Operation Of Aerospace Vehicles Research Articles

Aerospace Meteorology: An Overview of Some Key Environmental Elements

The natural terrestrial environment plays a significant role in the design and operation of aerospace vehicles (space vehicles and rockets) and in the associated integrity of aerospace systems and elements. Addressed herein are some of the key vehicle and environment areas of concern plus lessons learned that have been identified over a number of years. Many of these aerospace meteorology related events occurred during the development and interpretation of natural environment inputs, especially those of terrestrial environment, used in the design and development of the Saturn Apollo and Space Shuttle vehicles plus associated mission operations. Background is given regarding the actions needed to avoid having to re-learn these lessons.

Aerospace Meteorology: Some Lessons Learned from the Development and Application of NASA Terrestrial Environment Design Criteria

Aerospace meteorology plays an important role in the design, development, and operation of aerospace vehicles. Many of the issues and lessons presented occurred during the involvement of the authors with the development and interpretation of aerospace environment inputs, especially those of the terrestrial environment. Background for the actions needed to avoid the issue being repeated or the lesson having to be relearned is addressed. The engineering application importance and some issues associated with the presentation and interpretation of terrestrial environment guidelines associated with aerospace meteorology elements are presented.

Notes on the design and operation of aerospace vehicles

Geographical, seasonal, and day-to-day variations in the vertical distributions of atmospheric density and temperature must be considered in the design and operation of reentry vehicles. This work is part of a continuing effort to compile, analyze, and present information on the distribution of the atmospheric temperature in a form suitable for use in the design and operation of aerospace vehicles. We have used temperature data obtained from rockets which are mostly based on the datasonde system throughout the decade 1969–1978. Profiles and the individual arrays of coefficients of correlation of the temperature at 20 km with temperature at higher altitudes up to 60 km are shown for each season for locations in the low, middle, and high latitudes.

Probability Distribution of Vertical Longitudinal Shear Fluctuations

In order to properly design aerospace systems (conventional airplanes, V/STOL vehicles, space vehicles, etc.) the engineer must consider the vertical structure of the horizontal wind during the launch and landing phases of flight. One way do this is with vertical two-point wind differences (wind shear). In turbulent flows like those found near the ground, wind shear is composed a steady-state part associated with the mean wind profile and a fluctuating part produced by atmospheric turbulence. Mean wind profile theory can be used to specify the steady-state wind shear; however, the fluctuating part is a stochastic process which can only be specified statistically. This paper discusses some recent measurements of third and fourth moments of vertical differences (shears) of longitudinal velocity fluctuations obtained in unstable air at the NASA 150 m meteorological lower site at Cape Kennedy, Fla. Each set of measurements consisted of longitudinal velocity fluctuation time histories obtained at the 18, 30, 60, 90, 120 and 150 m levels, so that 15 wind-shear time histories were obtained from each set of measurements. It appears that standardized third and forth moments S and K of wind shear are universal functions of Δz/z̄ and z̄/L0, where Δz̄ is the vertical distance between the two points over which the wind difference is calculated, z̄ the height of the mid-point of Δz above natural grade, and L0 the surface Monin-Obukhov stability length. As Δz/z̄ → 2, K → 3, S → 0, and S > 0, K > 3 for Δz/z̄ < 2. Thus, it appears that the joint distribution function of the longitudinal wind fluctuations at two levels is not bivariate Gaussian and that it can only be approximated with a Gaussian distribution for sufficiently large value of Δz/z̄. The kurtosis K appears to be independent of z̄/L0. However, the skewness S seems to experience a rather abrupt transition at z̄/L0∼O(−1). The implications of these and other results relative to the design and operation of aerospace vehicles are discussed.

Influence of Airspeed on Noise Generated Within Various Fixed- and Rotary-Wing Aircraft

The data reported in this study will assist human-factors engineers and aeromedical personnel in assessing noise exposures associated with the operation of aerospace vehicles. The influence of increased flight speeds on the level and character of noise generated within the cockpits of 148 fixed- and rotary-wing aircraft is described and illustrated. Stereotyped collateral effects resulting from increases in airspeed are categorized for different types of vehicles and the noise envelopes that evolved from this study are grouped into two main categories: fixed-wing and rotary-wing. Secondary noise envelopes are then illustrated for each of the two main groups according to the type of power plant mated to the vehicle. The envelopes derived from this study clearly illustrate differences in the character and level of noise generated within various aircraft due to increased airspeed. Also, and probably more important, the various envelopes verify that within similar types of aircraft the increased airspeed results in changes in noise levels and spectra that are stereotyped.

Meteorological measurement accuracies for use in the design and operation of aerospace vehicles

meteorological measurement accuracies for use in the design and operation of aerospace vehicles