Jan 172021
An exploded view of the Marquardt ramjet engine that powered the Lockheed D-21B. The engine was derived from the ramjet that powered the Bomarc missile; interestingly, it went from a SAM engine that ran for at most fifteen minutes to a continent-crossing drone engine that ran for an hour and a half. The D-21 program was riddled with failures, but the engine was not a real source of trouble. What did become a minor source of trouble: after the seventeen surviving D-21s were mothballed, the nosecones of the engines had to be specially removed: being made of a thorium alloy, they were slightly radioactive.
