J.D. Saunders, T.J. Stueber, S.R. Thomas, and K.L. Suder

Glenn Research Center, Cleveland, Ohio

L.J. Weir and B.W. Sanders

Techland Research, Inc., North Olmsted, Ohio

Testing of the NASA Hypersonics Project’s 

Combined Cycle Engine Large Scale Inlet 

Mode Transition Experiment (CCE LIMX)

NASA/TM—2012-217217

January 2012
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J.D. Saunders, T.J. Stueber, S.R. Thomas, and K.L. Suder

Glenn Research Center, Cleveland, Ohio

L.J. Weir and B.W. Sanders

Techland Research, Inc., North Olmsted, Ohio

Testing of the NASA Hypersonics Project’s 

Combined Cycle Engine Large Scale Inlet 

Mode Transition Experiment (CCE LIMX)

NASA/TM—2012-217217

January 2012

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Prepared for the

58th Joint Army-Navy-NASA-Air Force (JANNAF) Propulsion Meeting 

sponsored by the JANNAF Interagency Propulsion Committee

Arlington, Virginia, April 18–22, 2011
Available from

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at the NASA Glenn Research Center.

Level of Review: This material has been technically reviewed by technical management. 
NASA/TM—2012-217217 1

Testing of the NASA Hypersonics Project’s Combined Cycle Engine 

Large Scale Inlet Mode Transition Experiment (CCE LIMX)

J.D. Saunders, T.J. Stueber, S.R. Thomas, and K.L. Suder

National Aeronautics and Space Administration

Glenn Research Center

Cleveland, Ohio 44135

L.J. Weir and B.W. Sanders

Techland Research, Inc.

North Olmsted, Ohio 44070

Abstract

The NASA Fundamental Aeronautics Hypersonics project is focused on technologies for combined 

cycle, air-breathing propulsions systems to enable highly reliable reusable launch systems for access to 

space. Turbine Based Combined Cycle (TBCC) propulsion systems offer specific impulse (Isp) 

improvements over rocket-based propulsion systems in the subsonic takeoff and return mission segments 

and offer improved safety. The potential to realize more aircraft-like operations with expanded launch site 

availability and reduced system maintenance are additional benefits. 

Among the most critical TBCC enabling technologies as identified in the National Aeronautics 

Institute (NAI) study were: 1) mode transition from the low speed propulsion system to the high speed 

propulsion system, 2) high Mach turbine engine development and 3) innovative turbine based combined 

cycle integration. 

To address these key TBCC challenges, NASA’s Hypersonics project (TBCC Discipline) initiated an 

experimental mode transition task that includes an analytic research endeavor to assess the state-of-the-art 

of propulsion system performance and design codes. This initiative includes inlet fluid and turbine 

performance codes and engineering-level algorithms. This effort has been focused on the CombinedCycle Engine Large Scale Inlet Mode Transition Experiment (CCE LIMX) which is a fully integrated 

TBCC propulsion system with flow path sizing consistent with previous NASA and DoD proposed 

Hypersonic experimental flight test plans. This experiment is being tested in the NASA Glenn Research 

Center 10- by 10-ft Supersonic Wind Tunnel (SWT) Facility. The goal of this activity is to address key 

hypersonic combined-cycle engine issues: (1) dual integrated inlet operability and performance issues—

unstart constraints, distortion constraints, bleed requirements, controls, and operability margins, 

(2) mode-transition sequence elements caused by the switch between the turbine and the ramjet/scramjet 

flow paths (imposed variable geometry requirements), (3) turbine engine transients (and associated time 

scales) during transition. The model will be tested in four test phases to develop a unique TBCC database 

to validate design and analysis tools and address operability, integration, and interaction issues for this 

class of advanced propulsion systems. The test article installation and facility build-up/preparation was 

completed and the inlet performance and operability characterization testing commenced on March 7, 

2011. The major upcoming events of this activity include:

• Phase I: Parametric inlet characterization testing completed—2nd QTR 2011

• Phase II: Inlet system identification tests completed—3rd QTR 2011

• Phase III: Controlled mode transition with simulated engines demonstrated—3rd QTR 2012

• Phase IV: Controlled mode transition with turbine engine demonstrated—3rd QTR 2013

In this paper we will discuss the following: 1) research objectives addressing TBCC enabling 

technologies, 2) features of the CCE hardware design which provide a unique TBCC mode transition data 
NASA/TM—2012-217217 2

base, 3) experimental procedures and test plans including a discussion of the facility and instrumentation, 

and 4) a status of the parametric inlet characterization testing. 

