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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

A multidomain and multidimensional numerical analysis of flow in fuelside preburner, high pressure turbine, hot gas manifold and main injector assembly of the Space Shuttle main engine

The Space Shuttle Main Engine (SSME) consists of a large number of critical components each serving a special purpose. Any design change in one of these components not only alters its performance but also the performance of the ones in the upstream and in the downstream. To evaluate the effects of such a design change on the flow fields and on SSME's overall performance a multidomain and multidimensional analytical procedure has been developed and applied here to the series of components on the fuel side of the SSME. The results obtained from the multidomain analysis and their comparison with the single-domain solution when the SSME is operating at Full Power Load indicates that the multidomain model shows greater realism. It is concluded that this modeling technique would assist the designer significantly to achieve still higher performance levels of the SSME.

Mukerjee, T.↗
NASA NTRS1997

Sample Delivery and Computer Control Systems for Detecting Leaks in the Main Engines of the Space Shuttle

The main engines of the Space Shuttle use hydrogen and oxygen as the fuel and oxidant. The explosive and fire hazards associated with these two components pose a serious danger to personnel and equipment. Therefore prior to use the main engines undergo extensive leak tests. Instead of using hazardous gases there tests utilize helium as the tracer element. This results in a need to monitor helium in the ppm level continuously for hours. The major challenge in developing such a low level gas monitor is the sample delivery system. This paper discuss a system developed to meet the requirements while also being mobile. Also shown is the calibration technique, stability, and accuracy results for the system.

Griffin, Timothy P.↗
NASA NTRS2011

Space Shuttle Main Engine - The Relentless Pursuit of Improvement

The Space Shuttle Main Engine (SSME) is the only reusable large liquid rocket engine ever developed. The specific impulse delivered by the staged combustion cycle, substantially higher than previous rocket engines, minimized volume and weight for the integrated vehicle. The dual pre-burner configuration permitted precise mixture ratio and thrust control while the fully redundant controller and avionics provided a very high degree of system reliability and health diagnosis. The main engine controller design was the first rocket engine application to incorporate digital processing. The engine was required to operate at a high chamber pressure to minimize engine volume and weight. Power level throttling was required to minimize structural loads on the vehicle early in flight and acceleration levels on the crew late in ascent. Fatigue capability, strength, ease of assembly and disassembly, inspectability, and materials compatibility were all major considerations in achieving a fully reusable design. During the multi-decade program the design evolved substantially using a series of block upgrades. A number of materials and manufacturing challenges were encountered throughout SSME s history. Significant development was required for the final configuration of the high pressure turbopumps. Fracture control was implemented to assess life limits of critical materials and components. Survival in the hydrogen environment required assessment of hydrogen embrittlement. Instrumentation systems were a challenge due to the harsh thermal and dynamic environments within the engine. Extensive inspection procedures were developed to assess the engine components between flights. The Space Shuttle Main Engine achieved a remarkable flight performance record. All flights were successful with only one mission requiring an ascent abort condition, which still resulted in an acceptable orbit and mission. This was achieved in large part via extensive ground testing to fully characterize performance and to establish acceptable life limits. During the program over a million seconds of accumulated test and flight time was achieved. Post flight inspection and assessment was a key part of assuring proper performance of the flight hardware. By the end of the program the predicted reliability had improved by a factor of four. These unique challenges, evolution of the design, and the resulting reliability will be discussed in this paper.

VanHooser, Katherine P.↗
NASA NTRS1980

Space Shuttle Main Engine development /May 1980/

The Space Shuttle Main Engine is the most advanced liquid propellant rocket engine ever developed. During the last year, significant progess has been made toward the identification and solution of several design weaknesses. The initial two test series to certify the engine's readiness for manned flight have been completed, and additional test series are in progress. Operation of the total propulsion system has been demonstrated by a successful series of flight-simulation tests using the three-engine cluster Main Propulsion Test Article. The first set of flight engines has been acceptance tested for use in Shuttle Orbiter 102 (Columbia) for the first manned orbital flight in late 1980 or early 1981. Engine development is continuing with initial demonstrations of full-power level (109%) operation capability.

