF)

The PTF uses a segmented arc heater similar to IHF and AHF to drive the facility and operates 

off the 20-MW power supply. This facility is specifically designed to perform panel shear type or 

protuberance type testing and is coupled with a semi-elliptic nozzle. Two semi-elliptic nozzle 

sizes are available, a 4 in. by 17 in. and a 1.5 in. by 6.7 in., which result in either a 14-in by 14-in 

panel test size or a 4-in by 4-in panel test size. The smaller nozzle and resulting smaller panel 

test size result in higher surface pressures, heat flux, and shear on the test sample; however, these 

conditions are not shown in Table F-1. A picture of the larger nozzle and a test sample are 

shown in Figure F-14. The test sample can be inclined in the flow from -4 to +8 degrees and can 

be changed during the run. Run times of up to 30 minutes are possible. There is good optical 

access to the test model face during the run.

The heater operates at chamber pressures from 1 to 9 atm and bulk enthalpies from 3,000 to 

15,000 BTU/lbm. Convective heating rates on the model surface range from 0.5 to 30 BTU/ft2

-

sec. Pressures range from 0.0006 to 0.05 atm. Facility performance is presented in Figure F-15

through Figure F-17.

Figure F-14. Panel Test Facility Test Cabin showing Semi-Elliptic Nozzle and Test Panel.
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Figure F-15. PTF Panel Test Performance on a 24-in x 24-in Sample, Heat Flux vs. Wall Pressure.

Figure F-16. TPTF Panel Test Performance on a 4-in x 4-in Sample, Heat Flux vs. Wall Pressure.

0

10

20

30

40

50

60

0 1 2 3 4 5 6

Cold Wall Heat Flux (W/cm2)

Wall Pressure (kPa)

PTF Panel Test, 14-in x 14-in Sample

Heat Flux vs. Wall Pressure

0

50

100

150

200

250

300

0 5 10 15 20 25 30 35

Cold Wall Heat Flux (W/cm2)

Wall Pressure (kPa)

TPTF Wedge Test, 4-in x 4-in Sample

Heat Flux vs. Wall Pressure
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Figure F-17. TPTF Test Performance on a 4-in x 4-in Sample, Heat Flux vs. Shear Force.

Turbulent Flow Duct (TFD)

The TFD uses a Huels heater to drive the facility and operates off the 20-MW power supply. The 

heater can operate on either air or nitrogen. This facility is specifically designed to perform shear 

type testing and has a 2-in. by 9-in. channel flow test configuration as shown in Figure F-18. The 

test sample is installed so it is part of the channel wall and can be subjected to higher shear values 

than the other ARC facilities. Test sample sizes can be either 8 in by 10 in. or 8 in. by 20 in.

Bulk enthalpies range from 1,300 to 4,000 BTU/lbm with convective heating rates on the model 

surface from 2 to 60 BTU/ft2-sec and pressures from 0.02 to 0.15 atm. Model shear force values 

range from 1 to 15 lb/ft2.

0

50

100

150

200

250

300

0 50 100 150 200 250 300

Cold Wall Heat Flux (W/cm2)

Shear Force (Pa)

TPTF Wedge Test, 4-in x 4-in Sample

Heat Flux vs. Shear Force
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Figure F-18. Turbulent Flow Duct.

Figure F-19. TFD Performance on a 2-in x 9-in Sample, Heat Flux vs. Wall Pressure.

Johnson Space Center Arc Jet Complex

The JSC complex contains two available test bays. Both have vacuum exhaust capability and are 

occupied with active facilities, TP-1 and TP-2. Both test bays share a common power supply, 

steam-ejector driven vacuum system, water cooling system, high-pressure gas system, and other 

auxiliary systems. The power supply is rated for 10-MW continuous power output; however, 

both facilities typically operate at power levels around 5 to 6 MW.

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25

Cold Wall Heat Flux (W/cm2)

Wall Pressure (kPa)

TFD Panel Test, 2-in x 9-in Sample

Heat Flux vs. Wall Pressure
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Figure F-20. Sketch of the JSC Arc Jet Complex.

