 theoret investig ablat glass-type heat protect shield vari materi properti stagnat point re-enter irbm theoret investig ablat glass-type heat protect shield vari materi properti stagnat point re-enter irbm melt-type heat protect stagnat point re-enter irbm treat emploi homogen opaqu nondecompos glass shield exce temperatur effect variat glass properti ballist re-entri vehicl nose diamet 0 635 ballist factor 3 5 10 re-entri angl 124 9 vertic altitud 100 re-entri speed 4 5 perform 36 glass shield assum combin materi properti investig emploi calcul method yield practic exact transient solut problem corollari steadi flight discuss deriv realist flight condit thermal characterist employ thin light-weight glass shield investig hypothet glass shield lead conclus low thermal conduct high specif heat small thermal diffus desir small thermal diffus yield high surfac temperatur caus high radi heat transfer shield steep temperatur profil normal surfac caus small thermal penetr shield total ablat shield assum irbm re-entri thick emploi glass shield increas monoton thermal diffus materi paramet thick high viscos level high emiss constant surfac supposedli opaqu shield desir properti exert compar small influenc perform disregard glass shield extrem low viscos level 