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At least 811 records · Page 45

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DOE OSTI2021

Top-level physics requirements and simulated performance of the MRSt on the National Ignition Facility

The time-resolving Magnetic Recoil Spectrometer (MRSt) for the National Ignition Facility (NIF) has been identified by the US National Diagnostic Working Group as one of the transformational diagnostics that will reshape the way inertial confinement fusion (ICF) implosions are diagnosed. The MRSt will measure the time-resolved neutron spectrum of an implosion, from which the time-resolved ion temperature, areal density, and yield will be inferred. Top-level physics requirements for the MRSt were determined based on simulations of numerous ICF implosions with varying degrees of alpha heating, P2 asymmetry, and mix. Synthetic MRSt data were subsequently generated for different configurations using Monte–Carlo methods to determine its performance in relation to the requirements. The system was found to meet most requirements at current neutron yields at the NIF. This work was supported by the DOE and LLNL.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

NASA NTRS1961

Gas Requirements in Pressurized Transfer of Liquid Hydrogen

Of late, liquid hydrogen has become a very popular fuel for space missions. It is being used in such programs as Centaur and Saturn. Furthermore, hydrogen is the ideal working fluid for nuclear powered space vehicles currently under development. In these applications, liquid hydrogen fuel is generally transferred to the combustion chamber by a combination of pumping and pressurization. The pump forces the liquid propellant from the fuel tank to the combustion chamber; gaseous pressurant holds tank pressure sufficiently high to prevent cavitation at the pump inlet and to maintain the structural rigidity of the tank. The pressurizing system, composed of pressurant, tankage, and associated hardware can be a large portion of the total vehicle weight. Pressurant weight can be reduced by introducing the pressurizing gas at temperatures substantially greater than those of liquid hydrogen. Heat and mass transfer processes thereby induced complicate gas requirements during discharge. These requirements must be known to insure proper design of the pressurizing system. The aim of this paper is to develop from basic mass and energy transfer processes a general method to predict helium and hydrogen gas usage for the pressurized transfer of liquid hydrogen. This required an analytical and experimental investigation, the results of which are described in this paper.

GAS↗

NASA NTRS1963

LATERAL-RANGE AND HYPERSONIC LIFT-DRAG-RATIO REQUIREMENTS FOR EFFICIENT FERRY SERVICE FROM A NEAR-EARTH MANNED SPACE STATION

The operation of any long-term manned space station will require some type of ferry vehicle to transport men and equipment to and from the station with regularity and reliability. Such a vehicle, designed for entry at near-orbital speeds, could also be useful in the return from any deeper space mission if either an earth-orbit rendezvous terminal maneuver or a maneuver combining atmospheric braking and a near-earth parking orbit is used. This study was undertaken to determine the class of vehicle which could be most efficiently used as a ferry vehicle between a near-earth space station and the earth. One measure of this efficiency is the ability of the vehicle to reach pre-chosen landing sites with some prescribed frequency. In considering this frequency of return it is necessary to consider not only the normal mode of operation in which only infrequent returns are scheduled at desirable times, but also operation under various degrees of emergency, which dictate quick or even immediate return to earth. In extreme emergencies, when immediate return to earth is necessary, choice of landing site becomes impractical. In most cases, however, although it might be required to abandon the station quickly, the ferry vehicle could remain in orbit for some time before initiating reentry in order to land at a prechosen site. The allowable delay time in orbit would be determined primarily by the capabilities of the ferry life-support system. This paper will examine the geometry of the ferry ranging problem, that is, the lateral ranges required to reach chosen landing sites from various near-earth orbits, and will investigate and compare several means of achieving these ranges. The particular case considered is that of returning from a space station which is in a circular orbit at an altitude of 200 statute miles, but the results obtained are not sensitive to orbit altitude for orbits within a few hundred miles of the surface. From this orbit, the vehicle will retro and reenter at very close to satellite velocity. The downrange problem can be handled by proper timing of the retrofiring , and the desired lateral range can be achieved by aerodynamics, space propulsion to change orbit plane, atmospheric propulsion, or combinations of these methods. The relative cost in terms of weight of using these different methods to achieve lateral range will be discussed.

Hypersonic vehicle↗

NASA NTRS1964

Biomedical and Human Factors Requirements for a Manned Earth Orbiting Station

The primary objective of this study is to determine which biomedical and human factors measurements must be made aboard a space station to assure adequate evaluation of the astronaut's health and performance during prolonged space flights. The study has employed, where possible, a medical and engineering systems analysis to define the pertinent life sciences and space station design parameters and their influence on a measurement program. The major areas requiring evaluation in meeting the study objectives include a definition of the space environment, man's response to the environment, selection of measurement and data management techniques, experimental program, space station design requirements, and a trade-off analysis with final recommendations. The space environment factors that are believed to have a significant effect on man were evaluated. This includes those factors characteristic of the space environment (e. g. weightlessness, radiation) as well as those created within the space station (e. g. toxic contaminants, capsule atmosphere). After establishing the general features of the environment, an appraisal was made of the anticipated response of the astronaut to each of these factors. For thoroughness, the major organ systems and functions of the body were delineated, and a determination was made of their anticipated response to each of the environmental categories. A judgment was then made on the medical significance or importance of each response, which enabled a determination of which physiological and psychological effects should be monitored. Concurrently, an extensive list of measurement techniques and methods of data management was evaluated for applicability to the space station program. The various space station configurations and design parameters were defined in terms of the biomedical and human factors requirements to provide the measurements program. Research design of experimental programs for various station configurations, mission durations, and crew sizes were prepared, and, finally, a trade-off analysis of the critical variables in the station planning was completed with recommendations to enhance the confidence in the measurement program.

