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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 NTRS2005

"Ames Research Center: Linking our Origins to our Future"

Our research traces a path from interstellar materials to inhabited worlds and beyond. We examine how protoplanetary disks evolve and form terrestrial planets, the evolutionary paths of habitable planets, and how external factors (e.g., orbital eccentricity) and internal factors (atmospheric circulation) affect habitability. We trace, spectroscopically and chemically, the evolution of organic molecules from the interstellar medium onto habitable bodies. We examine how membranes might form under prebiotic planetary conditions. We evolve proteins capable of sustaining early metabolism, such as synthesis of biopolymers and transport of ions across membranes. We estimate the frequency of finding a functional prebiotic protein that formed spontaneously. We characterize the formation of diagnostic microbial biosignatures in rock-hosted ecosystems in ophiolite springs as an analog for subsurface life within our solar system, and photosynthetic microbial mats as biota that could be detected on extrasolar planets. We develop quantitative models that simulate energy relationships, biogeochemical cycling, trace gas exchange, and biodiversity. We examine the effects of climate variability on a vegetation-rich biosphere over intermediate time scales, using South American ecosystems as a model. We address natural transport of life beyond its planet of origin, such as on a meteorite, where survivors must withstand radiation, desiccation, and time in transit. We fly organisms and ecosystems in low Earth orbit to test their resistance to space. The Ames E&PO program disseminates these themes to national- and international-scale audiences through partnerships with the California Academy of Sciences, Yellow stone National Park, New York Hall of Science, and several K-14 educational organizations.

DesMarais, David J.↗
NASA NTRS2000

Insolation and the Precession Index

Simple nonlinear climate models yield a precession index-like term in the temperature. Despite its importance in the geologic record, the precession index e sin omega, where e is the Earth's orbital eccentricity and omega is the Sun's perigee in the geocentric frame, is not present in the insolation at the top of the atmosphere. Hence there is no one-for-one mapping of 23,000 and 19,000 year periodicities from the insolation to the paleoclimate record; a nonlinear climate model is needed to produce these periods. Two such models, a grey body and an energy balance climate model with an added quadratic term, produce e sin omega terms in temperature. These terms, which without feedback mechanisms achieve extreme values of about plus or minus 0.48 K for the grey body and plus or minus 0.64 K for the energy balance model, simultaneously cool one hemisphere while they warm the other. Moreover, they produce long-term cooling in the northern hemisphere when the Sun's perigee is near northern solstice and long-term warming in the northern hemisphere when the perigee is near southern solstice. Thus this seemingly paradoxical mechanism works against the standard model which requires cool northern summers (Sun far from Earth in northern summer) to build up northern ice sheets, so that if the standard model is correct it may be more efficient than previously thought. Alternatively, the new mechanism could possibly be dominant and indicate southern hemisphere control of the northern ice sheets, wherein the southern oceans undergo a long-term cooling when the Sun is close to the Earth during southern summer. The cold water eventually flows north, cooling the northern hemisphere. This might explain why the northern oceans lag the southern ones when it comes to orbital forcing.

Rubincam, David Parry↗
NASA NTRS1963

A Passive Gravitational Attitude Control System for Satellites

It is shown how the gravity-gradient effect may be utilized to design a long-lived, earth-pointing satellite attitude control system which requires no fuel supplies, attitude sensors or active control equipment. This two-body system is provided with a magnetic hysteresis damper which effectively damps out oscillations (librations) about the local vertical. The long rods, which must be extended in space from coiled up metal tapes, provide the required large moments of inertia and possess adequate rigidity and sufficient strength to endure the rigors of the extension process. The system is compatible with the requirements of multiple satellite launchings from a single last-stage vehicle. Analysis indicates that the gravitational torques are sufficient to keep the disturbing effects of solar radiation pressure, residual magnetic dipole moments, orbit eccentricity, rod curvature, eddy currents, and meteorite impacts within tolerable limits. It is believed that the high-performance, earth-pointing system described and analyzed in this paper represents an essential step in the development of high-capacity communications satellites requiring long life.

GRAVITY↗
NASA NTRS1963

Simulation of atmospheric drag

To accurately simulate the trajectory of an artificial satellite or space probe, the deceleration from atmospheric drag must be considered. In addition to the Earth, there is evidence that Mars, Venus and Jupiter have sufficiently dense atmospheres to affect the motion of a space vehicle. This paper discusses some problems involved in simulating planetary atmospheres themselves, and the results of making certain simplifying assumptions. The object of this report is to come up with a recommendation for a method of simulating atmospheric drag representing a complexity commensurate with the state of the art. It should be noted that the mission of ·the vehicle has to be considered. There are three missions in which atmospheric drag could play an important part. The first mission is a low eccentricity orbit about the Earth or another planet. The second mission is a planetary re-entry and .the third is a flyby orbit of the space vehicle. The three cases will be referred to as the "orbiting'", "reentry" and "fly -by" cases.

