April 2009 

NASA/TM-2009-215316 

NESC-RP-05-113/05-034-E 

 

NESC Review of the 8-Foot High Temperature 

Tunnel (HTT) Oxygen Storage Pressure Vessel 

Inspection Requirements 

Michael Gilbert/NESC, Ivatury Raju/NESC, Robert Piascik/NESC, 

Kenneth Cameron/NESC, and Michael Kirsch/NESC 

Langley Research Center, Hampton, Virginia 

Eric Hoffman 

Langley Research Center, Hampton, Virginia 

Pappu Murthy 

Glenn Research Center, Cleveland, Ohio 

George Hopson/NESC 

Marshall Space Flight Center, Huntsville, Alabama 

Owen Greulich and Wayne Frazier 

NASA Headquarters, Washington, DC 
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April 2009 

NASA/TM-2009-215316 

NESC-RP-05-113/05-034-E 

 

NESC Review of the 8-Foot High Temperature 

Tunnel (HTT) Oxygen Storage Pressure Vessel 

Inspection Requirements 

Michael Gilbert/NESC, Ivatury Raju/NESC, Robert Piascik/NESC, 

Kenneth Cameron/NESC, and Michael Kirsch/NESC 

Langley Research Center, Hampton, Virginia 

Eric Hoffman 

Langley Research Center, Hampton, Virginia 

Pappu Murthy 

Glenn Research Center, Cleveland, Ohio 

George Hopson/NESC 

Marshall Space Flight Center, Huntsville, Alabama 

Owen Greulich and Wayne Frazier 

NASA Headquarters, Washington, DC 
Available from: 

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7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 

The use of trademarks or names of manufacturers in the report is for accurate reporting and does not 

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National Aeronautics and Space Administration. 
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NESC Request No. 05-034-E 

NESC Review of the 8-Foot High Temperature Tunnel (HTT) 

Oxygen Storage Pressure Vessel Inspection Requirements

March 16, 2006 
NASA Engineering and Safety Center 

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TABLE OF CONTENTS 

Volume I: Technical Consultation Report 

1.0 Authorization and Notification........................................................................................ 3 

2.0 Signature Page................................................................................................................... 4 

3.0 Team Members, Ex Officio Members, and Consultants............................................... 5 

4.0 Executive Summary.......................................................................................................... 6 

5.0 Consultation Plan.............................................................................................................. 8 

6.0 Description of the Problem, Proposed Solutions, and Risk Assessment...................... 9 

6.1 Description of the Problem ..................................................................................... 9 

6.2 Proposed Solution ................................................................................................... 9 

6.3 Risk Assessment ................................................................................................... 10 

7.0 Data Analysis................................................................................................................... 11 

8.0 Findings, Recommendations, and Observations.......................................................... 11 

8.1 Findings................................................................................................................. 11

8.2 Recommendations................................................................................................. 13 

8.3 Observations ......................................................................................................... 13 

9.0 Lessons Learned.............................................................................................................. 14 

10.0 Definition of Terms......................................................................................................... 14 

11.0 Minority Report (Dissenting Opinions) ........................................................................ 14 

Addendum. Summary of Activities from September 8, 2005 to October 7, 2005................ 15 

Volume II: Appendices 

Appendix A. ITA/I Request Form (NESC-PR-003-FM-01) ....................................................... 20 

Appendix B. LOX Run Tank Sketch ........................................................................................... 23 

Appendix C. LOX Run Tank Analyses ....................................................................................... 24 

Appendix D. NESC Risk Assessment ......................................................................................... 27 

Appendix E. List of Acronyms .................................................................................................... 28 

List of Figures

4.0-1 Schematic Drawing of the 8-Foot HTT for Air Breathing Propulsion Testing .................. 6 

6.3-1 5 x 5 Risk Acceptance Matrix........................................................................................... 10
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NESC Request No. 05-034-E 

Volume I: Technical Consultation Report 

1.0 Authorization and Notification 

The request to conduct a consultation on the 8-Foot HTT Liquid Oxygen (LOX) Storage 

Pressure Vessels was submitted to the NASA Engineering and Safety Center (NESC) on June 6, 

2005. 

The initial evaluation of the request was presented to the NESC Review Board (NRB) and the 

consultation was approved on August 12, 2005. The consultation review was held on September 

7-8, 2005, and a report documenting findings, recommendations, observations was written. 

