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NASA NTRS1986

Spacecraft technology requirements for future NASA missions

Missions selected by NASA as representative of the most critical technology issues are described and the key technology requirements are discussed. The following are considered: (1) the Large Deployable Reflector (LDR), (2) the Sample Return Missions (SRM), (3) the Earth Observing System (EOS), and (4) the Geostationary Communications Platform (GCP). The LDR, designed for infrared and submillimeter astronomical measurements, will contain the following components for its instruments: indium antimonide charge-coupled arrays, extrinsic photodetector arrays, and heterodyne photoconductors. New technology developed for SRM includes an X-band transponder, a fiber-optic rotation sensor, and long-life batteries. The EOS will consist of instruments designed to measure the earth's atmosphere, interior, and surface, as well as an information system to support scientific research. Inherent in the platform of the GCP is the ability to effectively utilize both the geostationary arc and the electromagnetic spectrum; the GCP can also reduce overall satellite communications system costs.

Hudson, W. R.↗

NASA NTRS1987

Formation of the layered deposits in the Valles Marineris, Mars

Thick sequences of layered deposits are found in the Valles Marineris, which exhibit fine, nearly horizontal layering, and are present as isolated plateaus of what were once more extensive deposits. It was argued that the morphology of the deposits is most consistent with origin in standing bodies of water. The conditions necessary for the existence of ice-covered Martian paleolakes are examined in detail and mechanisms for sediment deposition in them are considered. It was concluded that there are several geologically feasible mechanisms that could have led to the formation of thick deposits in ice-covered paleolakes in the Valles Marineris. Present data are insufficient to choose conclusively among the various possibilities. Several types of data from the Mars Observer mission will be useful in further characterizing the deposits and clarifying the process of their origin. The deposits should be considered important targets for a future Mars sample return mission.

Nedell, Susan S.↗

NASA NTRS1987

Spacecraft mass trade-offs versus radio-frequency power and antenna size at 8 GHz and 32 GHz

The purpose of this analysis is to help determine the relative merits of 32 GHz over 8 GHz for future deep space communications. This analysis is only a piece of the overall analysis and only considers the downlink communication mass, power, and size comparisons for 8 and 32 GHz. Both parabolic antennas and flat-plate arrays are considered. The Mars Sample Return mission is considered in some detail as an example of the tradeoffs involved; for this mission the mass, power, and size show a definite advantage of roughly 2:1 in using the 32 GHz over 8 GHz.

Gilchriest, C. E.↗

NASA NTRS1986

Sampling the cometary nucleus

Three modes for obtaining samples of cometary material: remote sampling, hover mode sampling, and landed (anchored) sampling are discussed. For each mode, trade-offs involving complexity, risk factors, and cost must be analyzed for the spacecraft and the sampling system. Flyby results for comet Halley indicate heterogeneity in the cometary nucleus that could dictate sampling at several different locations. Coring drills, drive tubes, and specialized mantle sampling devices must operate at cold temperatures (100 to 180 K) without heating the sample. Sample selections must be accomodated by the sample return canister, which must also be protected from thermal excursions.

Clark, B. C.↗

NASA NTRS1986

Analysis of cirrus from airborne lidar and radiometer observations

Lidar and passive radiance sensing data on cirrus clouds gathered in instrumented high altitude aircraft flights are analyzed, with emphasis on cirrus emittance characteristics. The data were collected with a U-2 aircraft flying at about 19 km altitude. Lidar data defined the vertical structure of the cloud which, when combined with independent atmospheric temperature data, permitted radiance to be derived from thermal radiance data. Sample return lidar images are provided of cirrus and cirrostratus clouds, along with the calculated emittance data.

Spinhirne, J. D.↗

NASA NTRS1986

Supporting planetary missions - The Space Station role

Spacecraft destined for interplanetary flight can be assembled, fueled, and tested near the Space Station, thus providing for spacecraft too large and/or massive for launch from earth on a single boost. The 28.5-deg-inclination orbit of the Station will, however, cause penalties for some missions. Another Station role is to recover sample returns from, e.g., Mars or a comet.

Blanchard, D. P.↗

NASA NTRS1986

Recent concepts in missions to Mars - Extraterrestrial processes

This paper presents some recent concepts in Mars Sample Return (MSR) missions that utilize extraterrestrial resources. The concepts examined include the power and energy needs of this mission. It is shown that solar energy is not especially attractive. Radioisotopic power generator and a Rankine cycle use are seen to be viable options. Quantitative estimates, taking into consideration state-of-the-art and projected technologies indicate that the power/energy per se is not critical to the mission - but reliability is. Hence, various modern options for the components of the power generation and utilization are discussed. The dramatic savings in Shuttle (or other) vehicle launches are quantitatively plotted. The basic system that is discussed here is the production of hydrocarbon (methane) fuel and oxygen from Martian atmosphere. For the simplest mission, it is seen that earth-carried methane burned with oxygen produced on site provides the best system.

