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NASA Stennis Space Center Test Technology Branch Activities 

3rd International Hydrogen Peroxide Propulsion Conference 

November 13 - 15, 2000 

Wanda M. Solano 
National Aeronautics and Space 
Administration 
John C. Stennis Space Center 
Code VA34 Building 8306 
Stennis Space Center, MS 39529-6000 
228-688-2655 

Keywords: NASA, Stennis Space Center, Test Technology, Plume, Radiometry, Acoustic, Data 
Acquisition, Sensors 

Abstract 

This paper provides a short history of NASA Stennis Space Center's Test Technology 
Laboratory and briefly describes the variety of engine test technology activities and 
developmental project initiatives. Theoretical rocket exhaust plume modeling, acoustic 
monitoring and analysis, hand held fire imaging, heat flux radiometry, thermal imaging and 
exhaust plume spectroscopy are all examples of current and past test activities that are briefly 
described. In addition, recent efforts and visions focused on accommodating second, third and 
fourth generation flight vehicle engine test requirements are discussed. 

Introduction 

Stennis Space Center, in Hancock County, Mississippi, is NASA's lead center for rocket 
propulsion testing. The Test Technology Branch, in the Propulsion Test Directorate, facilitates 
rocket engine testing in areas not traditionally supported by the Operations Division or Design 
and Analysis Branch. Recent and past activities include engine performance exhaust plume 
spectroscopy, hydrogen fire detection, imaging and smoke/fog penetration, vehicle design and 
facility protection analysis using heat flux radiometry, thermal imaging to identify hardware 
degradation, acoustic monitoring and analysis for sound pressure level predictions, and 
theoretical rocket exhaust plume prediction modeling. In addition, Test Technology Branch 
engineers, working together with in-house contractors and university faculty, engage in 
developmental efforts intended to address and resolve facility sensor, instrumentation, data 
acquisition and control challenges as they arise. Examples of the Test Technology Branch's 
current developmental projects include investigations into non-intrusive flow measurement, 
automatic signal conditioning and data acquisition, intelligent health monitoring and diagnostics, 
advanced fiber optic sensor technologies, flow-induced vibration analysis techniques, next 
generation accelerometers and implementation of a plume experimentation test-bed. Test 
Technology is also preparing for accommodating next generation flight vehicle engine test 
requirements with future research and development projects that may include alternate thrust 
measurement techniques, real time computer cluster signal processing, emission system design 
upgrades, and atmospheric transmission modeling to name a few. 


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Brief History 

In October 1961 NASA announced its decision to establish a national rocket test site in 
Hancock County, Mississippi [1]. The test facility resides on 13,500 acres of land with a sound 
buffer close to 125,000 acres. The site was officially named Mississippi Test Operations (MTO). 
MTO was designated as the Mississippi Test Facility (MTF) in 1965 where in the following year 
the first Saturn V rocket booster (S-II-T) was tested. In 1970, NASA announced that the Earth 
Resources Laboratory (ERL) will locate at MTF. The center was again re-named in 1974 to the 
National Space Technology Laboratories (NSTL) and one year later conducted the first Space 
Shuttle Main Engine (SSME) test. The Remote Sensing Branch of ERL began the SSME 
Vehicle Health Management (VHM). NSTL was re-named John C. Stennis Space Center by 
executive order of President Ronal Reagan in 1988 and designated the Center of Excellence for 
Large Propulsion System Testing in 1991. The Remote Sensing Brach was relocated under the 
newly established Propulsion Test Directorate. The Remote Sensing Branch was later 
reorganized into the Science and Technology Laboratory (STL) and continued work on the 
Diagnostic Test Bed Facility (DTF) to provide a test bed for development of rocket engine 
exhaust plume diagnostics methodologies and instrumentation [2], The Test Technology Branch 
grew out of STL and is now housed in building 8306. Dr. Bill St. Cyr is Branch Chief. 

