The Space Environment

The space environment, seen as beginning in the center of the earth, extends to infinity. In the past few decades outer space has been penetrated. These initial successful steps depended on a number of factors, one of which was the use of plastics. As in terrestrial uses, plastics have their place in space. 

Plastics will continue to be required in space applications from rockets to vehicles for landing on other planets. The space structures, reentry vehicles, and equipment such as antennas, sensors, and an astronaut s personal communication equipment that must operate outside the confines of a spaceship will encounter bizarre environments (see Table 4-20). Temperature extremes, thermal stresses, micrometeorites, and solar radiation are sample conditions that will be encountered. 

Entry Vehicles 1500-mile Ballistic Entry Nose Cone 5000-mile Ballistic Entry Nose Cone Earth Orbital Ballistic Entry Capsule Lifting Orbital Entry Glider Lunar Vehicle Earth Entry Mars Planetary Entry Probe 

Ablative systems are not limited by the heating rate or environmental temperature, but rather by the total heat load. In spite of this limitation, however, the versatility of ablation has permitted it to be used on almost every recent hypervelocity atmospheric vehicle. Moreover, it appears that ablation will continue to be favored as the primary thermal protection method for future flight vehicles. 

No single universally acceptable ablative material has been developed, nor is one likely to be created. Nevertheless, the interdisciplinary efforts of materials scientists and engineers have resulted in obtaining a wide variety of ablative compositions and constructions. These thermally protective materials have been arbitrarily categorized by their matrix composition. Typical materials are given in Table 4-21. 

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Composite materials must survive in the environment to which they are subjected at least as well as the conventional materials they replace. Some of the harmful environments encountered include exposure to humidity, water immersion, salt spray, jet fuel, hydraulic fluid, stack gas (includes sulfur dioxide), fire, lightning, and gunfire as well as the combined effects of the space environment. 

Jursa, A. S. (1985). Handbook of Geophysics and the Space Environment. Springfield VA National Technical... 

Laser cooling can efficiently reduce the velocity of the atoms but cannot circumvent the acceleration due to gravity. On the ground the 1-g gravity level sets clear limitations to the ultimate sensitivities. The HYPER project (Hyper precision cold atom interferometry in space) will follow precisely this line and will benefit from the space environment, which enables very long interaction time (few seconds) and low spurious vibrational level. The sensitivity of the atomic interferometer can achieve few 10 rad.s. Hz to rotation and to acceleration. This very sensitive and accurate apparatus... 

Many asteroid spectra tend to be "redder" than the spectra of the corresponding meteorites. Reddened spectra have lower reflectivity, weaker absorptions, and spectral slopes that are flatter in the red end. This phenomenon has been attributed to "space weathering," a catchall term referring to any process that modifies the optical properties of surfaces of airless bodies exposed to the space environment. 

In 2006 Beauchamp reported on the expanding role of mass spectrometry in developing new instruments for laboratory simulations and in situ exploration of the space environment.13 The cometary and interstellar dust analyzer ( ), which was designed for the direct analysis of the space environment and mounted on the spacecraft, is a time-of-flight mass spectrometer for measuring, in situ, the chemical composition and the original mass of the individual dust grains. 

Aerogel is a special materials with extreme micron porosity. It consists of separate particles of several nanometers, interconnected in a high-porosity branched structure. It was made on the basis of gel consisting of colloid silicone, the structural parts of which are filled with solvents. Aerogel is subjected to high temperature under pressure which rises to the critical point it is very strong and easily endures stress both at lift-off and in the space environment. This material has already been tried in space by Spacelab II and Eureca shuttles, as well as by the American Mars Pathfinder Rover. 

I. Katz, The Behavior of System in the Space Environment, Eds. R. N. DeWitt, D. Duston and A. K. Hyder (Kluwer Academic Pubhshers, 1991). 

K. S. W. Champion, A. E. Cole and A. J. Kantor, Standard and Reference Atmospheres , Handbook of Geophysics and the Space Environment, Ed. A. S. Jursa (United States Air Force, Air Force Geophysics Laboratory, 1985) Chap. 14. 

M. Van Eesbeek, F. Levadou and A. Mihntchouk, A Study of FEP Behaviour in the Space Environment, 25th International Conference on Environmental Systems, held in San Diego, CA, 10-13 July 1995 (Society of Automotive Engineers, 1995) Paper No. 951640. 

A. C. Tribble, The Space Environment Implications for Spacecraft Design (Princeton University Press, New Jersey, 1995). 

V. E. Skurat, Evailuation of Reaiction Efficiencies of Polymeric MateriaJs in Their Interaction with Fast (5 eV) Atomic-Oxygen , 7th International Symposium on Material in the Space Environment, held in Toulouse, France, 16-20 June 1997, Enseignment et espaice (Cepadues-Elditions, Toulouse, Prance, 1997) pp. 231-235. 

Almost 100 astronauts spent time on the space station during its lifetime, and countless experiments provided data to help scientists better understand the effects of the space environment on man and materials. The ISS has and will continue to benefit from the lessons learned with Mir. 

Geller, M.A., Dynamics of the middle atmosphere. Space Sci Rev 34, 359, 1983. Gombosi, T.I., Physics of the Space Environment. Cambridge University Press, 1998. 

Such mirrors are capable to withstand stress imposed by launch and the space environment, including extreme and rapid temperature variations, high vacuum, zero gravity, vibration and shock. 

To ensure the proper thermal simulation of the space environment, the absorptance of a space chamber s cold wall for both solar and room temperature radiation must be known. The absorptance of the cold-wall surface depends on the substrate coating, the type and thickness of the condensable gas deposited, and the source of incident radiation. 

It is evident that new approaches to cooling systems for space use should be explored. One such approach is a cooling system using the sublimation of a solid into the high vacuum of space. This system would use the space environment to advantage. 

Materials that are directly exposed to the space environment must also withstand or be protected from atomic oxygen. Atomic oxygen is prevalent in the low earth orbit (LEO), approximately 100 to 350 miles from Earth. At this distance, molecular oxygen reacts with ultraviolet light to produce monoatomic oxygen which is extremely chemically reactive and erosive. Most adhesives used in spacecraft, however, are sandwiched between two adherends, thus not directly exposed. 

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