Both of the arc heaters that drive TP-1 and TP-2 are segmented heaters with a tungsten button 

cathode on the upstream end and a conical copper anode on the downstream end. The test gas is 

a mixture of nitrogen and oxygen with the nitrogen and oxygen being individually injected at 

discrete locations and mixed along the heater bore. The percentages of nitrogen and oxygen can 

be varied. The heater can also be operated on pure nitrogen. Argon is not injected over the 

electrodes during testing, so only oxygen and nitrogen are injected into the heater as the test gas.
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Figure F-21. JSC Arc Jet Facility Showing TP-1 on the Left and TP-2 on the Right.

Test Position-1 (TP-1)

The TP-1 facility is a channel-flow facility that is unique to the Agency. The facility is designed 

with a channel flow configuration having a 2-in. wide channel and three different test locations 

along the 10-degree half-angle nozzle as shown in Figure F-22. The test sizes are: 8 in. by 10 in., 

12 in. by 12 in., and 24 in. by 24 in. The test sample is installed so it becomes part of the nozzle 

side wall. The pressures and heat flux are highest at the upstream test position and lowest at the 

downstream test position. Test performance for the 12-in. by 12-in. and 24-in. by 24-in. sample 

sizes are shown in Figure F-23. A new 4-in. by 4-in, 10-degree half-angle duct has been 

fabricated that will provide higher heat flux, pressure, and shear than the 8-in. by 10-in. test 

station.

The opposing side wall facing the test sample can be instrumented with pressure and heat flux 

gages, or it is possible to heat the wall to provide a radiant heating capability. Optical access to 

the test sample is not possible.
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Figure F-22. TP-1 Channel Nozzle Showing Three Test Locations.

Figure F-23. TP-1 Panel Test Performance for Heat Flux vs. Wall Pressure.

0

10

20

30

40

50

60

70

80

0 1 2 3 4 5 6

Cold Wall Heat Flux (W/cm2)

Wall Pressure (kPa)

TP-1 Panel Test

Heat Flux vs. Wall Pressure

TP-1 12-in x 12-in

TP-1 24-in x 24-in
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Test Position-2 (TP-2)

TP-2 uses a family of 15-degree half-angle conical nozzles with exit diameters of 5, 7.5, 10, 15, 

20, 25, 30, 35, and 40 in. (shown in Figure F-24). The 12-foot diameter test chamber allows 

video and optical temperature measurement access. Two hydraulically controlled sting arms are 

available that can support models weighing up to 500 lbs. The facility can test stagnation type 

models or shear type models using a wedge configuration. The model size is dependent on the 

nozzle exit diameter being used, but four standard wedge configurations are available with test 

sample sizes of 4.5 in. by 5 in., 6 in. by 6 in., 12 in. by 12 in., and 24 in. by 24 in.

Figure F-24. TP-2 40-in. exit Diameter Nozzle Configuration.

Arnold Engineering Development Center Arc Jet Complex

The AEDC arc jet complex contains four free-jet to atmosphere test bays, of which two are 

occupied with active arc jet facilities—H1 and H3. In addition, AEDC has a vacuum-capable test 

bay, which is occupied by the H2 facility. The two free-jet to atmosphere facilities, H1 and H3,

provide high-heating and high-pressure simulation, which is of little interest for NASA missions. 

Therefore, the H1 and H3 heaters will not be evaluated in this report. The H2 heater, however, 

does have test capabilities that overlap an area of interest for NASA, specifically, test simulation 

in higher pressure, higher-shear operating ranges.

The H2 facility is driven by a Huels arc heater, as shown in Figure F-25, from the 70-MW power 

supply and uses air as the test gas. The heater typically operates at a maximum power of 42 MW. 

A five-sting arm, computer controlled model injection system can inject models into the flow at 

variable speeds and move models axially in the test flow during the test. Multiple models or 

probes can be put on each sting arm, as shown in Figure F-26. Stagnation type models or wedge 

type models can be tested. Maximum run times are from 3 to 30 minutes depending on the test 

condition. The nozzle exit diameters range from 5 to 24 in. Flow-field stagnation enthalpies 

range from 1,200 to 6,500 BTU/lbm. Facility performance is shown in Figure F-27 and Figure 

F-28.
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Figure F-25. AEDC H2 Huels Type Arc Heater.

