A method of soft tether stationkeeping
Orbital motion of lunar module/Apollo telescope mount tethered to S-IVB orbital workshop
SATURN S-IVB STAGE↗
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Results for “ORBITAL WORKER”
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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Development of prototype mass measurement system for spaceflight
Construction and evaluation of prototype equipment to monitor mass changes of astronauts during orbital flight
MASS RATIO↗
Cluster man/system design requirements and verification
Discussion of the procedures employed for determining the man/system requirements that guided Skylab design, and review of the techniques used for implementing the man/system design verification. The foremost lesson learned from the design need anticipation and design verification experience is the necessity to allow for human capabilities of in-flight maintenance and repair. It is now known that the entire program was salvaged by a series of unplanned maintenance and repair events which were implemented in spite of poor design provisions for maintenance.
Orbital workers↗
Geometric Properties of Possible Volcanoes in the South Polar Region, Mars
In 1987 Tanaka and Scott mapped the south polar region of Mars using Viking Orbiter data and identified several features as volcanoes, probable volcanoes of uncertain origin, or mountains of uncertain origin. Several workers have since studied these features using Mars Orbiter Laser Altimetry (MOLA) data. In the north polar region of Mars volcanic edifices have been identified that have surrounding annular depressions, perhaps formed when magma chamber heat melted surrounding ground ice causing surface subsidence. Our objective is to use Martian south polar volcanoes as indicators of magma-ground ice interactions and as indicators of regional eruptive styles. In this study we use high resolution MOLA data to characterize the geometric parameters of mapped volcanoes and mountains and systematically search for any unidentified volcanic edifices from latitude 55 S to the South Pole.
Polit, A. T.↗
Proposal for a remotely manned space station
The United States is in trouble in space. The costs of the proposed Space Station Freedom have grown beyond reach, and the present design is obsolete. The trouble has come from imagining that there are only two alternatives: manned vs. unmanned. Both choices have led us into designs that do not appear to be practical. On one side, the United States simply does not possess the robotic technology needed to operate or assemble a sophisticated unmanned space station. On the other side, the manned designs that are now under way seem far too costly and dangerous, with all of its thousands of extravehicular activity (EVA) hours. More would be accomplished at far less cost by proceeding in a different way. The design of a space station made of modular, Erector Set-like parts is proposed which is to be assembled using earth-based remotely-controlled binary-tree telerobots. Earth-based workers could be trained to build the station in space using simulators. A small preassembled spacecraft would be launched with a few telerobots, and then, telerobots could be ferried into orbit along with stocks of additional parts. Trained terrestrial workers would remotely assemble a larger station, and materials for additional power and life support systems could be launched. Finally, human scientists and explorers could be sent to the space station. Other aspects of such a space station program are discussed.
Minsky, Marvin↗
Site Selection for Mars Exopaleontology in 2001
The microbial fossil record encompasses a wide range of information, including cellular remains, stromatolites, biofabrics, trace fossils, biominerals and chemofossils. The preservation of fossils is strongly influenced by the physical, chemical and biological factors of the environment which, acting together, ultimately determine the types of information that will be captured and retained in the rock record. The critical factor in assessing the suitability of a site for a microbial fossil record is the paleoenvironment. The reconstruction of ancient sedimentary environments usually requires the integration of a wide variety of geological information, including the shape, geometry and internal structure of sedimentary deposits, their mineralogy, and geochemistry. For Mars, much of our knowledge about past environments is based on orbital imaging of geomorphic features. This evidence provides an important context and starting point for site selection. However, our knowledge of the martian surface is quite limited, and a major goal of the upcoming exploration effort is to reconstruct the history of Martian volatiles, climate, and hydrology as a context for the exploration for past or present life. Mineralogical mapping from orbit will be an important key in this effort. In exploring for evidence of past life, terrestrial experience suggests that the long-term preservation of biological information as fossils occurs under a fairly narrow range of geological conditions that are well known to paleontologists (1). In detrital sedimentary systems, microbial fossilization is favored by rapid burial in fine-grained, clay-rich sediments. In chemical sedimentary systems, preservation is enhanced by rapid entombment in fine-grained chemical precipitates. For long term preservation, host rocks must be composed of stable minerals that resist chemical weathering, and which form an impermeable matrix and closed chemical system that can protect biosignatures from alteration during subsequent diagenetic change or metamorphism. In this context, host rocks composed of highly ordered, chemically-stable mineral phases, like silica (forming cherts) or phosphate (forming phosphorites), are especially favored. Such lithologies tend to have very long crustal residence times and (along with carbonates and shales), are the most common host rocks for the Precambrian microfossil record on Earth. If we assume that a subsurface hydrosphere