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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 NTRSDate not supplied

Accessing Icy Worlds using Lattice Confinement Fusion (LCF) Fast Fission

NASA proposed the Ocean Worlds Exploration Program to search for extraterrestrial life. The challenge is that up to 40 kilometer-thick ice must first be broken through to reach sub-surface oceans. These icy ocean worlds include Ceres, Europa, Enceladus, and Pluto. Each world may have a liquid water ocean beneath their ice crust. These oceans are likely heated by the parent planet’s tidal forces, or in the case of Pluto or Ceres, by residual radioactive decay. A robotic probe exploring the oceans beneath must either melt or bore through the ice crust first. Consequently, the proposed probe needs to contend with hydrostatic ice pressure, ice phase and density changes, then water pressure. Such a mission requires a small, but robust and long lived, electrical energy and heat source. Instead, we propose a novel, compact, scalable nuclear energy source using neither highly enriched uranium (HEU) nor 238Pu similar to the hybrid fusion-fission generator described by Forsley and Mosier-Boss. This nuclear energy source uses Lattice Confinement Fusion (LCF) neutrons to fast-fission thorium or depleted uranium where neither 232Th nor 238U isotopes are fissile

Theresa L Benyo↗
NASA NTRS2002

Polar Wander on Triton and Pluto Due to Volatile Migration

Polar wander may occur on Triton and Pluto because of volatile migration. Triton, with its low obliquity, can theoretically sublimate volatiles (mostly nitrogen) at the rate of approximately 10(exp 14) kilograms per year from the equatorial regions and deposit them at the poles. Assuming Triton to be rigid on the sublimation timescale, after approximately 10(exp 5) years the polar caps would become large enough to cancel the rotational flattening, with a total mass equivalent to a global layer approximately 120-250 m in depth. At this point the pole wanders about the tidal bulge axis, which is the line joining Triton and Neptune. Rotation about the bulge axis might be expected to disturb the leading side/trailing side cratering statistics. Because no such disturbance is observed, it may be that Triton's mantle viscosity is too high but its surface volatile inventory is too low to permit wander. On the other hand, its mantle viscosity might be low, so that any uncompensated cap load might be expected to wander toward the tidal bulge axis. In this case, the axis of wander passes through the equator from the leading side to the trailing side; rotation about this wander axis would not disturb the cratering statistics. Low-viscosity polar wander may explain the bright southern hemisphere: this is the pole which is wandering toward the equator. In any case the permanent polar caps may be geologically very young. Polar wander may possibly take place on Pluto, due to its obliquity oscillations and perihelion-pole geometry. However, Pluto is probably not experiencing any wander at present. The Sun has been shining strongly on the poles over the last half of the obliquity cycle, so that volatiles should migrate to the equator, stabilizing the planet against wander. Spacecraft missions to Triton and Pluto which measure the dynamical flattening could give information about the accumulation of volatiles at the poles. Such information is best obtained by measuring gravity and topography from orbiters, as was done for Mars with the highly successful Mars Global Surveyor.

Rubincam, David Parry↗
NASA NTRS1997

A Numerical Method for Calculating Stellar Occultation Light Curves from an Arbitrary Atmospheric Model

We present a method for speeding up numerical calculations of a light curve for a stellar occultation by a planetary atmosphere with an arbitrary atmospheric model that has spherical symmetry. This improved speed makes least-squares fitting for model parameters practical. Our method takes as input several sets of values for the first two radial derivatives of the refractivity at different values of model parameters, and interpolates to obtain the light curve at intermediate values of one or more model parameters. It was developed for small occulting bodies such as Pluto and Triton, but is applicable to planets of all sizes. We also present the results of a series of tests showing that our method calculates light curves that are correct to an accuracy of 10(exp -4) of the unocculted stellar flux. The test benchmarks are (i) an atmosphere with a l/r dependence of temperature, which yields an analytic solution for the light curve, (ii) an atmosphere that produces an exponential refraction angle, and (iii) a small-planet isothermal model. With our method, least-squares fits to noiseless data also converge to values of parameters with fractional errors of no more than 10(exp -4), with the largest errors occurring in small planets. These errors are well below the precision of the best stellar occultation data available. Fits to noisy data had formal errors consistent with the level of synthetic noise added to the light curve. We conclude: (i) one should interpolate refractivity derivatives and then form light curves from the interpolated values, rather than interpolating the light curves themselves; (ii) for the most accuracy, one must specify the atmospheric model for radii many scale heights above half light; and (iii) for atmospheres with smoothly varying refractivity with altitude, light curves can be sampled as coarsely as two points per scale height.