COMPUTER SIMULATION↗
NASA NTRS1969

Continuous and discrete RAE structural models.

Three dimensional coupled flexural and attitude dynamics of libration-damped cruciform gravity gradient satellite, discussing effects of orbital eccentricity, solar radiation pressure, etc

Farrell, J. L.↗
NASA NTRS1970

Geology of Mars

Mars geology, discussing polar caps phenomena, diurnal variations, orbital eccentricity, seasonal meteorology, volcanism, erosion, etc

Tombaugh, C. W.↗
NASA NTRS1972

Direct observations of low-energy solar electrons associated with a type 3 solar radio burst

On 6 April 1971 a solar X-ray flare and a type 3 solar radio noise burst were observed with instrumentation on the eccentric-orbiting satellite IMP 6. The type 3 solar radio noise burst was detected down to a frequency of 31 kHz. A highly anisotropic packet of low-energy solar electron intensities arrived at the satellite approximately 6000 seconds after the onset of the solar flare. This packet of solar electron intensities was observed for 4200 seconds. Maximum differential intensities of the solar electrons were in the energy range of one to several keV. The frequency drift rate of the type 3 radio noise at frequencies below 178 kHz also indicated an average particle speed corresponding to that of a 3-keV electron. The simultaneous observations of these solar electron intensities and of the type 3 solar radio burst are presented, and their interrelationships are explored.

Frank, L. A.↗
NASA NTRS1972

Tethered body problems and relative motion orbit determination

Selected problems dealing with orbiting tethered body systems have been studied. In addition, a relative motion orbit determination program was developed. Results from these tasks are described and discussed. The expected tethered body motions were examined, analytically, to ascertain what influence would be played by the physical parameters of the tether, the gravity gradient and orbit eccentricity. After separating the motion modes these influences were determined; and, subsequently, the effects of oscillations and/or rotations, on tether force, were described. A study was undertaken, by examining tether motions, to see what type of control actions would be needed to accurately place a mass particle at a prescribed position relative to a main vehicle. Other applications for tethers were studied. Principally these were concerned with the producing of low-level gee forces by means of stabilized tether configurations; and, the initiation of free transfer trajectories from tether supported vehicle relative positions.

Eades, J. B., Jr.↗
NASA NTRS1972

Orientation and resonance locks for satellites in the elliptic orbit.

In order to achieve the maximum strength of higher resonance locks for satellites in the elliptic orbit, the condition of satellite orientation during the process of deployment is established. It is shown that for maximum strength locks the axis of the minimum moment of inertia of satellites should point toward the attracting body at plus or minus (5/8) pi and 0 values of the true anomaly f. This condition of deployment is applicable to all cases of resonance rotation regardless of the value of lock number k and orbit eccentricity e.

Liu, H.-S.↗
NASA NTRS1973

Double floating probe measurements on S3-A.

Model calculations are made to explain the behavior of the potential of a pair of symmetrical floating probes used for the measurement of dc electric fields inside the plasmapause on the S3-A satellite launched on Nov. 15, 1971, into an eccentric orbit. Data representing the behavior of three regions of the plasmapause on and around Dec. 17, 1971, are discussed. The behavior of the plasmapause is found to be generally similar to that determined by previous observations involving variable magnetic activity.

Maynard, N. C.↗
NASA NTRS1974

Trapped particle and solar proton radiation prediction for ISEE (IME): Mother-daughter mission

The charged particle fluxes incident on spacecrafts in very eccentric orbits were investigated in support of the International Sun-Earth Explorer (International Magnetospheric Explorer) For this purpose, two flightpaths were considered having identical inclinations but different perigee altitudes (240 and 1364 kilometers, respectively). Apogee altitude was approximately the same for both cases (about 22 earth radii). For each of the two perigee altitudes investigated, two nominal trajectories were generated, having identical orbital configurations but with their major axes rotated by 180 deg in the plane of orbit, which resulted in placing the initial apogee into into opposite hemispheres. This was done in order to determine the corresponding variation in the vehicle-encountered particle intensities. Estimates of average energetic solar proton fluxes are given for a one year mission duration at selected integranlenergies ranging from E 10 to E 100 MeV. Results are summarized and discussed.

Stassinopoulos, E. G.↗