WELDING crews began sealing cracks in the main engines of NASA’s entire shuttle fleet this week. Repairs to the first, Atlantis, could be completed by the weekend.
NASA grounded its fleet of shuttles in June after a routine inspection of Atlantis revealed small cracks in liners that channel liquid hydrogen fuel into the main engine (Â鶹´«Ã½, 6 July, p 5). The thin tubular liners, made from a nickel alloy called Inconel 718, are fixed inside steel fuel pipes to smooth the flow of propellant into the engine. Each liner is perforated with holes to ensure that the propellant…
