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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Organic solids produced from simple C/H/O/N ices by charged particles - Applications to the outer solar system

The effects of charged particle irradiation by cold plasma discharge on surfaces of H2O:CH4 clathrate with a 200:1 ratio and on ices composed of H2O and C2H6 or C2H2 are examined. The molecules studies are found in Comet Halley and are plausible constituents in icy outer solar system objects. The IR transmission spectra of four ice-tholin residues obtained in the laboratory are compared with spectra produced by irradiation of gases and ices containing simple hydrocarbons. The similarities between CH4 clathrate residue and Halley organic grains, and the surface transport or atmospheric replenishment activity on Triton and Pluto are discussed.

Khare, B. N.↗
NASA NTRS1989

Origin and evolution of outer solar system atmospheres

The origin and evolution of the atmospheres of bodies in the outer solar system is studied on the basis of the abundances of key molecular species. Formation models in which significant infall of icy and rocky planetesimals accompanies planet formation is supported by the enrichment of methane and deuterated species from Jupiter and Neptune. The chemistry of the solar nebula and Titan are discussed. The prospects for obtaining information on the atmosphere of Triton from the Voyager 2 mission are considered. It is found that the mean density of the Pluto-Charon system implies an origin in the rather water-poor solar nebula.

Lunine, J. I.↗
NASA NTRS1990

Optical constants of solid methane

Methane is the most abundant simple organic molecule in the outer solar system bodies. In addition to being a gaseous constituent of the atmospheres of the Jovian planets and Titan, it is present in the solid form as a constituent of icy surfaces such as those of Triton and Pluto, and as cloud condensate in the atmospheres of Titan, Uranus, and Neptune. It is expected in the liquid form as a constituent of the ocean of Titan. Cometary ices also contain solid methane. The optical constants for both solid and liquid phases of CH4 for a wide temperature range are needed for radiative transfer calculations, for studies of reflection from surfaces, and for modeling of emission in the far infrared and microwave regions. The astronomically important visual to near infrared measurements of solid methane optical constants are conspicuously absent from the literature. Preliminary results are presented on the optical constants of solid methane for the 0.4 to 2.6 micrometer region. Deposition onto a substrate at 10 K produces glassy (semi-amorphous) material. Annealing this material at approximately 33 K for approximately 1 hour results in a crystalline material as seen by sharper, more structured bands and negligible background extinction due to scattering. The constant k is reported for both the amorphous and the crystalline (annealed) states. Typical values (at absorption maxima) are in the .001 to .0001 range. Below lambda = 1.1 micrometers the bands are too weak to be detected by transmission through the films less than or equal to 215 micrometers in thickness, employed in the studies to date. Using previously measured values of the real part of the refractive index, n, of liquid methane at 110 K, n is computed for solid methane using the Lorentz-Lorenz relationship. Work is in progress to extend the measurements of optical constants n and k for liquid and solid to both shorter and longer wavelengths, eventually providing a complete optical constants database for condensed CH4.

Khare, Bishun N.↗
NASA NTRS1989

Nuclear propulsion - A vital technology for the exploration of Mars and the planets beyond

The physics and technology issues and performance potential of various direct thrust fission and fusion propulsion concepts are examined. Next to chemical propulsion the solid core fission thermal rocket (SCR) is the only other concept to be experimentally tested at the power (approx 1.5 to 5.0 GW) and thrust levels (approx 0.33 to 1.11 MN) required for manned Mars missions. With a specific impulse of approx 850 s, the SCR can perform various near-earth, cislunar and interplanetary missions with lower mass and cost requirements than its chemical counterpart. The gas core fission thermal rocket, with a specific power and impulse of approx 50 kW/kg and 5000 s offers the potential for quick courier trips to Mars (of about 80 days) or longer duration exploration cargo missions (lasting about 280 days) with starting masses of about 1000 m tons. Convenient transportation to the outer Solar System will require the development of magnetic and inertial fusion rockets (IFRs). Possessing specific powers and impulses of approx 100 kW/kg and 200-300 kilosecs, IFRs will usher in the era of the true Solar System class spaceship. Even Pluto will be accessible with roundtrip times of less than 2 years and starting masses of about 1500 m tons.

