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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Assessment of jets as acoustic shields by comparison of single- and multitube suppressor nozzle data

Recent 1/4 scale and engine size nozzle acoustic data, for both 37-tube and single nozzles, were used to test the jet-shielding principle. At low jet velocities the multitube nozzle total sound power approaches the equivalent of 37 single tubes (no shielding), while near-sonic and above, the small equivalent number of single tubes compares well with a geometric model of lateral radiation from only about a third of the circumference of the outer jets (nearly complete shielding). At high jet velocities, the geometric shielding hypothesis is in excellent agreement with acoustic data from which the downstream coalesced jet noise is excluded. Present results are compared with an existing correlation for single jets, and with previous publications on multijet shielding.

Gray, V. H.↗
NASA NTRS1973

Development of porcelain enamel passive thermal control coatings

A white porcelain enamel coating was developed for application to high temperature metallic alloy substrates on spacecraft. The coating consists of an optically opacifying zirconia pigment, a lithia-zirconia-silica frit, and an inorganic pigment dispersant. The coating is fired at 1000 to 1150 C to form the enamel. The coating has a solar absorptance of 0.22 and a total normal emittance of 0.82 for a 0.017 cm thick coating. The coating exhibits excellent adhesion, cleanability, and integrity and is thermal shock resistant to 900 C. Capability to coat large panels has been demonstrated by successful coating of 30 cm x 30 cm Hastelloy X alloy panels. Preliminary development of low temperature enamels for application to aluminum and titanium alloy substrates was initiated. It was determined that both leaded and leadless frits were feasible when applied with appropriate mill fluxes. Indications were that opacification could be achieved at firing temperatures below 540 C for extended periods of time.

Levin, H.↗
NASA NTRS1972

Interferometric observations of an artificial satellite.

Very-long-baseline interferometric observations of radio signals from the TACSAT synchronous satellite, even though extending over only 7 hours, have enabled an excellent orbit to be deduced. Precision in differential delay and delay-rate measurements reached 0.15 nanosecond and 0.05 picosecond per second, respectively. The results from this initial three-station experiment demonstrate the feasibility of using the method for accurate satellite tracking and for geodesy.

Preston, R. A.↗
NASA NTRS1972

Simultaneous measurements of radar reflectivity and refractive index spectra in clear air convection.

Simultaneous measurements of radar reflectivity and radio refractive index at several altitudes in clear air convection have been made. The experimental data were compared with the theoretical relationship which relates the reflectivity to the refractivity spectrum. The agreement between the measurements and the theory is excellent and shows that the radar returns in clear air are the result of, and can be quantitatively described as being from, fine-scale refractivity fluctuations due to turbulent mixing. Further, the data give strong support to the -5/3 spectral decay of the refractivity spectrum in the inertial subrange.

Konrad, T. G.↗
NASA NTRS1972

Analysis of volatile combustion products and a study of their toxicological effects.

An experimental program was conducted to study the thermochemical, flammability and toxicological characteristics of uncoated and coated polyisocyanurate foams. The coatings used were fluorinated copolymer and an intumescent material. Combustion and pyrolysis gases were analyzed by gas chromatography and mass spectrometry. The LD-50 and LD-100 tests were performed on Sprague-Dawley rats housed in an environmental chamber. The isocyanurate foam, fluorinated-copolymer-coated foam, and the intumescent-coated foam were found to have excellent flammability and insulation characteristics, although smoke development was substantial.

Seader, J. D.↗
NASA NTRS1972

A reliable all-silver front contact for silicon solar cells.

Methods have been found to apply an adherent and humidity resistant silver-only front contact to n on p silicon solar cells. The critical processing step was the removal of the diffused oxide layer. Humidity resistance is superior to present day commercial titanium-silver contacts and the electrical characteristics of the cells are excellent. Titanium, which is degraded by humidity and which is a source of heavy metal poisoning, has been eliminated from the contact.

