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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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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

A preliminary analysis of a radar-mapping mission to Venus

A rather broad survey is reported of the Venus radar orbiter possibilities within the period 1983-1990. Minimum mission imaging requirements have been set by comparison with the improving capabilities of earth based radar systems and an examination of earth airborne radar imaging. This has led to a requirement for 80 percent coverage at a resolution of 100 m. A first main conclusion is that only the Shuttle-Centaur launch system would be capable of establishing a circular orbit under all possible launch conditions. Thus, orbit eccentricity has been introduced as a parameter throughout this presentation. An examination of typical radar designs has led to upper and lower limits on swath width of 100 and 50 km. A lower eccentricity of 0.2 was set by considering the current Viking propulsion system. An examination of solar perturbations indicates that orbit maintenance problems increase rapidly above an eccentricity of 0.5.

Mackay, J. S.↗
NASA NTRS1974

The role of man in conducting earth resources observations from space

The experience gained from the Skylab Earth Resources Experiment Package indicates that future equipment should be designed to facilitate on-orbit maintenance. Man should also be used to achieve selective data gathering, thus reducing the total requirements for data handling and analysis. This should require onboard displays of selected sensor signals for real-time analysis.

Weitz, P. J.↗
NASA NTRS1974

General concept considerations and mission profile

A general overview of the LST Program and the basic elements of the system are described. The LST schedule is discussed. The importance of properly balancing the performance of LST elements and understanding their cost/performance relationships is emphasized. Particular attention is given to the LST/Shuttle interface and on-orbit maintenance modes.

Downey, J. A., III↗
NASA NTRS1975

Orbital lifetime capabilities of digital programs RMDAP and Monster

The orbital lifetime study capabilities of the Reference Mission Design and Analysis Program (RMDAP) and the Apollo Mission Planning and Real-Time Rendezvous Support Program (ARRS or Monster) were studied. Output and program versatility, that is, the methods with which each program permits user definition of the major factors affecting orbital lifetimes, are discussed. In addition, orbit maintenance is examined and sample runs are compared. Since each program has special capabilities in different areas, it is left to the investigator's discretion as to the preferable program to employ for his lifetime study purposes.

Source record↗
NASA NTRS1978

Solar array systems

The recent past, present state-of-the-art, and future needs in the area of large photovoltaic solar arrays are discussed. In the past most attention was focused upon performance whereas in the future most of the effort should go into cost reduction. Suggestions are made regarding possible approaches to reducing cost such as on-orbit maintenance, extended lifetime, solar concentrators, and high-voltage modular concepts.

Crabtree, W. L.↗
NASA NTRS1979

Study of multi-kW solar arrays for Earth orbit applications: Midterm performance review

Planar and concentrator solar array concepts capable of providing 300 kW to 1000 kW in low Earth orbit applications in the 1987 time period at an array recurring cost less than or equal to thirty dollars per watt are examined. Silicon and gallium arsenide solar cell applicability are evaluated. On-orbit maintenance by space shuttle is also investigated. Design configurations for the solar arrays and solar cells are recommended.

Source record↗
NASA NTRS1981

An integrated transportation and operations comparison of space and ground based OTV's

This paper presents the results of a comparison of space vs. ground basing of orbital transfer vehicles (OTV). The comparison was done assuming an 11-year mission model beginning in 1995 and averaging over 100 MT of payloads per year to GEO. When analyzed from a total transportation standpoint, the launch system employed had the greatest impact on the basing mode comparison. A launch fleet consisting of both a basic STS and a Shuttle derivative cargo vehicle provided the least cost. Only a small advantage (3%) was found in flight performance for the space based (SB) OTV once it incorporated the necessary provisions for space debris protection and on-orbit maintenance. Propellant storage and transfer losses associated with the SB OTV amounted to 12% of the actual flight propellant requirement. Turnaround of the SB OTV required a crew of 3 and 40% duty cycle. The life cycle cost comparison including all involved space elements indicated less than a 10% difference between basing modes. The SB OTV however is judged to provide more flexibility in launch manifesting, simplified recovery operations and greater potential for improvement.