On October 5, 2005, the consultation team reconvened to review additional information and 

results pertaining to the LOX Run Tank fatigue and fracture analysis results. After reviewing the 

new information, the consultation team developed revised recommendations. The revised 

recommendations, documented in the Addendum to this report, were approved by the NRB on 

October 6, 2005, and presented to the NASA Langley Research Center (LaRC) Executive 

Council on October 7, 2005. 
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2.0 Signature Page 

Consultation Team Members 

Original signed on file

Michael Gilbert, NESC Lead Eric Hoffman, LaRC 

____________________________________ _________________________________ 

Ivatury Raju, NESC Robert Piascik, NESC 

Kenneth Cameron, NESC Michael Kirsch, NESC 

____________________________________ _________________________________ 

Pappu Murthy, GRC George Hopson, NESC 

Owen Greulich, HQ Wayne Frazier, HQ 
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3.0 Team Members, Ex Officio Members, and Consultants 

Michael Gilbert, NESC Chief Engineer, Team Lead 

Eric Hoffman, LaRC Materials 

Pappu Murthy, GRC Structures 

Wayne Frazier, HQ Safety & Mission Assurance (S&MA) 

Owen Greulich, HQ S&MA 

George Hopson, NESC Propulsion Discipline Engineer and Technical 

Warrant Holder 

Ivatury Raju, NESC Structures Discipline Engineer and Technical 

Warrant Holder 

Robert Piascik, NESC Materials Discipline Engineer and Technical 

Warrant Holder 

Kenneth Cameron, NESC Deputy for S&MA 

Michael Kirsch, NESC Principal Engineer 

Terri Derby, Swales Administrative Support 
NASA Engineering and Safety Center 

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4.0 Executive Summary 

The 8-Foot HTT (refer to Figure 4.0-1) is used to conduct tests of air-breathing hypersonic 

propulsion systems at Mach numbers 4, 5, and 7. Methane, Air, and LOX are mixed and burned 

in a combustor to produce test gas stream containing 21 percent by volume oxygen. 

Figure 4.0-1. Schematic Drawing of the 8-Foot HTT for Air Breathing Propulsion Testing 

The NESC was requested by the NASA LaRC Executive Safety Council to review the rationale 

for a proposed change to the recertification requirements, specifically the internal inspection 

requirements, of the 8-Foot HTT LOX Run Tank and LOX Storage Tank. The Run Tank is an 

8,000 gallon cryogenic tank used to provide LOX to the tunnel during operations, and is 

pressured during the tunnel run to 2,250 pounds per square inch gage (psig). The Storage Tank 

is a 25,000 gallon cryogenic tank used to store LOX at slightly above atmospheric pressure as a 

supply source for the Run Tank. Both tanks consist of an inner pressure vessel surrounded by an 

external shell, with space between the shells maintained under vacuum conditions. 

The proposed changes to the inspection requirements include: 
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– LOX Run Tank: from 10 years internal/external inspection to internal/external inspection 

after 1,000 pressure cycles. 

– LOX Storage Tank: from 10 years internal/external inspection to 10 year visual external 

inspection only. 

In reviewing the rationale for the proposed changes, the NESC Review Team determined that the 

fracture analysis was deficient and that the LOX Run Tank was not a “Leak-Before-Burst” 

(LBB) vessel. The NESC Review Team recommended immediate stand-down of the 8-Foot 

HTT until either the analysis deficiencies were corrected or the tank was inspected. The 

recommendation was accepted and the 8-Foot HTT stood-down operations on September 8, 

2005. Efforts to correct the analysis deficiencies began immediately thereafter. 

The NESC Review Team also determined that there were no analyses supporting changes to the 

LOX Storage Tank requirements and recommended that such analyses be performed. 
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5.0 Consultation Plan 

The NESC assembled a team of technical experts, NESC Discipline Engineers, Discipline 

Technical Warrant Holders, and S&MA personnel, led by the LaRC’s NESC Chief Engineer. 

The team met on September 7-8, 2005, to conduct a review and accomplished the following: 

– Toured the facility. 

– Reviewed the materials, stress, fatigue, and fracture analyses results. 

– Interviewed the analysts that performed the analyses. 

– Reviewed the fabrication, service, and repair history of the tanks. 

– Interviewed Facility, S&MA, and Pressure Systems Managers. 

