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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 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Wave emissions from dc and modulated electron beams on STS 3

During the third Space Shuttle Columbia flight (STS 3) in March 1982, investigations were conducted to assess the electrical, electromagnetic, and plasma environment of the orbiter and to diagnose wave emissions and related plasma effects due to the injection of an electron beam into the surrounding ionosphere. Attention is given to wave emissions and related plasma processes which were stimulated by the first electron beam emissions from the Space Shuttle. The on-orbit measurements are compared to measurements made in a space simulation chamber. Instrumentation and operations are considered along with the plasma effects of beam emissions, wave emissions from dc beams, wave emissions from VLF-modulated beams, and wave emissions from ELF-modulated beams.

Shawhan, S. D.↗
NASA NTRS1984

Modulated beam injection from the Space Shuttle during magnetic conjunctions of STS 3 with the DE 1 satellite

An electron beam emitted from the Office of Space Sciences 1 pallet on STS 3 was pulsed with specially designed very low frequency (VLF) formats in an attempt to generate whistler mode waves. Modulated operations of the beam emitted by a fast pulse electron generator (FPEG) were initiated during times of magnetic conjunctions between STS 3 and the high-altitude DE 1 satellite equipped with broadband VLF receivers. Coordinated FPEG/VLF modulation and DE 1 wideband data acquisition were achieved in 12 different cases. No evidence of any waves generated by FPEG were detected on the DE 1 analog wideband data. However, it is shown that in all of the cases, either the STS 3 attitude was such that the emitted electrons struck the main body of the vehicle, or it was not possible for whistler mode waves to propagate from the STS 3 location up to the vicinity of the DE 1 satellite.

Inan, U. S.↗
NASA NTRS1984

Injection module thrust vector control

A three-axis controlled Injection Module propelled by a Star 48 solid rocket motor has been considered for use as a final 'kick' stage to supplement the Inertial Upper Stage in a proposed launch option for the Galileo and International Solar Polar missions. A flight control law for the Injection Module is developed. A position plus rate control law is considered, with integral, path guidance, and derived rate terms added for improved pointing accuracy and fuel efficiency. Selection of control gains is accomplished with the help of analytical limit cycle expressions and verified by computer simulation of the closed loop system. A computer simulation of the flight control system is built around a rigid spacecraft model with gyro dynamics and thruster delays included. Models for pitch/yaw/roll disturbance torques are included. Through simple gain changes the proposed flight control law is shown to accommodate the widely different mass properties of the Galileo and International Solar Polar spacecraft. Pointing accuracies of better than the desired 0.2 degrees are achieved.

Bell, C. E.↗
NASA NTRS1984

Solar modulation of cosmic ray electrons 1978-1983

The ISEE 3 spacecraft has provided over 4 years of continuous data from nearby interplanetary space. By using these data together with prelaunch calibration data and precise electron spectra from balloon flights in 1979 and 1982 at Thompson, Manitoba, Canada, the flux level of approximately 1 GeV cosmic ray electrons with 1 month time resolution is monitored. The step-like onset of modulation observed for positive particles in 1979 is also seen in electrons, confirming that the dominant modulation mechanism is not sensitive to the charge of the particle. Hysteresis effects observed in the previous solar maximum by Burger and Swanenburg (1973) are not reproduced at the present solar maximum. A return to the relatively higher electron/proton ratios of the 1960s is a strong possibility. Conclusions must be drawn with caution, however, since the overall time structure of the present solar maximum is significantly different from that of the previous one.

Evenson, P.↗
NASA NTRS1984

Method for calculating multidimensional electric fields in photovoltaic modules

A finite element method for evaluating the electrical isolation characteristics of photovoltaic modules was developed; its accuracy was verified by comparison with an exact solution for a geometry similar to that of solar cells. Tests on a square test coupon, employed in electrical isolation tests, and a group of disc-shaped solar cells illustrated the finite element method's usefulness in evaluating module encapsulation designs. Finite element models had to avoid adjacent large and small elements and elements with large aspect ratios, and the NASTRAN output had to be curve fitted to calculate the maximum field. Geometric limits were indicated: cells with very sharp edges, and cells much thinner or thicker than the dielectric pottant layer.

Kallis, J. M.↗
NASA NTRS1983

The NASA data systems standardization program - Radio frequency and modulation

The modifications being considered by the NASA-ESA Working Group (NEWG) for space-data-systems standardization to maximize the commonality of the NASA and ESA RF and modulation systems linking spaceborne scientific experiments with ground stations are summarized. The first phase of the NEWG project shows that the NASA MK-IVA Deep Space Network and Shuttle Interrogator (SI) systems in place or planned for 1985 are generally compatible with the ESA Network, but that communications involving the Tracking and Data Relay Satellite (TDRS) are incompatible due to its use of spread-spectrum modulation, pseudonoise ranging, multiple-access channels, and Mbit/s data rates. Topics under study for the post-1985 period include low-bit-rate capability for the ESA Network, an optional 8-kHz command subcarrier for the SI, fixing the spacecraft-transponder frequency-multiplication ratios for possible X-band uplinks or X-band nondeep-space downlinks, review of incompatible TDRS features, and development of the 32-GHz band.

