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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Phase 3 study of selected tether applications in space. Volume 1: Executive summary

A tethered launch assist from the Shuttle for payloads with up to 10,000 kg mass for the mission model and the tethering of a 15,000 kg science platform for the space station were addressed. Also encompassed was the design and cost analysis for a variable g device that could be placed on the tether and allow ultralow g or other types of experiments to be conducted. Numerous tether applications were examined and their theoretical feasibility and technology requirements were assessed.

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NASA NTRS1986

Attitude control of tethered spacecraft

Procedures for achieving attitude control of single-body and multibody, tethered spacecraft are examined. The design considerations for attitude control and the generation of control torques are described. Two dimensional tether attach point motion is utilized to produce torque about two axes and the third axis is controlled with either a control moment gyro or a reaction wheel. The ability to perform attitude control of a tethered spacecraft is evaluated in the Kinetic Isolation Tether Experiment (KITE). It is observed that the KITE/SPARTAN design bandwidth is adequate to fully utilize the capability of attitude sensors with accuracies in the 1-arcsec range.

Lemke, L. G.↗
NASA NTRS1986

Results from a series of US/Japan tethered rocket experiments

Tethered rocket experiments have been carried out four times during a US-Japan joint space program in progress since 1980. The goal of the rocket program has been to perform a new type of active experiment by ejecting an electron beam from the tethered mother-daughter payload system. In the third and fourth rocket flights, the conductive tether wire was deployed more than 400 m. It was found that the tether wire acted as an antenna and its antenna impedance decreased with the extension of the wire both in HF and VLF bands. The vehicle charging due to the beam emission up to 80 mA was repeatedly measured in the series of the experiments. During the 80 mA emission, a clear evidence for the ignition of a beam plasma discharge was obtained by the plasma probe, photometers and wave receivers.

Sasaki, S.↗
NASA NTRS1986

Benefits of tether momentum transfer to Space Station operations

A full solar cycle (1994-2004) is analyzed to study tether and nontether Space Station operations. The Space Station yearly altitude variation for the two approaches are investigated; it is observed that the optimum tether approach provides greater benefits that the nontether approach due to the cargon weight gain associated with the preferred low altitudes of the optimum variable altitude tether approach. The advantages provided by the combining a variable altitude/OTV launch approach are discussed. The baseline and tethered Shuttle deployments are compared and the design and capabilities of the deployer system are examined.

Woodis, W. R.↗
NASA NTRS1987

A survey of tether applications to planetary exploration

Concepts for the use of tethers in various hypothetical astronomical research missions are discussed. Tethers used to study the atmospheres of Venus and Mars and the magnetosphere of Jupiter are examined, and possible orbiting tether systems at the moon and Mars are shown and described. A tether method for collecting a sample from Comet Halley is addressed along with a system for hovering near a comet. A multiple sample return system for asteroids is described, and a heliocentric Alfven engine concept to study the solar wind is discussed.

Penzo, Paul A.↗
NASA NTRS1987

Technology and applications - Convergence to a tether capability

In this paper, a convergence of interest from many potential tether applications is synthesized into one application that could be satisfied by a tethered satellite capability. This application is the use of a tethered research satellite deployed downward from the Shuttle Orbiter to gather scientific and engineering/technology data about the outer atmosphere from about 90 to 130 km. The atmospheric and aerothermodynamic information needed about this region of the atmosphere is identified, and the specific applications of that information, the tether capability, and the technology needed to gather the data are described.

Anderson, John L.↗
NASA NTRS1987

Study of Plasma Motor Generator (PMG) tether system for orbit reboost

Detailed designs were produced for a 2 kW plasma motor generator tether system based largely on existing hardware and hardware designs. Specifically, the hollow cathode design and electronics are derived from ion propulsion equipment. A prototype tether was constructed and will be tested for deployment, strength, resistance to breakage and abrasion and electrical properties. In addition, laboratory development models of the electronics will be used to operate two plasma motor generator hollow cathode assemblies with this tether to verify electrical performance parameters for the complete system. Results show that a low cost demonstration of a plasma motor generator tether system appears to be feasible by the middle of the 1990s.

