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NASA NTRS1995

Dynamics and control of instrumented harmonic drives

Since torque in harmonic drives is transmitted by a pure couple, harmonic drives do not generate radial forces and therefore can be instrumented with torque sensors without interference from radial forces. The installation of torque sensors on the stationary component of harmonic drives (the Flexipline cup in this research work) produce backdrivability needed for robotic and telerobotic compliant maneuvers. Backdrivability of a harmonic drive, when used as torque increaser, means that the output shaft can be rotated via finite amount of torque. A high ratio harmonic drive is non-backdrivable because its output shaft cannot be turned by applying a torque on it. This article first develops the dynamic behavior of a harmonic drive, in particular the non-backdrivability, in terms of a sensitivity transfer function. The instrumentation of the harmonic drive with torque sensor is then described. This leads to a description of the control architecture which allows modulation of the sensitivity transfer function within the limits established by the closed-loop stability. A set of experiments on an active hand controller, powered by a DC motor coupled to an instrumented harmonic drive, is given to exhibit this method's limitations.

NASA Discipline Space Human Factors↗

NASA NTRS1986

Large area space qualified thermoelectrically (TE) cooled HgCdTe MW photovoltaic detectors for the Halogen Occultation Experiment (HALOE)

Large-area, HgCdTe MW photovoltaic detectors have been developed for the NASA-HALOE instrument scheduled for operation on the Upper Atmospheric Research Satellite. The photodiodes will be TE-cooled and were designed to operate in the 5.1-5.4 micron band at 185 K to measure nitric oxide concentrations in the atmosphere. The active area required 15 micron thick devices and a full backside common contact. Reflections from the backside contact doubled the effective thickness of the detectors. Optical interference from reflections was eliminated with a dual layer front surface A/R coating. Bakeout reliability was optimized by having Au metallization for both n and p interconnects. Detailed performance data and a model for the optical stack are presented.

Norton, P. W.↗

NASA NTRS1973

Skylab experiments. Volume 6: Mechanics

Skylab program activities are presented in a form adapted to instruction of high school students. The overall goals of the program are discussed. The specific accomplishments of the mechanics investigations are described. The subjects involved are as follows: (1) evaluation of mobility aids, (2) mass measurement devices, and (3) space guidance crew/vehicle disturbances.

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NASA NTRS1985

Experiences with neutral buoyance testing mockups

Contingency operations with neutral bouyancy simulation on a space platform is considered. Some task simulated are aft payload port deployment and retraction, removal and replacement of the control moment cyro, and deployment of the manual hand crank appendage. It is decided that crewmen can perform fine motor activities when simple aids are provided, certain tasks can be accomplished with less efforts when the crewman is afforded additional mobility, manual translation of large mass items is feasible, and that during the installation of replaceable units application of alignment indicators provide significant assistance to crewmen.

Dellacamera, B.↗

NASA NTRS1994

TRMM-related research: Tropical rainfall and energy analysis experiment

The overall science objective of the participation in TRMM is the determination of daily rainfall and latent heating in the tropical atmosphere using TRMM and complementary spacecraft observations. The major focus these first three years has been to extend, in space and time, the TRMM satellite observations of rainfall. Observations from TRMM active and passive microwave radiometers will provide the fundamental observations for understanding the hydrological cycle of the tropics. Due to the orbit of the TRMM satellite and the extreme variability of convective rain systems, the TRMM observations provide rainfall estimates representative of a one month period. Monthly mean rainfall rates provide valuable information; however, this time scale limitation neglects the great value of the data towards a better understanding of the physics of tropical convection. Many tropical periodicities will not be characterized by these monthly averages, e.g. diurnal cycles, the 4-6 day easterly waves, and the 30 to 60 day cycle. In the spatial domain, due to its orbit, the TRMM satellite will over-fly many convective systems only once. Indeed, some precipitating systems will not be sampled at all. Observations from geostationary satellites can be used to extend the TRMM observations to smaller time and space scales. Although geostationary satellites cannot probe the interiors of precipitating systems, they do observe their life cycles. To acquire information on cloud water content and rain rate, it is proposed to combine geostationary and other satellite observations with the TRMM satellite measurements.