– Consulted with a Non-Destructive Evaluation expert. 
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6.0 Description of the Problem, Proposed Solutions, and Risk 

Assessment 

6.1 Description of the Problem 

Both the LOX Run Tank and LOX Storage Tank were due for internal inspection and 

recertification in calendar year 2000. A review by the Pressure Systems Subcommittee of the 

NASA LaRC Executive Safety Council in late 2004 identified that the 8-Foot HTT LOX Storage 

and Run tanks had not been recertified. Systemic issues related to the missed recertification are 

being addressed by the NASA LaRC. 

It was determined that continued operation of the facility beyond the recertification date was 

warranted based on the following conditions: 

LOX Run Tank (Refer to the sketch in Appendix B) 

• The tank was determined to be LBB by analysis. 

• Monitoring of the vacuum level between the inner pressure shell and the external shell would 

identify the presence of through-cracks in the pressure shell and allow the facility to stop 

operations before catastrophic failure would occur. 

Storage Tank 

• The tank operates at constant temperature and pressure, whereas crack growth is a function 

of temperature and pressure cycles. 

• The tank has an operational safety factor of 8 on ultimate material strength. 

• The allowable working pressure of the tank is 100 psia. The tank nominally operates at 45 

psia. 

6.2 Proposed Solution 

The Pressure Systems Subcommittee recommended to the NASA LaRC Executive Safety 

Council, based on contracted analyses, that the recertification requirement for the 8-Foot HTT 

LOX tanks be changed as follows: 

1. Change LOX Storage Tank requirement to time-based visual external inspection techniques 

only. 
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2. Change LOX Run Time Tank to use 1,000 pressure cycles instead of 10 years in operation as 

basis for inspection. 

6.3 Risk Assessment 

There were no immediate safety risks at the time the review request was evaluated. The analyses 

at that time indicated that sufficient margins existed to allow continued operations even though 

the tanks were at approximately 150 percent of the required inspection interval. The risk 

assessment is shown in Figure 6.3-1. Refer to Appendix D for a description of the NESC Risk 

Assessment likelihood and consequences. 

S – Safety NV – National Visibility MS – Mission Success 

Figure 6.3-1. 5 x 5 Risk Acceptance Matrix 

Safety 

• Probability: Very low probability of immediate failure, based on large analytical margins. 

• Consequence: Explosion and/or fire in proximity to inhabited buildings. 

National Visibility 

• Probability: Very low probability of immediate failure, based on large analytical margins. 

• Consequences: Publicity from failure to address Office of Inspector General (OIG) audit 

report. 

Mission Success 

• Probability: Very low probability of immediate failure, based on large analytical margins. 
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• Impact: Assumed hardware loss between $10M - $100M; no immediate impact to flight 

projects, might impact Exploration initiative. 

7.0 Data Analysis 

The NESC Review Team reviewed the stress, fatigue, and fracture analyses of the LOX Run 

Tank. The individuals that performed these analyses were interviewed by the NESC Review 

Team to gain full understanding and to resolve any questions. The results of the data analyses 

are documented in Section 8.1, Findings. 

Refer to Appendix C for key analyses figures reviewed by the team. 

8.0 Findings, Recommendations, and Observations 

8.1 Findings 

F-1. The damage tolerance analyses are insufficient to demonstrate LBB for the LOX Run 

Tank for the following reasons: 

– Critical crack size is predicted to be less than the tank wall thickness. 

– Fracture mechanics analyses did not account for weld material properties or 

residual stresses. 

– The structural finite element models do not capture changes in thickness, 

geometry, loading, and material properties. 

 The tank, as constructed, contains welded-in forgings for the upper access port and 

nozzles at both the top and bottom of the tank. The properties of the weld material and 

the forgings differ from the properties of the material used for the tank walls, even though 

both the tank wall and forgings are 347 Stainless Steel. The crack growth analysis 

assumed uniform material properties for all sections of the tank and did not include 

analyses of the welds. In addition, material properties for 304 Stainless Steel were used 

in the analyses as being representative of 347 Stainless Steel because material properties 

for 347 Stainless Steel were not readily available. 

 Although a critical crack size less than the tank wall thickness was predicted, it was 

assumed that the crack would also grow perpendicular to the thickness until reaching an 

adjacent nozzle opening, which would act as a crack stop. The crack would then be 
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stable (not growing) and be more than twice the wall thickness in length, thus satisfying 

LBB criteria. 

