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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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NASA NTRS2008

Electric Propulsion System Selection Process for Interplanetary Missions

The disparate design problems of selecting an electric propulsion system, launch vehicle, and flight time all have a significant impact on the cost and robustness of a mission. The effects of these system choices combine into a single optimization of the total mission cost, where the design constraint is a required spacecraft neutral (non-electric propulsion) mass. Cost-optimal systems are designed for a range of mass margins to examine how the optimal design varies with mass growth. The resulting cost-optimal designs are compared with results generated via mass optimization methods. Additional optimizations with continuous system parameters address the impact on mission cost due to discrete sets of launch vehicle, power, and specific impulse. The examined mission set comprises a near-Earth asteroid sample return, multiple main belt asteroid rendezvous, comet rendezvous, comet sample return, and a mission to Saturn.

Landau, Damon↗
NASA NTRS1993

First results of the seven-color asteroid survey

The new Seven-Color infrared filter system (SCAS), designed specifically to capture the essential mineralogical information present in asteroid spectra, is composed of seven broad-band filters which allow for IR observations of objects as faint as 17th magnitude. The first test of the SCAS system occurred in Jul. 1992. In four nights at the IRTF on Mauna Kea, Hawaii, over 67 objects were observed. Five of the observations were to test the new system for accuracy relative to previous observations with the high-resolution 52 Color Infrared Survey and with the Eight-Color Asteroid Survey (ECAS). In three cases, the match with previous data was good. In two cases, the match to previous observations was not as good. In addition, sixty S-Type asteroids were measured with the SCAS system. Forty of those asteroids were also observed with the ECAS system. Among the new observations is infrared data of 371 Bohemia, a main belt asteroid which was classified 'QSV' according to its UBV colors in the taxonomic system of D.J. Tholen. There are no corresponding ECAS data for 371. Q-type asteroids are of special interest as they are proposed to be the elusive parent bodies of the ordinary chondrite meteorites. Most Q-types are Earth-crossing asteroids and have not yet been observed in the infrared (except, perhaps, 371). Positive identification of a large main belt Q-type would be of major importance in the scheme of the geological structure of the asteroid belt. Without visible wavelength data, however, the classification of 371 Bohemia remains ambiguous. An attempt to conjoin Bohemia SCAS data with ECAS data of both a typical Q-Type asteroid and an average S-Type asteroid is shown. This figure thus illustrates the importance of visible wavelength data to the SCAS system. In other words, without ECAS data of 371 Bohemia we cannot use its spectral characteristics to identify it as a possible parent body of ordinary chondrite meteorites.

Clark, Beth E.↗
NASA NTRS1973

Radial pressure in the solar nebula as affecting the motions of planetesimals

Growing planetesimals and a range of drag laws depending on the Reynolds number and on the ratio of particle size to mean free path are considered. Particles spiral in the direction of positive gradient, thus being concentrated toward toroidal concentrations of gas. The effect increases with decreasing rates of particle growth, i.e., with increasing time scales of planet formation by accretion. In the outer regions, where evidence suggests that comets were formed and Uranus and Neptune were so accumulated, the effect of the pressure gradient is to clear the forming comets from those regions. The large mass of Neptune may have developed because of this effect, perhaps Neptune's solar distance was reduced from Bode's law, and perhaps no comet belt exists beyond Neptune. In the asteroid belt, on a slow time scale, the effect may have spiraled planetesimals toward Mars and Jupiter, thus contributing to the lack of planet formation in this region.

Whipple, F. L.↗
NASA NTRS1990

Comet nuclei and Trojan asteroids - A new link and a possible mechanism for comet splittings

Relatively elongated shapes, implied by recent evidence of a greater incidence of high amplitude lightcurves for comet nuclei and Trojan asteroids than for similarly scaled main belt asteroids, are suggested to have evolved among comet nuclei and Trojans due to volatile loss. It is further suggested that such an evolutionary course may account for observed comet splitting; rotational splitting may specifically occur as a result of evolution in the direction of an elongated shape through sublimation. Supporting these hypotheses, the few m/sec separation velocities projected for rotationally splitting elongated nuclei are precisely in the observed range.

