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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Satellite ephemerides for the Voyager Uranus encounter

Uranian satellite ephemerides are needed by the Voyager project to support both navigation and acquisition of scientific data. This paper presents the approach being taken to develop the ephemerides and details the initial phase of the development. That phase involves the analytical modeling of the satellites' motion and the adjustment of the model to fit astronomical observations. The paper describes the model and gives the result of a fit to 71 years of observations.

Jacobson, R. A.↗
NASA NTRS1984

Improving the Spacelab mass memory unit tape layout with a simulation model

A tape drive called the Mass Memory Unit (MMU) stores software used by Spacelab computers. MMU tape motion must be minimized during typical flight operations to avoid a loss of scientific data. A projection of the tape motion is needed for evaluation of candidate tape layouts. A computer simulation of the scheduled and unscheduled MMU tape accesses is developed for this purpose. This simulation permits evaluations of candidate tape layouts by tracking and summarizing tape movements. The factors that affect tape travel are investigated and a heuristic is developed to find a good tape layout. An improved tape layout for Spacelab I is selected after the evaluation of fourteen candidates. The simulation model will provide the ability to determine MMU layouts that substantially decrease the tape travel on future Spacelab flights.

Noneman, S. R.↗
NASA NTRS1985

The Venus Balloon Project

During the Soviet Vega Mission to Venus and Comet Halley, two instrumented balloons will be placed into the Venusian atmosphere in June 1985. These Soviet/French balloons will be used to study the structure and dynamics of the Venusian atmosphere by means of in situ measurements and earth-based VLBI determination of balloon position and velocity. The DSN 64-meter subnet will be part of an international network of antennas organized by the French to support this mission. The DSN is installing new L-band receiving systems for this task. All scientific data from the balloons will be analyzed by a joint Soviet/French/U.S. science team.

Preston, R. A.↗
NASA NTRS1985

Electro-science Requirements for Shuttle-attached Antenna Flight Experiments

The activities of an in-house electro-science task group organized to conduct studies of shuttle-attached flight experiments using the 15-meter hoop-column antennas as a research tool for developing both improved sensor technology and LSA technology are described. Some experiments could provide significant amounts of scientific data such as radio star mapping and definition of ocean current eddies over limited geographic regions. The experiments originate from the microwave remote sensing community and other areas which require the inherently higher resolution and boresite gain of large space antennas. Technology experiments are also being studied which would use the 15-meter antenna experiments as a stepping stone to 50 to 100 meter class reflector technology in the future. An antenna technology experiment using the 15-meter antenna in a shuttle-attached mission is discussed. Electromagnetic modeling is correct for each major subsystem and also to verify the interrelations of the subsystems.

Grantham, W. L.↗
NASA NTRS1985

Error analyses for the delivery of a spinning probe to Jupiter

The task of delivering the Galileo Probe to specified atmospheric entry conditions at Jupiter is especially challenging because tracking, trajectory corrections, and attitude adjustments are not possible after release of the Probe from the carrier vehicle. Statistical analysis of the spacecraft dynamics mapped into Probe dispersions in atmosphere-relative and relay-geometry parameters show that attitude stability, heating, and relay performance requirements can be satisfied. Reconstruction techniques are used to enhance estimates of the delivery parameters to permit correct interpretation of the scientific data for the Jovian atmosphere. A tradeoff which sacrifices some delivery accuracy and propellant is shown to guarantee satisfaction of a very tight reconstruction requirement for the trajectory considered in this report.

Hintz, G. R.↗
NASA NTRS1985

System study of the utilization of space for carbon dioxide research

The objectives included: compiling and selecting the Scientific Data Requirements (SDRs) pertinent to the CO2 Research Program that have the potential to be more successfully achieved by utilizing space-based sensor systems; assessment of potential space technology in monitoring those parameters which may be important first indicators of climate change due to increasing atmospheric CO2, including the behavior of the West Antarctic ice sheet; and determine the potential of space technology for monitoring those parameters to improve understanding of the coupling between CO2 and cloud cover.