This assumption did not account for the weldments or the changes in material properties 

along the assumed path of the crack and, therefore, is invalid. Also, the NASA standard 

for LBB is crack length 10 times the wall thickness, whereas the analysis was based on 

crack length 2 times the wall thickness. Refer to Observation O-3. 

F-2. The fatigue analysis method used is inconsistent with the original fabrication inspection 

performed on the LOX Run Tank for the following reasons: 

– The fatigue analysis was performed according to the American Society of 

Mechanical Engineers (ASME) Section VIII, Division 2. Application of this 

analysis is based on construction of the tank to ASME Section VIII, Division 2, 

which requires stringent manufacturing inspections. These inspections set the 

initial crack size to be used in subsequent fatigue analyses based on the actual 

minimum detectable flaw size at the time the inspections were conducted. 

– The LOX Run Tank was actually constructed to ASME Section VIII, Division 1, 

with much less stringent quality assurance, inspection, and process controls. 

– The ASME Section VIII, Division 2, fatigue analysis was performed based on an 

assumed crack size rather than the minimum detectable size from the 

manufacturing inspection process. 

F-3. The LOX Run Tank fatigue life calculations do not currently account for pre-LaRC use. 

The tank was manufactured in 1959, but was first put into service at the HTT in 1989. 

Since 1989, the LOX Run Tank has been subject to about 600 pressure cycles. The tank 

operational history prior to service at the HTT is not accounted for, nor has it been 

demonstrated that the tank was restored to "zero-time" status in 1989. 

F-4. All previous tank inspections have revealed cracks and/or crack-like indications that were 

repaired or removed. The inspection history, shown below, suggests that cracks 

continually initiate or that the inspections may not have found all flaws. 

– 1965: Cracks in 4-inch boss weld repaired 

– 1986: Four linear indications found and ground out 

– 1991: Six linear indications found and ground out 

F-5. No analysis or prior inspection data was available to establish a rationale to change the 

inspection requirements for the LOX Storage Tank. 
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F-6. The physical location of the LOX Run and Storage Tanks necessitated a waiver to 

requirements on proximity of LOX tanks to occupied buildings. The waiver has as an 

acceptance rationale maintaining the tanks in a certified state. 

8.2 Recommendations 

R-1. Remove the LOX Run Tank from run-time pressure service until the LBB rationale is 

verified and the risk of continued operation is accepted, or until an inspection is 

performed and any detected flaws are properly dispositioned (F-1, F-2, F-3, F-4 and F-6). 

R-2. Develop analyses to support a rationale for changing the LOX Storage Tank inspection 

requirements (F-5). 

– The tank can continue in current operation while rationale is developed. 

– The Storage Tank must be determined to be LBB or fracture-critical to establish 

appropriate inspection intervals. 

8.3 Observations 

O-1. Inspection intervals should be determined by both cyclic-loading and maximum time, 

based on industry practices and standards. Lengthening of inspection intervals should 

include as rationale prior inspection history and data. 

O-2. During the review, the team inquired about the Oxygen Hazards analysis for the HTT. 

Retrieval of records was not completed by the time the review team meeting ended. 

O-3. The “ten times the thickness” NASA standard is applicable to thin-walled pressure 

vessels and pipes. For thick-walled pressure vessels (such as LOX Run Tank of 4.73 

inches in thickness), the NASA standards are not clearly defined and the Nuclear Industry 

Code for LBB conditions should be used. The Nuclear Industry Code LBB conditions 

require the development of a through-the-thickness crack with sufficient crack opening 

for the fluid to leak and be detected. 
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9.0 Lessons Learned 

There were no lessons learned during this consultation. 

10.0 Definition of Terms 

Corrective Actions Changes to design processes, work instructions, workmanship practices, 

training, inspections, tests, procedures, specifications, drawings, tools, 

equipment, facilities, resources, or material that result in preventing, 

minimizing, or limiting the potential for recurrence of a problem. 

Finding A conclusion based on facts established during the assessment/inspection 

by the investigating authority. 

Lessons Learned Knowledge or understanding gained by experience. The experience may 

be positive, as in a successful test or mission, or negative, as in a mishap 

or failure. A lesson must be significant in that it has real or assumed 

impact on operations; valid in that it is factually and technically correct; 

and applicable in that it identifies a specific design, process, or decision 

that reduces or limits the potential for failures and mishaps, or reinforces a 

positive result. 