EARTH ORBIT↗

NASA NTRS1971

Manned spacecraft nonmetallic-materials flammability selection criteria and requirements

The criteria and requirements governing the selection and use of nonmetallic materials in manned spacecraft to control potential fire hazards are reviewed. The development of flammability requirements is discussed and traced through the historical evolution. Events that dictated the changes that have taken place are discussed. The current nonmetallic material requirements are presented. Significant features of a nonmetallic materials handbook are included.

Katsikas, C. J.↗

NASA NTRS1972

Mariner Venus-Mercury 1973 midcourse velocity requirements and delivery accuracy

The primary mission is described, which consists of encounters with Venus and Mercury; (a second encounter with Mercury is also possible). The exptected navigation sequences were simulated with a Monte Carlo computer program for the purpose of determining midcourse correction velocity requirements and delivery accuracies. These simulations provide sensitivity in velocity requirements and delivery accuracies to error sources affecting the navigation process. The orbit determination capability at the final pre-Venus maneuver is shown to be the dominant contributor to the velocity requirements for the primary mission. Similarly, the orbit determination capability at the final pre-Mercury maneuver is shown to be the dominant contributor to the delivery accuracy at Mercury.

Mckinley, E. L.↗

NASA NTRS1971

Modular space station phase B extension: Shuttle interface requirements

The interface requirements cover both the ground and orbital phases of operation from the launch of the first MSS module until the initial modular station has been manned and in routine operation. As a point of reference, the two-stage, fully reusable space shuttle was selected. The space shuttle is briefly described from the standpoint of its features most important to the interface requirements with the MSS. The environment induced upon the MSS elements when transported to and from orbit by the shuttle orbiter also is included. The mission operation includes the space shuttle launch facilities, the ground flow of the MSS modules, and the orbital operations of rendezvous, MSS buildup, resupply of the manned station, and orbiter descent and landing. The shuttle's once-around abort case is described as it affects the MSS interface requirements. The interfaces between the orbiter and the MSS resulting from the ground and orbital operations, are also described.

Source record↗

NASA NTRS1972

Shuttle/Agena study. Volume 2, part 1: Program requirements, conclusions, recommendations

An evaluation to determine the compatibility of the Agena with the space transportation system for use as an expendable third stage to the space shuttle was conducted. The Agena was considered for those missions requiring additional propulsion capability beyond that used for low earth orbit. The study defines the interface requirements imposed on both the Agena and the shuttle system and identifies those areas where the Agena must be improved or modified to satisfy mission requirements.

Source record↗

NASA NTRS1972

Effect of commercial and military performance requirements for transport category aircraft on space shuttle booster design and operation

The effect of two sets of performance requirements, commercial and military, on the design and operation of the space shuttle booster is evaluated. Critical thrust levels are established according to both sets of operating rules for the takeoff, cruise, and go-around flight modes, and the effect on engine requirements determined. Both flyback and ferry operations are considered. The impact of landing rules on potential shuttle flyback and ferry bases is evaluated. Factors affecting reserves are discussed, including winds, temperature, and nonstandard flight operations. Finally, a recommended set of operating rules is proposed for both flyback and ferry operations that allows adequate performance capability and safety margins without compromising design requirements for either flight phase.

Bithell, R. A.↗

NASA NTRS1972

Flight program language requirements. Volume 1: Executive summary

The activities and results of a study for the definition of flight program language requirements are described. A set of detailed requirements are presented for a language capable of supporting onboard application programming for the Marshall Space Flight Center's anticipated future activities in the decade of 1975-85. These requirements are based, in part, on the evaluation of existing flight programming language designs to determine the applicability of these designs to flight programming activities which are anticipated. The coding of benchmark problems in the selected programming languages is discussed. These benchmarks are in the form of program kernels selected from existing flight programs. This approach was taken to insure that the results of the study would reflect state of the art language capabilities, as well as to determine whether an existing language design should be selected for adaptation.

Source record↗

NASA NTRS1972

Development of approach control system requirements with applications to a jet transport

The development of requirements for an approach control system and example applications to a jet transport aircraft are presented. The material is divided into a general discussion of approach control requirements, and a specific application resulting in the design of three alternative longitudinal controllers. The point of view taken is that the essential features of the system structure are the feedbacks themselves, their equalization, and their combinations to create control commands. Use is made of the fact that for sucessful systems the possible feedback structures are very limited. They derive primarily from guidance, control, and regulation demands; and secondarily from dynamic response characteristics desired by the pilot. From the systems view it is the satisfaction of these requirements that is important rather than the means automatic, manual, or hygrid manual/automatic approach systems.

