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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Effect of Nozzle Nonlinearities upon Nonlinear Stability of Liquid Propellant Rocket Motors

A three dimensional, nonlinear nozzle admittance relation is developed by solving the wave equation describing finite amplitude oscillatory flow inside the subsonic portion of a choked, slowly convergent axisymmetric nozzle. This nonlinear nozzle admittance relation is then used as a boundary condition in the analysis of nonlinear combustion instability in a cylindrical liquid rocket combustor. In both nozzle and chamber analyses solutions are obtained using the Galerkin method with a series expansion consisting of the first tangential, second tangential, and first radial modes. Using Crocco's time lag model to describe the distributed unsteady combustion process, combustion instability calculations are presented for different values of the following parameters: (1) time lag, (2) interaction index, (3) steady-state Mach number at the nozzle entrance, and (4) chamber length-to-diameter ratio. In each case, limit cycle pressure amplitudes and waveforms are shown for both linear and nonlinear nozzle admittance conditions. These results show that when the amplitudes of the second tangential and first radial modes are considerably smaller than the amplitude of the first tangential mode the inclusion of nozzle nonlinearities has no significant effect on the limiting amplitude and pressure waveforms.

Padmanabhan, M. S.↗
NASA NTRS1991

Fiber optics in liquid propellant rocket engine environments

Fiber optics have recently been seen to offer several major benefits in liquid-fuel rocket engine applications. Fiber-optic sensors can provide measurements that cannot be made with conventional techniques. Fiber optics also can reduce harness weight, provide lightning immunity, and increase frequency response. This paper discusses the results of feasibility testing optical fibers in simulated liquid-fuel rocket engine environments. The environments included cryogenic and high temperatures, and high vibration levels.

Delcher, R.↗
NASA NTRS1959

Materials Problems in Chemical Liquid-Propellant Rocket Systems

With the advent of the space age, new adjustments in technical thinking and engineering experience are necessary. There is an increasing and extensive interest in the utilization of materials for components to be used at temperatures ranging from -423 to over 3500 deg F. This paper presents a description of the materials problems associated with the various components of chemical liquid rocket systems. These components include cooled and uncooled thrust chambers, injectors, turbine drive systems, propellant tanks, and cryogenic propellant containers. In addition to materials limitations associated with these components, suggested research approaches for improving materials properties are made. Materials such as high-temperature alloys, cermets, carbides, nonferrous alloys, plastics, refractory metals, and porous materials are considered.

Gilbert, L. L.↗
NASA NTRS1991

Launch vehicle performance using metallized propellants

Metallized propellant propulsion systems are considered as replacements for the solid rocket boosters and liquid sustainer stages on the current launch vehicles: both the Space Transportation System (STS) and the Titan 4. Liquid rocket boosters for the STS were analyzed as replacements for current solid rocket boosters. These boosters can provide a liquid propulsion system within the volume constraints of a solid rocket booster. A replacement for the Space Shuttle Main Engines using metallized O2/H2/Al was studied. The liquid stages of the Titan 4 were also investigated; the Aerozine-50 (A-50) fuel was replaced with metallized storable A-50/Al. A metallized propellant is similar to a traditional liquid propellant. However, it has metal particles, such as aluminum, that are suspended in a gelled fuel, such as hydrogen, RP-1, A-50 or monomethyl hydrazine (MMH). The fuels then undergo combustion with liquid oxygen or nitrogen tetroxide (NTO). These propellants provide options for increasing the performance of existing launch vehicle chemical propulsion systems by increasing fuel density or specific impulse or both. These increases in density and specific impulse can significantly reduce the propulsion system liftoff weight and allow a liquid rocket booster to fit into the same volume as an existing solid rocket booster. Also, because gelled fuels are akin to liquid propellants, metallized systems can provide enhanced controllability over solid propulsion systems. Gelling of the propellant also reduces the sensitivity to impacts and consequently reduces the propellant explosion hazard.

Palaszewski, Bryan A.↗
NASA NTRS1991

Launch vehicle performance using metallized propellants

Metallized propellant propulsion systems are considered as replacements for the solid rocket boosters and liquid sustainer stages on the current launch vehicles: both the Space Transportation System (STS) and the Titan 4. Liquid rocket boosters for the STS were analyzed as replacements for current solid rocket boosters. These boosters can provide a liquid propulsion system within the volume constraints of a solid rocket booster. A replacement for the Space Shuttle Main Engines using metallized 02/H2/A1 was studied. The liquid stages of the Titan 4 were also investigated; the Aerozine-50 (A-50) fuel was replaced with metallized storable A-50/A1. A metallized propellant is similar to a traditional liquid propellant. However, it has metal particles, such as aluminum, that are suspended in a gelled fuel, such as hydrogen, RP-1, A-50 or monomethyl hydrazine (MMH). The fuels then undergo combustion with liquid oxygen or nitrogen tetroxide (NTO). These propellants provide options for increasing the performance of existing launch vehicle chemical propulsion systems by increasing fuel density or specific impulse or both. These increases in density and specific impulse can significantly reduce the propulsion system liftoff weight and allow a liquid rocket booster to fit into the same volume as an existing solid rocket booster. Also, because gelled fuels are akin to liquid propellants, metallized systems can provide enhanced controllability over solid propulsion systems. Gelling of the propellant also reduces the sensitivity to impacts and consequently reduces the propellant explosion hazard.

