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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

On the determination and investigation of the terrestrial ionospheric refractive indices using GEOS-3/ATS-6 satellite-to-satellite tracking data

An analysis of the shortening and lengthening of the phase of satellite-to-satellite (SST) data that passed within 40-700 km above the earth surface during its ATS-6 to GEOS-3 to ATS-6 path resulted in refractivity vs height profiles. The SST Doppler data were used directly to adjust the GEOS-3 orbit. Perturbations from the moon, sun, and a 15th-order/degree earth gravity field were included in the orbit solution. This orbit was continued through the occulation period and a model ionosphere was estimated by a least-squares adjustment of the Chapman ionosphere parameters from the SST data residuals. The refractivity profile obtained by this model ionosphere was compared to a refractivity profile obtained by a direct integral inversion of the SST data residuals. Systematic differences between the two methods were caused by orbital errors, which propagated into the solution.

Liu, A. S.↗
NASA NTRS1978

On the determination and investigation of the terrestrial ionospheric refractive indices using GEOS-3/ATS-6 satellite-to-satellite tracking data

When the radio link between two satellites (GEOS-3/ATS-6) is intercepted by the earth's ionosphere and neutral atmosphere, a change in the Doppler frequency results. Travel through the atmosphere causes the Doppler phase to be advanced in the ionosphere's portion and retarded in the neutral portion of the atmosphere. Analysis of the shortening and lengthening of the phase of the Satellite-to-Satellite Tracking (SST) data that passed within 40-700 km above the earth's surface during its ATS-6 to GEOS-3 to ATS-6 path, caused by the atmosphere, results in refractivity versus height profiles. The SST Doppler data were used directly to adjust the GEOS-3 orbit. Perturbation from the Moon, Sun and a 15th order/degree earth gravity field were included in the orbit solution. This orbit was continued through the occultation period and a model ionosphere was estimated by a least-square adjustment of the Chapman ionosphere parameters from the SST data residuals. The refractivity profile obtained by this model ionosphere was compared to a refractivity profile obtained by a direct integral inversion of the SST data residuals. Systematic differences between the 2 methods were caused by orbital errors, which propagated into the solution. The SST data yielded refractive index profiles in a novel economical manner because no additional or special on-board equipment were required.

Liu, A. S.↗
NASA NTRS1978

Monitoring the state of the human airways by analysis of respiratory sound

A mechanism whereby sound is generated by the motion of vortices in the human lung is described. This mechanism is believed to be responsible for most of the sound which is generated both on inspiration and expiration in normal lungs. Mathematical expressions for the frequencies of sound generated, which depend only upon the axial flow velocity and diameters of the bronchi, are derived. This theory allows the location within the bronchial tree from which particular sounds emanate to be determined. Redistribution of pulmonary blood volume following transition from earth gravity to the weightless state probably alters the caliber of certain airways and doubtless alters sound transmission properties of the lung. We believe that these changes can be monitored effectively and non-invasively by spectral analysis of pulmonary sound.

Hardin, J. C.↗
NASA NTRS1979

The Saturn Orbiter Dual Probe mission concept

This paper presents the results of a mission design study for NASA of the next Saturn mission to follow Voyager. The Saturn Orbiter Dual Probe (SO2P) mission combines three spacecraft - a Saturn orbiter, a Saturn probe, and a Titan probe/lander - into a multipurpose Saturn exploration package. The mission is to conduct a survey from orbit around Saturn and to physically probe bodies in the Saturnian system, the first such mission to do so. The mission has many possible options including: combining solar electric propulsion with earth gravity assist, assembling of IUS stages in orbit, and aerocapture at Titan to insert into Saturn orbit.