Hartmann, William K.↗
NASA NTRS1992

JHK photometry of selected Trojan and Hilda asteroids

No entirely satisfactory match has been established between the present JHK photometry of selected Hilda and Trojan asteroids and photometry for both main belt asteroids and laboratory samples. It is noted that while the leading Trojans and Hildas exhibit similar and homogeneous JHK colors, the trailing Trojans appear to be more heterogeneous. Charcoal and magnetite provide the best match in terms of JHK colors.

Smith, Dale W.↗
NASA NTRS1995

The rotation state of 4015 Wilson-Harrington: Revisiting origins for the near-Earth asteroids

CCD photometry performed on the comet-asteroid transition object 4015 Wilson-Harrington during its most recent apparition has provided a new rotational lightcurve with a standard double-peaked rotational period of 6.1 +/- 0.05 hr and an amplitude of 0.2 magnitudes. The size, rotation period, and lightcurve amplitude of this object are all similar to values found for near-Earth asteroids (NEA) and small main-belt asteroids. However, these values vary significantly from those of any previously well-studied cometary nuclei. In short, the range in cometary nuclear properties is greater than that indicated by the comets studied previously and although the statistics are still poor, the size and rotational properties of 4015 Wilson-Harrington do suggest that some fraction of NEAs are of cometary origin.

Osip, DAVIDJ.↗
NASA NTRS2005

Detailed Mineralogical Characterizations of Four S-Asteroids: 138 Tolosa, 306 Unitas, 346 Hermentaria, and 480 Hansa

The S-asteroid taxonomic class is the second largest grouping of main-belt asteroids that are primarily located in the inner main belt (a < 3.0 AU) [1]. These asteroids have historically been the subject of interest within the asteroid community for several reasons. Continuing discussions about the nature of the S-asteroids (ordinary chondrite-like or thermally-evolved) and the putative space weathering effect on S-asteroids serve as examples of issues currently unresolved within the community [2,3]. Despite this general interest, detailed mineralogical investigations of individual S-asteroids has been relatively rare. A few workers have studied individual, or small groups of, S-asteroids [4,5,6,7]. Gaffey et al. [2] published their S-asteroid survey in 1993 that characterized 39 of the 144 then-classified S-asteroids. Despite the work already accomplished, the need exists to rigorously characterize the remaining S-asteroid population to gain a better understanding of these asteroids origin, nature, and physical characteristics.

Hardersen, P. S.↗
NASA NTRS1975

Asteroids - Spectral reflectance and color characteristics. II

New spectrophotometry for 31 asteroids, and improved data for nine previously observed, is presented, raising the total sample to 98. Several important new spectral types have been found. Asteroid 349 Dembowska is the first large main-belt asteroid found to resemble ordinary chondritic meteorites in spectral properties (it is similar to LL6 chondrites in pyroxene/olivine content). The first two measured Trojan asteroids show unusual spectra not compatible with carbonaceous chondrites or other known meteorites. The spectrum of Mars-crosser 887 Alinda is compatible with unequilibrated chondrites. Most fainter asteroids (especially those in the outer half of the belt) have flat spectra indicating probable carbonaceous composition. Compositional heterogeneity of Hirayama families is common among the 16 families studied to date. But individual asteroids seem to have remarkably uniform surface compositions, indicated by the usual lack of spectral changes with rotation. Spectra of a preliminary sample of proposed meteorite source-bodies are consistent with derivation of meteorites by proposed mechanisms, but further observations are needed.

