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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Conceptual design and analysis of roads and road construction machinery for initial lunar base operations

Recent developments have made it possible for scientists and engineers to consider returning to the Moon to build a manned lunar base. The base can be used to conduct scientific research, develop new space technology, and utilize the natural resources of the Moon. Areas of the base will be separated, connected by a system of roads that reduce the power requirements of vehicles traveling on them. Feasible road types for the lunar surface were analyzed and a road construction system was designed for initial lunar base operations. A model was also constructed to show the system configuration and key operating features. The alternate designs for the lunar road construction system were developed in four stages: analyze and select a road type; determine operations and machinery needed to produce the road; develop machinery configurations; and develop alternates for several machine components. A compacted lunar soil road was selected for initial lunar base operations. The only machinery required to produce this road were a grader and a compactor. The road construction system consists of a main drive unit which is used for propulsion, a detachable grader assembly, and a towed compactor.

Sines, Jeffrey L.↗
NASA NTRS1990

Gravity wave initiated convection

The vertical velocity of convection initiated by gravity waves was investigated. In one particular case, the convective motion-initiated and supported by the gravity wave-induced activity (excluding contributions made by other mechanisms) reached its maximum value about one hour before the production of the funnel clouds. In another case, both rawinsonde and geosynchronous satellite imagery were used to study the life cycles of severe convective storms. Cloud modelling with input sounding data and rapid-scan imagery from GOES were used to investigate storm cloud formation, development and dissipation in terms of growth and collapse of cloud tops, as well as, the life cycles of the penetration of overshooting turrets above the tropopause. The results based on these two approaches are presented and discussed.

Hung, R. J.↗
NASA NTRS1989

The intrinsic luminosity and initial period of pulsars

The observed properties of pulsars are modeled on the assumption that they evolve by emitting magnetic dipole radiation and have exponentially decaying magnetic fields. The models are constructed by using Monte Carlo techniques to generate a Galactic sample of pulsars having particular distributions of initial periods, magnetic dipole moments, and positions. By choosing a relationship between the radio luminosity L(r), the period (P), and the P derivative, it is determined which pulsars of the generated sample could be detected by one of the major pulsar surveys. Detailed account is taken of known selection effects in these surveys. Models in which the size of the pulsar emission cone is dependent on the period are considered. The properties of the detectable pulsars are compared with the properties of the observed pulsars, and the initial distributions and luminosity relation of the model are adjusted until a satisfactory agreement is obtained. A crucial point is that the observed relation between L(r) and P, P derivative is affected by selection effects and does not apply to the actual pulsar population. It is found that the best fits are obtained with models in which the pulsars are injected with relatively long periods, about 0.5 sec.

Emmering, Robert T.↗
NASA NTRS1989

Rocks and stars - Educational initiatives for the ISY

Several new initiatives of interest to space educators are discussed, with a focus on directions for the dissemination of space science and space technology information, materials, and philosophy. These initiatives involve kindergarten through university teaching, workshops, and programs, development of curricular guides and slide sets, and media presentation of information concerning flight missions.

Dasch, E. Julius↗
NASA NTRS1989

Initial findings from a telescopic search for small comets near earth

An analysis is provided for the capabilities of the Spacewatch Camera operated at Kitt Peak National Observatory by the University of Arizona for the detection of the large flux of small comets in the vicinity of earth that is proposed by Frank et al. (1986). The characteristics of this telescope are used to determine its optimum operational mode for the detection of these small comets. It is concluded that the Spacewatch Camera can detect these small comets near earth if the proposed large fluxes in prograde orbits are present. It is unlikely that previous optical telescope surveys would have detected these objects. A heretofore undetected, large flux of small objects was detected. The characteristics of these objects appear to be in general agreement with those of the comets proposed by Frank et al. (1986). No other known population of objects or other effects that could provide the observed optical signatures has been identified at this time. Because these initial results are of such great importance to our perception of the solar system, they should be conservatively treated as an initial result until confirmation is made with similar observations from other telescopes.

Yeates, C. M.↗
NASA NTRS1990

Specification of the scale and magnitude of thermals used to initiate convection in cloud models

Boundary layer similarity techniques are employed to specify the scale and intensity of a thermal perturbation used to initialize a cloud in a numerical cloud model. Techniques are outlined to specify the needed similarity variables from external information. Finally, the cloud model respone using the similarity scaled thermal is analyzed employing variations in the similarity variables giving an indication of the importance of the correct specification of the initiating thermal.

