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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

The feasibility of a high-altitude aircraft platform with consideration of technological and societal constraints

The feasibility of remotely piloted aircraft performing year around missions at an altitude of 70,000 feet is determined. Blimp and airplane type vehicles employing solar-voltaic, microwave, or nuclear propulsion systems were considered. A payload weighing 100 pounds and requiring 1000 watts of continuous power was assumed for analysis purposes. Results indicate that a solar powered aircraft requires more solar cell area than is available on conventional aircraft configurations if designed for the short days and high wind speeds associated with the winter season. A conventionally shaped blimp that uses solar power appears feasible if maximum airspeed is limited to about 100 ft/s. No viable airplane configuration that uses solar power and designed to withstand the winter environment was found. Both a conventionally shaped blimp and airplane appear feasible using microwave power. Nuclear powered aircraft of these type are also feasible. Societal attitudes toward the use of solar power in high altitude aircraft appear favorable. The use of microwave power for this purpose is controversial, even though the ground station required would transmit power at levels comparable to existing satellite communications stations.

Graves, E. B.↗
NASA NTRS1982

Math modeling for helicopter simulation of low speed, low altitude and steeply descending flight

A math model was formulated to represent some of the aerodynamic effects of low speed, low altitude, and steeply descending flight. The formulation is intended to be consistent with the single rotor real time simulation model at NASA Ames Research Center. The effect of low speed, low altitude flight on main rotor downwash was obtained by assuming a uniform plus first harmonic inflow model and then by using wind tunnel data in the form of hub loads to solve for the inflow coefficients. The result was a set of tables for steady and first harmonic inflow coefficients as functions of ground proximity, angle of attack, and airspeed. The aerodynamics associated with steep descending flight in the vortex ring state were modeled by replacing the steady induced downwash derived from momentum theory with an experimentally derived value and by including a thrust fluctuations effect due to vortex shedding. Tables of the induced downwash and the magnitude of the thrust fluctuations were created as functions of angle of attack and airspeed.

Sheridan, P. F.↗
NASA NTRS1981

Development of a high altitude Spin Parachute

A specially configured 16.6 foot (5.1 meter) Disc Gap Band (DGB) Spin Parachute has been designed, developed, integrated with a sounding rocket, and qualified by flight testing. Design requirements include (1) stable parachute should successfully deploy in the altitude region of 260,000 feet (80 kilometers) from a Super Arcas launch vehicle; (2) after deployment, parachute and payload spin rate should be greater than three rpm; (3) four electric field sensors should be mounted on parachute shroud lines and have provisions to be electrically connected to the suspended payload; and (4) time above 100,000 feet (30 kilometers) should exceed five minutes. The successful meeting of these requirements provided the first known high-altitude deployment of a Spin Parachute.

Silbert, M. N.↗
NASA NTRS1981

Solar radiation monitoring for high altitude aircraft

Ground-based and satellite-based ionizing radiation monitoring systems are considered as alternative methods for ensuring safe radiation levels for high-altitude aircraft. It is found that ground-based methods are of limited accuracy due to insensitivity to solar particles of energies between the riometer upper cutoff of about 50 MeV and the neutron monitor threshold of about 450 MeV. This energy range is demonstrated to be essential for atmospheric radiation monitoring at high altitude, and must be covered by satellite measurement. On the basis of presently available data, the accuracy to which the incident solar particle flux must be measured by satellite-borne detectors is examined and recommendations are made to establish minimum requirements.

Wilson, J. W.↗
NASA NTRS1982

Highly ionizing cosmic rays at mountain altitude

Large arrays of CR-39 plastic track detectors are being used at various depths in the atmosphere to study energetic, highly ionizing particles. The first measurements are made of the energy spectra of He and Li nuclei at mountain altitude (603 g/sq cm) and the first observations of relativistic heavy nuclei (Z/beta greater than or equal to 12; Z ranging from 8 to 14) at subsonic aircraft altitude (186 g/sq cm). A 95 percent CL upper limit of 0.4/sq m-yr was determined for the flux at 603 g/sq cm of particles with Z/beta greater than or equal to 30 and of monopoles with velocity as low as 0.01 c.

Price, P. B.↗
NASA NTRS1982

Altitude variations in stratospheric aerosols of a tropical region

To investigate the possibility that significant amounts of tropical tropospheric air may be convectively introduced into the stratosphere, aerosol samplings over Panama were made at various altitudes using a wire impactor collector. The percentage of particle sizes less than the mean mode decreases with height above the tropopause, suggesting depletion of small particles, possibly due to coagulation. Larger aerosols (greater than 0.3 micron in diam.) are more abundant farther above the tropopause, indicating growth, mainly by condensation. The total particle concentration decreases with increasing height above the tropopause, and also with increasing temperature. Aerosols containing smaller-size particles are thus found closer to the tropopause, and larger-size, more-evolved aerosols occur at higher altitudes. These data indicate that convective activity at the Intertropical Convergence Zone may be a source mechanism for stratospheric aerosols.

