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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Nuclear Thermal Propulsion

Development efforts in the United States for nuclear thermal propulsion (NTP) systems began with Project Rover (1955-1973) which completed 22 high-power rocket reactor tests. Results indicated that an NTP system with a high thrust-to-weight ratio and a specific impulse greater than 900 s would be feasible. John F. Kennedy, in his historic special address to Congress on the importance of Space on May 25, 1961, said, "First, I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth..." This was accomplished. He also said, "Secondly ... accelerate development of the Rover nuclear rocket. This gives promise of someday providing a means for even more exciting and ambitious exploration of space... to the very end of the solar system itself." The current NTP project focuses on demonstrating the affordability and viability of a fully integrated NTP system with emphasis on fuel fabrication and testing and an affordable development and qualification strategy. The goal is to enable NTP to be considered a mainstream option for supporting human Mars and other missions beyond Earth orbit.

Mitchell, Sonny↗
NASA NTRS2018

Demonstration of Subscale Cermet Fuel Specimen Fabrication Approach Using Spark Plasma Sintering and Diffusion Bonding

Nuclear thermal propulsion (NTP) has the potential to expand the limits of human space exploration by enabling crewed missions to Mars and beyond. The viability of NTP hinges on the development of a robust nuclear fuel material that can perform in the harsh operating environment (> or = 2500K, reactive hydrogen) of a nuclear thermal rocket (NTR) engine. Efforts are ongoing to develop fuel material and to assemble fuel elements that will be stable during the service life of an NTR. Ceramic-metal (cermet) fuels are being actively pursued by NASA Marshall Space Flight Center (MSFC) due to their demonstrated high-temperature stability and hydrogen compatibility. Building on past cermet fuel development research, experiments were conducted to investigate a modern fabrication approach for cermet fuel elements. The experiments used consolidated tungsten (W)-60vol%zirconia (ZrO2) compacts that were formed via spark plasma sintering (SPS). The consolidated compacts were stacked and diffusion bonded to assess the integrity of the bond lines and internal cooling channel cladding. The assessment included hot hydrogen testing of the manufactured surrogate fuel and pure W for 45 minutes at 2500 K in the compact fuel element environmental test (CFEET) system. Performance of bonded W-ZrO2 rods was compared to bonded pure W rods to access bond line integrity and composite stability. Bonded surrogate fuels retained structural integrity throughout testing and incurred minimal mass loss.

Barnes, Marvin W.↗
NASA NTRS2002

Effects of Fuel Distribution on Detonation Tube Performance

A pulse detonation engine (PDE) uses a series of high frequency intermittent detonation tubes to generate thrust. The process of filling the detonation tube with fuel and air for each cycle may yield non-uniform mixtures. Lack of mixture uniformity is commonly ignored when calculating detonation tube thrust performance. In this study, detonation cycles featuring idealized non-uniform H2/air mixtures were analyzed using the SPARK two-dimensional Navier-Stokes CFD code with 7-step H2/air reaction mechanism. Mixture non-uniformities examined included axial equivalence ratio gradients, transverse equivalence ratio gradients, and partially fueled tubes. Three different average test section equivalence ratios (phi), stoichiometric (phi = 1.00), fuel lean (phi = 0.90), and fuel rich (phi = 1.10), were studied. All mixtures were detonable throughout the detonation tube. It was found that various mixtures representing the same test section equivalence ratio had specific impulses within 1 percent of each other, indicating that good fuel/air mixing is not a prerequisite for optimal detonation tube performance.

Perkins, Hugh Douglas↗
NASA NTRS1993

Evaluation of scramjet nozzle configurations and film cooling for reduction of wall heating

Experiments on relaminarization, or reverse transition of turbulent flow, have been conducted with a scramjet combustor and nozzle model. The Mach-2.7 direct-connect scramjet combustor employed swept-ramp fuel injectors, and the entering flow simulated Mach-6 to Mach-7 flight conditions. Tests were also conducted without combustor fuel to produce a higher nozzle entrance Mach number and lower pressures. Additional tests were conducted to evaluate the effectiveness of film cooling on the cowl region. At each test condition studied, the entrance radius had no significant effect on the measured downstream wall heating rates. Analysis of the data when fuel was injected into the combustor shows good agreement with turbulent theory; for the tests without fuel injection and combustion, the data downstream of the nozzle entrance radius are intermediate to the calculated turbulent and laminar solutions. Results of film-cooling tests, conducted with both hydrogen and nitrogen injectants, showed that, per unit mass, the hydrogen was approximately three to four times more effective than nitrogen in reducing the downstream wall heating rates.