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NASA NTRS1987

Power and charge dissipation from an electrodynamic tether

The Plasma Motor-Generator project utilizes the influence of the geomagnetic field on a conductive tether attached to a LEO spacecraft to provide a reversible conversion of orbital energy into electrical energy. The behavior of the current into the ionospheric plasma under the influence of the geomagnetic field is of significant experimental and theoretical interest. Theoretical calculations are reviewed which start from Maxwell's equations and treat the ionospheric plasma as a linear dielectric medium. These calculations show a charge emitting tether moving in a magnetic field will generate electromagnetic waves in the plasma which carry the charge in the direction of the magnetic field. The ratio of the tether's speed to the ion cyclotron frequency which is about 25 m for a LEO is a characteristic length for the phenomena. Whereas for the dimensions of the contact plasma much larger than this value the waves are the conventional Alfven waves, when the dimensions are comparable or smaller, diffraction effects occur similar to those associated with Fresnel diffraction in optics. The power required to excite these waves for a given tether current is used to estimate the impedance associated with this mode of charge dissipation.

Hite, Gerald E.↗
NASA NTRS1988

Study of Plasma Motor Generator (PMG) tether system for orbit reboost

A progress report is given on a system study by TRW begun in January 1987 of a 2 kW Plasma Motor Generator Tether to be used for orbit reboost. Following the completion of the initial phase in September 1987, additional tasks were agreed on and work on them begun in March 1988. These tasks fell into three categories: tests on the prototype tether fabricated during the first phase, simulations of the spacecraft and tether system after deployment using GTOSS, and a brief investigation of the impact and feasibility of increasing the system to 20 kW and hosting it on the Orbital Maneuvering Vehicle. The subcontractor, Energy Sciences Laboratory, was assigned the responsibility of performing the simulations and some mechanical tests on the prototype tether to supplement those done at TRW. A summary of the significant findings and issues from each task follows. Recommendations for future work constitutes the third section. A copy of the final briefing is in Appendix A, plus additional reports for each task and additional analysis.

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NASA NTRS1987

Plasma contactors for use with electrodynamic tethers for power generation

Plasma contactors have been proposed as a means of making good electrical contact between biased surfaces such as found at the ends of an electrodynamic tether and the space environment. A plasma contactor is a plasma source which emits a plasma cloud which facilitates the electrical connection. The physics of this plasma cloud is investigated for contactors used as electron collectors and it is shown that contactor clouds in space will consist of a spherical core possibly containing a shock wave. Outside of the core the cloud will expand anisotropically across the magnetic field leading to a turbulent cigar shape structure along the field. This outer region is itself divided into two regions by the ion response to the electric field. A two dimensional theory of the motion of the cloud across the magnetic field is developed. The current voltage characteristic of an Argon plasma contactor cloud is estimated for several ion currents in the range of 1-100 Amperes. It is shown that small ion current contactors are more efficient than large ion current contactors. This suggests that if a plasma contactor is used on an electrodynamic tether, then a multiple tether array will be more efficient than a single tether.

Hastings, D. E.↗
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

Comments on the 'early experimental validation' session of the Second International Conference on Tethers in Space

The paper summarizes the 'early experiment aspects' of the session which focused on the need for low cost, simple flight experiments to verify tether concepts, analysis methods and simulations and to build a data base for future application of tethers. The papers discussed six well thoughtout new space experiments, a modest start toward obtaining the data needed before tether concepts can be realistically expected to be adopted in real designs. Of the ninety-five papers included in the Venice conference, only six new small experiments were discussed. In-space verification of the data base needed to design operational tethers continues to be a step in the future.

Harris, Leonard A.↗
NASA NTRS1988

The tethered satellite electrodynamics experiment project

NASA and Italy's PSN have undertaken the Tethered Satellite Electrodynamics Experiment, in which two tethered bodies will be equipped with data-collecting scientific instruments, as the first stage of the development of the Tethered Satellite System that can be deployed by the Space Shuttle. The experiment will give attention to the electromagnetic interaction between the satellite/tether/orbiter system and the ambient space plasma, and should demonstrate the operation of both satellite- and Shuttle-borne electrodynamic instruments with a conductive tether.