Suomi, Verner E.↗

NASA NTRS1993

Life Sciences Accomplishments 1994

The NASA Life and Biomedical Sciences and Applications Division (LBSAD) serves the Nation's life sciences community by managing all aspects of U.S. space-related life sciences research and technology development. The activities of the Division are integral components of the Nation's overall biological sciences and biomedical research efforts. However, NASA's life sciences activities are unique, in that space flight affords the opportunity to study and characterize basic biological mechanisms in ways not possible on Earth. By utilizing access to space as a research tool, NASA advances fundamental knowledge of the way in which weightlessness, radiation, and other aspects of the space-flight environment interact with biological processes. This knowledge is applied to procedures and technologies that enable humans to live and work in and explore space and contributes to the health and well-being of people on Earth. The activities of the Division are guided by the following three goals: Goal 1) Use microgravity and other unique aspects of the space environment to enhance our understanding of fundamental biological processes. Goal 2) Develop the scientific and technological foundations for supporting exploration by enabling productive human presence in space for extended periods. Goal 3) Apply our unique mission personnel, facilities, and technology to improve education, the quality of life on Earth, and U.S. competitiveness. The Division pursues these goals with integrated ground and flight programs involving the participation of NASA field centers, industry, and universities, as well as interactions with other national agencies and NASA's international partners. The published work of Division-sponsored researchers is a record of completed research in pursuit of these goals. During 1993, the LBSAD instituted significant changes in its experiment solicitation and peer review processes. For the first time, a NASA Research Announcement (NRA) was released requesting proposals for ground-based and flight research for all programs. Areas of particular interest to NASA were defined Proposals due April 29, 1994, will be peer reviewed - externally for scientific merit. This annual NRA process is now the mechanism for recruiting both extramural and intramural investigations. As an overview of LBSAD activities in 1993, this accomplishments document covers each of the major organizational components of the Division and the accomplishments of each. The second section is a review of the Space Life Sciences Research programs Space Biology, Space Physiology and Countermeasures, Radiation Health, Environmental Health, Space Human Factors, Advanced Life Support, and Global Monitoring and Disease Prediction, The third section, Research in Space Flight, describes the substantial contributions of the Spacelab Life Sciences 2 (SLS-2) mission to life sciences research and the significant contributions of the other missions flown in 1993, along with plans for future missions. The Division has greatly expanded and given high priority to its Education and Outreach Programs, which are presented in the fourth section. The fifth and final section, Partners for Space, shows the Divisions Cooperative efforts with other national and international agencies to achieve common goals, along with the accomplishments of joint research and analysis programs.

Burnell, Mary Lou↗

NASA NTRS2002

Bubble Experiments on the Hydrodynamic Focusing Bioreactor-Space (HFB-S)

The Hydrodynamic Focusing Bioreactor-Space (HFB-S) is being developed as a drop-in replacement for the Rotating Wall Perfused Vessel (RWPV) bioreactor currently planned for use on the International Space Station (ISS). Only the vessel itself is proposed for change, the supporting hardware will remain the same. These bioreactors are used for the growth of three-dimensional tissue culture that cannot be done in normal gravity labs. The bioreactors provide a continual supply of oxygen for cell growth, as well as periodic replacement of cell culture media with nutrients. The RWPV has had many successful flights on the space shuttle, but longer duration missions onboard the Mir Space Station resulted in bubbles inside the vessel that were detrimental to the science. It is believed that procedural changes can prevent bubble formation, but the HFB-S must not only provide a mechanism of bubble removal, but must also meet strict requirements for a low-shear environment and uniform oxygen concentration distribution for optimum cell tissue growth. A detailed technical objective (DTO) flight on the space shuttle to fully evaluate the HFB-S is currently in the planning stages. Ground-based activities are also underway to quanitify the characteristics of the HFB-S. Computational studies are being used to predict the internal fluid flow and cell trajectories. These computations will be compared to ground-based flow visualization experiments. Comparative studies of ground-based cell growth between the RWPV and the HFB-S are also in progress. These studies have shown that the HFB-S functions well as a bioreactor in normal gravity. Bubble motion and bubble removal are being studied using computational predictions as well as experimental validation.