Observation A factor, event, or circumstance identified during the 

assessment/inspection that did not contribute to the problem, but if left 

uncorrected has the potential to cause a mishap, injury, or increase the 

severity should a mishap occur. 

Problem The subject of the technical assessment/inspection. 

Requirement An action developed by the assessment/inspection team to correct the 

cause or a deficiency identified during the investigation. The requirements 

will be used in the preparation of the corrective action plan. 

Root Cause Along a chain of events leading to a mishap or close call, the first causal 

action or failure to act that could have been controlled systemically either 

by policy/practice/procedure or individual adherence to 

policy/practice/procedure. 

11.0 Minority Report (Dissenting Opinions) 

There were no dissenting opinions during this consultation. 
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Addendum. Summary of Activities from September 8, 2005 to 

October 7, 2005 
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Summary of Activities from September 8, 2005 to October 7, 2005 

On September 8, 2005, following a two-day review, the NESC 8-Foot High Temperature Tunnel 

(HTT) Oxygen Storage Pressure Vessel Inspection Requirements Technical Consultation team 

issued a safety recommendation to the Director, Safety and Mission Assurance (S&MA), NASA 

Langley Research Center (LaRC), to immediately stand-down operations of the HTT until 

deficiencies in the fatigue and fracture analyses of the LOX Run Tank could be corrected. This 

recommendation was based on the fact that deficiencies in the analyses negated the then current 

"Leak-Before-Burst" (LBB) result for the LOX Run Tank. "Leak-Before-Burst" was an essential 

part of the rationale for continuing to operate the tank 5 years beyond its specified inspection and 

certification date. The Director, S&MA, LaRC, accepted this recommendation and ordered the 

immediate stand-down of HTT test operations. The findings, recommendations, and 

observations developed by the NESC Technical Consultation Team from the review on 

September 7-8, 2005, are fully documented in the main body of this report. 

Subsequent to the HTT stand-down, an analysis team was formed by the NASA LaRC to update 

the fatigue and fracture analyses. The NESC provided technical assistance to, and consulted 

with, the Center analysis team in critical areas of materials properties and fatigue and fracture 

analysis methods. As a result of improved models, materials data, and revised analytical 

techniques, the Center analysis team determined: 

a. The LOX Run Tank is fracture-critical and not a LBB design. 

b. Conservative damage tolerance analyses showed large analytical margins (factor of 

10+) for a limited number (<100) of additional LOX Run Tank pressure cycles. 

On October 5, 2005, the NESC Technical Consultation Team reconvened via telecon to review 

the results [ref. 1] of the NASA LaRC HTT LOX Run Tank re-analysis efforts. The NESC 

Technical Consultation Team concurred with the results (items a. and b. above) and developed a 

set of revised recommendations and additional observations (listed below). This set of revised 

recommendations and additional observations were reviewed and approved by the NESC Review 

Board on October 6, 2005 and presented (in briefing format) to the NASA LaRC Executive 

Safety Council on October 7, 2005. The NASA LaRC Executive Safety Council accepted the 

NESC recommendations as written. 
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Revised and Additional Recommendations 

R-1 (Revised). Based on conservative analysis assumptions and large analytical margins in the 

revised fatigue and fracture analyses, the NESC Technical Consultation Team’s 

position on the LOX Run Tank is: 

 Completion of the Air Force Research Lab (AFRL) Ground Demonstration 

Engine test program is acceptable, based on an assumed test program of less 

than 100 additional pressure cycles of the LOX Run Tank. 

 The LOX Run Tank should be inspected and recertified immediately 

following the completion of the AFRL tests before any additional test 

programs are conducted. 

R-2 (Revised). Written and approved rationale for external inspection on the vacuum shell only 

of the LOX Storage Tank is required. 

R-3 (New). Stennis Space Center and other NASA facilities should be consulted and surveyed 

for high-pressure LOX tank inspection methods, techniques, and capabilities. 

Additional Observations 

O-4. Atmospheric pressure load modeling in the revised analysis needs to be updated; the 

overall effect is expected to be very minor (order of 14/2250 psi). 

 The atmospheric pressure acts on the external vacuum jacket shell and transfers to 

the LOX Run Tank pressure shell as point loads through standoffs, not as a 

uniform load on the pressure shell. 

