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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 397 records · Page 22
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NASA NTRS1984

Trajectories and orbital maneuvers for the ISEE-3/ICE comet mission

The ISEE-3/ICE spacecraft, (launched in 1978), and expected to obtain the first measurements of comet Giacobinni-Zinner in September 1985, has undertaken a combination of propulsive maneuvers, lunar swing-bys, and solar perturbations to produce its present trajectory profile. ISEE-3 is a drum-shaped, spin-stabilized spacecraft equipped with a redundant pair of high-resolution sun sensors, a medium-gain S-band antenna, a hydrazine propulsion system and a science experiment payload. After being placed into a sun-earth libration halo orbit in late 1978, ISEE-3 was retargeted to the geomagnetotail in mid-1982 and became the first spacecraft to explore the geomagnetic tail between 80 and 237 earth radii in 1983. These types of maneuvers may prove important for future scientific missions planned as follow-ons to ISEE-3/ICE, such as a joint NASA/ISAS project spacecraft scheduled for Shuttle launch in 1991, and a possible encounter with two comets in 1996 anad 1998.

Farquhar, R.↗
NASA NTRS1984

The size of the lunar core

A 0.2 arc second phase shift in the 18.6 year forced precession of the lunar figure was inferred from analysis of lunar laser ranging data. The source of the phase shift is either viscous friction at a lunar core mantle boundary or solid friction caused by tidal flexing of the Moon by the Earth. Core mantle viscous coupling will explain the signature if the core radius R sub c approximately equals 330 km. On the other hand, solid friction can account for the signature only if the lunar solid friction 0 approximately equals 30 is abnormally small compared with that observed for, say, Mars (approximately equals 100 - 200). Although the inferred core radius is certainly within the limits imposed by the Apollo seismic experiment, it is significantly smaller than estimates of order 400-500 km from electromagnetic sounding. How accurate is the estimate of the R sub c derived from the phase shift? The effect of uncertainties in the frictional coupling mechanism, core density and ellipticity on the inferred core radius are discussed. The excitation of lunar free librations by core turbulence vis-a-vis other mechanisms (e.g., cometary or asteroidal impacts) and the influence of changes in lunar precession in the past on lunar dynamo generation are also examined.

Yoder, C. F.↗
NASA NTRS1985

Transportation Applications, Part 1

The applications of tethers in support of space transportation is divided into: (1) orbit transfer, momentum transfer release/rendezvous (hanging, swinging, and spinning) and simplified docking; (2) orbit maintenance: electrodynamic thrust in or out of plane, electrodynamic libration pumping or damping, momentum scavenging, and isolate thruster exhaust; and (3) transfer within constellation: deployment or retrieval of whole constellation, clothesline loop, hoist, tram for travel on the tether, monkey between the tethers, and power and fluid transfer.

Carroll, J.↗
NASA NTRS1985

Small Solar System Bodies

The feasibility of using ranging data to a spacecraft lander on a synchronously rotating satellite to determine the satellite's orbit, the planet's orbit, the lander coordinates, and the principal term of forced physical librations was studied. Classifications of asteroids into their proper elements and families are also presented. Measurements and reduction of positions on comets and the minor planets with less common orbits was the focus for the astrometry program.

Williams, J. G.↗
NASA NTRS1985

Orbital Resonances and Planetary Accretion in the Solar Nebula

Planetesimal orbital evolution in a resisting medium near an accreting protoplanet was studied to explore mechanisms for capture into Trojan and satellite orbits. Various mechanisms for capture into libration were proposed, e.g., increase in Jupiter/Sun mass ratio, change in Jovian orbital radius, and collisions of asteroids with interplanetary dust. Studies include effects of solar nebula gas drag on orbital evolution. In general, the gas deviates from Keplerian motion, causing secular decay of planetesimal orbits, as well as damping eccentricity. The motion of bodies near Jupiter under the effect of a resisting medium was numerically explored. The equations of motion were integrated using the formalism of the planar restricted three body problem, modified to include effects by gas drag and a growing Jupiter.