Introduction

The “National Aeronautics Research and Development Policy” (Ref. 1) document, issued by the 

National Science and Technology Council in December 2006, stated that one (among several) of the guiding 

objectives of the federal aeronautics research and development endeavors shall be stable and long-term 

foundational research efforts. Nearly concurrently, the National Academies issued a more technically 

focused aeronautics blueprint, entitled: the “Decadal Survey of Civil Aeronautics—Foundations for the 

Future” (Ref. 2). Taken together these documents outline the principles of an aeronautics maturation plan. 

Thus, in response to these overarching inputs (and others), the National Aeronautics and Space 

Administration (NASA) organized the Fundamental Aeronautics Program (FAP), a program within the 

NASA Aeronautics Research Mission Directorate (ARMD). The FAP initiated foundational research and 

technology development tasks to enable the capability of future vehicles that operate across a broad range of 

Mach numbers, inclusive of the subsonic, supersonic, and hypersonic flight regimes. 

The FAP Hypersonics Project concentrates on two hypersonic missions: (1) Air-breathing Access to 

Space (AAS) and (2) the (Planetary Atmospheric) Entry, Decent, and Landing (EDL). The AAS mission 

focuses on Two-Stage-To-Orbit (TSTO) systems using “air-breathing” combined-cycle-engine propulsion; 

whereas, the EDL mission focuses on the challenges associated with delivering large payloads to (and from) 

Mars. So, the FAP Hypersonic Project investments are aligned to achieve mastery and intellectual 

stewardship of the core competencies in the hypersonic-flight regime, which ultimately will be required for 

practical systems with highly integrated aerodynamic/vehicle and propulsion/engine technologies. Within 

the FAP Hypersonics, the technology management is further divided into disciplines including one targeting 

Turbine-Based Combine-Cycle (TBCC) propulsion. Additionally, to obtain expertise and support from 

outside (including industry and academia) the hypersonic uses both NASA Research Announcements 

(NRA’s) and a jointly sponsored, Air Force Office of Scientific Research and NASA, National Hypersonic 

Science Center that are focused on propulsion research. Finally, these two disciplines use selected external 

partnership agreements with both governmental agencies and industrial entities. 

The TBCC discipline is comprised of analytic and experimental tasks, and is structured into the 

following two research topic areas: (1) TBCC Integrated Flowpath Technologies, and (2) TBCC 

Component Technologies. These tasks will provide experimental data to support design and analysis tool 

development and validation that will enable advances in TBCC technology.

Benefits of TBCC Propulsion

NASA’s Fundamental Aeronautics Program is investigating turbine-based propulsion systems for 

access to space. TBCC propulsion provides the potential for aircraft-like, space-launch operations that 

may significantly reduce launch costs and improve safety due to their following characteristics:

1. Turbine-based propulsion systems exhibit significant specific impulse (Isp) improvements over 

rocket-based propulsion systems in the subsonic takeoff and return mission segments, see Figure 1. 

2. Turbine-based systems can mitigate mission risk by providing operational flexibility for allweather launch, take-off and landing cross-range, powered landing and abort scenarios.

3. Turbine engines afford dual-use capability, adequately serving low speed accelerator missions as 

well as long range cruise missions.

4. Performance growth margin for TBCCs can be inherently designed for the system, yielding a 

robust propulsion package that is able to change with mission requirements.

TBCC propulsion for hypersonic applications requires high Mach turbine engines to accelerate the 

vehicle to scramjet takeover speeds. Major challenges are to develop a turbine accelerator with near 

Mach 4 capabilities and develop a scramjet with a low ignition speed (M <4) to enable transition from the 
NASA/TM—2012-217217 3

low speed to high speed propulsion system. A long term challenge is to understand and design to 

minimize propulsion system dry weight which can counterbalance the predicted Isp (wet weight) benefit.