Survey of Current and Past Activities 


• Exhaust Plume Spectroscopy 

Custom spectral analysis emission spectroscopy systems have been developed to detect 
minute levels of metallic contaminants indicative of abnormal engine wear. Optical 
Multichannel Analyzer (OMA) based systems have been used since 1989 to acquire Space 
Shuttle Main Engine (SSME) exhaust plume spectral data [2]. Engine performance 
conditions are correlated to specific engine components and materials in the hot-gas path that 
erode into the exhaust plume. Two optical channel analyzers are used with one for atomic 
metals and the other for molecular compounds. With emission spectroscopic techniques the 
collection optics is focused at the mach diamond disk as shown in Figure 1, where supersonic 
flow transitions to subsonic flow. 


Control 



Spectrometer 



AES System Configuration 

Figure 1 


Collection 

Optics 



SSME Nozzle 



Mach 

Diamond 


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An example of a typical plume diagnostic waveform is shown in Figure 2, where 
chromium emission intensity is shown over test time for three separate tests. 



0 100 200 300 400 500 600 700 

TIME FROM E/S (sec) Flg-2 


Figure 2 


Figure 3 shows the instrumentation used for absorption spectroscopy. Absorption 
spectroscopy is also routinely used for SSME engine testing when testing with a diffuser, 
where a mach diamond disk is not present. The limitation on absorption spectroscopy is that 
the element to be measured must be incorporated into the hollow cathode lamp prior to 
taking the test and only the selected wavelength can be detected. 



Figure 3 




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Hydrogen Fire Detection, imaging and Smoke/Fog Penetration 

Liquid hydrogen flames are virtually invisible in daylight because of the cryogenics 
clean-burning chemical makeup. A hydrogen tire plural wavelength flame detector was 
developed in collaboration with Kennedy Space Center (KSC) that discriminates between 
direct and reflected radiation. The device, shown in Figure 4, detects fires in the background 
of other emitted radiation. These instruments have been installed and aie in use at KSC. 



Flare Stack 


For low-cost and mobile fire searching, the 1991 National Fire Protection Association 
(NFPA) handbook recommends throwing dirt into the suspect area or probing the area with a 
com straw broom [3]. The Stennis Space Center Fire Department has replaced NFPA 
methods of hydrogen flame detection with a hand-held fire imager. The imager uses black- 
and-white surveillance-type cameras and operates at near-infrared (NIR) wavelengths of 
light, similar to those used by a television remote control. A comparison of a visual image of 
a hydrogen flame is compared in Figure 5 where the broadband IR camera image is shown on 
the left and the bandpass NIR camera image is shown on the right. The image is clearly 
visible with the NIR camera. The instrument can distinguish between the background images 
and the fire. Used like binoculars, the device has the capability to image an 8-inch flame 
from 50-feet away. 



Broadband IR Camera Bandpass NIR Camera 


Figure 5 


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A compact helmet-mounted imaging system coupled with heads-up display (HUD), as shown in 
Figure 6, has been conceptualized and is in development at Stennis Space Center (SSC) [4]. 



HUD Layout 

Figure 6 

The development was specifically designed to provide firefighters and emergency 
response personnel with the ability to work more efficiently in adverse conditions of heavy 
smoke, fog and darkness. The camera system has the capability to penetrate darkness and see 
through smoke and fog without difficulty. A normal view of a flare stack is shown in Figure 
7, where light smoke completely diminishes the view, while the thermal camera view 
increases visibility considerably. Coupled with the HUD, a user can see the video 
information from the camera super-imposed within the field of view (FOV). The system is 
essentially hands free, thereby allowing personnel to be engaged fully with necessary 
activities. The system does not need any adjustments by the user. 