Charles Niederhaus↗

NASA NTRS2001

Space flight affects magnocellular supraoptic neurons of young prepuberal rats: transient and permanent effects

Effects of microgravity on postural control and volume of extracellular fluids as well as stress associated with space flight may affect the function of hypothalamic neurosecretory neurons. Since environmental modifications in young animals may result in permanent alterations in neuroendocrine function, the present study was designed to determine the effect of a space flight on oxytocinergic and vasopressinergic magnocellular hypothalamic neurons of prepuberal rats. Fifteen-day-old Sprague-Dawley female rats were flown aboard the Space Shuttle Columbia (STS-90, Neurolab mission, experiment 150) for 16 days. Age-matched litters remained on the ground in cages similar to those of the flight animals. Six animals from each group were killed on the day of landing and eight animals from each group were maintained under standard vivarium conditions and killed 18 weeks after landing. Several signs of enhanced transcriptional and biosynthetic activity were observed in magnocellular supraoptic neurons of flight animals on the day of landing compared to control animals. These include increased c-Fos expression, larger nucleoli and cytoplasm, and higher volume occupied in the neuronal perikaryon by mitochondriae, endoplasmic reticulum, Golgi apparatus, lysosomes and cytoplasmic inclusions known as nematosomes. In contrast, the volume occupied by neurosecretory vesicles in the supraoptic neuronal perikarya was significantly decreased in flight rats. This decrease was associated with a significant decrease in oxytocin and vasopressin immunoreactive levels, suggestive of an increased hormonal release. Vasopressin levels, cytoplasmic volume and c-Fos expression returned to control levels by 18 weeks after landing. These reversible effects were probably associated to osmotic stimuli resulting from modifications in the volume and distribution of extracellular fluids and plasma during flight and landing. However, oxytocin levels were still reduced at 18 weeks after landing in flight animals compared to controls. This indicates that space flight during prepuberal age may induce irreversible modifications in the regulation of oxytocinergic neurons, which in turn may result in permanent endocrine and behavioral impairments.

NASA Experiment Number 9301150↗

NASA NTRS1973

Skylab experiments. Volume 3: Materials science

The materials science and technology investigation conducted on the Skylab vehicle are discussed. The thirteen experiments that support these investigations have been planned to evaluate the effect of a weightless environment on melting and resolidification of a variety of metals and semiconductor crystals, and on combustion of solid flammable materials. A glossary of terms which define the space activities and a bibliography of related data are presented.

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NASA NTRS1976

Shuttle era waste management and biowaste monitoring

The acquisition of crew biomedical data has been an important task on manned space missions. The monitoring of biowastes from the crew to support water and mineral balance studies and endocrine studies has been a valuable part of this activity. This paper will present a review of waste management systems used in past programs. This past experience will be cited as to its influence on the Shuttle design. Finally, the Shuttle baseline waste management system and the proposed Shuttle biomedical measurement and sampling systems will be presented.

Sauer, R. L.↗

NASA NTRS1989

Control of intelligent robots in space

In view of space activities like International Space Station, Man-Tended-Free-Flyer (MTFF) and free flying platforms, the development of intelligent robotic systems is gaining increasing importance. The range of applications that have to be performed by robotic systems in space includes e.g., the execution of experiments in space laboratories, the service and maintenance of satellites and flying platforms, the support of automatic production processes or the assembly of large network structures. Some of these tasks will require the development of bi-armed or of multiple robotic systems including functional redundancy. For the development of robotic systems which are able to perform this variety of tasks a hierarchically structured modular concept of automation is required. This concept is characterized by high flexibility as well as by automatic specialization to the particular sequence of tasks that have to be performed. On the other hand it has to be designed such that the human operator can influence or guide the system on different levels of control supervision, and decision. This leads to requirements for the hardware and software concept which permit a range of application of the robotic systems from telemanipulation to autonomous operation. The realization of this goal requires strong efforts in the development of new methods, software and hardware concepts, and the integration into an automation concept.

