Search NASA⌕ Search

SEARCH · Search NASA

Results for “EFFECT OF ALTITUDE”

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.

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Seasonal- and Beta-Angle-Dependent Latitude Bias Variations in Natural Decays

Prior work has demonstrated pronounced statistical clustering of natural decays of medium-to-high-inclination orbital objects peaking approximately 30 degrees in Argument of Latitude ahead of nodal crossings. This effect is caused by the physical bulge in the Earth and the overlying atmosphere, that cyclically modifies effective altitude (and therefore density) faster than the trajectory's decay itself. While prior work has averaged seasonal and RAAN effects over all non-uniform atmosphere possibilities to support long-term characterization of the clustering of final entries in generating a pre-mission Expectation of Casualty, the current study characterizes seasonal and beta angle effects as potential influences on the near-term statistical risks of specific tactical decay scenarios, relative to the average. Such effects on the density profile along an orbit may be important considerations in any scenario where small orbital adjustments are used to optimize the timing and location of final entry trajectories. I.E., two identical spacecraft entering in different seasons and/or beta angles may have different minimum-risk scenarios for identical control capabilities and space weather conditions. Further, the early heating history of shallow trajectories is explored, examining the influence of dramatically different density profiles over the final orbit as the spacecraft either skims over or dives into the atmosphere.

Bacon, John B.↗
NASA NTRS1981

Winter nighttime ion temperatures and energetic electrons from OGO 6 plasma measurements

In the reported investigation, ion temperature and suprathermal electron flux data were acquired with the retarding potential analyzer on board the OGO 6 satellite when it was in solar eclipse. Attention is given to measurements in the 400- to 800-km height interval between midnight and predawn in the northern winter nonpolar ionosphere. Statistical analysis of data recorded during a 1 month time span permits a decoupling of horizontal and altitude effects. A distinct longitudinal variation is observed for ion temperature above 500 km, with a significant relative enhancement over the western North Atlantic. Altitude distributions of ion temperature are compatible with Millstone Hill profiles within the common region of this enhancement. Large fluxes of energetic electrons are observed and extend to much lower geomagnetic latitudes in the same longitude sector.

Sanatani, S.↗
NASA NTRS1989

An intercomparison of mesospheric ozone profiles determined by the UVSP and SAGE II solar occultation experiments

A comparison is made of individual UVSP and SAGE II mesospheric ozone profiles between 50 and 70 km altitude as determined by the solar occultation technique. The generally good agreement between the two data sets below about 57 km leads to the conclusion that they may be considered as complementary, thus extending the effective altitude range of both. Comparison of the long-term ozone trend at 55.5 km shows a systematic difference of a few percent between the two measurements.

Aikin, A. C.↗
NASA NTRS1992

Spacecraft Glow and the Eisg/skirt Experiment

The objective of this experiment is to develop an understanding of the physical processes leading to spacecraft glow phenomena. The emphasis is to be on surface temperature and altitude effects. A complete understanding of the phenomena could be used to accomplish the following: (1) characterize optical instrument backgrounds; (2) provide guidelines for thermal insulations; (3) characterize material selection for flight optics and associated spacecraft; and (4) affect flight-operation altitude selection for relevant missions.

Swenson, Gary R.↗
NASA NTRS2004

High-speed Imaging of Global Surface Temperature Distributions on Hypersonic Ballistic-Range Projectiles

The NASA-Ames ballistic range provides a unique capability for aerothermodynamic testing of configurations in hypersonic, real-gas, free-flight environments. The facility can closely simulate conditions at any point along practically any trajectory of interest experienced by a spacecraft entering an atmosphere. Sub-scale models of blunt atmospheric entry vehicles are accelerated by a two-stage light-gas gun to speeds as high as 20 times the speed of sound to fly ballistic trajectories through an 24 m long vacuum-rated test section. The test-section pressure (effective altitude), the launch velocity of the model (flight Mach number), and the test-section working gas (planetary atmosphere) are independently variable. The model travels at hypersonic speeds through a quiescent test gas, creating a strong bow-shock wave and real-gas effects that closely match conditions achieved during actual atmospheric entry. The challenge with ballistic range experiments is to obtain quantitative surface measurements from a model traveling at hypersonic speeds. The models are relatively small (less than 3.8 cm in diameter), which limits the spatial resolution possible with surface mounted sensors. Furthermore, since the model is in flight, surface-mounted sensors require some form of on-board telemetry, which must survive the massive acceleration loads experienced during launch (up to 500,000 gravities). Finally, the model and any on-board instrumentation will be destroyed at the terminal wall of the range. For these reasons, optical measurement techniques are the most practical means of acquiring data. High-speed thermal imaging has been employed in the Ames ballistic range to measure global surface temperature distributions and to visualize the onset of transition to turbulent-flow on the forward regions of hypersonic blunt bodies. Both visible wavelength and infrared high-speed cameras are in use. The visible wavelength cameras are intensified CCD imagers capable of integration times as short as 2 ns. The infrared camera uses an Indium Antimonide (InSb) sensor in the 3 to 5 micron band and is capable of integration times as short as 500 ns. The projectiles are imaged nearly head-on using expendable mirrors offset slightly from the flight path. The proposed paper will discuss the application of high-speed digital imaging systems in the NASA-Ames hypersonic ballistic range, and the challenges encountered when applying these systems. Example images of the thermal radiation from the blunt nose of projectiles flying at nearly 14 times the speed of sound will be given.