Mccord, T. B.↗
NASA NTRS1991

Planetary astronomy

Many asteroids are known to be non-spherical, as revealed by changes in their brightness as they rotate (light curves) and present varying cross-sections to view. Models of collisional evolution of the asteroid belt suggest that many of the larger asteroids are shattered rubble piles, consisting of fragments bound together by gravity. If these assemblages are sufficiently weak, they should relax to equilibrium shapes that depend only on their spin periods and densities. Thus, if shape of an asteroid is known, one might infer its density and internal structure.

Chapman, C. R.↗
NASA NTRS2022

Noble Gases and Nitrogen in Samples of Asteroid Ryugu Record Its Volatile Sources and Recent Surface Evolution

The Hayabusa2 spacecraft retrieved surface and subsurface samples from the carbonaceous near-Earth asteroid (162173) Ryugu, which was expected to be enriched in volatile species. The samples were collected from two locations, one undisturbed surface and the other including material excavated by an artificial impact. Unlike meteorites, these samples have experienced minimal alteration by Earth’s atmosphere. Ryugu is thought to have formed from material ejected (by an impact) from a parent body, which had experienced aqueous alteration (reactions with liquid water) ~4.56 billion years (Gyr) ago. Ryugu’s orbit later migrated from the main asteroid belt to become a near-Earth asteroid.

volatile↗
NASA NTRS2012

Dawn's Exploration of Vesta

On 16 July 2011, after completing nearly four years of interplanetary flight, Dawn entered orbit around (4) Vesta, the second most massive body in the main asteroid belt. Dawn used solar electric propulsion to spiral to a series of six different orbits to accomplish its science campaign. Although the transfers to progressively lower orbits presented significant challenges, all were executed smoothly. During its nearly 14 months in orbit, Dawn spiraled down to 210 km above the surface and back up, before initiating the gradual departure to travel to dwarf planet (1) Ceres for a 2015 rendezvous. Dawn's exploration of Vesta has shown it to be geologically complex and fascinating, resembling terrestrial planets more than typical asteroids. Among the principal features is a 500-km diameter impact basin within which is the second tallest mountain known in the solar system. This paper presents Dawn's operations at Vesta and summarizes the principal findings.

ion propulsion↗
NASA NTRS1975

Surface properties of asteroids - A synthesis of polarimetry, radiometry, and spectrophotometry

Surface compositions of 110 asteroids are analyzed using data obtained by polarimetry and visible and near-IR spectrophotometry. A comparison of albedos and diameters determined by polarimetry and radiometry indicates that a slight upward revision of the radiometric albedo scale is necessary. Reliable adopted albedos and diameters are presented for 56 objects, and rough diameters are obtained for 52 additional objects. More than 90% of the asteroids are shown to fall into two broad groups (C and S) which are compositionally similar to carbonaceous and stony meteorites, respectively. C-type asteroids are found to predominate in the asteroid belt, and the largest of these (Ceres, Pallas, Hygiea, Davida) may be metamorphosed. It is shown that Vesta may be the only differentiated asteroid remaining intact in the belt. The results support the conclusions that asteroids and meteorites have similar classes of mineral assemblages, but the distribution of asteroid types contrasts with the distribution of major meteorite types found on earth.

Chapman, C. R.↗
NASA NTRS1979

The Palomar planet-crossing asteroid survey, 1973-1978

Photographic coverage of about 80,000 sq deg of sky with the Palomar 46-cm Schmidt camera has yielded 12 new planet-crossing asteroids as well as many objects in the main asteroid belt. The estimated population of planet-crossing asteroids includes approximately 100 Atens, 700 + or- 300 Apollos, 1000-2000 Amors, 10,000 + or- 5000 Mars crossers, and approximately 5000 Mars grazers.