Martin, W. L.↗
NASA NTRS1985

Bonding Solar-Cell Modules

Status of research program on chemical bonding for solar-cell arrays subject of 57-page report. Program aimed at identifying, developing, and validating weather-stable chemical bonding promoters. Materials key to ensuring long life in encapsulated photovoltaic modules for electric-power generation. To be cost-effective, modules must hold together for at least 20 years, reliably resisting delamination and separation of component materials

Coulter, D. R.↗
NASA NTRS1985

Intermediate load modules for test and evaluation: Flat-Plate Solar Array Project

Two versions of a 36 stainless steel solar module were built. The first version was built as a commercial module for marine applications and was purchased for evaluation by JPL. Design deficiencies were identified as a result of the evaluation. The second version was built and the improvements that resulted from design changes are described. Assembly problems, electrical performance, and qualification test results are provided.

Bower, M. J.↗
NASA NTRS1985

Nickel-hydrogen spacecraft module configurations study

The incorporation of nickel-hydrogen technology into spacecraft power system designs for low Earth orbit vehicles offers significant power system weight reductions by increasing the power storage watt-hour efficiency. Several possible module configurations exist for the power system. The module configurations were compared utilizing reliability, weight, volume and load capability as evaluation parameters.

Collins, W. B.↗
NASA NTRS1984

Flat-plate module efficiency versus cost tradeoffs

The Five Year Research Plan energy cost methodology and in depth analyses based on the extensive data that are relevant to PV systems are used to facilitate the accomplishment of the $0.15/kWh energy cost goal. An equation is given for the five year energy cost methodology. The allocation guidelines are designed to be consistent with flat solar array (FSA) milestones for module cost, module efficiency, and the programmatic goal for energy cost. They are research targets that appear to be achievable, given prior accomplishments and planned activities in the areas of low cost silicon purification, low cost sheet material, high efficiency cell processing, low cost, long life encapsulants, and automated fabrication method. Extensive sensitivity analysis work has been performed that shows that these guidelines represent an efficient way to meet the intent of the DOE program.

Aster, R. W.↗
NASA NTRS1984

Status of high-efficiency module design and fabrication

The fabrication of high efficiency solar energy conversion modules (13% efficiency at NOCT - Nominal Operating Cell Temperature) is discussed, with emphasis placed on reducing NOCT, since reduced operating temperature improves both efficiency and module lifetime.

Spitzer, M. B.↗
NASA NTRS1984

Photovoltaic module spread-of-flame testing

Photovoltaic modules used in solar energy conversion are tested for flammability. Class B burning brand tests were conducted with the following results: module glass shattered and hydrocarbon encapsulants ignited. Penetration of back surface material was the prime cause of failure. Materials with greater flame and heat resistance are under consideration to increase back surface integrity up to Class A burning brand standard. The most promising is stainless steel foil.

Sugimura, R. S.↗
NASA NTRS1985

Block 5 documentation and solar modules

Design and fabrication of Spire Corporation's Block 5 photovoltaic flat plate module is reviewed. These modules exhibited power of about 70 watts under standard test conditions. Results of performance and environmental testing are provided.

Source record↗
NASA NTRS1985

Drift and observations in cosmic-ray modulation, 1

It is illustrated that a relative simple drift model can, in contrast with no drift models, simultaneously fit proton and electron spectra observed in 1965-66 and 1977, using a single set of modulation parameters except for a change in the IMF polarity. This result is interpreted together with the observation of Evenson and Meyer that electrons are recovering more rapidly than protons after 1980, in contrast with what Burger and Swanenburg observed in 1968-72, as a charge sign dependent effect due to the occurrence of drift in cosmic ray modulation. The same set of parameters produces a shift in the phase and amplitude of the diurnal anisotropy vector, consistent with observations in 1969-71 and 1980-81.

Potgieter, M. S.↗
NASA NTRS1985

The dependence of solar modulation on the sign of the cosmic ray particle charge

The solar modulation of galactic cosmic ray helium and electrons at 1 AU, within the 600-1000 MV magnetic rigidity interval, are compared for the period from 1965 through 1984. The time-intensity variations during the two solar maxima around 1970 and 1981 show that after 1970 the helium intensity recovers earlier than that of the electrons, whereas after 1981 the electron intensity recovers earlier than that of helium. The flux ratio of helium to electrons (He/e) undergoes a major increases during the 1969-1971 period and a major decrease during 1979-83. These experimental results can be interpreted as due to a dependence of the solar modulation of galactic cosmic rays on the sign of the particle charge, possibly as a consequence of drifts due to gradients and curvatures in the interplanetary magnetic field. However, the comparison of the shapes of the intensity-time curves of helium and electrons in the period 1970-1981 does not support a major specific prediction of the drift model.

Garcia-Munoz, M.↗
NASA NTRS1985

Long-term modulation of cosmic rays during solar cycle 21

A preliminary result concerning the rigidity dependence of the longer-term solar cycle modulation is reported. The long-term modulation, using monthly mean intensities and referred to November 1977 as a normalizing level, appear to be in accordance with the exponent gamma = 1, provided only Brisbane and Hobart data are used. Darwin data do not conform to this pattern except perhaps during the early years of the cycle until about the end of 1980, since when the Darwin long-term intensity has been largely steady, apart from Forbush-type decreases and the as yet unidentified vector from the observed SI vector. The true SI vector of galactic origin can be obtained. The resultant vector has the amplitude of 0.031% and the phase of 2.3h. The present result seems to be consistent with those so far reported.

Fenton, A. G.↗