Palaszewski, Bryan↗
NASA NTRS2004

Nonlinear Longitudinal Mode Instability in Liquid Propellant Rocket Engine Preburners

Nonlinear pressure oscillations have been observed in liquid propellant rocket instability preburner devices. Unlike the familiar transverse mode instabilities that characterize primary combustion chambers, these oscillations appear as longitudinal gas motions with frequencies that are typical of the chamber axial acoustic modes. In several respects, the phenomenon is similar to longitudinal mode combustion instability appearing in low-smoke solid propellant motors. An important feature is evidence of steep-fronted wave motions with very high amplitude. Clearly, gas motions of this type threaten the mechanical integrity of associated engine components and create unacceptably high vibration levels. This paper focuses on development of the analytical tools needed to predict, diagnose, and correct instabilities of this type. For this purpose, mechanisms that lead to steep-fronted, high-amplitude pressure waves are described in detail. It is shown that such gas motions are the outcome of the natural steepening process in which initially low amplitude standing acoustic waves grow into shock-like disturbances. The energy source that promotes this behavior is a combination of unsteady combustion energy release and interactions with the quasi-steady mean chamber flow. Since shock waves characterize the gas motions, detonation-like mechanisms may well control the unsteady combustion processes. When the energy gains exceed the losses (represented mainly by nozzle and viscous damping), the waves can rapidly grow to a finite amplitude limit cycle. Analytical tools are described that allow the prediction of the limit cycle amplitude and show the dependence of this wave amplitude on the system geometry and other design parameters. This information can be used to guide corrective procedures that mitigate or eliminate the oscillations.

Sims, J. D.↗
NASA NTRS1992

Combustion instability analysis for liquid propellant rocket engines

The multi-dimensional numerical model has been developed to analyze the nonlinear combustion instabilities in liquid-fueled engines. The present pressure-based approach can handle the implicit pressure-velocity coupling in a non-iterative way. The additional scalar conservation equations for the chemical species, the energy, and the turbulent transport quantities can be handled by the same predictor-corrector sequences. This method is time-accurate and it can be applicable to the all-speed, transient, multi-phase, and reacting flows. Special emphasis is given to the acoustic/vaporization interaction which may act as the crucial rate-controlling mechanism in the liquid-fueled rocket engines. The subcritical vaporization is modeled to account for the effects of variable thermophysical properties, non-unitary Lewis number in the gas-film, the Stefan flow effect, and the effect of transient liquid heating. The test cases include the one-dimenisonal fast transient non-reacting and reacting flows, and the multi-dimensional combustion instabilities encountered in the liquid-fueled rocket thrust chamber. The present numerical model successfully demonstrated the capability to simulate the fast transient spray-combusting flows in terms of the limiting-cycle amplitude phenomena, correspondence between combustion and acoustics, and the steep-fronted wave and flame propagation. The investigated parameters include the spray initial conditions, air-fuel mixture ratios, and the engine geometry. Stable and unstable operating conditions are found for the liquid-fueled combustors. Under certain conditions, the limiting cycle behavior of the combusting flowfields is obtained. The numerical results indicate that the spray vaporization processes play an important role in releasing thermal energy and driving the combustion instability.

Kim, Y. M.↗
NASA NTRS2013

US Rocket Propulsion Industrial Base Health Metrics

The number of active liquid rocket engine and solid rocket motor development programs has severely declined since the "space race" of the 1950s and 1960s center dot This downward trend has been exacerbated by the retirement of the Space Shuttle, transition from the Constellation Program to the Space launch System (SLS) and similar activity in DoD programs center dot In addition with consolidation in the industry, the rocket propulsion industrial base is under stress. To Improve the "health" of the RPIB, we need to understand - The current condition of the RPIB - How this compares to past history - The trend of RPIB health center dot This drives the need for a concise set of "metrics" - Analogous to the basic data a physician uses to determine the state of health of his patients - Easy to measure and collect - The trend is often more useful than the actual data point - Can be used to focus on problem areas and develop preventative measures The nation's capability to conceive, design, develop, manufacture, test, and support missions using liquid rocket engines and solid rocket motors that are critical to its national security, economic health and growth, and future scientific needs. center dot The RPIB encompasses US government, academic, and commercial (including industry primes and their supplier base) research, development, test, evaluation, and manufacturing capabilities and facilities. center dot The RPIB includes the skilled workforce, related intellectual property, engineering and support services, and supply chain operations and management. This definition touches the five main segments of the U.S. RPIB as categorized by the USG: defense, intelligence community, civil government, academia, and commercial sector. The nation's capability to conceive, design, develop, manufacture, test, and support missions using liquid rocket engines and solid rocket motors that are critical to its national security, economic health and growth, and future scientific needs. center dot The RPIB encompasses US government, academic, and commercial (including industry primes and their supplier base) research, development, test, evaluation, and manufacturing capabilities and facilities. center dot The RPIB includes the skilled workforce, related intellectual property, engineering and support services, and supply chain operations and management. This definition touches the five main segments of the U.S. RPIB as categorized by the USG: defense, intelligence community, civil government, academia, and commercial sector.

Doreswamy, Rajiv↗