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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 253 records · Page 14

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NASA NTRS1991

High voltage plasma sheath analysis related to TSS-1

On the first mission of the Tethered Satellite System (TSS-1), a 1.8 m diameter spherical satellite will be deployed a distance of 20 km above the space shuttle Orbiter on an insulated conducting tether. The satellite will be held at electric potentials up to 5000 volts positive with respect to the ambient plasma. Due to the passage of the conducting tether through the Earth's magnetic field, an emf will be created, driving electrons down the tether to the orbiter, out through an electron gun into the ionosphere and back into the positive biased satellite. Instrumentation on the satellite will measure electron flow to the surface at several locations, but these detectors have a limited range of acceptance angle. The problem addressed herein is the determination of the electron current distribution over the satellite surface and the angle of incidence of the incoming electrons relative to the surface normal.

Sheldon, John W.↗

NASA NTRS1995

Low-pressure electrical discharge experiment to simulate high-altitude lightning above thunderclouds

Recently, extremely interesting high-altitude cloud-ionosphere electrical discharges, like lightning above thunderstorms, have been observed from NASA's space shuttle missions and during airborne and ground-based experiments. To understand these discharges, a new experiment was conceived to simulate a thundercloud in a vacuum chamber using a dielectric in particulate form into which electrodes were inserted to create charge centers analogous to those in an electrified cloud. To represent the ionosphere, a conducting medium (metallic plate) was introduced at the top of the chamber. It was found that for different pressures between approximately 1 and 300 mb, corresponding to various upper atmospheric altitudes, different discharges occurred above the simulated thundercloud, and these bore a remarkable similarity to the observed atmospheric phenomena. At pressures greater than 300 mb, these discharges were rare and only discharges within the simulated thundercloud were observed. Use of a particulate dielectric was critical for the successful simulation of the high-altitude lightning.

Jarzembski, M. A.↗

NASA NTRS1995

Automatic Radiated Susceptibility Test System for Payload Equipment

An automatic radiated susceptibility test system (ARSTS) was developed for NASA Lewis Research Center's Electro-magnetic Interference laboratory. According to MSFC-SPEC 521B, any electrical or electronic equipment that will be transported by the spacelab and space shuttle must be tested for susceptibility to electromagnetic interference. This state-of-the-art automatic test system performs necessary calculations; analyzes, processes, and records a great quantity of measured data; and monitors the equipment being tested in real-time and with minimal user intervention. ARSTS reduces costly test time, increases test accuracy, and provides reliable test results.

Ngo, Hoai T.↗

NASA NTRS2003

Robotic Mars Sample Return: Risk Assessment and Analysis Report

A comparison of the risk associated with two alternative scenarios for a robotic Mars sample return mission was conducted. Two alternative mission scenarios were identified, the Jet Propulsion Lab (JPL) reference Mission and a mission proposed by Johnson Space Center (JSC). The JPL mission was characterized by two landers and an orbiter, and a Mars orbit rendezvous to retrieve the samples. The JSC mission (Direct/SEP) involves a solar electric propulsion (SEP) return to earth followed by a rendezvous with the space shuttle in earth orbit. A qualitative risk assessment to identify and characterize the risks, and a risk analysis to quantify the risks were conducted on these missions. Technical descriptions of the competing scenarios were developed in conjunction with NASA engineers and the sequence of events for each candidate mission was developed. Risk distributions associated with individual and combinations of events were consolidated using event tree analysis in conjunction with Monte Carlo techniques to develop probabilities of mission success for each of the various alternatives. The results were the probability of success of various end states for each candidate scenario. These end states ranged from complete success through various levels of partial success to complete failure. Overall probability of success for the Direct/SEP mission was determined to be 66% for the return of at least one sample and 58% for the JPL mission for the return of at least one sample cache. Values were also determined for intermediate events and end states as well as for the probability of violation of planetary protection. Overall mission planetary protection event probabilities of occurrence were determined to be 0.002% and 1.3% for the Direct/SEP and JPL Reference missions respectively.

Lalk, Thomas R.↗

NASA NTRS1988

Refractory metal alloys and composites for space nuclear power systems

Space power requirements for future NASA and other U.S. missions will range from a few kilowatts to megawatts of electricity. Maximum efficiency is a key goal of any power system in order to minimize weight and size so that the Space Shuttle may be used a minimum number of times to put the power supply into orbit. Nuclear power has been identified as the primary power source to meet these high levels of electrical demand. One method to achieve maximum efficiency is to operate the power supply, energy conservation system, and related components at relatively high temperatures. For systems now in the planning stages, design temperatures range from 1300 K for the immediate future to as high as 1700 K for the advanced systems. NASA Lewis Research Center has undertaken a research program on advanced technology of refractory metal alloys and composites that will provide baseline information for space power systems in the 1900's and the 21st century. Special emphasis is focused on the refractory metal alloys of niobium and on the refractory metal composites which utilize tungsten alloy wires for reinforcement. Basic research on the creep and creep-rupture properties of wires, matrices, and composites are discussed.

