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Short · Rockets

When should a falling rocket light its engine?

A returning Falcon 9 booster cannot hover when its minimum thrust exceeds its landing weight. In the teaching model, one ignition height removes its speed exactly at the pad.

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Narrated · 35 seconds · captions includedDownload the film

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Transcript

When should a falling rocket light its engine? A returning Falcon Nine booster can't hover. Even at its lowest setting, its engine pushes harder than its weight. Light too early, and it stops in mid-air, then starts climbing again. Light too late, and it hits the ground. Now move the ignition point. Only one height brings it to zero speed, right at the pad. Fans call it the hover slam, and every Falcon Nine landing depends on getting it right. Try it yourself at Explainer Tools dot com.