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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Goddard Space Flight Center Solar Array Missions, Requirements and Directions

The Goddard Space Flight Center (GSFC) develops and operates a wide variety of spacecraft for conducting NASA's communications, space science, and earth science missions. Some are "in house" spacecraft for which the GSFC builds the spacecraft and performs all solar array design, analysis, integration, and test. Others are "out of house" spacecraft for which an aerospace contractor builds the spacecraft and develops the solar array under direction from GSFC. The experience of developing flight solar arrays for numerous GSFC "in house" and "out of house" spacecraft has resulted in an understanding of solar array requirements for many different applications. This presentation will review those solar array requirements that are common to most GSFC spacecraft. Solar array technologies will be discussed that are currently under development and that could be useful to future GSFC spacecraft.

Gaddy, Edward↗
NASA NTRS2010

Concept, Design, and Prototyping of XSAS: A High Power Extendable Solar Array for CubeSat Applications

CubeSats have proven themselves as a reliable and cost-effective method to perform experiments in space, but they are highly constrained by their specifications and size. One such constraint is the average continuous power, about 5 W, which is available to the typical CubeSat. To improve this constraint, we have developed the eXtendable Solar Array System (XSAS), a deployable solar array prototype in a CubeSat package, which can provide an average 23 W of continuous power. The prototype served as a technology demonstrator for the high risk mechanisms needed to release, deploy, and control the solar array. Aside from this drastic power increase, it is in the integration of each mechanism, their application within the small CubeSat form-factor, and the inherent passive control benefit of the deployed geometry that make XSAS a novel design. In this paper, we discuss the requirements and design process for the XSAS system and mechanical prototype, and provide qualitative and quantitative results from numerical simulations and prototype tests. We also discuss future work, including an upcoming NASA zero-gravity flight campaign, to further improve on XSAS and prepare it for future launch opportunities.

Senatore, Patrick↗
NASA NTRS1978

Aperture and detector cavity considerations for wide and medium field-of-view radiometers

It is anticipated that comparison ground calibration radiometers for the Earth Radiation Budget Satellite System (ERBSS) may well incorporate a receiver cavity to facilitate the electrical substitution calibration capability. The radiometers were specifically developed for direct solar measurements and incorporate narrow fields of view with total included angles of not more than 15 degrees. Special cavity design characteristics are required to achieve the potential accuracy of this type of radiometer. Adequate conical cavity designs have been developed to assure the five reflections which an entering photon must experience before it is allowed to exit the radiometer. Attention is given to the proposed hemispherical aperture configuration, typical paths of unwanted incoming radiation, a resolution of a skew ray into axial components, and aspects of cavity design.

Babcock, R. A.↗
NASA NTRS1994

Low encounter speed comet COMA sample return missions

Comets, being considered the most primitive bodies in the solar system, command the highest priority among solar-system objects for studying solar nebula evolution and the evolution of life through biogenic elements and compounds. The study of comets, and more especially, of material from them, provides an understanding of the physical, chemical, and mineralogical processes operative in the formation and earliest development of the solar systems. These return samples will provide valuable information on comets and serve as a rosetta stone for the analytical studies conducted on interplanetary dust particles over the past two decades, and will provide much needed extraterrestrial samples for the planetary materials community since the Apollo program. Lander sample return missions require rather complex spacecraft, intricate operations, and costly propulsion systems. By contrast, it is possible to take a highly simplified approach for sample capture and return in the case of a comet. In the past, we have considered Earth free-return trajectory to the comet, in which passive collectors intercept dust and volatiles from the cometary coma. However, standard short period cometary free-return trajectories results in the comet to the spacecraft encounter speeds in the range of 10 km/s. At these speeds the kinetic energy of the capture process can render significant modification of dust structure, change of solid phase as well as the lost of volatiles components. This paper presents a class of new missions with trajectories with significant reduction of encounter speeds by incorporating gravity assists and deep space maneuvering. Low encounter speed cometary flyby sample return will enable a marked increase in the value of the return science. Acquiring thousands of samples from a known comet and thousands of images of a comet nucleus would be space firsts. Applying new approach in flight mechanics to generate a new class of low encounter speed cometary sample return trajectories opens new possibilities in science. A systematic search of trajectories for the first decade of the twenty-first century will be made. The target encounter speed is for less than 7 km/s to short period comets.