Freund, E.↗

NASA NTRS1989

Proceedings of the NASA Conference on Space Telerobotics, volume 4

Papers presented at the NASA Conference on Space Telerobotics are compiled. The theme of the conference was man-machine collaboration in space. The conference provided a forum for researchers and engineers to exchange ideas on the research and development required for the application of telerobotic technology to the space systems planned for the 1990's and beyond. Volume 4 contains papers related to the following subject areas: manipulator control; telemanipulation; flight experiments (systems and simulators); sensor-based planning; robot kinematics, dynamics, and control; robot task planning and assembly; and research activities at the NASA Langley Research Center.

Rodriguez, Guillermo↗

NASA NTRS1993

C-SIDE: The control-structure interaction demonstration experiment

The Control-Structure Interaction Demonstration Experiment (C-SIDE) is sponsored by the Electro-Optics and Cryogenics Division of Ball Aerospace Systems Group. Our objective is to demonstrate methods of solution to structure control problems utilizing currently available hardware in a system that is an extension of our corporate experience. The larger space structures with which Ball has been associated are the SEASAT radar antenna, Shuttle Imaging Radar (SIR) -A, -B and -C antennas and the Radarsat spacecraft. The motivation for the C-SIDE configuration is to show that integration of active figure control in the radar's system-level design can relieve antenna mechanical design constraints. This presentation is primarily an introduction to the C-SIDE testbed. Its physical and functional layouts, and major components are described. The sensor is of special interest as it enables direct surface figure measurements from a remote location. The Remote Attitude Measurement System (RAMS) makes high-rate, unobtrusive measurements of many locations, several of which may be collocated easily with actuators. The control processor is a 386/25 executing a reduced order model-based algorithm with provision for residual mode filters to compensate for structure interaction. The actuators for the ground demonstration are non-contacting, linear force devices. Results presented illustrate some basic characteristics of control-structure interaction with this hardware. The testbed will be used for evaluation of current technologies and for research in several areas. A brief indication of the evolution of the C-SIDE is given at the conclusion.

Mohl, James B.↗

NASA NTRS1993

Construction and testing of a space ready rectenna

In Feb. 1993, the Solar Power Satellite (SPS) Working Group from ISAS, Japan will launch a sounding rocket into low earth orbit to perform two activities: collect scientific information on the high power microwave-ionosphere interaction, and demonstrate microwave power transmission in space at 2.45 GHz. The SPS Working Group announced an open invitation to international agencies willing to collaborate with the Microwave Energy Transmission in Space (METS) experiment in a number of categories. Under the sponsorship of the NASA's Lewis Research Center, the Center for Space Power located at Texas A&M University joined the experiment by producing a microwave rectifying receiving antenna (rectenna). The rectenna is a special type of receiving antenna with unique properties and characteristics. The rectenna's main purpose is to efficiently convert microwave power into DC power. The rectenna is an advanced component in microwave power beaming technology developed for 2.45 GHz. The state-of-the-art rectenna for this frequency consists of dipole antennas, filter circuits, and transmission lines etched on a thin layer of Kapton film. The format of the thin film rectenna is ideally suited for space applications. Thin film rectennas have a low specific mass of approximately 1 kg/kW. The main component of the rectenna is the rectifying diode. High conversion efficiencies (90 percent) in microwave to DC power are capable with special Schottky barrier diodes correctly located in the rectenna circuitry. The theory of operation of the 2.45 GHz rectenna is explained. Experimental test results on the METS rectenna are presented. The packaging of the rectenna is also discussed to meet space qualifications.

