In the NASA Space Shuttle flights, degradation of the surfaces of several of the Shuttle components has been noticed during the craft's low orbital circlings of the earth. These have been theorized to result from the impact with atomic particles, largely oxygen atoms which occur at those altitudes at orbital speeds of 8.0 km/sec. It was found that the degree of deterioration was of a nature that demands testing of the material in a simulated environment.
Simulating the conditions of high velocity atoms found in the low orbit path of the Shuttle is beyond the state of the art of present technology due to the difficulty of achieving such high speeds in a decomposed gas or particle beam at high particle fluxes.