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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

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NASA NTRS1989

Radiation and thermal effects on the time-dependent response of T300/934 graphite/epoxy

Experimental studies have suggested that radiation, in conjunction with elevated temperatures, may lead to an exacerbation of the time-dependent response of such materials as T300/934 graphite/epoxy. Attention is given to the results of an investigation into such radiation/temperature effects with this composite system; creep tests were conducted on specimens of both irradiated and nonirradiated T300/934 composite and neat 934 resin specimens, at room temperature and 121 C. The radiation was of 1 MeV electrons, for a total dose of 10,000 Mrads; this simulates a 30-year exposure to radiation in geosynchronous orbit. Irradiation at elevated temperature led to a significant creep-response increase in the initial stages of loading.

Yancey, Robert N.↗

NASA NTRS1991

Improving Sparse-Aperture Interferometric Radiometry

Proposed method for designing spatial arrangement of antennas of sparse-aperture interferometric radiometry (SAIR) system increases spatial resolution of images produced by system. Technique involves cross-correlation of signals received by pairs of small antennas at different locations. Includes ring array of "flood-beam" antennas. Signals from all possible pairs of antennas cross-correlated simultaneously. Diameter of ring determines spatial resolution of image, and distribution of antennas around ring determines sampling characteristics. Conceived to improve proposed remote-sensing SAIR system placed in geosynchronous orbit; also applied to other SAIR systems intended to stare at stationary targets for relatively long times.

Ruf, Christopher S.↗

NASA NTRS1990

Advanced launch vehicle upper stages using liquid propulsion and metallized propellants

Metallized propellants are liquid propellants with a metal additive suspended in a gelled fuel or oxidizer. Typically, aluminum particles are the metal additives. These propellants provide increase in the density and/or the specific impulse of the propulsion system. Using metallized propellants for volume- and mass-constrained upper stages can deliver modest increases in performance for Low Earth Orbit to Geosynchronous Earth Orbit and other Earth orbital transfer missions. Metallized propellants, however, can enable very fast planetary missions with a single-stage upper stage system. Trade studies comparing metallized propellant stage performance with non-metallized upper stages and the Inertial Upper Stage are presented. These upper stages are both one- and two-stage vehicles that provide the added energy to send payloads to altitudes and onto trajectories that are unattainable with only the launch vehicle. The stage designs are controlled by the volume and the mass constraints of the Space Transportation System and Space Transportation System-Cargo launch vehicles. The influences of the density and specific impulse increases enabled by metallized propellants are examined for a variety of different stage and propellant combinations.

Palaszewski, B. A.↗

NASA NTRS1990

Effects of cure temperature, electron radiation, and thermal cycling on P75/930 composites

Graphite/epoxy composites are candidates for future space structures due to high stiffness and dimensional stability requirements of these structures. Typical graphite/epoxy composites are brittle and have high residual stresses which often result in microcracking during the thermal cycling typical of the space environment. Composite materials used in geosynchronous orbit applications will also be exposed to high levels of radiation. The purpose of the present study was to determine the effects of cure temperature and radiation exposure on the shear strength and thermal cycling-induced microcrack density of a high modulus, 275 F cure epoxy, P75/930. The results from the P75/930 are compared to previously reported data on P75/934 and T300/934 where 934 is a standard 350 F cure epoxy. The results of this study reveal that P75/930 is significantly degraded by total doses of electron radiation greater than 10(exp 8) rads and by thermally cycling between -250 F and 150 F. The P75/930 did not have improved microcrack resistance over the P75/934, and the 930 resin system appears to be more sensitive to electron radiation-induced degradation than the 934 resin system.

Funk, Joan G.↗

NASA NTRS1990

Three orbital transfer vehicles

Aerospace engineering students at the Virginia Polytechnic Institute and State University undertook three design projects under the sponsorship of the NASA/USRA Advanced Space Design Program. All three projects addressed cargo and/or crew transportation between low Earth orbit and geosynchronous Earth orbit. Project SPARC presents a preliminary design of a fully reusable, chemically powered aeroassisted vehicle for a transfer of a crew of five and a 6000 to 20000 pound payload. The ASTV project outlines a chemically powered aeroassisted configuration that uses disposable tanks and a relatively small aerobrake to realize propellant savings. The third project, LOCOST, involves a reusable, hybrid laser/chemical vehicle designed for large cargo (up to 88,200 pounds) transportation.

Source record↗

NASA NTRS1990

Space simulation test for thermal control materials

Tests were run in TRW's Combined Environment Facility to examine the degradation of thermal control materials in a simulated space environment. Thermal control materials selected for the test were those presently being used on spacecraft or predicted to be used within the next few years. The geosynchronous orbit environment was selected as the most interesting. One of the goals was to match degradation of those materials with available flight data. Another aim was to determine if degradation can adequately be determined with accelerated or short term ground tests.