has been present throughout martian history, then life could have originated there at any time, perhaps emerging at the surface periodically when climate changes, induced by external forcing or endogenous processes (e.g. volcanism), allowed liquid water to exist at the surface. The recent discovery of subsurface chemolithoautotrophic organisms which are capable of synthesizing organic substrates from C02 and H2 liberated from the aqueous weathering of basalt, is especially. relevant as a model for martian life. While a subsurface habitable zone may yet exist on Mars, access to such environments will likely require drilling to depths of several kilometers. Given the technological challenge of deep drilling, this is unlikely to occur prior to human missions. So, even if there is extant life on Mars today in subsurface habitats, it may be much easier to find its fossil counterparts in ancient deposits exposed at the surface. In exploring for a fossil record in subsurface environments on Mars there are several geological situations that may provide access to the appropriate materials. These include 1) ejecta from impact craters, 2) talus slopes, debris flows or alluvial fans developed below the walls of deep canyons, and 3) the deposits of outflood channels. Examples of aqueous mineral deposits of formed in subsurface environments that could harbor a microbial fossil record include such things as cements in detrital sedimentary rocks, low temperature diagenetic minerals deposited in veins, or filling vesicles in volcanic rocks, and hydrothermal deposits formed below the upper temperature limit for life (about 160 degrees C). There are many sites within the present latitudinal constraints for the 2001 mission (15 deg S to 30 deg N) that meet these requirements. But the practical problem with these kinds of deposits is that they tend to be disseminated, making up only a small percentage of a host rock. Even with mineralogical information provided by the Thermal Emission Spectrometer (TES) presently in orbit around Mars, predicting their occurrence ahead of time may be quite difficult. The deposits of surficial aqueous sedimentary systems are likely to provide the largest targets for site selection in 2001. Of these, the deposits of hydrothermal systems (subaerial and subaqueous thermal springs) have been discussed previously. It is likely that hydrothermal systems were widespread on Mars early in its history and a number of common geo-tectonic settings on Mars are likely to have hosted hydrothermal activity. Most of these are represented within the latitudinal constraints presently identified for 2001. However, the deposits of surface spring systems are likely to be difficult to find as well. On Earth, exposure areas for hydrothermal spring mounds are typically a few square kms, less than a single TES pixel. But such deposits may be quite abundant within some volcanic terrains, It is estimated, for example, that between 15-20% of the floor of Yellowstone caldera is covered by thermal spring deposits. In such abundances, subaerial sinters could well be detected by TES. Where exposed, the shallow subsurface portions of these systems may be quite a lot larger (perhaps tens of square kms), although (as noted above) mineralization may be finely disseminated in the basement rock, making remote detection more difficult. Paleolake Basins. There are a large number of potential paleolake basins on Mars (inclusive of impact craters and volcanic calderas) that have been previously identified using Viking images. Most of these lie in the southern highlands beyond the l5 deg S constraint for 2001. However, deposits of paleolakes may offer the largest and most easily identified exopaleontological targets from orbit. Based on a variety of arguments, some workers have suggested that there was once an ancient ocean on the northern plains, and some sites of interest (potential shoreline terraces) fall within the 30 deg N constraint. From a paleontological standpoint the most interesting places of this type are terminal paleolake basins which are likely to have been both saline and alkaline. Models by Schaefer suggest such environments could be widespread on Mars. The conditions in terminal lake basin settings favor widespread chemical sedimentation, an important condition for microbial fossilization. Important lithological targets for a microbial fossil record in terminal lake basins include spring-deposited carbonates, shoreline cements, a wide variety of evaporite minerals and fine-grained detrital sediments including shales, marls, and water-lain volcanic ash deposits. In developing a strategy to explore for ancient hydrothermal deposits on Mars, we can learn from the methods that have been developed by explorationists to explore for economic mineral deposits on Earth. Due to their simple mineralogy, hydrothermal deposits can often be detected using remote sensing methods. Common thermal spring mineral assemblages include silica, carbonate, and various metallic oxides and sulfides. But there are also a number of diagnostic silicate minerals, including clays, formed by the hydrothermal alteration of country rocks. These hydrothermal minerals have characteristic spectral signatures that could be detected from Mars orbit using high resolution infrared remote sensing methods. In playa lake settings, evaporite deposits often form a predictable "bull's eye" pattern with carbonates being deposited in marginal basin areas, and sulfates and halides occurring progressively more basinward. The floors of some impact craters on Mars, such as "White Rock" and Bequeral Crater (see Oxia Palus NE, Site 148), have floor deposits that could be evaporites, inclusive of carbonates. Evaporite minerals possess characteristic spectral signatures in the infrared and could similarly be identified from Mars orbit using high resolution remote sensing methods. Clearly, utilization of TES data will be important for optimizing site selection for Exopaleontology, and every effort should be made to benefit from that data before a final decision is made.