O-5. Changes to the baseline inspection requirements may require changes to the NASA HQapproved site waiver for the tank locations. 

 "Waiver-of-the-waiver" approval requirements to conduct the AFRL tests, if any, 

needs to be determined. 

O-6. Vacuum monitoring of the LOX Run Tank as a safety precaution may lead to a false 

sense of security. 
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Reference 

1. Forth, S.C.; Harvin, S.F.; Gregory, P.B.; Mason, B.H.; Thompson, J.E.; and Hoffman, 

E.K. “Damage Tolerance Analysis of a Pressurized Liquid Oxygen Tank”, NASA/TM2006-214274, 2006.
NASA Engineering and Safety Center 

Technical Consultation Report

Document #: 

RP-05-113 

Version: 

1.0 

Title:

NESC Review of the 8-Foot High Temperature Tunnel 

(HTT) Oxygen Storage Pressure Vessel Inspection 

Requirements 

Page #: 

19 of 29

NESC Request No. 05-034-E 

Volume II: Appendices 

A ITA/I Request Form (NESC-PR-003-FM-01) 

B LOX Run Tank Sketches 

C LOX Run Tank Analyses 

D NESC Risk Assessment 

E List of Acronyms 
NASA Engineering and Safety Center 

Technical Consultation Report

Document #: 

RP-05-113 

Version: 

1.0 

Title:

NESC Review of the 8-Foot High Temperature Tunnel 

(HTT) Oxygen Storage Pressure Vessel Inspection 

Requirements 

Page #: 

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NESC Request No. 05-034-E 

Appendix A. ITA/I Request Form (NESC-PR-003-FM-01) 
NASA Engineering and Safety Center 

Technical Consultation Report

Document #: 

RP-05-113 

Version: 

1.0 

Title:

NESC Review of the 8-Foot High Temperature Tunnel 

(HTT) Oxygen Storage Pressure Vessel Inspection 

Requirements 

Page #: 

21 of 29

NESC Request No. 05-034-E 
NASA Engineering and Safety Center 

Technical Consultation Report

Document #: 

RP-05-113 

Version: 

1.0 

Title:

NESC Review of the 8-Foot High Temperature Tunnel 

(HTT) Oxygen Storage Pressure Vessel Inspection 

Requirements 

Page #: 

22 of 29

NESC Request No. 05-034-E 
NASA Engineering and Safety Center 

Technical Consultation Report

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RP-05-113 

Version: 

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(HTT) Oxygen Storage Pressure Vessel Inspection 

Requirements 

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NESC Request No. 05-034-E 

Appendix B. LOX Run Tank Sketch 
NASA Engineering and Safety Center 

Technical Consultation Report

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RP-05-113 

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1.0 

Title:

NESC Review of the 8-Foot High Temperature Tunnel 

(HTT) Oxygen Storage Pressure Vessel Inspection 

Requirements 

Page #: 

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NESC Request No. 05-034-E 

Appendix C. LOX Run Tank Analyses

LOX Run Tank Pressure Profile
NASA Engineering and Safety Center 

Technical Consultation Report

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RP-05-113 

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1.0 

Title:

NESC Review of the 8-Foot High Temperature Tunnel 

(HTT) Oxygen Storage Pressure Vessel Inspection 

Requirements 

Page #: 

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NESC Request No. 05-034-E 

LOX Run Tank Model
NASA Engineering and Safety Center 

Technical Consultation Report

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Version: 

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(HTT) Oxygen Storage Pressure Vessel Inspection 

Requirements 

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NESC Request No. 05-034-E 

LOX Run Tank Top Stresses
NASA Engineering and Safety Center 

Technical Consultation Report

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RP-05-113 

Version: 

1.0 

Title:

NESC Review of the 8-Foot High Temperature Tunnel 

(HTT) Oxygen Storage Pressure Vessel Inspection 

Requirements 

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NESC Request No. 05-034-E 

Appendix D. NESC Risk Assessment 

Significant National 

Prestige and 

Visibility 

High National 

Prestige and Visibility

Moderate National 

Prestige and Visibility 

Low National Prestige 

and Visibility National 

Significance

Minimal or no 

identified National 

Prestige or 

Visibility 

CONSEQUENCES

1 234 5

LEGEND

High – Accepted for 

NESC Board review. 

Probable NESC followon IA.

Medium – Accepted 

for NESC Board review. 

NESC or other NASA IA 

action required.