Sanchini, D. J.↗
NASA NTRS2014

Combustion Stability Characteristics of the Project Morpheus Liquid Oxygen / Liquid Methane Main Engine

The project Morpheus liquid oxygen (LOX) / liquid methane (LCH4) main engine is a Johnson Space Center (JSC) designed ~5,000 lbf-thrust, 4:1 throttling, pressure-fed cryogenic engine using an impinging element injector design. The engine met or exceeded all performance requirements without experiencing any in- ight failures, but the engine exhibited acoustic-coupled combustion instabilities during sea-level ground-based testing. First tangential (1T), rst radial (1R), 1T1R, and higher order modes were triggered by conditions during the Morpheus vehicle derived low chamber pressure startup sequence. The instability was never observed to initiate during mainstage, even at low power levels. Ground-interaction acoustics aggravated the instability in vehicle tests. Analysis of more than 200 hot re tests on the Morpheus vehicle and Stennis Space Center (SSC) test stand showed a relationship between ignition stability and injector/chamber pressure. The instability had the distinct characteristic of initiating at high relative injection pressure drop at low chamber pressure during the start sequence. Data analysis suggests that the two-phase density during engine start results in a high injection velocity, possibly triggering the instabilities predicted by the Hewitt stability curves. Engine ignition instability was successfully mitigated via a higher-chamber pressure start sequence (e.g., ~50% power level vs ~30%) and operational propellant start temperature limits that maintained \cold LOX" and \warm methane" at the engine inlet. The main engine successfully demonstrated 4:1 throttling without chugging during mainstage, but chug instabilities were observed during some engine shutdown sequences at low injector pressure drop, especially during vehicle landing.

Melcher, John C.↗
NASA NTRS1987

Space Shuttle Main Engine plume spectral monitoring preliminary results

In order to provide the information necessary to develop a rocket engine ground test failure detection monitor which keys on anomalous activity in the plume, a series of experimental observations were made during single engine Space Shuttle Main Engine (SSME) tests. The observations were conducted from the 220 nm wavelength in the ultraviolet out to the 15 micron wavelength in the infrared. Four types of instruments were employed including analog autoranging narrow band radiometers, optical multichannel analyzers, mechanical scanning and film plate spectrometers, and imaging cameras. Some results included: strong OH radiation in the UV up to vibrational transition state four; Na and K radiation lines in all phases of engine operation; reaction of some of the instruments to minor engine anomalies; good shock structure imaging; striations in the flow in the 310 nm OH band; and detection of gross changes in engine operating state such as start or shutdown.

Cikanek, H. A., III↗
NASA NTRS2001

Lubrication of Space Shuttle Main Engine Turbopump Bearings

The Space Shuttle has three main engines that are used for propulsion into orbit. These engines are fed propellants by four turbopumps on each engine. A main element in the turbopump is the bearings supporting the rotor that spins the turbine blades and the pump impeller. These bearings are required to spin at very high speeds, support radial and thrust loads, and have high wear resistance without the benefit of lubrication. The liquid hydrogen and oxygen propellants flow through the bearings to cool the surfaces. The volatile nature of the propellants excludes any conventional means of lubrication. Lubrication for these bearings is provided by the ball separator inside the bearing. The separator is a composite material that supplies a transfer film of lubrication to the rings and balls. New separator materials and lubrication schemes have been investigated at Marshall Space Flight Center in a bearing test rig with promising results. Hybrid bearings with silicon nitride balls have also been evaluated. The use of hybrid, silicon nitride ball bearings in conjunction -with better separator materials has shown excellent results. The work that Marshall has done is being utilized in turbopumps flying on the space shuttle fleet and will be utilized in future space travel. This result of this work is valuable for all aerospace and commercial applications where high-speed bearings are used.

Gibson, Howard↗
NASA NTRS2003

Leak Location and Classification in the Space Shuttle Main Engine Nozzle by Infrared Testing

The Space Shuttle Main Engine (SSME) is composed of cooling tubes brazed to the inside of a conical structural jacket. Because of the geometry there are regions that can't be inspected for leaks using the bubble solution and low-pressure method. The temperature change due escaping gas is detectable on the surface of the nozzle under the correct conditions. The methods and results presented in this summary address the thermographic identification of leaks in the Space Shuttle Main Engine nozzles. A highly sensitive digital infrared camera is used to record the minute temperature change associated with a leak source, such as a crack or pinhole, hidden within the nozzle wall by observing the inner "hot wall" surface as the nozzle is pressurized. These images are enhanced by digitally subtracting a thermal reference image taken before pressurization, greatly diminishing background noise. The method provides a nonintrusive way of localizing the tube that is leaking and the exact leak source position to within a very small axial distance. Many of the factors that influence the inspectability of the nozzle are addressed; including pressure rate, peak pressure, gas type, ambient temperature and surface preparation.