Figure F-26. View of AEDC H2 facility Test Cabin and Model Injection System.
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Figure F-27. H2 Wedge Test Performance Compared with NASA Wedge Test Performance.

Figure F-28. H2 Stagnation Test Performance Compared with NASA Facility Performance.
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Boeing LCAT Arc Jet Complex

The Boeing arc jet complex has two test bays, one free-jet to atmosphere and one with vacuum 

exhaust capability. The LCAT facility occupies the vacuum capable test bay and is driven by a 

12-MW power supply. The LCAT facility has a Huels arc heater. A rotary model injection 

system can test up to four models per run; however, typically only three models are tested per 

run. Three conical nozzles are available with 4-in., 6-in., and 12-in. exit diameters. In addition,

the LCAT facility has a square nozzle and a semi-elliptic nozzle. Performance of the LCAT 

facility is shown in Figure F-31 through Figure F-34.

Figure F-29. View of Boeing LCAT Facility.

Figure F-30. View of LCAT Test Cabin Interior and Model Injection System.

Nozzle Exit

Viewing Port

Clamping Sample Holder

In Test Position

Rotary Model

Injection System

Calibration Model

(Stagnation Heat Flux

And Pitot Pressure)

Diffuser

Entrance
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Figure F-31. LCAT Stagnation Performance of Heat Flux vs. Pressure.

Figure F-32. LCAT Stagnation Performance of Centerline Enthalpy vs. Pressure.

1

10

100

1000

10000

0.1 1 10 100 1000

Cold Wall Heat Flux (W/cm2)

10cm Hemisphere

Wall Pressure (kPa)

LCAT - C.W. Stagnation Point Heat Flux vs. Stagnation Pressure

1

10

100

0.1 1 10 100 1000

Centerline Enthalpy (MJ/kg)

Wall Pressure (kPa)

LCAT, Centerline Enthalpy vs. Stagnation Pressure
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Figure F-33. LCAT Wedge Test Performance, Heat Flux vs. Wall Pressure.

Figure F-34. LCAT Wedge Test Performance, Heat Flux vs. Shear Force.

0

50

100

150

200

250

0 5 10 15 20 25 30

Cold Wall Heat Flux (W/cm2)

Wall Pressure (kPa)

LCAT Wedge Test

Heat Flux vs. Wall Pressure

LCAT, 3-in x 3-in

LCAT, 

4.5-in x 5-in

0

50

100

150

200

250

0 100 200 300 400 500 600 700 800 900

Cold Wall Heat Flux (W/cm2)

Shear Force (Pa)

LCAT Wedge Test

Heat Flux vs. Shear Force

LCAT, 3-in x 3-in

LCAT, 4.5-in x 5-in
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Appendix G: Investment Options

Several options were evaluated for NASA’s 30-year investment in arc jets to support TPS 

development and operation for future missions. They were compared on the basis of capability, 

capacity, availability, and cost. The AJEWG assumed that no more than one new construction 

complex would be identified as a viable funding possibility. The basis for estimated costs over 

30 years is included in the discussion of each option. A table of individual cost elements for each 

option is included at the end of the section [deleted from public version of report]. 

The options identified for evaluation are:

• Close the existing arc jet complexes at ARC and JSC

• Continue operating both arc jet complexes, but provide no additional investment for 

revitalization and recapitalization

• Make both ARC and JSC complexes healthy, including investment for revitalization and 

recapitalization

• Close the ARC complex and make the JSC complex healthy

• Close the JSC complex and make the ARC complex healthy

1.1 Close the Existing Arc Jet Complexes at JSC and ARC

The AJEWG recognizes that arc jet tests will be required to support future missions, because it is 

not anticipated that missions beyond LEO will be flown without arc jet tests, so this option 

means that test services would be procured outside NASA. The only available Government 

facility is at AEDC, and its low enthalpy, high-pressure conditions are not a good match for the 

environments anticipated for most NASA missions. The only available commercial facility is 

LCAT, at Boeing, but its capabilities do not cover the full test range needed. International 

facilities, most notably Sirocco in Italy, appear to be capable, but complications associated with 

data security and ITAR regulations suggest that regular international testing is untenable. The 

Air Force has relied on NASA test capabilities for some strategic vehicles and stated they would 

not test materials in a foreign facility, even if ITAR restrictions were not an issue. 

