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NASA NTRS1990

Space Station Freedom on-orbit crew time availability - A limited resource

Because of the enormity, complexity, and duration of the Space Station Freedom (SSF) project, the available crew time is at a premium. This paper discusses the methodology for determining, early in the program, estimates of crew time which will be available within pressurized areas of intravehicular activity, from the First Element Launch (FEL) throughout the lifetime of the SSF. The methodology utilizes the baseline assembly sequence (November 1989) as a guideline. The total hours provided are categorized by periods, where a period is comprised of the time between two major SSF Program assembly milestones; e.g., FEL to Man Tended Capability (MTS), MTS to Permanently Manned Capability (PMC), or PMC to Assembly Complete (AC). After AC, total available crew time is presented on a yearly basis.

Garegnani, Jerry J.↗

NASA NTRS1990

Space Station Freedom Data Assessment Study

The SSF Data Assessment Study was initiated to identify payload and operations data requirements to be supported in the Space Station era. To initiate the study payload requirements from the projected SSF user community were obtained utilizing an electronic questionnaire. The results of the questionnaire were incorporated in a personal computer compatible database used for mission scheduling and end-to-end communications analyses. This paper discusses data flow paths and associated latencies, communications bottlenecks, resource needs versus availability, payload scheduling 'warning flags' and payload data loading requirements for each major milestone in the Space Station buildup sequence. This paper also presents the statistical and analytical assessments produced using the data base, an experiment scheduling program, and a Space Station unique end-to-end simulation model. The modeling concepts and simulation methodologies presented in this paper provide a foundation for forecasting communication requirements and identifying modeling tools to be used in the SSF Tactical Operations Planning (TOP) process.

Johnson, Anngienetta R.↗

NASA NTRS1990

Space Station accommodation of the Space Exploration Initiative

It is pointed out that Space Station Freedom (SSF) will support the transportation, research, and development requirements of the Space Exploration Initiative through augmentation of its resources and initial capabilities. These augmentations include providing facilities for lunar and Mars vehicle testing, processing, and servicing; providing laboratories and equipment for such enabling research as microgravity countermeasures development; and providing for the additional crew that will be required to carry out these duties. It is noted that the best way to facilitate these augmentations is to ensure 'design-for-growth' capabilities by incorporating necessary design features in the baseline program. The critical items to be accommodated in the baseline design include provisions for future increased power-generation capability, the ability to add nodes and modules, and the ability to expand the truss structure to accommodate new facilities. The SSF program must also address the effect on nonexploration users (e.g., NASA experimenters, commercial users, university investigators, and international partners of the U.S.) of SSF facilities.

Ahlf, Peter↗

NASA NTRS1990

Concurrent research on the Space Station transportation node

The feasibility of integrating scientific research on Space Station Freedom (SSF) with concurrent lunar-vehicle assembly and servicing operations associated with the support of Space Exploration Initiative (SEI) is investigated. The SSF, SEI, and lunar-vehicle user resource requirements are reviewed, and a station configuration is derived which can accommodate a significant percentage of user requirements while supporting the lunar transport vehicle (LTV) processing operations. The derived station configuration will require several augmentations to the baseline configuration. Most notably, the SSF power generation will be increased by an addition of six solar dynamic arrays, crew support will be increased by adding two habitation modules, and more payloads will be accomodated by adding dual keels.

Meredith, B. D.↗

NASA NTRS1990

Space Station Freedom flight operations in support of exploration missions

The operational requirements on Space Station Freedom (SSF) for supporting the Lunar Phase of the Space Exploration Initiative (SEI) are examined, and a concept is developed for carrying out these operations. Attention is given to the types of events and tasks that must be performed on the SSF to process the lunar vehicles, as well as to resources required for the SSF and the methods of meeting the operational requirements of the lunar missions. Critical technology areas and needs that must be addressed to enable lunar missions are also discussed.

Brender, Karen D.↗

NASA NTRS1990

Evolution of Spacelab payload operations to Space Station Freedom

NASA's Office of Space Science and Applications is actively involved in the development of operational concepts and data infrastructures which will be integrated to maximize the effectiveness of Space Station Freedom (SSF) payloads. Spacelab is noted to furnish an excellent 'experience base' for SFF activities. The SSF operations/data systems will be adaptable with respect to changes in payload manifests, in facility/apparatus complexity, and in implementing technologies; they will also be capable of flexibly accommodating the expanding needs of a highly variegated community of scientific users. Flowcharts are presented for the SSF payload operations concept, its flight operational data flows, and a data-flow growth concept.