Davis, E. E.↗
NASA NTRS1981

Space Shuttle utilization characteristics with special emphasis on payload design, economy of operation and effective space exploitation

The reusable manned Space Shuttle has made new and innovative payload planning a reality and opened the door to a variety of payload concepts formerly unavailable in routine space operations. In order to define the payload characteristics and program strategies, current Shuttle-oriented programs are presented: NASA's Space Telescope, the Long Duration Exposure Facility, the West German Shuttle Pallet Satellite, and the Goddard Space Flight Center's Multimission Modular Spacecraft. Commonality of spacecraft design and adaptation for specific mission roles minimizes payload program development and STS integration costs. Commonality of airborne support equipment assures the possibility of multiple program space operations with the Shuttle. On-orbit maintenance and repair was suggested for the module and system levels. Program savings from 13 to over 50% were found obtainable by the Shuttle over expendable launch systems, and savings from 17 to 45% were achievable by introducing reuse into the Shuttle-oriented programs.

Turner, D. N.↗
NASA NTRS1982

Future orbital transfer vehicle technology study. Volume 2: Technical report

Missions for future orbit transfer vehicles (1995-2010) are identified and the technology, operations and vehicle concepts that satisfy the transportation requirements are defined. Comparison of reusable space and ground based LO2/LH2 OTV's was made. Both vehicles used advanced space engines and aero assist capability. The SB OTV provided advantages in life cycle cost, performance and potential for improvement. Comparison of an all LO2/LH2 OTV fleet with a fleet of LO2/LH2 OTVs and electric OTV's was also made. The normal growth technology electric OTV used silicon cells with heavy shielding and argon ion thrusters. This provided a 23% advantage in total transportation cost. The impact of accelerated technology was considered in terms of improvements in performance and cost effectiveness. The accelerated technology electric vehicle used GaAs cells and annealing but did not result in the mixed fleet being any cheaper than an all LO2/LH2 OTV fleet. It is concluded that reusable LO2/LH2 OTV's can serve all general purpose cargo roles between LEO and GEO for the forseeable future. The most significant technology for the second generation vehicle would be space debris protection, on-orbit propellant storage and transfer and on-orbit maintenance capability.

Davis, E. E.↗
NASA NTRS1982

Future orbital transfer vehicle technology study. Volume 1: Executive summary

Reusable space and ground based LO2/LH2 OTV's, both advanced space engines and aero assist capability were compared. The SB OTV provided advantages in life cycle cost, performance and potential for improvement. An all LO2/LH2 OTV fleet was also compared with a fleet of LO2/.H2 OTV's and electric OTV's. The normal growth technology electric OTV used silicon cells with heavy shielding and argon ion thrusters. In this case, the LO2/LH2 OTV fleet provided a 23% advantage in total transportation cost. An accelerated technology LF2/LH2 OTV provided improvements in performance relative to LO2/.H2 OTV but has higher DDT&E cost which negated its cost effectiveness. The accelerated technology electric vehicle used GaAs cells and annealing but still did not result in the mixed fleet being any cheaper than an all LO2/LH2 OTV fleet. It is concluded that reusable LO2/LH2 OTV's can serve all general purpose cargo roles between LEO and GEO for the forseeable future. The most significant technology for the second generation vehicle would be space debris protection, on orbit propellant storage and transfer and on orbit maintenance capability.

Davis, E. E.↗
NASA NTRS1982

Space telescope neutral buoyancy simulations: The first two years

Neutral Buoyancy simulations which were conducted to validate the crew systems interface as it relates to space telescope on-orbit maintenance and contingency operations is discussed. The initial concept validation tests using low fidelity mockups is described. The entire spectrum of proposed space telescope refurbishment and selected contingencies using upgraded mockups which reflect flight hardware are reported. Findings which may be applicable to future efforts of a similar nature are presented.

Sanders, F. G.↗
NASA NTRS1982

Simulation and testing of digital control on a flexible beam

Large space structures are expected to have control problems due to low stiffness and damping, and control laws for these structures must deal with shape and configuration control as well as attitude and orbit maintenance. In general, these control tasks must be accomplished without adversely interacting with the lightly damped and low frequency vibration modes of the structure. Modal control schemes have been proposed to deal with these problems. A discrete time parameter adaptive control scheme which uses modal control has been proposed by Montgomery and Johnson (1978). In the present investigation the method considered by Montgomery and Johnson is applied to a homogeneous free-free beam in both numerical simulation and laboratory experimentation. Mathematical modeling of the beam is treated in a manner expedient for digital simulation and control implementation.

