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At least 541 records · Page 30

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NASA NTRS1990

High altitude AM0 testing of PV concentrator lens elements

Recently, the NASA Lewis Research Center modified its Lear High Altitude Test Facility to fly two prototype ENTECH minidome Fresnel lens photovoltaic concentrator elements. The tests were highly successful, and the results verified the ability of the Lear High Altitude Facility to measure the optical performance of individual concentrator lens elements and concentrator/cell combinations at near AM0 insolation conditions. The two concentrator lenses flown achieved optical efficiencies, based on a gallium arsenide concentrator cell response, of 89.8 percent and 90.0 percent. The flights demonstrated the ability of the aircraft to maintain the pointing accuracy required to obtain useful data. With proper alignment of the collimating tube and the pilot's sunsight, this facility could easily maintain a pointing accuracy of + or - 0.5 deg for a sufficiently long time to obtain accurate, reproducible results.

Piszczor, M. F.↗

NASA NTRS1991

NASA/USRA high altitude research aircraft. Gryphon: Soar like an eagle with the roar of a lion

At the equator, the ozone layer ranges from 65,000 to 130,000+ feet. This is beyond the capabilities of the ER-2, which is NASA's current high altitude reconnaissance aircraft. The Universities Space Research Association, in cooperation with NASA, is sponsoring an undergraduate program which is geared to designing an aircraft that can study the ozoned layer at the equator. This aircraft must be able to satisfy four mission profiles. Mission one is a polar mission which ranges from Chile to the South Pole and back to Chile, a total range of 6000 n. mi. at 100,000 feet with a 2500 lb. payload. The second mission is also a polar mission with a decreased altitude of 70,000 feet and an increased payload of 4000 lb. For the third mission, the aircraft will take-off at NASA Ames, cruise at 100,000 feet carrying a 2500 lb. payload, and land in Puerto Montt, Chile. The final mission requires the aircraft to take-off at NASA Ames, cruise at 100,000 feet with a 1000 lb. payload, make an excursion to 120,000 feet, and land at Howard AFB, Panama. All three missions require that a subsonic Mach number be maintained due to constraints imposed by the air sampling equipment. The aircraft need not be manned for all four missions. Three aircraft configurations were determined to be the most suitable for meeting the above requirements. The performance of each configuration is analyzed to investigate the feasibility of the project requirements. In the event that a requirement can not be obtained within the given constraints, recommendations for proposal modifications are given.

Rivera, Jose↗

NASA NTRS1991

The HAMMER: High altitude multiple mission environmental researcher

At the equator, the ozone layer ranges from 65,000 to 130,000+ feet which is beyond the capabilities of the ER-2, NASA's current high altitude reconnaissance aircraft. The Universities Space Research Association, in cooperation with NASA, is sponsoring an undergraduate program which is geared to designing an aircraft that can study the ozone layer at the equator. This aircraft must be able to satisfy four mission profiles. Mission one is a polar mission which ranges from Chile to the South Pole and back to Chile, a total range of 6000 n. mi. at 100,000 feet with a 2500 lb. payload. The second mission is also a polar mission with a decreased altitude of 70,000 feet and an increased payload of 4000 lb. For the third mission, the aircraft will take-off at NASA Ames, cruise at 100,000 feet carrying a 2500 lb. payload, and land in Puerto Montt, Chile. The final mission requires the aircraft to take-off at NASA Ames, cruise at 100,000 feet with a 1000 lb. payload, make an excursion to 120,000 feet, and land at Howard AFB, Panama. All three missions require that a subsonic Mach number is maintained due to constraints imposed by the air sampling equipment. The aircraft need not be manned for all four missions. Three aircraft configurations were determined to be the most suitable for meeting the above requirements. The performance of each configuration is analyzed to investigate the feasibility of the project requirements. In the event that a requirement can not be obtained within the given constraints, recommendations for proposal modifications are given.

Hayashi, Darren↗

NASA NTRS1991

Large scale lunar horizon glow and a high altitude lunar dust exosphere

All three Apollo 17 astronauts sketched a `lunar horizon glow', seen from orbit above the moon. It is shown that the shape of the glow is compatible with scattering of sunlight off of gas or dust at high altitudes above the moon. The present mathematical modeling best simulates the glow with submicron dust grains whose spatial density varies with altitude above the moon as exp(-H/H(s)), where H(s) is in the range of 5 to 20 km. These dust grains are probably electrically charged and ejected above the lunar surface by local electric fields.

Zook, Herbert A.↗

NASA NTRS1992

Orbit maintenance for low altitude near-circular lunar orbits

The behavior of low altitude near-circular lunar orbits is a key design issue for some missions in the proposed Space Exploration Initiative. The lunar gravity field strongly perturbs low altitude orbits, so an effective orbit maintenance strategy is needed. This strategy must contend with the long term orbit evolution due to the zonal gravity field. Two possible orbit control scenarios are passive control using a frozen orbit and active orbit control using maneuvers. A maneuver strategy can be designed which optimizes the propellant required for long term orbit sustenance. The long term requirements dominate the total propellant required for orbit control. Additional propellant may be required to offset the impact of medium period gravity field effects. Careful selection of maneuver times and directions, however, can eliminate any medium period penalty.

