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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.

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NASA NTRS1974

Remote platform power conserving system

A system is described where an unattended receiver and transmitter equipped data collection platform is interrogated by a substantially polar orbiting satellite. The method and apparatus involve physically representing the orbit of the satellite and the spin of the planetary body with timers, and using these representations to turn on the platform's receiver only when the satellite should be in radio range of the platform, whereby battery power at the platform is conserved.

Kurvin, C. W.↗

NASA NTRS1978

Pointed science scan platforms

Two examples of science scan platform mechanization concepts are presented to familiarize the reader with today's planetary scan platform technology. The first example is the Voyager scan platform, which will demonstrate the traditional approach to scan pointing from planetary vehicles. Although this conventional approach may be familiar to many, the control law implemented in the scan positioning loop is a new and interesting one. It is called 'Zero Crosser + Terminal Control'. The other example marks the beginning of a new generation of planetary scan pointing systems. It is the Galileo scan platform which will be inertially stabilized and decoupled from spacecraft motion.

Ward, R. S.↗

NASA NTRS1979

User definition and mission requirements for unmanned airborne platforms, revised

The airborne measurement requirements of the scientific and applications experiment user community were assessed with respect to the suitability of proposed strawman airborne platforms. These platforms provide a spectrum of measurement capabilities supporting associated mission tradeoffs such as payload weight, operating altitude, range, duration, flight profile control, deployment flexibility, quick response, and recoverability. The results of the survey are used to examine whether the development of platforms is warranted and to determine platform system requirements as well as research and technology needs.

Kuhner, M. B.↗

NASA NTRS1980

The dynamics and control of large flexible space structures, 3. Part A: Shape and orientation control of a platform in orbit using point actuators

The dynamics, attitude, and shape control of a large thin flexible square platform in orbit are studied. Attitude and shape control are assumed to result from actuators placed perpendicular to the main surface and one edge and their effect on the rigid body and elastic modes is modelled to first order. The equations of motion are linearized about three different nominal orientations: (1) the platform following the local vertical with its major surface perpendicular to the orbital plane; (2) the platform following the local horizontal with its major surface normal to the local vertical; and (3) the platform following the local vertical with its major surface perpendicular to the orbit normal. The stability of the uncontrolled system is investigated analytically. Once controllability is established for a set of actuator locations, control law development is based on decoupling, pole placement, and linear optimal control theory. Frequencies and elastic modal shape functions are obtained using a finite element computer algorithm, two different approximate analytical methods, and the results of the three methods compared.

Bainum, P. M.↗

NASA NTRS1979

Geostationary Platforms Mission and Payload Requirements Study. Volume 1: Executive summary

Time-phased missions and payloads for potential accommodation on geostationary platforms and the engineering requirements placed upon the platform housekeeping elements by selected payloads are identified. Optimum locations for geostationary platforms, potential missions and their characteristics, and potential user requirements were determined as well as the interface requirements between the missions and h the geostationary platform. A payload data book was prepared and antenna tradeoff studies were conducted. Payload missions are defined in terms of frequencies, power, beam patterns, interconnections, support requirements, and other characteristics.

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NASA NTRS1981

A multilevel control approach for a modular structured space platform

A three axis mathematical representation of a modular assembled space platform consisting of interconnected discrete masses, including a deployable truss module, was derived for digital computer simulation. The platform attitude control system as developed to provide multilevel control utilizing the Gauss-Seidel second level formulation along with an extended form of linear quadratic regulator techniques. The objectives of the multilevel control are to decouple the space platform's spatial axes and to accommodate the modification of the platform's configuration for each of the decoupled axes.

Chichester, F. D.↗

NASA NTRS1981

Design aspects of a solar array drive for spot, with a high platform stability objective

A solar array drive mechanism (MEGS) for the SPOT platform, which is a prototype of a multimission platform, is described. High-resolution cameras and other optical instruments are carried by the platform, requiring excellent platform stability in order to obtain high-quality pictures. Therefore, a severe requirement for the MEGS is the low level of disturbing torques it may generate considering the 0.6 times 10 to the minus 3 power deg/sec stability required. The mechanical design aspects aiming at reducing the mean friction torque, and therefore its fluctuations, are described as well as the method of compensation of the motor imperfections. It was concluded, however, that this is not sufficient to reach the stability requirement.