Normal View Thermal Camera 

Figure 7 


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• Vehicle Design Support Using Heat Flux Radiomotry 

Heat flux radiometry measurements have been used to define facility areas that require 
protection from high heat loads and help to mitigate damage to test articles. For example, 
measurement data has been used to validate CFD prediction computer codes developed to 
identify areas of thermal load on the aft of the X-33 Advanced Technology Demonstrator 
flight vehicle. Figure 8a is a view of radiometers that were mounted in the areas around the 
engine that corresponded to specific vehicle aft locations. Also shown in Figure 8b is a 
sample of test data that shows radiation rates for several radiometers over test time, the 
associated chamber pressure and a comparison to the predicted radiation rate. 



Figure 8a 


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Figure 8b 


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• Thermal Imaging 

Thermal imaging is used for engine and engine plume diagnostics. For engine thermal 
imaging, two thermal imagers, with sensitivities from ambient to several thousand degrees 
are used to map 360 degrees ot the test article to show hot spots and other engine thermal 
indications. The images are pseudo color or gray scale and available as integrated area 
temperatures or point measurements. For engine plume thermal imaging, ultra-violet (UV) 
and near-infrared (NIR) cameras are used. These measurements are used to map plume 
boundaries, visualize plume internal flow-fields and indicate combustion stability and other 
plume anomalies. An example is shown in figure 9, where thermal IR imaging (8-14 micron) 
of rocket exhaust plumes is used to show abnormal degradation of injector material. Metal 
material in the gas is visible due to increased emissivity. 



Nozzle Exit 


Mach Diamond 


Figure 9 


• Acoustic Monitoring and Analysis 

Acoustic monitoring and analysis capabilities include facility and test article mid-field 
acoustic monitoring and free field measurement of test acoustic signature and sound pressure 
levels. The acoustic levels generated by large rocket propulsion systems can have significant 
impact not only on the flight vehicle, but also on ground test facilities and personnel. Stennis 
Space Center has undertaken an extensive program to monitor and characterize the acoustic 
signatures of engines undergoing ground test and to support the development and validation 
of predictive models for acoustic emissions. A suite of instrumentation, including precision 
microphones, overpressure sensors, strain gages and signal conditioning and recording 
equipment is available to support both near and far field acoustic measurements. Data 
reduction and analysis programs have been developed that allow detailed analysis of the 
recorded acoustic data, examples of which are shown in Figure 10a & 10b. Data has been 
utilized to predict sound level impact on facility structures, shown in Figure 10c and for 
vehicle design. 


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Strain < ^in/inj 


RtKjkct Engine Icsl 
Building 4010 Strain Data 
John Slcnnts Space Center 



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Time in Sue 

Figure 10a 




Figure 10c 


• Theoretical Rocket Exhaust Plume Modeling 

Rocket plumes have been analyzed using computational fluid dynamic (CFD) techniques. 
The results have been used to design custom flame deflectors, obtain plume-induced 
environment predictions, and predict spectral characteristics for engine health monitoring. 
Figure 1 1 shows an example of how the plume model was generated to determine where the 
mach diamond disk was located in order to position spectroscopic optical collection 
equipment. Also shown is a model of the motor plume impingement on the tarmac and it's 
predicted heating. 


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Figure 1 1 

• SSC Beowulf Cluster and Computational Fluid Dynamics (CFD) Applications 

A Beowulf cluster has been configured at SSC and shown in Figure 12. The cluster has 
been used in a variety of applications: 

• Support plume-induced environment studies to ensure proper flame deflector and 
structural operation. 

• Determine optimum locations for sensors that measure flow properties of rocket exhaust 
plumes. 

• Ensure that NASA/SSC meets EPA guidelines by estimating the amounts of pollutants 
released into the atmosphere by rocket engine tests. 



Figure 12 


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The SSC Beowulf Cluster has the following characteristics: 48 dual Pentium II CPUs, 
400 MHz, Red Hat LINUX 6.0, 19.6GB, Memory, 370 GB Hard Disk Space, 72 ports of 
10Mbps, full duplex network connection. 