Ramohalli, K. N.↗

NASA NTRS1987

Numerical simulation of cometary nuclei. III - Internal temperatures of cometary nuclei

The thermal diffusion equation for the internal temperature of cometary nuclei is exactly solved by means of a one-dimensional numerical model in order to shed light on the complex behavior of these temperatures with varying orbital and thermal parameters and in order to consider possible cometary nucleus thermal evolution targets for comet rendezvous and/or sample-return missions. The concept of 'new' and 'old' comets, classified in terms of how many passages around the sun have been made, may take on new meaning in view of the present demonstration that differences in eccentricity between two comets having the same period and number of apparitions may yield significantly different internal temperature profiles.

Herman, Gary↗

NASA NTRS1987

A survey of tether applications to planetary exploration

Concepts for the use of tethers in various hypothetical astronomical research missions are discussed. Tethers used to study the atmospheres of Venus and Mars and the magnetosphere of Jupiter are examined, and possible orbiting tether systems at the moon and Mars are shown and described. A tether method for collecting a sample from Comet Halley is addressed along with a system for hovering near a comet. A multiple sample return system for asteroids is described, and a heliocentric Alfven engine concept to study the solar wind is discussed.

Penzo, Paul A.↗

NASA NTRS1987

Application of solar electric propulsion to future planetary missions

Application of solar electric propulsion (SEP) to several near term planetary missions has been investigated and is described in this paper. The missions under consideration include a comet rendezvous-asteroid flyby mission (CRAF), an orbiter mission to Saturn (CASSINI) and a comet nucleus sample return mission (CNSR). Advances in both thruster and solar array technology indicate that these missions could benefit by use of a moderate size solar electric propulsion system. The trajectory scenarios considered in this paper include a solar electric earth gravity assist (SEEGA) mode for all three missions and a SEP rendezvous mode for both the CRAF and CNSR missions. In addition an all SEP propulsion mode and a hybrid SEP-chemical propulsion mode is described for the CNSR mission.

Sauer, Carl G., Jr.↗

NASA NTRS1987

Accessibility of near-earth asteroids

Missions to near-earth asteroids are of interest to both scientists and prospectors in search of extraterrestrial materials. The primary consideration in selecting the object to explore is accessibility, or the global minimum total Delta-V for a two-impulse transfer or less than 360 deg from standard Shuttle orbit to rendezvous with the asteroid. A ranking by accessibility of all known near-earth asteroids is presented. In addition, actual mission opportunities with launch dates between 1990 and 2010 for the most accessible are listed and compared with the optimal rendezvous. Actual sample return opportunities are investigated for the best candidates.

Lau, C. O.↗

NASA NTRS1987

Some aspects of space propulsion with extraterrestrial resources

Extraterrestrial resources for space processing of chemicals, in general, and propellants, in particular, are explored quantitatively. It is seen that, for several candidate space mission scenarios, space processing of both space resources and earth-carried resources can make decisive differences in the mission success for a given payload. To fix ideas and demonstrate trends, the specific case of water splitting to extract oxygen, discard (or use without storage) the resulting hydrogen, and burn earth-carried noncryogenic liquid fuel(s) in a simple rocket motor, designed for periodic thrusting, is treated in some detail. Experimental hardware is assembled and demonstrated to perform adequately, besides showing compactness of the space-packaged 'capsule' module that is self-contained. Building upon previous studies, the concept of in situ propellant production (ISPP) is reexamined in light of more recent energy and materials technologies. Missions to comets and Mars Sample Return are mentioned as candidate scenarios. The mission duration, reliability-repairability of hardware, resource availability in low earth orbit (LEO), and the thrust requirements are considered in turn. It is seen that space storage of hydrogen for extended durations (5-10 years) involves problems that require detailed studies, besides involving many presently unanswered issues. A study of the energy option in LEO and in deep space is developed in simple terms. The different solar, radioisotope, and nuclear power sources are mentioned. Storage and handling of raw and processed chemicals are considered.

