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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Accreting neutron stars in highly compact binary systems and the nature of 3U 1626-67

We discuss the existence of pulsing X-ray sources that consist of neutron stars in highly compact binary systems (orbital periods not more than Od3), undergoing accretion from low-mass late-type dwarf or degenerate-dwarf companions. An appropriate mass transfer rate can be driven by the decay of the orbit due to gravitational radiation, a self-excited wind, and/or the evolution of the companion. Such a system may result from the evolution of a cataclysmic variable, wherein a degenerate dwarf collapses to form a neutron star after accreting sufficient mass to exceed the Chandrasekhar limit. We apply this model to the 7s7 X-ray pulsar 3U 1626-67, and demonstrate that it can explain the apparent lack of Doppler shifts in the X-ray pulsations from this source. The model may also account for other observed properties of the source, including (1) the apparent faintness and large ultraviolet excess of the optical counterpart, (2) the lack of X-ray eclipses, and (3) an approximately 1000 s quasi-periodic oscillation in the source intensity that was recently observed with the SAS 3 satellite.

Joss, P. C.↗
NASA NTRS1972

Manned space flight nuclear system safety. Volume 3: Reactor system preliminary nuclear safety analysis. Part 1: Reference Design Document (RDD)

The Reference Design Document, of the Preliminary Safety Analysis Report (PSAR) - Reactor System provides the basic design and operations data used in the nuclear safety analysis of the Rector Power Module as applied to a Space Base program. A description of the power module systems, facilities, launch vehicle and mission operations, as defined in NASA Phase A Space Base studies is included. Each of two Zirconium Hydride Reactor Brayton power modules provides 50 kWe for the nominal 50 man Space Base. The INT-21 is the prime launch vehicle. Resupply to the 500 km orbit over the ten year mission is provided by the Space Shuttle. At the end of the power module lifetime (nominally five years), a reactor disposal system is deployed for boost into a 990 km high altitude (long decay time) earth orbit.

Source record↗
NASA NTRS1989

Constraints on impact rates in the Pluto-Charon system and the population of the Kuiper comet belt

Impact rates in the Pluto-Charon system are dominated by comets from the proposed Kuiper Belt, 30 to 50 AU from the sun. Such collisions excite the eccentricity of Charon's orbit, which then decays due to tidal dissipation. Charon's eccentricity approaches a quasi-steady state, which can be used to constrain the total number and mass of comets in the Kuiper Belt. Unfortunately, the current upper limit on Charon's orbital eccentricity must be reduced by more than a factor of ten before useful constraints can be set.

Weissman, Paul R.↗
NASA NTRS2013

NanoSail - D Orbital and Attitude Dynamics

NanoSail-D unfurled January 20th, 2011 and successfully demonstrated the deployment and deorbit capability of a solar sail in low Earth orbit. The orbit was strongly perturbed by solar radiation pressure, aerodynamic drag, and oblate gravity which were modeled using STK HPOP. A comparison of the ballistic coefficient history to the orbit parameters exhibits a strong relationship between orbital lighting, the decay rate of the mean semi-major axis and mean eccentricity. A similar comparison of mean solar area using the STK HPOP solar radiation pressure model exhibits a strong correlation of solar radiation pressure to mean eccentricity and mean argument of perigee. NanoSail-D was not actively controlled and had no capability on-board for attitude or orbit determination. To estimate attitude dynamics we created a 3-DOF attitude dynamics simulation that incorporated highly realistic estimates of perturbing forces into NanoSail-D torque models. By comparing the results of this simulation to the orbital behavior and ground observations of NanoSail-D, we conclude that there is a coupling between the orbit and attitude dynamics as well as establish approximate limits on the location of the NanoSail-D solar center of pressure. Both of these observations contribute valuable data for future solar sail designs and missions.

Heaton, Andrew F.↗
NASA NTRS1972

On the semiannual change in exospheric temperature.

Discussion of some uncertainties about the semiannual density variations of the neutral atmosphere at heights above 100 km ascribed by Jacchia (1965), on the basis of long observations of the decay of satellite orbits, to changes in exosphere temperature, but later, because of some difficulties, attributed by Jacchia (1971) to semiannual density variations that may not be produced primarily by changes in temperature. Temperature values derived from ionosphere electron content data recorded since 1965 at several sites in New Zealand using the Faraday rotation of geostationary satellite signals and from their comparison with ionosonde measurements are shown to suggest that the semiannual variations represent primarily changes in temperature and only secondarily in density.

Titheridge, J. E.↗
NASA NTRS1979

A possible origin for the grooves of Phobos

A hypothesis that the age and distribution of grooves on the surface of Phobos may be explained by a hybrid origin due to varying tidal stresses induced after a large impact altered the satellite's rotation rate is presented. The theory that these grooves are surface manifestations of internal fractures induced by the decay of Phobos orbit is ruled out because this mechanism would require the grooves to be extremely young features, but their implied age is greater than 10 to the 9th power yr. The location and relationship of grooves to the largest crater, Stickney, indicate that they are related to the Stickney impact, but were formed shortly after that event with orientations determined by the shape of Phobos. If the impact destroyed the condition of synchronous rotation, the changing orientation of Phobos in the gravitational field of Mars would subject its interior to stresses, producing the systems of grooves.

