Space Shuttle

The stack was three machines. Two recoverable solid-rocket boosters - fished out of the ocean, refurbished, reflown up to fourteen times, about 83% of thrust at liftoff. One aluminium external tank: the only major part that never flew twice, and precisely where the fully-reusable economics died. And the orbiter itself, a rocket-powered glider that took just over 24 tonnes to orbit on liquid hydrogen. Coming home was always a dead-stick landing: no engine with which to go around, some 24,000 ceramic tiles holding back 1,200-degree heat, touchdown near 350 km/h on a glide path with no missed approach. The wings only slowed the descent; the heat shield did the real work. In orbit the design justified itself: no other vehicle has delivered and assembled the ISS, or captured, repaired and upgraded Hubble with astronaut spacewalks. Both losses are in the ledger - Challenger 1986, Columbia 2003, fourteen crew - and both traced to engineering specifics, an O-ring and a foam strike, not to the idea itself.