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At least 127 records · Page 7

Early space experiments in materials processing

A comprehensive survey of the flight experiments conducted in conjunction with the United States Materials Processing in Space Program is presented. Also included are a brief description of the conditions prevailing in an orbiting spacecraft and the research implications provided by this unique environment. What was done and what was learned are summarized in order to serve as a background for future experiments. It is assumed that the reader has some knowledge of the physical sciences but no background in spaceflight experimentation or in the materials science per se.

Naumann, R. J.↗

Prediction Accuracy of Error Rates for MPTB Space Experiment

This paper addresses the accuracy of radiation-induced upset-rate predictions in space using the results of ground-based measurements together with standard environmental and device models. The study is focused on two part types - 16 Mb NEC DRAM's (UPD4216) and 1 Kb SRAM's (AMD93L422) - both of which are currently in space on board the Microelectronics and Photonics Test Bed (MPTB). To date, ground-based measurements of proton-induced single event upset (SEM cross sections as a function of energy have been obtained and combined with models of the proton environment to predict proton-induced error rates in space. The role played by uncertainties in the environmental models will be determined by comparing the modeled radiation environment with the actual environment measured aboard MPTB. Heavy-ion induced upsets have also been obtained from MPTB and will be compared with the "predicted" error rate following ground testing that will be done in the near future. These results should help identify sources of uncertainty in predictions of SEU rates in space.

Buchner, S. P.↗

SADE: A space experiment to demonstrate structural assembly

The Structural Assembly and Demonstration Experiment (SADE) demonstrates that the Shuttle is a suitable base for space construction; this includes a test of the Shuttle's control system to determine its performance when a long attached truss or beam is extended from the bay. Examples of Shuttle-related systems that will receive special attention are the RMS, the lighting system, and the crew assembly capabilities. A second purpose is to determine the extent to which the assembly results from the Neutral Buoyancy Simulator can be used to forecast the results of space assembly is determined. Finally, the SADE truss design will be validated by measuring the performance of the deployment, the special connectors, and the assembly methods.

Harrison, J. K.↗

Space experiments with particle accelerators

Electron and plasma beams and neutral gas plumes were injected into the space environment by instruuments on Spacelab 1, and various diagnostic measurements including television camera observations were performed. The results yield information on vehicle charging and neutralization, beam-plasma interactions, and ionization enhancement by neutral beam injection.

Obayashi, T.↗

Test and space experience with protoflight spacecraft

Based on system level test results, there appears to be some additional risk of space failures when a protoflight spacecraft is launched in lieu of a flight spacecraft. The space performance of all protoflight spacecraft to date has been satisfactory with failure rates slightly less than conventional flight spacecraft. The continued use of the protoflight concept is supported by this study.

Timmins, A. R.↗

Research study on materials processing in space experiment M512

A study program was conducted to clarify the role of gravity in the fluid mechanics of certain molten metal processes of potential significance to manufacturing in space. In particular, analyses were conducted of the M551 Metals Melting Experiment and the M553 Sphere Forming Experiment to be conducted in the M512 Facility onboard Skylab. The M551 experiment consisted of a study of electron beam welding of various metals, and the M553 experiment studied the formation of molten metal spheres by free-floating in a near zero-gravity environment. The analyses of these experiments and a comparison with ground-based and KC135 experimental results are presented.

Brashears, M. R.↗

Research study on materials processing in space experiment M512

A study program was conducted to clarify the role of gravity in the fluid mechanics of certain molten metal processes of potential significance to manufacturing in space. In particular, analyses were conducted of the M551 Metals Melting Experiment and the M553 Sphere Forming Experiment to be conducted in the M512 Facility onboard Skylab. The M551 experiment consisted of a study of electron beam welding of various metals, and the M553 experiment studied the formation of molten metal spheres by free-floating in a near zero-gravity environment. The analyses of these experiments and a comparison with ground-based and KC135 experimental results are presented.