Borowski, Stanley K.↗
NASA NTRS1990

The Oort cloud

Although the outermost planet, Pluto, is 6 x 10 to the 9th km from the sun, the sun's gravitational sphere of influence extends much further, out to about 2 x 10 to the 13th km. This space is occupied by the Oort cloud, comprising 10 to the 12th-10 to the 13th cometary nuclei, formed in the primordial solar nebula. Observations and computer modeling have contributed to a detailed understanding of the structure and dynamics of the cloud, which is thought to be the source of the long-period comets and possibly comet showers.

Wessman, Paul R.↗
NASA NTRS1990

An approximation to the outer planet ephemeris errors in JPL's DE 200

The outer planet positions of JPL's recent planetary ephemeris, DE 202, have begun to show significant differences from DE 200, the basic ephemeris of the major national almanacs. The differences DE 202 - DE 200 are plotted and are assumed to approximate the errors of DE 200. For Jupiter, the difference in right ascension varies over the planet's 12 yr period between -0.1 and -0.2 arcsec throughout the century; for Saturn, the right ascension also varies over the 30 yr period, but in addition, shows a drift which reaches -0.25 arcsec at present; for Uranus, the difference is small through the first half of the century, but now has reached -0.4 arcsec; for Neptune, the error was +0.6 arcsec at 1900 and is near -1.0 arcsec by the year 2000; the error for Pluto exceeds +2.0 arcsec by the end of the century and is rapidly increasing. The declination errors are generally periodic and smaller than the right ascensions.

Standish, E. M., Jr.↗
NASA NTRS1990

Automated design of multiple encounter gravity-assist trajectories

Given a range of initial launch dates and a set of target planets, a new approach to planetary mission design is developed, using an automated method for finding all conic solutions. Each point on the diagrams reproduced represents a single ballistic trajectory and is computed by modeling the trajectory as a conic section and solving the corresponding Lambert problem for each set of launch and arrival dates. An example which prescribes a launch period of 1975-2050 and target planets Uranus, Saturn, Jupiter, Neptune and Pluto is described whereby, all possible grand tour missions of this class are found, including the Voyager II trajectory. It is determined that this automated design tool may be applied to a variety of multiple encounter gravity-assist trajectories that are being considered for future missions.

Longuski, James M.↗
NASA NTRS1989

Creation of fully vectorized FORTRAN code for integrating the movement of dust grains in interplanetary environments

The main objective is to improve the performance of a specific FORTRAN computer code from the Planetary Sciences Division of NASA/Johnson Space Center when used on a modern vectorizing supercomputer. The code is used to calculate orbits of dust grains that separate from comets and asteroids. This code accounts for influences of the sun and 8 planets (neglecting Pluto), solar wind, and solar light pressure including Poynting-Robertson drag. Calculations allow one to study the motion of these particles as they are influenced by the Earth or one of the other planets. Some of these particles become trapped just beyond the Earth for long periods of time. These integer period resonances vary from 3 orbits of the Earth and 2 orbits of the particles to as high as 14 to 13.

Colquitt, Walter↗
NASA NTRS1989

Optical constants of solid methane

Methane is the most abundant simple organic molecule in the outer solar system bodies. In addition to being a gaseous constituent of the atmospheres of the Jovian planets and Titan, it is present in the solid form as a constituent of icy surfaces such as those of Triton and Pluto, and as cloud condensate in the atmospheres of Titan, Uranus, and Neptune. It is expected in the liquid form as a constituent of the ocean of Titan. Cometary ices also contain solid methane. The optical constants for both solid and liquid phases of CH4 for a wide temperature range are needed for radiative transfer calculations, for studies of reflection from surfaces, and for modeling of emission in the far infrared and microwave regions. The astronomically important visual to near infrared measurements of solid methane optical constants are conspicuously absent from the literature. Preliminary results are presented of the optical constants of solid methane for the 0.4 to 2.6 micron region. K is reported for both the amorphous and the crystalline (annealed) states. Using the previously measured values of the real part of the refractive index, n, of liquid methane at 110 K n is computed for solid methane using the Lorentz-Lorentz relationship. Work is in progress to extend the measurements of optical constants n and k for liquid and solid to both shorter and longer wavelengths, eventually providing a complete optical constants database for condensed CH4.

Khare, Bishun N.↗
NASA NTRS1990

Evolutionary use of nuclear electric propulsion

Evolving new propulsion technologies through a rational and conscious effort to minimize development costs and program risks while maximizing the performance benefits is intuitively practical. A phased approach to the evolution of nuclear electric propulsion from use on planetary probes, to lunar cargo vehicles, and finally to manned Mars missions with a concomitant growth in technology is considered. Technology levels and system component makeup are discussed for nuclear power systems and both ion and magnetoplasmadynamic thrusters. Mission scenarios are described, which include analysis of a probe to Pluto, a lunar cargo mission, Martian split, all-up, and quick-trip mission options. Evolutionary progression of the use of NEP in such missions is discussed.