Mcnider, Richard T.↗
NASA NTRS1990

Crack initiation and growth toughness of an aluminum metal-matrix composite

The effects of systematic changes in matrix microstructure on crack initiation and growth toughnesses were determined on an Al-Zn-Mg-Cu alloy containing 0, 15, 20 percent by volume of SiC particulates. Materials were heat treated to underaged (UA) and overaged (OA) conditions of equivalent matrix microhardness and flow stress. Although both the fracture initiation and growth toughnesses, as measured by JIc and tearing modulus, were similar for the unreinforced materials in the UA and OA conditions, significant effects of microstructure on both JIc and tearing modulus were observed in the composites. SEM and TEM observations of fracture paths in the two conditions are utilized to rationalize these observations in light of existing theories of ductile fracture propagation.

Manoharan, M.↗
NASA NTRS1990

Benefits of electric propulsion for the Space Exploration Initiative

An overview of the benefits which may be derived through the use of electric propulsion in support of the Space Exploration Initiative is presented. Lunar cargo, Mars cargo and piloted Mars vehicles using electric propulsion are considered. The high performance of electric propulsion systems is shown to offer substantial benefits for these applications, including: substantially reduced initial masses in low earth orbit, reduced round-trip times for piloted Mars vehicles, availability of large amounts of electrical power en route and at the destination, less sensitivity to launch dates and windows, reusability, and growth potential for human exploration of the solar system. Hybrid chemical/NEP and NTR/NEP vehicles are discussed for their potential to reduce piloted round-trip time to Mars even further. A brief technology assessment of the major electric propulsion system components is also presented.

Brophy, John R.↗
NASA NTRS1990

Civil space technology initiative

The Civil Space Technology Initiative (CSTI) is a major, focused, space technology program of the Office of Aeronautics, Exploration and Technology (OAET) of NASA. The program was initiated to advance technology beyond basic research in order to expand and enhance system and vehicle capabilities for near-term missions. CSTI takes critical technologies to the point at which a user can confidently incorporate the new or expanded capabilities into relatively near-term, high-priority NASA missions. In particular, the CSTI program emphasizes technologies necessary for reliable and efficient access to and operation in Earth orbit as well as for support of scientific missions from Earth orbit.

Source record↗
NASA NTRS1990

A personal history of the human exploration initiative with commentary on the pivotal role for life support research

The author relates the history of the human exploration initiative from a personal perspective from the 1961 J. F. Kennedy initiative to land a man on the moon up to 1986 when a memo was circulated from NASA Headquarters to its employees which stated as a major goal the expansion of the human presence beyond Earth into the solar system. The pivotal role of life support research is woven into this personalized history.

Mendell, Wendell↗
NASA NTRS1990

West Antarctic Ice Sheet Initiative. Volume 1: Science and Implementation Plan

The Science and Implementation Plan of the West Antarctic Ice Sheet Initiative (WAIS) is described. The goal of this initiative is the prediction of the future behavior of this ice sheet and an assessment of its potential to collapse, rapidly raising global sea level. The multidisciplinary nature of WAIS reflects the complexity of the polar ice sheet environment. The project builds upon past and current polar studies in many fields and meshes with future programs of both the U.S. and other countries. Important tasks in each discipline are described and a coordinated schedule by which the majority of these tasks can be accomplished in 5 years is presented. The companion report (Volume 2) contains seven discipline review papers on the state of knowledge of Antarctica and opinions on how that knowledge must be increased to attain the WAIS goal.

Bindschadler, Robert A.↗
NASA NTRS1991

An assessment of technology alternatives for telecommunications and information management for the space exploration initiative

On the 20th anniversary of the Apollo 11 lunar landing, President Bush set forth ambitious goals for expanding human presence in the solar system. The Space Exploration Initiative (SEI) addresses these goals beginning with Space Station Freedom, followed by a permanent return to the Moon, and a manned mission to Mars. A well designed, adaptive Telecommunications, Navigation, and Information Management (TNIM) infrastructure is vital to the success of these missions. Utilizing initial projections of user requirements, a team under the direction of NASA's Office of Space Operations developed overall architectures and point designs to implement the TNIM functions for the Lunar and Mars mission scenarios. Based on these designs, an assessment of technology alternatives for the telecommunications and information management functions was performed. This technology assessment identifies technology developments necessary to meet the telecommunications and information management system requirements for SEI. Technology requirements, technology needs and alternatives, the present level of technology readiness in each area, and a schedule for development are presented.

