LOR
Although the basics of the LOR concept had been expressed as early 1916 by Yuri Kondratyuk and 1923 by German rocket pioneer Hermann Oberth, NASA would provide the first practical application of the concept. Some engineers were concerned about the risks of space rendezvous, especially in lunar orbit, where there would be no fallback options in case of a major mishap. Houbolt had presented the LOR concept to a series of panels.
Houbolt has a scheme that has a 50 percent chance of getting a man to the moon and a 1 percent of getting him back.
Max Faget:
His figures lie, he doesn't know what he's talking about.
After many technical conferences debating Direct ascent, Earth orbit rendezvous, and LOR, Werner von Braun supported the concept.
While some aspects of Houbolt's initial proposal were not realistic (such as a 10,000 pound Apollo Lunar Module which was ultimately 30,000 pounds), his LOR package proved to be feasible with a single Saturn V rocket whereas other modes would have required two or more such rocket launches (or larger rockets than were then available) to lift enough mass into space to complete the mission.
Read more about this topic: John Houbolt