Hack, K. J.↗
NASA NTRS1991

The design of hypersonic waveriders for aero-assisted interplanetary trajectories

The aerodynamic performance of a vehicle designed to execute an aerogravity assisted maneuver, which combines a gravitational turn with a low-drag atmosphere pass, is examined. The advantage of the aerogravity assisted maneuver, as opposed to a more traditional gravity-assist trajectory, is that, through the use of a controlled atmospheric flight, nearly any deflection angle around a gravitating body can be realized. This holds the promise of providing extremely large values of Delta V. The success of such a maneuver depends on being able to design a vehicle which can execute sustained atmospheric flight at Mach numbers in the range of 50 - 100 with minimal drag losses. Some simple modeling is used to demonstrate design rules for the design of such vehicles, and to estimate the deterioration of their performance during the flight. Two sample aerogravity-assisted maneuvers are detailed, including a close solar approach requiring modest Delta V, and a sprint mission to Pluto.

Lewis, Mark J.↗
NASA NTRS1990

Future NASA mission applications of space nuclear power

Recent studies sponsored by NASA show a continuing need for space nuclear power. A recently completed study considered missions (such as a Jovian grand tour, a Uranus or Neptune orbiter and probe, and a Pluto flyby) that can only be done with nuclear power. There are also studies for missions beyond the outer boundaries of the solar system at distances of 100 to 1000 astronomical units. The NASA 90-day study on the Space Exploration Initiative identified a need for nuclear reactors to power lunar surface bases and radioisotope power sources for use in lunar or Martian rovers, as well as considering options for advanced, nuclear propulsion systems for human missions to Mars.

Bennett, Gary L.↗
NASA NTRS1991

Outer planet satellites

Recent findings on the outer-planet satellites are presented, with special consideration given to data on the rheologic properties of ice on icy satellites, the satellite surfaces and exogenic processes, cratering on dead cratered satellites, volcanism, and the interiors of outer-planet satellites. Particular attention is given to the state of Titan's surface and the properties of Triton, Pluto, and Charon.

Schenk, Paul M.↗
NASA NTRS1991

Planetary atmospheres

Data published between 1987 and 1990 on the compositions and properties of different planetary atmospheres are reviewed. The origins and the evolutions of atmospheres of the outer planets and of their moons are discussed, and the relationships among waves, axisymmetric circulation, and global-scale transports are examined. Particular attention is given to the features of thin atmospheres of Mercury, Io, Triton, Pluto, and the earth's moon.

Kahn, Ralph↗
NASA NTRS1991

The magnetospheres of the outer planets

Research on the magnetospheres of all of the outer planets including Jupiter, Uranus, Neptune, and Pluto is reviewed for the 1987-1990 time period. Particular attention is given to magnetospheric structure, plasma transport, Jovian aurora, Io and the plasma torus, Titan and its magnetospheric interactions, rings and dusty plasmas, magnetospheric convection, and satellite interactions.

Mcnutt, Ralph L., Jr.↗
NASA NTRS1991

Symplectic maps for the n-body problem

The present study generalizes the mapping method of Wisdom (1982) to encompass all gravitational n-body problems with a dominant central mass. The rationale for the generalized mapping method is discussed as well as details for the mapping for the n-body problem. Some refinements of the method are considered, and the relationship of the mapping method to other symplectic integration methods is shown. The method is used to compute the evolution of the outer planets for a billion years. The resulting evolution is compared to the 845 million year evolution of the outer planets performed on the Digital Orerry using standard numerical integration techniques. This calculation provides independent numerical confirmation of the result of Sussman and Wisdom (1988) that the motion of the planet Pluto is chaotic.

Wisdom, Jack↗
NASA NTRS1991

Infrared observations of solar system objects

This is an ongoing groundbased infrared study of solar system objects. This is a broadbased program with the overall objective of studying the spectral and physical properties of small solar system bodies. The work spans the entire solar system from a study of the mineralogy of Mercury, to several studies of asteroids, and to studies of Triton, Pluto, and Charon. From these studies, it is hoped that a better understanding of the origin and evolution of these bodies and how they fit into the context of the origin and evolution of the solar system as a whole will be gained.

Lebofsky, Larry A.↗