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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 NTRS1993

Chemistry and evolution of gaseous circumstellar disks

An investigation of the chemical and physical processes which determine the composition and evolution of gas-rich circumstellar disks is reported. Strong mixing in a thermoclinic environment like an accretion disk leads to thermochemical disequilibration due to 'kinetic inhibition' induced by chemical time constants becoming longer than outward mixing time constants. In this case, species thermodynamically stable at high temperatures but not at low temperatures dominate at all temperatures in the disk. Nonaxisymmetric accretion of material at hypersonic speeds is a major forcing mechanism for mixing in the disk and can produce eddy speeds of 1 percent of the sound speed. The implications kinetic inhibition in the carbon, nitrogen, and anhydrous/hydrous silicate families has for the compositions of the terrestrial planets, giant planets, ice-rich satellites, Pluto, comets, meteorites, and asteroids are discussed.

Prinn, Ronald G.↗
NASA NTRS1995

Robotic Planetary Science Missions Enabled with Small NTR Engine/Stage Technologies

The high specific impulse (Isp) and engine thrust-to-weight ratio of liquid hydrogen (LH2)-cooled nuclear thermal rocket (NTR) engines makes them ideal for upper stage applications to difficult robotic planetary science missions. A small 15 thousand pound force (klbf) NTR engine using a uranium-zirconium-niobium 'ternary carbide' fuel (Isp approximately 960 seconds at approximately 3025K) developed in the Commonwealth of Independent States (CIS) is examined and its use on an expendable injection stage is shown to provide major increases in payload delivered to the outer planets (Saturn, Uranus, Neptune and Pluto). Using a single 'Titan IV-class' launch vehicle, with a lift capability to low Earth orbit (LEO) of approximately 20 metric tons (t), an expendable NTR upper stage can inject two Pluto 'Fast Flyby' spacecraft (PFF/SC) plus support equipment-combined mass of approximately 508 kg--on high energy, '6.5-9.2 year' direct trajectory missions to Pluto. A conventional chemical propulsion mission would use a liquid oxygen (LOX)/LH2 'Centaur' upper stage and two solid rocket 'kick motors' to inject a single PFF/SC on the same Titan IV launch vehicle. For follow on Pluto missions, the NTR injection stage would utilize a Jupiter 'gravity assist' (JGA) maneuver to launch a LOX/liquid methane (CH4) capture stage (Isp approximately 375 seconds) and a Pluto 'orbiter' spacecraft weighing between approximately 167-312 kg. With chemical propulsion, a Pluto orbiter mission is not a viable option because c inadequate delivered mass. Using a 'standardized' NTR injection stage and the same single Titan IV launch scenario, 'direct flight' (no gravity assist) orbiter missions to Saturn, Uranus and Neptune are also enabled with transit times of 2.3, 6.6, and 12.6 years, respectively. Injected mass includes a storable, nitrogen tetroxide/monomethyl hydrazine (N2O4/MMH) capture stage (Isp approximately 330 seconds) and orbiter payloads 340 to 820% larger than that achievable using a LOX/LH2-fueled injection stage. The paper discusses NTR technology and mission characteristics, shows NTR stage and payload accommodations within the 26.2 m long Titan IV payload fairing, and discusses NTR stage performance as a function of assumed cryogenic tank technology.

Borowski, Stanley K.↗
NASA NTRS1988

Research in planetary astronomy and operation of the Mauna Kea Observatory

Spectroscopic studies with ground-based telescopes at low resolution can give compositional information of the surfaces and atmospheres of planets, satellites, asteroids, and comets. Solid state absorptions in ices and minerals are measurable by the low-resolution spectrophotometric technique. This program includes spectroscopy of distant comets, asteroids of particular interest in various contexts (planet crossers, outer main belt, trojans, etc.), Pluto and Charon, and planetary satellites of particular interest (Iapetus, Io, Uranian satellites, etc.). In the case of planets, satellites, and comets, emphasis is placed on volatiles (ices and organics), while for asteroids the stress is on mineralogy and the connection with the meteorites. New spectra show that the IR signature of Triton has changed since 1980, in that the methane bands are significantly weaker. Spectral evidence for the presence of molecular nitrogen remains convincing. Also, the brightness of Triton throughout its orbital cycle was measured to higher precision than before and was found to be constant to better than 0.02 mag. Suggestive spectral evidence was found for the presence of the C-H stretching mode band in diffuse reflection on asteroid 130 Elektra.