Tsou, P.↗
NASA NTRS2004

Solar Simulation

Simulation of the surface region and interior of the Sun's convection zone. The objective is to provide understanding of the tachocline at the base of the convection zone. of the differential rotation generated by global convective motions, and of supergranules that are observed on the solar surface. Two large-scale simulation codes are used, one for the global dynamics in spherical coordinates and another for the local surface events in Cartesian geometry. We work in close collaboration with the Helioseismic and Magnetic Imager instrument developers for the Solar Dynamics Observatory satellite. NASA Program: Living with a Star - Sun-Earth Connection.

Wray, Alan↗
NASA NTRS2015

Near-Earth Asteroid Scout

Near-Earth asteroids (NEAs) are easily accessible objects in Earth's vicinity. As NASA continues to refine its plans to possibly explore NEAs with humans, initial reconnaissance with comparatively inexpensive robotic precursors is necessary. Obtaining and analyzing relevant data about these bodies via robotic precursors before committing a crew to visit an NEA will significantly minimize crew and mission risk, as well as maximize exploration return potential. The NASA Marshall Space Flight Center (MSFC) and NASA Jet Propulsion Laboratory are jointly developing the Near-Earth Asteroid Scout (NEAS) utilizing a low-cost CubeSat platform in response to the current needs for affordable missions with exploration science value. The mission is enabled by the use of an 85-sq m solar sail being developed by MSFC (figs. 1 and 2).

Walden, Amy↗
NASA NTRS1973

A study of the compatibility of science instruments with the solar electric propulsion space vehicle

Electromagnetic interference and field-of-view constraints are identified as the areas of most concern to science on solar electric propulsion space vehicles. Several areas are indicated which more detailed data on the space vehicle environment are needed. In addition, possible means to attain or demonstrate science/space vehicle compatibility are recommended for further iteration between space vehicle design and science payload considerations. The space vehicle design developed by the solar electric propulsion system integration technology effort is used. Two payload sets for comet Encke missions (a slow flyby and a rendezvous), as well as several instruments which are not included in the two payload sets, are analyzed to determine requirements on the space vehicle imposed by the instruments in order to meet their objectives. Environmental requirements for the sets of instruments are developed and compared to both the SEPSIT design criteria and the environment as it is presently understood.

Parker, R. H.↗
NASA NTRS2017

NASA's Advanced Solar Sail Propulsion System for Low-Cost Deep Space Exploration and Science Missions that Use High Performance Rollable Composite Booms

Several low-cost solar sail technology demonstrator missions are under development in the United States. However, the mass saving derived benefits that composites can offer to such a mass critical spacecraft architecture have not been realized yet. This is due to the lack of suitable composite booms that can fit inside CubeSat platforms and ultimately be readily scalable to much larger sizes, where they can fully optimize their use. With this aim, a new effort focused at developing scalable rollable composite booms for solar sails and other deployable structures has begun. Seven meter booms used to deploy a 90 m2 class solar sail that can fit inside a 6U CubeSat have already been developed. The NASA road map to low-cost solar sail capability demonstration envisioned, consists of increasing the size of these composite booms to enable sailcrafts with a reflective area of up to 2000 m2 housed aboard small satellite platforms. This paper presents a solar sail system initially conceived to serve as a risk reduction alternative to Near Earth Asteroid (NEA) Scout's baseline design but that has recently been slightly redesigned and proposed for follow-on missions. The features of the booms and various deployment mechanisms for the booms and sail, as well as ground support equipment used during testing, are introduced. The results of structural analyses predict the performance of the system under microgravity conditions. Finally, the results of the functional and environmental testing campaign carried out are shown.