Glaser, P. E.↗
NASA NTRS1985

Approaches to the utilization of space for CO2 research

A system study of the potential of space technology to monitor climate changes and improve the understanding of the coupling beteen CO2 and cloud cover is summarized. The basis for the study is scientific data requirements pertinent to the U.S. Department of Energy's CO2 Research Program. The capabilities of space-based sensor systems are matched to meet these requirements. New sensor system concepts are identified, including a Space Shuttle-launched recalibration package to provide for continuity of measurement and recalibration between satellites, a high-orbit radiation budget satellite, or parallax sensor to measure cloud altitude, a passive method for the direct measurements of CO2 and a high-altitude powered platform to monitor select regional parameters. Space-based sensor systems that could be the development focus for the time frames of 0-5, 5-10 and 10-20 years are recommended.

Glaser, P.↗
NASA NTRS1986

Ephemerides of the Uranian satellites determined from earth-based astrometric and Voyager imaging observations

Uranian satellite ephemerides were needed by the Voyager project to support both navigation and acquisition of scientific data. This paper outlines the mathematical modeling approach taken to generate those ephemerides and discusses their pre-encounter development, real time updating, and post-encounter refinement. The results presented include the final set of model parameters which generate the ephemerides that best fit the Voyager optical data as well as the earth based observations of the satellites.

Jacobson, R. A.↗
NASA NTRS1986

SIR-C, the next generation spaceborne SAR

SIR-C represents a significant advance in spaceborne SAR system capabilities. The design approach is responsive to the requirements identified by the Science Steering Committee. This multimode feature of the sensor will provide science investigators with new dimensions in acquiring and interpreting scientific data. The flexibility of the SIR-C design will provide a core instrument which will meet the needs of SAR data users into the 1990's and serve as a foundation for ultimate incorporation into the EOS platform.

Caro, E. R.↗
NASA NTRS1985

Engineering graphics and image processing at Langley Research Center

The objective of making raster graphics and image processing techniques readily available for the analysis and display of engineering and scientific data is stated. The approach is to develop and acquire tools and skills which are applied to support research activities in such disciplines as aeronautics and structures. A listing of grants and key personnel are given.

Voigt, Susan J.↗
NASA NTRS1986

Parachute recovery location aids

This paper presents various types of location aid devices that may be used individually or in some combination to locate parachutes designed for the recovery of scientific data and instrumentation that have impacted on the earth's surface. Systems may be used on either recovery parachute systems or high altitude parachute systems. It is noted that all location aids are passive during the data gathering period of flight. Initial results of test data from two types of direction finder receivers are presented as well as their application and use with parachute borne and other location transmitters.

Silbert, M. N.↗
NASA NTRS1987

Planning the Voyager spacecraft's mission to Uranus

The application of the systems engineering process to the planning of the Voyager spacecraft mission is described. The Mission Planning Office prepared guidelines that controlled the use of the project and multimission resources and spacecraft consumables in order to obtain valuable scientific data at an acceptable risk level. Examples of mission planning which are concerned with the design of the Deep Space Network antenna, the uplink window for transmitting computer command subsystem loads, and the contingency and risk assessment functions are presented.

Plagemann, Stephen H.↗
NASA NTRS1987

Small space reactor power systems for unmanned solar system exploration missions

A preliminary feasibility study of the application of small nuclear reactor space power systems to the Mariner Mark II Cassini spacecraft/mission was conducted. The purpose of the study was to identify and assess the technology and performance issues associated with the reactor power system/spacecraft/mission integration. The Cassini mission was selected because study of the Saturn system was identified as a high priority outer planet exploration objective. Reactor power systems applied to this mission were evaluated for two different uses. First, a very small 1 kWe reactor power system was used as an RTG replacement for the nominal spacecraft mission science payload power requirements while still retaining the spacecraft's usual bipropellant chemical propulsion system. The second use of reactor power involved the additional replacement of the chemical propulsion system with a small reactor power system and an electric propulsion system. The study also provides an examination of potential applications for the additional power available for scientific data collection. The reactor power system characteristics utilized in the study were based on a parametric mass model that was developed specifically for these low power applications. The model was generated following a neutronic safety and operational feasibility assessment of six small reactor concepts solicited from U.S. industry. This assessment provided the validation of reactor safety for all mission phases and generatad the reactor mass and dimensional data needed for the system mass model.