Baker, N. R.↗
NASA NTRS1974

Composition surveys of test gas produced by a hydrogen-oxygen-air burner

As a result of the need for a uniform hot gas test stream for fuel injector development for hydrogen fueled supersonic combustion ramjet engines, an experimental study of injector configuration effect on exit flow uniformity of a hydrogen fueled oxygen replenished, combustion burner was made. Measurements used to investigate the burner nozzle exit profiles were pitot and gas sample measurements. Gas composition and associated temperature profiles were reduced to an acceptable level by burner injector modifications. The effect of the injector modifications was to redistribute the hydrogen fuel, increase the air pressure drop, promote premixing of the oxygen and air, and establish a uniform flow pattern where the oxygen-air mixture comes into contact with the hydrogen fuel. The most sensitive phenomenon which affected the composition profiles was the uniformity of the air distribution supplied to the combustion chamber.

Eggers, J. M.↗
NASA NTRS1981

Catalytic combustion with incompletely vaporized residual fuel

Catalytic combustion of fuel lean mixtures of incompletely vaporized residual fuel and air was investigated. The 7.6 cm diameter, graded cell reactor was constructed from zirconia spinel substrate and catalyzed with a noble metal catalyst. Streams of luminous particles exited the rector as a result of fuel deposition and carbonization on the substrate. Similar results were obtained with blends of No. 6 and No. 2 oil. Blends of shale residual oil and No. 2 oil resulted in stable operation. In shale oil blends the combustor performance degraded with a reduced degree of fuel vaporization. In tests performed with No. 2 oil a similar effect was observed.

Rosfjord, T. J.↗
NASA NTRS1982

Measurement of the spatial dependence of temperature and gas and soot concentrations within large open hydrocarbon fuel fires

A series of large-scale JP-4 fuel pool fire tests was conducted to refine existing mathematical models of large fires. Seven tests were conducted to make chemical concentration and temperature measurements in 7.5 and 15 meter-diameter pool fires. Measurements were made at heights of 0.7, 1.4, 2.9, 5.7, 11.4, and 21.3 meters above the fires. Temperatures were measured at up to 50 locations each second during the fires. Chemistry samples were taken at up to 23 locations within the fires and analyzed for combustion chemistry and soot concentration. Temperature and combustion chemistry profiles obtained during two 7.5 meter-diameter and two 15 meter-diameter fires are included.

Johnson, H. T.↗
NASA NTRS1982

Attitude and translation control of a low-altitude Gravsat

Dynamic simulation of the Gravsat's attitude and translation control system is used to provide an upper bound for the fuel supply and test the feasibility of the preliminary design. A preliminary design is made for the disturbance compensation system (DISCOS) sensor, the thruster control laws, reaction wheel control laws, and the onboard state estimators. The sensor analysis and noise measurements show no problems in scaling the Triad navigation satellite sensor design up to meet the Gravsat requirements, except for proof mass center-of-mass offset. A promising technique is proposed to measure and eliminate this error. The covariance analysis confirms that a sophisticated post-flight data fit will be necessary to reconstruct a scientifically useful proof mass state. The DISCOS sensor will have to be continuously calibrated from the inflight data to achieve this reconstruction.

Ray, J. C.↗
NASA NTRS1982

Effects of simulated lightning on composite and metallic joints

The effects of simulated lightning strikes and currents on aircraft bonded joints and access/inspection panels were investigated. Both metallic and composite specimens were tested. Tests on metal fuel feed through elbows in graphite/epoxy structures were evaluated. Sparking threshold and residual strength of single lap bonded joints and sparking threshold of access/inspection panels and metal fuel feed through elbows are reported.

Howell, W. E.↗