Search NASA⌕ Search

SEARCH · Search NASA

Results for “space-based”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

MIT's interferometer CST testbed

The MIT Space Engineering Research Center (SERC) has developed a controlled structures technology (CST) testbed based on one design for a space-based optical interferometer. The role of the testbed is to provide a versatile platform for experimental investigation and discovery of CST approaches. In particular, it will serve as the focus for experimental verification of CSI methodologies and control strategies at SERC. The testbed program has an emphasis on experimental CST--incorporating a broad suite of actuators and sensors, active struts, system identification, passive damping, active mirror mounts, and precision component characterization. The SERC testbed represents a one-tenth scaled version of an optical interferometer concept based on an inherently rigid tetrahedral configuration with collecting apertures on one face. The testbed consists of six 3.5 meter long truss legs joined at four vertices and is suspended with attachment points at three vertices. Each aluminum leg has a 0.2 m by 0.2 m by 0.25 m triangular cross-section. The structure has a first flexible mode at 31 Hz and has over 50 global modes below 200 Hz. The stiff tetrahedral design differs from similar testbeds (such as the JPL Phase B) in that the structural topology is closed. The tetrahedral design minimizes structural deflections at the vertices (site of optical components for maximum baseline) resulting in reduced stroke requirements for isolation and pointing of optics. Typical total light path length stability goals are on the order of lambda/20, with a wavelength of light, lambda, of roughly 500 nanometers. It is expected that active structural control will be necessary to achieve this goal in the presence of disturbances.

Hyde, Tupper↗
NASA NTRS1990

Future solar system missions

NASA's planetary exploration program is discussed, with emphasis on strategy, namely, exploration of all three main classes of solar system bodies (the terrestrial planets, the outer giants and their moons, and the primitive small bodies). Planning of an extensive search for other planetary systems is focused on the application of various approaches to ultra-high precision astrometry and the possible use of a space-based coronagraphic telescope. Program strategy and lunar and Mars outpost precursor missions are illustrated.

Briggs, Geoffrey A.↗
NASA NTRS1991

Steady state modeling of large diameter crystal growth using baffles

Buoyancy driven flow in the crystal melt is one of the leading causes of segregation. Natural convection arises from the presence of thermal and/or solutal gradients in the melt and it is not possible to completely eliminate the convection even in the low gravity environment of space. This paper reports the results of computational modeling research that is being done in preparation for space-based experiments. The commercial finite element code FIDAP was used to simulate the steady convection of a gallium-doped germanium alloy in a Bridgman-Stockbarger furnace. In particular, the study examines the convection-suppressing benefits of inserting cylindrical baffles in the molten region to act as viscous dampers. These thin baffles are assumed to be inert and noncontaminating. The results from this study show the manner in which the streamlines, velocities, and temperature fields at various gravity levels are affected by the presence of baffles. The effects of changing both the number and position of the baffles are examined and the advantages and disadvantages of using baffles are considered.

Sahai, Vivek↗
NASA NTRS1991

Optical correlator techniques applied to robotic vision

Vision processing is one of the most computationally intensive tasks required of an autonomous robot. The data flow from a single typical imaging sensor is roughly 60 Mbits/sec, which can easily overload current on-board processors. Optical correlator-based processing can be used to perform many of the functions required of a general robotic vision system, such as object recognition, tracking, and orientation determination, and can perform these functions fast enough to keep pace with the incoming sensor data. We describe a hybrid digital electronic/analog optical robotic vision processing system developed at Ames Research Center to test concepts and algorithms for autonomous construction, inspection, and maintenance of space-based habitats. We discuss the system architecture design and implementation, its performance characteristics, and our future plans. In particular, we compare the performance of the system to a more conventional all digital electronic system developed concurrently. The hybrid system consistently outperforms the digital electronic one in both speed and robustness.