Brashears, M. R.↗

An overview of the Evaluation of Oxygen Interaction with Materials-third phase (EOIM-3) experiment: Space Shuttle Mission 46

The interaction of the atomic oxygen (AO) component of the low earth orbit (LEO) environment with spacecraft materials has been the subject of several flight experiments over the past 11 years. The effect of AO interactions with materials has been shown to be significant for long-lived spacecraft such as Space Station Freedom and has resulted in materials changes for externally exposed surfaces. The data obtained from previous flight experiments, augmented by limited ground-based evaluation, have been used to evaluate hardware performance and select materials. Questions pertaining to the accuracy of this data base remain, resulting from the use of long-term ambient density models to estimate the O-atom fluxes and fluences needed to calculate materials reactivity in short-term flight experiments. The EOIM-3 flight experiment was designed to produce benchmark AO reactivity data and was carried out during STS-46. Ambient density measurements were made with a quadrupole mass spectrometer which was calibrated for AO measurements in a unique ground-based test facility. The combination of these data with the predictions of ambient density models allows an assessment of the accuracy of measured reaction rates on a wide variety of materials, many of which had never been tested in LEO before. The mass spectrometer is also used to obtain a better definition of the local neutral and plasma environments resulting from interaction of the ambient atmosphere with various spacecraft surfaces. In addition, the EOIM-3 experiment was designed to produce information on the effects of temperature, mechanical stress, and solar exposure on the AO reactivity of a wide range of materials. An overview of the EOIM-3 methods and results are presented.

Leger, Lubert J.↗

Observations of electron beam structure in space experiments

Observations of a 100-mA, 1-keV electron beam were made with a low light level TV system and other instruments aboard the space shuttle STS 3 in March 1982. When fired at a moderate pitch angle with respect to the magnetic field, the beam electrons initially moved outward along a classical helical trajectory. Within a short distance, however, the beam electrons were deflected away from the helical trajectory into paths parallel to magnetic field lines threading the primary helix. This resulted in the formation of a thin-walled, cylindrical electron beam structure having a radius equal to the primary beam gyroradius. This structure, which is consistent with earlier laboratory vacuum chamber observations and recent two-dimensional computer electrostatic plasma simulations, has important implications for determining the extent to which pulsed electron beams can radiate electromagnetic energy in the ionosphere.

Banks, Peter M.↗

Modular Avionics Concept Developed for Microgravity Space Experiments: FEANICS

The Flow Enclosure Accommodating Novel Investigations in Combustion of Solids (FEANICS) is a facility being developed at the NASA Glenn Research Center that will be integrated into the Combustion Integrated Rack onboard the International Space Station. FEANICS will support various experimental studies of solid combustion in a microgravity environment. The experiments will vary, and the FEANICS facility hardware combined with the Combustion Integrated Rack hardware is designed to meet the science requirements of the individual experiments.

Hausmann, Clifford R.↗

Space Experiments with Particle Accelerators (SEPAC)

Plans for SEPAC, an instrument array to be used on Spacelab 1 to study vehicle charging and neutralization, beam-plasma interaction in space, beam-atmospheric interaction exciting artificial aurora and airglow, and the electromagnetic-field configuration of the magnetosphere, are presented. The hardware, consisting of electron beam accelerator, magnetoplasma arcjet, neutral-gas plume generator, power supply, diagnostic package (photometer, plasma probes, particle analyzers, and plasma-wave package), TV monitor, and control and data-management unit, is described. The individual SEPAC experiments, the typical operational sequence, and the general outline of the SEPAC follow-on mission are discussed. Some of the experiments are to be joint ventures with AEPI (INS 003) and will be monitored by low-light-level TV.

Obayashi, T.↗

The Annular Suspension and Pointing (ASP) system for space experiments and predicted pointing accuracies

An annular suspension and pointing system consisting of pointing assemblies for coarse and vernier pointing is described. The first assembly is attached to a carrier spacecraft (e.g., the space shuttle) and consists of an azimuth gimbal and an elevation gimbal which provide 'coarse' pointing. The second or vernier pointing assembly is made up of magnetic actuators of suspension and fine pointing, roll motor segments, and an instrument or experiment mounting plate around which is attached a continuous annular rim similar to that used in the annular momentum control device. The rim provides appropriate magnetic circuits for the actuators and the roll motor segments for any instrument roll position. The results of a study to determine the pointing accuracy of the system in the presence of crew motion disturbances are presented. Typical 3 sigma worst-case errors are found to be of the order of 0.001 arc-second.

