Water Well Journal
Issue link: http://read.dmtmag.com/i/740475
turned out to be a needed watershed mo- ment in space exploration, helping chart our path to the moon. But how do we get there? Another person who played quite a pivotal role in landing on the moon was John Houbolt, an aerospace engineer. In the early days of the Apollo pro- gram, fierce debate raged as to the best way to travel to and land on the moon. In the beginning, many engineers favored the more commonly accepted methods of using either direct ascent or earth orbit rendezvous as the only way to land on the moon (Figure 2). In direct ascent, a single rocket ship would be launched, transported to the moon, land, and then relaunch and re- turn to Earth. The proposed rocket ship was up to 100 feet in height for storage of the fuel and oxidizer and required an elevator-type device to transport the astronauts down to the moon's surface and back up into the mother ship. The proposed vehicle would consist of an enormous rocket, much larger than the Saturn V (then under development). In earth orbit rendezvous, the pro- gram would have called for at least two launches needed to assemble both crafts in earth orbit: one the direct-landing vehicle, the other the return vehicle. In virtually no realm at the time was the possible choice of a lunar orbit ren- dezvous ever considered. During the early 1960s, it appeared either direct as- cent or earth orbit rendezvous would be selected the way to go to the moon, ig- noring the costs and lack of feasibility. This is when Houbolt, who had been in- dependently evaluating both proposed methods, suggested a third but often ignored approach—lunar orbit ren- dezvous—be adopted, not only as one way to land on the moon, but as the only practical way to get to the moon. For Houbolt, it all came down to weight and keeping the weight as low as possible. The lower you can keep the weight of the rocket itself and its com- ponents, the less fuel it would require. In lunar orbit rendezvous (Figure 3), a command module, where three astro- nauts would ride to the moon and back to Earth, would be connected to a serv- ice module housing the needed consum- ables such as water, fuel, and oxygen for use during the mission. The command module and service module would be docked to a lunar excursion module (LEM) all the way to the moon and un- dock just before the LEM made the de- scent to the surface of the moon. The LEM would land on the moon, support two astronauts on the moon for the en- tire lunar stay, and then ascend and dock with the command module for the trip back to Earth, subsequently disposing of the LEM in lunar orbit. When proposing this idea to the pow- ers-that-be, Houbolt received an almost unanimous outcry: "But this would mean the astronauts would have to un- dock and then dock again in space— around the moon no less!" At the time this had not even been envisioned or accomplished in earth orbit. In a typical engineer's response, Houbolt and his supporters retorted, "Sure they will need to dock in space, but astronauts are smart people. They will figure it out." The solution was obviously some- what more involved than that and re- quired years of extensive training and a plethora of new and old technologies, such as tracking radar and celestial navi- gation. But Houbolt was vindicated. Lunar orbit rendezvous would be used on every manned mission. What if they get lost? Although the distance varies, the mean distance between Earth and the moon averages around 250,000 miles. Knowing both are in constant rotation and travelling through space at the same time required some more planning than the attitude that "We will simply point our rocket ship to the moon." In fact, knowing this represented the most criti- cal aspect of the entire Apollo program, the first contract NASA awarded for the Apollo program was to the Massachu- setts Institute of Technology (MIT) for the guidance system to enable and chart the trip to the moon and back. This is where our next notable person comes in, Dr. Charles Stark "Doc" Draper. He was an accomplished American scientist and engineer, known as the "father of inertial navigation." He was also the founder and director of the MIT Instrumentation Laboratory, later renamed the Charles Stark Draper Lab- oratory, which made the Apollo moon landings possible through its Apollo guidance computer. The guidance computer used for each moon landing was truly a rudimentary, although ingenious, machine with lim- ited memory and computing function. In fact, today's handheld calculators and iPads have more computing ability than ENGINEERING from page 60 Figure 1. The Saturn V rocket. waterwelljournal.com Figure 2. The early Apollo configuration for direct ascent and earth orbit rendezvous. 62 November 2016 WWJ