Low – Not Boarded by 

NESC. Direct referral to 

other NASA IA org.

Could result in death 

or perm. total disability

/ Irreversible severe 

environ damage that 

violates law or 

regulation 

Could result in 

permanent partial 

disability, injuries or 

occupational illness / 

Reversible envinmt 

damage – violates law

Could result in injury or 

occupational illness 

resulting in one or 

more lost work day / 

Mit. envirnmtl damage 

w/o law viol

Could result in 

injury or illness not 

resulting in lost 

work day / Minimal 

envirnmtl damage 

Minimal/no safety or

health plan 

violations / Minimal 

to no environ 

impacts 

Safety, 

Health, 

Environment

Leve 1 2 3 4 5

What is the likelihood the situation or circumstance will 

Level . . . or –. . . 

5

4

3

2

1

Probability

Very Likely

Likely to occur often. Likelihood of occurrence is 

estimated to be greater than 0.10 (10-1) per 

operational opportunity

High Expected to occur some time in the life of the item. Likelihood

of occurrence is estimated to be between 0.01 and 0.10 (10-2 

and 10-1) per operational opportunity

Moderate Likely to occur some time in the life of the item. Likelihood 

of occurrence is estimated to be between 0.01 and 0.001 

(10-2 and 10-3) per operational opportunity

Low

Unlikely but possible to occur. Likelihood of occurrence is 

estimated to be between 0.001 and 0.000001 (10-3 and 10-

6) per operational opportunity

Very Low Likelihood of occurrence is estimated to be less than 

.000001 (<10-6) per operational opportunity 

RISK 

DEFINITION

RISK MANAGEMENT: An organized, systematic decision-making process 

that efficiently identifies risks, assesses or analyzes risks, and effectively 

reduces or eliminates risks to achieving program goals. (NESC Risk 

Management Plan) 

NESC ASSESSMENT RISK MANAGEMENT APPLICATION (NARMA): The NESC 

database used to assess and prioritize concerns brought to the attention 

of the NESC. URL: http://xx 

Risk: Measure of the potential inability to achieve overall program objectives within defined constraints and has two 

components: (1) the probability/likelihood of failing to achieve a particular outcome, and (2) the consequences/impacts 

of failing to achieve that outcome 

Consequence: Impact (typically categorized as negative) to program/project (loss, injury, disadvantage) 

Likelihood: Ordinal scale: Relative ranking of probability of occurrence. Numerical scale: estimated probability an event 

will occur combined with the uncertainty in the probability assessment 

What is the Consequence (Safety, Health, Environment, Mission Success, National Significance) of this NESC 

Safety, Health, Environment is defined as impact to life, health, working 

environment and natural environment 

Mission Success definition includes impacts to Major Mission 

Objectives (MMOs) as well as hardware loss 

National Significance is defined as the degree to which national 

prestige, visibility and public relations are impacted 

Safety, Health, Environment, Mission Success and National Significance

can exist concurrently and are not mutually exclusive 

Risk scoring is accomplished by “multiplying” Likelihood (L) X 

Consequence (C ). Note: numerical value is reflective of the ordered 

pair L, C. Care must be taken when using multiplied falues as 

measures. When determining risk consequence among Cost, 

Schedule, and Technical, the highest score is represented in the NESC 

Risk Matrix as a single score value. 

RISK CONSEQUENCE SCORING TERMS 

NESC RISK ASSESSMENT

Rev A Annex.

L

I

K

E

L

I

H

O

O

L

I

K

E

L

I

H

O

O

5

4

3

2

1

NESC RISK 

1

2

3

4

5

C

O

N

S

E

Q

U

E

N

C

Hardware loss between 

$100M and $250 Million 

/ Failure to meet > 50% 

MMO's 

Hardware loss 

exceeding $250 

Million / Failure to 

meet all Major Mission

Objectives (MMO's) 

Hardware loss 

between $10M and 

$100 Million / Failure 

to meet any one 

MMO 

Hardware loss 

between $1M and $10 

Million / Failure to 

meet > 50% of 

supplemntl objectives 

Hardware loss 

between $200K 

and $1 Million / 

Failure to any one 

MMO 

Mission 

Success

Example

Lost work case per

worker over a 20 

year private 

industry career

Failures per US ELV 

Launch (1988 - 

2001) 

