Editing Atmospheric entry (section)

====AVCOAT====
[[AVCOAT 5026-39|AVCOAT]] is a [[NASA]]-specified ablative heat shield, a glass-filled [[epoxy]]–[[novolac]] system.<ref name=nasa196808>[https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19680021275_1968021275.pdf Flight-Test Analysis Of Apollo Heat-Shield Material Using The Pacemaker Vehicle System] {{Webarchive|url=https://web.archive.org/web/20200925144304/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19680021275_1968021275.pdf |date=September 25, 2020 }} [[NASA]] Technical Note D-4713, pp. 8, 1968–08, accessed 2010-12-26. ''"Avcoat 5026-39/HC-G is an epoxy novolac resin with special additives in a fiberglass honeycomb matrix. In fabrication, the empty honeycomb is bonded to the primary structure and the resin is gunned into each cell individually. ... The overall density of the material is 32 lb/ft3 (512 kg/m3). The char of the material is composed mainly of silica and carbon. It is necessary to know the amounts of each in the char because in the ablation analysis the silica is considered to be inert, but the carbon is considered to enter into exothermic reactions with oxygen. ... At 2160O R (12000 K), 54 percent by weight of the virgin material has volatilized and 46 percent has remained as char. ... In the virgin material, 25 percent by weight is silica, and since the silica is considered to be inert the char-layer composition becomes 6.7 lb/ft3 (107.4 kg/m3) of carbon and 8 lb/ft3 (128.1 kg/m3) of silica."''</ref><!-- the AVCOAT article claims this material was used on the Apollo command module, but no citation is provided so the claim is not [[WP:V|verified]]. -->

NASA originally used it for the [[Apollo command and service module#Command Module (CM)|Apollo command module]] in the 1960s, and then utilized the material for its next-generation beyond low Earth orbit [[Orion (spacecraft)|Orion]] crew module, which first flew in a December 2014 test and then operationally in November 2022.<ref name=nasa20090407>[http://www.nasa.gov/home/hqnews/2009/apr/HQ_09-080_Orion_Heat_Shield.html NASA.gov NASA Selects Material for Orion Spacecraft Heat Shield] {{Webarchive|url=https://web.archive.org/web/20101124220318/http://www.nasa.gov/home/hqnews/2009/apr/HQ_09-080_Orion_Heat_Shield.html |date=November 24, 2010 }}, 2009-04-07, accessed 2011-01-02.</ref> The Avcoat to be used on Orion has been reformulated to meet environmental legislation that has been passed since the end of Apollo.<ref name=fg20090310>{{Cite web|url=http://www.flightglobal.com/articles/2009/03/10/323585/nasas-orion-heat-shield-decision-expected-this-month.html|title=Flightglobal.com NASA's Orion heat shield decision expected this month 2009-10-03, accessed 2011-01-02|access-date=January 2, 2011|archive-date=March 24, 2009|archive-url=https://web.archive.org/web/20090324160130/http://www.flightglobal.com/articles/2009/03/10/323585/nasas-orion-heat-shield-decision-expected-this-month.html|url-status=live}}</ref><ref>{{cite web|url=http://www.thefreelibrary.com/Company+Watch+-+NASA-a0198584187|title=Company Watch – NASA. – Free Online Library|website=www.thefreelibrary.com|access-date=January 2, 2011|archive-date=October 22, 2012|archive-url=https://web.archive.org/web/20121022003103/http://www.thefreelibrary.com/Company+Watch+-+NASA-a0198584187|url-status=live}}</ref>