VTVL with long and thin body have a difficult time in obtaining stability during landing. Watch this failed SpaceX rocket landing for example:

Why can't they use "dampers" used in tall high rise building which provide them stability during rough weather?

I understand dampers could mean extra weight and more real estate consumption within the rocket. However, there could be a possibility of using rocket's internal components itself like dampers.


1 Answer 1


If you have a large weight above the center of gravity, and the stage gets off-vertical a little, that large weight now exerts a torque that pulls the rocket off-vertical some more. A weight at the top is only viable if the deviations you are trying to connect are very small (like a 100-m building swaying 1-2 meters in high winds). But the stage needs to be able to fly at large angles, as your video shows.

A large weight at the bottom of the stage would be better, and it's the only place where you already have a large weight, i.e. the engines. But to make that work, you'd need to make the engines movable relative to the rest of the stage. Given the huge forces involved, that would mean a heavy structure. The rocket only has a few tons of payload, this would reduced that significantly.

Your idea was looked at by SpaceX for the Dragon at some point: it was to use a movable weight to orient the capsule during reentry.

  • $\begingroup$ Thanks Hobbes. I am trying to create very small models of vertical rockets to test their stability. At some point I also want to try with gyroscope, albeit it has several variables. $\endgroup$
    – jerrymouse
    Oct 27, 2018 at 17:07
  • $\begingroup$ You could install 2 ducted fans at the top, along the X and Y axis (able to run in both directions) and use them as thrusters. On a small model, these can provide more than enough power to keep the stage upright, and they work in a much larger range of attitudes than a sliding weight. $\endgroup$
    – Hobbes
    Oct 27, 2018 at 17:17

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