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While reading about Saturn launch vehicle family, I read that Saturn 1 third stage used 2# RL 10 engines, producing a total thrust of 30K Pounds.

But each RL 10, individually produced approx 25K pounds of thrust. If two of these were used in Saturn 1 third stage, why total thrust of 3rd stage is said to be only 30 K pounds and not about 50 K pounds.

Similar is the case with S1 second stage. It used 6# of RL 10 (@ 25 K Lbf each), but total thrust of 2nd stage of S1 is only 90K Lbf and not 125 K. WHY so?

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    $\begingroup$ You have asked many questions which have recieved good answers. Consider accepting some of those answers. $\endgroup$ – Organic Marble Jul 12 at 12:05
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    $\begingroup$ I am not an admin/moderator. Moderators have a diamond by their user name. If your question receives an answer that you feel is correct, you should mark it as "accepted" by clicking the gray check mark beside the answer. I think your questions are mostly interesting. I won't mention it again, I just thought you might be unaware of how the site works. $\endgroup$ – Organic Marble Jul 12 at 15:20
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    $\begingroup$ @Niranjan: Organic Marble is not saying that you should not ask questions. In normal conversation "accept an answer" can also mean "don't ask all these questions", but here it simply means to click a button next to the answer that you like best. It helps other persons with the same question to find the best answer. $\endgroup$ – PA71 Jul 12 at 16:46
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    $\begingroup$ @Niranjan Accepting an answer is a specific action on this site. As question author, you can see a gray check mark to the left of the answer. You can click on that to mark an answer as helpful to you. This shows to other users that the answer was satisfactory to you and affords some reputation to the asker. Its is considered common courtesy on this site to accept answers in this way if you found them helpful. Most of your questions were well received, so please ask more. Note that Stack Exchange is self-moderated by the users, with the help of a few elected diamnond-moderators. $\endgroup$ – Polygnome Jul 12 at 17:24
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    $\begingroup$ @ - Organic Marble, PA71 and Polygnome...OK. Now I have understood what OM wanted to say. Will surely "accept" henceforth. PA71, you have rightly pointed out my pain in interpreting the style of English used here. Now I realize there is nothing offending in any remark. Polygnome, thanks for sharing the two sites. I will visit these for better understanding of the structure of this site. Thank you everyone. $\endgroup$ – Niranjan Jul 12 at 18:11
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There were different versions of the RL 10 engine with different thrusts.

The retired RL10A-1, first flown 1962 had a thrust of 67 kN (15,000 lbf).

The active RL10B-2, first flown 1998 has a thrust of 110.1 kN (24,800 lbf)

The RL10B-2 engine is very different to the RL10A-1, it is much heavier, longer and has a much larger diameter.

The third stage of Saturn I used two engines and the total thrust was 133 kN (30,000 lbf). But this stage was never flown. It was essentially the Centaur rocket as Russell Borogove commented.

The second stage of Saturn I used six engines and the total thrust was 400 kN (90,000 lbf).

So if we use the old RL10A-1 engine version thrust values the numbers fit well.

All numbers from Wikipedia, Saturn I and RL 10.

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  • $\begingroup$ Very clear answer (explaining about thrusts of RL10A-1, and RL10B-2). By the way, since my such doubts are more of "overall" nature, I generally tend to ignore specific details like {K=1024 / k=1000}. Please excuse me for ignoring such micro level details. Thanks a lot. I appreciate your prompt and "to the point" responses. $\endgroup$ – Niranjan Jul 12 at 14:44
  • $\begingroup$ @Organic Marble: You have repeated your comment. You commented same thing last time also. I fail to understand what is it that you wish to convey? Are you an administrator of the site? Do you not like/prefer my questions? If you are an administrator, and do not want me to post my questions / doubts on this site, let me know. I will stop. I found this site a few years back and got responses to my doubts. I think its a good site for knowledge sharing. If not so, I will quit. $\endgroup$ – Niranjan Jul 12 at 14:50
  • $\begingroup$ I am not an admin/moderator. Moderators have a diamond by their user name. If your question receives an answer that you feel is correct, you should mark it as "accepted" by clicking the gray check mark beside the answer. I think your questions are mostly interesting. I won't mention it again, I just thought you might be unaware of how the site works. $\endgroup$ – Organic Marble Jul 12 at 15:20
  • $\begingroup$ The Saturn I never had a third stage; the S-V stage that was proposed as a third stage was essentially the Centaur . $\endgroup$ – Russell Borogove Jul 12 at 15:56
  • $\begingroup$ @RussellBorogove The Wikipedia article mentions a unflown third stage. $\endgroup$ – Uwe Jul 12 at 16:04

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