Weidenschilling, S. J.↗
NASA NTRS1985

Vibration/Libration Interaction Dynamics During the Orbiter Based Deployment of Flexible Members

Essential features of a general formulation for studying librational dynamics of a large class of spacecraft during deployment of flexible members are reviewed. The formulation is applicable to a variety of missions ranging from deployment of antennas, booms and solar panels to manufacturing of trusses for space platforms using the space shuttle. The governing nonlinear, non-autonomous and coupled equations of motion are extremely difficult to solve even with the help of a computer, not to mention the cost involved. To get some appreciation as to the complex interactions between flexibility, deployment and attitude dynamics as well as to help pursue stability and control analysis, the equations are linearized about their nominal deflected equilibrium configuration. The procedure is applied to the Space Shuttle based deployment of boom and plate-like members. Results suggest substantial influence of the inertia parameter, flexural rigidity of the appendages, orbit eccentricity, deployment velocity, initial conditions, etc. on the system response. The results should prove useful in planning of the Orbiter based experiments aimed at assessing effectiveness of procedures for studying dynamics and control of flexible orbiting members.

Modi, V. J.↗
NASA NTRS1984

Through the tail of a comet

The instrumentation, trajectory, and missions of the ISEE-3 spacecraft being sent to observe Comet Giacobini-Zimmer (GZ) are described. Originally parked at a libration point to observe the solar wind, ISEE-3 was directed to perform a complex series of flybys of the earth and the moon to move to a trajectory that will intersect the GZ tail in 1985. Renamed ICE, the spacecraft will record magnetic field and charged particle data on the interaction of the cometary tail with the solar wind.

Mclaughlin, W. I.↗
NASA NTRS1984

The rotation of Hyperion

For almost the entire range of dimensions of Hyperion allowed by uncertainties in the observations, the satellite cannot librate stably about a rotation rate which is synchronous with its orbital mean motion. Rather, the large gravitational torques on the asymmetric satellite coupled with the large eccentricity forced by the orbital resonance with Titan cause Hyperion to tumble in a random manner. Large changes in orientation of body axes relative to inertial space and in the instantaneous spin rate occur on timescales of the order of the orbit period. Numerical evaluation of the exponential divergence of nearby trajectories in the phase space of the motion verifies that the tumbling is truly chaotic. This newly defined state of chaotic rotation for Hyperion is likely to be the only example of confined, continuously observable chaotic motion in the solar system.

Peale, S. J.↗
NASA NTRS1986

Effects of damping on the control dynamics of the space shuttle based on tethered systems

The analysis of the effects of damping on the control dynamics of the space shuttle based on tethered systems suggest that a relatively simple point mass model can provide useful information concering librational dynamics during development and retrieval of the tethered satellites. The results show that a nonlinear tension control strategy in conjunction with a suitable choice of gains and realistic damping can lead to stable retrieval maneuver with amplitudes in pitch and roll limited to acceptable values. Longitudinal and lateral vibrations of the tether are strongly coupled and can lead to the slackening of the tether. Tether vibrations can be controlled quite effectively by speeding up the retrieval at smaller tether length and/or using thruster.

Modi, V. J.↗
NASA NTRS1986

Roles for tethers on an evolving space station

A scenario was developed for evolution of space station tether capabilities. As tether imposed constaints on station developments and operations were minimized, maximum benefits were derived from a mutually compatible combination of: (1)electrodynamic tethers for power, thrust, and libration control; (2)momentum transfer operations involving the STS or upper stages; (3)aeromaneuvering devices for space station orbital plan change; and (4)tethered constellations and tether/free-flyer combinations. Some concepts determined for advance tether facilities orbiting the moon: (1)stationkeeping deltaVs to stay in precise equatorial or polar orbits; (2)ratio of facility mass to maximum payload mass (surface-orbit-escape); (3)electric-thruster power requirements and maximum rendezvous frequencies; and (4)overall capabilities and major constraints on such facilities.

Carroll, J. A.↗
NASA NTRS1986

Tether fundamentals

Some fundamental aspects of tethers are presented and briefly discussed. The effects of gravity gradients, dumbbell libration in circular orbits, tether control strategies and impact hazards for tethers are among those fundamentals. Also considered are aerodynamic drag, constraints in momentum transfer applications and constraints with permanently deployed tethers. The theoretical feasibility of these concepts are reviewed.

Carroll, J. A.↗
NASA NTRS1986

Transportation

A summary of tether transportation is given. Four steps were used over a period of time. First, theoretical engineering feasibility and technology requirements were determined. Then the survivors of that effort went into step two in the analysis of promising candidates. Those survivors went into the third phase which is engineering design and cost benefits. Survivors entered into the demonstration mission definition phase. Transportation studies have covered two kinds of deployments. First, steady state deployment was studied. Like the TSS, it's nearly vertical. It takes a long time to deploy and involves relatively high tether tension. Secondly, dynamic deployment was studied. Deployment started in an almost horizontal direction under a very shallow angle which allows a high deployment rate under very low tension. Momentum transfer here occurs by libration. Specific payloads were used to study tethered transportation benefits. Four transportation concepts were studied with regard to cost benefits. A tethered orbiter deboost from the space station, an OTV boost up from the Space Station, a science platform on a tether with a possible micro-g lab moving in between platform and station, and a tethered boost of payloads fromthe orbiter are the four concepts. These benefits are examined in detail.

