# Do the engines of an Energia core stage gimbal? **URL:** \ **Category:** Factual Questions\ **Created:** [December 7, 2004, 2:19am UTC](https://boards.straightdope.com/t/do-the-engines-of-an-energia-core-stage-gimbal/278474 "2004-12-07T02:19:38Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Ranchoth](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranchoth/32/1066_2.png) [@Ranchoth](https://boards.straightdope.com/u/Ranchoth)\ **Post date:** [December 7, 2004, 2:19am UTC](https://boards.straightdope.com/t/do-the-engines-of-an-energia-core-stage-gimbal/278474/1 "2004-12-07T02:19:38Z")
Kind of an odd, obscure technical question, but…does anyone happen to know if the engines of a Russian [Energia rocket core stage](http://www.astronautix.com/engines/rd0120.htm) “gimbal,” for attitude control? I understand that the [Energia _strapon_ stages](http://www.astronautix.com/stages/enerapon.htm) do gimbal a few degrees, but I don’t know about the core. That’s…it, I think. Can anyone help me out? Is there a rocket scientist in the house? ---
**Author:** ![PaulFitzroy](https://avatars.discourse-cdn.com/v4/letter/p/2acd7d/32.png) [@PaulFitzroy](https://boards.straightdope.com/u/PaulFitzroy)\ **Post date:** [December 7, 2004, 2:25am UTC](https://boards.straightdope.com/t/do-the-engines-of-an-energia-core-stage-gimbal/278474/2 "2004-12-07T02:25:29Z")
I don’t know about yours, but my strapon never gimbels. ---
**Author:** ![Fritz](https://avatars.discourse-cdn.com/v4/letter/f/c57346/32.png) [@Fritz](https://boards.straightdope.com/u/Fritz)\ **Post date:** [December 7, 2004, 5:33am UTC](https://boards.straightdope.com/t/do-the-engines-of-an-energia-core-stage-gimbal/278474/3 "2004-12-07T05:33:37Z")
> [@PaulFitzroy](#): > > I don’t know about yours, but my strapon never gimbels. I certainly don’t need a strapon, but I do gimbel… ---
**Author:** ![Jurph](https://avatars.discourse-cdn.com/v4/letter/j/50afbb/32.png) [@Jurph](https://boards.straightdope.com/u/Jurph)\ **Post date:** [December 7, 2004, 4:06pm UTC](https://boards.straightdope.com/t/do-the-engines-of-an-energia-core-stage-gimbal/278474/4 "2004-12-07T16:06:44Z")
I did a stint as a rocket scientist at my last job, and even learned a little about Former Soviet/Russian space launch vehicles. I’m going to poke around today and see what I can find, but if I can’t find anything online, I might be able to put in a FOIA request to the right folks and get you an answer. Any reason you’re researching the Energia? ---
**Author:** ![Jurph](https://avatars.discourse-cdn.com/v4/letter/j/50afbb/32.png) [@Jurph](https://boards.straightdope.com/u/Jurph)\ **Post date:** [December 7, 2004, 4:11pm UTC](https://boards.straightdope.com/t/do-the-engines-of-an-energia-core-stage-gimbal/278474/5 "2004-12-07T16:11:25Z")
Aha! Here you are. The answer is “yes”. > [@Korolev Design Bureau PR Text](#): > > In the ascent phase, LV is controlled and stabilized through a **thrust vector deflection of engines of stages I and II in two planes.** For this, the engine gimbals and high precision vernier thrusters are provided to gimbal each engine of stage II and four engine chambers of stage I. The vernier thrusters are sized to about 50 tf for stage I and 33 tf for stage II and to an accuracy of 1% from the thrusters motion spectrum. How’s that for you? ---
**Author:** ![Ranchoth](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranchoth/32/1066_2.png) [@Ranchoth](https://boards.straightdope.com/u/Ranchoth)\ **Post date:** [December 7, 2004, 9:18pm UTC](https://boards.straightdope.com/t/do-the-engines-of-an-energia-core-stage-gimbal/278474/6 "2004-12-07T21:18:02Z")
> [@Jurph](#): > > How’s that for you? Perfect! Thank you. And I’m researching the Energia because I’m building a Buran-Energia for the flight simulator I use, “X-Plane.” It should be pretty accurate. Thanks again! Ranchoth ---
**Author:** ![pilot141](https://avatars.discourse-cdn.com/v4/letter/p/e0b2c6/32.png) [@pilot141](https://boards.straightdope.com/u/pilot141)\ **Post date:** [December 8, 2004, 6:15am UTC](https://boards.straightdope.com/t/do-the-engines-of-an-energia-core-stage-gimbal/278474/7 "2004-12-08T06:15:42Z")
Just have to say that the SDMB rocks. First off, the question could only be asked on a very limited number of message boards, and all of the others would be serious tech-heavy only boards. But it showed up here, and I read the OP and thought “Huh…I never really thought about that, but my guess would be yes. Dammit, now I want to know!” And sure enough, someone knows! 🆒 ---
**Author:** ![Jurph](https://avatars.discourse-cdn.com/v4/letter/j/50afbb/32.png) [@Jurph](https://boards.straightdope.com/u/Jurph)\ **Post date:** [December 8, 2004, 3:55pm UTC](https://boards.straightdope.com/t/do-the-engines-of-an-energia-core-stage-gimbal/278474/8 "2004-12-08T15:55:10Z")
I will also raise a mug to the SDMB, because when I saw the question, my first instinct was “Well I’m a rocket scientist. And I know a lot about Russian space launch vehicles. I should try to help him out – _I hope someone else doesn’t get to it first!_” There aren’t many boards where this could get answered, and I think the SDMB is the only place where I thought I’d be late with the answer. By the way, the “tf” mentioned above, if you didn’t get it from context, is angular degrees – so the core stage gimbals 33 degrees off-center in increments of .066 or .033 degrees, and the strap-ons gimbal 50 degrees in increments of 1 or 0.5 degrees. It’s unclear whether an engine can gimbal “inside” the centerline – that is, can the top-left-side main engine direct its thrust down or to the right, or can it only swing outward 33 degrees? This has a direct bearing (ha ha) on what you use as the basis for the 1% vernier precision figure. Not sure how accurately you intend to model the control system, but your initial question seems like you want as much meat as you can get. BTW, I checked out your homepage with the simulator – cool stuff! ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [December 8, 2004, 4:22pm UTC](https://boards.straightdope.com/t/do-the-engines-of-an-energia-core-stage-gimbal/278474/9 "2004-12-08T16:22:21Z")
> [@Jurph](#): > > By the way, the “tf” mentioned above, if you didn’t get it from context, is angular degrees – so the core stage gimbals 33 degrees off-center in increments of .066 or .033 degrees, and the strap-ons gimbal 50 degrees in increments of 1 or 0.5 degrees. Are you sure? It sounds to me the 30 tf and 50 tf are thrust ratings for the vernier thrusters. IIRC, **tf** = ton force, or something like that. But this passage is confusing me: “…high precision vernier thrusters are provided to gimbal each engine of stage II and four engine chambers of stage I.” Does that mean the gimbals move freely and controlled by jets, rather than activated by hydraulics?