Hardgrove, W. R.↗

NASA NTRS1991

Design, performance evaluation, and investigation of the theoretical capabilities of the NASA Millimeter-wave Imaging Radiometer (MIR)

The development of techniques for passive microwave retrieval of water vapor and precipitation parameters using millimeter- and sub-millimeter wavelength channels is reviewed. Channels of particular interest are in the tropospheric transmission windows at 90, 150, 220, and 340 GHz and centered around the water vapor lines at 183 and 325 GHz. Collectively, these channels have potential application in high-resolution mapping (e.g., from geosynchronous orbit), remote sensing of cloud and precipitation parameters, and retrieval of water vapor profiles. Both theoretical and experimental results to date are discussed.

Gasiewski, Albin J.↗

NASA NTRS1990

Advanced Launch Vehicle Upper Stages Using Liquid Propulsion and Metallized Propellants

Metallized propellants are liquid propellants with a metal additive suspended in a gelled fuel or oxidizer. Typically, aluminum (Al) particles are the metal additive. These propellants provide increase in the density and/or the specific impulse of the propulsion system. Using metallized propellant for volume-and mass-constrained upper stages can deliver modest increases in performance for low earth orbit to geosynchronous earth orbit (LEO-GEO) and other earth orbital transfer missions. Metallized propellants, however, can enable very fast planetary missions with a single-stage upper stage system. Trade studies comparing metallized propellant stage performance with non-metallized upper stages and the Inertial Upper Stage (IUS) are presented. These upper stages are both one- and two-stage vehicles that provide the added energy to send payloads to altitudes and onto trajectories that are unattainable with only the launch vehicle. The stage designs are controlled by the volume and the mass constraints of the Space Transportation System (STS) and Space Transportation System-Cargo (STS-C) launch vehicles. The influences of the density and specific impulse increases enabled by metallized propellants are examined for a variety of different stage and propellant combinations.

Palaszewski, Bryan A.↗

NASA NTRS1991

The 1983 tail-era data series. Volume 3: Geosynchronous particle measurements

Geosynchronous particle measurements are presented for comparison with same-scale plots of ISEE 3 plasma and field data. Shown for each day are electron and proton fluxes measured with the low-energy-range electron and the low-energy-range proton detectors of the Los Alamos Charged Particle Analyzer. This instrument has flown aboard several geosynchronous orbit satellites, including the three spacecraft from which the presented data were obtained. The presented data are 5-min averages of the integral flux in each of several energy channels.

Fairfield, D. H.↗

NASA NTRS1991

Small capacity, low cost (Ni-H2) design concept for commercial, military, and higher-volume aerospace applications

Nickel-Hydrogen (Ni-H2) batteries have become the technology of choice for both commercial and defense-related satellites in geosynchronous orbits. Their use for low-earth- orbit (LEO) applications is not as advanced, but seems just as inevitable because of their inherent advantages over nickel-cadmium batteries. These include superior energy density, longer cycle life, and better tolerance to over-charge and reversal. Ni-H2 cells have the added advantage in both construction and operation of not presenting the environmental possibility of cadmium pollution. Unfortunately, but necessarily, the design of these cells has been driven to high cost by the sophistication of the satellites and their uses. Now, using most of the same concepts but less costly materials and techniques, a low-cost, small cell design has been developed. Combined with the concept of the common pressure vessel, this new design promises to be ideal for the "small-sat" and commercial markets which, increasingly, are calling for large numbers of less-expensive satellites.

James R Wheeler↗

NASA NTRS1990

Satellite eclipse power by laser illumination

A method is proposed to eliminate the energy storage system required to power a satellite in geosynchronous orbit during eclipse. An array of high-power CW lasers is situated at one or more ground locations in line of sight of the satellite, preferably on mountaintops. The lasers are provided with a tracking system, and lenses or mirrors of sufficient size to reduce the beam spread due to diffraction. As the satellite enters eclipse, the laser arrays illuminate the solar arrays on the satellite to a level sufficient to provide operating power.

Landis, Geoffrey A.↗

NASA NTRS1989

Optical alignment equipment and methods for visible and IR imaging meteorological radiometer

This paper describes the test equipment required for precise IR and visible channel microradian alignments for geosynchronous orbiting meteorological instruments. The test equipment design criteria, design, function and use are explained in detail. Wave front error measurements, vibration isolation, thermal compensation and stress free mounting configurations are described.

