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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 415 records · Page 23

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NASA NTRS1986

Solar wind parameters and magnetospheric coupling studies

This paper presents distributions, means, and standard deviations of the fluxes of solar wind protons, momentum, and energy as observed near earth during the solar quiet and active years 1976 and 1979. Distributions of ratios of energies (Alfven Mach number, plasma beta) and distributions of interplanetary magnetic field orientations are also given. Finally, the uncertainties associated with the use of the libration point orbiting ISEE-3 spacecraft as a solar wind monitor are discussed.

King, Joseph H.↗

NASA NTRS1987

Orbits of the ten small satellites of Uranus

Orbital elements are presented for the ten small satellites discovered by Voyager 2 at Uranus. These ten new satellites, whose provisional IAU designations are 1985UI and 1986UI through 1986U9, lie for the most part in equatorial, circular orbits; the most notable exception is 1986U8, the outer epsilon-ring shepherd, whose eccentricity e = 0.0101. Unlike the Voyager discoveries at Saturn, which included two co-orbiting satellites and three librators, the ten small Uranian satellites all have quite different semimajor axes.

Owen, W. M., Jr.↗

NASA NTRS1988

Trajectory analysis of transfers between L4 and L5 and low lunar orbit

The flight characteristics and spacecraft performance during missions involving flight between the equilateral libration points and the Moon are discussed. The conclusions drawn will show that a minimum energy trajectory is the most efficient transfer technique for this type of flight.

Source record↗

NASA NTRS1989

The development of a cislunar space infrastructure

The primary objective of this Advanced Mission Design Program is to define the general characteristics and phased evolution of a near-Earth space infrastructure. The envisioned foundation includes a permanently manned, self-sustaining base on the lunar surface, a space station at the Libration Point between earth and the moon (L1), and a transportation system that anchors these elements to the Low Earth Orbit (LEO) station. The implementation of this conceptual design was carried out with the idea that the infrastructure is an important step in a larger plan to expand man's capabilities in space science and technology. Such expansion depends on low cost, reliable, and frequent access to space for those who wish to use the multiple benefits of this environment. The presence of a cislunar space infrastructure would greatly facilitate the staging of future planetary missions, as well as the full exploration of the lunar potential for science and industry. The rationale for, and a proposed detailed scenario in support of, the cislunar space infrastructure are discussed.

Buck, C. A.↗

NASA NTRS1988

Applying the OTV to lunar logistics

The Orbit Transfer Vehicle (OTV), representing the next generation of upper stages, has recently been studied in a Phase A concept definition study managed by NASA's Marshall Space Flight Center. The vehicle has been previously defined as strictly an orbit-to-orbit type transfer device. Recently its application to the task of lunar surface logistics was investigated. Transfer options to the surface were considered which included direct transfer, and transfer via lunar orbit as well as the L1 libration point. The subsystem modifications required to enable lunar landings were established for the following elements: aerobrake, main propulsion system, landing legs, primary structure, and avionics. It is concluded that the majority of the basic systems required for efficient transfer to the lunar surface are already contained in the OTV.

Willcockson, W. H.↗

NASA NTRS1988

Planet X and the stability of resonances in the Neptune-Pluto system

Four test orbits of a trans-Plutonian planet have been integrated forward for four million years in order to determine the effects of such a body on the stability of the Neptune-Pluto 3:2 resonance. Planets beyond Pluto with masses of 0.1 M and 1.0 Earth masses in orbits at 48.3 and 75.5 AU, respectively, do not disturb the 3:2 resonance. Test planets of 5 Earth masses with semimajor axes of 52.5 and 62.5 AU disrupt the four million year libration of Pluto's argument of perihelion.

Jackson, A. A.↗

NASA NTRS1989

Tidal evolution of the Uranian satellites. II - An explanation of the anomalously high orbital inclination of Miranda

It is proposed that the current, anomalously high orbital inclination of the Uranian satellite, Miranda, can be accounted for by temporary capture into the 3:1 resonance with Umbriel. This would imply that the orbits of the satellites have tidally evolved sufficiently to have permitted passage through this resonance. Escape from resonance is suggested to have occurred by way of a novel dynamical mechanism, in which the trajectory encounters low-order commensurabilities between the libration frequency of the resonant argument and other fundamental system frequencies.