Cabillic, J.↗

NASA NTRS1982

Space platform accommodations

The results of studies performed at NASA of five space platform design reference missions (DRM) are presented. The DRM's were planned in an effort to eliminate problems, rather than to enhance optimization. A diagram of each payload is included, and the space platform concept is presented with the most important features being a continuous total power supply of 12.5 kW to the payloads at 30 and/or 120 Vdc regulated, a high-rate multiplexer with a total output of 48 Mbps, and and a thermal control system capable of dissipating the platform power output at payload fluid temperatures of 0 C to 3 C. Payload interface requirements were analyzed and appropriate integration hardware was added. Payload viewing characteristics are considered, and resource use is discussed. It is concluded that, in payload applications, efficient use of STS transportation and the platform must be considered.

Bailey, W.↗

NASA NTRS1983

Vibration characteristics of hexagonal radial rib and hoop platforms

Experiment and analysis have been used to characterize the modes of vibration of planar radial rib and hoop hexagonal platforms. Finite element analysis correlated very well with experimental results. The sensitivity of mode shapes and frequencies to cable stiffness and initial tension is presented. Threshold values have been identified, above which changes in cable stiffness do not affect the first few platform vibration modes. Primary vibration modes of the radial rib platform involve beam bending. Vibration modes of the hoop platform exhibit both beam bending and frame bending and torsion. Results indicate for low order polygonal structures, the radial rib concept produced a higher fundamental frequency. For high order polygonal structures, the hoop concept has the potential to achieve a higher fundamental frequency than the radial rib concept.

Belvin, W. K.↗

NASA NTRS1983

Space platform attitude control system

A discussion is presented of the preliminary design of the Space Platform System, which is being developed to support the Shuttle Orbiter in a sortie configuration with power, communications, and thermal and attitude control capability for up to 30 days while supporting payloads within the Shuttle bay or mounted directly on the platform. Three payload pallets can be supported for indefinite periods of time by the platform in a free flier mode. The vehicle is stabilized against gravity gradients and aerodynamic disturbance torques by the attitude control system. The attitude control system requirements are stringent, due to the need to counteract large aerodynamic disturbances despite the large platform size and low earth orbit altitude. The design of the control system allows it to control both free fly and sortie configurations, with differing inertias as payload pallets are changed.

Levinthal, J.↗

NASA NTRS1984

NASA's geostationary communications platform program

This paper reviews recent trends in communications satellites and explains NASA's current interest in geostationary communications platforms. Large communications platforms capable of supporting multiple payloads with common utilities have been examined in a number of studies since 1974 and appear to offer a number of potential advantages. In 1981, an Industry Briefing and Workshop sponsord by NASA focused on the institutional, operational and technical issues that will influence the implementation of geostationary platforms. The workshop identified numerous issues and problem areas that needed more detailed study. To address the issues/problems identified, a NASA geostationary communications platform program has been developed. This program is described, focusing on the initial studies to be performed.

Ramler, J.↗

NASA NTRS1985

Space platforms and autonomy

Potential applications for autonomous space platforms (SP) are discussed. The platforms are assumed to have long in-service lifetimes and therefore be flexible as to configuration modification and payload changeout. Higher degrees of autonomy, particularly from ground control, are made possible because of the rapid increase of microprocessor power and artificial intelligence advances. Functioning independently, the platforms are to rely only on periodic refurbishment visits by, e.g., the Orbiter. The Manned Space Station (MSS) will be the most complex structure, involving multifacted man-machine interfaces. The SP can be subsystems of the MSS (or other platforms), handling communications enunciation, data acquisition, analysis and telemetry, fault detection and isolation, systems monitoring and control, etc. The SP adopted will depend in all cases on costs vs benefits analyses to determine the worth of removing the function(s) from direct, regular human intervention.

