SEARCH · Search NASA
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Exposure to g-forces causes changes in the vascular systems of animals. The vessels are distorted and their contents may escape. Various parts of a given organ may react differently according to their structure, and arteries will undergo changes that depend on their position relative to the direction of the g-force vector.
The effects of several parameters on the relative motions of a space shuttle orbiter design and its external tank were determined during staging for the return-to-launch-site abort mode. The parameters included angle of attack, dynamic pressure, flight-path angle, pitch rate, elevon effectiveness and the use of thrust applied to the tank. The relative positions of each component were determined by a separation trajectory computer program which incorporated data obtained in wind-tunnel tests with the orbiter and tank in proximity. These tests were conducted at Mach 10.3 in a continuous-flow hypersonic tunnel. All separation cases were initiated at a constant Mach number of 10 with an assumed sideslip angle of 0 deg.
The effect was examined of aircraft position and attitude, of measurement errors, and of computational approximations on the size, shape, and position of a perspective radar image of an airport runway as might be displayed by an independent landing monitor in transport aircraft. The effect on runway image geometry was examined for different aircraft attitudes and different aircraft positions relative to a standard three degree glide slope. Measurement errors investigated were errors in radar azimuth angle and range, and errors in those aircraft parameters supplied to the radar for use in converting the radar image into a perspective format (namely pitch, roll, and altitude). Also investigated were the effects of using certain mathematical approximations, such as small angle, in the coordinate transformation which converts the image to a perspective format.
The technique of differential very-long baseline interferometry was used to measure the relative positions of the ALSEP transmitters at the Apollo 12, 14, 15, 16, and 17 lunar landing sites with uncertainties less than 0.005 of geocentric arc. These measurements yielded improved determinations of the selenodetic coordinates of the Apollo landing sites, and of the physical libration of the moon. By means of a new device, the differential Doppler receiver (DDR), instrumental errors were reduced to less than the equivalent of 0.001. DDRs were installed in six stations of the NASA spaceflight tracking and data network and used in an extensive program of observations beginning in March 1973.
A motorized chair (with precise servo controls) accelerated the observer in a clockwise (CW) or counterclockwise (CCW) direction at rates that ranged in logarithmic progression from 0.02 to 6.00 deg/sq sec. The target, a narrow collimated line of light, was contained within a goggle device worn by the observer and therefore fixed in relative position to him. The illusion, appearing as rightward or leftward movement of the visual target in the direction of acceleration, was determined by a double staircase procedure among 300 normal and 4 labyrinthine-defective observers. None of the latter perceived the illusion. The majority of normal observers revealed no substantial directional difference (CW vs. CCW threshold). Threshold frequency distributions ranged in rate (deg/sq sec) from 0.020 to 0.950; the threshold of response in more than half the normal observers was less than 0.10, in over three-fourths was less than 0.20, in over 90% less than 0.30, and 100% less than 1.00.
Measurements of NH3 absorption coefficients are presented for several transitions of a C-13(O-16)2 laser for small concentrations of NH3(p less than 1 torr) for absorption lines broadened to 1 atm with N2. NH3 absorption coefficients were determined for laser transitions R(8)(920.2194 wavelengths/cm) to R(28)(933.8808 wavelengths/cm) of the 00 1 - (10 0,02 0)I band. The strongest absorption coefficient K = 36.09 + or - 1.43 per (atm-cm) was measured for the R(18) transition for the NH3 line, aQ(6,6), and is larger than has been found in any previous measurements with a CO2 laser. The dependence of K on total pressure was also obtained for select transitions, and the frequency separation between the R(18) laser transition and the neighboring NH3 line aQ(6,6) was determined to be 550 + or - 50 MHz. These results are significant for long path absorption monitoring of NH3 with CO2 lasers since the path length can be reduced by approximately 40% and for heterodyne detection of NH3 since the relative position of the laser transition to the NH3 absorption line is well within the bandpass of Hg-Cd-Te photomixers.
The Astrometric Multiplexing Area Scanner (AMAS) is an instrument designed to perform photoelectric long focus astrometry of small fields. Modulation of a telescope focal plane with a rotating Ronchi ruling produces a frequency modulated signal from which relative positions and magnitudes can be extracted. Evaluation instrumental precision, accuracy and resolution characteristics with respect to a variety of instrumental and cosmical parameters indicates 1.5 micron precision and accuracy for single stars under specific conditions. This value decreases for increased number of field stars, particularly for fainter stars.
A Rockwell built 0.030-scale 45-0 modified Space Shuttle Orbiter Configuration 14?A/B model and a Boeing built 0.030-scale 747 carrier model were tested to provide six component force and moment data for each vehicle in proximity to the other at a matrix of relative positions, attitudes and test conditions (angles of attack and sideslip were varied). Orbiter model support system tare effects were determined for corrections to obtain support-free aerodynamics. In addition to the balance force data, pressures were measured. Pressure orifices were located at the base of the Orbiter, on either side of the vertical blade strut, and at the mid-root chord on either side of the vertical tail. Strain gages were installed on the Boeing 747 vertical tail to indicate buffet onset. Photographs of aerodynamic configurations tested are shown.
A method is presented for integrating satellite images into a geophysical data interpretation system. Aspects of the method include: an attempt to automatically interpret images by structural, mainly topological, methods for the mapping of geological contours; an analysis of the position relation of the contours gives a skeleton stratigraphy (order of succession); and a system combining some of the extracted elements with geographic data to make an objective search for an interpretation hypothesis. Some examples are presented.