Farmer, Jack↗
Some new aspects on the superrotation of the thermosphere
The motion of the thermosphere with a rotational velocity between 10 and 20 per cent in excess of the earth's rotational velocity has been deduced by King-Hele and his co-workers from the change of the inclination of satellite orbits. To date, no completely satisfactory explanation of the observations has been presented. In this paper, it is shown that in the thermosphere there exists a small diurnal mean driving force in the eastward direction. This force has not previously been considered in analyses of superrotation. A critical review of the observations and a theoretical analysis that takes account of both equinox and solstice conditions is presented. In the lower height region, where the great majority of observations were made, it is possible to achieve agreement between observations and a dynamical model. Additional observational data are needed in the isothermal region for a more complete analysis.
Blum, P. W.↗
Rate constants for the deactivation of O/1D/ by Xe, Kr, and Ar over the range 110-330 K
The rate constants for the deactivation of O(1D) by Xe, Kr, and Ar were measured over the range 110-330 K. Only Xe had a significant temperature dependence. Its Arrhenius expression is (8.5 + or - 1.7) times 10 to the -11th power exp(-103 + or - 52)/RT cu cm/molecule-sec. The rate constants for Kr and Ar are (6.4 + or - 1.3) times 10 to the -12th power and (5.0 + or - 1.5) times 10 to the -13th power cu cm/molecule-sec, respectively. The observed trend in deactivation efficiency, Xe (greatest), Kr, Ar (least), and the observed temperature effects support the results and the spin-orbit interaction mechanism for deactivation given by Husain and co-workers.
Davidson, J. A.↗
Annual survey of spaceflight safety systems: 11th supplement. Survey period - July 1980-June 1981
Reports in the field of space flight safety applicable to current and future operational space activities which appeared between July 1980 and June 1981 are surveyed. Subjects in the area of flight rescue and safety during launch, on-orbit, reentry and landing phases include the major activities and findings of the first Shuttle test flight, a slidewire system for emergency egress from the Space Shuttle on the launch pad, and the testing of the Spacelab engineering model. In the area of human capabilities and crew roles, attention is given to reports of repairs to the Salyut 6 space station made by a Soyuz crew, and an assessment of weightlessness effects on space worker health and safety. Safety requirements for STS payloads including pressure vessels, and the Orbiter window system and for spacecraft testing are also presented, along with those for a television system to aid in monitoring astronaut extravehicular activities. For the operation of large space structures, reports include EVA equipment for satellite servicing and the safety aspects of connectors used in construction. Finally, attention is given to safety-related criteria in a study of Shuttle interactions with the proposed Space Operations Center.
Brown, N. E.↗
Toxicity study of dimethylethoxysilane (DMSES), the waterproofing agent for the Orbiter heat protective system
DMES, a volatile liquid, is used by NASA to waterproof the Orbiter thermal protective system. During waterproofing operations at the Oribter Processing Facility at KSC, workers could be exposed to DMES vapor. To assess the toxicity of DMES, acute and subchronic (2-week and 13-week) inhalation studies were conducted with rats. Studies were also conducted to assess the potential of DMES. Inhalation exposure concentrations ranged from 40 ppm to 4000 ppm. No mortality was observed during the studies. Exposures to 2100 ppm produced narcosis and ataxia. Post-exposure recovery from these CNS effects was rapid (less than 1 hr). These effects were concentration-dependent and relatively independent of exposure length. Exposure to 3000 ppm for 2 weeks (5 h/d, 5 d/wk) produced testicular toxicity. The 13-week study yielded similar results. Results from the genotoxicity assays (in vivo/in vitro unscheduled DNA synthesis in rat primary heptaocytes, chromosomal aberrations in rat bone marrow cells; reverse gene mutation in Salmonella typhimurium; and forward mutation in Chinese hamster culture cells) were negative. These studies indicated that DMES is mildly to moderately toxic but not a multagen.