Brown, Alan M.↗

NASA NTRS1994

The Charlotte (TM) intra-vehicular robot

NASA has identified telerobotics and telescience as essential technologies to reduce the crew extra-vehicular activity (EVA) and intra-vehicular activity (IVA) workloads. Under this project, we are developing and flight testing a novel IVA robot to relieve the crew of tedious and routine tasks. Through ground telerobotic control of this robot, we will enable ground researchers to routinely interact with experiments in space. Our approach is to develop an IVA robot system incrementally by employing a series of flight tests with increasing complexity. This approach has the advantages of providing an early IVA capability that can assist the crew, demonstrate capabilities that ground researchers can be confident of in planning for future experiments, and allow incremental refinement of system capabilities and insertion of new technology. In parallel with this approach to flight testing, we seek to establish ground test beds, in which the requirements of payload experimenters can be further investigated. In 1993 we reviewed manifested SpaceHab experiments and defined IVA robot requirements to assist in their operation. We also examined previous IVA robot designs and assessed them against flight requirements. We rejected previous design concepts on the basis of threat to crew safety, operability, and maintainability. Based on this insight, we developed an entirely new concept for IVA robotics, the CHARLOTTE robot system. Ground based testing of a prototype version of the system has already proven its ability to perform most common tasks demanded of the crew, including operation of switches, buttons, knobs, dials, and performing video surveys of experiments and switch panels.

Swaim, Patrick L.↗

NASA NTRS2000

Fundamentals of Microgravity Vibration Isolation

In view of the utility of space vehicles as orbiting science laboratories, the need for vibration isolation systems for acceleration sensitive experiments has gained increasing visibility. This presentation provides a tutorial discussion of microgravity vibration isolation technology with the objective of elaborating on the relative merits of passive and active isolation approaches. The concepts of control bandwidth, isolation performance, and robustness will be addressed with illustrative examples. Concluding the presentation will be a suggested roadmap for future technology development activities to enhance the acceleration environment for microgravity science experiments.

Whorton, Mark S.↗

NASA NTRS2001

STS-105 Flight Day 2 Highlights

On this second day of the STS-105 mission, Discovery continues to approach the International Space Station (ISS) and the crewmembers of the orbiter (Commander Scott Horowitz, Pilot Frederick Sturckow, and Mission Specialists Daniel Barry and Patrick Forrester) are seen as they participate in various on-orbit activities, including the set-up and performance of the experiment 'Effects of Microgravity on Spinal Chord Excitability' and maneuver the Shuttle's robotic arm to its docking configuration. The Rocky Mountains are seen as Discovery passes over the United States.

Source record↗

NASA NTRS1996

Secondary particle contribution to LET spectra on LDEF

Four experiments utilizing passive detectors (P0006, P0004, A0015, M0004) were flown on LDEF to study the radiation environment. These experiments have been summarized in a companion paper (Benton et al., 1996). One of the experimental goals was to measure LET spectra at different locations and shielding depths with plastic nuclear track detectors (PNTD). It was found that the LET spectra extended well above the LET cutoff imposed by the geomagnetic field on GCR particle penetration into LEO. The high LET particles detected were mostly short-range (range < 2000 m), indicating that they were secondaries produced locally within the PNTD. The presence of these high LET particle fluences is important for the determination of dose equivalent because of the high Quality Factors (Q) involved. A relatively small fraction of particle fluence can contribute a large fraction of dose equivalent. Short-range, inelastic secondary particles produced by trapped protons in the South Atlantic Anomaly (SAA) were found to be a major contributor to the LET spectra above 100 keV/micrometer. The LET spectra were found to extend beyond the approximately 137 keV/micrometer relativistic GCR Fe peak to over 1000 keV/micrometer. The high LET tail of the LET spectra was measured in CR-39 and polycarbonate PNTDs using different techniques. GCR made a relatively modest contribution to the LET spectra as compared to the contributions from short-range secondary particles and stopping protons. LET spectra intercomparisons were made between LDEF measurements and exposures to 154 MeV accelerated proton beams. The similarities support the role of nuclear interactions by trapped protons as the major source of secondary particles in the PNTDs. Also techniques were employed to reduce the range cutoff for detection of the short-range secondaries to approximately 1 micrometer, so that essentially all secondary particles were included in the LET spectra. This has allowed a more realistic assessment of secondary contribution to dose equivalent. Comparisons of measured and calculated LET spectra have been made that demonstrate the need for more accurate modeling of secondary particles in radiation transport codes. Comparisons include preliminary calculations in which attempts have been made to include secondary particles.

long duration↗