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At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

User modeling techniques for enhanced usability of OPSMODEL operations simulation software

The PC based OPSMODEL operations software for modeling and simulation of space station crew activities supports engineering and cost analyses and operations planning. Using top-down modeling, the level of detail required in the data base can be limited to being commensurate with the results required of any particular analysis. To perform a simulation, a resource environment consisting of locations, crew definition, equipment, and consumables is first defined. Activities to be simulated are then defined as operations and scheduled as desired. These operations are defined within a 1000 level priority structure. The simulation on OPSMODEL, then, consists of the following: user defined, user scheduled operations executing within an environment of user defined resource and priority constraints. Techniques for prioritizing operations to realistically model a representative daily scenario of on-orbit space station crew activities are discussed. The large number of priority levels allows priorities to be assigned commensurate with the detail necessary for a given simulation. Several techniques for realistic modeling of day-to-day work carryover are also addressed.

Davis, William T.↗
NASA NTRS1990

Recursive dynamics for flexible multibody systems using spatial operators

Due to their structural flexibility, spacecraft and space manipulators are multibody systems with complex dynamics and possess a large number of degrees of freedom. Here the spatial operator algebra methodology is used to develop a new dynamics formulation and spatially recursive algorithms for such flexible multibody systems. A key feature of the formulation is that the operator description of the flexible system dynamics is identical in form to the corresponding operator description of the dynamics of rigid multibody systems. A significant advantage of this unifying approach is that it allows ideas and techniques for rigid multibody systems to be easily applied to flexible multibody systems. The algorithms use standard finite-element and assumed modes models for the individual body deformation. A Newton-Euler Operator Factorization of the mass matrix of the multibody system is first developed. It forms the basis for recursive algorithms such as for the inverse dynamics, the computation of the mass matrix, and the composite body forward dynamics for the system. Subsequently, an alternative Innovations Operator Factorization of the mass matrix, each of whose factors is invertible, is developed. It leads to an operator expression for the inverse of the mass matrix, and forms the basis for the recursive articulated body forward dynamics algorithm for the flexible multibody system. For simplicity, most of the development here focuses on serial chain multibody systems. However, extensions of the algorithms to general topology flexible multibody systems are described. While the computational cost of the algorithms depends on factors such as the topology and the amount of flexibility in the multibody system, in general, it appears that in contrast to the rigid multibody case, the articulated body forward dynamics algorithm is the more efficient algorithm for flexible multibody systems containing even a small number of flexible bodies. The variety of algorithms described here permits a user to choose the algorithm which is optimal for the multibody system at hand. The availability of a number of algorithms is even more important for real-time applications, where implementation on parallel processors or custom computing hardware is often necessary to maximize speed.

Jain, A.↗
NASA NTRS1991

Space Station Freedom payload operations in the 21st century

The modified approach to the accomodation of payload operations in light of both flight and ground systems changes to the operational concept for the Space Station Freedom is described. The challenges for the man-tended capability payload operations and those for the permanently manned capability are assessed. An overview of payload operations is presented including payload accomodations, operations modes, ground systems, the payload operations integration center, and the evolution from man-tended capability to permanent manning.

Griner, C. S.↗
NASA NTRS1991

Operational perspectives for performing microgravity science in orbit

The combination of automation and operator-based technologies is discussed with respect to orbital microgravity experiments in order to optimize the performance and results. A list of five design objectives is presented, and each item is examined in terms of on-orbit flight history to identify relevant examples. It is suggested that human factors be considered in hardware design and that in-flight maintenance operations be considered an integral part of a program. The operational design can produce more effective results when it is established for 'failures' and mission success operations. The design must also be approached in terms of both the limitations and advantages of microgravity. The overarching theme of the investigation is that the mix of automation and operator interaction should be optimized by automating routine tasks and using the operator for critical assessments.

Dunbar, Bonnie J.↗
NASA NTRS1992

Ulysses mission operations

The Ulysses mission is described in terms of in-Shuttle operations, initial in-orbit operations, routine operations, operational organization, and data gathering and production. The configuration of the Ulysses payload is illustrated, and the flight to orbit is described including a three-hour on-orbit checkout. The first contact was reported at the Deep Space Network station followed by an adjustment of the spacecraft solar-aspect angle and the acquisition of ranging and Doppler data. In-orbit operations include the earth acquisition maneuver, a trajectory correction maneuver, and a payload switch. Continuous data gathering is discussed with reference to the Jupiter encounter and the first and second oppositions and conjunctions. The data-gathering components comprise ground stations, a data-processing computer, and a data-records system. Data production is performed in an off-line mode that does not interfere with the real-time operations.