Cruikshank, Dale P.↗
NASA NTRS1994

Space Science for the 21st Century. Strategic Plan for 1995-2000

This publication is one of three volumes in 'Space Science for the 21st Century', the Office of Space Science Strategic plan for 1995-2000. The other two volumes are the recently released Integrated Technology Strategy and the Education Plan, which is in preparation at this publication date. The Science Plan was developed by the Office of Space Science (OSS) in partnership with the Space Science Advisory Committee. The mission of the OSS is to seek answers to fundamental questions about: the galaxy and the universe; the connection between the Sun, Earth, and Heliosphere; the origin and evolution of planetary systems; and the origin and distribution of life in the universe. The strategy to answer these questions includes completing the means to survey the universe across the entire electromagnetic spectrum; completing the survey of cosmic rays through their highest energies, and of interstellar gas; carrying out a basic new test of the Theory of General Relativity; completing development of the means to understand the mechanisms of solar variability and its effects on Earth; completing the first exploration of the inner and outer frontiers of the heliosphere; determining the plasma environments of the solar system planets and how those environments are affected by solar activity; completing development of the means to finish the reconnaissance of the entire solar system from the Sun to Pluto; beginning the comprehensive search for other planets around other stars; resuming surface exploration of solar system bodies to understand the origin and evolution of the Sun's planetary system; continuing the study of biogenic compounds and their evolution in the universe; and searching for indicators of past and present conditions conducive to life.

Source record↗
NASA NTRS1994

Communications in Space

This paper provides an overview of the imaging results of the JPL/NASA unmanned exploration missions to all the planets of the solar system (except Pluto) as well as the telecommunications capability which was developed to enable/support those missions. the telecommunications link improvements will be described to show increases in data rate capability resulting from the addition of ground antenna aperture, transmitter power, coding techniques, lower noise receivers, etc. This paper will also describe (briefly) the current and future flight missions. The presentation will be supported by a significant number of pictures taken during the planetary encounters as well as pictures of the Deep Space Network antennas.

imaging planets Deep Space Network telecommunicati↗
NASA NTRS1992

Robotic planetary mission benefits from nuclear electric propulsion

Several interesting planetary missions are either enabled or significantly enhanced by nuclear electric propulsion (NEP) in the 50 to 100 kW power range. These missions include a Pluto Orbiter/Probe with an 11-year flight time and several years of operational life in orbit versus a ballistic very fast (13 km/s) flyby which would take longer to get to Pluto and would have a very short time to observe the planet. (A ballistic orbiter would take about 40 years to get to Pluto). Other missions include a Neptune Orbiter/Probe, a Jupiter Grand Tour orbiting each of the major moons in order, an Uranus Orbiter/Probe, a Multiple Mainbelt Asteroid Rendezvous orbiting six selected asteroids, and a Comet Nucleus Sample Return. This paper discusses potential missions and compares the nuclear electric propulsion option to the conventional ballistic approach on a parametric basis.

Kelley, James H.↗
NASA NTRS1983

On the global distribution of Pluto's atmosphere

The present investigation is relevant to the study of Pluto's current global and diurnal radiation balance. Strong gravitational tides are suggested by Charon's close proximity to Pluto (approximately 20,000 km) and Charon's large relative mass (roughly 0.25 Pluto's mass). Thus, the Pluto-Charon system replaces the earth-moon system as the best known example of a double planet. Methane is the only gas positively detected in Pluto's atmosphere. The tendency of the whole atmosphere to bulge preferentially toward the subsolar point as a result of the solar heating of the suface is considered, taking into account the longitudinal and the latitudinal tide. It is concluded that near perihelion, Pluto's atmosphere is essentially uniform over Pluto's surface. Its heat capacity by virtue of the heat of condensation is large enough that eclipses and the diurnal variation of insolation cause negligible freezing out of atmospheric gases.

Trafton, L.↗
NASA NTRS1972

A survey of dynamical data for the major planets and satellites

Representative values for the masses and sizes of the major planets and their larger satellites are given. These quantities are well determined for most of the planets, with the notable exception of Pluto, and the coefficient in the gravitational field is in most cases known well enough to see that the equilibrium value of the oblateness agrees with the observed value to first approximation. The sizes of the larger satellites only may be measured directly, and, in the case of the smaller bodies, only probable limits for the sizes can be given, inferred from the observed magnitudes. The determination of the mass of a satellite usually depends on the existence of a near-commensurability with another, the perturbation of which is augmented so as to be more easily detected in the observations.

Message, P. J.↗
NASA NTRS1981

The atmospheres of the outer planets and satellites

Recent research results concerning the atmospheres of the outer planets and satellites are presented, covering Pluto, Triton, Neptune, Uranus, Titan, Saturn, and Io. In addition to presenting analyses of physical properties and atmospheric chemical composition, attention is given to (1) the origin of Pluto; (2) the possible variability of Triton; (3) the rotation periods of Uranus and Neptune, as well as their effective temperatures and internal heating, haze distribution, thermal structure, and weather and seasonal changes; (4) the seasonal and long-term changes of Titan, in addition to its thermal structure; (5) the dust and haze distribution of Saturn; and (6) Io's gaseous plasma and neutral torio. The data include Voyager 1 and 2 results for Io, along with Pioneer 11 results for Saturn and Titan.

