Meteorology and Range Safety

Jerry Haber

Recognizing the importance of defining the environment through which launch vehicles must operate between surface and the upper regions of the atmosphere, NASA has published guidelines for addressing factors from winds to precipitation to earthquakes (NASA/TM-2008–215633). While the specific data in these publications have emphasized facilities in the United States, much of the material has broader applicability.

Unfortunately, no such comprehensive narrative and collection of environmental or meteorological data oriented toward range safety has been created. In the United States, many of the launch facilities publish guides to range users providing a level of guidance as to the range safety data requirements and provide insights as to the facilities the individual ranges have for obtaining meteorological data and how it may affect risks generated by launch vehicles. Publicly available guidelines developed through the years by the ranges in the United States may be identified by referring to the Range Commanders Council public website (Range Commanders Council Public Web Site). In this regard, attention is directed to reference (Meteorology Group, Range Commanders Council, 1992), which provides an overall guide to instrumentation available for meteorological measurements and their characteristics, and to reference (Meteorology Group, Range Commanders Council, 1994), which provides a discussion of the quality control measures for surface meteorological measurements. This document characterizes the error sources to be managed and discusses both real-time processing and post-processing concerns to assure that the resulting data is meaningful.

Most launch complexes are part of the synoptic network. Twice a day atmospheric soundings are performed, the data is processed and integrated with other reporting stations. Soundings are supplemented by measurements using ground based equipment, such as tower-based wind measurements, acoustical and optical soundings. Important information for range safety purposes includes a profile of wind speed and direction, temperature, moisture, wind shear, atmospheric pressure and air density.

Debris risk analysis requires meteorological data for four types of calculations: (1) translation of the re-entering debris by the winds; (2) dispersion of the debris about the mean impact points by temporal and spatial wind variability; (3) atmospheric effect on the demise of re-entering debris; and (4) determining the local speed of sound to assure that the proper aerodynamic coefficients are employed in trajectory calculations. Demise includes burning propellant that may be consumed during re-entry and aerothermal demise. Demise is primarily governed by atmospheric density. (It should be noted that the effect of the wind on debris is also affected by the atmospheric density, as are drag effects.)

Distant focusing overpressure is governed by the atmospheric parameters governing the lower atmosphere that may alter the blast wave propagation. This includes wind speed and direction, atmospheric density, and humidity. The rate of change of the effective propagation speed of the blast wave front determines how refraction will alter the direction of propagation. Moreover, it also affects the convergence or divergence of the wave front as it is propagated and hence the amplitude of the shock wave at receptors.

Complete analyses of toxic risks require a substantial amount of meteorological data, as discussed in Chapter 5.1. These data are used to develop a characterization of the release of the toxic materials, the formation of a stable source term, and the transport and diffusion of the toxic materials. The type of data required strongly depends on the level of sophistication of the model. More sophisticated models attempt to solve complex sets of equations that require substantial amounts of data characterizing both the toxic release and atmospheric conditions. As a minimum, data must be sufficient to characterize the rate of release, the formation of a pool on the Earth’s surface, or for buoyant substances the initial cloud rise and stabilization, and the subsequent transport of the cloud by the wind-field and diffusion by different scales of turbulence. Minimum requirements include a temperature and wind profile and a characterization of atmospheric stability from which turbulence characteristics are inferred.