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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Dynamics of carbon dioxide exchange of a wheat community grown in a semi-closed environment

A wheat (Triticum aestivum Yecora Rojo) community was grown in the semi-closed conditions of the NASA/KSC Biomass Production Chamber (BPC). Experiments were conducted to determine whole community carbon dioxide exchange rates as influenced by growth and development, carbon dioxide concentration, time within the photoperiod, irradiance, and temperature. Plants were grown at a population of about 1500 per sq meter using a 20 hour light/4 hour dark daily regime. Light was supplied by HPS vapor lamps and irradiance was maintained in the range of 590 to 675 mu mol per sq meter. The temperature regime was 20 C light/16 C dark and nutrients were supplied hydroponically as a thin film. Fractional interception of PPF by the community increased rapidly during growth reaching a maximum of 0.96, 24 days after planting. This time corresponded to canopy closure and maximum rates of net photosynthesis (NP). Net daily CO2 utilization rates were calculated to day 48 and a 4th order regression equation integrated to obtain total moles of CO2 fixed by the community. This procedure may be useful for monitoring and prediction of biomass yields in a closed ecology life support system (CELSS).

Corey, Kenneth A.↗
NASA NTRS1990

Review and statistical analysis of the ultrasonic velocity method for estimating the porosity fraction in polycrystalline materials

A review and statistical analysis of the ultrasonic velocity method for estimating the porosity fraction in polycrystalline materials is presented. Initially, a semi-empirical model is developed showing the origin of the linear relationship between ultrasonic velocity and porosity fraction. Then, from a compilation of data produced by many researchers, scatter plots of velocity versus percent porosity data are shown for Al2O3, MgO, porcelain-based ceramics, PZT, SiC, Si3N4, steel, tungsten, UO2,(U0.30Pu0.70)C, and YBa2Cu3O(7-x). Linear regression analysis produced predicted slope, intercept, correlation coefficient, level of significance, and confidence interval statistics for the data. Velocity values predicted from regression analysis for fully-dense materials are in good agreement with those calculated from elastic properties.

Roth, D. J.↗
NASA NTRS1986

NASA 60 GHz intersatellite communication link definition study. Baseline document

The overall system and component concepts for a 60 GHz intersatellite communications link system (ICLS) are described. The ICLS was designed to augment the capabilities of the current Tracking and Data Relay Satellite System (TDRSS), providing a data rate capacity large enough to accommodate the expected rates for user satellites (USAT's) in the post-1995 timeframe. The use of 60 GHz for the anticipated successor to TDRSS, the Tracking and Data Acquisition System (TDAS), was selected because of current technology development that will enable multigigibit data rates. Additionally, the attenuation of the earth's atmosphere at 60 GHz means that there is virtually no possibility of terrestrially generated interference (intentional or accidental) or terrestrially based intercept. The ICLS includes the following functional areas: (1) the ICLS payload package on the GEO TDAS satellite that communicates simultaneously with up to five LEO USAT's; (2) the payload package on the USAT that communicates with the TDAS satellite; and (3) the crosslink payload package on the TDAS satellite that communicates with another TDAS satellite. Two methods of data relay on-board the TDAS spacecraft were addressed. One is a complete baseband system (demod and remod) with a bi-directional 2 Gbps data stream; the other is a channelized system wherein some of the channels are baseband and others are merely frequency translated before re-transmission. Descriptions of the TDAS antenna, transmitter, receiver, and mechanical designs are presented.

Source record↗
NASA NTRS1989

Reasoning about software specifications - A case study

The launch intercept condition (LIC) problem was analyzed to better understand the complexity of the automated reasoning process and the nature and role of background knowledge. An extension to resolution-based logic processing systems, called constraint logic programming, is described. Consideration is also given to a knowledge-driven incremental reasoning architecture which integrates a generic constraint logic programming system with a knowledge base of the domain.