TBCC Enabling Technologies

The most critical TBCC enabling technologies as identified in the National Institute of Aerospace

study (Ref. 3) were: 1) mode transition from the low speed propulsion system to the high-speed 

propulsion system, 2) high-Mach turbine engine development, 3) transonic aero-propulsion performance, 

4) low-Mach-number dual-mode scramjet operation, 5) Innovative three dimensional flowpath concepts 

and 6) Innovative turbine-based combined-cycle integration. A further breakout of these TBCC enabling 

technology challenges are identified in Figure 2.

Figure 1.—Comparison of specific impulse for turbine-based and rocketbased propulsion systems.

Figure 2.—Technologies to enable TBCC propulsion for access to space vehicles.

TBCC Propulsion Technology Challenge: Develop Air-Breathing 

Propulsion Technology for Two-Stage-to-Orbit Vehicles

High Mach Turbine Tech Challenges:

 Increase Maximum Mach from 2+  4+

 Provide thrust margin over entire range (0<M<4+)

• Light Weight High Temperature Materials

• Thermal Management

• High Temperature Bearings and Seals

• Highly Loaded Turbomachinery

• Propulsion/Airframe Integration 

• Cocooning and Relight 

Scramjet Tech Challenges:

 Reduce Scramjet Ignition Mach Speed (M5  M3)

 Provide transition speed margin (3<M<4)

• Variable Geometry

• Advanced Combustion Schemes

• Light Weight High Temperature Materials

• Thermal Management

• High Temperature Seals

• Propulsion/Airframe Integration

Turbine Based propulsion Hypersonic Scramjet propulsion Hypersonic TBCC propulsion 

LRC

TBCC Propulsion Technology Challenges

 addressed by NASA CCE

 Performance and Operability over flight range

 Inlet / Engine / Nozzle Integration

• Propulsion / Airframe Integration

 Mode Transition / Stage Separation

• Thermal Management 

• Transonic Thrust Margin
NASA/TM—2012-217217 4

Based on the Next Generation Launch Technology (NGLT) studies (Ref. 4), an over-under TBCC 

system (turbine engine over ram/scramjet) was selected as the reference vehicle configuration for a TBCC 

TSTO space access by the NASA FAP Hypersonics MDAO (Multidisciplinary Design and Analysis 

Optimization) discipline. The over-under TBCC configuration and challenges associated with this 

configuration are illustrated in Figure 3. This present study investigates a two-dimensional inlet concept 

designed (Ref. 5) with a mode transition Mach number of 4 and a top end Mach number of 7. The goals 

of the activity are to address key hypersonic combine-cycle engine issues: (1) the operating constraints of 

a high-temperature turbine and a dual mode scramjet engine (specific to the TBCC), (2) dual integrated 

inlet operability and performance issues including unstart constraints, inlet flow distortion effects, bleed 

requirements and controls characterization, and operability margins, and (3) mode-transition constraints 

imposed by the turbine and the ramjet/scramjet flow paths (imposed variable geometry requirements).

The near term emphasis is to understand, demonstrate, and control the mode transition between the low 

speed turbine engine and the dual-mode ram/scramjet engine for a relevant TBCC over/under propulsion 

configuration. This requires a comprehensive understanding of the integrated inlet characteristics and the 

inlet/engine/nozzle interactions to model and predict the behavior of the TBCC propulsion system. In the 

subsequent sections we will summarize the specific TBCC research objectives/questions related to 

integrated flowpath technology, inlet/engine integration, and mode transition between the turbine and dual 

mode ram/scramjet engines. 

(a)

(b)

Figure 3.—Over-under configuration serves as NASA's TBCC TSTO reference vehicle for MDAO. (a) Operating 

configuration before and after mode transition. (b) Features of the propulsion system.
NASA/TM—2012-217217 5

Integrated Inlet Technology

Military Specification (Mil-spec) inlet performance, as measured by total pressure recovery, can be 

achieved for an inlet carefully designed for single point operation. However for a TBCC system, the inlet 

must operate over a wide range of flight conditions and distribute the flow with acceptable distortion and 

unsteadiness to both the turbine engine as well as the dual mode ram/scramjet engine. Common practice 

is to use variable geometry and designed bleed configurations to enable a wide range of inlet operability 

and meet performance requirements including maximizing pressure recovery and minimizing flow 

spillage. However, this added complexity to achieve high performance and operability results in 

additional weight, complex vehicle integration, and an increase in drag. Figure 4 illustrates that the inlet 

pressure recovery can vary by a factor of 4X (assuming Mil-spec can be achieved over the Mach flight 

range) depending on the inlet complexity. Component performance levels (such as total pressure 

recovery) are used in system trade studies for each vehicle configuration and mission such as airbreathing access to space (AAS). To this end, NASA is focusing on the development of validated design 

and analysis tools as well as parametric databases which are required to perform these system trade

studies.

