Yeh, at Main Engine Cutoff, the stack’s trajectory was still sub-orbital, so that when they detached the main tank, it would re-enter ballistically without having to maneuver. Then the orbiter’s OMS engines would make the final push to orbit.
Yep. Those propellants are why shuttle landings involved everyone standing off at a distance until they could tow a wind machine into place, and then guys in hazmat suits would approach from upwind to check for leaks.
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The engines – Aerojet AJ-10 — are classics, having first flown in 1958. They were used on a whole bunch of upper stages, and also as the Apollo Service Module’s main engine.
Some shuttle OMS engines will actually be reused as the Orion spacecraft’s Service Module main engine. NASA has been removing both the RS-25 main engines and the AJ-10 OMS engines from the museum-piece shuttles and recycling them as use-once-and-throw-away disposables for the SLS/Orion program.
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