Helin, E. F.↗
NASA NTRS1984

Mineralogical-petrological characterization of near-earth asteroids

The mineralogy and petrology of 17 near-earth asteroids are characterized using reflectance spectroscopy with ground-based telescopes. Assuming the surfaces are composed of cosmically abundant materials, the presence of certain mineralogical species can be determined from diagnostic absorption features and spectral characteristics which have been studied under known laboratory conditions and understood in terms of crystal-field theory. With one possible exception, the surface composition of near-earth asteroids consists of common rock-forming minerals such as olivine, pyroxene, and phyllosilicates. Opaque components are present but cannot be mineralogically identified with existing experimental data. The spectrum of 2201 Oljato cannot be interpreted in terms of common rock-forming minerals and is examined for cometary features because its high orbital eccentricity suggests a possible relation to comets, but no common cometary features are identified. The predominance of mafic silicate absorption features in spectra of near-earth asteroids (compared to the majority of main-belt asteroids) may be a primary compositional feature or may be the signature of relatively fresher asteroid material.

Mcfadden, L. A.↗
NASA NTRS1986

IRAS survey of asteroids

The Infrared Astronomical Satellite (IRAS) scanned the celestial sphere during 1983 through bandpasses centered at wavelengths of 12, 25, 60 and 100 microns. In addition to sources fixed on the sky, many moving objects were observed. This data set is the largest and least biased survey of asteroids and comets ever conducted. Included are main belt asteroids, Mars-crossers, earth-approachers, and Trojans. Measurements for the known asteroids have been reduced and organized into a number of data products which are available to researchers. The data for 'new' asteroids are being processed.

Matson, D. L.↗
NASA NTRS1993

Chondrites, S asteroids, and space weathering: Thumping noises from the coffin?

Most of the spectral characteristics of ordinary chondrites and S-asteroids in the visible and infrared can be reduced to three numerical values. These values represent the depth of the absorption band resulting from octahedrally coordinated Fe(sup 2+), the reflectance at 0.56 microns and the slope of the continuum (as measured according to convention). By plotting these three characteristics, it is possible to immediately compare the spectral characteristics of large numbers of ordinary chondrites and S-asteroids. Commonality of spectral characteristics between these populations can thus be evaluated on the basis of overlap in position on three two-coordinate systems: albedo vs. band depth, band depth vs. slope, and slope vs. albedo. In order to establish identity, members of the two populations must overlap on all three of these independent parameter spaces. In this coordinate system, spectra of 23 ordinary chondrites (representing all metamorphic grades), and 39 S-asteroids were compared. It was found that there was no overlap between the two populations in terms of the slope vs. band depth parameters, nor were most chondrites identical to the S-asteroids with respect to the other criteria. However, the controversial question remains: Where are the parent bodies of the chondrites? Perhaps an even more critical question is: Where are our samples of the S-asteroids? Considering the geography of the asteroid belt and the theory that early solar-system electromagnetic induction heating differentiated protoasteroids in the inner portion of the main belt, it was suggested that although S-asteroids and ordinary chondrites have very similar mineralogy, the S-asteroids are mixtures of metallic nickel iron and silicates which resulted from magmatism induced by electromagnetic heating whereas chondrites were only slightly metamorphosed nebular condensates. In this scenario chondrites would have been derived from a population of bodies with thermal lag times so short that they were not subjected to melting during the phase of the electromagnetic induction heating event but only to various degrees of pervasive metamorphism. Furthermore, these objects would then have been too small to be observed and systematically included in the library of asteroidal spectra. It was also suggested that the parametric distribution of S-asteroid spectra could be reproduced by mixing various proportions of NiFe meteorite and achondritic materials. This has also been demonstrated in the laboratory.

Fanale, F. P.↗
NASA NTRS2001

Announcing the Availability of the MIT SMASS and SMASSIR Data Sets

We announce the release of visible and near-infrared reflectance spectroscopy measurements for nearly 2000 asteroids obtained by the MIT Small Main-Belt Asteroid Spectroscopic Survey (SMASS) program. Data are being released via http://smass.mit.edu. Additional information is contained in the original extended abstract.

Binzel, R. P.↗