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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Geodetic studies by laser ranging to satellites.

For three months in 1970, two Goddard Space Flight Center (GSFC) laser tracking systems were used to try to detect the motion of the pole of rotation of the earth. More than two hundred passes of the Beacon Explorer C spacecraft were observed as it passed between the two stations, and these data were used to determine the orbital inclination of the spacecraft. The analysis required the accurate determination of the relative positions of the two tracking stations and the identification of the perturbations to the spacecraft orbit, in particular, those due to the gravitational fields of the earth, sun, and moon and those caused by the solid-earth tides. The results to date indicate that the GSFC laser systems can determine interstation distances with a repeatability of about 25 cm and that a new value of the Love number k that represents the distortion of the earth's gravity field caused by the tidal deformation of the earth is 0.35 plus or minus 0.05.

Smith, D. E.↗
NASA NTRS1975

Problem of artificial gravity from the point of view of experimental physiology

Artificial gravity in spacecraft and orbital stations is considered as prophylactic method for preventing disorders under weightlessness conditions and for readaptation of astronauts to the gravity of earth. The creation of 0.28 to 0.31 g artificial gravity during weightlessness is adequate to orient the human body in space, to preserve movement coordination, as well as to maintain the necessary level of certain physiological indices. This range of artificial weightiness can be reached by various angular accelerations of the satellite rotation as a function of the radius or orientation.

Yuganov, Y. M.↗
NASA NTRS1978

Vestibular Function Research aboard Spacelab

NASA is planning to perform a series of Vestibular Function Research (VFR) investigations on the early STS missions to investigate those neurosensory and related physiological processes believed to be associated with the space flight nausea syndrome. The first flight is scheduled for the 1981 Spacelab III Mission in which four frog specimens, mounted on a frog tilting/centrifuge device, will be subjected to periodic acceleration stimuli and periods of artificial gravity. The vestibular nerve firing responses of each frog specimen will be monitored through implanted neutral bouyancy microelectrodes and transmitted to the ground for quick analysis during the flight. The experimentation will be directed at investigating: (1) adaptation to weightlessness; (2) response to acceleration stimuli; (3) response to artificial gravity (in a weightlessness environment) and (4) readaptation to earth's gravity upon return.

Mah, R. W.↗
NASA NTRS1991

Report of the panel on geopotential fields: Gravity field, section 8

The objective of the Geopotential Panel was to develop a program of data acquisition and model development for the Earth's gravity and magnetic fields that meet the basic science requirements of the solid Earth and ocean studies. Presented here are the requirements for gravity information and models through the end of the century, the present status of our knowledge, data acquisition techniques, and an outline of a program to meet the requirements.