Lam, Chiu-Wing↗
A simulation system for Space Station extravehicular activity
America's next major step into space will be the construction of a permanently manned Space Station which is currently under development and scheduled for full operation in the mid-1990's. Most of the construction of the Space Station will be performed over several flights by suited crew members during an extravehicular activity (EVA) from the Space Shuttle. Once fully operational, EVA's will be performed from the Space Station on a routine basis to provide, among other services, maintenance and repair operations of satellites currently in Earth orbit. Both voice recognition and helmet-mounted display technologies can improve the productivity of workers in space by potentially reducing the time, risk, and cost involved in performing EVA. NASA has recognized this potential and is currently developing a voice-controlled information system for Space Station EVA. Two bench-model helmet-mounted displays and an EVA simulation program have been developed to demonstrate the functionality and practicality of the system.
Marmolejo, Jose A.↗
Broadband X-Ray Spectra of GX 339-4 and the Geometry of Accreting Black Holes in the Hard State
A major question in the study of black hole binaries involves our understanding of the accretion geometry when the sources are in the "hard" state. In this state, the X-ray energy spectrum is dominated by a hard power-law component and radio observations indicate the presence of a steady and powerful "compact" jet. Although the common hard state picture is that the accretion disk is truncated, perhaps at hundreds of gravitational radii (R(sub g)) from the black hole, recent results for the recurrent transient GX 339-4 by Miller and co-workers show evidence for optically thick material very close to the black hole's innermost stable circular orbit. That work focused on an observation of GX 339-4 at a luminosity of about 5% of the Eddington limit (L(sub Edd)) and used parameters from a relativistic reflection model and the presence of a soft, thermal component as diagnostics. In this work, we use similar diagnostics, but extend the study to lower luminosities (2.3% and 0.8% L(sub Edd)) using Swift and RXTE observations of GX 339-4. We detect a thermal component with an inner disk temperature of approx.0.2 keV at 2.3% L(sub Edd). At 0.8% L(sub Edd), the spectrum is consistent with the presence of such a component, but the component is not required with high confidence. At both luminosities, we detect broad features due to iron Ka that are likely related to reflection of hard X-rays off the optically thick material. If these features are broadened by relativistic effects, they indicate that optically thick material resides within 10 R(sub g) down to 0.8% L(sub Edd), and the measurements are consistent with the inner radius of the disk remaining at approx.4 R(sub g) down to this level. However, we also discuss an alternative model for the broadening, and we note that the evolution of the thermal component is not entirely consistent with the constant inner radius interpretation. Finally, we discuss the results in terms of recent theoretical work by Liu and co-workers on the possibility that material may condense out of an Advection-Dominated Accretion Flow to maintain an inner optically thick disk.
Tomsick↗
A Survey of Formal Methods for Intelligent Swarms
Swarms of intelligent autonomous spacecraft, involving complex behaviors and interactions, are being proposed for future space exploration missions. Such missions provide greater flexibility and offer the possibility of gathering more science data than traditional single spacecraft missions. The emergent properties of swarms make these missions powerful, but simultaneously far more difficult to design, and to assure that the proper behaviors will emerge. These missions are also considerably more complex than previous types of missions, and NASA, like other organizations, has little experience in developing or in verifying and validating these types of missions. A significant challenge when verifying and validating swarms of intelligent interacting agents is how to determine that the possible exponential interactions and emergent behaviors are producing the desired results. Assuring correct behavior and interactions of swarms will be critical to mission success. The Autonomous Nano Technology Swarm (ANTS) mission is an example of one of the swarm types of missions NASA is considering. The ANTS mission will use a swarm of picospacecraft that will fly from Earth orbit to the Asteroid Belt. Using an insect colony analogy, ANTS will be composed of specialized workers for asteroid exploration. Exploration would consist of cataloguing the mass, density, morphology, and chemical composition of the asteroids, including any anomalous concentrations of specific minerals. To perform this task, ANTS would carry miniaturized instruments, such as imagers, spectrometers, and detectors. Since ANTS and other similar missions are going to consist of autonomous spacecraft that may be out of contact with the earth for extended periods of time, and have low bandwidths due to weight constraints, it will be difficult to observe improper behavior and to correct any errors after launch. Providing V&V (verification and validation) for this type of mission is new to NASA, and represents the cutting edge in system correctness, and requires higher levels of assurance than other (traditional) missions that use a single or small number of spacecraft that are deterministic in nature and have near continuous communication access. One of the highest possible levels of assurance comes from the application of formal methods. Formal methods are mathematics-based tools and techniques for specifying and verifying (software and hardware) systems. They are particularly useful for specifying complex parallel systems, such as exemplified by the ANTS mission, where the entire system is difficult for a single person to fully understand, a problem that is multiplied with multiple developers. Once written, a formal specification can be used to prove properties of a system (e.g., the underlying system will go from one state to another or not into a specific state) and check for particular types of errors (e.g., race or livelock conditions). A formal specification can also be used as input to a model checker for further validation. This report gives the results of a survey of formal methods techniques for verification and validation of space missions that use swarm technology. Multiple formal methods were evaluated to determine their effectiveness in modeling and assuring the behavior of swarms of spacecraft using the ANTS mission as an example system. This report is the first result of the project to determine formal approaches that are promising for formally specifying swarm-based systems. From this survey, the most promising approaches were selected and are discussed relative to their possible application to the ANTS mission. Future work will include the application of an integrated approach, based on the selected approaches identified in this report, to the formal specification of the ANTS mission.