Beech, P.↗
NASA NTRS1992

Automating simulator operations

A set of requirements are defined for an operations support system for automating operations in the Space Station Training Facility (SSTF). An operations concept is described based on utilization studies and facility-operations plans with specific attention given to the SSTF components. The Operations Support System (OSS) is designed to have an integrated set of tools for system configuration and realtime data monitoring, analysis, and control. The concept relies on a system configuration tool for connecting and verifying hardware and software components, and a status-and-control monitor is envisaged to collect data. The SSTF OSS is expected to enhance the effectiveness of simulator training by configuring the components for training, monitoring and controlling components, and conducting all operations in real time.

Jacobs, Rebecca J.↗
NASA NTRS1992

Space Station Freedom payload operations from the user's perspective

This report describes the Microgravity Science and Applications Division's (MSAD) operations concept for using the Space Station Freedom (SSF) program ground data systems and services, and the plans for and capabilities of the MSAD remote User Operations Facilities (UOF) from which the MSAD SSF payloads will be operated. Attention is given to the MSAD operational phases, the MSAD UOF concept, and UOF operations teams. MSAD is planning remote payload operations for a number of Spacelab missions which will supply MSAD valuable information for application to the development of UOFs in the SSF era.

Robey, J. L.↗
NASA NTRS1992

Economic benefits of supersonic overland operation

Environmental concerns are likely to impose some restrictions on the next generation of supersonic commercial transport. There is a global concern over the effects of engine emissions on the ozone layer which protects life on Earth from ultraviolet radiation. There is also some concern over community noise. The High Speed Civil Transport (HSCT) must meet at least the current subsonic noise certification standards to be compatible with the future subsonic fleet. Concerns over sonic boom represent another environmental and marketing challenge to the HSCT program. The most attractive feature of the supersonic transport is speed, which offers the traveling public significant time-savings on long range routes. The sonic boom issue represents a major environmental and economic challenge as well. Supersonic operation overland produces the most desirable economic results. However, unacceptable overland sonic boom raise levels may force HSCT to use subsonic speeds overland. These environmental and economic challenges are likely to impose some restrictions on supersonic operation, thus introducing major changes to existing route structures and future supersonic network composition. The current subsonic route structure may have to be altered for supersonic transports to avoid sensitive areas in the stratosphere or to minimize overland flight tracks. It is important to examine the alternative route structure and the impact of these restrictions on the economic viability of the overall supersonic operation. Future market potential for HSCT fleets must be large enough to enable engine and airframe manufacturers to build the plane at a cost that provides them with an attractive return on investment and to sell it at a price that allows the airlines to operate with a reasonable margin of profit. Subsonic overland operation of a supersonic aircraft hinders its economic viability. Ways to increase the market potential of supersonic operation are described.

Metwally, Munir↗
NASA NTRS1992

Role of automation in the ACRV operations

The Assured Crew Return Vehicle (ACRV) will provide the Space Station Freedom with contingency means of return to earth (1) of one disabled crew member during medical emergencies, (2) of all crew members in case of accidents or failures of SSF systems, and (3) in case of interruption of the Space Shuttle flights. A wide range of vehicle configurations and system approaches are currently under study. The Program requirements focus on minimizing life cycle costs by ensuring simple operations, built-in reliability and maintainability. The ACRV philosophy of embedded operations is based on maximum use of existing facilities, resources and processes, while minimizing the interfaces and impacts to the Space Shuttle and Freedom programs. A preliminary integrated operations concept based on this philosophy and covering the ground, flight, mission support, and landing and recovery operations has been produced. To implement the ACRV operations concept, the underlying approach has been to rely on vehicle autonomy and automation, to the extent possible. Candidate functions and processes which may benefit from current or near-term automation and robotics technologies are identified. These include, but are not limited to, built-in automated ground tests and checkouts; use of the Freedom and the Orbiter remote manipulator systems, for ACRV berthing; automated passive monitoring and performance trend analysis, and periodic active checkouts during dormant periods. The major ACRV operations concept issues as they relate to the use of automation are discussed.