Hine, Butler P., III↗
NASA NTRS1985

Results of an observing system simulation experiment based on the proposed Windsat instrument

Two fraternal twin experiments were conducted as part of this study. A data impact experiment using real data (runs 1 and 2) was conducted to assess the impact that rawin wind observations have on both a 5-day assimilation and a single 5-day forecast generated at the end of each assimilation. An observing system simulation experiment (OSSE) using simulated observations (runs 3, 4, and 5) was conducted in order to first calibrate the OSSE results and second to use this calibration to estimate the 'real world' impact from the contribution of global 3-dimensional wind profiles generated from a space-based lidar system known as Windsat. Each of the three runs in the seond experiment were also 5-day assimilation runs with a 5-day forecast initialized from the last 6-hour update cycle of the assimilation. The data impact study revealed a consistent positive impact when rawin winds were added back into an otherwise complete FGGE data set. Both the 6-hour and 5-day forecasts were improved at all levels, in both hemispheres, and for both the wind and the geopotential height fields. Similar results were obtained from the two parallel simulation runs, 3 and 4. Together with the results from runs 1 and 2, calibration coefficients were generated so as to 'correct' the results determined from the addition of Windsat winds (run 5). The Windsat simulation showed a positive improvement in all cases studied. Even though only the tropics were enhanced with these wind observations, hemispheric rms errors were decreased in both the assimilation and 5-day forecast. The 6-hour forecasts of zonal wind from the assimilation run were improved by as much as 50 pct. on the average, and the single forecast showed an average improvement of near 30 pct. Even though these calibrated values are considered too optimistic, the skill of the forecast generated from this run extended the useful forecast period by 18-24 hours.

Arnold, Charles P., Jr.↗
NASA NTRS1989

Residual mode filters and adaptive control in large space structures

One of the most difficult problems in controlling large systems and structures is compensating for the destructive interaction which can occur between the reduced-order model (ROM) of the plant, which is used by the controller, and the unmodeled dynamics of the plant, often called the residual modes. The problem is more significant in the case of large space structures because their naturally light damping and high performance requirements lead to more frequent, destructive residual mode interaction (RMI). Using the design/compensation technique of residual mode filters (RMF's), effective compensation of RMI can be accomplished in a straightforward manner when using linear controllers. The use of RMF's has been shown to be effective for a variety of large structures, including a space-based laser and infinite dimensional systems. However, the dynamics of space structures is often uncertain and may even change over time due to on-orbit erosion from space debris and corrosive chemicals in the upper atmosphere. In this case, adaptive control can be extremely beneficial in meeting the performance requirements of the structure. Adaptive control for large structures is also based on ROM's and so destructive RMI may occur. Unfortunately, adaptive control is inherently nonlinear, and therefore the known results of RMF's cannot be applied. The purpose is to present the results of new research showing the effects of RMI when using adaptive control and the work which will hopefully lead to RMF compensation of this problem.

Davidson, Roger A.↗
NASA NTRS1989

Petite Amateur Navy Satellite (PANSAT)

The Naval Postgraduate School's (NPS) Space Systems Academic Group (SSAG) is designing and developing a small communications satellite for launch aboard the shuttle as a complex autonomous payload (CAP). The objectives of PANSAT are three-fold. First, PANSAT will provide an ideal educational tool for the officer students at NPS supporting Space Systems Engineering and Space Systems Operations with hands-on hardware development. Second, the satellite will provide digital store-and-forward communications, or packet radio, for the amateur radio community. The third objective is to provide a low-cost, space-based platform for small experiments. PANSAT will be launched from the shuttle at a nominal altitude of 200 n.m. and an inclination of at least 37 degrees. The satellite weight is 150 lbs. Since there is no attitude control, eight dipole whip antennas will be used to provide isotropic ground coverage for communications. FM digital communications will be used with up-link and down-link on a single frequency in the amateur band of 437.25 MHz. A maximum 50 kHz of bandwidth is envisioned for the satellite. The expected lifetime of the satellite is 1 1/2 to 2 years before atmospheric reentry. The PANSAT design consists of the following: communications subsystem (COMM); computer, or data processor and sequencer (DP&S); power subsystem; structure subsystem; and experiment payload.

