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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 1,207 records · Page 67

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NASA NTRS1972

Pseudorandom noise for telemetry error rate measurement applications and limitations.

A pseudorandom noise (PRN) generator functional design has been developed which is superior to the commercially available instrument in usable bandwidth and in the closeness of fit to the gaussian probability distribution in the 'tails' of the curve. The principal disadvantage of PRN sources for bit error rate (BER) measurements is that the probability distribution is truncated in the tails. This truncation of the probability distribution results in a similar truncation of the BER curve - i.e., there is a minimum BER which can be measured, below which the only possible result is zero. The minimum nonzero BER actually computed with the PRN source developed was 0.00001 with a pseudorandom sequence of 131,071 bits. It is theoretically possible, with a longer sequence, to achieve a minimum BER of 0.000001 with the same design.

Hopkins, P. M.↗

NASA NTRS1973

Photography of a lithium vapor trail during the daytime.

Barium and lithium vapors were released from sounding rockets in the thermosphere and observed from aboard a jet aircraft at an altitude of 40,000 ft. The purpose of the releases was to demonstrate the feasibility of an all-weather technique for observing chemical releases and to evaluate methods of observing daytime releases. The selected flight plan of the aircraft allowed a series of observations of the trail from two different straight line paths. Data were recorded photographically. The reduction in sky brightness at the 40,000-ft altitude as compared to the ground allows the use of a filter with a 10-A bandwidth for trail photography in the daytime. These photographs verified the calculation of the usable angular field of the narrow-band filters. Photographs of a 45-min-old trail of lithium vapor were obtained up to 20 min after sunrise at the aircraft. It is concluded that now vapor trail observations may be made during the daytime without regard to weather and logistic restrictions.

Bedinger, J. F.↗

NASA NTRS1973

Experimental landings in a spoiler-equipped light aircraft.

This report presents the results of a flight test program to determine the effects on landings of wide variations in approach path angle and approach airspeed for different kinds of piloting technique. Over 400 landings were made at approach speeds from 60 to 120 mph and approach path angles from 3 to 18 deg. Several variations of pilot technique involving different operations of the throttle/spoiler control were investigated. It is shown that very large ranges of airspeed and approach path angle can be accommodated with rather moderate penalties in landing distance and difficulty. With the spoiler-equipped aircraft, the best approach speeds are considerably higher than would be usable without spoilers, and approach path angles can be used which are far beyond those normally possible without spoilers.

Seckel, E.↗

NASA NTRS1973

Algebraic decoding of block codes over a q-ary input, Q-ary output channel, Q greater than q.

Decoding algorithms designed for one output alphabet are shown to be effectively usable for channels with a different output alphabet. The described technique that makes this possible can be used in conjunction with an arbitrary distance measure between input and output vectors. Thus, Hamming distance, Lee distance, or a burst distance can be assumed. Examples are presented for each of these distances.

Wainberg, S.↗

NASA NTRS1973

Hydrogen evolution in nickel-water heat pipes.

A study was made of the evolution of hydrogen gas in nickel-water heat pipes for the purpose of investigating methods of accelerated life testing. The data were analyzed in terms of a phenomenological corrosion model of heat pipe degradation which incorporates corrosion and oxidation theory and contains parameters which can be determined by experiment. The gas was evolved with a linear time dependence and an exponential temperature dependence with an activation energy of 1.03 x 10 to the minus 19th joules. A flow-rate dependence of the gas evolution was found in the form of a threshold. The results were used to predict usable lifetimes of heat pipes operated at normal operating conditions from results taken under accelerated operating conditions.

Anderson, W. T.↗

NASA NTRS1973

Linear filtering of ballistic-entry-probe data for atmospheric reconstruction.

A Kalman-Schmidt filter is used to estimate atmospheric and trajectory parameters for entry into the Venusian atmosphere. A significantly improved version of the Landing Trajectory Reconstruction (LTR) computer program, used to obtain the estimates is described. Major improvements involve precision and linearity control of numerical differencing, corrected perturbation modeling, and incorporation of a refractivity model. Important results show that gyroscopic data are not usable with LTR, that atmospheric properties are generally well estimated for altitudes less than 100 km, and that the two LTR modes of operation are complementary in performance.