Ponchak, Denise S.↗
NASA NTRS1991

Radiation exposure of LDEF: Initial results

Initial results from Long Duration Exposure Facility (LDEF) include radiation detector measurements from four experiments; P0006, P0004, M0004, and A0015. The detectors were located on both the leading and trailing edges of the orbiter and also at the Earthside end. This allowed the directional dependence of the incoming radiation to be measured. Total absorbed doses from thermoluminescent detectors (TLDs) verified the predicted spatial east-west dose dependence of a factor of approx. 2.5, due to trapped proton anisotropy in the South Atlantic Anomaly (SAA). On the trailing edge of the orbiter, a range of doses from 664 to 291 rad were measured under nominal shielding of 0.42 to 8.45 g/sq cm. A second set of detectors near this locations results are also given. On the leading edge, doses of 258 to 210 rad were found under shielding of 1.25 to 2.48 g/sq cm. Initial charged particle LET (linear energy transfer) spectra, fluxes, doses, and dose equivalents, for LET in H2O greater than or = 5 keV/micron, were measured with plastic nuclear track detectors located in the four experiments. Also, preliminary data on low energy neutrons were obtained from detectors containing (6)LiF foils.

Benton, E. V.↗
NASA NTRS1991

Effect of initial delamination on Mode 1 and Mode 2 interlaminar fracture toughness and fatigue fracture threshold

Static and fatigue double-cantilever beam (DCB) and end-notch flexure (ENF) tests were conducted to determine the effect of the simulated initial delamination in interlaminar fracture toughness, G(sub c), and fatigue fracture threshold, G(sub th). Unidirectional, 24-ply specimens of S2/SP250 glass/epoxy were tested using Kapton inserts of four different thickness - 13, 25, 75, and 130 microns, at the midplane at one end, or with tension or shear precracks, to simulate an initial delamination. To determine G(sub c), the fatigue fracture threshold below which no delamination growth would occur in less than 1 x 10(exp 6) cycles, fatigue tests were conducted by cyclically loading specimens until delamination growth was detected. Consistent values of model 1 fracture toughness, G(sub Ic), were measured from DCB specimens with inserts of thickness 75 microns or thinner, or with shear precracks. The fatigue DCB tests gave similar values of G(sub Ith) for the 13, 25, and 75 microns specimens. Results for the shear precracked specimens were significantly lower that for specimens without precracks. Results for both the static and fatigue ENF tests showed that measured G(IIc) and G(IIth) values decreased with decreasing insert thickness, so that no limiting thickness could be determined. Results for specimens with inserts of 75 microns or thicker were significantly higher than the results for precracked specimens or specimens with 13 or 25 microns inserts.

Murri, Gretchen Bostaph↗
NASA NTRS1991

Research on diabatic initialization

The objective was to contribute to the improvement of the analyses of irrotational wind and moisture fields in the trophics through advancement in the technique of initialization by incorporating diabatic effects. Significant accomplishments made during the period May 1990 to April 1991 in the following areas are presented: (1) estimation of the uncertainty of daily synoptic analyses in the tropics; (2) normal modes of Laplace's tidal equations for zonal wavenumber zero; and (3) tropical initialization to ameliorate the spin-up problem of precipitation forecasts. The focus of current research and plans for next year are also presented.

Kasahara, Akira↗
NASA NTRS1990

Cryogenic propellant management architectures to support the Space Exploration Initiative

The initial results of a current study to develop fuel system architectures to support the lunar requirements of the Space Exploration Initiative (SEI) are reported. The study includes the development and assessment of propellant management facility concepts, supporting infrastructure, operations analysis, and identification of impact on current programs, including Space Station Freedom, Earth-to-Orbit vehicles, and the Space Transfer Vehicle. The cryogenic propellant management architectures are evaluated using criteria that have been defined to provide for minimum subjective assessment and effective data reliability.

Cady, E. C.↗
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

Technology needs of the Exploration Initiative

An overview of the U.S. Space Exploration Initiative (SEI) is presented. The two primary objectives of the initiative are a return to the moon to create a permanent lunar base and a human mission to Mars. Even though mission architectural concepts are not yet defined, previous studies indicate that the SEI will require developments in numerous areas, including advanced engines for space transportation, in-space assembly and construction to support permanent basing of exploration systems in space, and advanced surface operations capabilities including satisfactory levels of power and surface roving vehicles, and technologies to safely support human space operations of long duration. The process of mission definition has begun and it is shown that it is possible to identify a family of fundamental functional building blocks from which all SEI mission architectures will be constructed.

Aldrich, Arnold↗