Sakoda, D.↗
NASA NTRS1989

Laser powered interorbital vehicle

A preliminary design of a low-thrust Laser Powered Interorbital Vehicle (LPIV) intended for cargo transportation between an Earth space station and a lunar base is presented. The selected mission utilizes a spiral trajectory, characteristic of a low-thrust spacecraft, requiring eight days for a lunar rendezvous and an additional nine days for return. The ship's configuration consists primarily of an optical train, two hydrogen plasma engines, a 37.1 m box-beam truss, a payload module, and propellant tanks. The total mass of the vehicle, fully loaded, is 63,300 kg. A single plasma, regeneratively cooled engine design is incorporated into the two 500 N engines. These are connected to the spacecraft by turntables that allow the vehicle to thrust tangential to the flight path. Proper collection and transmission of the laser beam to the thrust chambers is provided through the optical train. This system consists of a 23-m-diameter primary mirror, a convex parabolic secondary mirror, a beam splitter, and two concave parabolic tertiary mirrors. The payload bay is capable of carrying 18,000 kg of cargo and is located opposite the primary mirror on the main truss. Fuel tanks carrying a maximum of 35,000 kg of liquid hydrogen are fastened to tracks that allow the tanks to be moved perpendicular to the main truss. This capability is required to prevent the center of mass from moving out of the thrust vector line. The laser beam is located and tracked by means of an acquisition, pointing, and tracking system that can be locked onto the space-based laser station. Correct orientation of the spacecraft with the laser beam is maintained by control moment gyros and reaction control rockets. In addition, an aerobrake configuration was designed to provide the option of using the atmospheric drag in place of propulsion for a return trajectory.

Clarke, M. T.↗
NASA NTRS1990

Optimal design of a space power system

The aerospace industry, like many other industries, regularly applies optimization techniques to develop designs which reduce cost, maximize performance, and minimize weight. The desire to minimize weight is of particular importance in space-related products since the costs of launch are directly related to payload weight, and launch vehicle capabilities often limit the allowable weight of a component or system. With these concerns in mind, this paper presents the optimization of a space-based power generation system for minimum mass. The goal of this work is to demonstrate the use of optimization techniques on a realistic and practical engineering system. The power system described uses thermoelectric devices to convert heat into electricity. The heat source for the system is a nuclear reactor. Waste heat is rejected from the system to space by a radiator.

Chun, Young W.↗
NASA NTRS1991

Implementation issues for a compact 6 degree of freedom force reflecting handcontroller with cueing of modes

Teleoperated control requires a master human interface device that can provide haptic input and output which reflect the responses of a slave robotic system. The effort reported in this paper addresses the design and prototyping of a six degree-of-freedom (DOF) Cartesian coordinate hand controller for this purpose. The device design recommended is an XYZ stage attached to a three-roll wrist which positions a flight-type handgrip. Six degrees of freedom are transduced and control brushless DC motor servo electronics similar in design to those used in computer controlled robotic manipulators. This general approach supports scaled force, velocity, and position feedback to aid an operator in achieving telepresence. The generality of the device and control system characteristics allow the use of inverse dynamics robotic control methodology to project slave robot system forces and inertias to the operator (in scaled form) and at the same time to reduce the apparent inertia of the robotic handcontroller itself. The current control design, which is not multiple fault tolerant, can be extended to make flight control or space use possible. The proposed handcontroller will have advantages in space-based applications where an operator must control several robot arms in a simultaneous and coordinated fashion. It will also have applications in intravehicular activities (within the Space Station) such as microgravity experiments in metallurgy and biological experiments that require isolation from the astronauts' environment. For ground applications, the handcontroller will be useful in underwater activities where the generality of the proposed handcontroller becomes an asset for operation of many different manipulator types. Also applications will emerge in the Military, Construction, and Maintenance/Manufacturing areas including ordnance handling, mine removal, NBC (Nuclear, Chemical, Biological) operations, control of vehicles, and operating strength and agility enhanced machines. Future avionics applications including advanced helicopter and aircraft control may also become important.