Weidenschilling, S. J.↗
NASA NTRS1983

STS-2, -3, -4 Induced Environment Contamination Monitor (ICEM)

The second, third, and fourth space transportation system missions are described including the location of the IECM in the payload bay and the shuttle coordinate systems used. Measurement results from the three flights are given for each instrument with comparisons to original goals for preflight environment and induced environment contamination. These results include very low levels of molecular mass accumulation rates, absence of molecular films on optical samples, outgassing species above 50 amu undetectable generally low levels of on-orbit particulates, and decay rates for early mission water dump particulates. Results of exposure of several optical materials and coatings to atomic oxygen are also presented. From these results, it is concluded that the space shuttle met the established induced environment contamination goals.

Miller, E. R.↗
NASA NTRS1983

Nimbus 7 CZCS - Reduction of its radiometric sensitivity with time

Preliminary results are described for an effort to quantify the sensitivity decay of a radiometry sensor (the Coastal Zone Color Scanner or CZCS aboard Nimbus 7). The method used in the study is to (1) compute the water-leaving radiance for imagery acquired in regions where this radiance is known or can be independently estimated, and (2) adjust the sensor calibration to force agreement between the two radiances. Decay factors for orbit numbers from 0 to 20,000 are plotted, and surface and space measurements are compared for the Gulf Stream and the Northern Sargasso Sea at different seasons. The fact that a seasonal variability in the chlorophyll a concentration in the Sargasso Sea was found in the sensor analysis (apparently the first such satellite observation) increases confidence in the method.

Gordon, H. R.↗
NASA NTRS1985

Particle size, number, composition and velocity from solid rocket motors

The damage potentials to the space shuttle orbiter caused by the high velocity particles contained in the exhaust plume of an upper stage is discussed. In particular, the particle size distribution and composition, the velocity of the particles and the expected contribution from shuttle launched upper stages are addressed. Particle size estimates based on historical data are compapred with those derived from upper stage motor performance testing. The particle velocities as determined by the best available plume computational technique are presented. The shuttle is scheduled to launch approximately 135 upper-stages over its lifetime looking at the currently scheduled flights and averaging over a yearly basis yields the contribution of particulates from the uper-stages. On the average, 91,645 llbs of Al2O3 will be ejected on each launch. The analysis to determine how much of this 91,645 lbs will remain in orbit or the decay rate is yet to be accomplished.

Roberts, B. B.↗
NASA NTRS1985

Applicability of 100kWe-class of space reactor power systems to NASA manned space station missions

An assessment is made of a manned space station operating with sufficiently high power demands to require a multihundred kilowatt range electrical power system. The nuclear reactor is a competitor for supplying this power level. Load levels were selected at 150kWe and 300kWe. Interactions among the reactor electrical power system, the manned space station, the space transportation system, and the mission were evaluated. The reactor shield and the conversion equipment were assumed to be in different positions with respect to the station; on board, tethered, and on a free flyer platform. Mission analyses showed that the free flyer concept resulted in unacceptable costs and technical problems. The tethered reactor providing power to an electrolyzer for regenerative fuel cells on the space station, results in a minimum weight shield and can be designed to release the reactor power section so that it moves to a high altitude orbit where the decay period is at least 300 years. Placing the reactor on the station, on a structural boom is an attractive design, but heavier than the long tethered reactor design because of the shield weight for manned activity near the reactor.

Silverman, S. W.↗
NASA NTRS1986

Orbital-Lifetime Program

Orbital Lifetime Program (OL) analyzes long-term motion of Earthorbiting spacecraft at altitudes of up to 2,500 km. Models perturbations to orbit caused by solar-radiation pressure, atmospheric drag, and gravitational effects of Sun, Moon, and oblate Earth. Used to predict orbital lifetime and decay rate of satellites. OL written in FORTRAN 77.

Orr, L. H.↗
NASA NTRS1986

Density waves in the solar nebula - Differential Lindblad torque

The differential torque exerted by Lindblad resonances on a perturbing object embedded in a two-dimensional nonself-gravitating disk with density, pressure and sound speed gradients is quantified. First-order corrections are made to account for Keplerian rotation and the presence of the gradients. The total torque is calculated by summing over all resonances in the absence of local wave damping. When applied to the primordial solar nebula disk, the calculations show that disks that cool with increasing heliocentric distance will cause decay of the orbit of the perturbing object. Conditions in which the perturber will escape orbit delay are also described. The characteristic drift time will be no greater than the stochastic accretion time scales. Implications of the calculations for planetary formation are discussed.

Ward, W. R.↗
NASA NTRS1989

Gravitational radiation as a test of relativistic gravity

Gravitational radiation can be used to test theories of gravitation. When the waves are ultimately detected directly, their speed and polarization properties can be measured and compared with predictions of alternative theories. The multipole nature of gravitational radiation was already tested in the binary pulsar, where observations of the decay of the orbit verify the quadrupole formula for gravitational radiation damping of general relativity and put strong constraints on dipole gravitational radiation predicted by many alternative theories.

