Lunar orbit rendezvous
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Lunar Orbit Rendezvous was the method of flying to the moon used in the Apollo Missions, where a main ship would carry a ferry to the moon which would carry astronauts down to the surface. This "mode" of moon landing was one of three modes that were theories on how to land on the moon.
The first was direct ascent, which is exactly how it sounds. A huge rocket (called "Nova") launches into space and lands on the moon.
The second was earth orbit rendezvous, where two smaller rockets launch the capsule with the astronauts and a fuel tank. The astronauts would meet with the fuel tank in orbit, fill up the capsule and depart Earth orbit for the moon.
The third mode was Lunar Orbit Rendezvous, a plan developed by a team led by John C. Houbolt. In this mode, a rocket launches the capsule with the astronauts and a lunar lander, known as the "lunar excursion module"(LEM). When the astronauts reach lunar orbit, the LEM undocks from the command module (capsule) and descends to the surface of the moon. One astronaut of three remains in the command module which orbits the moon. The astronauts that have landed on the moon re-launch using an ascent stage of the LEM and re-join with the command module which is orbiting the moon to return to the earth.
Upon return to Earth, the command and service modules separate, leaving the command module to plunge into the Earth's atmosphere at a velocity of 25,000 mph.
Dr. John Houbolt, would not let the advantages of LOR be ignored. As a member of Lunar Mission Steering Group, Houbolt had been studying various technical aspects of space rendezvous since 1959 and was convinced, like several others at Langley Research Center, that LOR was not only the most feasible way to make it to the moon before the decade was out, it was the only way. He had reported his findings to NASA on various occasions but felt strongly that the internal task forces (to which he made presentations) were following arbitrarily established "ground rules." According to Houbolt, these ground rules were constraining NASA's thinking about the lunar mission -- and causing LOR to be ruled out before it was fairly considered.
Lunar-orbit rendezvous required docking the lunar module with the command module in lunar orbit. Astronauts practiced the complex task of separating and uniting spacecraft to master docking techniques with Langley's Rendezvous and Docking Simulator, today a National Historic Landmark.
In November 1961, Houbolt took the bold step of skipping proper channels and writing a private letter, nine pages long, directly to Robert C. Seamans, the associate administrator. "Somewhat as a voice in the wilderness," Houbolt protested LOR's exclusion. "Do we want to go to the moon or not?" the Langley engineer asked. "Why is Nova, with its ponderous size simply just accepted, and why is a much less grandiose scheme involving rendezvous ostracized or put on the defensive? I fully realize that contacting you in this manner is somewhat unorthodox," Houbolt admitted, "but the issues at stake are crucial enough to us all that an unusual course is warranted."
It took two weeks for Seamans to reply to Houbolt's extraordinary letter. The associate administrator agreed that "it would be extremely harmful to our organization and to the country if our qualified staff were unduly limited by restrictive guidelines." He assured Houbolt that NASA would in the future be paying more attention to LOR than it had up to this time.
In the following months, NASA did just that, and to the surprise of many both inside and outside the agency, the darkhorse candidate, LOR, quickly became the front runner. Several factors decided the issue in its favor. First, there was growing disenchantment with the idea of direct ascent due to the time and money it was going to take to develop the huge Nova rocket. Second, there was increasing technical apprehension over how the relatively large spacecraft demanded even by Earth-orbit rendezvous would be able to maneuver to a soft landing on the moon. As one NASA engineer who changed his mind explained: "The business of eye balling that thing down to the moon really didn't have a satisfactory answer. The best thing about LOR was that it allowed us to build a separate vehicle for landing."
The first major group to break camp in favor of LOR was Robert Gilruth's Space Task Group, which was still located at Langley but was soon to move to Houston. The second to come over was the Von Braun team at the Marshall Space Flight Center in Huntsville, Alabama. Then these two powerful groups of converts, along with the original true believers at Langley, persuaded key officials at NASA Headquarters, notably Administrator James Webb, who had been holding out for direct ascent, that LOR was the only way to land on the moon by 1969. With the key players inside NASA lined up behind the concept, Webb approved LOR in July 1962. He did it even though President Kennedy's science advisor, Jerome Wiesner, remained firmly opposed to LOR.
Whether NASA's choice of LOR would have been made in the summer of 1962 or at any later time without the research information, the commitment, and the crusading zeal of Houbolt and his associates at NASA Langley is a matter for historical conjecture. However, the basic contribution made by the Langley researchers is beyond debate. They were the first in NASA to recognize the fundamental advantages of the LOR concept, and for a critical period of time in the early 1960s they were also the only ones inside of the agency to foster it and fight for it.
Thousands of factors contributed to the ultimate success of Apollo, but no single factor was more essential than the concept of lunar-orbit rendezvous. Without NASA's adoption of this stubbornly-held minority opinion, we may still have gotten to the moon, but almost certainly it would not have been accomplished by the end of the decade, as President Kennedy had wanted.
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