Sepahban, S. F.↗
NASA NTRS1991

Spacecraft rendezvous operational considerations affecting vehicle systems design and configuration

One lesson learned from Orbiting Maneuvering Vehicle (OMV) program experience is that Design Reference Missions must include an appropriate balance of operations and performance inputs to effectively drive vehicle systems design and configuration. Rendezvous trajectory design is based on vehicle characteristics (e.g., mass, propellant tank size, and mission duration capability) and operational requirements, which have evolved through the Gemini, Apollo, and STS programs. Operational constraints affecting the rendezvous final approach are summarized. The two major objectives of operational rendezvous design are vehicle/crew safety and mission success. Operational requirements on the final approach which support these objectives include: tracking/targeting/communications; trajectory dispersion and navigation uncertainty handling; contingency protection; favorable sunlight conditions; acceptable relative state for proximity operations handover; and compliance with target vehicle constraints. A discussion of the ways each of these requirements may constrain the rendezvous trajectory follows. Although the constraints discussed apply to all rendezvous, the trajectory presented in 'Cargo Transfer Vehicle Preliminary Reference Definition' (MSFC, May 1991) was used as the basis for the comments below.

Prust, Ellen E.↗
NASA NTRS1991

White paper on science operations

Major changes are taking place in the way astronomy gets done. There are continuing advances in observational capabilities across the frequency spectrum, involving both ground-based and space-based facilities. There is also very rapid evolution of relevant computing and data management technologies. However, although the new technologies are filtering in to the astronomy community, and astronomers are looking at their computing needs in new ways, there is little coordination or coherent policy. Furthermore, although there is great awareness of the evolving technologies in the arena of operations, much of the existing operations infrastructure is ill-suited to take advantage of them. Astronomy, especially space astronomy, has often been at the cutting edge of computer use in data reduction and image analysis, but has been somewhat removed from advanced applications in operations, which have tended to be implemented by industry rather than by the end-user scientists. The purpose of this paper is threefold. First, we briefly review the background and general status of astronomy-related computing. Second, we make recommendations in three areas: data analysis; operations (directed primarily to NASA-related activities); and issues of management and policy, believing that these must be addressed to enable technological progress and to proceed through the next decade. Finally, we recommend specific NASA-related work as part of the Astrotech-21 plans, to enable better science operations in the operations of the Great Observatories and in the lunar outpost era.

Schreier, Ethan J.↗
NASA NTRS1992

Non-LTE radiative transfer with lambda-acceleration - Convergence properties using exact full and diagonal lambda-operators

We investigate the convergence properties of Lambda-acceleration methods for non-LTE radiative transfer problems in planar and spherical geometry. Matrix elements of the 'exact' A-operator are used to accelerate convergence to a solution in which both the radiative transfer and atomic rate equations are simultaneously satisfied. Convergence properties of two-level and multilevel atomic systems are investigated for methods using: (1) the complete Lambda-operator, and (2) the diagonal of the Lambda-operator. We find that the convergence properties for the method utilizing the complete Lambda-operator are significantly better than those of the diagonal Lambda-operator method, often reducing the number of iterations needed for convergence by a factor of between two and seven. However, the overall computational time required for large scale calculations - that is, those with many atomic levels and spatial zones - is typically a factor of a few larger for the complete Lambda-operator method, suggesting that the approach should be best applied to problems in which convergence is especially difficult.

Macfarlane, J. J.↗
NASA NTRS1992

Operations planning for Space Station Freedom - And beyond

The potential of automated planning and electronic execution systems for enhancing operations on board Space Station Freedom (SSF) are discussed. To exploit this potential the Operations Planning and Scheduling Subsystem is being developed at the NASA Johnson Space Center. Such systems may also make valuable contributions to the operation of resource-constrained, long-duration space habitats of the future. Points that should be considered during the design of future long-duration manned space missions are discussed. Early development of a detailed operations concept as an end-to-end mission description offers a basis for iterative design evaluation, refinement, and option comparison, particularly when used with an advanced operations planning system capable of modeling the operations and resource constraints of the proposed designs.

Gibson, Stephen S.↗
NASA NTRS1993

Extreme Ultraviolet Explorer Science Operation Center

The EUVE Science Operations Center (ESOC) is a satellite payload operations center for the Extreme Ultraviolet Explorer project, located on the Berkeley campus of the University of California. The ESOC has the primary responsibility for commanding the EUVE telescopes and monitoring their telemetry. The ESOC is one of a very few university-based satellite operations facilities operating with NASA. This article describes the history, operation, and advantages of the ESOC as an on-campus operations center.