Mcruer, D. T.↗

NASA NTRS1972

Photovoltaic solar array technology required for three wide scale generating systems for terrestrial applications: rooftop, solar farm, and satellite

Three major options for wide-scale generation of photovoltaic energy for terrestrial use are considered: (1) rooftop array, (2) solar farm, and (3) satellite station. The rooftop array would use solar cell arrays on the roofs of residential or commercial buildings; the solar farm would consist of large ground-based arrays, probably in arid areas with high insolation; and the satellite station would consist of an orbiting solar array, many square kilometers in area. The technology advancement requirements necessary for each option are discussed, including cost reduction of solar cells and arrays, weight reduction, resistance to environmental factors, reliability, and fabrication capability, including the availability of raw materials. The majority of the technology advancement requirements are applicable to all three options, making possible a flexible basic approach regardless of the options that may eventually be chosen. No conclusions are drawn as to which option is most advantageous, since the feasibility of each option depends on the success achieved in the technology advancement requirements specified.

Berman, P. A.↗

NASA NTRS1971

Power processing requirements for solar electric propulsion.

The successful integration of a light-weight, high-efficiency power conditioning (PC) unit with an electron bombardment ion thruster using a hollow cathode at JPL has been reported recently. This paper summarizes the presently conceived requirements by which the next generation of PCs should be judged and evaluated. The requirements are formulated in terms of a deep space mission, which implies that the characteristics of the solar source will vary in terms of output power and output voltage. The requirements identified by practical experience during long-term evaluation between 1968-1970 are described and explained.

Macie, T. W.↗

NASA NTRS1972

Minimizing the area required for time constants in integrated circuits

When a medium- or large-scale integrated circuit is designed, efforts are usually made to avoid the use of resistor-capacitor time constant generators. The capacitor needed for this circuit usually takes up more surface area on the chip than several resistors and transistors. When the use of this network is unavoidable, the designer usually makes an effort to see that the choice of resistor and capacitor combinations is such that a minimum amount of surface area is consumed. The optimum ratio of resistance to capacitance that will result in this minimum area is equal to the ratio of resistance to capacitance which may be obtained from a unit of surface area for the particular process being used. The minimum area required is a function of the square root of the reciprocal of the products of the resistance and capacitance per unit area. This minimum occurs when the area required by the resistor is equal to the area required by the capacitor.

Lyons, J. C.↗

NASA NTRS1972

Data processing requirements for the Earth Resources Technology Satellite (ERTS)

Some of the data handling considerations that led to the formulation of the data processing requirements for the ERTS system are discussed. The significant parameters that influence these requirements are: (1) payload characteristics, (2) spacecraft characteristics such as orbit, attitude and attitude rates, (3) payload coverage, and (4) product types and quantities. Items 3 and 4 have had the most significant influence on the generation of the requirements.

Sos, J. Y.↗

NASA NTRS1972

Space shuttle auxiliary propulsion system design study. Phase A report: Requirements definition

The analyses and rationale used to develop requirements for the oxygen-hydrogen auxiliary propulsion systems to be used with the space shuttle are presented. The requirements apply to a fully reusable space shuttle vehicle system using internal, reusable main engine propellant tanks in both the orbiter and booster stages. Requirements of principal interest are engine thrust, number of engines, maximum system thrust, total impulse, and total impulse expenditure history.

Orton, G. F.↗

NASA NTRS1972

Astronomy sortie missions definition study. Volume 4: Program development requirements

Program development requirements for the selected Astronomy Sortie Missions concept were generated and are presented in four parts as follows: (1)the gross planning requirements that must be considered in subsequent phases of the project; (2)the schedules and logic networks for the design, development, and operation of the overall project; (3)the supporting research and technology required to support the project; and (4)the work breakdown data, from which cost data will be generated. Data reported in each part includes the appropriate rationale with explanations of the guidelines and assumptions that were used in the analyses and estimates.

Source record↗

NASA NTRS1973

Study of space shuttle EVA/IVA support requirements. Volume 1: Technical summary report

Results are summarized which were obtained for equipment requirements for the space shuttle EVA/IVA pressure suit, life support system, mobility aids, vehicle support provisions, and energy 4 support. An initial study of tasks, guidelines, and constraints and a special task on the impact of a 10 psia orbiter cabin atmosphere are included. Supporting studies not related exclusively to any one group of equipment requirements are also summarized. Representative EVA/IVA task scenarios were defined based on an evaluation of missions and payloads. Analysis of the scenarios resulted in a total of 788 EVA/IVA's in the 1979-1990 time frame, for an average of 1.3 per shuttle flight. Duration was estimated to be under 4 hours on 98% of the EVA/IVA's, and distance from the airlock was determined to be 70 feet or less 96% of the time. Payload water vapor sensitivity was estimated to be significant on 9%-17% of the flights. Further analysis of the scenarios was carried out to determine specific equipment characteristics, such as suit cycle and mobility requirements.

Copeland, R. J.↗