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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Some dynamical design considerations for momentum biased spacecraft

This paper discusses some of the dynamical aspects that affect the attitude behavior of a spacecraft placed in a near earth polar orbit. The parameters such as atmospheric density variation, super-rotation of upper atmosphere, pitch equilibrium angle, and trim boom length selection to reduce pitch axis drift are considered. These parameters are studied with reference to two momentum biased satellities (Magsat and Dynamics Explorer-2) and the analyses are correlated with observed flight data. It is found that the design model of certain parameters has to be improved by including other phenomena so that flight data and the analytical model predictions have good correlations. The effects of mass imbalance on the orbital and nutational modes of the spacecraft attitude are discussed.

Sellappan, R. G.↗
NASA NTRS1983

Modeling stiffness loss in boron/aluminum laminates below the fatigue limit

Boron/aluminum can develop significant internal matrix cracking when fatigued. These matrix cracks can result in a 40 percent secant modulus loss in some laminates, even when fatigued below the fatigue limit. It is shown that the same amount of fatigue damage will develop during stress or strain-controlled tests. Stacking sequence has little influence on secant modulus loss. The secant modulus loss in unidirectional composites is small, whereas the losses are substantial in laminates containing off-axis plies. A simple analysis is presented that predicts unnotched laminate secant modulus loss due to fatigue. The analysis is based upon the elastic modulus and Poisson's ratio of the fiber and matrix, fiber volume fraction, fiber orientations, and the cyclic-hardened yield stress of the matrix material. Excellent agreement was achieved between model predictions and experimental results. With this model, designers can project the material stiffness loss for design load or strain levels and assess the feasibility of its use in stiffness-critical parts. Previously announced in STAR as N82-24298

Johnson, W. S.↗
NASA NTRS1985

Evaluation and prediction of long-term environmental effects of nonmetallic materials

The properties of a number of nonmetallic materials were evaluated experimentally in simulated space environments in order to develop models for accelerated test methods useful for predicting such behavioral changes. Graphite-epoxy composites were exposed to thermal cycling. Adhesive foam tapes were subjected to a vacuum environment. Metal-matrix composites were tested for baseline data. Predictive modeling designed to include strength and aging effects on composites, polymeric films, and metals under such space conditions (including the atomic oxygen environment) is discussed. The Korel 8031-00 high strength adhesive foam tape was shown to be superior to the other two tested.

Papazian, H.↗
NASA NTRS1985

Study of the potential usefulness of superfine holographic x-ray gratings in AXAF and astrophysics in general

Present day high energy electron storage rings and insertion devices (wigglers and undulators) provide the necessary technology to manufacture superfile (line density or=100,00/mm) holographic X-ray gratings. The usefulness in future astrophysical research of such gratings is determined, as a function of the grating size and line density. A model design is given for an instrument which would fit within the (presently specified) constraints of the planned Advanced X-ray Astrophysics Facility (AXAF).

Csonka, P. L.↗
NASA NTRS1985

Rationale for an experimental test for flexible space structure attitude control

The problems of large flexible spacecraft control are characterized by the infinite bandwidth of structural vibrations, which cannot be accounted for in the dynamic design model. This may lead to instability even, if ideal control hardware is assumed, which can be concluded from preceding numerical investigations. Additional performance limitations are expected to occur due to hardware constraints. A laboratory experiment is proposed to investigate the key problems in more detail. The test setup requirements being defined by the idealized control system are extremely high demanding a high speed processor and special hardware component developments. The test element is a wire suspended plate being controlled by an array processor via high performance sensors and actuators. First tests on component level indicate the feasibility of the system presently being developed.

Lange, T.↗
NASA NTRS1985

Shock drift acceleration in the presence of waves

Attention is given to the initial results of a model designed to study the modification of the scatter-free, shock drift acceleration of energetic test particles by wave activity in the vicinity of a quasi-perpendicular, fast-mode MHD shock. It is emphasized that the concept of magnetic moment conservation is a valid approximation only in the perpendicular and nearly perpendicular regimes, when the angle theta-Bn between the shock normal and the upstream magnetic field vector is in the range from 70 deg to 90 deg. The present investigation is concerned with one step in a program which is being developed to combine the shock drift and diffusive processes at a shock of arbitrary theta-Bn.

