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I was wondering if thrust vectoring via a maneuvering gimballed nozzle affected the thrust of a rocket. I've read a couple times that a gimballed rocket engine's thrust doesn't change while exhaust vanes do, (I imagine they're similar to how an aerodynamic control surface works).

It seems logical to me that a gimballed nozzle shouldn't affect thrust of rocket when deflecting the exhaust, however I am unable to find anything that states this.

It also seems that gimballed nozzles are used on solid fueled rockets, and not on liquid fueled ones. I'm assuming gimballing a solid fueled rocket engine would not be possible due to the propellant basically being the combustion chamber?

In short: do gimballed nozzles have any effect on raw thrust output? If not, why aren't they used on liquid fueled rockets?

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    $\begingroup$ Are you making a distinction between gimballing just the nozzle and gimballing the whole engine? $\endgroup$ Aug 24, 2022 at 18:25
  • $\begingroup$ "gimballed nozzles are used on solid fuelled rockets and not on liquid fulled ones". is this a typo? $\endgroup$
    – Woody
    Aug 24, 2022 at 19:37
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    $\begingroup$ Are you asking about the thrust measured along the nozzle's axis or the rocket's axis? They will differ by the cosine of the angle, and so give different answers to your question. $\endgroup$
    – Woody
    Aug 24, 2022 at 19:42

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Gimbaling a nozzle is not that easy - you have to handle high loads, temperatures and pressures. So on liquid engines the hole engine is gimballed, not only the nozzle. Solid engines are "a bit too large" for that - so you need to gimbal the nozzle. (or use other methods for thrust vectoring)

Vanes do create quite a significant drag in the rocket exhaust, so they suffer a higher impact on the thrust than other methods - so they were discontinued quite early (except on some amateur rockets - where the mechanical simplicity still is an advantage)

But all thrust vectoring does have an impact on the performance of the vehicle. But it is quite low for gimballed engines so one can nearly disregard it. The change in the axial thrust is cos(alpha) which won't change much in the few degrees of rotation. But it still takes power to move the engine around - and it also adds some weight.

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  • $\begingroup$ Could you add a source for the added drag of vanes? As well as a source on the impact/added weight of thrust vectoring for gimballed engines? I don't wanna sound like I'm complaining; I love your answer, but without any outside sources it's impossible to verify the accuracy of it. thx :) $\endgroup$ Aug 26, 2022 at 16:59
  • $\begingroup$ @DakotaWharton some numbers for Isp loss due to the vanes here space.stackexchange.com/a/50647/6944 $\endgroup$ Aug 26, 2022 at 17:39
  • $\begingroup$ thanks for your reply, so is a gimballed engine on a liquid fuelled rocket "easier" to implement than a gimballed nozzle and hence the lack of gimbaling nozzles on liquid fuelled rockets? $\endgroup$ Sep 5, 2022 at 6:51

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