Examples of Current Development Efforts 

• Non-Intrusive Flow Measurement 

Fluid flow measurements are an essential part of the engine testing and performance 
evaluations. Non- intrusive flow measurement technology could provide improved and more 
accurate instrumentation for SSC test stands application. A comprehensive study of the flow 
measurement requirements and the current methodology utilized at the SSC test stands is 
being conducted to select the promising technologies for further development for application 
to the SSC engine testing environment. 

• Automatic Signal Conditioning and Data Acquisition 

The propulsion test environment shares many features in common with the data 
acquisition requirements of industries including manufacturing and process control. Of 
continuing interest are those techniques that can help reduce the personnel costs needed to 
reconfigure systems to fix problems and meet new requirements. Another critical need is 
improvements in the quality and reliability of measurements — i.e., monitoring the health of 
the data acquisition system. The universal signal conditioning amplifier (USCA) developed 
at Kennedy Space Center (KSC) [6] is being evaluated for adaptation to the SSC testing 
infrastructure. The primary focus is to determine system design modifications that would 
provide enhanced flexibility, reduced costs, and include health monitoring. Results should be 
of interest to a variety of data acquisition users. 

• Intelligent Health Monitoring and Diagnostics System 

The IHMDS is based on two key elements: A modeling method to instantiate each sensor 
as a highly autonomous sensor (HAS), and a structure suitable for a network of controllers, 
processes, and sensors to implement sensor fusion at a high-qualitative level [7]. This is 
illustrated in Figure 13. 


High Level Controller 



Figure 13 

The IHMDS focuses on modeling sensors as intelligent (highly autonomous) agents that 
operate as elements of a distributed network of sensors, processes, and controllers. A 


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modeling method will be used to embed into any sensor the ability to extract qualitative 
behaviors from the data it reads. Hence, each sensor will provide a qualitative description in- 
time of the behaviors experienced by the parameter it monitors (e.g. tank pressure step 
change). Even though there are many commercial trending software packages, none is 
capable of describing trends as qualitative behaviors where the key features are shapes of a 
signal, regardless of the values. The ability to extract these qualitative behaviors is a very 
powerful tool for monitoring and diagnosis since it mimics how expert operators perform 
these tasks. With all sensors in a system modeled as highly autonomous, a fusion method at 
a high-qualitative level will be implemented to perform monitoring and diagnostics. A 
figurative view of this is provided in Figure 14. 



VA 


Highly Autonomous Sensor I (HASI) 

Plug-and-Play: Self installation, calibration. 

Knowledge Bases: Sensors, measurand, and environment. 

Interpretation: Extraction of Qualitative Behaviors (intuitive, fast, robust). 
Learning: Evolve, adjust to new conditions and sensor physics status. 
Fusion: with environment sensors at quantitative and qualitative levels 
Communications: fiber-optic, wireless 


Figure 14 


• Fiber Optic Sensors 

Fiber optic sensor technology offers the possibility of low cost, multi point measurement 
of many parameters important in propulsion system ground testing and flight environments. 
These include pressure, temperature, vibration, stress, etc. Existing sensor designs are being 
evaluated for their applicability to propulsion system testing / flight applications and the 
designs modified and tested as needed to meet application specific requirements. For 
example, a distributed fiber optic sensor system is being considered for development for 
propellant tank level measurements. 


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• Flow-Induced Vibration Analysis Capability 

A large amount of propellants at high pressures are required for the rocket engine testing. 
Propellant transfer is done by means of the piping systems. These piping structures are 
subject to flow-induced vibration due to turbulence in the flow or, sometimes, due to 
resonance with some periodicity in the flow, which may itself arise by fluid-structure 
interaction. Also, the structure may be subject to fluidelastic instabilities of different types. 
Fairly significant vibrations have been observed at the test stands during propellant transfers 
on some occasions. Prevention of these occurrences requires a better understanding of the 
problem by means of analytical tools. Analytical tools/insights are being developed to 
identify likely situations where flow-induced vibrations are going to be a significant problem. 