Chamberlain, D. M.↗
NASA NTRS2002

Outer Planet Exploration with Advanced Radioisotope Electric Propulsion

In response to a request by the NASA Deep Space Exploration Technology Program, NASA Glenn Research Center conducted a study to identify advanced technology options to perform a Pluto/Kuiper mission without depending on a 2004 Jupiter Gravity Assist, but still arriving before 2020. A concept using a direct trajectory with small, sub-kilowatt ion thrusters and Stirling radioisotope power systems was shown to allow the same or smaller launch vehicle class as the chemical 2004 baseline and allow a launch slip and still flyby in the 2014 to 2020 timeframe. With this promising result the study was expanded to use a radioisotope power source for small electrically propelled orbiter spacecraft for outer planet targets such as Uranus, Neptune, and Pluto.

Oleson, Steven↗
NASA NTRS2002

Solar System Dynamics

In these 18 years, the research has touched every major dynamical problem in the solar system, including: the effect of chaotic zones on the distribution of asteroids, the delivery of meteorites along chaotic pathways, the chaotic motion of Pluto, the chaotic motion of the outer planets and that of the whole solar system, the delivery of short period comets from the Kuiper belt, the tidal evolution of the Uranian arid Galilean satellites, the chaotic tumbling of Hyperion and other irregular satellites, the large chaotic variations of the obliquity of Mars, the evolution of the Earth-Moon system, and the resonant core- mantle dynamics of Earth and Venus. It has introduced new analytical and numerical tools that are in widespread use. Today, nearly every long-term integration of our solar system, its subsystems, and other solar systems uses algorithms that was invented. This research has all been primarily Supported by this sequence of PGG NASA grants. During this period published major investigations of tidal evolution of the Earth-Moon system and of the passage of the Earth and Venus through non-linear core-mantle resonances were completed. It has published a major innovation in symplectic algorithms: the symplectic corrector. A paper was completed on non-perturbative hydrostatic equilibrium.

Wisdom, Jack↗
NASA NTRS1973

Interaction of the solar wind with the outer planets.

The hypersonic analog for the interaction of the solar wind with Jupiter, Saturn, Uranus, Neptune, and Pluto is used to provide estimates of shock shapes and locations, as well as average magnetosheath and/or ionosheath properties for these planets. Several representative spacecraft flyby trajectories (designed for outer-planet 'Grand Tour' simulations) are superimposed upon a series of figures in order to provide estimates of potential plasma and field parameters which may be encountered. Consideration is given first to the possibility that several of these planets have intrinsic magnetic fields and, secondly, to the interaction of the solar wind directly on the ionosphere should there actually be no intrinsic field. Saturn and Pluto are chosen as examples of this latter case.

Dryer, M.↗
NASA NTRS1993

Visible Imaging on the Pluto Fast Flyby Mission

Objectives for visible imaging of the Pluto-Charon system, as prescribed by the Outer Planets Science Working Group, are to acquire (1) global observations (FOV of approximately 5000 IFOV's) at 1 km/line-pair for the purpose of characterizing surface morphology and geology, (2) global observations in 3-5 broadband colors at 5-10 km/line-pair for studies of surface properties and composition as it relates to morphology, and (3) selected observations at higher spatial resolution for study of surface processes. Several factors of the Pluto Fast Flyby mission make these difficult to achieve. These factors along with other aspects of the mission are discussed.

Malin, M. C.↗
NASA NTRS2004

Pluto-Charon: Infrared Reflectance from 3.6 to 8.0 Micrometers

We have measured the spectral reflectance of the Pluto-Charon pair at 3.6, 4.5, 5.8, and 8.0 micrometers with the Infrared Array Camera (IRAC) (G. G. Fazzio et al. Ap.J.Supp. 154, 10-17, 2004) on the Spitzer Space Telescope (STS), at eight different longitudes that cover a full rotation of the planet. STS does not have sufficient resolution to separate the light from the planet and the satellite. The image of the Pluto-Charon pair is clearly visible at each of the four wavelengths. We will discuss the spectral reflectance in terms of models that include the known components of Pluto and Charon s surfaces, and evidence for diurnal variations.

