The solid boosters of Shuttle/SLS fly in pairs. Could a pair of them fly without SLS, carrying a smaller second stage and payload to orbit? What capacity would it have?

A rescue launcher needs to launch on short notice, hence solid first stage. The second stage still has to be fueled. The prepared payload could be a space tug that for example could prevent a predicted debris collision in LEO from happening.

  • $\begingroup$ Predicted debris collision in LEO isn't currently a good rescue mission - we don't track debris accurately enough to make good conjunction predictions. At the time of the Iridium-Cosmos collision the Iridium constellation was getting 400 conjunction notices per week in 2007 and the collision wasn't the closest predicted collision of the day (and I hear some operators get 20k+ notices a week). $\endgroup$
    – 1337joe
    Jul 22, 2015 at 15:44
  • $\begingroup$ Why do you ask? $\endgroup$ Jul 22, 2015 at 20:50
  • $\begingroup$ @RussellBorogove Why? I just found a couple while cleaning up my garage... I guess that a solid launcher standing by on short notice would give more flexibility if something important is misplaced in orbit. $\endgroup$
    – LocalFluff
    Jul 22, 2015 at 21:41
  • 1
    $\begingroup$ It doesn't seem like a great use of a big and relatively fancy SRB. Keeping something like an Athena (en.wikipedia.org/wiki/Athena_II) or Minotaur around might be more sensible, depending on the payload. $\endgroup$ Jul 22, 2015 at 21:59
  • $\begingroup$ I may be an old cynic, but we already have something of this kind: SM-3 ASAT. $\endgroup$ Jul 24, 2015 at 16:47

1 Answer 1


By themselves, a pair of SRBs with no payload would produce about 5500 m/s of ∆v, which gets them something more than half-way to orbit. They have a fairly poor ISP and propellant mass fraction.

If you added a 100-ton second stage using storable hydrazine-family propellants, you could get about 5 tons of payload to LEO if that's your goal.

enter image description here

  • 2
    $\begingroup$ Invisible Second Stage! $\endgroup$ Jul 24, 2015 at 16:20
  • 1
    $\begingroup$ That's some serious stealth for you. NRO has cleared this shot for public release. $\endgroup$ Jul 24, 2015 at 16:44
  • $\begingroup$ "Boss....we forgot something..." $\endgroup$ Jul 24, 2015 at 17:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.