Specific questions related to integrated inlet technology addressed by the inlet performance and 

characteristic (Phase I) testing of the Combined Cycle Engine Large Scale Inlet Mode Transition 

Experiment (CCE LIMX) include: 

• Is Mil-Spec performance achievable over the wide operating range that is required for TBCC 

space access?

• Can design and analysis tools reliably predict inlet performance and operability?

• What is the trade-off between bleed and inlet performance/operability?

• Can design and analysis tools adequately predict operability limits both with and without bleed?

• Can these tools predict low/high speed inlet interaction effects due to varying inlet backpressures 

and low/high speed inlet cowl positions?

Figure 4.—Potential Inlet Total Pressure Recovery for TBCC inlets.
NASA/TM—2012-217217 6

Inlet/Engine Interactions

In order to maintain propulsion system performance through mode transition, the inlet/engine as well 

as the low speed/high speed engine interactions must be controlled to avoid inlet unstarts and engine stalls

while maintaining the proper airflow quality and splits as the low speed turbine engine is spooled down 

and the dual mode ramjet takes over. Specific questions with regard to inlet/engine interaction:

• What impact does engine inlet distortion have on performance and operability? 

• Can design and analysis tools predict distortion into engine both with and without bleed?

• Can these tools predict the impact of distortion on engine performance and operability? 

• What is the trade-off between bleed and inlet exit profile? Are vortex generators required?

Propulsion Mode Transition

Validated design and analysis tools are necessary to model the TBCC propulsion system 

characteristics over the wide flight range and during mode transition. This requires addressing specific 

questions with regard to understanding and demonstrating mode transition:

• What is the process for safe and optimum mode transition?

• Can design and analysis tools properly model components adequately to perform a controlled 

mode transition?

• Are these predictions of sufficiently high fidelity to guide the testing and avoid inlet unstart 

and/or engine stall?

• Can these design tools be effectively used to extrapolate the experimental data in order to 

optimize the propulsion system configuration?

Throughout the CCE LIMX testing, this model will be used as a testbed to assess the state-of-the-art 

of performance and design codes/tools, inclusive of fluid and turbine performance codes and engineeringlevel algorithms. During this activity integrated system design and analysis tools, as well as dynamic 

models, are being developed and validated to support the controls design and demonstration of mode 

transition of an over-under TBCC propulsion system. 

CCE LIMX—Testbed for Mode Transition Testing

The CCE LIMX is a dual integrated inlet flowpath designed for mode transition testing, including 

controls and integrated inlet and engine testing. The unique features of the CCE LIMX that are being used 

to develop databases and assess state-of-the-art (SOA) tools are shown in Figure 5. 

There are four phases in the test activity that span approximately 3 years: Phase I: inlet performance 

and operability characterization in which cold pipe and mass flow plugs are used to simulate engine 

backpressures for both the low-speed and high-speed flow paths. Open loop control mode transition 

sequences will also be demonstrated. Phase II: unsteady Inlet dynamic system identification experiments

using the cold pipe and mass flow plugs installed in both flowpaths. This test phase will provide the data 

needed to develop the closed loop propulsion system controller. Phase III: demonstrate closed loop mode 

transition control strategies using the cold pipe and mass flow plugs installed in both flowpaths. Phase IV: 

demonstrate closed loop controlled mode transition strategies with a candidate turbine engine and single 

expansion ramp nozzle (SERN) system incorporated into the low-speed flowpath (see Appendix). As 

currently planned the high-speed flowpath uses the cold pipe and mass flow plugs to simulate the 

ram/scramjet for all four phases.
NASA/TM—2012-217217 7

Figure 5.—Unique features of the CCE LIMX to develop databases and assess SOA tools.

