They'd been sprayed with a half-meter layer of carbon-based foam, which was supposed to act as a thermal shield as well as providing protection from cosmic radiation.
In between the two layers of glass is the dead air that makes for a thermal shield.
Masonite and steel plates enclose the thermal shield on its top and sides, forming a biological shield for radiation protection.
That is to be enclosed in a cone shell and a thermal shield to withstand the heat generated when they enter the planet's atmosphere.
In relatively quick succession, the conical protection and thermal shield will be discarded.
During inspections the utility discovered cracks in the bolts in the support blocks holding up the thermal shield, which captures heat from the plant's reactor core.
It was far enough out from their thermal shield to feel the full glare, so it was heating up fast.
Then she slipped into a thermal shield and headed out into the not-quite-dark.
"Must be some sort of thermal shield," Mort said after a quick look.
The RS-68 engine is mounted to the lower thrust structure of the vehicle by a four-legged (quadrapod) thrust frame, and enclosed in a protective composite conical thermal shield.