Easter, R. W.↗

NASA NTRS1986

Tether pointing platform and space elevator mechanisms analysis of the key concepts for SATP and scaled SATP

The key concepts for a scaled and full model Science and Applications Tethered Platform (SATP) are analysized. This includes a tether pointing platform and a space elevator. The mechanism concepts and technological solutions are given. The idea of the tether pointing platform mechanism is to control and stabilize the attitude of a platform by means of a movable tether. The idea of the space elevator mechanism for a scaled SATP is to drag the tether gripping it between two rotating wheels.

Turci, E.↗

NASA NTRS1986

Tethered elevator and platforms as space station facilities: Systems studies and demonstrative experiments

Several key concepts of the science and applications tethered platforms were studied. Some conclusions reached are herein listed. Tether elevator and platform could improve the space station scientific and applicative capabilities. The space elevator presents unique characteristics as microgravity facility and as a tethered platform servicing vehicle. Pointing platforms could represent a new kind of observation facility for large class of payloads. The dynamical, control and technological complexity of these concepts advised demonstrative experiments. The on-going tethered satellite system offers the opportunity to perform such experiments. And feasibility studies are in progress.

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NASA NTRS1985

Space stations and space platforms - Concepts, design, infrastructure, and uses

Topics discussed include space infrastructures and early Space Station and platform planning. Consideration is given to the supportive role of the Space Station and platform in future astronomy, earth observation, planetary, and communication space missions. Papers are presented on the history of the Space Station and space platform concepts, potential designs of space stations and space platforms, and long-range plans for space research.

Bekey, I.↗

NASA NTRS1984

Inertially referenced instrument pointing platform with momentum compensated articulation

The characteristics of the Mariner Mark II Integrated Platform Pointing and Attitude Control System (IPPACS) microstep actuator with momentum compensation and the IPPACS optical reference tracker are examined, and the advantages of this new technology are identified. The momentum-compensated articulation acts to prevent platform articulation activity from disturbing the spacecaft. This guarantees dynamic stability, ensures a quiescent pointing environment, and decouples the design of the platform from the design of the spacecraft. A microstep actuator with harmonic drive provides platform angular step resolution to 0.5 arcsec for precision pointing of instruments. An optical reference tracker boresighted with scientific instruments guarantees accurate target-referenced closed-loop pointing. An IPPACS star and target tracker with 1 to 10 arcsec accuracy and wide 11 x 17 degrees field of view has been derived from Advanced Star and Target Reference Optical Sensor (ASTROS) CCD star tracker technology, greatly enhancing the optical referencing capabilities of future multimission interplanetary spacecraft.

Bell, C. E.↗

NASA NTRS1984

Earth observing system (Eos) requirements for a polar platform

This paper describes the requirements that the polar platform will have to meet if it is to satisfy the needs of the scientific earth observation communities in the early 1990s. The Eos is a prime mission for the polar platform. The polar platform will be a large satellite in a sun synchronous orbit that could be built up from the same components that are to be used to build the Space Station and its co-orbiting freeflying satellite. It will be serviced from the Shuttle so that it will be kept in operation and up-to-date for at least a decade. An initial set of scientific requirements has been documented by a Science and Missions Requirements Working Group (S&MRWG). These scientific requirements have been translated into derived technical requirements for the polar platform. These derived requirements are presented.

Muller, R. M.↗

NASA NTRS1986

Design summary of a geostationary facility utilized as a communications platform

This paper describes the technical aspects of a geostationary platform facility that makes maximum use of the planned NASA space station and its elements, mainly the orbital maneuvering vehicle (OMV) and the orbital transfer vehicles (OTV). The platform design concept is described, with emphasis on the key technologies utilized to configure the platform. Key systems aspects include a design summary with discussion of the controls, telemetry, command and ranging, power, propulsion, control electronics, thermal control subsystems, and space station interfaces. The use of the facility as a communications platform is developed to demonstrate the attractiveness of the concept. The economic benefits are discussed, as well as the concept of servicing for payload upgrade.

Barberis, N. J.↗