Cruikshank, Dale P.↗
NASA NTRS1974

Geodetic and dynamical properties of planets

The study of planetary dynamics and geodesy is a difficult subject. This is so, not simply because of the complexity of the interactions between several scientific disciplines, including geophysics, geology, geochemistry, seismology, celestial mechanics, radar astronomy, and meteoritics, but perhaps more fundamentally, because of a lack of data. Although it is true that the space age has brought about important new observational techniques, which are responsible in large part for the rapid developments in planetary science over the past decade, and although we should expect to see significant progress in the field over the next few years, it is still a sad fact that data will be severely limited for an indefinite period of time in the future. The basic problem is that we can observe and study, at present, only one planetary system in the universe. This system, our solar system, contains only four major planets, five terrestrial planets, where we are inclined to include the moon but exclude Pluto, and a fairly limited collection of debris, presumably left over from some inadequately understood formation process. Thus it is impossible to base the study of planets on a significant statistical sample.

J. D.. Anderson↗
NASA NTRS2010

Generating an Atmosphere

The presence of water ice on most of the large satellites of the outer planets was established many years ago through near-infrared observations with ground-based telescopes. Frozen carbon dioxide, sulfur dioxide, methane, nitrogen, and other molecular ices are also found in various combinations on inner planets such as Mars to bodies far beyond Pluto. Recent discoveries of ice varieties on some asteroids and sequestered in protected regions on Mercury and the Moon point to the near-universal distribution of frozen volatiles throughout the solar system.

Cruikshank, Dale P.↗
NASA NTRS2007

NASA's Discovery Program: Moving Toward the Edge (of the Solar System)

NASA's Planetary Science , Division sponsors a competitive program of small spacecraft missions with the goal of performing focused science investigations that complement NASA's larger planetary science explorations at relatively low cost. The goal of the Discovery program is to launch many smaller missions with fast development times to increase our understanding of the solar system by exploring the planets, dwarf planets, their moons, and small bodies such as comets and asteroids. Discovery missions are solicited from the broad planetary science community approximately every 2 years. Active missions within the Discovery program include several with direct scientific or engineering connections to potential future missions to the edge of the solar system and beyond. In addition to those in the Discovery program are the missions of the New Frontiers program. The first New Frontiers mission. is the New Horizons mission to Pluto, which will explore this 38-AU distant dwarf planet and potentially some Kuiper Belt objects beyond. The Discovery program's Dawn mission, when launched in mid-2007, will use ion drive as its primary propulsion system. Ion propulsion is one of only two technologies that appear feasible for early interstellar precursor missions with practical flight times. The Kepler mission will explore the structure and diversity of extrasolar planetary systems, with an emphasis on the detection of Earth-size planets around other stars. Kepler will survey nearby solar systems searching for planets that may fall within the habitable zone,' a region surrounding a star within which liquid water may exist on a planet's surface - an essential ingredient for life as we know it. With its open and competitive approach to mission selections, the Discovery program affords scientists the opportunity to propose missions to virtually any solar system destination. With its emphasis on science and proven openness to the use of new technologies such as ion propulsion, missions flown as part of the program will test out technologies needed for future very deep-space exploration and potentially take us to these difficult and distant destinations.

Johnson, Les↗
NASA NTRS2017

Dawn at Ceres: The First Exploration of the First Dwarf Planet

Dawn has conducted an extensive exploration of dwarf planet Ceres, the largest object between the Sun and Pluto that had not previously been visited by a spacecraft. Following its arrival at Ceres in March 2015, Dawn acquired all the planned data from four circular polar orbits ranging in altitude from 13,600 km to 385 km. After the successful conclusion of its primary mission in June 2016, Dawn's mission was extended, and new investigations, not previously considered, were conducted from three new orbits. The mission has provided a uniquely detailed view of the first dwarf planet discovered. The overall strategy for exploring Ceres was based strongly on the extremely successful 16 months of Vesta operations. Nevertheless, the loss of two of the spacecraft's four reaction wheels before arrival at Ceres necessitated some important changes in order to conserve hydrazine. These changes were so effective that Dawn has been able to operate beyond the expected end of life, acquiring significantly more data than planned. This paper describes Ceres operations in the primary and extended missions as well as some of the major findings there.

Rayman, Marc D.↗
NASA NTRS1991

The last grand tour opportunity to Pluto

An automated mission design program permits a thorough examination of gravity-assist trajectories such as the Voyager II flight to Jupiter, Saturn, Uranus and Neptune. The program is applied to the automated design of multiple encounter trajectories to the far outer planets. The most significant result is that the last four-planet grand tour opportunity occurs in 1996 and includes encounters with Jupiter, Uranus, Neptune and Pluto. Other mission designs include Jupiter and one or two other planets and have characteristically short flight times.