Cook, Richard A.↗

NASA NTRS1992

Appraisal of digital terrain elevation data for low-altitude flight

The use of terrain elevation databases in advanced guidance and navigation systems has greatly expanded. However, the limitations and accuracies of these databases must be considered and established prior to safe system flight evaluation. A simple approach to quantify reasonable flight limits is presented and evaluated for a helicopter guidance system dependent on a terrain database. The flight test evaluated involved a helicopter equipped with a Global Positioning System (GPS) receiver and radar altimeter, and a ground station GPS receiver which provided improved helicopter positioning. The precision navigation and radar altimeter data was acquired while flying low-altitude missions in south-central Pennsylvania. The aircraft-determined terrain elevations were compared with the terrain predicted by the Defense Mapping Agency (DMA) Level 1 terrain elevation data for the same area. The results suggest a safe set clearance altitude of 220 ft for flight testing of a DMA-based guidance avionic in the same area.

Zelenka, Richard E.↗

NASA NTRS1993

What is the Relationship Between Altitude and Weight in a Model Rocket?

This experiment was designed to find a function of payload weight for altitude. The same rocket was launched a repeated number of times with the same engine and varying amounts of weight. After performing experimentation, it was calculated that the altitude in meters could be predicted with the equation A = (2.8(W exp 2)) - (70.6W + 310.3), with weight expressed in the unit ounces.

Betz, Jonathan↗

NASA NTRS1991

High-altitude reconnaissance aircraft

At the equator the ozone layer ranges from 65,000 to 130,000+ ft, which is beyond the capabilities of the ER-2, NASA's current high-altitude reconnaissance aircraft. This project is geared to designing an aircraft that can study the ozone layer. The aircraft must be able to satisfy four mission profiles. The first is a polar mission that ranges from Chile to the South Pole and back to Chile, a total range of 6000 n.m. at 100,000 ft with a 2500-lb payload. The second mission is also a polar mission with a decreased altitude and an increased payload. For the third mission, the aircraft will take off at NASA Ames, cruise at 100,000 ft, and land in Chile. The final mission requires the aircraft to make an excursion to 120,000 ft. All four missions require that a subsonic Mach number be maintained because of constraints imposed by the air sampling equipment. Three aircraft configurations were determined to be the most suitable for meeting the requirements. The performance of each is analyzed to investigate the feasibility of the mission requirements.

Yazdi, Renee Anna↗

NASA NTRS1993

The cone structure and focusing of the electric field of VLF and LF waves at high altitudes of the ionosphere

This paper presents a short review of the frequency and angle dependencies of the electric field radiated by an electric dipole E = E(sub 0)cos(omega)t in a magnetoplasma and detailed results of numerical calculations of (E) in the VLF and LF frequency bands 0.02f(sub b) is less than or equal to F is less than or equal to 0.5f(sub b) in the ionosphere and magnetosphere in the altitude region Z = (800 - 6000) km (F is approximately (4 - 500) kHz and f(sub b) is approximately equal to (1.1 to 0.2) MHz is the electron gyro-frequency). The amplitudes of the electric field have large maxima in four regions: close to the direction of the Earth magnetic field line B(sub 0) (it is the so called Axis field E(sub 0); in the Storey E(sub St); Reversed Storey E(sub RevSt); and Resonance E(sub Res) Cones. The maximal values of E(sub 0), E(sub Res), and E(sub Rev ST) are the most pronounced close to the low hybrid frequency, F is approximately F(sub L). The flux of the electric field is concentrated in very narrow regions, with the apexes angles of the cones delta(beta) is approximately (0.1 - 1) degree. The enhancement and focusing of the electric field increases with altitude starting at Z is greater than 800 km. At Z is greater than or equal to 1000 up to 6000 km, the relative value of E, in comparison with its value at Z equals 800 km is about (10(exp 2) to 10(exp 10)) times larger. Thus, the flux of VLF and LF electromagnetic waves in the Earth magnetoplasma produces and is guided by very narrow pencil beams, similar, let us say, to laser beams.

Alpert, Y. L.↗

NASA NTRS1993

Tidal winds at mesopause altitudes over Arecibo (18 deg N, 67 deg W), 5-11 April 1989 (AIDA '89)

A tidal analysis of the imaging Doppler interferometer scattering point parameter data at upper mesosphere-lower thermosphere altitudes (70-110 km) is presented, on the basis of the procedure developed by Groves (1959), over the interval April 5-11, 1989 at Aercibo as part of Project AIDA. This analysis reveals a typical equatorial easterly circulation, with mean meridional circulation becoming significant only above 96 km. A periodogram analysis shows the diurnal tide to be the most significant feature of the wind field at these altitudes, with zonal amplitudes up to some 50 m/s and meridional amplitudes approximately half this value. The semidiurnal tide is well developed in both zonal and meridional directions only above 96 km. Both 8- and 6-hr components become significant above 100 km, the 6-h component being as strong as both the 24- and 12-h tides at 100 km.

