Perseverance, NASA's latest Mars rover, is a one-ton, $2 billion marvel. The plan was for it to enter the Mars atmosphere going 12,000 miles an hour. The problem: How do you slow it down enough to set it down gently on the surface? You can't use retro rockets, because they'd stir up so much dust, the rover’s cameras and instruments would be ruined. You can’t deliver Perseverance inside a larger spaceship, because the rover wouldn’t be able to drive out of the landing crater. You can’t even control the descent from Earth, because it takes so long for our signals to reach Mars; by the time the rover received a course-correction instruction, there’d be nothing left of it but a smoking wreck. Yet NASA pulled it off—with a nutty, Rube Goldberg-y, multi-stage, seven-minute-long, completely automated system involving a parachute, an airborne launch platform, and a cable.

Guest: Alan Chen, NASA Entry, Descent, and Landing Lead for the Mars 2020 mission.

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