Sabin, M. L.↗

NASA NTRS1973

On the surface-to-bulk mode conversion of Rayleigh waves.

Surface-to-bulk wave conversion phenomena occurring at a discontinuity characterized by a surface contour deformation are shown to be usable as a means for tapping Rayleigh waves in a nonpiezoelectric solid. A boundary perturbation technique is used in the treatment of the mode conversion problem. A systematic procedure is presented for calculating not only the first-order scattered waves, which include the reflected surface wave and the converted bulk wave, but also the higher order terms.

Chang, C.-P.↗

NASA NTRS1973

Investigation of high temperature antennas for space shuttle

The design and development of high temperature antennas for the space shuttle orbiter are discussed. The antenna designs were based on three antenna types, an annular slot (L-Band), a linear slot (C-Band), and a horn (C-Band). The design approach was based on combining an RF window, which provides thermal protection, with an off-the-shelf antenna. Available antenna window materials were reviewed and compared, and the materials most compatible with the design requirements were selected. Two antenna window design approaches were considered: one employed a high temperature dielectric material and a low density insulation material, and the other an insulation material usable for the orbiter thermal protection system. Preliminary designs were formulated and integrated into the orbiter structure. Simple electrical models, with a series of window configurations, were constructed and tested. The results of tests and analyses for the final antenna system designs are given and show that high temperature antenna systems consisting of off-the-shelf antennas thermally protected by RF windows can be designed for the Space Shuttle Orbiter.

Kuhlman, E. A.↗

NASA NTRS1973

Monitoring the vernal advancement and retrogradation (green wave effect) of natural vegetation

The author has identified the following significant results. The Great Plains Corridor rangeland project utilizes natural vegetation systems as phenological indicators of seasonal development and climatic effects upon regional growth conditions. A method has been developed for quantitative measurement of vegetation conditions over broad regions using ERTS-1 MSS data. Radiance values recorded in ERTS-1 spectral bands 5 and 7, corrected for sun angle, are used to compute a band ratio parameter which is shown to be correlated with green biomass and vegetation moisture content. This report details the progress being made toward determining factors associated with the transformed vegetation index (TVI) and limitations on the method. During the first year of ERTS-1 operation (cycles 1-20), an average of 50% usable ERTS-1 data was obtained for the ten Great Plains Corridor test sites.

Rouse, J. W., Jr.↗

NASA NTRS1973

Liquid metal magnetohydrodynamics (LMMHD) technology transfer feasibility study. Volume 1: Summary

The potential application of liquid metal magnetohydrodynamics (LMMHD) to central station utility power generation through the period to 1990 is examined. Included are: (1) a description of LMMHD and a review of its development status, (2) LMMHD preliminary design for application to central station utility power generation, (3) evaluation of LMMHD in comparison with conventional and other advanced power generation systems and (4) a technology development plan. One of the major conclusions found is that the most economic and technically feasible application of LMMHD is a topping cycle to a steam plant, taking advantage of high temperatures available but not usable by the steam cycle.

Phen, R. L.↗

NASA NTRS1973

Finite element analysis of a composite material interface

A finite element model of a composite material interface is developed to study the influence of the interface on the thermal strain in the composite. A plane stress model is used with an axisymmetric model as a check. The interface thickness, thermal coefficient, modulus, Poisson's ratio and the percent of mineral in the composite are variables in the study. The results confirmed the usability of the finite element model in studying the polymer-mineral interface.

Murray, K. H.↗

NASA NTRS1973

The space shuttle payload planning working groups. Volume 1: Astronomy

The space astronomy missions to be accomplished by the space shuttle are discussed. The principal instrument is the Large Space Telescope optimized for the ultraviolet and visible regions of the spectrum, but usable also in the infrared. Two infrared telescopes are also proposed and their characteristics are described. Other instruments considered for the astronomical observations are: (1) a very wide angle ultraviolet camera, (2) a grazing incidence telescope, (3) Explorer-class free flyers to measure the cosmic microwave background, and (4) rocket-class instruments which can fly frequently on a variety of missions. The stability requirements of the space shuttle for accomplishing the astronomy mission are defined.