Truszkowski, Walt↗
Mapping the stability region of the 3:2 Neptune-Pluto resonance
Pluto and Charon are most likely the remnants of a large number of objects that existed in the Uranus-Neptune region at early epochs of the solar system. Numerical integrations have shown that, in general, such objects were ejected from the planetary region on timescales of approximately 10(exp 7) years after Neptune and Uranus reached their current masses. It is thought that the Pluto-Charon system survived to current times without being dynamically removed in this way because it is trapped in a set of secular and mean motion resonances with Neptune. The best-known Pluto-Neptune orbit coupling is the 3:2 mean motion resonance discovered almost 30 years ago by C. Cohen and E. Hubbard. These workers showed that the resonance angle, delta is equivalent to 3(lambda(sub P)) - 2(lambda(sub N)) - omega-bar(sub P) where omega-bar(sub P) is the longitude of perihelion of the Pluto-Charon system, and lambda(sub N) and lambda(sub P) are the mean longitude of Neptune and Pluto-Charon respectively, librates about 180 deg with an amplitude, A(sub delta), of 76 deg. A numerical simulation project to map out the stability region of the 3:2 resonance is reported. The results of these simulations are important to understanding whether Pluto's long-term heliocentric stability requires only the 3:2 resonance, or whether it instead requires one or more of the other Pluto-Neptune resonances. Our study also has another important application. By investigating stability timescales as a function of orbital elements, we gain insight into the fraction of orbital phase space which the stable 3:2 resonance occupies. This fraction is directly related to the probability that the Pluto-Charon system (and possibly other small bodies) could have been captured into this resonance.
Levison, H. F.↗
Aboard the Space Shuttle
Livability aboard the space shuttle orbiter makes it possible for men and women scientists and technicians in reasonably good health to join superbly healthy astronauts as space travelers and workers. Features of the flight deck, the mid-deck living quarters, and the subfloor life support and house-keeping equipment are illustrated as well as the provisions for food preparation, eating, sleeping, exercising, and medical care. Operation of the personal hygiene equipment and of the air revitalization system for maintaining sea level atmosphere in space is described. Capabilities of Spacelab, the purpose and use of the remote manipulator arm, and the design of a permanent space operations center assembled on-orbit by shuttle personnel are also depicted.
Steinberg, F. S.↗
Results of Click Workers Mars Crater Marking and Crater Classification
This paper presents several data tables on Mars Crater Markings and Crater Classifications. The tables include: 1) Craters observed in Mars Orbiter Camera (MOC); 2) Craters observed in Mars Digital Image Mosaics from Viking Orbiter images; and 3) Crater classifications in Mars Digital Image Mosaics from Viking Orbiter images.
Kanesky, Bob↗
The Size of the Universe and Where Will We Go?
As an avid engineer and amateur astronomer, Mike Lawson presented a perspective on the size of the universe and asked the question, "Where will we go?" This was an entry-level overview for the average space worker who really wanted to understand the size of stars and the distance between objects in space. Mike provided information about familiar orbital objects and elaborated more on galaxies during the discussion. He also explored where humans could go in space and the physical limitations of going there.
Lawson, B. Mike↗
Small Crater Morphology Within Gusev Crater and Isidis Planitia: Evidence for Widespread Secondaries on Mars
Large (greater than 2 km diameter) impact craters on the martian surface have been extensively studied and modeled. Craters smaller than this were known to exist but the lack of high-resolution images prevented detailed measurements and descriptions. Images obtained by the Mars Orbiter Camera (MOC) on Mars Global Surveyor are of sufficient resolution to perform detailed studies on the morphology of small (less than 1 km diameter) craters. Previous workers have suggested that many of these small craters are secondary craters; while others maintain that they represent primary impacts. The difference is significant, however, because of implications for surface age, climate change, impact generated regolith, provenance of surface rocks, engineering considerations (landing safety and rover trafficability), and the origin of martian meteorites.
Hurst, M.↗