Sublimitable carbon-carbon structure for nose tip for re-entry space

Abstract

A thermal protection system arrangement and method of manufacture for a carbon-carbon nose tip of a re-entry space vehicle that is expected to encounter very high heat fluxes upon re-entry into the earth's atmosphere. The arrangement includes a carbon-carbon nose tip which has a first sublimatable material infiltrated into the outer portion of the nose tip for release of thermal energy to the environment during the high heat fluxes of re-entry. A second sublimatable material which sublimates at heat fluxes materially less than that of the first sublimatable material is infiltrated into the inner portion of the nose tip so that the nose tip releases energy to the environment and erodes in a controlled manner thereby maintaining the interior of the nose tip at a desired temperature. The first sublimatable material is preferably a refractory element which has been partially converted to a sublimatable carbide during carbonization and graphitization of the carbon-carbon nose tip and is further converted to a carbide during re-entry. The second sublimatable material is preferably a fluorocarbon which sublimates at a lower temperature when the internal structure of the carbon-carbon nose tip reaches a predetermined temperature, thereby permitting the carbon-carbon nose tip to achieve temperatures well in excess of those presently obtainable by known other structures.