Although the near-term cost savings may seem attractive, the long-term costs of relying on an 

external facility have a high risk, and may ultimately exceed the cost of maintaining a NASA 

capability. Also, the availability of arc jet test time, especially for rapid access in a crisis, would 

be poor.

Most importantly, the technical knowledge and skills associated with arc jet design, diagnostics, 

and operations will be lost to NASA.

Estimated Costs

The cost to close and dispose of both complexes is estimated to be several million. 

Although at face value this option offers savings, this option is unacceptable due to high risk of 

lack of access when needed and the loss of critical testing capability and knowledge. 
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1.2 Continue Operating Both Arc Jet Complexes But Provide No Additional Investment for 

Revitalization and Recapitalization

Both complexes could continue to operate for several years without major infrastructure 

investment. The long-term deferral of refurbishment, which is a decision to run to failure, 

effectively amounts to a decision to close the complexes at an uncertain time, when a serious 

failure will render the complexes inoperable. 

Estimated Costs

Two cases are evaluated for this option: the continuation at the current level of operation and 

operations at a reduced level. 

Reducing the operations at ARC will result in a decrease to maintenance, personnel, and 

capacity, and will essentially become proficiency operations only. Operations at JSC will 

decrease from two shifts to one shift. 

These options are also unacceptable, since continuing to operate the facilities without a strategy 

to upgrade or replace to support the long-term needs of NASA will eventually result in an 

unplanned loss of capability.

1.3 Make Both ARC and JSC Complexes Healthy, Including Investment for Revitalization 

and Recapitalization

In recent years, the facilities at ARC and JSC have been heavily utilized, with ARC handling all 

planetary mission testing for the Science Mission Directorate and JSC handling the bulk of 

Shuttle testing. ARC has provided backup testing for the Shuttle, and there has been considerable 

coordination of testing between the two facilities for Orion support, both through the TPS 

Advanced Development Project and subsequent Orion insight and oversight work. 

Operational benefits associated with the existence of two geographically distinct facilities have 

been demonstrated in recent years. The redundancy of some capability can compensate for a lack 

of reliability at either complex. The combined capacity permits robust response to surges in test 

requirements, which has been particularly helpful for real-time support of Shuttle missions. 

Interaction of the personnel at different facilities is also fruitful. The distinct groups have 

different approaches to dealing with similar technical issues, so more options are proposed, and 

their relative merits are vigorously assessed. At times when mission test requirements are low, 

the excess capacity can be used to investigate differences in the two facilities and the 

implications for differences in test outcomes. Members of both teams can develop deeper 

understanding of arc jet design and operations through the unique features of each facility. 

Ultimately, this option should ensure current test capabilities and maintain a robust pool of 

highly skilled personnel for arc jet operations. In the short term, vibrant teams at two locations 

are likely to promote innovative approaches for facility development, but in the long term, the 

cost of maintaining two complexes with separate operating teams will leave little funding to 

implement innovations. 

Estimated Costs

This option is not recommended because it does not adequately address NASA’s long-term 

mission goals. Unfortunately, the benefits of operational robustness and personnel interaction 

have a considerable cost due to maintenance of two sets of infrastructure and high staffing levels. 
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The outdated technology at both facilities would be retained, so that the existing capability 

would be delivered inefficiently.

Some of the redundancy benefits of distinct facilities can be realized at a single complex through 

judicious design of infrastructure and arc heaters. Similarly, some of the benefits of two distinct 

teams cross-pollinating to improve test practices can be realized at a single location if personnel 

are organized in separate groups. A single complex might have a group concentrating on testing 

to support mission design and operations, while a second team is devoted to material and TPS 

concept development. The groups could coordinate facility usage and share ideas on potential 

improvements. Such an approach has been effectively employed at AEDC.

1.4 Close the ARC Complex and Make the JSC Complex Healthy

The complex at JSC has less capability and capacity than the ARC complex and, consequently,

has somewhat lower operating costs. It is capable of supporting LEO missions well, but its lower 

power levels provide limited utility for more energetic entry profiles. This option is somewhat 

better than closing both facilities, because some arc jet expertise is retained and small samples 

can be tested effectively, but it does not adequately address NASA’s long-term mission goals.

