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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Low loss injector for Space Shuttle main engine. Center director's discretionary fund

An efficient propellant injection method to raise the Space Shuttle Main Engine (SSME) thrust and payload is discussed. Relatively large diameter injector elements with low pressure loss are recommended for the main combustion chamber and the pre-burners. Smaller losses admit more propellant flow which then raises thrust. Payload is not only gained by specific impulse but also by thrust. The chamber pressure is stabilized by selecting the proper cavity size for the injector elements while reducing the injection pressure loss which normally is kept high for stability. The rather large injector element recesses provide acoustic damping which makes baffles and acoustic absorbers unnecessary. A tenfold reduction of flow induced stresses which are rather high in the present design is shown. Relaxed tolerances, fewer elements, and better maintenance are offered. The study was conducted under a center director discretionary fund assignment.

Vonpragenau, G. L.↗
NASA NTRS2010

Understanding the Space Shuttle Main Engine Hydraulic Actuation System and Reviewing Its Evolution

The complex engine start and thrust control requirements of the Space Shuttle Main Engine (SSME) require unique valve, actuator and control system hardware. The Hydraulic Actuation System (HAS) was designed, developed, and now operates to meet tight engine control requirement limits to assure safe, reliable and correct engine thrust at all times. The actuator is designed to be fail safe and fail operate in the areas where redundancy is important. The HAS has an additional pneumatic operating capability that insures a safe sequential closure of all actuators and propellant valves in the event of the loss of hydraulic system pressure or loss of electrical closed loop control of the actuator. The objective of this paper is to provide a complete description of the actuator s internal operating system, along with its interaction with all SSME system interfaces. Additionally the paper addresses the challenges, problems identified, and corrected, and lessons learned, during the course of the almost 35 years of engine operation.

McWade, Robert J.↗
NASA NTRS1992

Engine systems analysis results of the Space Shuttle Main Engine redesigned powerhead initial engine level testing

Engineers regularly analyze SSME ground test and flight data with respect to engine systems performance. Recently, a redesigned SSME powerhead was introduced to engine-level testing in part to increase engine operational margins through optimization of the engine internal environment. This paper presents an overview of the MSFC personnel engine systems analysis results and conclusions reached from initial engine level testing of the redesigned powerhead, and further redesigns incorporated to eliminate accelerated main injector baffle and main combustion chamber hot gas wall degradation. The conclusions are drawn from instrumented engine ground test data and hardware integrity analysis reports and address initial engine test results with respect to the apparent design change effects on engine system and component operation.

Sander, Erik J.↗
NASA NTRS1995

The Calibrations of Space Shuttle Main Engines High Pressure Transducers

Previously, high pressure transducers that were used on the Space Shuttles Main Engine (SSME) exhibited a severe drift after being tested on the SSME. The Experimental Testing Technology Division (ETTD) designed some new transducers that would not exhibit a severe drift over a short period of time. These transducers were calibrated at the Test Bed at Marshall Space Flight Center (MSFC). After the high pressure transducers were calibrated, the transducers were placed on the SSME and fired. The transducers were then sent to the NASA LaRC to be recalibrated. The main objectives of the recalibrations was to make sure that the transducers possessed the same qualities as they did before they were fired on the SSME. Other objectives of the project were to determine the stability of the transducers and to determine whether the transducers exhibited a severe drift.

Steward, Christopher S.↗
NASA NTRS1980

Mechanism associated with the Space Shuttle main engine oxidizer valve/duct system anomalous high amplitude discrete acoustical excitation

Anomalous high frequency pressure fluctuations in the Space Shuttle main engine have been experienced during hot firings. Through diagnostic analysis of hot firing engine data, it was determined that this excitation originated at the main oxidizer valve. The intensity of these fluctuations was such that the main oxidizer valve was partially consumed in fire, experienced fretting, and had seal damage. Delineated in this paper are the associated dynamical phenomena and the methodologies leading toward understanding the excitation mechanism. The results presented demonstrate that the source of the anomalous frequencies was suppressed by a simple fix and all main oxidizer valve damage was terminated.

Schutzenhofer, L. A.↗
NASA NTRS1981

Space Shuttle main engine progress through the first flight

A system overview is presented for the Space Shuttle Main Engine (SSME), and extensive performance comparisons are made with the Saturn V booster powerplant showing (1) staged-combustion turbopump pressures of 7,500 vs 1,100 psi for the Saturn V first stage; (2) a specific impulse of 455 vs 300; (3) power density of 100 vs 20 hp/lb; and (4) chamber pressures of 3200 vs 1000 psia. An account is then given of the SSME testing program, engine certification process and flight aboard the Space Shuttle Columbia, with attention to anomalies detected during flight in turbopump operation and mixture ratio sensor function.

Johnson, J. R.↗
NASA NTRS1984

Research pressure instrumentation for NASA Space Shuttle main engine, modification no. 5

Research concerning the development of pressure instrumentation for the space shuttle main engine is reported. The following specific topics were addressed: (1) transducer design and materials, (2) silicon piezoresistor characterization at cryogenic temperatures, (3) chip mounting characterization, and (4) frequency response optimization.

Anderson, P. J.↗
NASA NTRS1984

Research pressure instrumentation for NASA Space Shuttle main engine

The development of prototype pressure transducers which are targeted to meet the Space Shuttle Main Engine SSME performance design goals is discussed. The fabrication, testing and delivery of 10 prototype units is examined. Silicon piezoresistive strain sensing technology is used to achieve the objectives of advanced state-of-the-art pressure sensors in terms of reliability, accuracy and ease of manufacture. Integration of multiple functions on a single chip is the key attribute of this technology.