Wild, Chris↗
NASA NTRS1989

The cryogenic subsystem for the X-ray spectrometer on the Advanced X-Ray Astrophysics Facility (AXAF)

The X-ray Spectrometer (XRS) instrument on the Advanced X-ray Astrophysics Facility (AXAF) will use X-ray detectors that operate at 0.1 K. The detectors will be maintained at 0.1 K by an Adiabatic Demagnetization Refrigerator (ADR) that operates inside a liquid helium dewar. The ADR rejects approximately 2 mW of heat to the stored liquid helium. With this low instrument heat load, the liquid helium dewar will have a long lifetime if the parasitic heat load on the helium from the surrounding warm facility is minimized. Spaceborne helium dewars typically use up to 3 vapor cooled shields to intercept the parasitic heat load. The XRS will add mechanical coolers to provide additional cooling to the outer vapor cooled shield. The cryogenic system consists of an ADR, a liquid helium dewar, mechanical coolers, and a thermal strap to connect the coolers to the dewar. The lifetime of the stored cryogen is calculated to be up to 5 years. This cryogenic system is described, with particular attention given to the dewar, mechanical cooler, and ADR design, testing, and trade studies. A breadboard ADR is presently being fabricated and tested. The status of the construction and testing of this breadboard will be described.

Castles, Stephen H.↗
NASA NTRS1988

High-speed analog fiber optic links for satellite communication

Large-aperture phased array antennas operating at millimeter wave frequencies are designed for space-based communications and imaging. Array elements are comprised of active transmit/receive (T/R) modules which are linked to the central processing unit through a high-speed fiberoptic network. This paper demonstrates optical control of active modules for satellite communication at 24 GHz. An approach called T/R level data mixing, which utilizes fiberoptic transmission of a data signal to individual T/R modules to be upconverted by an optically synchronized local oscillator, is demonstrated at 24 GHz. A free-running HEMT oscillator, used as local oscillator at 24 GHz, is synchronized using indirect subharmonic optical injection locking over a locking range of 14 MHz. Results of data link performance over 500-1000 MHz is also reported in terms of gain-bandwidth, linearity and third-order intercept, sensitivity, and dynamic range.

Daryoush, A. S.↗
NASA NTRS1990

Canopy architecture measured with a laser

A laser based method was employed to measure and numerically describe the architecture of a corn canopy. Use of the method provides an interception coefficient for classes of vegetation in layers of the canopy viewed in various directions. Architectural data obtained for similar corn canopies but measured by differing methods are comparable to the results obtained using the laser based method. These results provide input data to mathematical models employed in remote sensing for describing the radiation environment in a plant canopy and predicting its reflectance.

Vanderbilt, Vern C.↗
NASA NTRS1990

U-Th-Pb systematics of the Estherville mesosiderite

Results are presented on a detailed U-Th-Pb systematics of the Estherville mososiderite, which was performed in a study involving stepwise leaching experiments. The Pb-Pb internal 'isochrons' for Estherville yielded ages of 4556 + or - 35 Ma, 4506 + or - 75 Ma, and 4422 + or - 50 Ma, indicating that the silicate fraction of the Estherville mesosiderite is very heterogeneous and was formed early in the solar system history. Results clearly identifies the Pb-Pb isochron as a mixing line. The U-Pb lower-intercept ages could be divided into two groups: (1) around 3 Ga, and likely related to the 3.6 Ga heating event, and (2) close to 0 Ma and to 62 Ma.

Brouxel, M.↗
NASA NTRS1990

PHL 1226 and IC 1746 - A QSO-galaxy pair without Ca II or Na I absorption

Spectroscopic observations of the QSO PHL 1226 show no absorption lines at the expected wavelengths of Ca II H and K and Na I D absorption at the redshift of the nearby galaxy IC 1746 (z = 0.0176). The line of sight to PHL 1226 intercepts IC 1746 near the galaxy major axis at a projected separation from the galaxy nucleus of 28/h50 kpc. The 3-sigma upper limits on equivalent width attained in the spectra are 110 mA for Ca II H or K and 90 mA for either of the Na I D lines. The probable Ca II K line reported by Bergeron et al. (1988) is not confirmed.