Jacobus, Heidi↗
NASA NTRS1989

Super Smooth Optics for Extra-Solar Planet Detection

The goal of imaging planets around the nearby stars has important scientific significance but requires the use of advanced methods of controlling diffracted and scattered light. Over the last three years we have undertaken a study of coronagraphic methods of controlling diffracted light and of figuring hyper-contrast optics. Progress in these two general areas have led to a proposed space-based, 1.9 meter diameter coronagraphic telescope designed specifically for very high performance in the imaging of faint objects near bright sources. This instrument, called the Circumstellar Imaging Telescope (CIT), relies on a new high efficiency coronagraph design and the careful control of scattered light by extremely smooth optics. The high efficiency coronagraph uses focal plane apodization in order to concentrate diffracted light more efficiently in the pupil. This allows convenient removal of the diffracted light by masking off parts of the telescope pupil while not sacrificing the center of the field. Reductions of diffracted light by factors exceeding 1000 are not only possible but are required in order to detect extra-solar planets. Laboratory experiments with this new design have confirmed the theoretical diffraction reductions to the limits of the optics used (factors of about 300) . The extremely high efficiency of this coronagraph puts strong constraints on the narrow angle scattered light due to figure errors in the telescope mirror. Since planets orbiting nearby stars are expected at angular distances of about 1 arcsecond, it is in this small angular range in which scattering must be controlled. The figure errors responsible for scattering in this range come from mid-spatial frequencies corresponding to correlation lengths of about 10 cm on the primary mirror. A primary mirror about 15 times smoother than the Hubble Space Telescope mirror is required for the CIT. Laboratory experiments indicate that small test mirrors can be fabricated with existing technology which come within a factor of two of this requirement.

Terrile, Richard J.↗
NASA NTRS1989

Cryogenics for Space Observatories: Technology, Requirements, Issues

The ability to provide cooling at cryogenic temperatures is a critical enabling technology for many of the next generation of space-based observatories and instruments. This report discusses the state of cryogenics technology and identifies and categorizes the various methods of cooling.

Schember, Helene↗
NASA NTRS1986

FASAC Technical Assessment Report: Soviet Space Science Research

This report is the work of a panel of eight US scientists who surveyed and assessed Soviet research in the spare sciences. All of the panelists were very familiar with Soviet research through their knowledge of the published scientific literature and personal contacts with Soviet and other foreign colleagues. In addition, all of the panelists reviewed considerable additional open literature--scientific, and popular, including news releases. The specific disciplines of Soviet space science research examined in detail for the report were: solar-terrestrial research, lunar and planetary research, space astronomy and astrophysics, and, life sciences. The Soviet Union has in the past carried out an ambitious program in lunar exploration and, more recently, in studies of the inner planets, Mars and especially Venus. The Soviets have provided scientific data about the latter planet which has been crucial for studies of the planet's evolution. Future programs envision an encounter with Halley's Comet, in March 1986, and missions to Mars and asteroids. The Soviet programs in the life sciences and solar-terrestrial research have been long-lasting and systematically pursued. Much of the ground-based and space-based research in these two disciplines appears to be motivated by the requirement to establish long-term human habitation in near-Earth space. The Soviet contributions to new discoveries and understanding in observational space astronomy and astrophysics have been few. This is in significant contrast to the very excellent theoretical work contributed by Soviet scientists in this discipline.

