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At least 91 records · Page 5

Microgravity robotics technology program

A research program to develop technology for robots operating in the microgravity environment of the space station laboratory is described. These robots must be capable of manipulating payloads without causing them to experience harmful levels of acceleration, and the motion of these robots must not disturb adjacent experiments and operations by transmitting reactions that translate into damaging effects throughout the laboratory. Solutions to these problems, based on both mechanism technology and control strategies, are discussed. Methods are presented for reduction of robot base reactions through the use of redundant degrees of freedom, and the development of smoothly operating roller-driven robot joints for microgravity manipulators is discussed.

Rohn, Douglas A.↗

Durability tests of a five centimeter diameter ion thruster system

A modified Hughes SIT-5 system is being tested for durability at the Lewis Research Center. As of October 1, 1972, the thruster subsystem has logged over 8000 hours of operation. The initial 2023 hours were run with a translating screen thrust vector grid. The thruster is currently operating with an electrostatic type vector grid. Profiles and maps taken at widely separated intervals show that performance and operating characteristics have remained essentially constant. Overall efficiency is about 32 percent and power to thrust ratio is 170 watts per millipound at a specific impulse of 2500 seconds. Telescopic examination of the vector grid shows some sputtering erosion due to charge exchange and direct impingement ions.

Nakanishi, S.↗

Durability tests of a five-centimeter diameter ion thruster system.

A modified Hughes SIT-5 system is being tested for durability at the Lewis Research Center. As of Oct. 1, 1972, the thruster subsystem has logged over 8000 hours of operation. The initial 2023 hours were run with a translating screen thrust vector grid. The thruster is currently operating with an electrostatic type vector grid. Profiles and maps taken at widely separated intervals show that performance and operating characteristics have remained essentially constant. Overall efficiency is about 32 per cent and power to thrust ratio is 170 watts per millipound at a specific impulse of 2500 seconds. Telescopic examination of the vector grid shows some sputtering erosion due to charge exchange and direct impingement ions. An independent test of the propellant storage and cathode-isolator-vaporizer subsystem has demonstrated good reliability under simulated thruster operating conditions.

Nakanishi, S.↗

Gene activity during germination of spores of the fern, Onoclea sensibilis. Cell-free translation analysis of mRNA of spores and the effect of alpha-amanitin on spore germination

Poly(A)-RNA fractions of dormant, dark-imbibed (non-germinating) and photoinduced (germinating) spores of Onoclea sensibilis were poor templates in the rabbit reticulocyte lysate protein synthesizing system, but the translational efficiency of poly(A)+RNA was considerably higher than that of unfractionated RNA. Poly(A)+RNA isolated from photoinduced spores had a consistently higher translational efficiency than poly(A)+RNA from dark-imbibed spores. Analysis of the translation products by one-dimensional polyacrylamide gel electrophoresis showed no qualitative differences in the mRNA populations of dormant, dark-imbibed, and photoinduced spores. However, poly(A)+RNA from dark-imbibed spores appeared to encode in vitro fewer detectable polypeptides at a reduced intensity than photoinduced spores. A DNA clone encoding the large subunit of maize ribulose bisphosphate carboxylase hybridized at strong to moderate intensity to RNA isolated from dark-imbibed spores, indicating the absence of mRNA degradation. Although alpha-amanitin did not inhibit the germination of spores, the drug prevented the elongation of the rhizoid and protonemal initial with a concomitant effect on the synthesis of poly(A)+RNA. These results are consistent with the view that some form of translational control involving stored mRNA operates during dark-imbibition and photoinduced germination of spores.

NASA Discipline Number 29-20↗

High-efficiency 20 GHz traveling wave tube development for space communications

A 75 watt CW high efficiency helix TWT operating at 20 GHz was developed for satellite communication systems. The purpose was to extend the performance capabilities of helix TWTs by using recent technology developments. The TWT described is a unique design because high overall efficiency is obtained with a low perveance beam. In the past, low perveance designs resulted in low beam efficiencies. However, due to recent breakthoughs in diamond rod technology and in collector electrode materials, high efficiencies can now be achieved with low perveance beams. The advantage of a low perveance beam is a reduction in space charge within the beam which translates to more efficient collector operation. In addition, this design incorporates textured graphite electrodes which further enhance collector operation by suppressing backstreaming secondaries. The diamond supported helix circuit features low RF losses, high interaction impedance, good thermal handling capability and has been designed to compensate for the low perveance beam. One more discussed tube feature is the use of a velocity taper in the output helix that achieves low signal distortion while maintaining high efficiency.