The CCE LIMX has substantial parametric capability; it has a reconfigurable bleed system, variablegeometry flow paths, and accommodates a nominally 12-in. diameter turbine. There are a total of 13 

bleed locations (controlled by 15 cold pipe/mass flow plug assemblies) in the low speed flowpath: five on 

the ramp, three on each of the sidewalls, and two on the cowl. Cold pipe and mass flow plug assemblies 

are used on the low speed and high speed flow paths to measure flowrate and to backpressure the inlet.

The mass flow plugs and cold pipes integrated with the CCE LIMX model are shown in Figure 6.

Additionally, due to the large scale, the inlet model is highly instrumented; therefore, spatially resolved 

distributions and high fidelity data can be obtained. 

The CCE research objectives include:

1. Proof of concept of an over/under split flow inlet for a TBCC propulsion system.

a. Develop an integrated performance and operability database

b. Demonstrate mode transition at large scale.

2. Validate inlet computational fluid dynamic (CFD) code predictions of performance and 

operability for the low-speed and high speed flowpaths.

3. Develop realistic distortion characteristics throughout the mode transition Mach number range 

and assess the impact of this distortion on the turbine engine performance and operability.

4. Use this hardware as a testbed for future mode transition controls research and integrated 

inlet/engine propulsion system studies.

The 10- by 10-ft SWT can operate over a Mach number range of 2 to 3.5 (Ref. 6). The CCE LIMX is 

mounted to the facility strut and the angle of attack can be varied between –15° and 5° by rotating the 

strut about its pivot pin which has a 3 in diameter. By operating the facility at Mach 3.5 and positioning 

the CCE LIMX model at an angle of about –7°, as shown in Figure 7, a Mach 4 test condition is provided 

(which is the design condition); some off-design testing at other Mach numbers will also be conducted.

www.nasa.gov 16

1

2

3

4

5

6

8

9

1. Low-speed Inlet Ramps

2. Sidewall Assembly

3. Bleed System

4. Low-speed Cowl Flap

5. High-speed Cowl Flap

6. Base Plate Assembly

7. Fixed Flowpath Panels

8. Overboard Bypass

9. Low-speed Cold-pipe & 

Backpressure System

10. High-speed Isolator & 

Backpressure System

Major Systems:

10

7

1

2

3

4

5

6

8

9

1. Low-speed Inlet Ramps

2. Sidewall Assembly

3. Bleed System

4. Low-speed Cowl Flap

5. High-speed Cowl Flap

6. Base Plate Assembly

7. Fixed Flowpath Panels

8. Overboard Bypass

9. Low-speed Cold-pipe & 

Backpressure System

10. High-speed Isolator & 

Backpressure System

Major Systems:

10

7

CCE Inlet Integrated Model Description

10x10 SWT Installation

(Test at Mach 2, 2.5, 3.1, 3.5, and 4) Parametric Testing Provides Design Database

 Bleed vs Pressure recovery trades

 Bleed vs Engine inlet distortion trades

 Inlet unstart and recovery

 Inlet Mode Transition 

 CFD assessment to predict above

10x10 TBCC/CCE Testbed : Inlet Characterization & Mode Transition Test: Develops 

Operability, Performance and Control Models

High - speed (DMSJ

Low - speed (Turbine)

High - speed (DMSJ

Low - speed (Turbine)

4

4 5

Testbed Features

 Variable Low Speed Cowl

 Variable High Speed cowl

 Variable Ramp

 Variable Compartmented Bleed 

 Low Speed Mass flow / 

Backpressure Device

 High Speed Mass flow / 

Backpressure Device

 Inlet Performance Instrumentation

 Engine Face: Flow Characteristics
NASA/TM—2012-217217 8

Figure 6.—CCE LIMX mass-flow plug and cold pipe locations.

Figure 7.—CCE LIMX Model orientation in the 10- by 10-ft SWT.

The CCE LIMX development was led by NASA with many partners playing an integral role in the 

design and development. Techland Research, Inc. was the primary contractor for the inlet aerodynamic 

flowpath design (Ref. 5). Alliant Techsystems, Inc. (ATK) had the primary responsibility for the 

mechanical design and integration of the inlet hardware and also provided a candidate scramjet design

which was carried through detailed design. Arctic Slope Regional Corporation (ASRC) also helped with 

mechanical design and were responsible for much of the design and fabrication of the facility hardware 

including the strong back. Metalex, Inc. fabricated the majority of the inlet test rig hardware. Williams 

International is providing the (high Mach) turbine engine via an interagency agreement between NASA 

and the Air Force Research Lab (AFRL) to develop high speed turbine engines. The integrated turbine 

engine nozzle was designed and fabricated by Spiritech, Inc. Boeing, Inc. contributed with CFD 

simulations which helped with test preparations. The collage shown in Figure 8 illustrates the 

contributions of the CCE testbed hardware team.