Roberts, P. H., Jr.↗
NASA NTRS1980

Hypergravity and estrogen effects on avian anterior pituitary growth hormone and prolactin levels

Developing female chicks with fractured right radii were maintained for 14 d at either earth gravity (1 g) or a hypergravity state (2 g). The birds at 1 g were divided into groups which received daily injections of (1) saline, (2) 200 micrograms estrone, and (3) 400 micrograms estrone for 14 d. The 2-g birds were divided into three similarly treated groups. All 2-g birds showed significantly lower body weights than did 1-g birds. Anterior pituitary (AP) glands were excised and analyzed for growth hormone and prolactin content by analytical electrophoresis. The 1-g chicks receiving either dose of daily estrogen showed increased AP growth hormone levels, whereas hypergravity alone did not affect growth hormone content. Chicks exposed to daily estrogen and hypergravity displayed reduced growth hormone levels. AP prolactin levels were slightly increased by the lower daily estrogen dose in 1-g birds, but markedly reduced in birds exposed only to hypergravity. Doubly-treated chicks displayed normal prolactin levels. Reduced growth in 2-g birds might be due, in part, to reduced AP levels of prolactin and/or growth hormone.

Fiorindo, R. P.↗
NASA NTRS1982

Body composition data from the rat subjects of Cosmos 1129 experiment K-316

The effects of 18.5 days of weightlessness on the body composition of young, growing, male laboratory rats were examined. Three groups of 5 rats each were examined. It is indicated that exposure of young, growing, male rats to 18.5 days of weightlessness produces: (1) no effect on the quantity of fat stored by the body; (2) a slight reduction in the quantity of fat free tissue laid down by the body; (3) a small reduction in the fraction of water contained by the fat free body mass; (4) a similar reduction in the fraction of water contained by the fat free skin and fat free carcass; (5) a shift in relative distribution of the total body water from skin to viscera; (6) a diminution in the fraction of extracellular water contained by the fat free body; (7) no effect on the fraction of total skeletal musculature contained by the fat free body, as indicated by body creatine content; (8) a sizeable reduction in the fraction of bone mineral contained by the fat free body, as calculated from body calcium content. The nature of the physiological changes induced by unloading from Earth gravity in the mammalian organism are illustrated.

Pace, N.↗
NASA NTRS1981

Satellite services system analysis study. Volume 3A: Service equipment requirements, appendix

Spacecraft descriptions and mission sequences, mission and servicing operations functional analyses, servicing requirements, and servicing equipment are discussed for five reference satellites: the X-ray Timing Explorer, the Upper Atmospheric Research Satellite, the Advanced X-ray Astrophysics Facility, the Earth Gravity Field Survey Mission, and the Orbiting Astronomical Observatory.

Source record↗
NASA NTRS1981

Ore deposits in Africa and their relation to the underlying mantle

African magmatism is largely related to the tensional stress regimes of the crust which are induced by the hotter upwelling mantle rocks. These mantle rocks may provide emanating forces and thermal energy for the upward movements of primary ore bodies with fluid inclusions in the tensional stress regimes of the crust. In this paper, the Goddard Earth Gravity Model is used to calculate a detailed subcrustal stress system exerted by mantle convection under Africa. The resulting system is found to be correlated with the African metallogenic provinces. Recognition of the full spectrum of ore deposits in Africa that may be associated with the hotter upwelling mantle rocks has provided an independent evidence to support the hypothesis of mantle-derived heat source for ore deposits.

Liu, H.-S.↗
NASA NTRS1982

Galilean satellite mission concepts

Post-Galileo mission concepts considered possible for satellite-intensive investigations are presented, with consideration given to single and multiple target scenarios using orbiter and lander deployments. Candidate missions that satisfy the selected science objectives are identified, and specific scenario/target combinations which fall within performance constraints are chosen. The concepts are then developed into descriptive mission profiles. Also discussed are target encounter and deployment requirements, payload delivery, and operational considerations. Particular attention is given to Jupiter radiation effects and shielding requirements. A wide range of satellite-intensive missions is thought to be within the performance capabilities of earth-gravity-assisted ballistic trajectories and nuclear electric propulsion technology.