Source record↗

NASA NTRS1974

Quality of signatures

Three conclusions are drawn on the usability, inherent variations, and noise aspects of the spectral signatures processed from data collected by the Field Signature Acquisition System (FSAS). Conclusions are based on the spectral data collected from winter wheat of the 1972/73 season, grown at Texas A and M University, College Station, Texas.

Kan, E. P. F.↗

NASA NTRS1974

Operating characteristics of the Langley Mach 10 high Reynolds number helium tunnel

Operating characteristics of the Langley Mach 10 high Reynolds number helium tunnel are presented for stagnation pressures from 138 N/sq cm to 1655 N/sq cm. The characteristics include detailed Mach number surveys in the test section from which usable core size and regions of disturbed flow were determined, preliminary blockage test results, and maximum run time to be expected at various stagnation pressures. Important tunnel dimensions including details of the model mounting apparatus are given. Measurements show the variation in average core Mach number in the test section to be between 9.4 and 10 for the present range of test conditions. The core radius is from 23 cm to 31.5 cm, depending on stagnation pressure and axial location in the test section.

Watson, R. D.↗

NASA NTRS1973

System design of the Pioneer Venus spacecraft. Volume 11: Launch vehicle utilization

A summary of the spacecraft descriptions; the probe bus, large probe, small probe, and orbiter is presented. The highlights on the designs of the Atlas/Centaur spacecraft as compared to the corresponding Thor/Delta spacecraft designs are contained. A comparison is made of the two Atlas/Centaur spacecraft for reference. The major differences are the replacement of the probes of the forward end of the probe bus with the mechanically despun antenna of the orbiter and the replacement of the bicone antenna on the aft end with the orbit insertion motor. The cross sections of the large and small probes are compared. The major features of each probe are described. The Thor/Delta and Atlas/Centaur designs for the probe bus and orbiter are analyzed. The usable spacecraft mass for the Atlas/Centaur is roughly twice that for the Thor/Delta if the Type I trajectory is assumed. It is somewhat less for the Type II trajectory in the designated launch years. This additional mass capability leads to cost savings in many areas which are described.

Varga, R. J.↗

NASA NTRS1974

Utilizing ERTS imagery to detect plant diseases and nutrient deficiencies, soil types and soil moisture levels

The author has identified the following significant results. ERTS-1 imagery may be used to delineate soil associations. It does have the capacity to divide soils into groups such that their land use and management would be similar. It offers definite potential for making grass flood-plain, wetland, river shoreline, and land use change surveys. Production of volume strata and forest type from the two usable bands of ERTS-1 imagery were of questionable value. No imagery was received for evaluation during the time of year when maine dwarf mosaic virus and southern corn leaf blight were active.

Parks, W. L.↗

NASA NTRS1974

Remote profiling of lake ice thickness using a short pulse radar system aboard a C-47 aircraft

Design and operation of short pulse radar systems for use in ice thickness measurement are described. Two ice profiling systems were tested, an S system which used either random noise or continous wave modulation at 2.8 GHz and a less powerful C band system which operated at 6.0 GHz and did not have random noise modulation. Flight altitudes of 4,000 feet were used, but the S band system was usable at 7,000 feet allowing flights in poor weather conditions. A minimum ice thickness of four inches is required for measurement, while the thickest ice measured was 36 inches. System accuracy is plus or minus one inch.

Cooper, D. W.↗

NASA NTRS1974

Natural resource inventories and management applications in the Great Basin

ERTS-1 resolution capabilities and repetitive coverage have allowed the acquisition of several statewide inventories of natural resource features not previously completed or that could not be completed in any other way. Familiarity with landform, tone, pattern and other converging factors, along with multidate imagery, has been required. Nevada's vegetation has been mapped from ERTS-1. Dynamic characteristics of the landscape have been studied. Sequential ERTS-1 imagery has proved its usefulness for mapping vegetation, following vegetation phenology changes, monitoring changes in lakes and reservoirs (including water quality), determining changes in surface mining use, making fire fuel estimates and determining potential hazard, mapping the distribution of rain and snow events, making range readiness determinations, monitoring marshland management practices and other uses. Feasibility has been determined, but details of incorporating the data in management systems awaits further research and development. The need is to accurately define the steps necessary to extract required or usable information from ERTS imagery and fit it into on-going management programs.

Tueller, P. T.↗