Ramohalli, Kumar↗

NASA NTRS1988

A Design Study of Onboard Navigation and Guidance During Aerocapture at Mars

The navigation and guidance of a high lift-to-drag ratio sample return vehicle during aerocapture at Mars are investigated. Emphasis is placed on integrated systems design, with guidance algorithm synthesis and analysis based on vehicle state and atmospheric density uncertainty estimates provided by the navigation system. The latter utilizes a Kalman filter for state vector estimation, with useful update information obtained through radar altimeter measurements and density altitude measurements based on IMU-measured drag acceleration. A three-phase guidance algorithm, featuring constant bank numeric predictor/corrector atmospheric capture and exit phases and an extended constant altitude cruise phase, is developed to provide controlled capture and depletion of orbital energy, orbital plane control, and exit apoapsis control. Integrated navigation and guidance systems performance are analyzed using a four degree-of-freedom computer simulation. The simulation environment includes an atmospheric density model with spatially correlated perturbations to provide realistic variations over the vehicle trajectory. Navigation filter initial conditions for the analysis are based on planetary approach optical navigation results. Results from a selection of test cases are presented to give insight into systems performance.

Fuhry, Douglas Paul↗

NASA NTRS1988

Planetary Geology: Goals, Future Directions, and Recommendations

Planetary exploration has provided a torrent of discoveries and a recognition that planets are not inert objects. This expanded view has led to the notion of comparative planetology, in which the differences and similarities among planetary objects are assessed. Solar system exploration is undergoing a change from an era of reconnaissance to one of intensive exploration and focused study. Analyses of planetary surfaces are playing a key role in this transition, especially as attention is focused on such exploration goals as returned samples from Mars. To assess how the science of planetary geology can best contribute to the goals of solar system exploration, a workshop was held at Arizona State University in January 1987. The participants discussed previous accomplishments of the planetary geology program, assessed the current studies in planetary geology, and considered the requirements to meet near-term and long-term exploration goals.

Source record↗

NASA NTRS1988

Energy storage considerations for a robotic Mars surface sampler

A Mars Rover capable of obtaining surface samples will need a power system for motive power and to power scientific instrumentation. Several different power systems are considered along with a discussion of the location options. The weight and volume advantages of the different systems are described for a particular power profile. The conclusions are that a Mars Rover Sample Return Mission and Extended Mission can be accomplished utilizing photovoltaics and electrochemical storage.

Odonnell, Patricia M.↗

NASA NTRS1988

Volatiles on Mars

The long-term evolution of both the atmosphere and the surface of Mars can be understood by examining the history of volatiles in the Mars atmosphere, their non-atmospheric reservoirs, and the processes of exchange between the two. Clearly, the present state of both the surface and the atmosphere can only be seen, so that any inferences about the evolution of the climate system are just that, inferences. The processes which control the atmosphere and surface on a seasonal basis, however, are the same processes which can act on longer timescales; only the specific solar and atmospheric forcing will differ. Once the ability of each process to affect the seasonal behavior is understood, the long-timescale forcing may be applied to the various processes in order to clearly identify the ability of the processes to act over the entire history of Mars. The areas of surface-atmospheric interaction of Mars are addressed in the ongoing research. The climate system on Mars is controlled by processes involving the exchange between the surface and atmosphere, so it is important to understand the current behavior of those processes. This is especially so in light of the current interest in understanding Mars; the upcoming Mars Observer mission, and the potential for a future sample-return or human-exploration mission will focus emphasis on this area of Mars science.

Jakosky, Bruce M.↗

NASA NTRS1987

Spacecraft technology trends - A view from the past

Future spacecraft will be sent on missions to complete the exploration of the solar system, to return samples from celestial bodies, record the process of creation of stars, galaxies, and the universe itself, to provide a continuous record of earth processes, and to maintain vital space communications. A key ingredient to projecting the future is to comprehend the historic record and to understand the significance of trends. This paper focuses on spacecraft cost and life trends, as well as those of the major subsystems. Throughout the history of the 'space age' there has been significant progress in the performance of spacecraft and their subsystems. However, various aspects of spacecraft performance lag behind what is technically feasible by a considerable margin. In addition, examination of the historical trend implies that future spacecraft will likely continue to be relatively unique in their design features. This is in contrast to the technically realizable future attributes such as large space platforms, modularity, system autonomy and on-orbit repair and servicing.

Hudson, Wayne R.↗

NASA NTRS1988

The Mariner Mark II program

The Mariner Mark II spacecraft is a modular design that can be inexpensively reconfigured for different missions beyond the inner solar system. The first three missions will be described. The Comet Rendezvous Asteroid Flyby mission has a February 1993 launch to comet Tempel 2. The Cassini mission has a May 1995 launch to Saturn and Titan. The third mission is a Comet Nucleus Sample Return launch in 1998.

Draper, Ronald F.↗