Proceedings of a Workshop on Applications of Tethers in Space, Volume 2

The panel conclusions for each of the following panels (science applications; electrodynamic interactions; transportation applications; artificial gravity; constellations; and technology and test) are given

Proceedings of a Workshop on the Applications of Tethers in Space, Volume 1

Project overview; tether deployment; satellite system description; tether fundamentals; science applications; electrodynamic interactions; transportation; artificial gravity; and constellations; were described

Space Station Systems: a Bibliography with Indexes (Supplement 8)

This bibliography lists 950 reports, articles, and other documents introduced into the NASA scientific and technical information system between July 1, 1989 and December 31, 1989. Its purpose is to provide helpful information to researchers, designers and managers engaged in Space Station technology development and mission design. Coverage includes documents that define major systems and subsystems related to structures and dynamic control, electronics and power supplies, propulsion, and payload integration. In addition, orbital construction methods, servicing and support requirements, procedures and operations, and missions for the current and future Space Station are included

Technology for large space systems: A bibliography with indexes (supplement 20)

This bibliography lists 694 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System between July, 1988 and December, 1988. Its purpose is to provide helpful information to the researcher or manager engaged in the development of technologies related to large space systems. Subject areas include mission and program definition, design techniques, structural and thermal analysis, structural dynamics and control systems, electronics, advanced materials, assembly concepts, and propulsion

Tethers in space handbook

The handbook provides a list and description of ongoing tether programs. This includes the joint U.S.-Italy demonstration project, and individual U.S. and Italian studies and demonstration programs. An overview of the current activity level and areas of emphasis in this emerging field is provided. The fundamental physical principles behind the proposed tether applications are addressed. Four basic concepts of gravity gradient, rotation, momentum exchange, and electrodynamics are discussed. Information extracted from literature, which supplements and enhances the tether applications is also presented. A bibliography is appended

Applications of Tethers in Space, Volume 1

The tethered satellite system is described including tether fundamentals. Applications of very long tethers in space to a broad spectrum of future space missions are explored. Topics covered include: science, transportation, constellations, artificial gravity, technology and test, and electrodynamic interactions. Recommendations to NASA are included

Developing an Integrated Guidance and Control System for Reactive Free-Flyer Maneuvering

The use of highly autonomous free-flying spacecraft has been investigated for potential utility in future human spaceflight endeavors. In general, ’free-flyer’ robots are small, self-sufficient spacecraft that operate near the exterior of larger space structures, such as the International Space Station, and are designed to provide support during various operations. Free-flyer designs and concepts often include a large degree of autonomy to provide mission support with little operational overhead. One of the building blocks of autonomous free-flyer behavior is safe and reliable point-to-point maneuvering during proximity operations. This thesis explores the development and simulation of an integrated guidance and control (G&C) system to enable safe free-flyer point-to-point maneuvering in proximity to larger space structures, including the avoidance of collision and jet plume impingement. The foundation for this system is an existing trajectory planning method introduced by Roger [1]. This method represents the free-space as a discrete harmonic potential field and uses the resulting field gradient as a condition for generating collision-free trajectories that efficiently account for natural dynamics. A real-time guidance process is built around this method that can manage an internal model of the environment based upon obstacle mapping data and react quickly to dynamic obstacles. A linear-programming jet selection technique is implemented to fulfill six DOF velocity impulse commands using a free-flyer’s RCS propulsion system, and additionally is augmented to include jet plume impingement avoidance functionality. Finally, an attitude con-troller process was developed and implemented to enable the free-flyer to reach and track a desired attitude during translational maneuvers. To verify the system’s capabilities, a test-bed simulation was developed using the SpaceCRAFT platform, specifically utilizing it’s modular, asynchronous architecture. In a set of four maneuver-ing tests set in distinct obstacle environments, the G&C system demonstrated the ability to maneuver the free-flyer to the goal state along collision-free trajectories. In three of the test cases, the plume avoidance strategy results in a large reduction in the accumulated plume cost (36-54%). Overall, these simulation results demonstrate that the system enabled point-to-point maneuvering for a reference free-flyer design, and support its feasibility and practicality. This work represents a somewhat unique approach to free-flyer autonomous maneuvering in that it departs from a trajectory planning, or offline-online paradigm. Instead, this approach relies on the refinement of an internal model of the environment and the resulting potential field to per-form reactive path-finding. This approach results in better overall flexibility when the free-flyer lacks knowledge of the position, geometry, and motion of nearby obstacles. In the future, the integration of Simultaneous Localization and Mapping (SLAM) and 3D mapping algorithms will help to further verify the feasibility of this approach. Other future improvements include integrating more robust methods of dynamic obstacle avoidance and automated positioning and scaling of the potential field grid

Project Argo: The design and analysis of an all-propulsive and an aeroassisted version of a manned space transportation vehicle

Project Argo is the design of a manned Space Transportation Vehicle (STV) that would transport payloads between LEO (altitude lying between 278 to 500 km above the Earth) and GEO (altitude is approximately 35,800 km above the Earth) and would be refueled and refurbished at the Space Station Freedom. Argo would be man's first space-based manned vehicle and would provide a crucial link to geosynchronous orbit where the vast majority of satellites are located. The vehicle could be built and launched shortly after the space station and give invaluable space experience while serving as a workhorse to deliver and repair satellites. Eventually, if a manned space station is established in GEO, then Argo could serve as the transport between the Space Station Freedom and a Geostation. If necessary, modifications could be made to allow the vehicle to reach the moon or possibly Mars. Project Argo is unique in that it consists of the design and comparison of two different concepts to accomplish the same mission. The first is an all-propulsive vehicle which uses chemical propulsion for all of its major maneuvers between LEO and GEO. The second is a vehicle that uses aeroassisted braking during its return from GEO to LEO by passing through the upper portions of the atmosphere

Proceedings of a Workshop on Applications of Tethers in Space, Executive Summary

The objectives were to identify potential applications for tethers in space; develop a first order assessment of the feasibility and benefits of tether applications; recommend future actions necessary to enable tether applications, including required technology advancements; and stimulate industry and government planners to consider the unique properties of tethers in designs for future missions

Applications of Tethers in Space, Volume 2

Topics discussed include tethered satellites, tether deployment, satellite systems, science applications, electrodynamic interactions, transportation applications, artificial gravity, constellations, and technology and testing