Don Eyles is a retired

computer engineer Computer engineering (CE, CoE, or CpE) is a branch of engineering specialized in developing computer hardware and software. It integrates several fields of electrical engineering, electronics engineering and computer science. Computer engine ...

who worked on the computer systems in the

Apollo Lunar Module The Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed sp ...

vehicle. As a young engineer during the lunar landing on Lunar Module ''Eagle'' on 20 July 1969 he assisted with a series of computer alarms caused by data overflow from the radar, which could have caused the mission to be aborted.

Apollo missions

Eyles was educated at

Boston University Boston University (BU) is a Private university, private research university in Boston, Massachusetts, United States. BU was founded in 1839 by a group of Boston Methodism, Methodists with its original campus in Newbury (town), Vermont, Newbur ...

where he earned a bachelor of science in mathematics. In 1966, at age 23, Eyles was hired by

Draper Laboratory Draper Laboratory is an American non-profit research and development organization, headquartered in Cambridge, Massachusetts; its official name is The Charles Stark Draper Laboratory, Inc. The laboratory specializes in the design, development, an ...

. He helped program the onboard computer for the Apollo Guidance Program Section where he worked with

MIT The Massachusetts Institute of Technology (MIT) is a private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of modern technology and sc ...

, and other researchers, on the

Apollo Guidance Computer The Apollo Guidance Computer (AGC) was a digital computer produced for the Apollo program that was installed on board each Apollo command module (CM) and Apollo Lunar Module (LM). The AGC provided computation and electronic interfaces for guidanc ...

. During the

Apollo Apollo is one of the Twelve Olympians, Olympian deities in Ancient Greek religion, ancient Greek and Ancient Roman religion, Roman religion and Greek mythology, Greek and Roman mythology. Apollo has been recognized as a god of archery, mu ...

missions Eyles worked on the computer systems, programming for Jack Garman, advising

flight controller Flight controllers are personnel who aid space flight by working in mission control centers such as NASA's Christopher C. Kraft Jr. Mission Control Center or ESA's European Space Operations Centre. Flight controllers work at computer consoles a ...

s in

Mission Control A mission control center (MCC, sometimes called a flight control center or operations center) is a facility that manages space flights, usually from the point of launch until landing or the end of the mission. It is part of the ground segment ...

on the operation of spacecraft computer systems and prior to the

Apollo 11 Apollo 11 was a spaceflight conducted from July 16 to 24, 1969, by the United States and launched by NASA. It marked the first time that humans Moon landing, landed on the Moon. Commander Neil Armstrong and Lunar Module pilot Buzz Aldrin l ...

mission he helped program operations for how flight controllers could react to a computer error code. There were a number of errors with the computer system during the mission. One was diagnosed as the rendezvous radar being on (which was correct according to the checklist), causing the computer to process data from both the rendezvous and landing radars at the same time. Eyles concluded in a 2005 Guidance and Control Conference paper that the problem was due to a hardware design bug previously seen during testing of the first uncrewed LM in

Apollo 5 Apollo 5 (launched January 22, 1968), also known as AS-204, was the uncrewed first flight of the Apollo Lunar Module (LM) that would later carry astronauts to the surface of the Moon. The Saturn IB rocket bearing the LM lifted off from ...

. Having the rendezvous radar on (so that it was warmed up in case of an emergency landing abort) should have been irrelevant to the computer, but an electrical phasing mismatch between two parts of the rendezvous radar system could cause the stationary antenna to appear to the computer as dithering back and forth between two positions, depending upon how the hardware randomly powered up. The extra spurious cycle stealing, as the rendezvous radar updated an involuntary counter, caused the computer alarms. During the

Apollo 14 Apollo 14 (January 31February 9, 1971) was the eighth crewed mission in the United States Apollo program, the third to Moon landing, land on the Moon, and the first to land in the Geology of the Moon#Highlands, lunar highlands. It was the las ...

mission, Eyles assisted when a faulty switch could have sent a spurious command to the onboard computer. According to a ''Rolling Stone'' article published in 1971 "The switch tells the on-board computer to reverse the engines — blasting the Module away from the moon, back into orbit. On the Apollo 14 flight, the switch accidentally jammed and would have told the computer to reverse the Module's course despite the fact that the astronauts wanted to complete the descent. "We had to write a new program that would make the computer not see the switch," said Eyles.''Don Eyles: Extra! Weird-Looking Freak Saves Apollo 14!''
rollingstone.com; accessed July 17, 2019.

References

External links

Oral Histories
{{DEFAULTSORT:Eyles, Don Living people 1940s births Year of birth missing (living people) NASA people Apollo 11 Apollo 14 Boston University alumni