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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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Generator can produce sinusoidal pressures at frequencies from 300 to 5000 Hz and peak-to-peak amplitudes up to 5.6 lbs/sq in. Amplitude and phase-angle measurements made at various frequencies are compared with measurements from a piezoelectric transducer mounted flush with the resonant tube wall.
Monolithic structure, consisting of fused quartz fabricated solar sensor and autocollimator, measures angle between reference surface on spacecraft and solar vector. Device compensates for errors caused by changes in the alignment of its mountings or component parts. Integrated concept is advantageous whenever sensor mounting errors constitute problems.
The development of a digital solar aspect sensor with a resolution of approximately 14 arc-seconds is discussed. An interpolation technique was used to generate the fine angle measurements. The sensor and its mode of operation are described. The electronic and mechanical design of the sensor were completed, and two flight units, one for the OAO 4 and the other for determining the attitude of a spinning spacecraft, are being fabricated.
Two new methods for navigation on the land are reported. Both methods make use of landmarks which are in sight but whose positions are not known. Only angle measurements are needed. Although the methods were intended for guiding a Lunar Roving Vehicle as it travels on the lunar surface, they may also find applications on other planets as well as on earth. Besides the mathematical details, two examples are also included to demonstrate the correctness of the method.
A self phased array was developed for propagation measurements on an earth-space path. The 11.7 GHz CTS beacon was used as the signal source. The self phased array was used to measure angle of arrival as well as attenuation and scintillation statistics. The performance of the array is described, and sample data are presented. The tracking capability of the self phased array was also studied. This technique permits fully electronic, nonmechanical satellite tracking, thus simplifying unmanned operation and eliminating severe weather tracking constraints.
The refraction angle and amplitude changes associated with sound transmission through a circular, open-jet shear layer were studied in a 0.91 m diameter open jet acoustic research tunnel. Free stream Mach number was varied from 0.1 to 0.4. Good agreement between refraction angle correction theory and experiment was obtained over the test Mach number, frequency and angle measurement range for all on-axis acoustic source locations. For off-axis source positions, good agreement was obtained at a source-to-shear layer separation distance greater than the jet radius. Measureable differences between theory and experiment occurred at a source-to-shear layer separation distance less than one jet radius. A shear layer turbulence scattering experiment was conducted at 90 deg to the open jet axis for the same free stream Mach numbers and axial source locations used in the refraction study. Significant discrete tone spectrum broadening and tone amplitude changes were observed at open jet Mach numbers above 0.2 and at acoustic source frequencies greater than 5 kHz. More severe turbulence scattering was observed for downstream source locations.
This paper extends the analysis of attitude determination accuracy introduced at the 1975 American Astronautical Society/American Institute of Aeronautics and Astronautics (AAS/AIAA) Astrodynamics Conference. It contains more generalized expressions, new geometrical relations, and additional applications. A complete set of attitude accuracy equations for both arc-length (portion of a great circle) and rotation-angle (dihedral angle) measurements are presented. These expressions can then be applied to determine the geometrical conditions under which a specified accuracy can be achieved by using either the attitude or a selected reference-vector direction as the independent variable. Representative applications to attitude determination accuracy studies and launch window analyses are discussed. The clear physical interpretation and straightforward graphical procedures greatly simplify mission analysis, maneuver planning, hardware configuration studies, and interpretation of results.
Results are discussed for X-ray scans of the Perseus cluster with the SAS 3 slat detectors. Counting rates in two broadband channels (1.5 to 5.5 keV and 5.5 to 15.5 keV) are compared as a function of the instrument scan angle measured from the center of emission, and it is found that the emission in the higher energy range is broader in extent. Tests for a systematic energy-dependent error in the background demonstrate that the discovered energy dependence of the Perseus cluster emission is valid. Iron line emission is determined by two methods, various models are fitted to the data, and the total cluster emission in the two energy ranges is computed. The iron line emission is determined to be 0.003 photon/sq cm per sec. It is concluded that the diffuse emission increases in the range from 1.5 to 15.5 keV within the bounds of a model involving a point source with a radius not exceeding about 3 arcmin plus a diffuse source.
As the Apollo program proceeded, redundancy became a requirement for all crew safety functions. One critical period of the Apollo missions was the rendezvous of the Command Module and the Lunar Module. The rendezvous radar provided the critical range, range rate, and angle measurements necessary to complete the rendezvous. Use of a redundant radar for backup was out of the question because of its 80-lb weight. It was, however, found that the voice radios could be adapted to perform the ranging function. Slight modifications of the VHF voice radios and the addition of a ranging interrogator and transponder at a weight of less than 10 lbs total would provide an accuracy of 100-ft rms at several hundred miles. The Apollo VHF ranging system demonstrated that it is feasible to achieve highly accurate range measurements with conventional voice radios.
