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AVCOAT was used for the heat shield on NASA's Apollo command module. [4] In its final Apollo form, this material was called AVCOAT 5026–39. Although AVCOAT was not used for the Space Shuttle orbiters, NASA again used the material for its Orion spacecraft [5] first for the initial Orion test and then for a different type of heat shield for the later Orions.
AVCOAT is a NASA-specified ablative heat shield, a glass-filled epoxy–novolac system. [ 41 ] NASA originally used it for the Apollo command module in the 1960s, and then utilized the material for its next-generation beyond low Earth orbit Orion crew module, which first flew in a December 2014 test and then operationally in November 2022. [ 42 ]
The key to a reusable shield against this type of heating is very low-density material, similar to how a thermos bottle inhibits convective heat transfer. [citation needed] Some high-temperature metal alloys can withstand reentry heat; they simply get hot and re-radiate the absorbed heat.
This heat shield was composed of phenolic formaldehyde resin. During reentry, this material charred and melted away, absorbing and carrying away the intense heat in the process. The heat shield has several outer coverings: a pore seal, a moisture barrier (a white reflective coating), and a silver Mylar thermal coating that looks like aluminum foil.
Atmospheric re-entry spacecraft use phenol formaldehyde resin as a key component in ablative heat shields (e.g. AVCOAT on the Apollo modules). As the heat shield skin temperature can reach 1000-2000 °C, the resin pyrolizes due to aerodynamic heating. This reaction absorbs significant thermal energy, insulating the deeper layers of the heat shield.
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The heat shield absorbs some of this energy while much is also dissipated into the atmospheric gasses, mostly by radiation. During the latter stages of descent, a parachute is typically deployed and any heat shield is detached. Rockets may be located at the back shell to assist in control or to retropropulsively slow descent. Airbags may also ...
Elements like heat, humidity, light, and air are the “main enemies of vitamin freshness,” says Blatner. “Keep them cool, dry, and out of the sun.” So, probably not in your medicine cabinet.
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