Russell, Samuel S.↗
NASA NTRS1973

Condition monitoring helps make the Space Shuttle Main Engine reusable

The Space Shuttle Main Engine (SSME) is a reusable, high-performance liquid-propellant rocket engine being developed for the Space Shuttle Orbiter Vehicle. The SSME has been designed for long life, rapid postflight maintenance, and a fast vehicle turnaround cycle of 160 hours. To meet the unique reusability requirements, the SSME considers maintainability and condition monitoring much as airlines do today. The condition monitoring capabilities designed into this engine are discussed with major emphasis on internal inspection and techniques which ensure the reusability of the SSME.

Lacroix, W. P.↗
NASA NTRS1995

Predicting engine parameters using the optic spectrum of the space shuttle main engine exhaust plume

The Optical Plume Anomaly Detection (OPAD) system is under development to predict engine anomalies and engine parameters of the Space Shuttle's Main Engine (SSME). The anomaly detection is based on abnormal metal concentrations in the optical spectrum of the rocket plume. Such abnormalities could be indicative of engine corrosion or other malfunctions. Here, we focus on the second task of the OPAD system, namely the prediction of engine parameters such as rated power level (RPL) and mixture ratio (MR). Because of the high dimensionality of the spectrum, we developed a linear algorithm to resolve the optical spectrum of the exhaust plume into a number of separate components, each with a different physical interpretation. These components are used to predict the metal concentrations and engine parameters for online support of ground-level testing of the SSME. Currently, these predictions are labor intensive and cannot be done online. We predict RPL using neural networks and give preliminary results.

Srivastava, Ashok N.↗
NASA NTRS2010

Cassini Main Engine Assembly Cover Flight Management and Performance

The Cassini spacecraft has performed its four year Prime Mission at Saturn and is currently in orbit at Saturn performing a two year extended mission. 12Its main engine nozzles are susceptible to impact damage from micrometeoroids and on-orbit dust. The spacecraft has an articulating device known as the Main Engine Assembly (MEA) cover which can close and shield the main engines from these threats. The cover opens to allow for main engine burns that are necessary to maintain the trajectory. Periodically updated analyses of potential on-orbit dust hazard threats have resulted in the need to continue to use the MEA cover beyond its intended use and beyond its design life. This paper provides a detailed Systems-level overview of the flight management of the MEA cover device and its flight performance to date.

Somawardhana, Ruwan P.↗
NASA NTRS2002

Space Shuttle Main Engine (SSME) Options for the Future Shuttle

The main engines for the Future Shuttle will focus on improved safety and operability. Performance enhancements may also be required for vehicle safety purposes to achieve more desirable abort scenarios. This paper discusses the potential improvements that will be considered for implementation into the Future Shuttle. Integrated engine and vehicle health management systems will achieve additional system-level reliability improvements over those currently in development. Advanced instrumentation for detecting leaks, analyzing component wear and degradation, and providing sophisticated operational data will be used for reliable engine control and scheduling maintenance operations. A new nozzle and main combustion chamber (MCC) will reduce failure probability by 50% and allow for higher thrust capability without requiring the entire engine to be redesigned. Turbopump improvements may range from minor component improvements to using 3rd-generation pumps built on the advanced concepts demonstrated by the Integrated Powerhead Development (IPD) program and the Space Launch Initiative (SLI) prototype engines.The main engines for the Future Shuttle will focus on improved safety and operability. Performance enhancements may also be required for vehicle safety purposes to achieve more desirable abort scenarios. This paper discusses the potential improvements that will be considered for implementation into the Future Shuttle. Integrated engine and vehicle health management systems will achieve additional system-level reliability improvements over those currently in development. Advanced instrumentation for detecting leaks, analyzing component wear and degradation, and providing sophisticated operational data will be used for reliable engine control and scheduling maintenance operations. A new nozzle and main combustion chamber (MCC) will reduce failure probability by 50% and allow for higher thrust capability without requiring the entire engine to be redesigned. Turbopump improvements may range from minor component improvements to using 3rd-generation pumps built on the advanced concepts demonstrated by the Integrated Powerhead Development (IPD) program and the Space Launch Initiative (SLI) prototype engines.