Anderson, W. W.↗

The ISES: A non-intrusive medium for in-space experiments in on-board information extraction

The Information Science Experiment System (ISES) represents a new approach in applying advanced systems technology and techniques to on-board information extraction in the space environment. Basically, what is proposed is a 'black box' attached to the spacecraft data bus or local area network. To the spacecraft the 'black box' appears to be just another payload requiring power, heat rejection, interfaces, adding weight, and requiring time on the data management and communication system. In reality, the 'black box' is a programmable computational resource which eavesdrops on the data network, taking and producing selectable, real-time science data back on the network. This paper will present a brief overview of the ISES Concept and will discuss issues related to applying the ISES to the polar platform and Space Station Freedom. Critical to the operation of ISES is the viability of a payload-like interface to the spacecraft data bus or local area network. Study results that address this question will be reviewed vis-a-vis the solar platform and the core space station. Also, initial results of processing science and other requirements for onboard, real-time information extraction will be presented with particular emphasis on the polar platform. Opportunities for a broader range of applications on the core space station will also be discussed.

Murray, Nicholas D.↗

Early space experiments in materials processing: Future programs

A list of the present state of knowledge in materials processing is presented. The fluid behavior in a low gravity environment is summarized. Materials processing in the Space Transportation System facility is discussed. Prospects for space commercialization are reported.

Source record↗

Vibration isolation technology: Sensitivity of selected classes of space experiments to residual accelerations

Progress performed on each task is described. Order of magnitude analyses related to liquid zone sensitivity and thermo-capillary flow sensitivity are covered. Progress with numerical models of the sensitivity of isothermal liquid zones is described. Progress towards a numerical model of coupled buoyancy-driven and thermo-capillary convection experiments is also described. Interaction with NASA personnel is covered. Results to date are summarized and they are discussed in terms of the predicted space station acceleration environment. Work planned for the second year is also discussed.

Alexander, J. Iwan D.↗

Implications of RFI at L-Band on Passive Microwave Remote Sensing of Soil Moisture from Space: Experience with ESTAR During SGP97

Passive microwave remote sensing in the protected band at 1.413 GHz (L-band) is important for monitoring parameters of the ocean and land surface such as soil moisture and sea surface salinity. These parameters are needed for understanding energy exchange between the surface and atmosphere and therefore are important for improving our understanding of weather and climate change. Although the band at 1.413 GHz is protected for passive use, airborne radiometers experience problems with RFI. For example, during the Southern Great Plains Experiment (1997) the ESTAR radiometer experienced significant RFI associated with airports, presumably air traffic control radar. This is a potential problem for future sensors in space planned for remote sensing of the earth surface in this frequency band.

LeVine, David M.↗

Space Experiment on Tuber Development and Starch Accumulation for CELSS

Potato explants (leaf, small stem section, and axillary bud), flown on STS-73, developed tubers of 1.5 cm diameter and 1.7 g mass during the 16 day period of spaceflight. The experiment was undertaken in the ASTROCULTURE(Trademark) experiment package under controlled temperature, humidity, lighting, and carbon dioxide concentrations. The tubers formed in the explant system under microgravity had the same gross morphology, the same anatomical configuration of cells and tissues, and the same sizes, shapes, and surface character of starch granules as tubers formed in a 1 g environment. The total accumulation of starch and other energy containing compounds was singular in space flight and ground control tubers. Enzyme activity of starch synthase, starch phosphorylase, and total hydrolase was similar in spaceflight and ground controls but activity of ADP-glucose pyrophosphorylase was reduced in the spaceflight tuber tissue. This experiment documented that potatoes will metabolize and accumulate starch as effectively in spaceflight as on the ground and thus this data provides the potential for effective utilization of potatoes in life support systems of space bases.

Tibbitts,Theodore W.↗

Biorhythms and space experiments with nonhuman primates

Man's response to exposure to spaceflight and weightlessness is expressed in physiological adjustments which involve his health and ability to function. The amplitude and periodicity of fluctuations in biological processes affect various functions and responses to provocative stimuli. Primates and other species are subjected to tests to determine the consequences of an altered biorhythm on work and performance, emotional stability, biomedical evaluation in space, the ability to cope with the unexpected, and susceptibility to infection, toxicity, radiation, drugs, and stress. Factors in the environment or operational setup which can change the physiological baseline must be determined and controlled.

Winget, C. M.↗