Model angle, α ≅ - 7°

(Mach 4 simulation)
NASA/TM—2012-217217 9

Figure 8.—CCE Testbed and Mode Transition Team.

Facility Preparation and CCE LIMX Model Installation

CCE LIMX preparations have been underway for over 3 years. Installation of the test article and all 

facility preparations were completed, and Phase I testing commenced March 7, 2011.

Due to the large scale of the test article, its complexity, and the extent of instrumentation, the process 

of carefully installing this test article took place through most of calendar year 2010. The test team took 

the time and care during installation to make certain the flowpath was configured as designed. The inlet 

model was delivered to the 10- by 10-ft SWT facility in January 2010 and mounted into the tunnel by 

February 2010 (Fig. 9(a)). Upon receipt and installation of the hardware, a need to re-work many of the 

seals and make some modifications to the hardware was determined. This subsequently required 

substantial disassembly, rework, and reassembly. During re-work, the model was disassembled, leak 

paths were sealed, and the instrumentation routing was completed. Between March and September 2010 

the model was reassembled, which included the installation of all cold pipe and mass flow plug 

assemblies as shown in Figure 9(b). The forebody pre-compression plate, which is the trapezoidal shaped 

surface shown in Figure 9(c), was then installed onto the facility strut and aligned with the inlet model.

Final instrumentation end-to-end checks, calibration of all moving systems (17 mass flow plugs, two

cowls, ramp, and strut angle) were conducted. The overall integrated systems testing, pre-test checkouts, 

and all required safety and test readiness reviews were completed October 2010 through February 2011; 

testing commenced on March 7, 2011.
NASA/TM—2012-217217 10

(a) 

(b)

(c)

Figure 9.—(a) Model as delivered and subsequently mounted in the facility (Jan. to Feb. 2010). (b) Model 

partly disassembled to work seals and hardware interfaces, instrumentation routing, checked out, and inlet 

model re-assembled (Mar. to Sep. 2010). (c) CCE LIMX installed in the 10- by 10-ft SWT ready for test.
NASA/TM—2012-217217 11

CCE LIMX Testing

Four test phases to address the technical challenges and questions discussed previously are planned 

over the next 3 years. Phase I commenced on March 7, 2011, and is expected to conclude by the end of 

May 2011. Previous studies were used to mitigate risk and guide preparations for these experiments

(Ref. 7). These efforts included CFD analysis (Ref. 8) as well as smaller scale screening tests (Ref. 9)in 

the NASA Glenn 1- by 1-ft supersonic wind tunnel. The small scale test results and the CFD analysis

were used to set initial bleed schedules, assess sensitivity to performance and operability with variable 

geometry (both cowls, and low speed ramp), identify necessary control models (Ref. 10), and to help 

develop the test plan. The CCE LIMX has substantially more parametric capability than the small scale 

test model and is more highly instrumented to provide improved fidelity of results. By using the small 

scale test and computational results, an initial test plan for the Phase I experiment was developed as 

shown in Table I.

TABLE I.—TEST MATRIX FOR THE CCE LIMX INLET CHARACTERIZATION (PHASE I)

Test 

series

Bleed pattern Vortex generator 

configuration

Simulated 

Mach numbers

Notes Planned 

data points

1 A7 Basic 4 Facility and model checkout run 7

2 A7 Basic 4 Configuration a7, testing at lower pressure 165

3 A7 Basic 4 Configuration a7, start of standard testing 204

4 A8 Basic 4 Alternate bleed configuration, a8 204

5 A9 Basic 4 Alternate bleed configuration, a9 204

6 Selected Basic 4 Alternate cowl lip al 204

7 Selected Vg1 4 Alternate vortex generator pattern 204

8 Selected Selected 4 Performance and mode transition 661

9 Selected, reduced bleed Selected 4 Reduced bleed 204

10 Selected Selected 3 Lower (off design) mach number tests 661

11 Selected, reduced bleed Selected 3 Lower (off design) mach number tests 204

12 Selected Selected 3.5 Lower (off design) mach number tests 223

13 Selected Selected 2.5 Lower (off design) mach number tests 223

14 Selected Selected 2 Lower (off design) mach number tests 223

Due to high electrical power usage, testing of the 10- by 10-ft SWT occurs on third shift. At the time 

