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SpaceX Landing Platform video: why is the rocket moving so fast?

up vote 14 down vote favorite

This is the video of the Falcon 9 first stage attempting a landing on SpaceX's barge. Why is the rocket moving so fast at impact?

2 Answers

up vote 4 down vote accept

The Falcon 9 can't hover--even one engine at minimum is too much thrust. Thus it must do what KSP calls a suicide burn.

up vote 3 down vote

It is actually moving quite slow vertically. It's speed comes from the horizontal component -- which is a result of the vehicle trying (unsuccessfully) to correct its horizontal position. The vehicle was unable to accomplish this with the aerodynamic control surfaces as intended. The control surfaces that were responsible for this ran out of hydraulic fluid.


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SpaceX Landing Platform video: why is the rocket moving so fast?

up vote 14 down vote

This is the video of the Falcon 9 first stage attempting a landing on SpaceX's barge. Why is the rocket moving so fast at impact?


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up vote 9 down vote

The Falcon 9 can't hover--even one engine at minimum is too much thrust. Thus it must do what KSP calls a suicide burn.

edit

SpaceX calls it a "hover slam". - geoffc Jan 17 '15 at 23:41

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