Soldner, J. K.↗
NASA NTRS1982

Limitations imposed by ionospheric turbulence on satellite-to-satellite Doppler measurement accuracy

For some time the possibility has been considered to perform an accurate survey from orbit of the earth gravity field by making use of low-low, satellite-to-satellite Doppler tracking with a radio link which operates in the frequency band in the range from 50 to 100 GHz. It is, therefore, of interest to discuss the upper bound in Doppler measurement accuracy imposed by the effects of ionospheric turbulence. The present investigation is concerned with the measurement error induced by ionospheric turbulence. The assumptin is made that the so-called ionospheric refractive 'bias' can be removed with one of the multifrequency methods of the current practice.

Grossi, M. D.↗
NASA NTRS1982

Aerospace gerontology

The relevancy of gerontology and geriatrics to the discipline of aerospace medicine is examined. It is noted that since the shuttle program gives the facility to fly passengers, including specially qualified older persons, it is essential to examine response to acceleration, weightlessness, and re-entry over the whole adult lifespan, not only its second quartile. The physiological responses of the older person to weightlessness and the return to Earth gravity are reviewed. The importance of the use of the weightless environment to solve critical problems in the fields of fundamental gerontology and geriatrics is also stressed.

Comfort, A.↗
NASA NTRS1983

A mobile work station concept for mechanically aided astronaut assembly of large space trusses

This report presents results of a series of truss assembly tests conducted to evaluate a mobile work station concept intended to mechanically assist astronaut manual assembly of erectable space trusses. The tests involved assembly of a tetrahedral truss beam by a pair of test subjects with and without pressure (space) suits, both in Earth gravity and in simulated zero gravity (neutral buoyancy in water). The beam was assembled from 38 identical graphite-epoxy nestable struts, 5.4 m in length with aluminum quick-attachment structural joints. Struts and joints were designed to closely simulate flight hardware. The assembled beam was approximately 16.5 m long and 4.5 m on each of the four sides of its diamond-shaped cross section. The results show that average in-space assembly rates of approximately 38 seconds per strut can be expected for struts of comparable size. This result is virtually independent of the overall size of the structure being assembled. The mobile work station concept would improve astronaut efficiency for on-orbit manual assembly of truss structures, and also this assembly-line method is highly competitive with other construction methods being considered for large space structures.

Heard, W. L., Jr.↗
NASA NTRS1983

Status of the geopotential

Satellite laser ranging, satellite altimetry, and improved measurements of surface gravitational anomalies have broadened the data base on intermediate and short wavelength regions of the earth gravity field. The global data set served to develop new geopotential models with a resolution in spherical harmonics out to degree 180. The resolution was made possible using Seasat altimetry data containing 56,761 values of 1 x 1 deg gravity anomalies. Satellite-to-satellite tracking techniques involving the Geos-3 and Apollo spacecraft data for the sea surface temperature have yielded accurate intermediate wavelength gravity variations which correlate well with residual depth anomalies. Oceanic gravity anomalies have been computed directly from satellite altimetry or through statistical estimation using oceanic geoid heights. The data sets for gravimetric geoids have been compared with altimetric surfaces to identify areas which were of interest for geophysical investigation. Future data sets could become available from a proposed satellite-to-satellite Doppler tracking system (Gravsat) launched by NASA.

Lerch, F. J.↗
NASA NTRS1983

On determining the large-scale ocean circulation from satellite altimetry

It is contended that a spherical harmonic expansion of the difference between the altimeter-derived mean sea surface and the geoid estimate should reveal the large-scale circulation of the ocean surface layer when the low-degree terms are examined. Methods based on this principle are proposed and partially demonstrated over the Pacific Ocean with the aid of the mean sea surface derived from the Seasat altimeter and the Goddard Earth Model 9 earth gravity model. The preliminary results reveal a well-defined clockwise gyre in the North Pacific and a much less well defined counterclockwise gyre in the South Pacific. When the dynamic topography thus obtained is compared with Wyrtki's (1975) dynamic topography derived from hydrographic data, the agreement is found to be within the limit of geoid uncertainties and satellite orbital errors.