• Next Generation Accelerometers 

Sensors used for data acquisition and control fall loosely into two categories, facility or 
test article. Facility sensors refer to those used in conjunction with the propellant delivery 
and thrust measurement systems. These sensors are generally considered to be an integral 
part of the "test stand" data acquisition and control system. Test article sensors refer to those 
used to monitor the behavior and performance of the engine or device under test. These 
sensors are configured into the resident data acquisition and control system as needed and 
required for each particular engine test program. 

Accelerometer and vibration measurements are often utilized as part of the rocket 
propulsion testing system and can fall into either the facility or test article category 
mentioned previously. They are used in a wide variety of applications such as in support of 
building structural response studies, flow induced vibration RMS measurements, turbo pump 
RPM measurements and other rocket engine testing related applications. In order to 
accommodate the need for a versatile, quickly and easily installed and configurable 
acceleration and vibration measurement device a developmental project was undertaken to 
determine the feasibility of producing a low-cost low-power wireless MEMS -based 
accelerometer system (MEMBAS). The preliminary architecture is shown in Figure 15 [8]. 


ADXL 150/250 
MEMS Sensor 



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• Plume Experimentation Test-Bed 

In a combustion test oriented laboratory, the need for a hot gas source comes up quite 
often. For rocket test applications, this must be a high pressure, high temperature, high 
velocity and reacting source. A Plume Experimentation Test (PET) rocket has been 
developed for these applications. The thruster shown in Figure 16 is built in igniter, injector, 
combustion chamber and nozzle sections and modeled after a thruster used at Penn State [9], 
It is designed for a chamber pressure of 200 psi and a thrust of 50 lbf. It uses gaseous 
oxygen as an oxidizer and gaseous hydrogen as a propellant. Plans are underway to design 
and construct an associated mobile test cell, control and data acquisition system. 



Figure 16 


Funding Avenues 

Technology Transfer Office 

Dual-Use Program 

Small Business Innovative Research (SBIR) Program 
Small Business Technology Transfer (STTR) Program 
Education and University Affairs Office 
Resident Research Associateship Program 
Summer Faculty Fellowship Program 
Graduate Student Researchers Program 
EPSCoR Program 
Stennis Space Center Director 
Center Director’s Discretionary Fund (CDDF) Projects 

Future Research and Development 

Technology is also preparing for accommodating next generation flight vehicle engine 
test requirements with future research and development projects that may include, in addition to 
those already discussed, alternate thrust measurement techniques, real time computer cluster 
signal processing, emission system design upgrades, and atmospheric transmission modeling to 
name a few. 


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Acknowledgments 

The author wishes to thank her colleagues lor their many contributions to the text, 
presentation and review of this paper including Fernando Figueroa, Harvey Smith, Chuck 
Thurman, Dave Van Dyke, Jody Woods, and Skip Wright. 

Points of Contact 

Bill St. Cyr, Ph.D.: NASA Test Technology Branch Chief; 228-688-1134 

Skip Wright; Lockheed Martin Technology & Management Support Supervisor; 228-688-7791 


NASA Engineers: 

• Bob Field, Ph.D.: x3735 

• J. Fernando Figueroa, Ph.D.: x2482 

• Wanda Solano: x2655 

• Peter Sulyma: xl920 

• Chuck Thurman: x7680 


References 

[1] John C. Stennis Space Center History Office, Building 1 100, Room 1002, Stennis Space 
Center, MS 39529-6000, (228) 688-2643. http://www.ssc.nasa.gov/about/history/ 

[2] G.D. Tejwani, D.B. Van Dyke, F.E. Bircher, D.G. Gardner and D.J. Chenevert, "Emission 
Spectra of Selected SSME Elements and Materials", NASA Reference Publication 1286, 
December 1992 

