Well, you are going to have to modify the S-IVB to carry more fuel and last all of the way to the moon, aren't you? You will need a bigger LOI engine, and it might as well be the S-IVB, extended for 3 burns, not 2.<br /><br />And, if it can do that, it might as well be your ETO engine as well, meaning that the SM is not really needed, right? So the S-IVB needs to loft only the CM. <br /><br />Eventually, you might be able to come up with a system where the IVB is extremely long-lived, capable of say, 20 LTO-LOI-ETO-EOI sequences. Could the S-I loft the CM and a refueler for the S-IVB? <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>