Will, Clifford M.↗
NASA NTRS1992

Long Duration Exposure Facility (LDEF) space environments overview

The Long Duration Exposure Facility (LDEF) was retrieved from Earth orbit in January 1990 after spending almost six years in space. It had flown in a near-circular orbit with an inclination of 28.5 degrees. Initially, the orbit altitude was approximately 257 nautical miles; however, when the LDEF was retrieved the orbit altitude had decayed to approximately 179 nautical miles. The LDEF was passively stabilized about three axes while in free flight, making it an ideal platform for exposing experiments which were measuring the environments of near-Earth space and investigating the long-term effects of these environments on spacecraft. A brief overview of the encountered environments that were of most interest to the LDEF investigators is presented.

Kinard, William H.↗
NASA NTRS1994

Double-core evolution. 5: Three-dimensional effects in the merger of a red giant with a dwarf companion

The evolution of the common envelope phase of a binary system consisting of a 4.67 solar mass red giant and a 0.94 solar mass dwarf is studied using smoothed particle hydrodynamics. We demonstrate that the three-dimensional effects associated with the gravitational tidal torques lead to a rapid decay of the orbit on timescales approximately less than 1 yr. The relative orbit of the two cores in the common envelope is initally eccentric and tends to circularize as the orbital separation of the two cores decreases. The angular momentum lost from the orbital motion is distributed throughout the common envelope, and the double core does not evolve to a state of co-rotation for the evolutionary time followed. The energy dissipated from the relative orbit and deposited in the common envelope results in the ejection of approximately 13% of the mass of the envelope. The mass is ejected in all directions, but there is a preference for mass ejection in the orbital plane of the binary system. For example, approximately 80% of the ejected mass lies within 30 deg of the binary orbital plane. Because gravitational forces are long range, most of the energy and angular momentum is imparted to a small fraction of the common envelope resulting in an efficiency of the mass ejection process of approximately 15%. The core of the red giant executes significant displacement with respect to the center of mass of the system and contributes nearly equally to the total energy dissipation rate during the latter phases of the evolution. The degree of departure from synchronism of the initial binary system can be an important property of the system which can affect the outcome of the common envelope phase.

Terman, James L.↗
NASA NTRS1997

NASA/JSC orbital debris models

The orbital debris models developed within the framework of the NASA Johnson Space Center's (JSC's) orbital debris program, are categorized as environment definition and risk assessment models. The EVOLVE, CHAIN and the orbital debris engineering model 1996 (ORDEM96) computer programs determine the past, present and future orbital particulate environment, while the BUMPER and debris assessment software (DAS) computer programs provide a means for evaluating the risks of specific space missions. These models are presented. To support these models and to conduct specialized analyses, NASA/JSC employs a range of auxiliary models, including explosion and collision satellite breakup models, hypervelocity impact ballistic limit models, orbit propagation and decay models, space traffic models and solid rocket motor effluent models.

Johnson, Nicholas↗
NASA NTRS2001

In Situ Measurements of Meteoric Ions

Extraterrestrial material is the source of metal ions in the Earth's atmosphere, Each year approx. 10(exp 8) kg of material is intercepted by the Earth. The origin of this material is predominantly solar orbiting interplanetary debris from comets or asteroids that crosses the Earth's orbit. It contains a very small amount of interstellar material. On occasion the Earth passes through enhanced amounts of debris associated with the orbit of a decaying comet. This leads to enhanced meteor shower displays for up to several days. The number flux of shower material is typically several times the average sporadic background influx of material. Meteoric material is some of the earliest material formed in the solar system. By studying the relative elemental abundances of atmospheric metal ions, information can be gained on the chemical composition of cometary debris and the chemical makeup of the early solar system. Using in situ sampling with rocket-borne ion mass spectrometers; there have been approximately 50 flights that made measurements of the metal ion abundances at attitudes between 80 and 130 km. It is this altitude range where incoming meteoric particles am ablated, the larger ones giving rise to visible meteor. displays. In several rocket measurements isotopic ratios of different atomic ion mass components and metal molecular ion concentrations have been determined and used to identify unambiguously the measured species and to investigate the processes controlling the metal ion distributions The composition of the Earth's ionosphere was first sampled by an ion mass spectrometer flown an a rocket in 1956. In 1958 a rocket-borne ion spectrometer identified, fbr the first time, a layer of metal ions near 95 km. These data were interpreted as evidence of an extraterrestrial rather than a terrestrial source. Istomin predicted: "It seems probable that with some improvement in the method that analysis of the ion composition in the E-region may be used for determining the chemical composition of those meteors which do not reach the ground. Particularly, we hope to get information about the composition difference between particles of different meteor showers and also sporadic and shower meteoroids". These visions categorized the aims of many subsequent rocket-borne ion mass spectrometer experiments in the lower ionosphere, Although the use such measurements to deduce the composition of different classes of meteoroids has not been successful, the past four decades of rocket observations have provided po%erful sets of data for advancing our understanding of meteor ablation, meteoric composition, metal neutral and ion chemistry as well as ionospheric dynamics.

Grebowsky, Joseph M.↗