Williams, J. P.↗
NASA NTRS1983

Structures and mechanisms - Streamlining for fuel economy

The design of prospective NASA space station components which inherently possess the means for structural growth without compromising initial system characteristics is considered. In structural design terms, space station growth can be achieved by increasing design safety factors, introducing dynamic isolators to prevent loads from reaching the initial components, or preplanning the refurbishment of the original structure with stronger elements. Design tradeoffs will be based on the definition of on-orbit loads, including docking and maneuvering, whose derived load spectra will allow the estimation of fatigue life. Improvements must be made in structural materials selection in order to reduce contamination, slow degradation, and extend the life of coatings. To minimize on-orbit maintenance, long service life lubrication systems with advanced sealing devices must be developed.

Card, M. F.↗
NASA NTRS1983

Autonomy issues for an operational space station

Within the last decade, both the U.S. and the Soviet space programs have taken significant preliminary steps in developing technology and systems which are appropriate for the establishment of space stations. The degree of autonomy which will be provided for the station and the role of the crew represents one of the most critical considerations. The present investigation is concerned with a review of the major autonomy issues associated with a permanent, low earth orbit, operational space station. It is shown that both operational effectiveness and crew safety issues require a relatively high degree of space station autonomy. The autonomy level should, for instance, be higher than that of the present space shuttle. Attention is given to various levels of spacecraft autonomy, system integrity, attitude determination and control, navigation and orbit maintenance, system maintenance and resupply, mission support, and implementation of autonomy.

Daly, K. C.↗
NASA NTRS1985

Transportation Applications, Part 1

The applications of tethers in support of space transportation is divided into: (1) orbit transfer, momentum transfer release/rendezvous (hanging, swinging, and spinning) and simplified docking; (2) orbit maintenance: electrodynamic thrust in or out of plane, electrodynamic libration pumping or damping, momentum scavenging, and isolate thruster exhaust; and (3) transfer within constellation: deployment or retrieval of whole constellation, clothesline loop, hoist, tram for travel on the tether, monkey between the tethers, and power and fluid transfer.

Carroll, J.↗
NASA NTRS1986

Electrical power system for the U.S. space station

The Space Station Electrical Power System presents many interesting challenges. It will be much larger than previous space power systems, and it must be designed for on-orbit maintenance and replacement, along with having a growth capability. The power generation, energy storage, and power management and distribution (PMAD) subsystems comprise the primary elements of the overall system. Each was analyzed by NASA Lewis Research Center and its two contractors -- Rocketdyne and TRW -- in the definition studies of the program to determine the optimum approach to minimize initial costs and life cycle costs. For the PMAD subsystem, a ring bus architecture operating at 440 V, 20 kHz, single phase, was selected. Photovoltaic and solar dynamic power generation subsystems were both studied. Major tradeoffs were made for each subsystem and for the overall system, and a hybrid system (both photovoltaic and solar dynamic) was selected.

Nored, D. L.↗
NASA NTRS1984

Space Station - The next logical step

NASA is committed to the development of a permanently manned Space Station within a decade, in concert with European and Japanese space agencies. In addition to continuing scientific research, the Space Station will proceed with applied science and industrialization experiments. International cooperation opportunities arise within the Space Station program for users (in the definition of missions), for builders (in the development of station resources and capabilities), and operators (in the orbital maintenance of the Space Station).

Finn, T. T.↗
NASA NTRS1985

Payload isolation and precision pointing for the 1990's

The design of a pointing system that is applicable for a variety of payloads is examined. The system employs a very soft interface coupled with inertial control torques which use reaction wheels or control moment gyros. The fundamental stability and disturbance rejection characteristics of simple gimbal pointing systems and the soft mounted inertially reacting concept are evaluated and compared. It is observed that in simple and two-stage gimbal systems there is dynamic interaction with the basebody and these types of systems are not applicable for a Space Station/Space Platform environment in which system dynamics are uncertain; however, the soft mounted inertially reacting concept minimizes the dynamic interaction with the basebody and retains stability. It is concluded that the soft mounted inertially reacting concept has the pointing accuracy and disturbance isolation of a free flying spacecraft while still obtaining power, communication, orbit maintenance, and servicing from a basebody.

Sirlin, S. W.↗