Titran, Robert H.↗

NASA NTRS1973

The evolution of the SEP stage /SEPS/ concept

The features of a solar electric propulsion (SEP) stage are examined. An SEP stage (SEPS) contains all of the subsystems required to deliver separable payloads to the desired target and to support its own operations. These include attitude control, communications, data handling, and computer subsystems in addition to the solar array and thrust subsystems required for electric propulsion. SEPS can provide subsystem support to attached payloads for comet flyby and asteroid rendezvous. It can accommodate both planetary and geosynchronous missions by the use of mission-peculiar modules. In addition SEPS can assist the shuttle tug transportation system in earth-orbital applications. Aspects of mission analysis are discussed together with details of the electric propulsion system including solar array considerations.

Gilbert, J.↗

NASA NTRS1987

High power ion thruster performance

The ion thruster is one of several forms of space electric propulsion being considered for use on future SP-100 based missions. One possible major mission ground rule is the use of single Space Shuttle launch. Thus, the mass in orbit at the reactor activation altitude would be limited by the Shuttle mass constraints. When the spacecraft subsystem masses are subtracted from this available mass limit, a maximum propellant mass may be calculated. Knowing the characteristics of each type of electric thruster allow maximum values of total impulse, mission velocity increment, and thrusting time to be calculated. Because ion thrusters easily operate at high values of efficiency (60 to 70 percent) and specific impulse (3000 to 5000 sec), they can impart large values of total impulse to a spacecraft. They also can be operated with separate control of the propellant flow rate and exhaust velocity. Values are presented of demonstrated and projected performance of high power ion thrusters used in an analysis of electric propulsion for an SP-100 based mission.

Rawlin, Vincent K.↗

NASA NTRS1999

Electrohydrodynamic Stability of a Liquid Bridge: The "ALEX" Experiment

To provide insight into the roles of electrical forces, experiments on the stability of a liquid bridge were carried out during the 1996 Life And Microgravity Science Mission on the space shuttle Columbia. In terrestrial laboratories a Plateau configuration (where the bridge is surrounded by a matched density liquid) is necessary to avoid deformation due to buoyancy. This complicates the electrical boundary conditions, since charge is transported across the liquid-liquid interface. In the microgravity environment, a cylindrical bridge can be deployed in a gas which considerably simplifies the boundary condition. Nevertheless, to provide a tie-in to terrestrial experiments, two-phase experiments were carried out. The agreement with previous work was excellent. Then several experiments were conducted with a bridge deployed in a dielectric gas, SF6. In experiments with steady fields, it was found that the bridge was less stable than predicted by a linearized stability analysis using the Taylor-Melcher leaky dielectric model.

Burcham, C. L.↗

NASA NTRS1987

An electrically conductive thermal control surface for spacecraft encountering Low-Earth Orbit (LEO) atomic oxygen indium tin oxide-coated thermal blankets

An organic black thermal blanket material was coated with indium tin oxide (ITO) to prevent blanket degradation in the low Earth orbit (LEO) atomic oxygen environment. The blankets were designed for the Galileo spacecraft. Galileo was initially intended for space shuttle launch and would, therefore, have been exposed to atomic oxygen in LEO for between 10 and 25 hours. Two processes for depositing ITO are described. Thermooptical, electrical, and chemical properties of the ITO film are presented as a function of the deposition process. Results of exposure of the ITO film to atomic oxygen (from a shuttle flight) and radiation exposure (simulated Jovian environment) are also presented. It is shown that the ITO-protected thermal blankets would resist the anticipated LEO oxygen and Jovian radiation yet provide adequate thermooptical and electrical resistance. Reference is made to the ESA Ulysses spacecraft, which also used ITO protection on thermal control surfaces.

Bauer, J. L.↗

NASA NTRS1972

Space shuttle auxiliary propulsion system design study. Phase D report: Oxygen-hydrogen special RCS studies

Two alternate oxygen-hydrogen auxiliary propulsion system concepts for use with the space shuttle vehicle were evaluated. The two concepts considered were: (1) gaseous oxygen-hydrogen systems with electric or hydraulic motor driven pumps to provide system pressure and (2) liquid oxygen-hydrogen systems which delivered propellants to the engines in a liquid state without the need for pumps. The various means of implementing each of the concepts are compared on the basis of weight, technology requirements, and operational considerations. It was determined that the liquid oxygen-hydrogen system concepts have the potential to produce substantial weight reductions in the space shuttle orbiter total impulse range.

Baumann, T. L.↗

NASA NTRS2002

Characterization of Subsystems for a WB-003 Single Stage Shuttle

Subsystems for an all oxygen-hydrogen-single-stage shuttle are characterized for a vehicle designated WB-003. Features of the vehicle include all-electric actuation, fiber optics for information circuitry, fuel cells for power generation, and extensive use of composites for structure. The vehicle is sized for the delivery of a 25,000 lb. payload to a space station orbit without crew. When crew are being delivered, they are carried in a module in the payload bay with escape and manual override capabilities. The underlying reason for undertaking this task is to provide a framework for the study of the operations costs of the newer shuttles.