Anderson, Allen Joel↗
NASA NTRS2010

A Transportable Gravity Gradiometer Based on Atom Interferometry

A transportable atom interferometer-based gravity gradiometer has been developed at JPL to carry out measurements of Earth's gravity field at ever finer spatial resolutions, and to facilitate high-resolution monitoring of temporal variations in the gravity field from ground- and flight-based platforms. Existing satellite-based gravity missions such as CHAMP and GRACE measure the gravity field via precise monitoring of the motion of the satellites; i.e. the satellites themselves function as test masses. JPL's quantum gravity gradiometer employs a quantum phase measurement technique, similar to that employed in atomic clocks, made possible by recent advances in laser cooling and manipulation of atoms. This measurement technique is based on atomwave interferometry, and individual laser-cooled atoms are used as drag-free test masses. The quantum gravity gradiometer employs two identical atom interferometers as precision accelerometers to measure the difference in gravitational acceleration between two points (Figure 1). By using the same lasers for the manipulation of atoms in both interferometers, the accelerometers have a common reference frame and non-inertial accelerations are effectively rejected as common mode noise in the differential measurement of the gravity gradient. As a result, the dual atom interferometer-based gravity gradiometer allows gravity measurements on a moving platform, while achieving the same long-term stability of the best atomic clocks. In the laboratory-based prototype (Figure 2), the cesium atoms used in each atom interferometer are initially collected and cooled in two separate magneto-optic traps (MOTs). Each MOT, consisting of three orthogonal pairs of counter-propagating laser beams centered on a quadrupole magnetic field, collects up to 10(exp 9) atoms. These atoms are then launched vertically as in an atom fountain by switching off the magnetic field and introducing a slight frequency shift between pairs of lasers to create a moving rest frame for the trapped atoms. While still in this moving-frame molasses, the laser frequencies are further detuned from the atomic resonance (while maintaining this relative frequency shift) to cool the atom cloud's temperature to 2 K or below, corresponding to an rms velocity of less than 2 cm/s. After launch, the cold atoms undergo further state and velocity selection to prepare for atom interferometry. The atom interferometers are then realized using laser-induced stimulated Raman transitions to perform the necessary manipulations of each atom, and the resulting interferometer phase is measured using laser-induced fluorescence for state-normalized detection. More than 20 laser beams with independent controls of frequency, phase, and intensity are required for this measurement sequence. This instrument can facilitate the study of Earth's gravitational field from surface and air vehicles, as well as from space by allowing gravity mapping from a low-cost, single spacecraft mission. In addition, the operation of atom interferometer-based instruments in space offers greater sensitivity than is possible in terrestrial instruments due to the much longer interrogation times available in the microgravity environment. A space-based quantum gravity gradiometer has the potential to achieve sensitivities similar to the GRACE mission at long spatial wavelengths, and will also have resolution similar to GOCE for measurement at shorter length scales.

Yu, Nan↗
NASA NTRS1979

System noise analysis of the dumbbell tethered satellite for gravity-gradient measurements

An analysis of the dumbbell gravity gradiometer concept for measuring short wavelength variations in the earth's gravity gradient is presented. Variations in the gradient are recorded by measuring tension variations in a vertically stabilized satellite consisting of heavy masses connected by a long wire or rod. Tension noise arises from the excitation of various mechanical oscillations of the system. The principal noise sources that were identified are fluctuations in atmospheric drag heating and drag force resulting from density variations and winds. Approximate analytical expressions are presented for the tension noise as a function of the system design parameters for various possible configurations. Computer simulations using numerical integration were performed to study the tension noise for several sample cases. Three designs consistent with Shuttle launch capabilities are discussed.

Colombo, G.↗
NASA NTRS1995

Engineering Support of Microgravity Life Science Research: Development of an Avian Development Facility

The Avian Development Facility (ADF) is designed to provide a 'window' for the study of embryogenesis in space. It allows researchers to determine and then to mitigate or nullify the forces of altered gravity upon embryos when leaving and re-entering the Earth's gravity. The ADF design will allow investigations to begin their incubation after their experiments have achieved orbit, and shut down the experiment and fix specimens before leaving orbit. In effect, the ADF makes every attempt to minimize launch and re-entry effects in order to isolate and preserve the effects of the experimental variable(s) of the space environment.

Vellinger, J.↗
NASA NTRS2002

Exploring Heart and Lung Function in Space: ARMS Experiments

The Advanced Respiratory Monitoring System (ARMS) is a suite of monitoring instruments and supplies used to study the heart, lungs, and metabolism. Many experiments sponsored by the European Space Agency (ESA) will be conducted using ARMS during STS-107. The near-weightless environment of space causes the body to undergo many physiological adaptations, and the regulation of blood pressure is no exception. Astronauts also experience a decrease in blood volume as an adaptation to microgravity. Reduced blood volume may not provide enough blood pressure to the head during entry or landing. As a result, astronauts often experience light-headedness, and sometimes even fainting, when they stand shortly after returning to Earth. To help regulate blood pressure and heart rate, baroreceptors, sensors located in artery walls in the neck and near the heart, control blood pressure by sending information to the brain and ensuring blood flow to organs. These mechanisms work properly in Earth's gravity but must adapt in the microgravity environment of space. However, upon return to Earth during entry and landing, the cardiovascular system must readjust itself to gravity, which can cause fluctuation in the control of blood pressure and heart rate. Although the system recovers in hours or days, these occurrences are not easily predicted or understood - a puzzle investigators will study with the ARMS equipment. In space, researchers can focus on aspects of the cardiovascular system normally masked by gravity. The STS-107 experiments using ARMS will provide data on how the heart and lungs function in space, as well as how the nervous system controls them. Exercise will also be combined with breath holding and straining (the Valsalva maneuver) to test how heart rate and blood pressure react to different stresses. This understanding will improve astronauts' cardiopulmonary function after return to Earth, and may well help Earthbound patients who experience similar effects after long-term bed rest.