Aldana, S. L.↗

A MEMS Micro-Translation Stage with Long Linear Translation

A MEMS Micro-Translation Stage (MTS) actuator concept has been developed that is capable of traveling long distances, while maintaining low power, low voltage, and accuracy as required by many applications, including optical coupling. The Micro-Translation Stage (MTS) uses capacitive electrostatic forces in a linear motor application, with stationary stators arranged linearly on both sides of a channel, and matching rotors on a moveable shuttle. This creates a force that allows the shuttle to be pulled along the channel. It is designed to carry 100 micron-sized elements on the top surface, and can travel back and forth in the channel, either in a stepping fashion allowing many interim stops, or it can maintain constant adjustable speeds for a controlled scanning motion. The MTS travel range is limited only by the size of the fabrication wafer. Analytical modeling and simulations were performed based on the fabrication process, to assure the stresses, friction and electrostatic forces were acceptable to allow successful operation of this device. The translation forces were analyzed to be near 0.5 micron N, with a 300 micron N stop-to-stop time of 11.8 ms.

Ferguson, Cynthia K.↗

Towards a Formal Semantics of Flight Plans and Trajectories

In the National Airspace System, ight plans are often used only as a planning tool by air trac controllers and aircraft operators. These plans are implicitly translated into trajectories by the pilot or by the ight management system, and subsequently own by the aircraft. This translation process inevitably introduces di erences between the plan and the trajectory. However, given the current intended usage, exact correspondence between the plan and the trajectory is not needed. To achieve greater capacity and eciency, future air trac management concepts are being designed around the use of trajectories where predictability is extremely important. In this paper, a mathematical relationship between ight plans and trajectories is explored with the goal of making feasible, highly accurate predictions of future positions and velocities of aircraft. The goal here is to describe, in mathematically precise detail, a formal language of trajectories, whereby all receivers of the trajectory information will be able to arrive at precisely the same trajectory predication and to do this without having aircraft broadcast a large amount of data. Although even a four-dimensional ight plan is simple in structure, this paper will show that it is inherently ambiguous and will explore these issues in detail. In e ect, we propose that a rigorous semantics for ight plans can be developed and this will serve as an important stepping stone towards trajectory-based operations in the National Airspace System.

Hagen, George E.↗

Translation Optics for 30 cm Ion Engine Thrust Vector Control

Data were obtained from a 30 cm xenon ion thruster in which the accelerator grid was translated in the radial plane. The thruster was operated at three different throttle power levels, and the accelerator grid was incrementally translated in the X, Y, and azimuthal directions. Plume data was obtained downstream from the thruster using a Faraday probe mounted to a positioning system. Successive probe sweeps revealed variations in the plume direction. Thruster perveance, electron backstreaming limit, accelerator current, and plume deflection angle were taken at each power level, and for each accelerator grid position. Results showed that the thruster plume could easily be deflected up to six degrees without a prohibitive increase in accelerator impingement current. Results were similar in both X and Y direction.

Haag, Thomas↗

Transfer of terrestrial technology for lunar mining

The functions, operational procedures, and major items of equipment that comprise the terrestrial mining process are characterized. These data are used to synthesize a similar activity on the lunar surface. Functions, operations, and types of equipment that can be suitably transferred to lunar operation are identified. Shortfalls, enhancements, and technology development needs are described. The lunar mining process and what is required to adapt terrestrial equipment are highlighted. It is concluded that translation of terrestrial mining equipment and operational processes to perform similar functions on the lunar surface is practical. Adequate attention must be given to the harsh environment and logistical constraints of the lunar setting. By using earth-based equipment as a forcing function, near- and long-term benefits are derived (i.e., improved terrestrial mining in the near term vis-a-vis commercial production of helium-3 in the long term.

Hall, Robert A.↗

Pattern recognition technique

Technique operates regardless of pattern rotation, translation or magnification and successfully detects out-of-register patterns. It improves accuracy and reduces cost of various optical character recognition devices and page readers and provides data input to computer.