Tittemore, William C.↗

NASA NTRS1989

The figure of Phobos

The figure of Phobos is presently modeled by a sixth-degree-and-order spherical harmonic expansion that fits the observed surface to an accuracy of a few hundred m, as validated through the use of control points, limbs, terminators, map projections, and predicted rotational properties. Only the region around the large crater, Stickney, exhibits lower accuracy. The forced libration amplitude obtained closely matches the observed value; this supports the view of Phobos as possessing a uniform density distribution.

Duxbury, Thomas C.↗

NASA NTRS1989

The gravitational field of Phobos

The external gravitational field produced by a rigid body of uniform density but irregular shape is formulated in terms of spherical harmonics. The formalism is applied to the Martian satellite Phobos. Based on a three-dimensional shape model of Phobos by Duxbury (1989), the gravitational coefficients up to degree and order 4 for a homogeneous Phobos are computed. In particular, J2 is found to be 0.105. The in-plane libration amplitude of a homogeneous Phobos is predicted to be 0.97 deg, within the rather large uncertainty of the observed value of 0.78 + or - 0.4 deg.

Chao, B. Fong↗

NASA NTRS1990

TV observations of Phobos - First results

From February to March, 1989, Phobos-2 acquired 37 TV images of Phobos at distances from 200 to 1100 km. These images will be used to update the figure model and topographic and geological maps of Phobos, its spectral characteristics and scattering law, the surface composition and texture, and the parameters of the orbital motion and forced libration.

Avanesov, G. A.↗

NASA NTRS1989

Orbital mechanics and mission design; Proceedings of the AAS/NASA International Symposium, Greenbelt, MD, Apr. 24-27, 1989

The present conference discusses topics in LEO mechanics, the earth-sun-moon orbital regime, space navigation, and lunar and planetary missions. Attention is given to an improved technique for passive eccentricity control, H-I launch vehicle mission planning, glideslope approaches, the control of Space Station-based tethered systems, rendezvous operations in GEO, launch-window expansion and trajectory correction for the First Lunar Swingby, the nature of lunar gravity assists, and the numerical determination of libration-point trajectories with solar exclusion zone-avoiding out-of-plane maneuvers. Also discussed are the interferometric tracking of multiple spacecraft, an improved determination of Martian satellite orbits, the Magellan Venus Mapping Mission, the Mars Rover Sample Return Mission, round-trip trajectories for manned Mars exploration, advanced missions using fusion propulsion, Vesta trajectories and navigation, and Voyager interstellar mission design.

Teles, Jerome↗

NASA NTRS1990

Minimum fuel trajectories for a low-thrust power-limited mission to the moon and to Lagrange points L4 and L5

Minimum fuel trajectories from a low earth parking orbit to Lagrange points L4 or L5 and to the moon are obtained for a low-thrust limited-power spacecraft, with thrust acceleration levels of the order of 0.001 G. The procedure to find a trajectory to the libration point starts from an analytical description of a slightly elliptical spiral, given by Breakwell and Rauch. The earth moon trajectory is found by matching an earth spiral to a moon spiral on the sphere of influence. Earth oblateness effect is considered.

Breakwell, John V.↗

NASA NTRS1990

First evaluation of the main parameters in the dynamics of the Small Expendable Deployer System (SEDS) for a tethered satellite

The dynamics of the motion of the Small Expendable Deployer System (SEDS) is studied by using a simplified model in which no external forces (except the gravity gradient field) are applied on the tethered body and the tether is assumed massless. The dynamics of SEDS operation is modeled as a sequence of two phases: the deployment phase and the swing phase. For the first one the velocity dependent forces are found to force the tether forward from the local vertical. When the deployment ends, Coriolis effects vanish and the swing phase begins, which is characterized by a wide free libration. The time duration as well as velocity, acceleration and tension of the tethered body are estimated for both deployment and swing phases.

Deluca, Luigi↗

NASA NTRS1991

The 1990 MB: The first Mars Trojan

Asteroid 1990 MB was discovered by D. H. Levy and H. E. Holt during the course of the Mars and Earth Crossing Asteroid and Comet Survey. An orbit based on a 9 day arc and the asteroid's location near Mars' L5 (trailing Lagrangean) longitude led E. Boswell to speculate that it might be in 1:1 resonance with Mars, analogous to the Trojan asteroids of Jupiter. Subsequent observations strengthened the possibility, and later calculations confirmed it. Thus 1990 MB is the first known asteroid in 1:1 resonance with a planet other than Jupiter. The existence of 1990 MB (a small body most likely between 2 and 4 km in diameter) provides remarkable confirmation of computer simulations. These self consistent n-body simulations demonstrated this sort of stability for Trojans of all the terrestrial planets over at least a 2 million year time base. The discovery of 1990 MB suggests that others of similar or smaller diameter may be found. Using hypothetical populations of Mars Trojans, their possible sky plane distributions were modeled as a first step in undertaking a systematic observational search of Mars' L4 and L5 libration regions.