Andre Kuipers↗
NASA NTRS1989

The GRADIO spaceborne gravity gradiometer: Development and accommodation

The European ARISTOTELES mission aims at the determination of the Earth's gravity field at short wavelength with a global coverage. Gravity gradient measurements will be achieved during six months by the GRADIO instrument onboard a dedicated satellite in a near dawn-dusk sun-synchronous orbit at an altitude of 200 km. The objective is an accuracy of better than 5 mgals for gravity anomalies, at ground level for blocks of 1 x 1 deg. According to present knowledge of the potential, the recovery of higher spherical harmonics (degree and order greater than 30) is of main importance. This leads to focus on the variations of the measured components T(sub ij) of the gravity gradient tensor, at frequencies greater than 5 x 10(exp -3) Hz. The resolution, required for the gradiometer is 10(exp -2) Eotvos (i.e., 10(exp -11)/s squared) with an averaging time of 4 s.

Bernard, A.↗
NASA NTRS2020

The Mitigating Effects of Artificial gravity on Microgravity

The effects of microgravity on the human body can be debilitating however, the use of artificial gravity has the potential to completely mitigate these effects. Developing an artificial gravity habitation spacecraft concept could have positive effects on the astronauts spending long durations in space. Researching the past and upcoming artificial gravity concepts was accomplished using resources provided by my mentors, i.e. NASA Technical Reports Server (NTRS), human research roadmap, and the Aerospace Research Central (ARC) in coordination with other academic sources and research papers. This research has been accomplished over a several week period that looks at past artificial gravity concepts and the implications of instituting them or new designs in the future. Also, the research examines how to improve future artificial gravity concepts by applying what we know about past designs and what we are creating today. The expected outcomes of artificial gravity are that the health risks imposed on astronauts due to not being in Earth’s gravity environment for long duration space missions will decrease. No other microgravity mitigation technique addresses neurological problems such as fluid shift and VIIP syndrome as they only address physical conditions with exercise and supplements Another outcome is that using artificial gravity should reduce the long-term health effects that happen after the astronauts return to Earth because they will not be exposed to microgravity for as long. The real outcomes should be similar, if not the same, as the expected outcomes mentioned above. This process of creating artificial gravity aboard spacecrafts has potential to create a plethora of positive outcomes. The research completed will contribute to NASA’s missions and goals because the information gathered directly relates to the goal of sending humans to Mars and beyond and the research looks at how to solve one of the major problems associated with achieving that goal soon: microgravity. This research will contribute to NASA’s mission of sending astronauts to Mars, with a lower risk assessment, because artificial gravity will potentially mitigate the health risks (VIIP syndrome) associated with long duration in space flight.