Junkkarinen, Vesa T.↗
NASA NTRS1989

Launch window expansion and trajectory correction strategies prior to the first lunar swingby

Double lunar swing-by (DLSB) orbits will be employed by 'Geotail' and other spacecraft in the International Solar Terrestrial Physics program in order to conduct observations in the geomagnetic tail and front field regions of the earth begining in 1992. For these missions, first swing-by dates are virtually fixed due to the dependency of the inertial frame apsis direction on them; in addition, the relative velocity magnitude to the moon is defined so that the DLSB condition will hold rigorously. These two conditions entail that the spacecraft intercept the moon on the prescribed dates. Several revolutions in intermediate transfer orbits are required prior to the first swing-by, in order to adjust flight time while maintaining the requisite lunar swing-by date.

Engel, Cheryl↗
NASA NTRS1989

The International Cometary Explorer comet encounter and earth-return trajectory

ICE experienced a successful encounter with Comet Giacobini-Zinner on September 11, 1985. The comet-intercept trajectory, earth-return trajectory, and two cases of a possible 2014 capture trajectory are presented. Also, the essential propulsive trajectory correction maneuvers and the projected August 10, 2014 lunar swingby maneuver are discussed. The targeting methodology used for designing the trajectories is also discussed.

Roberts, Craig E.↗
NASA NTRS1989

Image defects from surface and alignment errors in grazing incidence telescopes

The rigid body motions and low frequency surface errors of grazing incidence Wolter telescopes are studied. The analysis is based on surface error descriptors proposed by Paul Glenn. In his analysis, the alignment and surface errors are expressed in terms of Legendre-Fourier polynomials. Individual terms in the expression correspond to rigid body motions (decenter and tilt) and low spatial frequency surface errors of mirrors. With the help of the Legendre-Fourier polynomials and the geometry of grazing incidence telescopes, exact and approximated first order equations are derived in this paper for the components of the ray intercepts at the image plane. These equations are then used to calculate the sensitivities of Wolter type I and II telescopes for the rigid body motions and surface deformations. The rms spot diameters calculated from this theory and OSAC ray tracing code agree very well. This theory also provides a tool to predict how rigid body motions and surface errors of the mirrors compensate each other.

Saha, Timo T.↗
NASA NTRS1990

Optimal orbital rendezvous using high and low thrust

Optimal control theory is used to examine a specific class of spacecraft trajectory problems where high- and low-thrust propulsion systems are utilized. These problems assume a spacecraft is in an established orbit about a planet. It is desired to execute an intercept of a pre-determined position in space in a specified amount of time using an optimal high-thrust program. The spacecraft then returns to the original orbit station using the low-thrust propulsion system in an optimal fashion. A minimum fuel solution is sought using the linearized equations of motion, known as the CW equations, which simplify the necessary computations. Solutions are obtained for problems with a fixed final time. However, for the time-open case, the optimal solution is for the final time to be infinite. With a weighted function of the final time in the performance index, a limited range of optimal single impulse solutions for the time -open case can also be found.

Prussing, John E.↗
NASA NTRS1990

Antimatter applied for Earth protection from asteroid collision

An Earth protection system against asteroids and meteorites in colliding orbit is proposed. The system consists of detection and deorbiting systems. Analyses are given for the resolution of microwave optics, the detectability of radar, the orbital plan of intercepting operation, and the antimatter mass require for totally or partially blasting the asteroid. Antimatter of 1 kg is required for deorbiting an asteroid 200 m in diameter. An experimental simulation of antimatter cooling and storage is planned. The facility under construction is discussed.