Lanzerotti, L. J.↗
NASA NTRS1981

Yacht Race Monitoring

Observer Single-handed Transatlantic Race (OSTAR) participants were aided by a French-American space-based monitoring system which reported the yacht's positions throughout the race, and also served as an emergency locator service. Originating from NASA's Nimbus 6 Satellite, use of this system, called ARGOS made the OSTAR competition the most accurately reported sea race ever conducted. Each boat carried a portable transmitter allowing 88 new sources of oceanographic data available during the race.

Source record↗
NASA NTRS1988

Physical considerations relevant to HZE-particle transport in matter

High-energy, highly charged (HZE) heavy nuclei may seem at first sight to be an exotic type of radiation, only remotely connected with nuclear power generation. On closer examination it becomes evident that heavy-ion accelerators are being seriously considered for driving inertial confinement fusion reactors, and high-energy heavy nuclei in the cosmic radiation are likely to place significant constraints on satellite power system deployment and space-based power generation. The use of beams of heavy nuclei in an increasing number of current applications, as well as their importance for the development of the state of the art of the future, makes it necessary to develop at the same time a good understanding of their transport through matter.

NASA Program Biomedical Research↗
NASA NTRS1990

Binding of isolated plant lectin by rhizobia during episodes of reduced gravity obtained by parabolic flight

Development of a legume root nodule is a complex process culminating in a plant/bacterial symbiosis possessing the capacity for biological dinitrogen fixation. Formation of root nodules is initiated by the binding and stabilization of rhizobia to plant root hairs, mediated in part by a receptor/ligand recognition system composed of lectins on the plant root surface and lectin-binding sites on the rhizobial cell surface. The dinitrogen fixation activity of these root nodules may be an important feature of enclosed, space-based life support systems, and may provide an ecological method to recycle nitrogen for amino acid production. However, the effects on nodule development of varied gravitational fields, or of root nutrient delivery hardware, remain unknown. We have investigated the effects of microgravity on root nodule formation, with preliminary experiments focused upon the receptor/ligand component. Microgravity, obtained during parabolic flight aboard NASA 930, has no apparent effect on the binding of purified lectin to rhizobia, a result that will facilitate forthcoming experiments using intact root tissues.

manned↗
NASA NTRS1991

Waste treatment integration in space

The circumstances and criteria for space-based waste treatment bioregenerative life-support systems differ in many ways from those needed in terrestrial applications. In fact, the term "waste" may not even be appropriate in the context of nearly closed, cycling, ecosystems such as those under consideration. Because of these constraints there is a need for innovative approaches to the problem of "materials recycling". Hybrid physico-chemico-biological systems offer advantages over both strictly physico-chemico or biological approaches that would be beneficial to material recycling. To effectively emulate terrestrial cycling, the use of various microbial consortia ("assemblies of interdependent microbes") should be seriously considered for the biological components of such systems. This paper will examine the use of consortia in the context of a hybrid-system for materials recycling in space.

Waste Management/methods↗
NASA NTRS1990

Reproduction in the space environment: Part II. Concerns for human reproduction

Long-duration space flight and eventual colonization of our solar system will require successful control of reproductive function and a thorough understanding of factors unique to space flight and their impact on gynecologic and obstetric parameters. Part II of this paper examines the specific environmental factors associated with space flight and the implications for human reproduction. Space environmental hazards discussed include radiation, alteration in atmospheric pressure and breathing gas partial pressures, prolonged toxicological exposure, and microgravity. The effects of countermeasures necessary to reduce cardiovascular deconditioning, calcium loss, muscle wasting, and neurovestibular problems are also considered. In addition, the impact of microgravity on male fertility and gamete quality is explored. Due to current constraints, human pregnancy is now contraindicated for space flight. However, a program to explore effective countermeasures to current constraints and develop the required health care delivery capability for extended-duration space flight is suggested. A program of Earth- and space-based research to provide further answers to reproductive questions is suggested.

Review, Tutorial↗