Estimated Costs

This option is unacceptable in the long term, since it leaves NASA without the higher 

performance capability that currently exists at ARC.

1.5 Close the JSC Complex and Make the ARC Complex Healthy

Closing the JSC arc jet complex and making the ARC complex healthy has the potential to 

reduce total arc jet costs by decreasing capacity and backup robustness without giving up 

capability, because JSC operating conditions are a subset of those achievable at ARC. JSC 

currently has superior functionality in its ability to vary gas mixtures and avoid argon in the test 

stream, but this capability can be implemented at ARC at a modest development cost.

The cost reductions that would accrue through closure of one facility are likely to be smaller than 

anticipated. JSC also operates the RHTF with the same crew now operating the ARMSEF. Either 

the radiant capability would also be lost, or the personnel reductions would be smaller than the 

total number currently operating the arc jets. The remaining team would likely be less productive 

than they are currently. Furthermore, the lack of a second operation may reduce the impetus to 

deliver efficiency improvements at the remaining facility. The cost savings that are achieved are 

unlikely to be redirected to arc jet support at a different Center, making it less likely that the 

remaining complex can upgrade its capability. Existing technology will be maintained, but the 

pool of talent that can drive improvement will shrink.

Estimated Costs

This option should reduce costs relative to operating two facilities, but it reduces capacity and 

introduces some availability risk without delivering substantial capability improvement. In the 

long term, if the Agency chooses not to improve capability, this is a viable option. But it is not 

recommended because it does not adequately address NASA’s long-term mission goals. There 

are significant human resource risks associated with closure of one facility. The TPS 

communities at ARC and JSC have worked together extremely well in the years since the 
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Columbia accident, displaying unity of purpose through RTF and into Orion TPS development 

and oversight. Facility closure is likely to lead to Center-centric decision making. 

Finally, there are real risks associated with concentrating resources at ARC. The likelihood of 

major damage from earthquakes is small but real, and the consequences for Agency mission 

support could be severe. The cost of upgrades that comply with structural codes is relatively 

large in California. ARC might soon require a waiver for air quality. A new boiler would address 

that issue, but air and water quality regulation limits will continue to become more stringent in 

California, and the cost of compliance could be high. Finally, ARC is approaching its quota for 

low-cost hydroelectric power, and the cost and availability of electrical power might be 

problematic in future decades.
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Appendix H: Work Statement

Provide engineering support to the NASA Office of the Chief Engineer for, and be a member of, 

the Arc Jet Evaluation Working Group (AJEWG), a focused, independent evaluation of NASA 

arc jet facilities, considering the availability and use of other hypersonic thermal testing 

facilities, against planned and future mission requirements and provide findings that will help 

inform possible long-term investment strategy alternatives for NASA’s arc jet capability.

Evaluation Purpose

An arc jet facility provides ground-based, long-duration, high-energy density (enthalpy) 

environments for testing thermal protection materials. These facilities are designed to simulate 

heating and aerothermal forces experienced during hypersonic deceleration of a spacecraft 

through a planetary atmosphere. The environments the arc jet can achieve allow material 

engineers and spacecraft designers to: develop new, innovative thermal protection materials; 

select the appropriate heat shield, backshell, and seal design, and validate estimates of its 

response; and flight certify and establish required performance margin for the thermal protection 

system (TPS) design during entry, descent, and landing (EDL). They also provide NASA the 

capability to test, analyze, and consider repair alternatives to on-orbit thermal protection system 

anomalies, as well as the capability to support mishap investigation boards. 

Introduction

In operation, high-pressure air is heated electrically to a flight-like energy enthalpy. This highenergy air is expanded and accelerated to hypersonic speeds through a nozzle into a vacuum test 

chamber where the test article(s) is/are exposed to a flight-relevant heating, pressure, and shear 

environment. The test article is inserted into the flow for periods of up to an hour to simulate the 

long duration exposure of an actual entry. Data is recorded continuously from model-embedded 

sensors and optical instrumentation. Test articles include ablative, as well as reusable materials 

and systems.

