Neil Armstrong was the first man to walk on the moon. John C. Houbolt might be the man who got him there on time. The former NASA engineer and chief proponent of Lunar Orbit Rendezvous has died at the age of 95.
Houbolt tirelessly advocated the Lunar Orbit Rendezvous (LOR) mode of lunar landing. In the process, he set the stage for the fabled Saturn V to become our primary moon rocket and enabled the rescue of the Apollo 13 astronauts after their craft suffered a catastrophic failure in space.
In the early 60s, the leading strategies for a lunar landing were
1. Direct ascent: Create a huge rocket (much larger then the Saturn V), fly it directly to the moon and land.
2. Earth orbit rendezvous: Launch two rockets into earth orbit. One would carry the crew and moon rocket. The other would carry fuel for trip to the moon. The crew ship would fuel up in orbit, then complete the mission in more or less the same manner as a direct ascent mission.
3. Lunar orbit rendezvous: Launch a multi-module lunar ship from earth that, on reaching the moon, would send a lander/ascent stage to the moon. After the surface mission was complete, the ascent stage would rendezvous with the orbiting command module and return to earth.
Others at NASA had shied away from the LOR mode because of the complexity of performing a rendezvous in lunar orbit and a lack of redundancy in key systems. Houbolt believed that the risks could be minimized and that LOR was the only approach that could be accomplished in NASA's aggressive time frame. With LOR, the Saturn V could take the place of the massive NOVA rocket proposed for direct ascent, saving both money and time.