Decker, R. B.↗
NASA NTRS1984

Users guide: Steady-state aerodynamic-loads program for shuttle TPS tiles

A user's guide for the computer program that calculates the steady-state aerodynamic loads on the Shuttle thermal-protection tiles is presented. The main element in the program is the MITAS-II, Martin Marietta Interactive Thermal Analysis System. The MITAS-II is used to calculate the mass flow in a nine-tile model designed to simulate conditions duing a Shuttle flight. The procedures used to execute the program using the MITAS-II software are described. A list of the necessry software and data files along with a brief description of their functions is given. The format of the data file containing the surface pressure data is specified. The interpolation techniques used to calculate the pressure profile over the tile matrix are briefly described. In addition, the output from a sample run is explained. The actual output and the procedure file used to execute the program at NASA Langley Research Center on a CDC CYBER-175 are provided in the appendices.

Kerr, P. A.↗
NASA NTRS1987

High- and low-thrust propulsion systems for the space station

The purpose of the Advanced Development program was to investigate propulsion options for the space station. Two options were investigated in detail: a high-thrust system consisting of 25 to 50 lbf gaseous oxygen/hydrogen rockets, and a low-thrust system of 0.1 lbf multipropellant resistojets. An effort is also being conducted to determine the life capability of hydrazine-fueled thrusters. During the course of this program, studies clearly identified the benefits of utilizing waste water and other fluids as propellant sources. The results of the H/O thruster test programs are presented and the plan to determine the life of hydrazine thrusters is discussed. The background required to establish a long-life resistojet is presented and the first design model is shown in detail.

Jones, R. E.↗
NASA NTRS1986

Wright Brothers Lectureship in Aeronautics: Experience with HiMAT remotely piloted research vehicle - An alternate flight test approach

The highly maneuverable aircraft technology (HiMAT) program explored the various and complex interactions of advanced technologies, such as aeroelastic tailoring, close-coupled canard, and relaxed static stability. A 0.44-subscale remotely piloted research vehicle (RPRV) of a hypothetical fighter airplane was designed and flight-tested to determine the effects of these interactions and to define the design techniques appropriate for advanced fighter technologies. Flexibility and high maneuverability were provided by flight control laws implemented in ground-based computers and telemetered to the vehicle control system during flight tests. The high quality of the flight-measured data and their close correlation with the analytical design modeling proved that the RPRV is a viable and cost-effective tool for developing aerodynamic, structure, and control law requirements for highly maneuverable fighter airplanes of the future.

Deets, D. A.↗
NASA NTRS1987

High- and low-thrust propulsion systems for the Space Station

The purpose of the Advanced Development program was to investigate propulsion options for the space station. Two options were investigated in detail: a high-thrust system consisting of 25 to 50 lbf gaseous oxygen/hydrogen rockets, and a lwo-thrust system of 0.1 lbf multipropellant resistojets. An effort is also being conducted to determine the life capability of hydrazine-fueled thrusters. During the course of this program, studies clearly identified the benefits of utilizing waste water and other fluids as propellant sources. The results of the H/O thruster test programs are presented and the plan to determine the life of hydrazine thrusters is discussed. The background required to establish a long-life resistojet is presented and the first design model is shown in detail.

Jones, Robert E.↗
NASA NTRS1987

Hypervelocity Technology (HVT) crew escape

Conceptual designs are being investigated for escape systems applicable to hypervelocity technology class aerospace vehicles. The concepts selected for further development will provide survivable escape and recovery throughout all phases of flight. Sixteen conceptual escape systems were identified, of which two were viable. The study vehicles included a horizontally launched vehicle (HLV) and a vertically launched vehicle (VLV). Computer-aided design models of the candidate escape systems were developed. State-of-the-art or near-term enabling technologies were identified in such areas as propulsion, life support, thermal protection, and deceleration.

Jines, Lanny A.↗
NASA NTRS1987

Design of robust line-of-sight pointing control system for the SCOLE configuration

Robust compensator design for attitude control of the Spacecraft Control Laboratory Experiment (SCOLE) configuration is considered. A loop-shaping procedure similar to that used in the LQG/LTR method is used to iteratively design the compensator. A satisfactory compensator is obtained by including the rigid modes and three elastic modes in the design model.