Place holder

Fatal crashes per 

automobile trip 

Fatal crashes per 

passenger airplane 

departure 
NASA Engineering and Safety Center 

Technical Consultation Report

Document #: 

RP-05-113 

Version: 

1.0 

Title:

NESC Review of the 8-Foot High Temperature Tunnel 

(HTT) Oxygen Storage Pressure Vessel Inspection 

Requirements 

Page #: 

28 of 29

NESC Request No. 05-034-E 

Appendix E. List of Acronyms 

AFRL Air Force Research Laboratory 

ASME American Society of Mechanical Engineers 

GRC Glenn Research Center 

HQ Headquarters 

HTT High Temperature Tunnel 

LaRC Langley Research Center 

LBB Leak-Before-Burst 

LOX Liquid Oxygen 

NASA National Aeronautics and Space Administration 

NESC NASA Engineering and Safety Center 

NRB NESC Review Board 

OIG Office of Inspector General 

psig pounds per square inch gage 

S&MA Safety & Mission Assurance 
NASA Engineering and Safety Center 

Technical Consultation Report

Document #: 

RP-05-113 

Version: 

1.0 

Title:

NESC Review of the 8-Foot High Temperature Tunnel 

(HTT) Oxygen Storage Pressure Vessel Inspection 

Requirements 

Page #: 

29 of 29

NESC Request No. 05-034-E 

Approval and Document Revision History 

Approved: Original signed on file 3/24/06 

 NESC Director Date 

Version Description of Revision Office of Primary 

Responsibility 

Effective 

Date 

1.0 Initial Release NESC Chief Engineer’s 

Office 

3/16/06 
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

2. REPORT TYPE 

Technical Memorandum

 4. TITLE AND SUBTITLE

NESC Review of the 8-Foot High Temperature Tunnel (HTT) Oxygen 

Storage Pressure Vessel Inspection Requirements

5a. CONTRACT NUMBER

 6. AUTHOR(S)

Gilbert, Michael; Hoffman, Eric; Raju, Ivatury; Piascik, Robert; Cameron, 

Kenneth; Kirsch, Michael; Murthy, Pappu; Hopson, George; Greulich, 

Owen; Frazier, Wayne

 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

NASA Langley Research Center

Hampton, VA 23681-2199

 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

 8. PERFORMING ORGANIZATION

 REPORT NUMBER

L-19638 NESC-RP-05-113/05-034-E

10. SPONSOR/MONITOR'S ACRONYM(S)

NASA

13. SUPPLEMENTARY NOTES

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified - Unlimited

Subject Category 20 Spacecraft Propulsion And Power 

Availability: NASA CASI (443) 757-5802

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email: help@sti.nasa.gov)

14. ABSTRACT

The 8-Foot HTT (refer to Figure 4.0-1) is used to conduct tests of air-breathing hypersonic propulsion systems at Mach 

numbers 4, 5, and 7. Methane, Air, and LOX are mixed and burned in a combustor to produce test gas stream containing 21 

percent by volume oxygen. The NESC was requested by the NASA LaRC Executive Safety Council to review the rationale for 

a proposed change to the recertification requirements, specifically the internal inspection requirements, of the 8-Foot HTT 

LOX Run Tank and LOX Storage Tank. The Run Tank is an 8,000 gallon cryogenic tank used to provide LOX to the tunnel 

during operations, and is pressured during the tunnel run to 2,250 pounds per square inch gage (psig). The Storage Tank is a 

25,000 gallon cryogenic tank used to store LOX at slightly above atmospheric pressure as a external shell, with space between 

the shells maintained under vacuum conditions.

15. SUBJECT TERMS

NESC, LOX, High Temperature Tunnel (HTT), psig, Leak-Before-Burst (LBB), AFRL, Run Tank fatigue; Fracture analysis, 

inner pressure vessel, external shell

18. NUMBER

 OF 

 PAGES

34

19b. TELEPHONE NUMBER (Include area code)

(443) 757-5802

a. REPORT

U

c. THIS PAGE

U

b. ABSTRACT

U

17. LIMITATION OF 

 ABSTRACT

UU

Prescribed by ANSI Std. Z39.18

Standard Form 298 (Rev. 8-98)

3. DATES COVERED (From - To)

June 2005-Mar 2006

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

510505.06.07.01.99

11. SPONSOR/MONITOR'S REPORT

 NUMBER(S)

NASA/TM-2009-215316

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