You searched for: “ablator
ablator (s) (noun), ablators (pl)
1. The heat shields of space vehicles, which melt or wear away during the reentry into the earth's atmosphere: The scientist created a new ablator which could withstand extreme heat.
2. The outer surface of a spacecraft or missile: Ablation is the erosion of the protective outer surface, or ablator, of a spacecraft or missile resulting from aerodynamic heating caused by travel at hypersonic speeds during reentry through the atmosphere.

The ablators on the spacecraft were welded into place using a specialized metal that would withstand great heat.