Golden, H.↗

NASA NTRS1990

The role of Space Station Freedom in the Human Exploration Initiative

Exploration accommodation requirements for Space Station Freedom (SSF) and mission-supporting capabilities have been studied. For supporting the Human Exploration Initiative (HEI), SSF will accommodate two functions with augmentations to the baseline Assembly Complete configuration. First, it will be an earth-orbiting transportation node providing facilities and resources (crew, power, communications) for space vehicle assembly, testing, processing and postflight servicing. Second, it will be an in-space laboratory for science research and technology development. The evolutionary design of SSF will allow the on-orbit addition of pressurized laboratory and habitation modules, power generation equipment, truss structure, and unpressurized vehicle processing platforms.

Ahlf, P. R.↗

NASA NTRS1991

The dynamic effects of internal robots on Space Station Freedom

Many of the planned experiments of the Space Station Freedom (SSF) will require acceleration levels to be no greater than microgravity (10 exp -6 g) levels for long periods of time. Studies have demonstrated that without adequate control, routine operations may cause disturbances which are large enough to affect on-board experiments. One way to both minimize disturbances and make the SSF more autonomous is to utilize robots instead of astronauts for some operations. The present study addresses the feasibility of using robots for microgravity manipulation. Two methods for minimizing the dynamic disturbances resulting from the robot motions are evaluated. The first method is to use a robot with kinematic redundancy (redundant links). The second method involves the use of a vibration isolation device between the robot and the SSF laboratory module. The results from these methods are presented along with simulations of robots without disturbance control.

Miller, Jeffrey H.↗

NASA NTRS1990

Interference effects on Space Station Freedom and Space Shuttle Orbiter Ku-band single access return links

In a Ku-band single access return (KSAR) communication link via the tracking and data relay satellite system (TDRSS), the interference between spacecraft can be discriminated by opposite antenna polarizations, pseudo-noise code, and by TDRSS antenna beam pointing. For the Space Station Freedom (SSF) KSAR and the Space Shuttle Orbiter (SSO) KSAR links, the pseudo-noise coding technique is not exploited. In addition, the two KSAR links use the same carrier frequency. Therefore, if the SSF and SSO are in close proximity, it is expected that mutual interference will be significant. Mutual interference effects on the SSO-KSAR I-channel and the SSF-KSAR links are analytically derived and compared to the simulation results. For the analysis, the channel is assumed ideally bandlimited and linear. It is demonstrated that a simplified (linear bandlimited channel) analytical approach yields results of adequate accuracy in an estimation of the signal degradation by interference.

Kwon, Hyuck M.↗

NASA NTRS1992

Synergistic effects of ultraviolet radiation, thermal cycling, and atomic oxygen on altered and coated Kapton surfaces

The photovoltaic (PV) power system for Space Station Freedom (SSF) uses solar array blankets which provide structural support for the solar cells and house the electrical interconnections. In the low Earth orbital (LEO) environment where SSF will be located, surfaces will be exposed to potentially damaging environmental conditions including solar ultraviolet (UV) radiation, thermal cycling, and atomic oxygen. It is necessary to use ground based tests to determine how these environmental conditions would affect the mass loss and optical properties of candidate SSF blanket materials. Silicone containing, silicone coated, and SiO(x) coated polyimide film materials were exposed to simulated LEO environmental conditions to determine there durability and whether the environmental conditions of UV, thermal cycling and oxygen atoms act synergistically on these materials. A candidate PV blanket material called AOR Kapton, a polysiloxane polyimide cast from a solution mixture, shows an improvement in durability to oxygen atoms erosion after exposure to UV radiation or thermal cycling combined with UV radiation. This may indicate that the environmental conditions react synergistically with this material, and the damage predicted by exposure to atomic oxygen alone is more severe than that which would occur in LEO where atomic oxygen, thermal cycling and UV radiation are present together.

Dever, Joyce A.↗

NASA NTRS1991

Space station internal propagation

The Space Station Freedom (SSF) is planned with a wireless communication system in place for the transmission of information between crew members on board. The clarity of transmission is paramount to an effective system of communication. A short overview is presented of the system including the requirements of interest, and a statement of the problem. The theory used to solve the problem is explored. The results given are for the experiments performed on a mockup of the proposed structure at NASA-Marshall. The requirements on the signal level are that there is a 45 dB signal to noise ratio from end to end, and that coverage over 99 pct. of the volume be maintained. The Rice probability distribution function, a simple extension of the Rayleigh distribution, is used to estimate the field strength inside a volume, where a significant line of sight from the transmitter to the receiver exists. For the SSF, this distribution will correspond to the summation of a coherent line of sight path between the transmitter and the receiver and an incoherent portion. The incoherent portion is the sum of reflections from the walls and the equipment inside the SSF. The Rice distribution was found to be the optimal distribution from the results.