Lamneck, J. H., Jr.↗
NASA NTRS1972

The ERTS wideband image communication system.

The ERTS payload includes a three camera return beam vidicon (RBV) television system and a four channel multispectral scanner system (MSS). The communications system described includes spacecraft wideband equipment plus unique payload processing equipment located at three NASA tracking stations. The RBV information, transmitted as analog FM with a baseband response of dc to 3.2 MHz, is telemetered, processed and recorded on a wideband video recorder. The MSS data, consisting of 24 analog sensor outputs, is digitized and encoded as 15 megabit per second PCM. The MSS data is then transmitted as analog FM, demultiplexed, and recorded on a 25 channel recorder. It is shown that bit error rate is an excellent indicator of MSS link performance while signal-to-noise ratio and distortion vs frequency adequately define RBV link performance.

Pandelides, J.↗
NASA NTRS1973

Periodic attitude control of a slowly spinning spacecraft.

A periodic attitude control system is presented which permits control of secular errors of a slowly spinning spacecraft operating in a high disturbance environment. Attitude errors of the spin-axis are detected by sun sensors (or rate gyros) and are controlled by a periodic control law which modulates external control torques generated by mass expulsion torquers. Attitude stability during the uncontrolled periods is obtained passively via the vehicle spin momentum. Equations of motion, a system block diagram, and design parameters are presented for a typical spacecraft application. Simulation results are included which demonstrate the feasibility of the novel control concept. Salient features of the periodic control approach are implementation simplicity, excellent response, and a propellant utilization efficiency greater than 75 percent.

Todosiev, E. P.↗
NASA NTRS1972

Flight evaluation of a quartz-fiberfrax heat shield.

The results of temperature and base heat flux measurements made on two heat-shield evaluation flights of six-solid-motor Delta boosters are reviewed. Curtains made of quartz cloth and Fiberfrax felt sandwiches formed the heat shield. A comparison is presented of the flight data to ground test results and to an analytical thermal model of the curtain material. In general, the results obtained have confirmed the excellent suitability of the proposed material as a heat shield for the application considered.

Greenwald, G. F.↗
NASA NTRS1972

High speed, high performance /Hg,Cd/Te photodiode detectors.

The current performance of high speed photodiode detectors for the 1 to 10 micron spectral region is discussed. The (Hg,Cd)Te photodiode configuration, detector properties, integration in laser receiver modules, and frequency response are considered for near infrared and far infrared wavelengths. The recent advances in (Hg,Cd)Te material and device development are indicated by the realization not only of exceptionally high speed detectors but of detectors that exhibit excellent detectivities. The performance improves substantially when the detector is cooled. This detector junction technology has been extended to other compositions of (Hg,Cd)Te for peak spectral responses at 5 and 10 micron.

Soderman, D. A.↗
NASA NTRS1972

Star sensor/mapper for the Small Astronomy Satellites.

As a requirement for the Small Astronomy Satellite-B (SAS-B), a star sensor was designed to provide satellite positional data to an accuracy of 3 arc minutes for satellite spin rates of 1/12 rpm and 1 rpm. The star sensor is required to detect stars having a +4 visual magnitude during the sunlit portion of the orbit. The spacecraft orientation can be anything achievable in its near equatorial 500-km orbit. The design of the star sensor resulted in an instrument which weighs 6.5 lbs., consumes 0.4 W and operates at spin rates ranging from 1/12 rpm to 3 rpm. The instrument design incorporates optical features providing excellent uniformity of response across the 5 by 10 deg field of view.

Schenkel, F. W.↗
NASA NTRS1973

Diffusion in a unidirectional filament reinforced metal composite.

A theoretical analysis has been developed to describe composition changes resulting from exposure of a unidirectional filament reinforced metal composite to an elevated temperature environment. The analysis was based on a simple superposition of finite-difference solutions of the diffusion equation, and was applicable to the case for which the filament and matrix metals comprised an isomorphous binary alloy system. The possibility of chemical reaction between filaments and matrix was excluded. Excellent agreement was obtained between calculated concentration profiles and results of quantitative electron microprobe analyses of nickel filament reinforced copper samples.