Trafton, L.↗
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 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 NTRS1994

(abstract) Communications in Space

This paper provides an overview of the results of the JPL/NASA unmanned exploration of all of the planets of the solar system (except Pluto) as well as the telecommunications capability which was developed to enable/support those missions. The telecommunications link improvements will be described to show increases in data rate capability resulting from addition of ground antenna aperture, transmitter power, coding techniques, lower noise receivers, etc. The paper will also describe (briefly), the current and future flight missions.

coding↗
NASA NTRS1997

Planning for the Last Planet

Spacecraft from Caltech's and NASA's Jet Propulsion Laboratory (JPL) in La Canada Flintridge have visited all the planets in the solar system except Pluto.

robotic spacecraft↗
NASA NTRS2016

Predictable Patterns in Planetary Transit Timing Variations and Transit Duration Variations Due to Exomoons

We present new ways to identify single and multiple moons around extrasolar planets using planetary transit timing variations (TTVs) and transit duration variations (TDVs). For planets with one moon, measurements from successive transits exhibit a hitherto undescribed pattern in the TTV-TDV diagram, originating from the stroboscopic sampling of the planet's orbit around the planet-moon barycenter. This pattern is fully determined and analytically predictable after three consecutive transits. The more measurements become available, the more the TTV-TDV diagram approaches an ellipse. For planets with multiple moons in orbital mean motion resonance (MMR), like the Galilean moon system, the pattern is much more complex and addressed numerically in this report. Exomoons in MMR can also form closed, predictable TTV-TDV figures, as long as the drift of the moons' pericenters is suciently slow.We find that MMR exomoons produce loops in the TTV-TDV diagram and that the number of these loops is equal to the order of the MMR, or the largest integer in the MMR ratio.We use a Bayesian model and Monte Carlo simulations to test the discoverability of exomoons using TTV-TDV diagrams with current and near-future technology. In a blind test, two of us (BP, DA) successfully retrieved a large moon from simulated TTV-TDV by co-authors MH and RH, which resembled data from a known Kepler planet candidate. Single exomoons with a 10 percent moon-to-planet mass ratio, like to Pluto-Charon binary, can be detectable in the archival data of the Kepler primary mission. Multi-exomoon systems, however, require either larger telescopes or brighter target stars. Complementary detection methods invoking a moon's own photometric transit or its orbital sampling effect can be used for validation or falsification. A combination of TESS, CHEOPS, and PLATO data would offer a compelling opportunity for an exomoon discovery around a bright star.

stroboscopic sampling↗
NASA NTRS1994

Optimal Low Thrust Trajectories Using Differential Inclusion Concepts

A direct optimization method based on differential inclusion concepts has been developed and used to compute low thrust trajectories. This new formulation removes explicit control dependence from the problem statement thereby reducing the dimension of the parameter space of the resulting nonlinear programming problem. A simple example of a two-dimensional gravity-free trajectory involving a maximum velocity transfer to a rectilinear path is discussed. Three interplanetary trajectory examples, an Earth-Mars constant specific impulse transfer, and Earth-Jupiter constant specific impulse transfer, and an Earth-Venus-Mars variable specific impulse gravity assist, are also included. An analysis of the technique's performance is provided.

low↗
NASA NTRS2021

Neptune Odyssey: A Flagship Concept for the Exploration of the Neptune–Triton System

The Neptune Odyssey mission concept is a Flagship-class orbiter and atmospheric probe to the Neptune–Triton system. This bold mission of exploration would orbit an ice-giant planet to study the planet, its rings, small satellites, space environment, and the planet-sized moon Triton. Triton is a captured dwarf planet from the Kuiper Belt, twin of Pluto, and likely ocean world. Odyssey addresses Neptune system-level science, with equal priorities placed on Neptune, its rings, moons, space environment, and Triton. Between Uranus and Neptune, the latter is unique in providing simultaneous access to both an ice giant and a Kuiper Belt dwarf planet. The spacecraft—in a class equivalent to the NASA/ESA/ASI Cassini spacecraft—would launch by 2031 on a Space Launch System or equivalent launch vehicle and utilize a Jupiter gravity assist for a 12 yr cruise to Neptune and a 4 yr prime orbital mission; alternatively a launch after 2031 would have a 16 yr direct-to-Neptune cruise phase. Our solution provides annual launch opportunities and allows for an easy upgrade to the shorter (12 yr) cruise. Odyssey would orbit Neptune retrograde (prograde with respect to Triton), using the moonʼs gravity to shape the orbital tour and allow coverage of Triton, Neptune, and the space environment. The atmospheric entry probe would descend in ∼37 minutes to the 10 bar pressure level in Neptune’s atmosphere just before Odysseyʼs orbit-insertion engine burn. Odysseyʼs mission would end by conducting a Cassini-like “Grand Finale,” passing inside the rings and ultimately taking a final great plunge into Neptuneʼs atmosphere.

Abigail M. Rymer↗
NASA NTRS1996

Pluto Express: Mission to Pluto

Pluto is the smallest, outermost and last-discovered planet in the Solar System and the only one that has never been visited by a spacecraft from Earth. Pluto and its relatively large satellite Charon are the destinations of a proposed spacecraft mission for the next decade, being developed for NASA by scientists and engineers at NASA's Jet Propulsion Laboratory.

Pluto mission to Pluto Charon Pluto's atmosphere s↗