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At least 271 records · Page 15

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NASA NTRS1990

Microgravity strategic plan, 1990

The mission of the NASA Microgravity program is to utilize the unique characteristics of the space environment, primarily the near absence of gravity, to understand the role of gravity in materials processing, and to demonstrate the feasibility of space production of improved materials that have high technological, and possible commercial, utility. The following five goals for the Microgravity Program are discussed: (1) Develop a comprehensive research program in fundamental sciences, materials science, and biotechnology for the purpose of attaining a structured understanding of gravity dependent physical phenomena in both Earth and non-Earth environments; (2) Foster the growth of interdisciplinary research community to conduct research in the space environment; (3) Encourage international cooperation for the purpose of conducting research in the space environment; (4) Utilize a permanently manned, multi-facility national microgravity laboratory in low-Earth orbit to provide a long-duration, stable microgravity environment; (5) Promote industrial applications of space research for the development of new, commercially viable products, services, and markets resulting from research in the space environment.

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NASA NTRS1991

A fundamental study of nucleate pool boiling under microgravity

An experimental study of incipient boiling in short-term microgravity and with a/g = +/- 1 for pool boiling was performed. Calibrated thin gold films sputtered on a smoothly polished quartz surface were used simultaneously for thermal resistance measurements and heating of the boiling surface. The gold films were used for both transient and quasi-steady heating surface temperature measurements. Two test vessels were constructed for precise measurement and control of fluid temperature and pressure: a laboratory pool boiling vessel for the a/g = +/- experiments and a pool boiling vessel designed for the 131 m free-fall in the NASA Lewis Research Center Microgravity Research Facility for the microgravity tests. Measurements included the heater surface temperature, the pressure near the heating surface, and the bulk liquid temperatures. High speed photography was used in the experiments. With high quality microgravity and the measured initial temperature of the quiescent test fluid, R113, the temperature distribution in the liquid at the moment of boiling inception resulting from an imposed step in heat flux is known with a certainty not possible previously. The types of boiling propagation across the large flat heating surface are categorized; the conditions necessary for their occurrence are described. Explosive boiling propagation with a striking pattern of small scale protuberances over the entire vapor mass periphery not observed previously at low heat flux levels is described. For the heater surface with a/g = -1, a step in the heater surface temperature of short duration was imposed. The resulting liquid temperature distribution at the moment of boiling inception was different from that obtained with a step in heat flux.

Ervin, Jamie S.↗

NASA NTRS1990

United States microgravity programs

The U.S. Microgravity Program encompasses research initiatives of the NASA Office of Space Science and Applications and Office of Commercial Programs. NASA involvement in space missions extends to the U.S Microgravity Laboratory, the International Microgravity Laboratory, the Space Life Sciences Mission, and planned activities aboard the Japanese and German Spacelab missions. Flight programs under the aegis of NASA's Centers for the Commercial Development of Space will employ the Space Shuttle-based Commercial Middeck Augmentation Module and the Suborbital and Orbital Expendable Launch Vehicles. The projected Space Station will include a significant microgravity program.

Ott, Richard H.↗

NASA NTRS1990

Combustion Phenomena in Relationship to Microgravity Research

The conservation equations of combustion are presented, with relevant nondimensional parameters identified, for focusing on the role of buoyancy in combustion processes. The objective is to indicate ways in which microgravity combustion experiments enable regimes of fluid mechanics, not readily investigated in combustion at normal gravity, to be studied more carefully for chemically reacting flows with heat release. Descriptions are given of self-extinguishing flames, of flames balls, of double flames, and of the slow regime of droplet combustion, as examples in which microgravity experiments have revealed new combustion phenomena. A classification of experiments is offered, concerning combustion regimes and flow regimes, within which microgravity combustion studies can be placed. Projects on premixed flame propagation, gas-jet diffusion flames, flame spread, smoldering combustion, and droplet combustion are considered, within this classification, as potential areas for future advances in understanding of combustion phenomena through microgravity experiments.