Elizabeth Anne Westfall↗
NASA NTRS2017

Overview of SPRITE: Saturn Probe Interior and aTmosphere Explorer Concept

The Saturn PRobe Interior and aTmosphere Explorer (SPRITE) mission concept targets high-priority Planetary Science Decadal Survey science objectives. This mission concept would deliver the SPRITE entry probe into the Saturn atmosphere to obtain in situ measurements of elemental abundances and isotopic ratios, which would help distinguish the role Saturn played in the solar system formation and co-evolution of other planets. An Atmospheric Structure Investigation sensor package on the entry probe would provide in situ measurements of the pressure/temperature and wind structure below the cloud-tops, and a Quadrupole Mass Spectrometer and Tunable Laser Spectrometer suite would determine the composition of Saturn’s atmosphere. The SPRITE mission concept described in this paper uses a solar-powered carrier-relay spacecraft to deliver the battery-powered entry probe to Saturn after a 10-year Venus-Earth-Earth gravity-assist trajectory, and then relays the probe data back to Earth during the carrier-relay spacecraft Saturn flyby. A high-heritage design approach is implemented for the flight elements to minimize technical risk and enable successful return of this high-value science data.

Cuddy, Cavan↗
NASA NTRS2000

A Lifetime of Geodesy and Geophysics: In Rememberence of Bill Kaula

In the early 1960's the secrets that knowledge of the Earth's gravity field would eventually reveal about the processes that govern our planet were yet to be appreciated. It was the beginning of a new science known as space geodesy, which arose at a time when most efforts were devoted to understanding how to extract precise measurements of Earth structure and motions from an orbiting spacecraft. Bill Kaula was central to that beginning and showed the way for many who were to follow, both in time and in the development of approaches most likely to yield results. Bill laid out the theory, analyzed the data, and argued strenuously for a spacecraft mission devoted to measuring gravity to make it all come true in the way he knew it really could. That mission, GRACE, was a long time coming and Bill would not see its final staging, but his influence in making it happen was everywhere. With time, the concepts for measuring the static gravity field of the Earth and terrestrial planets became well advanced, although not universally agreed upon, and certainly not by Bill, who was always eager to argue and challenge traditional methods and thinking. The extension of space geodetic techniques to the planets and the development of new techniques to measure time variations in gravity have recently brought geodesy even closer to the geophysical processes that Bill sought to understand. This presentation will contain a little geodesy, a little history, and a little reminiscing about the leader in our field.

Smith, David E.↗
NASA NTRS2004

Time-Variable Gravity: The Low-Degree Components and their Connections with Geophysical/Climatic Changes

The oblateness of the Earth's gravity field, J2, has long been observed to undergo a slight decrease due to post-glacial rebound of the mantle. Sometime around 1998 this trend reversed quite suddenly. This reversal persisted until 2001, at which point the atmosphere-corrected time series appears to have reversed yet again. Presently, the time series appears to be returning to the value that would nominally have been reached had the anomaly not occurred. This anomaly signifies a large interannual change in global mass distribution whose J2 effect overshadows that of the post-glacial rebound over such timescales. A number of possible causes have been considered, with oceanic mass redistribution as the leading candidate although other effects, such as glacial melting and core effects may be contributing.

Cox, Christopher M.↗
NASA NTRS1993

Gravity recovery analysis using GPS for STEP and a low-low satellite mission

Global Positioning System (GPS) receivers on low Earth orbiting satellites can provide three-dimensional global tracking with sub-decimeter orbit accuracy. The precise GPS data can additionally be used to refine the Earth's gravity field. Satellite Test of the Equivalence Principle (STEP) is a proposed European Space Agency mission which will carry a flight GPS receiver. Using a realistic scenario for processing 5 days of GPS data, a covariance analysis is performed to obtain the expected improvement in the gravity field. Additionally, a similar analysis is then repeated for two low Earth orbiting satellites, each equipped with GPS receivers and with precise ranging measurements between them.

