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At least 451 records · Page 25

All sources NASA NTRS DOE OSTI

NASA NTRS1980

Effect of wing location and strakes on stability and control characteristics of a monoplanar circular missile with low-profile tail fins at supersonic speeds

A wind tunnel test was conducted at Mach numbers from 1.70 to 2.86 to extend the aerodynamic data base for wing tail effect on stability and control characteristics of monoplanar missiles. The results are summarized to show the effects of tail fin dihedral angle, wing location, and nose body strakes. The results indicate that an increase in tail fin dihedral angle produces positive increments in directional stability that allow greater trimmed lift coefficient values (maneuver potential) to be obtained. An increase in wing tail gap for the Mach number range reduces the aerodynamic center travel and produces reductions in directional stability at the lower angles of attack. A change in wing height (vertical location) strongly influences the angle of attack at which pitch up and the most directional stability occur. The addition of strakes to the baseline configuration increases directional stability, which allows a significant increase in stable trimmed maneuver capability. The tail fins of the baseline configuration are effective in producing roll and yaw control that are accompanied by favorable yaw and roll, respectively.

Blair, A. B., Jr.↗

NASA NTRS1981

Optimum damper locations for a free-free beam

Algorithms to optimally locate and design dampers for large space structures were developed. The requirements for distributed sensing and actuation in control of structural systems were determined. Mathematical programming was used to solve for optimum damping rate and location. Actuator dynamics were considered to solve for optimum actuator mass.

Horner, G. C.↗

NASA NTRS1981

MLS antenna locations for the deHaviland DASH 7 aircraft

Several proposed aircraft antenna locations were investigated to determine their potential for satisfying the microwave landing system antenna coverage requirements. The results of this investigation are presented and antenna locations are recommended for the deHavilland DASH 7 aircraft.

Gilreath, M. C.↗

NASA NTRS1981

Design of a laser system for instantaneous location of a longwall shearer

Calculations and measurements for the design of a laser system for instantaneous location of a longwall shearer were made. The designs determine shearer location to approximately one foot. The roll, pitch, and yaw angles of the shearer track are determined to approximately two degrees. The first technique uses the water target system. A single silicon sensor system and three gallium arsenide laser beams are used in this technique. The second technique is based on an arrangement similar to that employed in aircraft omnidirectional position finding. The angle between two points is determined by combining information in an onmidirectional flash with a scanned, narrow beam beacon. It is concluded that this approach maximizes the signal levels.

Stein, R.↗

NASA NTRS1981

Medium-range, objective predictions of thunderstorm location and severity for aviation

This paper presents a computerized technique for medium-range (12-48h) prediction of both the location and severity of thunderstorms utilizing atmospheric predictions from the National Meteorological Center's limited-area fine-mesh model (LFM). A regional-scale analysis scheme is first used to examine the spatial and temporal distributions of forecasted variables associated with the structure and dynamics of mesoscale systems over an area of approximately 10 to the 6th sq km. The final prediction of thunderstorm location and severity is based upon an objective combination of these regionally analyzed variables. Medium-range thunderstorm predictions are presented for the late afternoon period of April 10, 1979, the day of the Wichita Falls, Texas tornado. Conventional medium-range thunderstorm forecasts, made from observed data, are presented with the case study to demonstrate the possible application of this objective technique in improving 12-48 h thunderstorm forecasts for aviation.

Wilson, G. S.↗

NASA NTRS1981

Significance of turbulence and transition location on radiative heating with ablation injection

This paper presents forebody flowfield solutions for Jupiter entry conditions where the ablation injection rate is coupled with the surface heating rate. The calculations are made with a time-dependent viscous-shock-layer analysis where the flow is assumed to be in chemical equilibrium. Both laminar and turbulent solutions are presented to describe the impact of turbulence on surface mass loss rates for flow conditions where the heating is due primarily to radiation. Results are also presented where the transition location to turbulent flow is arbitrarily varied. Results show that the radiative heating rate values based on several downstream transition locations adjust quickly to the corresponding values based on transition near the stagnation point.