Tai, C.-K.↗
NASA NTRS1984

Definitive orbit determination for the HEAO-2 spacecraft

Precise ephemerides for the High Energy Astronomy Observatory-2 (HEAO-2) were computed to assist in the Charles Stark Draper Laboratory development of an onboard orbit determination technique. Weighted least-squares, batch orbit solutions were calculated using a high-precision earth gravity model and an approximate model for intermittent spacecraft thrusting. With these improvements, orbit solution consistencies at the 50- to 100-meter level were attained using the Goddard Trajectory Determination System and NASA S-band tracking data.

Smith, R. L.↗
NASA NTRS1984

Search and rescue satellite (SARSAT) error analysis of the 406 MHz system

A computer simulation investigated conditions encountered by the SARSAT 406 MHz system. Three and four parameter emergency transmitter (ET) location solutions were determined. Latitude and longitude, a frequency bias, and in the four-parameters solutions, a linear frequency drift term were estimated. Earth gravity, frequency drift, and measurement noise are the major error contributors to the ET position. Time-tag ET height and velocity errors, although significant are not routinely present. In the four-parameter solutions the drift error is eliminated; however, the sensitivity to measurement noise increases. Using the four-parameter pass solutions, the 406 MHz oscillator specifications can be relaxed and still satisfy the 5 km positioning requirement. Since a linear oscillator drift is removed in the four-parameter solution, only the measurement noise over 10-15 min is important.

Yionoulis, S. M.↗
NASA NTRS1985

The O sub 2/H sub 2 propulsion module for planetary spacecraft injection energy augmentation

A propulsion module to augment the Centaur G-Prime and the Aerobraked OTV (AOTV) injection energy (C sub 3) was studied. The characteristics and performance of a variety of Earth-storable and cryogenic propulsion systems are presented. A pump-fed, cryogenic O2/H2 propulsion system enables the elimination of a three-year delta V Earth gravity assist (delta VEGA) maneuver for several planetary missions currently under consideration by the NASA. This trip time reduction can significantly reduce mission support costs, reduce spacecraft (S/C) life requirements and potentially increase the probability of mission success. This study also shows that an O2/H2 propulsion module, developed for Centaur C sub 3 augmentation can be used with a space-based AOTV in the return mode, allowing the reuse of the high-value AOTV while still delivering the required high-injection energy for direct planetary missions. The propulsion module performance was estimated for a space shuttle delivery capability to LEO of 65,000 lb sub m and 75,000 lb sub m. The required minimum thrust level to minimize gravity losses was also determined. For several currently planned NASA planetary missions, the Centaur G-Prime injection energy is augmented by a delta VEGA maneuver. For these missions, direct injection by the Centaur cannot provide a shorter trip time than the delta VEGA injection trip time.

Palaszewski, B. A.↗
NASA NTRS1986

Trajectory options for the Mariner Mark II Tempel 2 rendezvous mission

Recent schedule changes have motivated a reassessment of the mission options for the Mariner Mark II Comet Rendezvous Asteroid Flyby. A new baseline mission has been selected, which will launch in September 1992 and arrive at comet Tempel 2 in December 1996. The geometry of the comet's orbit imposes on the mission total delta-V requirements that can best be met by selection of a delta-V-EGA trajectory, during which an earth gravity assist is used to improve mission performance. There is considerable freedom in the choice of comet arrival date and asteroid flyby targets; associated with each potential asteroid flyby is a different penalty in terms of delta-V and comet arrival data. Analysis of the trajectory and the asteroid flyby options will continue throughout the early phases of the Project.

Stetson, D. S.↗