Innanen, Kimmo A.↗

NASA NTRS1989

Some unsolved problems in evolutionary dynamics in the solar system

Several unsolved problems in the evolutionary histories leading to current dynamical configurations of the planets and their systems of satellites are discussed. These include the possibilities of rather tight constraints on the primordial rotation states of Mercury and Venus and the stabilizing mechanism for the latter's retrograde spin, a brief mention of the problem of origin of the moons of earth and Mars, the excessive heat flow from Jupiter's satellite Io which is not compatible with an otherwise self-consistent model of origin of the Laplace three-body libration, the mechanism for the long history of resurfacing of Saturn's satellite Enceladus and the possibly short lifetime of the A ring and the mechanisms for resurfacing the satellites of Uranus, especially Ariel, if the high stability of the mean motion orbital resonances at the 2/1 commensurability involving Ariel and Umbriel precludes a long term occupancy of the resonance. Finally, excessive times of accumulation of the outer planets in current models may possibly be reducible from the effects of nebular gas drag.

Peale, S. J.↗

NASA NTRS1990

Microwave and optical lunar transponders

The scientific areas which used data from the Lunar Laser Ranging Experiment, collected from measurements to the Apollo 11, 14, and 15 and Lunakhod 2, include lunar science (i.e., studies of variations in the lunar angular orientation from that for uniform rotation, lunar tidal displacements, and the lunar mass distribution), geodynamics, astrometry, and gravitational physics. This paper argues that the placement of microwave and optical transponders on the moon would improve the accuracy of laser range measurements by nearly two orders of magnitude and would simplify the measurements. The K-band microwave transponders would be operated at the lunar base and at two remote sites on the moon surface, yielding much improved lunar libration and tidal displacement measurements. A two-wavelength laser transponder also would be operated at the lunar base, allowing accurate tropospheric propagation corrections to be made. This would introduce major improvements in measurements of the lunar orbit and of the earth's rotation, and in tests of general relativity.

Bender, P. L.↗

NASA NTRS1991

Rotational properties of planetary satellites

Properties of satellite rotation that are observable in principle, include the rotation period, the orientation of the spin axis relative to the orbit plane, precession of the spin axis due to gravitational torques, nonprincipal axis rotation or wobble, and deviations from uniform principle axis rotation or libration. Considerable order is observed in current satellite rotation states, and it is of interest to ascertain how this order came about and why some satellites do not conform to the dominant norm. There is a strong coupling between the spin and orbital motions that is primarily responsible for maintaining the ordered rotation states in most cases, but this coupling is equally responsible for destroying any chance of orderly rotation for Saturn's satellite Hyperion. Understanding the processes which constrain current rotation states as well as those of an evolutionary nature which could have brought the individual satellites to their observed rotation and orbit states allows us to sometimes infer interior properties of some satellite or even of its primary planet, although, attempts to deduce primordial rotation states are usually frustrated. The observed rotational properties of the planetary satellites are summarized, and the understanding of the processes maintaining and those leading to the observed states are outlined. Some of the inferences that can be drawn about intrinsic properties of the bodies themselves are indicated.

Peale, S. J.↗

NASA NTRS1991

International Cometary Explorer (ICE)

The primary mission objectives of the International Cometary Explorer (ICE) Comet Mission are to determine the composition and physical state of the Giacobini-Zinner Comet's nucleus; to determine the processes that governs the composition and distribution of neutral and ionized species in the cometary atmosphere; and to investigate the interaction between the solar wind and the cometary atmosphere. The spacecraft was in a halo orbit around the Sun-Earth libration point until it was moved 10 Jun. 1982 to the Earth's Geomagnetic Tail (GT). The spacecraft reached the GT in Jan. 1983 and remained there until Dec. 1983, at which time a lunar swing-by placed the spacecraft in a trajectory heliocentric orbit which encountered the comet Giacobini-Zinner in Sep. 1985. The spacecraft provided observations of solar wind upstream of Halley's Comet in 1986. Information is presented in tabular form and includes the following areas: Deep Space Network support, frequency assignments, telemetry, command, and tracking support responsibilities.

Wales, R.↗