head, to regulate pressure, rate of propellant flow, and the pattern of fuel mixture in the combustion chamber. The first full-throttle firing of Space Technology Laboratories' LM descent engine was carried out in early 1964. NASA planners expected one of the two drastically different designs would emerge the clear winner, but this did not happen throughout 1964. Apollo Spacecraft Program Office manager Joseph Shea formed a committee of NASA, Grumman and Air Force propulsion experts, chaired by American spacecraft designer Maxime Faget, in November 1964 to recommend a choice, but their results were inconclusive. Grumman chose Rocketdyne on January 5, 1965. Still not satisfied, MSC Director Robert R. Gilruth convened his own five-member board, also chaired by Faget, which reversed Grumman's decision on January 18 and awarded the contract to STL. To keep the DPS as simple, lightweight, and reliable as possible, the propellants were pressure-fed with helium gas instead of using heavy, complicated, and failure-prone turbopumps. Cryogenic supercritical helium was loaded and stored at 3500 psi. The helium was pressure regulated down to 246 psi for the propellant tanks. Pressure from the helium would gradually rise as it warmed and would eventually be vented. The system was also equipped with a rubber diaphragm that would burst when the helium pressure reached a certain level and allow the gas to vent harmlessly into space. Once the helium was gone however, the DPS would no longer be operable. This was not seen as an issue since normally, the helium release would not occur until after the lunar module was on the Moon, by which time the DPS had completed its operational life and would never be fired again. The design and development of the innovative thrust chamber and pintle design is credited to TRW Aerospace Engineer Gerard W. Elverum Jr. The engine could throttle between and but operation between 65% and 92.5% thrust was avoided to prevent excessive nozzle erosion. It weighed , with a length of and diameter of . Performance in LM "life boat" The LMDE achieved a prominent role in the Apollo 13 mission, serving as the primary propulsion engine after the oxygen tank explosion in the Apollo Service Module. After this event, the ground controllers decided that the Service Propulsion System could no longer be operated safely, leaving the DPS engine in Aquarius as the only means of maneuvering Apollo 13. Modification for Extended Lunar Module In