The Ultimate Geotechnical Engineering Challenge
The Ultimate Geotechnical Engineering Challenge
Edward A. Nowatzki, PE, PhD
Principal Engineer, NCS Consultants, LLC (www.ncsconsultants.com)
After I completed my Ph.D. in July 1966, I took my first “real job” with the Grumman Aircraft Engineering Company in Bethpage, Long Island, New York. Grumman went through a few name changes since that time before becoming part of Northrop Grumman, one of today’s largest defense contractors. Why would a guy with a Ph.D. in civil engineering and a specialization in geotechnical engineering take a job with Grumman, a defense contractor and one of the US Navy’s major contractors for making sophisticated aircraft such as the A-6 “Intruder” and the F-14 “Tomcat”? Well, Grumman was also the National Aeronautics and Space Administration’s (NASA’s) prime contractor for the design and construction of the lunar excursion module (LEM), better known as the lunar module or “LM.”
July 20, 2007 will be the thirty-eighth anniversary of the first time men set foot on the Moon, an event many people believe to be one of the most significant accomplishments of the millennium, despite the fact that some people still believe the whole Apollo program including the lunar landing was staged. I consider myself very fortunate to have been a part of that historic event while I worked for Grumman’s Research Department. This essay contains some recollections of my work on the LM project at Grumman, specifically the geotechnical engineering problems associated with the design of the first lunar lander.
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NASA’s plan for manned lunar exploration consisted of multiple phases, starting with the Ranger Program, followed by the Lunar Orbiter and Surveyor programs and culminating with the Apollo Program, which was the name given to the manned lunar landing program. In 1963 President Kennedy, for political reasons, committed the United States to sending men to the Moon and returning them safely to Earth before the end of the decade (1960s). By doing so he inadvertently compressed NASA’s well conceived plan for lunar exploration into a time frame that diminished the usefulness of much of the data collected on the unmanned projects for the design of the LM.
NASA’s first task was to determine suitable landing sites for the Apollo Program missions since there was a controversy ranging at the time about the thickness of the lunar regolith (surface or “dust” layer). The Ranger Program (1964-65) provided more than 17,000 photographs of the lunar surface at resolutions not previously obtained by earth-based telescopes, but since the spacecraft disintegrated upon impact, those missions provided virtually no information on the thickness of the “dust” that was believed to cover the Moon’s surface. However, photos obtained from the Ranger missions were used to define areas where high resolution photography could be taken from lunar orbiters. The Lunar Orbiter program (1966-67) provided high resolution photography of selected areas of the lunar surface. The goal was to identify candidate sites for further exploration with the intent of selecting sites for the Apollo Program’s manned lunar landings. After candidate landing areas were selected from the orbiter photographs, the Surveyor Program (1966-1968) was launched to obtain scientific and engineering data through the use of unmanned landers that were instrumented to perform in situ tests on the lunar soil. According to NASA’s original plan the data collected from the Surveyor Program would be used directly in the design of the LM. Unfortunately that was not to be the case because of the compressed schedule.
Before going into the geotechnical part of this essay, I believe it would be helpful to present a little background on the US manned space flight program. The Mercury and Gemini programs were going on concurrently with the unmanned programs described above. The main objectives of the six manned flights of the Mercury Program (1961 – 1963) were very specific: (1) to orbit a manned spacecraft around Earth, (2) to investigate man’s ability to function in space and (3) to recover both man and spacecraft safely. The main objectives of the ten missions of the Gemini Program (1965 – 1966) were to learn how to “fly” a spacecraft: (1) by maneuvering it in orbit, (2) by rendezvousing with other vehicles and (3) by docking with other vehicles. In general, the main goals of these pre-cursor programs were to evaluate the performance of astronauts in a zero-gravity environment and to develop and test the systems that would be needed for the eventual manned lunar landing program.
The Apollo Program (1966 – 1972) was the manned lunar landing program. The Apollo spacecraft consisted of three components or “modules,” all of which were integrated into one vehicle for the long journey between the Earth and the Moon, but each of which performed separate functions once the spacecraft went into lunar orbit. The three modules were: (1) the command module (CM), which would stay in orbit around the Moon during the lunar landing and carry the three astronauts back to Earth after completion of the lunar excursion, (2) the lunar module (LM), which, as stated previously, was the module that actually landed on the Moon, and (3) the service module (SM), which was the upper part of the LM until it was time for the two astronauts who had landed on the Moon to return to the CM for the trip back to Earth. The SM separated itself from the LM upon launch from the lunar surface and rendezvoused with the CM orbiting the Moon. The SM was jettisoned after the astronauts, transferred themselves and their cargo of lunar soil and rocks to the CM. The Apollo Program consisted of 11 missions, not including Apollo 1, which resulted in the death of the primary crew in a command module fire during a practice session. The first flight was Apollo 7. Its mission was to test the command and service modules (CSM) in an Earth orbit. It was followed by Apollo 8 whose mission was to test the CSM in a lunar orbit. Then came Apollo 9 and Apollo 10 to test the LM in Earth and lunar orbits, respectively. Apollo 11 was the first attempted and successful lunar landing mission. It was followed by the five other successful landing missions and one attempted but aborted landing mission, Apollo 13. My work at Grumman was primarily in support of the Apollo 11 mission. The following summarizes the main statistics of the Apollo 11 mission:
- Launched: July 16, 1969
- Landed on the Moon: July 20, 1969
- Landing Site: Sea of Tranquility
- Returned to Earth: July 24, 1969
- Command Module: Columbia
- Lunar Module: Eagle
- Neil A. Armstrong, commander
- Edwin E. Aldrin, Jr., lunar module pilot
- Michael Collins, command module pilot