原推：@PPathole @Erdayastronaut @SpaceX @Caspar_Stanley @IzanRamos2002 Some small tubes & wiring need to be nested in a bigger tube for thermal protection, kinda like conduit in a house.
Engines themselves & booster base are extremely robust. High strength stainless steel is bulletproof to a handgun at ~2.5mm thickness. Booster dome is 4mm.
https://twitter.com/elonmusk/status/1547769955327680513