of the writing of this report 10 nights of testing have been conducted. The 10- by 10-ft SWT is a 

continuous flow facility and substantial data can be obtained in a test period. For any supersonic tunnel, 

model size is a concern due to blockage, or the ability to ‘pass the [tunnel normal] shock’ and start the 

tunnel. Initial testing has first shown that the supersonic tunnel was able to start and operate nominally 

with this large model installed (Refs. 6 and 11). During the second test period a hard facility shutdown (or 

tunnel unstart) was observed, which produced a high pressure load over the model. Because the hardware 

was structurally designed to handle this event, the tunnel unstart did not result in any facility or model 

damage. 

With this experience complete, testing is progressing with substantial research testing has been 

achieved to date. Several hundred data points have been taken and are being analyzed; the first 

configurations for the low speed and the high speed flowpaths have been initially characterized and the 

performance assessed. Access to this data can be obtained through the authors and will be reported out in 

detail in the near future. The results are being compared to pre-test computational solutions and to the 

small scale inlet mode transition experiment (IMX) results previously obtained in 1- by 1-ft SWT. Phase I 

and II testing are planned to be completed during 2011 (expected to conclude August 2011); Phase III in 

2012, and Phase IV in 2013.
NASA/TM—2012-217217 12

Summary and Concluding Remarks

One of the missions of the NASA Aeronautics Research Directorate (ARMD) Fundamental 

Aeronautics Program (FAP) Hypersonics project is to develop air-breathing propulsion technology for 

air-breathing access to space (AAS). The focus of this effort is in developing a two stage to orbit (TSTO) 

turbine based combined cycle (TBCC) propulsion system.

There are many technical challenges involved with the development of a TBCC propulsion system and 

these were discussed in this paper. The TBCC Discipline of the Hypersonics project is pursuing the 

Combined Cycle Engine Large Scale Inlet Mode Transition Experiment (CCE LIMX) to work towards 

answering these questions. This very complex experimental activity will take place over the next three years 

and will be accomplished through 4 distinct phases of testing. Phases I through III use the initial test article 

configuration, which is presently being tested in the NASA Glenn 10- by 10-ft SWT, and includes mass 

flow plug and cold pipe assemblies in both the low speed and high speed flowpaths. For Phase IV, a high 

Mach capable turbine engine and single expansion ramp nozzle (SERN) will be incorporated into the lowspeed flowpath. This engine and nozzle have also been developed as a part of the TBCC discipline activity.

Over the past 3 years the CCE LIMX hardware has been developed, designed, fabricated, installed, 

checked out, and is now being tested in the 10- by 10-ft SWT. Testing commenced on March 7, 2011, and 

to date 10 nights of testing have been conducted. Initial testing has shown that the supersonic tunnel was 

able to easily start and operate nominally with this large model installed, and a hard facility shutdown was 

experienced without any resultant facility or model damage. Already several hundred data points have 

been obtained, since this is a continuous flow facility, and these are being analyzed. Access to the data 

can be obtained through the authors and will be reported out in detail in the near future.

Overall this test activity is providing a highly accurate, refined database on this TBCC design and will 

serve to demonstrate the controlled mode transition which is required by an advanced air-breathing 

propulsion system to enable hypersonic flight. Beyond the four phases of this current study the CCE 

LIMX test hardware/TBCC testbed will be continue to remain available to address future national needs 

in combined cycle propulsion.

References

1. Marburger, John H., et al., “National Aeronautics Research and Development Policy,” National 

Research and Technology Council, December 2006.

2. “Decadal Survey of Civil Aeronautics—Foundations for the Future,” National Academies, June 2006.