Williams, Forman A.↗

NASA NTRS1991

The microgravity environment of the Space Shuttle Columbia middeck during STS-32

Four hours of three-axis microgravity accelerometer data were successfully measured at the MA9F locker location in the Orbiter middeck of Columbia as part of the Microgravity Disturbances Experiment (MDE) on STS-32. These data were measured using the Honeywell In-Space Accelerometer, a small three-axis accelerometer that was hard-mounted onto the Fluid Experiment Apparatus to record the microgravity environment at the exact location of the MDE. Data were recorded during specific mission events such as Orbiter quiescent periods, crew exercise on the treadmill, and numerous Orbiter engine burns. Orbiter background levels were measured to be in the 3 x 10(exp -5) to 2 x 10(exp -4) G range, treadmill operations in the 6 x 10(exp -4) to 5 x 10(exp -3) G range, and Orbiter engine burns from 4 x 10(exp -3) to in excess of 1 x 10(exp -2) G. These data represent some of the first microgravity accelerometer data ever recorded in the middeck area of the Orbiter.

Dunbar, Bonnie J.↗

NASA NTRS1992

Microgravity effects on standardized cognitive performance measures

The purpose of this experiment, selected to fly on the International Microgravity Laboratory (IML-2) Spacelab mission, is to determine the effects of microgravity upon the cognitive skills which are critical to successful performance of many tasks on board the Space Shuttle. Six tests from the Unified Tri-service Cognitive Performance Assessment Battery (UTC-PAB) will be administered to the Mission Specialists to fulfill the goals of this experiment. These tests are based upon current theoretical models of human performance and the hypothesized effects of microgravity. The principle objective is the identification of the effects of microgravity upon specific information processing skills affecting performance from those of fatigue and shifts in work/rest cycles. Multiple measures of both short and long term fatigue will be obtained and used as a major independent variable for the analysis of these performance data. Scientific supporting studies will determine optimum practice and performance testing schedules for the astronauts. The same tests will be used post-flight to collect data on the recovery of any cognitive performance impairment compared with pre-flight, baseline levels.

Schiflett, Samuel G.↗

NASA NTRS1991

Microgravity Program strategic plan, 1991

The all encompassing objective of the NASA Microgravity Program is the use of space as a lab to conduct research and development. The on-orbit microgravity environment, with its substantially reduced buoyancy forces, hydrostatic pressures, and sedimentation, enables the conduction of scientific studies not possible on Earth. This environment allows processes to be isolated and controlled with an accuracy that cannot be obtained in the terrestrial environment. The Microgravity Science and Applications Div. has defined three major science categories in order to develop a program structure: fundamental science, including the study of the behavior of fluids, transport phenomena, condensed matter physics, and combustion science; materials science, including electronic and photonic materials, metals and alloys, and glasses and ceramics; and biotechnology, focusing on macromolecular crystal growth as well as cell and molecular science. Experiments in these areas seek to provide observations of complex phenomena and measurements of physical attributes with a precision that is enabled by the microgravity environment.

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NASA NTRS1991

An investigation of flame spread over shallow liquid pools in microgravity and nonair environments

Experiments of interest to combustion fundamentals and spacecraft fire safety investigated flame spread of alcohol fuels over shallow, 15 cm diameter pools in a 5.2 sec free-fall, microgravity facility. Results showed that, independent O2 concentrations, alcohol fuel, and diluent types, microgravity flame spread rates were nearly identical to those corresponding normal-gravity flames for conditions where the normal gravity flames spread uniformly. This similarity indicated buoyancy-related convection in either phase does not affect flame spread, at least for the physical scale of the experiments. However, microgravity extinction coincided with the onset conditions for pulsating spread in normal gravity, implicating gas phase, buoyant flow as a requirement for pulsating spread. When the atmospheric nitrogen was replaced with argon, the conditions for the onset of normal-gravity pulsating flame spread and microgravity flame extinction were changed, in agreement with the expected lowering of the flash point through the thermal properties of the diluent. Helium-diluted flames, however, showed unexpected results with a shift to apparently higher flash-point temperatures and high normal gravity pulsation amplitudes.

