Water Well Journal
Issue link: http://read.dmtmag.com/i/740475
the original Apollo guidance computer! The concept Draper used in develop- ing the basic guidance program was based on the now fundamental concept of inertial guidance. During the 1950s, Draper commissioned a cross-country flight from the east coast of the United States to the west coast—using only a gyroscope and inertial guidance to per- form the needed navigation to keep the plane on course. After a flight of many hours the plane landed safely in Los An- geles, the intended destination, with only minor course corrections automati- cally made during the journey. Today, this seems like old hat tech- nology with most planes now equipped with either autopilot or global position- ing satellite controls, but this was a rev- olutionary method of guidance at the time. In fact, this guidance computer was later instrumental in keeping the command module on course on the way to the moon and the lunar module dur- ing the landing itself. So how are we going to land on the moon? Our fourth often unsung hero of the Apollo program is Thomas Kelly, an engineer for Grumman Corp., the firm that developed the lunar lander. Kelly was an aerospace engineer who mainly worked on jet fighters for the U.S. Air Force but was assigned as chief engi- neer for the LEM (Figure 4) project, which later earned him the name "Father of the Lunar Module." Development of the LEM was not simply a matter of building a space ve- hicle with the capability of setting down on another celestial body. Right from the beginning, a whole host of problems confronted the design team of the LEM. To start with, no manned vehicle had ever been designed or intended to fly through space, land, and then launch from another planet. Besides the obvious lack of aerody- namic considerations due to the fact the LEM was designed to only fly in space, there were other considerations. For in- stance, what was the type and composi- tion of soil the craft would land on? Was it soft and the lander would simply sink into the lunar dust? Was it uneven, vol- canic, and rocky where undue pressure on one of the lander's footpads would cause the craft to tip or turn over? Was it so soft the lander would sink so deep and out of sight a return liftoff could not be performed? Was the soil so corrosive even a stay of only a few hours would result in degradation of the metal pads? These all had to be factored in. Additional considerations included the heat to cold variables experienced from the reverse exposure of sunlight to dark shadows—a possible swing of up to 525°F. In sunlight, the surface tempera- ture on the moon could reach 225°F, while in the dark shadows the tempera- ture extreme could reach a low of –300°F. This extreme variation in tem- peratures required the innovation of many new insulating fabrics and protec- tive coverings, including Mylar—often seen as a gold-colored covering wrapped around the lower half of the lander. As with all other elements of the mis- sion, weight played an important and key factor in the design of the LEM. A critical early design factor by Kelly was the decision to leave behind the lower part of the LEM, with all of its no longer needed and mostly empty landing se- quence engine, fuel and oxidizer tanks, and other unneeded consumables. This would be done by using guillotines to sever the connections between the two portions of the lander and have the lower half act as a launchpad for the upper half, the manned crew compartment. Another important design element overseen by Kelly was the decision to keep the astronauts in a standing posi- ENGINEERING continues on page 64 Figure 3. A lunar flight profile. Twitter @WaterWellJournl WWJ November 2016 63