MacConochie, Ian O.↗

NASA NTRS1987

High power ion thruster performance

The ion thruster is one of several forms of space electric propulsion being considered for use on future SP-100-based missions. One possible major mission ground rule is the use of a single Space Shuttle launch. Thus, the mass in orbit at the reactor activation altitude would be limited by the Shuttle mass constraints. When the spacecraft subsystem masses are subtracted from this available mass limit, a maximum propellant mass may be calculated. Knowing the characteristics of each type of electric thruster allows maximum values of total impulse, mission velocity increment, and thrusting time to be calculated. Because ion thrusters easily operate at high values of efficiency (60 to 70%) and specific impulse (3000 to 5000 sec), they can impart large values of total impulse to a spacecraft. They also can be operated with separate control of the propellant flow rate and exhaust velocity. This paper presents values of demonstrated and projected performance of high power ion thrusters used in an analysis of electric propulsion for an SP-100 based mission.

Rawlin, Vincent K.↗

NASA NTRS1985

Development of the VOLT-A shuttle experiment

The NASA Lewis Research Center (LeRC) is investigating potential problems associated with the operation of high voltage solar cell arrays in the space plasma environment. At high voltages, interactions between the solar array and the space plasma could result in unacceptable levels of electrical discharge (arcing) and/or parasitic losses (current drains from the array to the plasma). The objective of the Voltage Operating Limit Tests (VOLT-A) Shuttle bay experiment is to characterize space plasma/solar cell panel interactions in low earth orbit. VOLT-A consists of an experiment plate subassembly which contains four solar panels, an electronics subassembly and a Langmuir probe subassembly mounted on an MPESS carrier. During a given 8.25 hour data taking period (5-1/2 continuous orbits), the solar panels, which represent state-of-the-art solar cell technologies, will be sequentially subjected to bias voltages in steps ranging from minus 626 V to plus 313 V. Appropriate measurements will be made at each voltage to characterize arcing and parasitic losses. Corresponding measurements of the plasma environment (plasma density, electron temperature and neutral density) will also be made. Data will be recorded on an on-board tape recorder for subsequent data reduction and analysis.

Bifano, W. J.↗

NASA NTRS1985

Development of the VOLT-A Shuttle experiment

Bifano, William J.↗

NASA NTRS1979

A programmable power processor for a 25-kW power module

A discussion of the power processor for an electrical power system for a 25-kW Power Module that could support the Space Shuttle program during the 1980's and 1990's and which could be a stepping stone to future large space power systems is presented. Trades that led to the selection of a microprocessor-controlled power processor are briefly discussed. Emphasis is given to the power processing equipment that uses a microprocessor to provide versatility that allows multiple use and to provide for future growth by reprogramming output voltage to a higher level (to 120 V from 30 V). Efficiency data from a breadboard programmable power processor are presented, and component selection and design considerations are also discussed.

Lanier, R., Jr.↗

NASA NTRS1985

An electrochemical study of the corrosion behavior of primer coated 2219-T87 aluminum

The corrosion behavior for 2219-T87 aluminum coated with various primers, including those used for the external tank and solid rocket boosters of the Space Shuttle Transportation System, were investigated using electrochemical techniques. Corrosion potential time, polarization resistance time, electrical resistance time, and corrosion rate time measurements were all investigated. It was found that electrical resistance time and corrosion rate time measurement were most useful for studying the corrosion behavior of painted aluminum. Electrical resistance time determination give useful information concerning the porosity of paint films, while corrosion rate time curves give important information concerning overall corrosion rates and corrosion mechanisms. In general, the corrosion rate time curves all exhibited at least one peak during the 30 day test period, which was attributed, according to the proposed mechanisms, to the onset of the hydrogen evolution reaction and the beginning of destruction of the protective properties of the paint film.

Danford, M. D.↗

NASA NTRS1985

The investigation of tethered satellite system dynamics

The tether control law to retrieve the satellite was modified in order to have a smooth retrieval trajectory of the satellite that minimizes the thruster activation. The satellite thrusters were added to the rotational dynamics computer code and a preliminary control logic was implemented to simulate them during the retrieval maneuver. The high resolution computer code for modelling the three dimensional dynamics of untensioned tether, SLACK3, was made fully operative and a set of computer simulations of possible tether breakages was run. The distribution of the electric field around an electrodynamic tether in vacuo severed at some length from the shuttle was computed with a three dimensional electrodynamic computer code.

Lorenzini, E.↗

NASA NTRS1986

A spacecraft cooling system for a charged coupled device

This paper describes the thermal analysis, design, and testing of a dedicated cooling system for a Spartan spacecraft payload. A simple reliable design that requires minimum power consumption and minimum weight was developed. The payload has a CCD detector that must be maintained at a temperature of approximately -40 C or colder. The cooling system consists of a fin radiator, dual redundant heat pipes, and a thermal electric device (TED). The system was analytically modeled through the use of the Simplified Shuttle Payload Thermal Analyzer (SSPTA) computer program. A thermal test of the system simulating flight conditions was conducted to correlate the computer model and verify performance specifications.

Walker, Mary S.↗