Using booster for TLI? | Propulsion Workgroup | Forum

Last night I learned that the Apollo spacecraft actually used the final stage of their Saturn V booster (which was a re-startable engine) to perform their trans lunar injection burn.  I had always just assumed they used the service module engine for this.

Since we seem to be slightly inclined toward solid fuel for simplicity's sake, we won't be able to restart our final stage while in parking orbit.  This means we'll either need effectively a forth stage to our booster, for TLI use, or we'll have to use our service module engine for both TLI and TEI, meaning our SM will need *double* the delta-v budget of Apollo's.  Of course, that might not be so severe a problem, since our CSM will weigh a lot less than theirs, but it still doesn't exactly sound great.

Any thoughts on which of these options would be best?

Ah, yes.  Not quite double the delta-v, then, but significantly more.  But, due to the reduced crew size and lack of a LEM, I suppose our CSM should be so much lighter that this is managable.

I saw your other post containing data on commercial options – good work.  I think it is worth keeping this in mind at all times.  We should only go with the custom booster option if we really think we can save a considerable amount of money without compromising too much on quality/reliability.