Price, John M.↗
NASA NTRS1988

Alfven waves from an electrodynamic tethered satellite system

The ionospheric plasma currents associated with the operation of an orbiting, constant current electrodynamic tethered satellite system are calculated using linear cold plasma theory and a tethered system current distribution model that takes into account the peculiar dumbbell shape of the system. The field line current calculations show plasma sheet currents at each end of the tethered system whose structure is roughly that of the Alfven wings. The disturbance caused by the moving tethered system extends behind its dimensions along the line of sight. The form of the wings alters as they travel away from the system. The front boundary becomes sharper while the ripples in J(z) in the wake extend to greater distances with larger amplitude. The wave impedance is calculated for a wide range of system dimension values. The expression is in sharp disagreement with a recently published result by Dobrowolny and Veltri (1986).

Estes, Robert D.↗
NASA NTRS1987

Cosmic dust collection with a sub satellite tethered to a Space Station

The number concentration and density of 1 micron and submicron sized grains in interplanetary space, as well as their relation to the larger zodical dust particles, and the importance of the beta meteoroid phenomenon are currently being questioned. The best approach to collecting large numbers of intact micron and submicron sized cosmic dust particles in real time while avoiding terrestrial and man made contamination would be to employ a tethered subsatellite from a space station down into the earth's atmosphere. Such a subsatellite tied to the space shuttle by a 100 km long tether is being developed. It is also possible that a permanent space station would allow the use of a tether even longer than 100 km. It should be noted that the same tethered collectors could also be employed to study the composition and flux of man made earth orbiting debris in any direction within 100 km or so of the space station.

Corso, George J.↗
NASA NTRS1988

The use of the tethered satellite system to perform low density aerothermodynamics studies

The Tethered Satellite System (TSS) is a cooperative space system development activity of the U.S.A. and Italy. It is comprised of the Tether Satellite (TS) and the deployer. Within TSS, the Shuttle Tethered Aerothermodynamic Research Facility (STARFAC) concept has the potential to provide access to vast portions of the upper atmosphere for atmospheric and aerothermodynamic research. The feasibility and capability of the TSS to operate as a continuous open wind tunnel and to perform low density aerothermodynamic studies are investigated. This is accomplished through a modified version of the TS simulation program (SKYHOOK). The results indicate that STARFAC concept is both feasible and practical. The TS can go below 100 km but, if thrust is used, large velocity variation (delta V) maneuvers and an attitude control are required; if a satellite lift is considered, large tether tension is produced and an attitude control is required.

Carlomagno, Giovanni M.↗
NASA NTRS1989

Dynamics and control of the tether elevator/crawler system

This paper investigates the dynamics and acceleration levels of a new tethered system for micro- and variable-gravity applications. The system consists of two platforms tethered on opposite sides to the Space Station. A fourth platform, the elevator, is placed in between the Space Station and the upper platform. Variable-g levels on board the elevator are obtained by moving this facility along the upper tether, while microgravity experiments are carried out on board the Space Station. By controlling the length of the lower tether the position of the system center of mass can be maintained on board the Space Station despite variations of the system's distribution of mass. The paper illustrates the mathematical model, the environmental perturbations and the control techniques which have been adopted for the simulation and control of the system dynamics. Two sets of results from two different simulation runs are shown. The first set shows the system dynamics and the acceleration spectra on board the Space Station and the elevator during station-keeping. The second set of results demonstrates the capability of the elevator to attain a preselected g-level.

Lorenzini, E. C.↗
NASA NTRS1989

Tethered Satellite System-2 - A proposed program

A second mission (TSS-2) has been proposed for the reusable Tethered Satellite System (TSS) being developed jointly by the U.S. and Italy. The TSS-2 flight demonstration would use the TSS deployer/retriever system to deploy a research spacecraft attached to the end of a 100-km-long tether. The deployment would take place downward from the Space Shuttle into the outer atmosphere to an altitude of approximately 130 km. The objectives of the mission would be to demonstrate the atmospheric deployment of a tethered system, conduct scientific and aerothermodynamic research measurements, and conduct engineering measurements to verify flight system performance. Analytical studies have shown the feasibility of the TSS-2 mission from both the technology and operational dynamics standpoint. The TSS-1 mission (a 20 km tether deployed upward to conduct electrodynamic experiments) will validate the TSS itself as well as deployment and retrieval operations.

Anderson, John L.↗