Muellerschroen, Ronald J.↗
NASA NTRS2013

Hydrogen-Enhanced Lunar Oxygen Extraction and Storage Using Only Solar Power

The innovation consists of a thermodynamic system for extracting in situ oxygen vapor from lunar regolith using a solar photovoltaic power source in a reactor, a method for thermally insulating the reactor, a method for protecting the reactor internal components from oxidation by the extracted oxygen, a method for removing unwanted chemical species produced in the reactor from the oxygen vapor, a method for passively storing the oxygen, and a method for releasing high-purity oxygen from storage for lunar use. Lunar oxygen exists in various types of minerals, mostly silicates. The energy required to extract the oxygen from the minerals is 30 to 60 MJ/kg O. Using simple heating, the extraction rate depends on temperature. The minimum temperature is approximately 2,500 K, which is at the upper end of available oven temperatures. The oxygen is released from storage in a purified state, as needed, especially if for human consumption. This method extracts oxygen from regolith by treating the problem as a closed batch cycle system. The innovation works equally well in Earth or Lunar gravity fields, at low partial pressure of oxygen, and makes use of in situ regolith for system insulation. The innovation extracts oxygen from lunar regolith using a method similar to vacuum pyrolysis, but with hydrogen cover gas added stoichiometrically to react with the oxygen as it is produced by radiatively heating regolith to 2,500 K. The hydrogen flows over and through the heating element (HE), protecting it from released oxygen. The H2 O2 heat of reaction is regeneratively recovered to assist the heating process. Lunar regolith is loaded into a large-diameter, low-height pancake reactor powered by photovoltaic cells. The reactor lid contains a 2,500 K HE that radiates downward onto the regolith to heat it and extract oxygen, and is shielded above by a multi-layer tungsten radiation shield. Hydrogen cover gas percolates through the perforated tungsten shielding and HE, preventing oxidation of the shielding and HE, and reacting with the oxygen to form water vapor. The water vapor is filtered through solid regolith to remove unwanted extraction byproducts, and then condensed to a liquid state and stored at 300 to 325 K. Conversion to usable oxygen is achieved by pumping liquid water into a high-pressure electrolyzer, storing the gaseous oxygen at high pressure for use, and diverting the hydrogen back to the reactor or to storage. The results from this design effort show that this oxygen-generating concept can be developed in an efficient system with low specific mass. Advantages include use of regolith as an oxygen source, filter, and thermal insulator. The system can be tested in Earth gravity and can be expected to operate similarly in lunar gravity. The system is scalable, either by increasing the power level and output of a standard module, or by employing multiple modules.

Burton, rodney↗
NASA NTRS1985

Subduction dynamics: Constraints from gravity field observations

Satellite systems do the best job of resolving the long wavelength components of the Earth's gravity field. Over the oceans, satellite-borne radar altimeters such as SEASAT provide the best resolution observations of the intermediate wavelength components. Satellite observations of gravity contributed to the understanding of the dynamics of subduction. Large, long wavelength geoidal highs generally occur over subduction zones. These highs are attributed to the superposition of two effects of subduction: (1) the positive mass anomalies of subducting slabs themselves; and (2) the surface deformations such as the trenches convectively inducted by these slabs as they sink into the mantle. Models of this subduction process suggest that the mantle behaves as a nonNewtonian fluid, its effective viscosity increases significantly with depth, and that large positive mass anomalies may occur beneath the seismically defined Benioff zones.

Mcadoo, D. C.↗
NASA NTRS1983

Orbiting chains and rings

Two very different, highly flexible, space structures proposed during the last decade which involve analytical solution of certain partial differential equations are discussed. The first structure is an array, or hanging chain of aluminum beads which would serve as a convenient communicator if, under the influence of the Earth's gravity gradient, it assumes a local vertical orientation as it circles the Earth. Two passive schemes have been proposed for damping the rigid modes: twist the wire at the ends to provide non-zero moment of inertia about the vertical, thereby inducing relative motion of the two tips during rigid pitch or roll, and thus exercising a damper; and introduce weak lossy springs between the end sections and the main section; thereby providing linear coupling between the springs and all the in-plane (pitch) modes. The second structure is a complete ring of satellites cabled together at synchronous altitude. By a slight increase in altitude, the cable is in tension. This configuration is, however, unstable, and an active feedback control scheme is required to stabilize it. A possible scheme involves local cable length adjustment based on measurement of local altitude and shape variations and their rates.

Breakwell, J. V.↗