Joshi, S. M.↗
NASA NTRS1988

A proposed tropical rainfall measuring mission (TRMM) satellite

The proposed Tropical Rainfall Measuring Mission (TRMM) satellite (presently in its third year of planning), is described. The TRMM satellite, planned for an operational duration of at least three years beginning in the mid-1990s, is intended to obtain high-quality measurements of tropical precipitation by means of information derived from a quantitative spaceborne radar, a multichannel passive microwave radiometer, and an AVHRR. The satellite's orbit will be low-altitude (320 km), for high resolution, and low-inclination (30 to 35 deg), for making it possible to visit each sampling area twice a day. Radar and passive microwave algorithms and rain-retrieval algorithms to be used in precipitation measurements are discussed together with cloud dynamical models designed to test these algorithms.

Simpson, Joanne↗
NASA NTRS1989

Analysis of selected data from the triservice missile data base

An extremely large, systematic, axisymmetric-body/tail-fin data base has been gathered through tests of an innovative missile model design which is described herein. These data were originally obtained for incorporation into a missile aerodynamics code based on engineering methods (Program MISSILE3), but these data are also valuable as diagnostic test cases for developing computational methods because of the individual-fin data included in the data base. Detailed analyses of four sample cases from these data are presented to illustrate interesting individual-fin force and moment trends. These samples quantitatively show how bow shock, fin orientation, fin deflection, and body vortices can produce strong, unusual, and computationally challenging effects on individual fin loads. Flow-visualization photographs are examined to provide physical insight into the cause of these effects.

Allen, Jerry M.↗
NASA NTRS1990

Evaluation of EDR-3 vibration, shock, temperature, and humidity recording unit

The purpose of this evaluation was to determine if the self-contained, off-the-shelf, Environmental Data Recorder 3 (EDR-3) could be qualified to monitor shock, vibration, and temperature during rail transportation of space shuttle solid rocket components. The evaluation testing started in November 1989 and continued until June 1990. Two EDR-3 units were used to monitor both on- and off-plant shipments of shuttle components. In addition, extensive testing was performed at Thiokol's Vibration Test facility, T-53. Testing demonstrated that the EDR-3 is capable of successfully monitoring actual shipments of solid rocket hardware. Thiokol metrology has verified the accuracy of temperature monitoring. In addition, calibrated shock/vibration testing demonstrated that the EDR-3 does accurately record acceleration. It is recommended that the vendor modify the EDR-3 data recovery system to allow remote communication via a 30-foot cable. This would permit communication with the unit mounted on a case segment after a rail car cover is installed. The vendor will make this change and produce a new model, designated EDR-3-10. It is further recommended that Thiokol qualify the EDR-3-10 for transportation monitoring of redesigned solid rocket motor (RSRM) components.

Rees, Kevin G.↗
NASA NTRS1989

Three dimensional simulation of spatial and temporal variability of stratospheric hydrogen chloride

Spatial and temporal variability of atmospheric HCl columns are calculated for January 1979 using a three-dimensional chemistry-transport model designed to provide the best possible representation of stratospheric transport. Large spatial and temporal variability of the HCl columns is shown to be correlated with lower stratospheric potential vorticity and thus to be of dynamical origin. Systematic longitudinal structure is correlated with planetary wave structure. These results can help place spatially and temporally isolated column and profile measurements in a regional and/or global perspective.

Kaye, Jack A.↗
NASA NTRS1989

Asteroidal regoliths - What we do not know

Most of the knowledge of asteroidal regoliths is based on extensive studies of the lunar regolith and the meteorite regolith breccias and on theoretical models designed to match some characteristics of these two types of samples. Two major factors that affect the production and evolution of regolith and make these efforts problematical are changes of regolith properties with time, because of changes in the flux and velocity of impactors, and changes due to the location of the object in the solar system and the strength of the local gravity field. It is emphasized that, at present, not enough data are available on the processes operating on asteroids to be able to define the asteroidal regolith properties; such data can be obtained by missions to individual asteroids.

Mckay, D. S.↗
NASA NTRS1988

Surface flow visualization in the cryogenic wind tunnel

The prospects are reviewed of a range of possible surface flow visualization methods for application to model testing in the large cryogenic wind tunnel. Desirable features are outlined, including the flow details which should be revealed by the various methods. The risks of model and tunnel contamination are discussed, also the coverage of the model surface to be expected, the advance planning and complexity of model design and tunnel equipment required by the visualization method, and the prospects of generating multiple flow images during one tunnel run. The techniques range from the untried to several on which already there is some experience in the cryogenic environment. Directions for further development are suggested.

Goodyer, M. J.↗