[3] NASA’s Commercial Technology Program Target of Opportunity Report, Code TAOO, 
Stennis Space Center, MS 39529-6000, (228) 688-1929, http://technology.ssc. nasa.gov 

[4] H. S. Smith, "Helmet Mounted Fog/Smoke Camera Penetrating System with Heads-Up 
Display", Final Report, Lockheed Martin Stennis Operations, Stennis Space Center, MS 
39529-6000, March 1999 

[5] J. Woods and J. West, "Construction and Utilization of a Beowulf Cluster: A User’s 
Perspective", Preliminary NASA Publication, Lockheed Martin Stennis Operations, Stennis 
Space Center, MS 39529-6000, Nov 2000. 

[6] D. Becker, J. Cedil, C. Halberg and P. Medelius. "The Universal Signal Conditioning 
Amplifier", Proc. ITC, vol. 30, pp. 626-33, 1994. 

[7 1 F. Figueroa. S. Griffin, L. Roemer, and J. Schmalzel, "A Look into the Future of Data 
Acquisition", IEEE Instrumentation & Measurement Magazine, December 1999. 

[8] Analog Devices, Inc. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, 
(617) 329-4700. www.analog.com 

[9) M.D. Moser. "Flowfield Characterization in a Uni-element Rocket Chamber", Ph.D. thesis, 
Pennsylvania State University Graduate School. May 1995. 


Wanda Solano 


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Acknowledgments 

The author wishes to thank her colleagues for their many contributions to the text, 
presentation and review of this paper including Fernando Figueroa, Harvey Smith, Chuck 
Thurman, Dave Van Dyke, Jody Woods, and Skip Wright. 

Points of Contact 

Bill St. Cyr, Ph.D.: NASA Test Technology Branch Chief; 228-688-1134 

Skip Wright: Lockheed Martin Technology & Management Support Supervisor; 228-688-7791 


NASA Engineers: 

• Bob Field, Ph.D.: x3735 

• J. Fernando Figueroa, Ph.D.: x2482 

• Wanda Solano: x2655 

• Peter Sulyma: xl920 

• Chuck Thurman: x7680 


[1] John C. Stennis Space Center History Office, Building 1 100, Room 1002, Stennis Space 
Center, MS 39529-6000, (228) 688-2643. http://www.ssc.nasa.go v/abOut/history/ 

[2] G.D. Tejwani, D.B. Van Dyke, F.E. Bircher, D.G. Gardner and D.J. Chenevert, Emission 
Spectra of Selected SSME Elements and Materials", NASA Reference Publication 1286, 
December 1992 

[3] NASA’s Commercial Technology Program Target of Opportunity Report, Code TA00, 
Stennis Space Center, MS 39529-6000, (228) 688-1929, http://technolo gy.ssc.nasa.goy 

[4] H. S. Smith, "Helmet Mounted Fog/Smoke Camera Penetrating System with Heads-Up 
Display", Final Report, Lockheed Martin Stennis Operations, Stennis Space Center, MS 
39529-6000, March 1999 

[5] J. Woods and J. West, "Construction and Utilization of a Beowulf Cluster: A User’s 
Perspective", Preliminary NASA Publication, Lockheed Martin Stennis Operations, Stennis 
Space Center, MS 39529-6000, Nov 2000. 

[6] D. Becker, J. Cedil, C. Halberg and P. Medelius, "The Universal Signal Conditioning 
Amplifier", Proc. ITC, vol. 30, pp. 626-33, 1994. 

[7] F. Figueroa, S. Griffin, L. Roemer, and J. Schmalzel, "A Look into the Future of Data 
Acquisition", IEEE Instrumentation & Measurement Magazine, December 1999. 

[8] Analog Devices, Inc. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, 
(617) ^Q-4700. www.analog.com 

[9] M.D. Moser, "Flowfield Characterization in a Uni-element Rocket Chamber", Ph.D. thesis, 
Pennsylvania State University Graduate School, May 1995. 


Wanda Solano 


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