Jue, Fred↗
NASA NTRS1988

Identification and characterization of structural nonlinearities in the Space Shuttle Main Engine

Structural nonlinearities should be considered in the analysis and modeling of mechanical systems for accuracy in predicting dynamic behavior. Moreover, checks for nonlinearity should address the type and class of nonlinearity in the structure and identify the probable cause. A series of experimental modal survey tests were carried out to determine and characterize the structural nonlinearities of the Space Shuttle Main Engine main injector. Different excitation regimes at various amplitudes were utilized to induce vibration and strain, and acceleration measurements were taken at judiciously selected locations. The test results indicated that both stiffness and damping nonlinearities were present.

Panossian, H. V.↗
NASA NTRS1983

Space Shuttle Main Engine /SSME/ - The 'maturing' process

The basic Space Shuttle Main Engine (SSME) concept called for an operational life of 55 missions, as well as an exceptionally high specific impulse. While these requirements are considered achievable in the cases of the basic engine structure, powerhead, main combustion chamber, propellant ducts, hydraulic lines and engine controller, other components may experience excessive wear and deterioration and may not achieve specification life without removal and overhaul. Most SSME components have been designed as line replaceable units, which have demonstrated good operational durability and will meet flight certification requirement upgrading. The Flight Confidence Program of the SSME test program currently being instituted will recertify existing engines for use in more than the 10 flights stipulated until now. The testing of two engines in repeated cycles should add 10 flights for every two successfully completed certification cycles.

Dankhoff, W.↗
NASA NTRS2011

Characterizing Observed Limit Cycles in the Cassini Main Engine Guidance Control System

The Cassini spacecraft dynamics-related telemetry during long Main Engine (ME) burns has indicated the presence of stable limit cycles between 0.03-0.04 Hz frequencies. These stable limit cycles cause the spacecraft to possess non-zero oscillating rates for extended periods of time. This indicates that the linear ME guidance control system does not model the complete dynamics of the spacecraft. In this study, we propose that the observed limit cycles in the spacecraft dynamics telemetry appear from a stable interaction between the unmodeled nonlinear elements in the ME guidance control system. Many nonlinearities in the control system emerge from translating the linear engine gimbal actuator (EGA) motion into a spacecraft rotation. One such nonlinearity comes from the gear backlash in the EGA system, which is the focus of this paper. The limit cycle characteristics and behavior can be predicted by modeling this gear backlash nonlinear element via a describing function and studying the interaction of this describing function with the overall dynamics of the spacecraft. The linear ME guidance controller and gear backlash nonlinearity are modeled analytically. The frequency, magnitude, and nature of the limit cycle are obtained from the frequency response of the ME guidance controller and nonlinear element. In addition, the ME guidance controller along with the nonlinearity is simulated. The simulation response contains a limit cycle with similar characterstics as predicted analytically: 0.03-0.04 Hz frequency and stable, sustained oscillations. The analytical and simulated limit cycle responses are compared to the flight telemetry for long burns such as the Saturn Orbit Insertion and Main Engine Orbit Trim Maneuvers. The analytical and simulated limit cycle characteristics compare well with the actual observed limit cycles in the flight telemetry. Both have frequencies between 0.03-0.04 Hz and stable oscillations. This work shows that the stable limit cycles occur due to the interaction between the unmodeled nonlinear elements and linear ME guidance controller.

stable limit cycle↗
NASA NTRS1981

Space shuttle main engine: Hydraulic system

The hydraulic actuation system of the space shuttle main engine is discussed. The system consists of five electrohydraulic actuators and a single engine filter used to control the five different propellant valves, which in turn control thrust and mixture ratio of the space shuttle main engine. The hydraulic actuation system provides this control with a precision of 98.7 percent or an error in position no greater than 1.3 percent of full scale rotational travel for critical positions.

Geller, G.↗
NASA NTRS1988

3-D thermal analysis using finite difference technique with finite element model for improved design of components of rocket engine turbomachines for Space Shuttle Main Engine SSME

Three-dimensional finite element models were generated and transferred into three-dimensional finite difference models to perform transient thermal analyses for the SSME high pressure fuel turbopump's first stage nozzles and rotor blades. STANCOOL was chosen to calculate the heat transfer characteristics (HTCs) around the airfoils, and endwall effects were included at the intersections of the airfoils and platforms for the steady-state boundary conditions. Free and forced convection due to rotation effects were also considered in hollow cores. Transient HTCs were calculated by taking ratios of the steady-state values based on the flow rates and fluid properties calculated at each time slice. Results are presented for both transient plots and three-dimensional color contour isotherm plots; they were also converted into universal files to be used for FEM stress analyses.

Sohn, Kiho D.↗