Moss, J. N.↗

NASA NTRS1981

Interpolating for the location of remote sensor data

An interpolation algorithm is presented as a practical alternative to common interpolation and approximation methods when applied to the problem of determining the location of remote sensor data. This algorithm is based upon knowledge of the geometry of the problem and is shown to be inherently more accurate than common interpolation schemes which may be applied to all types of data. A practical location problem is used to demonstrate its accuracy and computational cost.

Puccinelli, E. F.↗

NASA NTRS1981

Saturnian kilometric radiation: Source locations

The surce locations of both polariation components of the saturn kilometer wavelength radiation were deduced using Voyager 1 and Voyager 2 planetary radio astronomy data and assumptions about radiation beam geometry. Radio source footprints were compared with the surface locations of saturns ultraviolet aurorae, its polar cap boundary, and its polar cusp.

Kaiser, M. L.↗

NASA NTRS1982

Rotary balance data for a typical single-engine general aviation design for an angle-of-attack range of 8 deg to 90 deg. 2: Influence of horizontal tail location for Model D

The influence of horizontal tail location on the rotational flow aerodynamics is discussed for a 1/6-scale general aviation airplane model. The model was tested using various horizontal tail positions, with both a high and a low-wing location and for each of two body lengths. Data were measured, using a rotary balance, over an angle-of-attack range of 8 to 90 deg, and for clockwise and counter-clockwise rotations covering an Omega b/2V range of 0 to 0.9.

Barnhart, B.↗

NASA NTRS1983

Effect of empennage location on twin-engine afterbody-nozzle aerodynamic characteristics at Mach Numbers from 0.6 to 1.2

The Langley 16-foot transonic tunnel was used to determine the effects of several empennage and afterbody parameters on the aft-end aerodynamic characteristics of a twin-engine fighter-type configuration. Model variables were as follows: horizontal tail axial location and incidence, vertical tail axial location and configuration (twin- versus single-tail arrangements), tail booms, and nozzle power setting. Tests were conducted over a Mach number range from 0.6 to 1.2 and over an angle-of-attack from -2 deg to 10 deg. Jet total-pressure ratio was varied from jet off to approximately 10.0.

Leavitt, L. D.↗

NASA NTRS1983

Location and source of ionospheric high latitude troughs

The global extent of the high-latitude troughs from altitudes between approximately 400 and 1100 km are explored using ion composition measurements from the satellite OGO 6. The trough locations are compared with prominent magnetosphere-ionosphere coupling signatures in order to understand the source and controlling mechanisms for these plasma depletions. It is found that, on the average, the troughs at all local times are in the vicinity of the auroral oval and move equatorward in response to increasing magnetic activity. The average trough location is compared with the average polar cap boundary as defined by the convection electric field reversal and the electron trapping boundary, as well as with the maximum horizontal magnetic disturbance associated with the large-scale field-aligned currents. It is concluded that the troughs are mainly the result of enhanced chemical O(+) losses in regions having high convection velocities.

Grebowsky, J. M.↗

NASA NTRS1983

Factors controlling the location of the Venus bow shock

The location of the Venus bow shock determined from magnetic field measurements during the first and third years of Pioneer Venus orbiter operation is examined and compared with nearly simultaneously obtained interplanetary solar wind data to determine those factors that control the size of the Venus bow shock. The location of the intersection of the bow shock with the terminator that is best determined by the data does not vary significantly between years 1979 and 1981 and is only 16 percent more distant than the Venera 9 and 10 shock when account is taken of solar wind aberration. Alfvenic Mach number and magnetosonic Mach number affect the size of the bow shock significantly. Solar wind dynamic pressure has a lesser effect. No significant asymmetries in the shock shape were found either as a result of the orientation of the clock angle of the IMF in the terminator plane or the angle of the IMF relative to the shock normal.