Two-axis goniometer accurately measures movements of fingers about knuckle joints, diagnosing hands structurally changed by rheumatoid arthritis. Instrument measures lateral movement which is small in normal knuckles but increased in diseased joints. Goniometer is two connected protractors that simultaneously measure angles in perpindicular planes. Dials are offset to clear bony protuberances; extension and offset adjustments span any hand size.
The POLAR 5 rocket experiment carried an electron accelerator on a 'daughter' payload which injected a 0.1 A beam of 10 keV electrons in a pulsed mode every 410 ms. With spin and precession, injections were made over a wide range of pitch angles. Measurements from a double probe electric field instrument and from particle detectors on the 'mother' payload and from a crude RPA on the 'daughter' payload are interpreted to indicate that the 'daughter' charges to a potential between several hundred volts and 1 kV. The neutralizing return current to the 'daughter' is shown to be asymmetrically distributed with the majority being collected from the direction of the beam. The additional electrons necessary to neutralize the daughter are thought to be produced and heated through beam-plasma interactions postulated by Maehlum et al. (1980) and Grandal et al. (1980) to explain the particle and optical measurements. Significant electric fields emanating from the charged 'daughter' and the beam are seen at distances exceeding 100 m at the 'mother' payload.
The various definitions of albedo used in planetary astronomy are reviewed. In particular, the Bond albedo, which refers only to the reflected and refracted components, is not applicable to small particles or highly irregular particles, where diffraction is not restricted to a well-defined lobe at small scattering angles. Measured scattering functions for irregular particles are presented in a normalized form and are applied to the case of zodiacal light.
X ray photoelectron spectroscopy and contact angle measurements on graphite fiber composites pretreated in a number of different ways including mechanical, chemical, and light irradiation were analyzed. Data acquired on surface contamination as a result of fabrication techniques provides answers to the strength and durability of adhesively bonded composites. These techniques were shown to provide valuable information on surface analysis of pretreated composites prior to adhesive bonding and following lap shear fracture.
The effects of high energy radiation on the mechanical properties and on the molecular and structural properties of graphite fiber reinforced composites were assessed so that the durability of such composites in space applications could be predicted. Investigative techniques including ESR and infrared spectroscopy, ESCA, contact angle measurements, and dynamic and static mechanical testing (3-point bending and interlaminar shear) were employed. The results using these different techniques are individually described, and the implications of the data are discussed. The proposed plan of work for the next fiscal year is outlined.
The aircraft industry has long been concerned with the increase of drag on airplanes due to fouling of the wings by insects. The present research studied the effects of surface energy and surface roughness on the phenomenon of insect sticking. Aluminum plates of different roughnesses were coated with thin films of polymers with varying surface energies. The coated plates were attached to a custom jig and mounted on top of an automobile for insect collection. Contact angle measurements, X-ray photoelectron spectroscopy and specular reflectance infrared spectroscopy were used to characterize the surface before and after the insect impact experiments. Scanning electron microscopy showed the topography of insect residues on the exposed plates. Moments were calculated in order to find a correlation between the parameters studied and the amount of bugs collected on the plates. An effect of surface energy on the sticking of insect residues was demonstrated.
Phase separation of polymer systems in microgravity is studied in aircraft flights to prepare shuttle experiments. Short duration (20 sec) experiments demonstrate that phase separation proceeds rapidly in low gravity despite appreciable phase viscosities and low liquid interfacial tensions (i.e., 50 cP, 10 micro N/m). Ostwald ripening does not appear to be a satisfactory model for the phase separation mechanism. Polymer coated surfaces are evaluated as a means to localize phases separated in low gravity. Contact angle measurements demonstrate that covalently coupling dextran or PEG to glass drastically alters the 1-g wall wetting behavior of the phases in dextran-PEG two phase systems.
A laser angle measurement system was designed and fabricated for NASA Langley Research Center. The instrument is a fringe counting interferometer that monitors the pitch attitude of a model in a wind tunnel. A laser source and detector are mounted above the model. Interference fringes are generated by a small passive element on the model. The fringe count is accumulated and displayed by a processor in the wind tunnel control room. This report includes optical and electrical schematics, system maintenance and operation procedures.
Experimental tests were conducted in the UDRI Environmental Wind/Rain Tunnel to establish the performance of an alpha-vane, that measures angle of attack, in a simulated heavy rain environment. The tests consisted of emersing the alpha-vane in an airstream with a concurrent water spray penetrating vertically through the airstream. The direction of the spray was varied to make an angle of 5.8 to 18 deg with the airstream direction in order to simulate the conditions that occur when an aircraft lands in a heavy rain environment. Rainrates simulated varied from 1000 to 1200 mm/hr which are the most severe ever expected to be encountered by an aircraft over even a 30 second period. Tunnel airspeeds ranged from 85 to 125 miles per hour. The results showed that even the most severe rainrates produced a misalignment in the alpha-vane of only 1 deg away from the airstream direction. Thus for normal rain conditions experienced by landing aircraft no significant deterioration in alpha-vane performance is expected.