Hong, J. P.↗

Sensorimotor Adaptation Following Exposure to Ambiguous Inertial Motion Cues

The central nervous system must resolve the ambiguity of inertial motion sensory cues in order to derive accurate spatial orientation awareness. Adaptive changes in how inertial cues from the otolith system are integrated with other sensory information lead to perceptual and postural disturbances upon return to Earth s gravity. The primary goals of this ground-based research investigation are to explore physiological mechanisms and operational implications of tilt-translation disturbances during and following re-entry, and to evaluate a tactile prosthesis as a countermeasure for improving control of whole-body orientation during tilt and translation motion.

Wood, S. J.↗

BIRCHES and Lunarcubes: Building the First Deep Space Cubesat Broadband IR Spectrometer

The Broadband InfraRed Compact High-resolution Exploration Spectrometer (BIRCHES), which will be described in detail here, is the compact broadband IR spectrometer of the Lunar Ice Cube mission. Lunar Ice Cube is one of 13 6U cubesats that will be deployed by EM1 in cislunar space, qualifying as lunarcubes. The LunarCube paradigm is a proposed approach for extending the affordable CubeSat standard to support access to deep space via cis-lunar/lunar missions. Because the lunar environment contains analogs of most solar system environments, the Moon is an ideal target for both testing critical deep space capabilities and understanding solar system formation and processes. Effectively, as developments are occurring in parallel, 13 prototype deep space cubesats are being flown for EM1. One useful outcome of this ‘experiment’ will be to determine to what extent it is possible to develop a lunarcube ‘bus’ with standardized interfaces to all subsystems using reasonable protocols for a variety of payloads. The lunar ice cube mission was developed as the test case in a GSFC R&D study to determine whether the cubesat paradigm could be applied to deep space, science requirements driven missions, and BIRCHES was its payload. Here, we present the design and describe the ongoing development, and testing, in the context of the challenges of using the cubesat paradigm to fly a broadband IR spectrometer in a 6U platform, including minimal funding and extensive need for leveraging existing assets and relationships on development, the foreshortened schedule for payload delivery on testing, and minimum bandwidth translating into simplified or canned operation.

Chapin, Peter↗

A new approach to telemetry data processing

An approach for a preprocessing system for telemetry data processing was developed. The philosophy of the approach is the development of a preprocessing system to interface with the main processor and relieve it of the burden of stripping information from a telemetry data stream. To accomplish this task, a telemetry preprocessing language was developed. Also, a hardware device for implementing the operation of this language was designed using a cellular logic module concept. In the development of the hardware device and the cellular logic module, a distributed form of control was implemented. This is accomplished by a technique of one-to-one intermodule communications and a set of privileged communication operations. By transferring this control state from module to module, the control function is dispersed through the system. A compiler for translating the preprocessing language statements into an operations table for the hardware device was also developed. Finally, to complete the system design and verify it, a simulator for the collular logic module was written using the APL/360 system.

Broglio, C. J.↗

Motion Perception and Manual Control Performance During Passive Tilt and Translation Following Space Flight

This joint ESA-NASA study is examining changes in motion perception following Space Shuttle flights and the operational implications of post-flight tilt-translation ambiguity for manual control performance. Vibrotactile feedback of tilt orientation is also being evaluated as a countermeasure to improve performance during a closed-loop nulling task. METHODS. Data has been collected on 5 astronaut subjects during 3 preflight sessions and during the first 8 days after Shuttle landings. Variable radius centrifugation (216 deg/s) combined with body translation (12-22 cm, peak-to-peak) is utilized to elicit roll-tilt perception (equivalent to 20 deg, peak-to-peak). A forward-backward moving sled (24-390 cm, peak-to-peak) with or without chair tilting in pitch is utilized to elicit pitch tilt perception (equivalent to 20 deg, peak-to-peak). These combinations are elicited at 0.15, 0.3, and 0.6 Hz for evaluating the effect of motion frequency on tilt-translation ambiguity. In both devices, a closed-loop nulling task is also performed during pseudorandom motion with and without vibrotactile feedback of tilt. All tests are performed in complete darkness. PRELIMINARY RESULTS. Data collection is currently ongoing. Results to date suggest there is a trend for translation motion perception to be increased at the low and medium frequencies on landing day compared to pre-flight. Manual control performance is improved with vibrotactile feedback. DISCUSSION. The results of this study indicate that post-flight recovery of motion perception and manual control performance is complete within 8 days following short-duration space missions. Vibrotactile feedback of tilt improves manual control performance both before and after flight.