Satori, Shin↗
NASA NTRS1991

Dust particles from comets and asteroids collected at the Earth's orbit: Parent-daughter relationships

The relative contributions of comets and asteroids to the reservoir of dust in the interplanetary medium is not well known. There are direct observations of dust released from comets and there is evidence to associate the IRAS dust bands with possible collisions of Asteroids in the main belt. It is believed that one may combine lab analysis of the physics and chemistry of captured particles with orbital data in order to identify comet and asteroid parent bodies. It is possible to use the collected orbits of the dust to connect with its source in two ways. One is to consider the long time orbit evolution of the dust under Poynting-Robertson drag. The other is to look at the prompt orbit change of dust from comets onto trajectories that intersect the earth's orbit. In order to characterize the orbits of dust particles evolved over a long period of time, a study of its orbital evolution was undertaken. Various parameters associated with these dust orbits as they cross the Earth's orbit were considered in order to see if one may discriminate between particles evolved from comets and asteroids. The method was to calculate by a numerical procedure the orbits of dust particles after they left their parent bodies. It appears that as the particles pass the Earth's orbit, asteroidal grains and cometary grains can be differentiated on the basis of their measured orbital eccentricities even after much planetary perturbation. Broad parent daughter associations can be made on this basis from measurement of their trajectories intercepted in earth orbit.

Jackson, A. A.↗
NASA NTRS1991

Distillation of H2O from hard-frozen Martian permafrost

The authors present a method for distillation of hard-frozen Martian permafrost. A cable-tool is drilled into hard frozem permafrost to a depth of 10 to 20 m. They calculate that a 10 m hole could be drilled in a few days. A 10 m shaft with a diameter equal to the bore is inserted into the hole, and a air tight tent-like structure is erected over the borehole. Photovoltaic cells mounted on the tent supply electrical energy that is dissipated in the shaft. Drilling power can be supplied by other sources. With 1000 watts, the shaft can be heated to near 350 K, producing relatively high temperatures in the vicinity of the borehole. Surrounding H2O is vaporized and diffuses up through the regolith. The authors calculate that a tent of a radius of no more than a few meters would intercept most of the H2O as it diffused to the surface. Calculations suggest that it would require perhaps 30 days to extract H2O from most of the volume drained by this technique. Assuming that the hard frozen regolith is no more than 10 percent ice, the author's calculate that that about 2890 kg of H2O could be extracted in 30 days. Since the nominal requirement for each crew member is about 5 kg/day, one such borehole might be expected to supply enough H2O to maintain a crew of 5 for perhaps 100 days. Additional engineering studies will be done to attempt to improve the capacity or efficiency of this method.

Zent, A. P.↗
NASA NTRS1990

Using Landsat to provide potato production estimates to Columbia Basin farmers and processors

A summary of project activities relative to the estimation of potato yields in the Columbia Basin is given. Oregon State University is using a two-pronged approach to yield estimation, one using simulation models and the other using purely empirical models. The simulation modeling approach has used satellite observations to determine key dates in the development of the crop for each field identified as potatoes. In particular, these include planting dates, emergence dates, and harvest dates. These critical dates are fed into simulation models of crop growth and development to derive yield forecasts. Two empirical modeling approaches are illustrated. One relates tuber yield to estimates of cumulative intercepted solar radiation; the other relates tuber yield to the integral under the GVI curve.

Source record↗
NASA NTRS1991

Intracloud development of lightning strikes to aircraft

The analysis of airborne electromagnetic records of seven lightning strikes to the FAA CV-580 instrumented airplane during the 1987 field campaign was aimed at revealing and interpreting processes taken place during the intracloud propagation of lighting strikes initiated on or intercepted by the airplane. It is shown that intracloud development of the strike may consist of recoil streamers, dart leader/return stroke sequences, and the secondary initiations of new discharges. These processes, with their high current pulse amplitudes, may present greater threat to aircraft than current pulses during strike initiation. The latter are presently considered by the technical community to be the primary lightning threat to aircraft.

Mazur, Vladislav↗