Richie, J. E.↗

NASA NTRS1991

Space Station Freedom status

Several graphs are presented which illustrate the restructuring activities of the Space Station Freedom. The restructed SSF program meets the objectives including cost guidelines. The solution adopted best features from alternative concepts. The SSF program allows significantly greater utilization opportunities than other programs. It was decided that pre-integration simplifies on-orbit assembly planning and operations. The SSF permanently manned configuration is shown.

Cox, John↗

NASA NTRS1991

Mars aerobrake assembly demonstration

NASA has identified aerobraking as a potentially critical technology for the Space Exploration Initiative (SEI). The size of Mars aerobrakes may be beyond the capabilities of future launch vehicles to place them into orbit in one launch. On-orbit assembly using facilities and operations developed under the Space Station Freedom (SSF) Program represent one approach for realizing such large structures. the results of early testing in this subject can help influence the future evolution of the SSF. The objectives are to: (1) generate empirical data on operational procedures for on-orbit assembly of a large Mars aerobrake; (2) develop aerobrake design concepts; (3) identify critical issues and requirements associated with SSF utilization; and (4) to stimulate student participation in the SEI.

Garvey, John M.↗

NASA NTRS1991

Beyond the Baseline 1991: Proceedings of the Space Station Evolution Symposium. Volume 2: Space Station Freedom, part 1

The results from the Advanced Systems Study and Advanced Development within the Space Station Freedom (SSF) Program are reported. The results show the evolution of the SSF in terms of user requirements, utilization and operations concepts, and growth options for distributed systems. Special attention is given to: highlighting changes made during restructuring; description of growth paths through the follow-on and evolution phases; identification of minimum-impact provisions to allow flexibility in the baseline; and identification of enhancing and enabling technologies. Products of these tasks include: engineering fidelity demonstrations and evaluations of advanced technology; detailed requirements, performance specifications, and design accommodations for insertion of advanced technology; and mature technology, tools, applications for SSF flight, ground, and information systems.

Source record↗

NASA NTRS1991

Solar dynamic technology status for Space Station Freedom application

The objectives of this presentation is to emphasize the (1) rationale to incorporate solar dynamic (SD) systems onto Space Station Freedom (SSF) as the power demand increases onboard SSF, (2) SD technical progress made through the SSF Program, (3) areas of further technology development, and (4) future plans for SD system development. The SD status summary is presented in graph form.

Zernic, Michael J.↗

NASA NTRS1991

Space Station Freedom electric power system evolution analysis status

The ability is examined of the SSF baselined EPS to transition to operate at a greater system capacity beyond the SSF Permanent Manned Capability PMC) milestone. Specifically, a status of a current analysis is discussed concerning additions, modifications, changeout, or combination thereof of baseline EPS hardware and/or software needed to accomplish the power generation, distribution, operation, and use needed to meet evolving SSF mission objectives. This discussion results in several EPS architectural options that facilitate the addition or substitution of new technologies.

Zernic, Michael J.↗

NASA NTRS1991

Active thermal control system evolution

The 'restructured' baseline of the Space Station Freedom (SSF) has eliminated many of the growth options for the Active Thermal Control System (ATCS). Modular addition of baseline technology to increase heat rejection will be extremely difficult. The system design and the available real estate no longer accommodate this type of growth. As the station matures during its thirty years of operation, a demand of up to 165 kW of heat rejection can be expected. The baseline configuration will be able to provide 82.5 kW at Eight Manned Crew Capability (EMCC). The growth paths necessary to reach 165 kW have been identified. Doubling the heat rejection capability of SSF will require either the modification of existing radiator wings or the attachment of growth structure to the baseline truss for growth radiator wing placement. Radiator performance can be improved by enlarging the surface area or by boosting the operating temperature with a heat pump. The optimal solution will require both modifications. The addition of growth structure would permit the addition of a parallel ATCS using baseline technology. This growth system would simplify integration. The feasibility of incorporating these growth options to improve the heat rejection capacity of SSF is under evaluation.

Petete, Patricia A.↗

NASA NTRS1991

Robust stabilization of the Space Station

A robust H-infinity control design methodology and its application to a Space Station Freedom (SSF) attitude and momentum control problem are presented. This approach incorporates nonlinear multi-parameter variations in the state-space formulation of H-infinity control theory. An application of this robust H-infinity control synthesis technique to the SSF control problem yields remarkable results in stability robustness with respect to moments of inertia variation of about 73 percent in one of the structured uncertainty directions. The performance and stability of this robust H-infinity controller for the SSF are compared to those of other controllers designed using a standard linear-quadratic-regulator synthesis technique.

Wie, Bong↗