Vontiesenhausen, G.↗
NASA NTRS1986

The outer solar system for 200 million years

A special-purpose computer is used to integrate the orbits of the outer five planets for more than 100 Myr into the future and more than 100 Myr into the past. The strongest features in the Fourier transforms of the orbital elements of the Jovian planets can be identified with the frequencies predicted by linear secular theory. Many of the weaker features in the Fourier spectra are identified as linear combinations of the basic frequencies. Serious differences are noted between the present measurements and the predictions of Bretagnon (1974). The amplitude of the 3.796 Myr period libration of Pluto's longitude of perihelion is modulated with a period of 34 Myr. Very long periods, on the order of 137 Myr, are also seen. The orbit of Pluto is stable for the duration of the integration; the maximum Liapunov characteristic exponent is less than 10 to the -6.8 power/yr.

Applegate, J. H.↗
NASA NTRS1985

Guidebook for analysis of tether applications

This guidebook is intended as a tool to facilitate initial analyses of proposed tether applications in space. Topics disscussed include: orbit and orbit transfer equations; orbital perturbations; aerodynamic drag; thermal balance; micrometeoroids; gravity gradient effects; tether control strategies; momentum transfer; orbit transfer by tethered release/rendezvous; impact hazards for tethers; electrodynamic tether principles; and electrodynamic libration control issues.

Carroll, J. A.↗
NASA NTRS1986

Earth vicinity trades and options

The options for recovering a returned manned Mars spacecraft are surveyed. Earth parking orbits from libration point to low circular are discussed, with a 500 km perigee, 24 hour period elliptical orbit chosen as a baseline for further calculation. Several techniques for recovering up to 100 metric tons of returned spacecraft are investigated, including recovery by a low Earth orbit (LEO) based orbit transfer vehicle (OTV) pushing the spacecraft to LEO, and OTV transporting and aerobrake to the spacecraft, and an OTV delivering propellant to the spacecraft. Methods utilizing OTVs results in less total mass in LEO, but may not be the minimum cost solutions if significant development and testing are required.

William R Stump↗
NASA NTRS1986

Dynamics During Thrust Maneuvers of Flexible Spinning Satellites with Axial and Radial Booms

The dynamic response to operational maneuvers of spinning symmetric spacecraft with radial and axial booms was analyzed as part of the prelaunch dynamic analysis of the ISEE-3 spacecraft placed in a halo orbit around an Earth-Sun libration point, and later renamed ICE when it was directed to fly-by comet Giacobini-Zinner. The results presented use simple spacecraft models, and frequently give predictions that are good and easily obtained when the results from using a general purpose multibody dynamics program were very time consuming to obtain. Deployment of radial booms, spin-up after partial deployment, stationkeeping, and trajectory changes are analyzed. The latter two can involve both axial thrusting and pulsed radial thrusting once per revolution.

Longman, R. W.↗
NASA NTRS1987

Dynamic analysis of satellites with deployable hinged appendages

The nonlinear equations of motion determining the planar dynamical behavior of an orbiting satellite deploying both one and two rigid appendages have been formulated using Lagrange's equations. The analysis accounts for large angle rotations, Coriolis effects, and the gravitational gradient, and the resulting coupled governing equations are integrated numerically. The analysis is applied to the Space Shuttle based deployment of rigid truss-like members, and results show that spacecraft inertia parameters, appendage mass and length, deployment velocity, and initial conditions all influence the system response. It is found that the resulting librational movement is related to the size of the deployment payload, and that gravitational forces lead to vehicle stabilization.

Oakes, Kevin F.↗
NASA NTRS1986

Environmental control and life support technologies for advanced manned space missions

Regenerative environmental control and life support system (ECLSS) technologies are found by the present evaluation to have reached a degree of maturity that recommends their application to long duration manned missions. The missions for which regenerative ECLSSs are attractive in virtue of the need to avoid expendables and resupply requirements have been identified as that of the long duration LEO Space Station, long duration stays at GEO, a permanently manned lunar base (or colony), manned platforms located at the earth-moon libration points L4 or L5, a Mars mission, deep space exploration, and asteroid exploration. A comparison is made between nonregenerative and regenerative ECLSSs in the cases of 10 essential functions.

Powell, F. T.↗