The arc jet facility includes elements that are required to accomplish given program or project

requirements, as well as to maintain the facilities in ready-to-operate condition. This includes the 

skilled workforce, support facilities/equipment, suppliers/supplies, and contracts that, when 

combined, perform the arc jet function. Facilities and equipment include all real 

property/structures such as buildings, software and business systems, and any personal property 

that might be required to operate the arc jet. The workforce includes the technical staff (both 

civil servant and contractor) required to safely and reliably operate the facility, as well as to 

conduct analysis, engineering and science, and produce reports. The workforce includes all 

support staff required to conduct business-like functions such as scheduling and budget 

formulation, execution, and reconciliation. Suppliers/supplies, contracts, and other items for 

consideration include O&M, data/data storage, knowledge (intellectual property, reports, and 

collective undocumented wisdom and experience), old and current contracts and contract-related 

termination liability, and all other ancillary supplies, tools, utilities, and consumables required 

for safe arc jet operation.
Evaluation of Arc Jet Facilities Report

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The AJEWG will document requirements and capabilities for current and planned NASA 

missions, as well as aeronautics research milestones and advanced entry system technologies that 

drive the utilization of arc jet facilities used for hypersonic thermal testing. Those requirements 

will be evaluated against the performance envelopes and throughput capacities that are supported 

in the current NASA thermal protection system test facility configuration. Support for all mission 

phases, from precursor technology maturation through sustaining engineering of operational 

systems, should be considered. Driving thermal testing requirements should consider human and 

robotic Mars entry; human and robotic Earth return from the LEO, the Moon or Mars; deep 

space robotic Earth return; robotic science missions to Venus and the Giant Planets; and 

atmospheric entry of robotic science missions to Titan. Table H-1 is provided as a guide for one 

method that could be use to identify driving thermal testing requirements for planned and future 

missions. Hypersonic thermal test facility throughput capacities should consider use of all 

available resources (both NASA and non-NASA), maximum throughput capacity of those 

resources, and envelope of operation of those resources against thermal testing requirements for 

future missions. Throughput capacities of test facilities are not expected to be stagnant, as 

consideration should be given for planned maintenance and facility upgrades. A report will be 

generated to capture results of the evaluation and based on findings and analysis; the report will 

include possible investment strategy alternatives for NASA’s hypersonic thermal test facility 

capability.

Charter

The AJEWG will coordinate their efforts and findings with the Technical Capabilities, 

Requirements, and Utilization Panels of the Facilities Program Board, to inform these panels as 

they develop a 5-10 year Agency investment strategy. Findings should consider:

• Maintaining current capabilities for a specified period of time,

• Consolidation and upgrade of current capabilities as deemed appropriate,

• New construction (“Greenfield” approach),

• Other categories to include combinations of alternatives and utilization of outside capability 

such as Arnold Engineering Development Center (AEDC) or Boeing St. Louis arc jets.
Evaluation of Arc Jet Facilities Report

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Table H-1: Program and Project Requirements for Arc Jet Capability

Program Gas

Input 

Power 

(MW)

Typical 

Test Time 

(heat load)

Types of 

Test 

Article

Model 

Test 

Positions

Nozzle 

Exit 

(Inches)

Mach 

Number

Flow 

Enthalpy 

(Btu/lbm)

Surface 

Pressure 

(atm)

Heating Rate 

(Btu/ft2

-sec)

*Human Mars Entry

*Robotic Mars Entry

*Human Lunar Return

Human ISS Return

Robotic Lunar Return

*Human Mars Return

*Robotic Mars Return

*Deep Space Robotic Return

Robotic Venus Aerocapture

Robotic Venus Entry

Robotic Giant Planet Aerocapture

Robotic Giant Planet Entry

Robotic Titan Aerocapture

Robotic Titian Entry

*ISS Down Mass

*Most likely future missions.

The AJEWG will be comprised of knowledgeable individuals that do not have a stake in the 

outcome, and this working group will be led by Mike Ryschkewitsch, NASA Chief Engineer. 

The AJEWG Lead will engage technical experts and advisors as required. 

Organization

• Draft Report: February 24, 2010, including possible investment roadmap alternatives (rough 

order estimated cost, schedule and risk) that inform the 5-10 year infrastructure investment 

strategy to provide capability through 2040.

Deliverables

• Final Report: March 31, 2010.