Bloomfield, Harvey S.↗
NASA NTRS1987

Results from a series of tethered rocket experiments

This paper reports the results of three tethered rocket experiments conducted as part of a U.S.-Japan joint program under way since 1980. The major purpose of the experiments is to obtain technical and scientific data supporting the figure electrodynamic tethered subsatellite experiments by the Space Shuttle. Vehicle charging due to dc beam emission up to 80 mA in the 150-200 km altitude range was repeatedly measured by both Langmuir and floating probes, and was found to be usually less than 10 V. During the 80 mA emission, clear evidence for the ignition of a beam-plasma discharge was obtained. In a tether deployment experiment, it was found that the tether wire acted as an antenna whose impedance decreased with the extension of the wire both in high-frequency and very low-frequency bands. Substantial rocket charging was observed during periods of electron-beam very low-frequency pulsing.

Sasaki, S.↗
NASA NTRS1988

Outer atmospheric research

The region above the earth from about 90 km to 150 km is a major part of the upper or outer atmosphere. It is relatively unexplored, being too high for balloons or aircraft and too low for persistent orbiting spacecraft. However, the concept of a tethered subsatellite, deployed downward from an orbiting, more massive craft such as the Space Shuttle, opens the possibility of a research capability that could provide global mapping of this region. The need for research in this thick spherical shell above the earth falls into two major categories: (1) scientific data for understanding and modeling the global atmosphere and thereby determining its role in the earth system, and (2) engineering data for the design of future aerospace vehicles that will operate there. This paper presents an overview and synthesis of the currently perceived research needs and the state-of-the-art of the proposed tethered research capability.

Anderson, John L.↗
NASA NTRS1987

The Voyager-2 Neptune encounter

Aspects of the encounter of Voyager 2 with Neptune which will occur during the summer of 1989 are discussed. The major scientific objectives and the resulting trajectory characteristics are reviewed. The technological requirements for transmitting the scientific data to earth are addressed, and the hardware and software aboard the satellite which will accomplish the transmission are described.

Kosman, William J.↗
NASA NTRS1989

The controllability of the aeroassist flight experiment atmospheric skip trajectory

The Aeroassist Flight Experiment (AFE) will be the first vehicle to simulate a return from geosynchronous orbit, deplete energy during an aerobraking maneuver, and navigate back out of the atmosphere to a low earth orbit It will gather scientific data necessary for future Aeroasisted Orbitl Transfer Vehicles (AOTV's). Critical to mission success is the ability of the atmospheric guidance to accurately attain a targeted post-aeropass orbital apogee while nulling inclination errors and compensating for dispersions in state, aerodynamic, and atmospheric parameters. In typing to satisfy mission constraints, atmospheric entry-interface (EI) conditions, guidance gains, and trajectory. The results of the investigation are presented; emphasizing the adverse effects of dispersed atmospheres on trajectory controllability.

Wood, R.↗
NASA NTRS1990

Ephemerides of the major Neptunian satellites determined from earth-based astrometric and Voyager imaging observations

The Voyager project used Neptunian satellite ephemerides to support both navigation and acquisition of scientific data. The development of postencounter ephemerides for the satellites Triton, Nereid, and 1989N1 is discussed. Primary results are the final set of model parameters which generate orbits that best fit both the earth-based satellite observations and data acquired by Voyager. The ephemerides are compared with those generated preencounter, and the accuracy of the final ephemerides is assessed. Mean orbital elements are also provided as a geometrical representation for the satellite orbits.

Jacobson, R. A.↗