Wong, G. S.↗
NASA NTRS1989

The structure of the clouds distributed operating system

A novel system architecture, based on the object model, is the central structuring concept used in the Clouds distributed operating system. This architecture makes Clouds attractive over a wide class of machines and environments. Clouds is a native operating system, designed and implemented at Georgia Tech. and runs on a set of generated purpose computers connected via a local area network. The system architecture of Clouds is composed of a system-wide global set of persistent (long-lived) virtual address spaces, called objects that contain persistent data and code. The object concept is implemented at the operating system level, thus presenting a single level storage view to the user. Lightweight treads carry computational activity through the code stored in the objects. The persistent objects and threads gives rise to a programming environment composed of shared permanent memory, dispensing with the need for hardware-derived concepts such as the file systems and message systems. Though the hardware may be distributed and may have disks and networks, the Clouds provides the applications with a logically centralized system, based on a shared, structured, single level store. The current design of Clouds uses a minimalist philosophy with respect to both the kernel and the operating system. That is, the kernel and the operating system support a bare minimum of functionality. Clouds also adheres to the concept of separation of policy and mechanism. Most low-level operating system services are implemented above the kernel and most high level services are implemented at the user level. From the measured performance of using the kernel mechanisms, we are able to demonstrate that efficient implementations are feasible for the object model on commercially available hardware. Clouds provides a rich environment for conducting research in distributed systems. Some of the topics addressed in this paper include distributed programming environments, consistency of persistent data and fault-tolerance.

Dasgupta, Partha↗
NASA NTRS1990

A radiological assessment of space nuclear power operations near Space Station Freedom

In order to accomplish NASA's more ambitious exploration goals, nuclear reactors may be used in the vicinity of Space Station Freedom (SSF) either as power sources for coorbiting platforms or as part of the propulsion system for departing and returning personnel or cargo vehicles. This study identifies ranges of operational parameters, such as parking distances and reactor cooldown times, which would reasonably guarantee that doses to the SSF crew from all radiation sources would be below guidelines recently recommended by the National Council of Radiation Protection and Measurements. The specific scenarios considered include: (1) the launch and return of a nuclear electric propulsion vehicle, (2) the launch and return of a nuclear thermal rocket vehicle, (3) the operation of an SP-100 class reactor on a coorbiting platform, (4) the activation of materials near operating reactors, (5) the storage and handling of radioisotope thermal generator units, and (6) the storage and handling of fresh and previously operated reactors. Portable reactor shield concepts were examined for relaxing the operational constraints imposed by unshielded (for human proximity operations) reactors and that might also be used to provide additional SSF crew protection from natural background radiation.

Stevenson, Steve↗
NASA NTRS1993

Floquet operator as integral of motion

Nonstationary quantum systems have no energy levels. However, for time-dependent periodical quantum systems, the notion of quasi-energy levels has been introduced. The main point of the quasi-energy concept is to relate quasi-energies to eigenvalues of the Floquet operator or monodromy operators which is equal to the evolution operator of a quantum system taken at the moment coinciding with the period of the system. The purpose of this article is to relate the Floquet operator to integrals of the motion and to introduce a new operator which is the integral of motion and has the same quasi-energy spectrum that the Floquet operator has. We wish to discuss an explicit formula for this new integral of motion.

Manko, V. I.↗
NASA NTRS1993

HP upgrade operational streamlining

New computer technology and resources must be successfully integrated into CDSLR station operations to manage new complex operational tracking requirements, support the on site production of new data products, support ongoing station performance improvements, and to support new station communication requirements. The NASA CDSLR Network is in the process of upgrading station computer resources with HP UNIX workstations, designed to automate a wide range of operational station requirements. The primary HP upgrade objective was to relocate computer intensive data system tasks from the controller computer to a new advanced computer environment designed to meet the new data system requirements. The HP UNIX environment supports fully automated real time data communications, data management, data processing, and data quality control. Automated data compression procedures are used to improve the efficiency of station data communications. In addition, the UNIX environment supports a number of semi-automated technical and administrative operational station tasks. The x window user interface generates multiple simultaneous color graphics displays, providing direct operator visibility and control over a wide range of operational station functions.

Edge, David R.↗