Herring, H. W.↗
NASA NTRS1972

Viscosity of atomic hydrogen.

New calculations of the viscosity of atomic hydrogen were carried out, and excellent agreement between these values and recent experimental results (Cheng and Blackshear, 1972) is pointed out. They made measurements of the viscosity of atomic hydrogen at four temperatures, using an iterative technique. Theoretical values for the transport properties of atomic hydrogen may be predicted reliably over a wide range of temperatures by use of Kolos and Wolniewicz potential energy functions (1965).

Allison, A. C.↗
NASA NTRS1973

Experimental study of shock-wave reflection from a thermally accommodating wall.

Shock-tube experiments have been conducted to study the nonequilibrium gas-surface interaction which occurs when a thick shock wave in argon reflects from a coplanar, heat-conducting wall. Fast-response instrumentation was used to monitor variations in temperature and normal stress on the surface of the shock-tube end wall during and immediately following reflection of the incident shock wave. The laboratory observations are compared with computer predictions obtained by Deiwert using the direct-simulation Monte Carlo method, and excellent agreement is obtained when a suitable average thermal accommodation coefficient is chosen for the wall surface.

Hanson, R. K.↗
NASA NTRS1973

Unsteady subsonic compressible flow around finite thickness wings.

A general formulation for the unsteady subsonic compressible potential flow around aircraft having arbitrary configurations is presented. An integral representation of the velocity potential is obtained. From this a linear integral equation relating the perturbation potential and its normal derivative (which is known from the boundary conditions) is derived. For the numerical solution of the integral equation, the surface of the aircraft is divided into small elements and the potential is assumed to be constant within each element. Numerical results are obtained for an oscillating finite-thickness wing and indicate good convergence and excellent agreement with existing lifting surface solutions.

Morino, L.↗
NASA NTRS1972

Recent materials compatibility studies in refractory metal-alkali metal systems for space power applications.

Advanced Rankine and other proposed space power systems utilize refractory metals in contact with both single-phase and two-phase alkali metals at elevated temperatures. A number of recent compatibility experiments are described which emphasize the excellent compatibility of refractory metals with the alkali metals, lithium, sodium, and potassium, under a variety of environmental conditions. The alkali metal compatibilities of tantalum-, columbium-, molybdenum-, and tungsten-base alloys are discussed.

Harrison, R. W.↗
NASA NTRS1973

Gravity field of Mars from Mariner 9 tracking data.

Further reduction of Doppler tracking data from Mariner 9 confirms our earlier conclusion that the gravity field of Mars is considerably rougher than the fields of either the earth or the moon. The largest positive gravity anomaly uncovered is in the Tharsis region which is also topographically high and geologically unusual. The value obtained for the inverse mass of Mars is in good agreement with prior determinations from Mariner fly by trajectories. The direction found for the rotational pole of Mars is in excellent agreement with Sinclair's recent value, determined from earth-based observations of Mars' satellites. Other important physical constants that have either been refined or confirmed by the Mariner 9 data include: (1) the dynamical flattening, (2) the maximum principal moment of inertia, and (3) the period of precession of Mars' pole.

Lorell, J.↗
NASA NTRS1972

Apollo lunar orbital science.

The Apollo 15 and 16 experiments are discussed. The formal scientific experiments conducted in lunar orbit are listed in an appendix. The gamma ray spectrometer performed a compositional survey of the upper 30 cm of the lunar surface by observing the gamma rays emitted during the radioactive decay of naturally occurring radioisotopes and their daughter products, and of the radioisotopes produced by cosmic ray bombardment of lunar surface materials. The results from the Apollo 15 X-ray spectrometer have shown excellent correlation between returned samples and gross lunar features. The various systems and experiments are described in detail.

Roberson, F. I.↗