Ross, Howard D.↗

NASA NTRS1991

Exercise training - Blood pressure responses in subjects adapted to microgravity

Conventional endurance exercise training that involves daily workouts of 1-2 hr duration during exposure to microgravity has not proven completely effective in ameliorating postexposure orthostatic hypotension. Single bouts of intense exercise have been shown to increase plasma volume and baroreflex sensitivity in ambulatory subjects through 24 hr postexercise and to reverse decrements in maximal oxygen uptake and syncopal episodes following exposure to simulated microgravity. These physiological adaptations to acute intense exercise were opposite to those observed following exposure to microgravity. These results suggest that the 'exercise training' stimulus used to prevent orthostatic hypotension induced by microgravity may be specific and should be redefined to include single bouts of maximal exercise which may provide an acute effective countermeasure against postflight hypotension.

Convertino, Victor A.↗

NASA NTRS1992

The potential impact of microgravity science and technology on education

The development of educational support materials by NASA's Microgravity Science and Applications Division is discussed in the light of two programs. Descriptions of the inception and application possibilities are given for the Microgravity-Science Teacher's Guide and the program of Undergraduate Research Opportunities in Microgravity Science and Technology. The guide is intended to introduce students to the principles and research efforts related to microgravity, and the undergraduate program is intended to reinforce interest in the space program. The use of computers and electronic communications is shown to be an important catalyst for the educational efforts. It is suggested that student and teacher access to these programs be enhanced so that they can have a broader impact on the educational development of space-related knowledge.

Wargo, M. J.↗

NASA NTRS1992

Effects of microgravity on the interaction of vestibular and optokinetic nystagmus in the vertical plane

The extent to which the slow phase velocity (SPV) of nystagmus elicited by a vertical optokinetic stimulation with constant velocity could be modulated by sinusoidal angular motion in the vertical plane was investigated under normal gravity condition and during the microgravity period of parabolic flight. In normal gravity, when the angular head motion and the optokinetic stimulation were in the same direction, the peak SPV was slower than the velocity of the optokinetic display. When the head motion and the optokinetic stimulation were in opposite directions, the peak SPV was equal to the velocity of the optokinetic display. In microgravity, the peak SPV was approximately equal to the velocity of the optokinetic display when head rotation and optokinetic stimulation were in the same direction, and was faster than the velocity of the optokinetic dispaly when head rotation and optokinetic stimulation were in opposite directions. In addition, the interaction of vestibular and optokinetic nystagmus was found to be nonlinear in microgravity, especially when the optokinetic stimulation was directed downward. These results suggest an interaction between the vestibular and the optokinetic systems modulated as a function of the gravitational state, and support the observation that visual input is more effective in reducing sensory conflict experienced in microgravity.

Clement, Gilles↗

NASA NTRS1992

Early use of Space Station Freedom for NASA's Microgravity Science and Applications Program

The paper describes microgravity science opportunities inherent to the restructured Space Station and presents a synopsis of the scientific utilization plan for the first two years of ground-tended operations. In the ground-tended utilization mode the Space Station is a large free-flyer providing a continuous microgravity environment unmatched by any other platform within any existing U.S. program. It is pointed out that the importance of this period of early Space Station mixed-mode utilization between crew-tended and ground-tended approaches is of such magnitude that Station-based microgravity science experiments many become benchmarks to the disciplines involved. The traffic model that is currently being pursued is designed to maximize this opportunity for the U.S. microgravity science community.