Clement, Gilles↗

Benefits of a Single-Person Spacecraft for Weightless Operations

Historically, less than 20 percent of crew time related to extravehicular activity (EVA) is spent on productive external work. For planetary operations space suits are still the logical choice; however for safe and rapid access to the weightless environment, spacecraft offer compelling advantages. FlexCraft, a concept for a single-person spacecraft, enables any-time access to space for short or long excursions by different astronauts. For the International Space Station (ISS), going outside is time-consuming, requiring pre-breathing, donning a fitted space suit, and pumping down an airlock. For each ISS EVA this is between 12.5 and 16 hours. FlexCraft provides immediate access to space because it operates with the same cabin atmosphere as its host. Furthermore, compared to the space suit pure oxygen environment, a mixed gas atmosphere lowers the fire risk and allows use of conventional materials and systems. For getting to the worksite, integral propulsion replaces hand-over-hand translation or having another crew member operate the robotic arm. This means less physical exertion and more time at the work site. Possibly more important, in case of an emergency, FlexCraft can return from the most distant point on ISS in less than a minute. The one-size-fits-all FlexCraft means no on-orbit inventory of parts or crew time required to fit all astronauts. With a shirtsleeve cockpit, conventional displays and controls are used, there is no suit trauma and because the work is not strenuous, no rest days are required. Furthermore, there is no need to collect hand tools because manipulators are equipped with force multiplying end-effectors that can deliver the precise torque for the job. FlexCraft is an efficient solution for asteroid exploration allowing all crew to use one vehicle with no risk of contamination. And, because FlexCraft is a vehicle, its design offers better radiation and micro-meteoroid protection than space suits.

Griffin, Brand Norman↗

Operational compensation for effect of close Titan flyby on remainder of Voyager 1 Saturn near encounter

The satellite instrument pointing update process (SPUP) developed for the Voyager 1 Saturn encounter is assessed. At certain times, navigation errors translated into target pointing errors, impede camera operation. Two sigma pointing accuracy of 1.5 to 2.0 mrads per axis was required. The SPUP combines correction slews implemented by immediate action commands with preevent modifications. The process worked perfectly, producing good quality images of target areas.

Laeser, R. P.↗

SSBRP User Operations Facility (UOF) Overview and Development Strategy

This paper will present the Space Station Biological Research Project (SSBRP) User Operations Facility (UOF) architecture and development strategy. A major element of the UOF at NASA Ames Research Center, the Communication and Data System (CDS) will be the primary focus of the discussions. CDS operational, telescience, security, and development objectives will be discussed along with CDS implementation strategy. The implementation strategy discussions will include: Object Oriented Analysis & Design, System & Software Prototyping, and Technology Utilization. A CDS design overview that includes: CDS Context Diagram, CDS Architecture, Object Models, Use Cases, and User Interfaces will also be presented. CDS development brings together "cutting edge" technologies and techniques such as: object oriented development, network security, multimedia networking, web-based data distribution, JAVA, and graphical user interfaces. Use of these "cutting edge" technologies and techniques translates directly to lower development and operations costs.

Picinich, Lou↗

A Fortran-90 Based Multiprecision System

The author has developed a new version of his Fortran multiprecision computation system that is based on the Fortran-90 language. With this new approach, a translator program is not required - translation of Fortran code for multiprecision is accomplished by merely utilizing advanced features of Fortran-90, such as derived data types and operator extensions. This approach results in more reliable translation and also permits programmers of multiprecision applications to utilize the full power of the Fortran-90 language. Three multiprecision datatypes are supported in this system: multiprecision integer. real and complex. All the usual Fortran conventions for mixed mode operations are supported, and many of the Fortran intrinsics, such as SIN, EXP and MOD, are supported with multiprecision arguments. This paper also briefly describes an interesting application of this software, wherein new number-theoretic identities have been discovered by means of multiprecision computations.

Bailey, David H.↗