Tatrallyay, M.↗

NASA NTRS1983

Satellite data relay and platform locating in oceanography. Report of the In Situ Ocean Science Working Group

The present and future use of satellites to locate offshore platforms and relay data from in situ sensors to shore was examined. A system of the ARGOS type will satisfy the increasing demand for oceanographic information through data relay and platform location. The improved ship navigation provided by the Global Positioning System (GPS) will allow direct observation of currents from underway ships. Ocean systems are described and demand estimates on satellite systems are determined. The capabilities of the ARGOS system is assessed, including anticipated demand in the next decade.

Chase, R.↗

NASA NTRS1984

Effects of spacecraft reflections on RF interferometer position location accuracy

This report describes one of three study tasks related to the application of an RF interferometer aboard a low-orbiting spacecraft to determine the location of ground-based transmitters. Computer modeling was used to estimate the error in the measured signal angle-of-arrival caused by reflection and diffraction off the spacecraft. Existing computer codes (NEC-BSC) were modified and used to determine the perturbation, due to the spacecraft, in the phase difference between two interferometer antennas, suspended on either side of the spacecraft. This phase perturbation was found as a function of the angle-of-arrival of the signal from a far-field source. The spacecraft antennas were assumed to be circularly polarized with a cardioid pattern. It was found that the perturbation was as much 12.4 deg within the + or - 60 deg field-of-view. This suggests that phase calibration and correction of phase measurements are essential for precision position location using this technique.

Wallace, R. G.↗

NASA NTRS1984

Microwave and X-ray observations of delayed brightenings at sites remote from the primary flare locations

Five examples of solar flares observed with the 17-GHz interferometer at Nobeyama in which a secondary microwave burst occurred at a distance of 100,000 km to 1,000,000 km from the primary flare site are presented. The secondary microwave burst in all five cases had a similar time profile to the primary burst with a delay of 2 to 25 s. The velocity of a triggering agent inferred from this delay and spatial separation is 10,000 km to 100,000 km/s. The intensity of the secondary burst was a factor of 3 to 25 smaller than that of the primary burst in all events except for one case in which it was a factor of 2 larger. The polarization degree of the secondary burst at 17 GHz was 35%, significantly higher than the average value for typical impulsive bursts. Two of the events were accompanied by meterwave type III/V bursts located high in the corona between the primary and secondary sites. For two of the other events, X-ray images of he secondary source were obtained with the hard-X-ray imaging spectrometer on the Solar Maximum Mission. These observations strongly suggest that the distant microwave bursts were produced by electrons with energies of 10 keV to 100 keV which were channeled along a huge loop from the main flare site to the remote location.

Nakajima, H.↗

NASA NTRS1984

Three precise gamma-ray burst source locations

The precise source regions of three moderately intense gamma ray bursts are derived. These events were observed with the first interplanetary burst sensor network. The optimum locations of the detectors, widely separated throughout the inner solar system, allowed for high accuracy, over-determined source fields of size 0.7 to 7.0 arc-min(2). All three locations are at fairly high galactic latitude in regions of low source confusion; none can be identified with a steady source object. Archived photographs were searched for optical transients that are able to be associated with these source fields; one such association was made.

Cline, T. L.↗

NASA NTRS1982

Development of satellite position location system for aircraft and boat distress beacons

An international satellite system for the detection and location of distress beacons carried on aircraft and vessels is in its technical checkout phase. User demonstration and evaluation (D&E) will start in early 1983 and continue for two years. The D&E phase and a subsequent transition period will form the basis for improved search and rescue operations for the 1980's and beyond. The system, called COSPAS/SARSAT, has international participation involving the U.S., Canada, and France as SARSAT members and joint participation with the Soviet Union's COSPAS Project. Norway and the U.K. have recently joined as investigators. Average position location error of the satellite aided processing is expected to be from 10-20KM for the existing 121.5/243 MHz distress beacons and from 2-5KM for experimental beacons transmitting in the 406 MHz band.

Kahle, D. R.↗

NASA NTRS1984

Three precise gamma-ray burst source locations

Cline, T. L.↗