Fernandez, Juan M.↗
NASA NTRS1995

An extended structure-function model and its application to the analysis of solar wind intermittency

An extended structure-function model is developed by including the new effect in the p-model of Meneveau and Sreenivasan (1987a), i.e., that the averaged energy cascade rate changes with scale, a situation which has been found to prevail in non-fully-developed turbulence in the inner solar wind. This model is useful for the small-scale fluctuations in the inner heliosphere, where the turbulence is not fully developed and cannot be explained quantitatively by any of the previous intermittency turbulence models. With two model parameters, the intrinsic index of the energy spectrum, alpha and the fragmentation fraction p, the model can fit, for the first time, all the observed scaling exponents of the structure functions, which are calculated for time lags ranging from 81 seconds to 0.7 hours from the Helios solar wind data. From the cases we studied we can establish for p neither a clear radial evolution trend, nor a solar-wind-speed, or stream-structure dependence, or a systematic anisotropy for both the flow velocity and magnetic field component fluctuations. Generally, p has values between 0. 7 and 0.8. However, in some cases in low-speed wind p has somewhat higher values for the magnetic components, especially for the radial component. In high-speed wind, the inferred intrinsic spectral indices (alpha) of the velocity and magnetic field components are about equal, while the experimental spectral indices derived from the observed power spectra differ. The magnetic index is somewhat larger than the index of the velocity spectrum. For magnetic fluctuations in both high- and low-speed winds, the intrinsic exponent alpha has values which are near 1.5, while the observed spectral exponent has much higher values.

Tu, C.-Y.↗
NASA NTRS1989

Main sequence mass loss and the ages of stars

The potentially observable consequences of the pulsation/rotation-induced mass loss from main-sequence A and F stars proposed by Willson et al. (1987) are discussed, reviewing the results of recent investigations. Particular attention is given to (1) evidence for a deficiency in A stars and an excess of F and G stars, as predicted by the theory, (2) cluster HR diagrams and age estimates, and (3) modifications to standard models of solar-system evolution. It is pointed out that the time scales and mass-loss rates required to explain the observed properties of clusters and field stars in this theory are the same as those needed to account for the early development of the solar system.

Willson, L. A.↗
NASA NTRS1994

An integrated strategy for the planetary sciences: 1995 - 2010

In 1992, the National Research Council's Space Studies Board charged its Committee on Planetary and Lunar Exploration (COMPLEX) to: (1) summarize current understanding of the planets and the solar system; (2) pose the most significant scientific questions that remain; and (3) establish the priorities for scientific exploration of the planets for the period from 1995 to 2010. The broad scientific goals of solar system exploration include: (1) understanding how physical and chemical processes determine the major characteristics of the planets, and thereby help us to understand the operation of Earth; (2) learning about how planetary systems originate and evolve; (3) determining how life developed in the solar system, particularly on Earth, and in what ways life modifies planetary environments; and (4) discovering how relatively simple, basic laws of physics and chemistry can lead to the diverse phenomena observed in complex systems. COMPLEX maintains that the most useful new programs to emphasize in the period from 1995 to 2010 are detailed investigations of comets, Mars, and Jupiter and an intensive search for, and characterization of, extrasolar planets.

Source record↗
NASA NTRS1997

The JPL/NASA solar probe mission

The Solar Probe mission, developed under the JPL/NASA outer planets program, is described. The system's design, based on X-2000 technology, is presented. The purpose of the mission is to: understand the plasma processes that heat the corona and accelerate the fast and slow solar winds; determine the dynamics of interior convection and small scale magnetism in the polar regions; to measure the high-latitude solar magnetic fields on the solar surface and determine how they project outwards into the solar system.

Tsurutani, Bruce T.↗