Anderson, P. J.↗
NASA NTRS1985

Research pressure instrumentation for NASA space shuttle main engine

The breadboard feasibility model of a silicon piezoresistive pressure transducer suitable for space shuttle main engine (SSME) applications was demonstrated. The development of pressure instrumentation for the SSME was examined. The objective is to develop prototype pressure transducers which are targeted to meet the SSME performance design goals and to fabricate, test and deliver a total of 10 prototype units. Effective utilization of the many advantages of silicon piezoresistive strain sensing technology to achieve the objectives of advanced state-of-the-art pressure sensors for reliability, accuracy and ease of manufacture is analyzed. Integration of multiple functions on a single chip is the key attribute of the technology.

Anderson, P. J.↗
NASA NTRS1986

Space Shuttle Main Engine fuel preburner augmented spark igniter shutdown detonations

Detonations were experienced in the Space Shuttle Main Engine fuel preburner (FPB) augmented spark igniter (ASI) during engine cutoff. Several of these resulted in over pressures sufficient to damage the FPB ASI oxidizer system. The detonations initiated in the FPB ASI oxidizer line when residual oxidizer (oxygen) in the line mixed with backflowing fuel (hydrogen) and detonated. This paper reviews the damage history to the FPB ASI oxidizer system, an engineering assessment of the problem cause, a verification of the mechanisms, the hazards associated with the detonations, and the solution implemented.

Dexter, C. E.↗
NASA NTRS1986

Testing certifies the Space Shuttle Main Engine life improvement modifications

Development and certification tests have been conducted on the Space Shuttle Main Engine to verify design changes made on the high-pressure turbopumps to expand operating margin at full-power level, increase life, and reduce maintenance requirements. Design changes are summarized and the verification process is described in detail. Methods of testing turbopumps for increased rotor stability, reduced bearing loads, extended bearing and turbine blade life, and reduced turbine operating temperatures are also described. Accomplishments to date in extending both the power level and life of the SSME are summarized.

Wood, Byron K.↗
NASA NTRS1978

Solution of the subsynchronous whirl problem in the high-pressure hydrogen turbomachinery of the Space Shuttle Main Engine

Subsynchronous whirl of the high-pressure fuel turbopump limited operation of the Space Shuttle Main Engine for some months in early 1976. The means by which this problem was successfully attacked is of particular interest to the rotor-dynamics community, not only because this machinery was the highest power-to-weight ratio known (77,000 hp...760 pounds), but because of the multiple forcing functions involved and the means, both analytical and experimental, which were utilized in separating variables, pointing toward successful solutions, and evaluating results. The general means of identifying fundamental characteristics, analyzing data, and conducting computer investigations are delineated. The results of analysis and testing are discussed. Since whirl inception occurs at a shaft speed greater than twice the first system critical, this was increased by stiffening the shaft and bearing supports; the system damping and system stiffness was additionally increased by proper interstage seal design to the extent that the instability threshold is now beyond the operating range.

Ek, M. C.↗
NASA NTRS1980

Rotordynamics analysis of the Space Shuttle main engine high-pressure oxidizer pump

This study describes the rotordynamics analysis of the Space Shuttle Main Engine (SSME) high-pressure oxidizer turbopump. Modal synthesis methods were used to account for the complex coupling of the pump and engine structure. Cross-coupling elements effecting rotor stability were included in the analysis. Results of the analysis indicated that smaller bearing clearances and a smooth turbine interstage seal would result in longer bearing life and improved stability. Subsequent testing with these design features has shown the same results.

Rowan, B. F.↗
NASA NTRS1989

Identification of space shuttle main engine dynamics

System identification techniques are used to represent the dynamic behavior of the Space Shuttle Main Engine. The transfer function matrices of the linearized models of both the closed loop and the open loop system are obtained by using the recursive maximum likelihood method.

Duyar, Ahmet↗
NASA NTRS1989

Identification of Space Shuttle Main Engine dynamics

System identification techniques are used to represent the dynamic behavior of the Space Shuttle Main Engine. The transfer function matrices of the linearized models of both the closed loop and the open loop system are obtained by using the recursive maximum likelihood method.

Duyar, Ahmet↗
NASA NTRS1990

Inductive knowledge acquisition experience with commercial tools for space shuttle main engine testing

Since 1984, an effort has been underway at Rocketdyne, manufacturer of the Space Shuttle Main Engine (SSME), to automate much of the analysis procedure conducted after engine test firings. Previously published articles at national and international conferences have contained the context of and justification for this effort. Here, progress is reported in building the full system, including the extensions of integrating large databases with the system, known as Scotty. Inductive knowledge acquisition has proven itself to be a key factor in the success of Scotty. The combination of a powerful inductive expert system building tool (ExTran), a relational data base management system (Reliance), and software engineering principles and Computer-Assisted Software Engineering (CASE) tools makes for a practical, useful and state-of-the-art application of an expert system.

Modesitt, Kenneth L.↗
NASA NTRS1991

Space transportation main engine cycle assessment process

The Advanced Launch System (ALS) program selection process for a space transportation main engine (STME) power cycle is described in terms of the methodology employed. Low cost, robustness, and high reliability are the primary parameters for engine choice, suggesting simplicity of design and efficient fabrication methods as the crucial characteristics. An evaluation methodology is developed based on the Pugh (1981) process and the King (1989) matrices. The cycle configurations considered are the gas generator (GG), the closed expander, and the open expander. The cycle assessment team determined that the GG cycle is favored by most cycle discriminators, based on an assessment of the characteristics in terms of ALS goals. The lower development risk of the GG-cycle STME is consistent with the goals of the ALS program in terms of reliability and cost efficiency.

Mcconnaughey, H. V.↗