3. NIA Report, Boeing Contractor Report, Contract No. 2900-HY04, February 18, 2005.

4. Bilardo V.J., Curran F.M., Hunt J.L., Lovell N.T., Wilhite A.W., McKinney L.E., “The Benefits of 

Hypersonic Airbreathing Launch Systems for Access to Space,” AIAA 2003-5265, 39th

AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Huntsville, AL, 20-23 July 2003

5. Sanders, B. W.; and Weir, L. J.: “Aerodynamic Design of a Dual-Flow Mach 7 Hypersonic Inlet 

System for a Turbine-Based Combined-Cycle Hypersonic Propulsion System,” NASA/CR—2008-

215214, June 2008.

6. Soeder, R.H, Roeder, J.W., Linne, A.A., and Panek, J.W., “User Manual for NASA Glenn 10-by10-

Foot Supersonic Wind Tunnel,” NASA/TM—2004-212697, May 2004.

7. Saunders J.D., Slater J.W., Dippold V., Weir, L.J., Sanders B.W., “Inlet Research Status for a LargeScale Turbine-Based Combined Cycle Engine Testbed”, JANNAF, La Jolla, CA, (Dec. 7-11, 2009).

8. J. W. Slater and J. D. Saunders: CFD Simulation of Hypersonic TBCC Inlet Mode Transition, AIAA2009-7349, 16th AIAA/DLR/DGLR International Space Planes and Hypersonic Systems and 

Technologies Conference, Oct.2009.

9. J. D. Saunders; J. W. Slater; V. Dippold; J. Lee; B. W. Sanders and L. J. Weir: “Inlet Mode Transition 

Screening Test for a Turbine-Based Combined-Cycle Propulsion System,” JANNAF, Boston, MA

(May 13, 2008).
NASA/TM—2012-217217 13

10. Stueber, T.J.; Vrnak, D.R.; Le, D.K.; and Ouzts, P.J.: “Control Activity in Support of NASA TBCC 

Research,” JANNAF, La Jolla, CA (Dec. 7-11, 2009).

11. Liepmann, H.W.; and Roshko, A.: Elements of Gasdynamics, pp. 130-137, John Wiley & Sons, Inc. 

1957.
NASA/TM—2012-217217 14
NASA/TM—2012-217217 15

Appendix—Mach 3 Capable Turbine Development

The CCE LIMX Phase IV task includes removing the cold pipe and mass flow plug assembly from 

the low-speed flowpath and installing a Mach 3 capable turbine engine in its place. In preparation for this 

test a William International WJ38 Turbine Engine has been modified as required for Mach 3 operation.

The engine is currently available and has undergone sea level static (SLS) checkout tests. A final series of 

checkout/acceptance testing is planned with an afterburner and integrated nozzle installed. Figure 10

shows a photo of the WI turbine and the integrated nozzle assembly; this hardware will be delivered to 

NASA at the conclusion of the checkout testing (expected April 2011).

Figure 10.—Williams International High Mach WJ38 turbine engine and integrated nozzle assembly.
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Testing of the NASA Hypersonics Project’s Combined Cycle Engine Large Scale Inlet Mode 

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14. ABSTRACT

Status on an effort to develop Turbine Based Combined Cycle (TBCC) propulsion is described. This propulsion technology can enable 

reliable and reusable space launch systems. TBCC propulsion offers improved performance and safety over rocket propulsion. The potential 

to realize aircraft-like operations and reduced maintenance are additional benefits. Among most the critical TBCC enabling technologies 

are: 1) mode transition from turbine to scramjet propulsion, 2) high Mach turbine engines and 3) TBCC integration. To address these TBCC 

challenges, the effort is centered on a propulsion mode transition experiment and includes analytical research. The test program, the 

Combined-Cycle Engine Large Scale Inlet Mode Transition Experiment (CCE LIMX), was conceived to integrate TBCC propulsion with 

proposed hypersonic vehicles. The goals address: (1) dual inlet operability and performance, (2) mode-transition sequences enabling a 

switch between turbine and scramjet flow paths, and (3) turbine engine transients during transition. Four test phases are planned from which 

a database can be used to both validate design and analysis codes and characterize operability and integration issues for TBCC propulsion. 

In this paper we discuss the research objectives, features of the CCE hardware and test plans, and status of the parametric inlet 

characterization testing which began in 2011. This effort is sponsored by the NASA Fundamental Aeronautics Hypersonics project.

15. SUBJECT TERMS

Turbine engines; Ramjet engines; Scramjet engines; Propulsion 

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