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Results for “Density 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.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Median density altitude profiles of the major ions in the central nightside Venus ionosphere

Altitude profiles of median values for total ion density, constituent ion densities, and the molecular ion group of the central nightside Venus ionosphere are presently derived from the Pioneer Venus retarding potential analyzer's measurements during the first five seasonal passages of the spacecraft through the nightside hemisphere. The altitude profiles for total ion density, constituent ions and the molecular ion group are compared with previously predicted profiles derived from numerical models in which the ionization source was O(+) ions transported from the dayside ionosphere and electron impact-produced ionization. The electron impact-produced profiles for O(+) is 2 orders of magnitude smaller than that observed.

Knudsen, William C.↗
NASA NTRS1997

Neutral Orbital Altitude Density Effects on the International Space Station

One of the design requirements of the International Space Station (ISS) is that each year accelerations of one micro-g cannot be exceeded at the ISS internal payload location for 6 periods of not less than 30 consecutive days. Although there are other causes, this study deals only with the accelerations caused by atmospheric drag. The critical ambient neutral density, computed using the Marshall Engineering Thermosphere Model, required to produce accelerations of one micro-g on the ISS, is estimated using an atmospheric drag acceleration equation. Results show that the design requirements may be difficult to meet during periods of extremely high solar activity; the planned reboost and altitude strategies for the ISS may have to be revised to allow for the uncertainty in the prediction of neutral atmospheric density within the 100-day period established for orbital decay before reboost.

Smith, O.E.↗
NASA NTRS1986

Rarefied aerodynamics and upper atmosphere density from multiple orbiter flight measurements

Flight data from six flights of the experimental High Resolution Accelerometer Package (HIRAP), a micro-g accelerometer system, have been analyzed to produce rarefied flow aerodynamic coefficients of the Orbiter and freestream density in the altitude range from 60 km to 160 km. The direct measurements of the lift to drag ratio (L/D) are used to obtain individual normalized body-axis force coefficients in a least-squares regression scheme. An aerodynamics model based on an exponential function of Knudsen number is used for the individual coefficients. The calculated L/D from the flight determined coefficients agree with the multiple flight data measurements to within about 5 percent. Simultaneously, an upper altitude density variation is also obtained from the data. Density altitude profiles exhibit a wave feature on all flights. The wave has an amplitude of about + or - 25 percent relative to the 1962 Standard atmosphere model.

Buck, G. M.↗
NASA NTRS1984

Lightning flash density versus altitude and storm structure from observations with UHF- and S-band radars

The UHF-(70.5 cm wavelength) and S-band (10 cm wavelength) radar at NASA/Wallops Island Research Facility in Virginia, U.S.A. have been used to relate lightning activity with altitude and with the reflectivity structure of thunderstorms. Two centers of lightning flash density were found; one between 6 and 8 km altitude and another between 11 and 15 km. Previously announced in STAR as N83-31206

Mazur, V.↗
NASA NTRS1972

Design, fabrication and calibration of alpha particle densitometers for measuring planetary atmospheric density

An alpha particle densitometer was developed for possible application to measurement of the atmospheric density-altitude profile on Martian entry. The device uses an Am-241 radioactive-foil source, which emits a distributed energy spectrum, located about 25 to 75 cm from a semiconductor detector. System response - defined as the number of alphas per second reaching the detector with energy above a fixed threshold - is given for Ar and CO2. The altitude profile of density measurement accuracy is given for a pure CO2 atmosphere with 5 mb surface pressure. The entire unit, including dc-dc converters, requires less than 350 milliwatts of power from +28 volts, weighs about 0.85 lb and occupies less than 15 cubic inches volume.

Sellers, B.↗
NASA NTRSDate not supplied

Regulatory Considerations for Future Regional Air Mobility Aircraft

Regional Air Mobility (RAM) is a term that is used to describe equitable, economical, and environmentally friendly access to air commerce at local airports. The term “regional” can imply a wide range of aircraft payload and/or number of passengers carried, types of airports served, distances between aircraft origin/destination pairs, crew requirements, runways lengths, required energy reserves, and much more. This paper describes the regulations and other considerations that apply to RAM operations in the conterminous United States and defines a notional set of requirements to apply to a planned NASA study on RAM aircraft sizing. These notional requirements include: (1) a payload sufficient to carry up to nine passengers or equivalent cargo, (2) nominal distances between the origin and destination of at least 100 miles, with 300 miles desired, (3) ability to operate from a runway that is no more than 3,364 ft in length at a density altitude of 3,100 ft, with a desire for a 2,665 ft runway at 4,100 ft density altitude, and (4) energy reserves at least sufficient for 45 minutes of operation at normal cruise power, with a desire for energy reserves that also include diversion to an alternate airport at least 50 nautical miles away. Aircraft that meet these desired capabilities will be able to provide commercial access to at least 2,507 airports in the conterminous United States without revision to airworthiness, operating, or security regulations.

Nicholas K Borer↗
NASA NTRSDate not supplied

Regulatory Considerations for Future Regional Air Mobility Aircraft

Regional Air Mobility (RAM) is a term that is used to describe equitable, economical, and environmentally friendly access to air commerce at local airports. The term “regional” can imply a wide range of aircraft payload and/or number of passengers carried, types of airports served, distances between aircraft origin/destination pairs, crew requirements, runways lengths, required energy reserves, and much more. This paper describes the regulations and other considerations that apply to RAM operations in the conterminous United States and defines a notional set of requirements to apply to a planned NASA study on RAM aircraft sizing. These notional requirements include: (1) a payload sufficient to carry up to nine passengers or equivalent cargo, (2) nominal distances between the origin and destination of at least 100 miles, with 300 miles desired, (3) ability to operate from a runway that is no more than 3,364 ft in length at a density altitude of 3,100 ft, with a desire for a 2,665 ft runway at 4,100 ft density altitude, and (4) energy reserves at least sufficient for 45 minutes of operation at normal cruise power, with a desire for energy reserves that also include diversion to an alternate airport at least 50 nautical miles away. Aircraft that meet these desired capabilities will be able to provide commercial access to at least 2,507 airports in the conterminous United States without revision to airworthiness, operating, or security regulations.

Nicholas K Borer↗
NASA NTRS1982

The 2145 A dayglow and the high altitude nitric oxide density

It is argued that dissociative photoionization of N2 by solar ultraviolet radiation at wavelengths shorter than 329 A is a large source of atmospheric N(+)(5S 0 2) ions which radiate at 2143.6 A and 2139.7 A. Calculations of the daytime production of N(+)(5S 0 2) ions are carried out. The band pass of the instrument used to measure the intensity of the NO gamma band at 2150 A contains the N(+) emission wavelengths and we suggest that the NO densities at high altitudes may be affected.

Victor, G. A.↗
NASA NTRSDate not supplied

Data Driven UAM Flight Energy Consumption Prediction and Risk Assessment

With the current technological advancements revolutionizing the concept of Urban Air Mobility (UAM) and package delivery, there is also, a concurrent need to quantify the operational safety of these vehicles in terms of their associated risk. Conducting safe flight operations is critical for UAM vehicles which are electrically Vertical Takeoff and Landing (eVTOL) vehicles, to operate in current Air traffic control. In this paper, a data-driven method for UAM vehicle energy consumption prediction and risk quantification with conditional value-at-risk based on energy consumption distribution is presented. Significant factors affecting energy consumption, such as density altitude, aircraft design, airspeed, and collision avoidance algorithms, are considered in the data-driven based energy consumption prediction of different eVTOL

Data-driven↗