Roper, R. G.↗

NASA NTRS1991

Determination of the altitude of the nitric acid layer from very high resolution ground-based IR solar spectra

A ground-based solar spectrum at a spectral resolution of about 0.002/cm is used to determine the altitude of the HNO3 layer. The 870/cm spectral region, which is essentially free from absorptions from other species, is employed. The data were obtained with the University of Denver 2.5-m maximum path difference Fourier Transform interferometer spectrometer system. A set of 13 HNO3 vertical profiles were used in the analysis. The best fit obtained for the 'starting' profile (which is centered at 24 km), and the best fit for the profile centered at 26 km are shown. For displacements of greater than 2 km, the discrepancy between the synthetic and observed spectra becomes readily discernible by inspection of the spectra. It is shown that the 'best fit' rms residuals are quite sensitive to the assumed altitude of the HNO3 layer.

Blatherwick, R. D.↗

NASA NTRS1992

Appraisal of digital terrain elevation data for low-altitude flight

Zelenka, Richard E.↗

NASA NTRS1920

Tests of the Daimler D-IVa Engine at a High Altitude Test Bench

Reports of tests of a Daimler IVa engine at the test-bench at Friedrichshafen, show that the decrease of power of that engine, at high altitudes, was established, and that the manner of its working when air is supplied at a certain pressure was explained. These tests were preparatory to the installation of compressors in giant aircraft for the purpose of maintaining constant power at high altitudes.

Noack, W G↗

NASA NTRS1922

The Use of Multiplied Pressures for Automatic Altitude Adjustments

The efficient performance of an airplane requires that certain adjustments be made as the density of the air through which the airplane passes changes. The safety of the over-dimensioned aircraft engine depends upon careful manipulation of spark advance and throttle opening and a proper control of a variable pitch propeller, if the maximum performance of the supercharged engine is to be obtained. It is evident that there is a real need for satisfactory devices to make such adjustments automatically. Discussed here is a method of automatic compensation which deserves consideration in the design of such devices. Existing schemes for automatic compensation all depend upon some contrivance which functions primarily because of changes in atmospheric pressure. In these devices a leak in the supposedly tight chamber means utter failure. The elimination of this source of danger is one of the aims of the method of altitude compensation described here. The change suggested is to make the source of operation the difference between atmospheric pressure and some multiple of atmospheric pressure instead of the difference between the atmospheric pressure and that of the gas confined in a tight chamber. The design of a device based on this method of altitude compensation is given.

Sparrow, Stanwood S↗

NASA NTRS1923

An Optical Altitude Indicator for Night Landing

One of the most ingenious of the devices intended for use in night landing, especially emergency landing, is a very simple optical instrument known as the Jenkins night altitude indicator. The design and operation of this instrument, which allows a pilot to determine the altitude of the aircraft, is discussed. The author discusses various modifications and improvements that might be made to the instrument.

Warner, John A C↗

NASA NTRS1923

Results of experimental flights at high altitudes with Daimler, Benz and Maybach engines to determine mixture formation and heat utilization of fuel

The experimental flights described herein were made with the object of obtaining information regarding the following two questions, which as yet have not been sufficiently elucidated. These are: 1. What effect has altitude upon the formation of the mixture? 2. What alteration takes place, with increasing altitude, in the utilization of the heat contained in the fuel?.

Kutzbach, K↗

NASA NTRS1925

An Altitude Chamber for the Study and Calibration of Aeronautical Instruments

The design and construction of an altitude chamber, in which both pressure and temperature can be varied independently, was carried out by the NACA at the Langley Memorial Aeronautical Laboratory for the purpose of studying the effects of temperature and pressure on aeronautical research instruments. Temperatures from +20c to -50c are obtained by the expansion of CO2from standard containers. The chamber can be used for the calibration of research instruments under altitude conditions simulating those up to 45,000 feet. Results obtained with this chamber have a direct application in the design and calibration of instruments used in free flight research.

Reid, J E↗

NASA NTRS1937

Charts expressing the time, velocity, and altitude relations for an airplane diving in a standard atmosphere

In this report charts are given showing the relation between time, velocities, and altitude for airplanes having various terminal velocities diving in a standard atmosphere. The range of starting altitudes is from 8,000 to 32,000 feet, and the terminal velocities vary from 150 to 550 miles per hour. A comparison is made between an experimental case and the results obtained from the charts. Examples pointing out the use of the charts are included.

Pearson, H A↗