Goodman, J.↗
NASA NTRS1982

Plasma injection and transport in the mid-altitude polar cusp

DE-1 hot plasma observations in the mid-altitude polar cusp have shown evidence of a significant velocity filtering phenomenon which is consistent with a latitudinally narrow region of plasma injection located at a geocentric distance of about eight earth radii (in a dipole approximation). Plasma convection from the injection region into the polar cap results in a V-shaped log E vs. observed pitch angle relation at geocentric distances near 4 earth radii. This velocity filtering effect allows the measurement of much smaller flow velocities (about 10 km/sec) than have heretofore been possible with hot plasma measurements. The flows thus determined are consistent with ionospheric flows measured nearly simultaneously by the DE-2 spacecraft, although the magnitudes of the higher altitude flows are higher by a factor of 2 or more than an approximately r to the 3/2 power dipole-field mapping would predict.

Burch, J. L.↗
NASA NTRS1982

DE-1 observations of counterstreaming electrons at high altitudes

Observations of plasma at altitudes of 2-3 earth radii with the High Altitude Plasma Instrument (HAPI) on DE-1 indicate two distinct types of counterstreaming electron events. The type 1 event is characterized by two Maxwellian distribution functions, an isotropic high-temperature component and a field-aligned low temperature component. The type 2 event is distinguished by beams parallel and antiparallel to the magnetic field direction. The observations suggest two distinct mechanisms for accelerating counterstreaming electrons. Type 1 events appear to involve wave-particle interactions while type 2 events imply direct acceleration by oppositely-directed electric fields pointing toward the satellite along magnetic field lines.

Lin, C. S.↗
NASA NTRS1983

Performance of high-altitude, long-endurance, turboprop airplanes using conventional or cryogenic fuels

An analytical study has been conducted to evaluate the potential endurance of remotely piloted, low speed, high altitude, long endurance airplanes designed with 1990 technology. The baseline configuration was a propeller driven, sailplane like airplane powered by turbine engines that used JP-7, liquid methane, or liquid hydrogen as fuel. Endurance was measured as the time spent between 60,000 feet and an engine limited maximum altitude of 70,000 feet. Performance was calculated for a baseline vehicle and for configurations derived by varying aerodynamic, structural or propulsion parameters. Endurance is maximized by reducing wing loading and engine size. The level of maximum endurance for a given wing loading is virtually the same for all three fuels. Constraints due to winds aloft and propulsion system scaling produce maximum endurance values of 71 hours for JP-7 fuel, 70 hours for liquid methane, and 65 hours for liquid hydrogen. Endurance is shown to be strongly effected by structural weight fraction, specific fuel consumption, and fuel load. Listings of the computer program used in this study and sample cases are included in the report.

Liu, G. C.↗
NASA NTRS1983

Storm-time changes of geomagnetic field at MAGSAT altitudes (325-550 Km) and their comparison with changes at ground locations

The values of H, X, Y, Z at MAGSAT altitudes were first expressed as residuals delta H, delta X, delta Y, delta Z after subtracting the model HMD, XMD, YMD, ZMC. The storm-time variations of H showed that delta H (Dusk) was larger (negative) than delta H (Dawn) and occurred earlier, indicating a sort of hysteresis effect. Effects at MAGSAT altitudes were roughly the same (10% accuracy) as at ground, indicating that these effects were mostly of magnetospheric origin. The delta Y component also showed large storm-time changes. The latitudinal distribution of storm-time delta H showed north-south asymmetries varying in nature as the storm progressed. It seems that the central plane of the storm-time magnetospheric ring current undergoes latitudinal meanderings during the course of the storm.

Parada, N. D. J.↗
NASA NTRS1982

Image Analysis for Facility Siting: a Comparison of Lowand High-altitude Image Interpretability for Land Use/land Cover Mapping

For two test sites in Pennsylvania the interpretability of commercially acquired low-altitude and existing high-altitude aerial photography are documented in terms of time, costs, and accuracy for Anderson Level II land use/land cover mapping. Information extracted from the imagery is to be used in the evaluation process for siting energy facilities. Land use/land cover maps were drawn at 1:24,000 scale using commercially flown color infrared photography obtained from the United States Geological Surveys' EROS Data Center. Detailed accuracy assessment of the maps generated by manual image analysis was accomplished employing a stratified unaligned adequate class representation. Both 'area-weighted' and 'by-class' accuracies were documented and field-verified. A discrepancy map was also drawn to illustrate differences in classifications between the two map scales. Results show that the 1:24,000 scale map set was more accurate (99% to 94% area-weighted) than the 1:62,500 scale set, especially when sampled by class (96% to 66%). The 1:24,000 scale maps were also more time-consuming and costly to produce, due mainly to higher image acquisition costs.

Borella, H. M.↗
NASA NTRS1982

Fine altitude resolution radar observations of upper-tropospheric and lower-stratospheric winds and waves

Preliminary results of wind velocity measurements made using the Arecibo 430 MHz radar are presented. These measurements were made in the altitude range between 10 and 30 km, with a time resolution of 1-2 min, and an improved altitude resolution of 150 m. A few interesting phenomena such as a quasi-stationary wavy structure and short period sinusoidal oscillations are discussed.