Rhome, Robert C.↗

NASA NTRS1992

Toward a microgravity research strategy

Recommendations of the Committee on Microgravity Research (CMGR) of the Space Studies Board of the National Research Council are found in the Summary and Recommendations in the front of the report. The CMGR recommends a long-range research strategy. The main rationale for the microgravity research program should be to improve our fundamental scientific and technical knowledge base, particularly in the areas that are likely to lead to improvements in processing and manufacturing on earth. The CMGR recommends research be categorized as Biological science and technology, Combustion, Fluid science, Fundamental phenomena, Materials, and Processing science and technology. The committee also recommends that NASA apply a set of value criteria and measurement indicators to define the research and analysis program more clearly. The CMGR recommends that the funding level for research and analysis in microgravity science be established as a fixed percentage of the total program of NASA's Microgravity Science and Applications Division in order to build a strong scientific base for future experiments. The committee also recommends a cost-effective approach to experiments. Finally the CMGR recommends that a thorough technical review of the centers for commercial development of space be conducted to determine the quality of their activities and to ascertain to what degree their original mission has been accomplished.

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NASA NTRS1993

Laser diagnostics for microgravity droplet studies

Rapid advances have recently been made in numerical simulation of droplet combustion under microgravity conditions, while experimental capabilities remain relatively primitive. Calculations can now provide detailed information on mass and energy transport, complex gas-phase chemistry, multi-component molecular diffusion, surface evaporation and heterogeneous reaction, which provides a clearer picture of both quasi-steady as well as dynamic behavior of droplet combustion. Experiments concerning these phenomena typically result in pictures of the burning droplets, and the data therefrom describe droplet surface regression along with flame and soot shell position. With much more precise, detailed, experimental diagnostics, significant gains could be made on the dynamics and flame structural changes which occur during droplet combustion. Since microgravity experiments become increasingly more expensive as they progress from drop towers and flights to spaceborne experiments, there is a great need to maximize the information content from these experiments. Sophisticated measurements using laser diagnostics on individual droplets and combustion phenomena are now possible. These include measuring flow patterns and temperature fields within droplets, vaporization rates and vaporization enhancement, radical species profiling in flames and gas-phase flow-tagging velocimetry. Although these measurements are sophisticated, they have undergone maturation to the degree where with some development, they are applicable to studies of microgravity droplet combustion. This program beginning in September of 1992, will include a series of measurements in the NASA Learjet, KC-135 and Drop Tower facilities for investigating the range of applicability of these diagnostics while generating and providing fundamental data to ongoing NASA research programs in this area. This program is being conducted in collaboration with other microgravity investigators and is aimed toward supplementing their experimental efforts.

Winter, Michael↗

NASA NTRS1992

Microgravity fluid physics research in the Space Station Freedom era

Microgravity fluid physics covers an exciting range of established and potential fields of scientific research. Areas in which the Microgravity Science and Applications Division of NASA's Office of Space Science and Applications is currently supporting research include: multiphase flow and phase change heat transfer, behavior of granular media and colloids; and interface dynamics, morphological stability, and contact line phenomena. As they contribute to our knowledge of fluid behavior, advances in these areas will enhance our understanding of materials processing on Earth and in space, and will contribute to technologies as diverse as chemical extraction, the prediction of soil behavior in earthquakes, and the production of oil reservoirs. NASA' s primary platform for research in microgravity fluid physics will soon be the Fluid Physics/Dynamics Facility on Space Station Freedom. This facility shares a rack for control and utilities with the Modular Combustion Facility, and has one rack for experiment-unique instruments. It is planned to change out the content of the experiment-unique rack at intervals on the order of one year. In order to obtain a maximum return on the operation of the facility during these intervals, the research community must carefully plan and coordinate an effort that brings the efforts of many investigators to bear on problems of particular importance. NASA is currently working with the community to identify research areas in which microgravity can make a unique and valuable contribution, and to build a balanced program of research around these areas or thrusts. Selections will soon be made from our first solicitation for research in fluid dynamics and transport phenomena. These solicitations will build the research community that will make Space Station Freedom a catalyst for scientific and technological discovery, and offer U.S. scientists in many disciplines a unique opportunity to participate in space science.