Herendeen, R.↗

NASA NTRS1991

Ion cyclotron waves near L = 4.6 - A ground-satellite correlation study

Results are presented of the first ground-satellite correlation study of ion cyclotron wave events inside geosynchronous orbit. Several intervals are found during which waves at the same frequency were observed simultaneously by the DE 1 Goddard Space Flight Center Fluxgate Magnetometer and by the Air Force Geophysics Laboratory Magnetometer Network. This represents about 33 percent of the intervals during which waves were seen on the ground and DE 1 was in a favorable location (near the geomagnetic equator around L = 4.6) to observe the wave generation region. Three of seven simultaneous events showed a positive correlation when a detailed correlation analysis was performed. Peaks in the the cross-correlation function occurred at delays of 30-100 s and are interpreted as the group delay time of signals from space to the ground station. The small number of events seen in space during conjunction intervals results from the satellite's path missing the source region.

Ludlow, G. R.↗

NASA NTRS1990

Workspace visualization and time-delay telerobotic operations

The paper examines the performance of telerobotic tasks where the operator and robot are physically separated, and a comunication time delay of up to several seconds between them exists. This situation is applicable to space robotic servicing-assembly-maintenance operations on low earth or geosynchronous orbits with a ground-based command station. Attention is given to two developments which address advanced time-delay teleoperations for unstructured tasks: (1) the 'phantom robot', a real-time predictive graphics simulator developed to allow teleoperator eye-to-hand coordination or robot free-space kinematics under a time delay of several seconds; and (2) shared compliance control, a modified form of automatic electromechanical impedance control employed in parallel with manual position control to permit soft contact and grasp compliance with workpiece geometry under a time delay of several seconds.

Schenker, P. S.↗

NASA NTRS1992

Effects Of Irradiation By Electrons On Two Polyimides

Polyimides of new class, known as polyetherimides, used for composites and castings. Study undertaken to compare effects of electron radiation, in doses expected for 30-year missions in geosynchronous orbit, on molecular structures and tensile properties of two commercially available polyimides: polypyromellitimide and polyetherimide. Findings helpful in development of new polymers that endure radiation, leading to synthesis of polymers not having methyl groups or other moieties that are sources of hydrogen, inhibiting self-mending. Significance of study for polymer industry relating to structures in outer space considerable.

Long, Edward R., Jr.↗

NASA NTRS1991

Tracking and Data Relay Satellite System (TDRSS)

The DSN (Deep Space Network) mission support requirements for the Tracking and Data Relay Satellite System (TDRSS) are summarized. The TDRSS consists of four identical satellites in geosynchronous orbits (35,800 km) and a dedicated ground station. The payload of each satellite is a telecommunications service system that relays communication signals between low earth-orbiting user spacecraft and the TDRSS ground terminal. Mission objectives are outlined and the DSN support requirements are defined through the presentation of tables and narratives describing the spacecraft flight profile; DSN support coverage; frequency assignments; support parameters for telemetry, command and support systems; and tracking support responsibility.

Mckenzie, J.↗

NASA NTRS1992

Upper stages using liquid propulsion and metallized propellants

Metallized propellants are liquid propellants with a metal additive suspended in a gelled fuel. Typically, aluminum particles are the metal additive. These propellants increase the density and/or the specific impulse of the propulsion system. Using metallized propellants for volume- and mass-constrained upper stages can deliver modest increases in performance for low Earth orbit to geosynchronous Earth orbit (LEO-GEO) and other Earth-orbital transfer missions. However, using metallized propellants for planetary missions can deliver great reductions in flight time with a single-stage, upper-stage system. Tradeoff studies comparing metallized propellant stage performance with nonmetallized upper stages and the Inertial Upper Stage (IUS) are presented. These upper stages, launched from the STS and STS-C, are both one- and two-stage vehicles that provide the added energy to send payloads to high altitude orbits and onto interplanetary trajectories that are unattainable with only the Space Transportation System (STS) and the Space Transportation System-Cargo (STS-C). The stage designs are controlled by the volume and the mass constraints of the STS and STS-C launch vehicles. The influences of the density and specific impulse increases enabled by metallized propellants are examined for a variety of different stage and propellant combinations.

Palaszewski, Bryan A.↗

NASA NTRS1991

Phased array antenna beamforming using optical processor

The feasibility of optical processor based beamforming for microwave array antennas is investigated. The primary focus is on systems utilizing the 20/30 GHz communications band and a transmit configuration exclusively to serve this band. A mathematical model is developed for computation of candidate design configurations. The model is capable of determination of the necessary design parameters required for spatial aspects of the microwave 'footprint' (beam) formation. Computed example beams transmitted from geosynchronous orbit are presented to demonstrate network capabilities. The effect of the processor on the output microwave signal to noise quality at the antenna interface is also considered.

Anderson, L. P.↗