Longuski, J. M.↗
NASA NTRS1989

Origin and evolution of planetary and satellite atmospheres

The present volume on the origin and evolution of planet and satellite atmospheres discusses the chemistry of interstellar gas and grains, planetary accretion, cometary composition, the inventories of asteroid volatiles, key similarities and differences among the terrestrial planets' atmospheric compositions, and planets' atmospheric escape and water loss. Also discussed are planetary atmosphere-planetary interior evolutionary coupling, the atmospheric composition of the outer planets, the structure and composition of giant planet interiors, the tenuous atmosphere of Io, the sources of the atmospheres of the outer solar system's satellites, the present state and chemical evolution of the Titan, Triton, and Pluto atmospheres, and the thermal structure and heat balance of the outer planets.

Atreya, S. K.↗
NASA NTRS2019

Initial Results from the New Horizons Exploration of 2014 MU69, a Small Kuiper Belt Object

The Kuiper Belt is a broad, torus-shaped region in the outer Solar System beyond Neptune’s orbit. It contains primordial planetary building blocks and dwarf planets. NASA’s New Horizons spacecraft conducted a flyby of Pluto and its system of moons on 14 July 2015. New Horizons then continued farther into the Kuiper Belt, adjusting its trajectory to fly close to the small Kuiper Belt object (486958) 2014 MU69 (henceforth MU69; also informally known as Ultima Thule). Stellar occultation observations in 2017 showed that MU69 was ~25 to 35 km in diameter, and therefore smaller than the diameter of Pluto (2375 km) by a factor of ~100 and less massive than Pluto by a factor of ~106. MU69 is located about 1.6 billion kilometers farther from the Sun than Pluto was at the time of the New Horizons flyby. MU69’s orbit indicates that it is a “cold classical” Kuiper Belt object, thought to be the least dynamically evolved population in the Solar System. A major goal of flying past this target is to investigate accretion processes in the outer Solar System and how those processes led to the formation of the planets. Because no small Kuiper Belt object had previously been explored by spacecraft, we also sought to provide a close-up look at such a body’s geology and composition, and to search for satellites, rings, and evidence of present or past atmosphere. We report initial scientific results and interpretations from that flyby.

S. A. Stern↗
NASA NTRS1979

Surface composition of Pluto

Broadband (J, H, K and L) and narrowband (1.5- to 3.7-micron) infrared photometry of Pluto has been conducted in order to check previous ambiguous observations of methane frost on the planet's surface. In detail, the match between a laboratory spectrum of methane frost and the observed spectrum of Pluto is not good. Nevertheless, the photometric observations suggest the presence of methane in some form.

Lebofsky, L. A.↗
NASA NTRS2016

Pluto is the new Mars!

Data from NASA's New Horizons encounter with Pluto in July 2015 revealed an astoundingly complex world. The surface seen on the encounter hemisphere ranged in age from ancient to recent. A vast craterless plain of slowly convecting solid nitrogen resides in a deep primordial impact basin, reminiscent of young enigmatic deposits in Mars' Hellas basin. Like Mars, regions of Pluto are dominated by valleys, though the Pluto valleys are thought to be carved by nitrogen glaciers. Pluto has fretted terrain and halo craters. Pluto is cut by tectonics of several different ages. Like Mars, vast tracts on Pluto are mantled by dust and volatiles. Just as on Mars, Pluto has landscapes that systematically vary with latitude due to past and present seasonal (and mega-seasonal) effects on two major volatiles. On Mars, those volatiles are H2O and CO2; on Pluto they are CH4 and N2. Like Mars, some landscapes on Pluto defy easy explanation. In the Plutonian arctic there is a region of large (approx. 40 km across) deep (approx. 3-4 km) pits that probably could not be formed by sublimation, or any other single process, alone. Equally bizarre is the Bladed terrain, which is composed of fields of often roughly aligned blade-like ridges covering the flanks and crests of broad regional swells. Topping the unexpected are two large mounds approximately150 km across, approx. 5-6 km high, with great central depressions at their summits. The central depressions are almost as deep as the mounds are tall. These mounds have many of the characteristics of volcanic mountains seen on Mars and elsewhere in the inner solar system. Hypotheses for the formation of these Plutonian mounds so far all have challenges, principally revolving around the need for H2O ice to support their relief and the difficulty imagining mechanisms that would mobilize H2O. From the perspective of one year after the encounter, our appreciation of the extent of Pluto's diversity and complexity is quite reminiscent of the perspective the science community had of Mars, with similar quality data sets, soon after the early reconnaissance of that planet in the late 1960s and early 70s. So certainly in this sense, Pluto is the new Mars.

Pluto↗