Wilder, Michael C.↗
NASA NTRS2005

The Variation of Hydrocarbon Abundances with Latitude and Season in Saturn's Stratosphere

We have developed a realistic, time-variable, one-dimensional, seasonal model for stratospheric photochemistry on Saturn using the Caltech/ JPL KINETICS code [1,2,3]. The model accounts for variations in ultraviolet flux due to orbital position, solar-cycle variations, and ring-shadowing effects. The results for two Saturnian years, starting at Ls = 0 in 1950 and running until the upcoming northern vernal equinox in 2009, are presented for numerous latitudes. The same two model years are run over and over again until the model convergences to make sure that high-altitude effects have had a chance to propagate down through the atmosphere. We use the SOLAR2000 model [4,5], in combination with the spectra presented in [6], to predict the ultraviolet flux at any wavelength and any point in time during the simulation. Saturn's orbital position during the simulation was taken from the ephemeris calculator at http://ssd.jpl.nasa.gov/horizons.html [7]. The photochemical model is derived from "Model C" of [8] and uses a hydrocarbon reaction list that has been extensively updated from that presented in [3].

Moses, J. I.↗
NASA NTRSDate not supplied

ACS3 - Flight Dynamics for A Solar Sail Technology Demonstration Mission

The NASA's Advanced Composite Solar Sail System (ACS3) mission consist of a spacecraft that will deploy an 80 m 2 solar sail in a 1000 km sun-synchronous orbit. The main objective of the mission is to demonstrate that the solar wind can impulse the spacecraft to change the semimajor-axis and obtain a different orbit altitude. The sail will be composed of a combination of composite materials with distinct properties, and it will be deployed with lightweight booms from a 12U CubeSat bus, developed by Nanoavionics. The spacecraft will be launched aboard an Electron launch vehicle from Rocket LAB Launch Complex in New Zealand no earlier than July 2023. This paper covers the orbital mechanics and navigation developments to support the mission, from the solar sail trajectory model to the actual flight dynamics system to provide the orbit determination analysis prior to flight. First, we introduce a description of our high-fidelity propagation that accounts for the solar radiation pressure to produce predictive ephemeris of the solar sail performance with several spacecraft attitude modes. As part of our results, we present plots of the expected altitudes achieved by the spacecraft once the solar sail is deployed under various assumptions of the solar weather. In addition to that, we present a full description of our orbit determination process which relies in GPS state vectors to accurately estimate the position and velocity uncertainties at a frequent cadence during the mission. The outcome of this process will be critical to achieving the objective of determining effective altitude change produced by the solar sail.

Solar Sail↗
NASA NTRSDate not supplied

ACS3: Flight Dynamics

The NASA's Advanced Composite Solar Sail System (ACS3) mission consist of a spacecraft that will deploy an 80 m2 solar sail in Low Earth Orbit (LEO). The main objective of the mission is to demonstrate that the solar wind can impulse the spacecraft to change the semimajor-axis and obtain a different orbit altitude. The sail will be composed of a combination of composite materials with distinct properties, and it will be deployed with lightweight booms from a 12U CubeSat bus, developed by Nanoavionics. The spacecraft will be launched aboard an Electron launch vehicle from Rocket LAB Launch Complex in New Zealand. This paper covers the orbital mechanics and navigation developments to support the mission, from the solar sail trajectory model to the actual flight dynamics system to provide the orbit determination analysis prior to flight. First, we introduce a description of our high-fidelity propagation that accounts for the solar radiation pressure to produce predictive ephemeris of the solar sail performance with several spacecraft attitude modes. As part of our results, we present plots of the expected altitudes achieved by the spacecraft once the solar sail is deployed under various assumptions of the solar weather. In addition to that, we present a full description of our orbit determination process which relies in GPS state vectors to accurately estimate the position and velocity uncertainties at a frequent cadence during the mission. The outcome of this process will be critical to achieving the objective of determining effective altitude change produced by the solar sail.

Solar sail↗
NASA NTRS1977

Aerodynamics of horizontally-opposed aircraft engine installations

The goal of cooling installation design is to provide adequate cooling air flow to the engine with a minimum drag penalty. To achieve this goal, attention must be given to certain aerodynamic factors involved in the design problem. In the present paper, the factors which influence the aerodynamic design of horizontally-opposed engine cooling installations are discussed with particular reference to the performance of the aircraft in terms of the dynamic pressure generated for the power output of the engine, the gains or losses through the propeller, proper inlet design, altitude effects on the orifice characteristics of the engine, and exit area sizing. Results of a flight research program showed that the inlet design has a significant influence on cooling effectiveness and drag; the inlet should be designed for low velocity ratios and should avoid small radii of curvature in its geometry. The influence of the propeller on the inlet appears to cause the stagnation point on the lip to move toward the inside.

Miley, S. J.↗
NASA NTRS1981

Stratospheric HF and HCl observations /15 June 1981/

Balloon measurements of the stratospheric HF/HCl ratio are reported. Seven far-infrared rotational lines of HF and HCl were observed at elevation angles of 25, 18 and 8 deg by a far-infrared Fourier-transform spectrometer on board a balloon platform at 28.5 km. Analysis of line intensities yields an average HF/HCl ratio of 0.18 + or - 0.02 at an effective altitude of 33 km, with a water vapor mixing ratio of about 4 ppmv. Results are noted to be in reasonable agreement with the calculated profile of Sze and Ko (1981) with 4.5 ppmv H2O.

Traub, W. A.↗
NASA NTRS1984

Thematic Mapper Sensor Characteristics

The characteristics of the thematic mapper (TM) sensor onboard the LANDSAT 4 satellite are discussed. Topics include instantaneous field of view size, rise time, delay time, square wave response, bright target recovery, altitude effects, band to band registration, and scan profile linearity.

Engel, J.↗