Carpenter, Bradley M.↗

NASA NTRS1993

Glovebox - an Excellent Environment for Microgravity Experiments

The use of the Spacelab Glovebox on the recent First United States Microgravity Laboratory (USML-1) mission and the success with which the facility accommodated a large number of microgravity experiments are discussed. Sixteen Materials Science experiments were developed and successfully operated during the first microgravity usage of this new glovebox in space. This facility has a closed working volume to safely contain loose particles and droplets that may be inadvertently freed in setting up or conducting the experiments. The facility also offers an excellent photographic laboratory for observing and recording science data. The USML-1 Spacelab Globebox was a highly successful project that provided the motivation to begin the development of an Orbiter Middeck Glovebox and also provided valuable experience in setting the requirements for the Space Station Freedom Microgravity Science Glovebox (MSG).

Chassay, Roger P.↗

NASA NTRS1993

A feasibility study of a microgravity enhancement system for Space Station Freedom

The current low frequency microgravity requirements for Space Station Freedom (SSF) call for a level of less than 1 micro-g over 50 percent of all the laboratory racks for continuous periods of 30 days for at least 180 days per year. While this requirement is attainable for some of the laboratory modules for the Permanently Manned Configuration (PMC), it cannot be met for the Man-Tended Configuration (MTC). To improve the microgravity conditions in the laboratory modules, the Microgravity Enhancement System (MESYS) will apply a continuous thrust to SSF, to negate the disturbing gravity gradient and drag forces. The MESYS consists of a sensor, continuous throttle-able thrusters, and a control system. Both a proof mass system and nano-g accelerometer were evaluated for use as the sensor. The net result of the MESYS will be to shift the microgravity contours from the center of mass to a chosen location. Results indicate the MESYS is not feasible for the MTC since it will require 5073 kg of hydrazine fuel and 7660 watts of electrical power for 30 days of operation during average atmospheric conditions. For the PMC, the MESYS is much more practical, since only 4008 kg of fuel and 5640 watts of electrical power will be required for 30 days of operation during average atmospheric conditions.

Diamond, Preston S.↗

NASA NTRS1993

Microgravity acceleration measurement environment characterization

The Space Acceleration Measurement System (SAMS) is a general-purpose instrumentation system designed to measure the accelerations onboard the shuttle Orbiter and shuttle/Spacelab vehicles. These measurements are used to support microgravity experiments and investigations into the microgravity environment of the vehicle. Acceleration measurement can be made at locations remote from the SAMS main instrumentation unit by the use of up to three remote triaxial sensor heads. The SAMS was developed by NASA's Lewis Research Center (LeRC) in support of NASA's microgravity science programs. In the past, numerous acceleration measurement systems have flown on various space missions. These systems were tailored to measure accelerations for a narrow set of requirements and were limited in bandwidth, dynamic range, and recording capability. In addition, these systems were mission-peculiar and not easily modified for other applications or missions. The result has been an inability to accurately assess the expected microgravity environment prior to a mission for a particular experiment and/or location. The prime science objective for SAMS on the SL-J mission will be to measure the accelerations experienced by a multitude of experiments in the two racks of the Japanese First Materials Processing Test (FMPT). The FMPT consists of a variety of materials science and life science experiments contained in racks no. 7 and no. 10. The SAMS data will be made available to the FMPT principal investigators after the mission for their analysis with the FMPT data. A secondary science objective for SAMS will be the characterization of the acceleration environment of the Spacelab module. This will include an analysis of the acceleration transfer function of the Spacelab module which will utilize the FMPT acceleration measurement along with measurements at the rack no. 9 structure. Another analytical effort to be undertaken is a general characterization of the acceleration environment of the Spacelab as an orbiting laboratory. These analysis efforts will be in conjunction with similar measurements and analyses on other SAMS Spacelab missions.

Delombard, Richard↗