This has to do with the details of lunar travel, and more specifically current NASA plans for lunar travel with project Constellation.<br /><br />Background<br /><br />NASA has chosen the so-called '1.5 launch' (really 2 launch) Earth Orbit Rendezvous (EOR) plus Lunar Orbit Rendezvous (LOR) architecture for lunar travel. The CEV will return to Earth straight from a polar low lunar orbit. Because the capsule Crew Module (CM) will recover on land inside the United States, the CM must do a skip-reentry to reach the higher lattitude of the preferred landing zone.<br /><br />The Issue<br /><br />Many other options have been proposed, most often substituting Langrange Point Rendezvous (LPR) at either EML-1 or EML-2 for the NASA plan of LOR. I'm interested at comparing those rendezvous options. For shorthand I will refer to EML-1 LPR as LPR-1 and EML-2 LPR as LPR-2.<br /><br />Questions<br /><br />1) I have heard that LPR-1 permits anytime Earth return and to any Earth latitude. Is this also true for LPR-2?<br /><br />2) What is the difference in Earth return travel time and Earth re-entry velocity between LPR-1, LOR and LPR-2? Does LPR-1 provide a significant bonus in lower re-entry velocity compared to LPR-2?<br /><br />3) Detail of delta-V differences between LPR-1, LOR and LPR-2?