The author has identified the following significant results. In the S192 data, a peak was apparent in the lower altitudes that was not present in the shorter wavelengths and grew with increasing wavelength beginning with band 7. For ten S192 wavelengths, the relative altitude increment was determined by knowledge of the relative position of the highest point in the scan arc. Using this scheme, results of scaling and inverting data for passes 47 and 61 were put into two models. Each result had three chart representations: (1) limb brightness measurement, (2) attenuation coefficients, and (3) ratio of the aerosol and Rayleigh coefficients to accentuate layers.
An experimental investigation was conducted to model the film-cooling performance for a turbine-vane leading edge using the stagnation region of a cylinder in cross flow. Experiments were conducted with a single row of spanwise-angled coolant holes for a range of the coolant blowing ratio with a freestream-to-wall temperature ratio of about 2.1 and a Reynolds number of 170,000, characteristic of the gas-turbine environment. Data from local heat-flux measurements are presented for coolant-hole injection angles of 25, 35, and 45 deg with the row of holes located at three positions relative to the stagnation line on the cylinder. Results show the spanwise (hole-to-hole) variation of heat-flux reduction due to film cooling and indicate conditions for the optimum film-cooling performance.
The Close Grid Geodynamic Measurement System is conceived as an orbiting ranging device with a ground base grid of reflectors or transponders (spacing 1.0 to 30 km), which are projected to be of low cost (maintenance free and unattended), and which will permit the saturation of a local area to obtain data useful to monitor crustal movements in the San Andreas fault zone. The system includes a station network of 75 stations covering an area between 36 deg N and 38 deg N latitudes, and 237 deg E and 239 deg E longitudes, with roughly half of the stations on either side of the faults. In addition, the simulation of crustal movements through the introduction of changes in the relative positions between grid stations, weather effect for intervisibility between satellite and station and loss of observations thereof, and comparative evaluation of various observational scheme-patterns have been critically studied.
Test OH51 was a phase change paint test conducted in the LaRC 31-inch CFHT utilizing models 46-0, 64-0, and 90-0. Model 46-0 represented the space shuttle configuration 139 Orbiter. Model 90-0 represented the configuration 140 Orbiter. Model 64-0 represented the forward 45% portion of the Orbiter wing. The partial wing was tested with a shock generator located at various positions relative to the wing. The test was conducted at Mach 10.0, angles of attack from 27.5 deg through 37.5 deg, and Reynolds numbers of 0.5 and 1.5 million per foot.
A load regulating mechanical latch is described that has a pivotally mounted latch element having a hook-shaped end with a strike roller-engaging laterally open hook for engaging a stationary strike roller. The latch element or hook is pivotally mounted in a clevis end of an elongated latch stem that is adapted for axial movement through an opening in a support plate or bracket mounted to a structural member. A coil spring is disposed over and around the extending latch stem and the lower end of the coil spring engages the support bracket. A thrust washer is removably attached to the other end of the latch stem and engages the other end of the coil spring and compresses the coil spring thereby preloading the spring and the latch element carried by the latch stem. The hook-shaped latch element has a limited degree of axial travel for loading caused by structural distortion which may change the relative positions of the latch element hook and the strike roller. Means are also provided to permit limited tilt of the latch element due to loading of the hook.
The technique of differential very-long-baseline inteferometry (VLBI) Apollo Lunar Surface Experiments Package was used to measure the relative positions of the (ALSEP) transmitters at the Apollo 12, 14, 15, 16, and 17 lunar landing sites with uncertainties less than 0.005 sec of the geocentric arc. These measurements yielded improved determinations of the selenodetic coordinates of the Apollo landing sites, and of the physical libration of the moon.
Very long base line interferometry (VLBI) observations of lunar radio transmitters have been combined with data from laser ranging to lunar retroreflectors to estimate simultaneously (1) parameters in models of the lunar orbit and libration and (2) the selenodetic coordinates of the radio transmitters and retroreflectors. For the ratio of the mass of the sun to that of the earth plus moon, a value of approximately 328,900.5 is obtained. The lunar moment-of-inertia ratios beta and gamma are also determined. The values and most of the uncertainties obtained for the third-degree harmonics of the moon's gravity field are comparable to those which have been obtained by others from observations of lunar-orbiting spacecraft. However, the results for the two third-degree gravity coefficients have much less uncertainty than determinations based on laser data alone. For the relative position vectors of the lunar radio transmitters and the retroreflectors, the estimates have uncertainties of about 30 m along the earth-moon direction and about 10 m in each of the two transverse coordinates.
Observations of signals from the ALSEP transmitters via differential very-long-baseline interferometry (VLBI) are being made to determine the relative selenocentric coordinates of the ALSEPs and the motion of the moon about its center of mass. By VLBI the relative positions of the ALSEPs can be determined with uncertainties less than 5 meters, and the orientation of the moon within 0.5 second of selenocentric arc.
Coplanar aerial combat is modeled with constant speeds and specified turn rates. The minimum capture radius which will always permit capture, regardless of the initial conditions, is calculated. This 'critical' capture radius is also the maximum range which the evader can guarantee indefinitely if the initial range, for example, is large. A composite barrier is constructed which gives the boundary, at any heading, of relative positions for which the capture radius is less than critical.