Sato, T.↗
NASA NTRS1983

High altitude Venus haze from Pioneer Venus limb scans

High-resolution limb scans of Venus made with the Orbiter Cloud Photopolarimeter aboard Pioneer Venus have been used to observe the high altitude Venus haze and its variation over almost one half a Venusian year. A model for a spherical atmosphere with tangential viewing geometry was used to analyze the observations and derive the haze properties. Values are found for the particle size and refractive index, particle number density and scale height, and eddy diffusion coefficient. Single scattering computations show good agreement with observed intensities for particles smaller than 0.3 micron radius and refractive index less than 1.7, consistent with, but not limited to, concentrated sulfuric acid. Particle scale height in the 0.5 to 2 mbar pressure regions varies between 1 and 3 km over the season, latitude, and local time ranges of the observations. Detached layers of haze are sometimes present. An average particle scale height of 2.2 km at 84 km altitude yields an eddy diffusion coefficient of 130,000 sq cm/sec.

Lane, W. A.↗
NASA NTRS1984

High altitude aerodynamic platform concept evaluation and prototype engine testing

A design concept has been developed for maintaining a 150-pound payload at 60,000 feet altitude for about 50 hours. A 600-pound liftoff weight aerodynamic vehicle is used which operates at sufficient speeds to withstand prevailing winds. It is powered by a turbocharged four-stoke cycle gasoline fueled engine. Endurance time of 100 hours or more appears to be feasible with hydrogen fuel and a lighter payload. A prototype engine has been tested to 40,000 feet simulated altitude. Mismatch of the engine and the turbocharger system flow and problems with fuel/air mixture ratio control characteristics prohibited operation beyond 40,000 feet. But there seems to be no reason why the concept cannot be developed to function as analytically predicted.

Akkerman, J. W.↗
NASA NTRS1983

A helicopter flight investigation of roll-control sensitivity, damping and cross coupling in a low altitude lateral maneuvering task

A helicopter in-flight simulation was conducted to determine the effects of variations in roll damping, roll sensitivity, and pitch and roll rate cross-coupling on helicopter flying qualities in a low altitude maneuver. The experiment utilized the UH-1H helicopter in-flight simulator, which is equipped with the V/STOLAND avionics system. The response envelope of this vehicle allowed simulation of configurations with low to moderate damping and sensitivity. A visual, low level slalom course was set up, consisting of constant speed and constant altitude S-turns around the 1000 ft makers of an 8000 ft runway. Results are shown in terms of Cooper-Harper pilot ratings, pilot commentary, and statistical and frequency analyses of the lateral characteristics. These results show good consistency with previous ground simulator results and are compared with existing flying qualities criteria.

Corliss, L. D.↗
NASA NTRS1984

Verification of an altitude decompression sickness prevention protocol for Shuttle operations utilizing a 10.s psi pressure stage

Three test series involving 173-man tess were conducted to define and verify a pre-extravehicular activity (EVA) denitrogenation procedure that would provide acceptable protection against altitude decompression sickness while minimizing the required duration of oxygen (O2) prebreathe in the suit prior to EVA. The tests also addressed the safety, in terms of incidence of decompression sickness, of conducting EVA's on consecutive days rather than on alternate days. The tests were conducted in an altitude chamber, subjects were selected as representative of the astronaut population, and EVA periods were simulated by reducing the chamber pressure to suit pressure while the subjects breathed O2 with masks and worked at EVA representative work rates. A higher than anticipated incidence of both venous bubbles (55%) and symptoms (26%) was measured following all denitrogenation protocols in this test. For the most part, symptoms were very minor and stabilized, diminished, or disappeared in the six-hour tests. Instances of clear, possible, or potential systemic symptoms were encountered only after use of the unmodified 10.2 psi protocol and not after the modified 10.2 psi protocol, the 3.5-hour O2 prebreathed protocol, or the 4.0-hour O2 prebreathe protocol. The high incidence of symptoms is ascribed to the type and duration of exercise and the sensitivity of the reporting technique to minor symptoms. Repeated EVA exposures after only 17 hours did not increase symptom or bubble incidence.

Waligora, J. M.↗
NASA NTRS1982

Orbit determination of low-altitude earth satellites using GPS RF Doppler

This paper investigates the use of one type of GPS-signal derived measurement, the doubly differenced GPS RF Doppler, in the orbit determination of low-altitude earth satellites. This measurement is simple to make, is insensitive to clock errors and provides a continuous determination of the user satellite orbit. Analysis shows that, with a constellation of 18 GPS satellites and 13 ground stations, the 1300 km altitude of a user satellite (TOPEX) can be determined to 5 cm in 2 hours of tracking. Examination is made of the effects of employing fewer ground stations, of different solution strategies, and of introducing fictitious thrust parameters to alleviate the geopotential modeling error which is one of the major error sources.

Wu, S. C.↗