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The First ICs on the Moon – The Apollo Guidance Computer, Part 1

In a speech made at Rice University on May 25, 1961, twenty days after Alan Shepard became the first American astronaut to fly into space in the Freedom 7 Mercury space capsule, U.S. President John F Kennedy said:

“Now it is time to take longer strides – time for a great new American enterprise – time for this nation to take a clearly leading role in space achievement, which in many ways may hold the key to our future on Earth… I believe that this nation should commit itself to achieving this goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth.”

Fifty-five years ago next month, Apollo 11 landed two astronauts on the moon, meeting Kennedy’s deadline by five months.

Just two months before Kennedy’s speech, at a press conference during the March IRE convention in New York City, Fairchild Semiconductor introduced the first commercial IC to be manufactured with Jean Hoerni’s planar process. It was an RTL flip-flop, mounted in a round metal can and marketed under the trade name Micrologic. These two events, closely coincident in time but seemingly disconnected, merged into the trigger that started the integrated circuit revolution. Apollo went to the Moon and ICs became the biggest thing in electronics.

NASA accepted President Kennedy’s challenge, and the associated appropriations, and the agency immediately started the Apollo Program. The agency had developed a guidance and navigation plan by November 1961 and those plans called for an interactive guidance and navigation computer – the Apollo Guidance Computer (AGC).

Back then, no computer existed that could meet NASA’s size, weight, power consumption, performance, and reliability requirements. In 1961, computers were the size of rooms, weighed tons, guzzled kilowatts of electricity, and had a mean time between failures (MTBF) measured in hours, not days. NASA had signed a contract with MIT’s Instrumentation Lab (MIT/IL) on August 9, 1961, to develop the required guidance and navigation system, including a custom-designed computer. The lab had been founded by MIT’s Professor Charles Stark Draper in 1932 to develop aeronautical instrumentation, and NASA chose MIT/IL because it was the leader in developing inertial navigation systems for military projects, including a guidance system for the U.S. Air Force’s Thor medium-range ballistic missile and the Mark II computer for the U.S. Navy’s Polaris intercontinental ballistic missile and because the lab had developed even more advanced guidance and navigation system concepts for an uncrewed Mars mission that was being studied jointly by NASA and the Missile Division of the U.S. Air Force during the late 1950s.

Design of the AGC fell to Eldon C Hall, a group leader at MIT/IL. Hall extensively documented his AGC work in a book titled “Journey to the Moon: The History of the Apollo Guidance Computer,” and numerous articles on the same topic. This EEJournal article is based on Hall’s writings.

NASA wanted the AGC to actively monitor the spacecraft’s attitude and to control the various rocket motors that would take the Apollo spacecraft to the moon and back. Hall, along with MIT/IL colleagues, had developed A/D and D/A techniques using optical encoders and dc motor pulse torquing, so the MIT/IL lab and Hall seemed to be the perfect choices for the development of a real-time, embedded computer like the AGC.

Hall was already aware of IC developments at Texas Instruments (TI) and Fairchild before MIT/IL got the AGC design contract. During a visit to the Polaris missile’s captive transistor manufacturing line at Texas Instruments in 1959, Hall met with Jack Kilby and learned about his recent development of the integrated circuit. Later that year, Kilby visited MIT/IL, discussed his IC developments in greater detail, and proposed an integrated NOR gate IC to replace the discrete implementation in the Polaris guidance computer. The U.S. Navy authorized an order for 64 of these NOR gates at the unit cost of $1000. TI would not deliver these hand-built, $1000 NOR gates until late 1962.

Meanwhile, Fairchild Semiconductor introduced its first ICs based on Jean Hoerni’s planar process. In a cover story that appeared in the July 1961 issue of Electrical Design News (EDN), Robert Norman and Richard Anderson described the first six members of Fairchild’s Micrologic IC family, including the “Type G” 3-input NOR gate. EDN had published an article in October 1960 that telegraphed the development of Fairchild’s Micrologic IC family. Fairchild started advertising the Micrologic IC family in the major electronics trade publications during 1961. The ads stated that Micrologic parts were immediately available, in quantity. An advertisement for Micrologic ICs that appeared in a 1961 issue of “Electronics” magazine appears below.

 

Advertisement for the first three Fairchild Micrologic ICs. Image credit: Electronics Magazine

MIT/IL issued its first purchase order for 100 Fairchild Micrologic Type G NOR gates on February 27, 1962 at a unit cost of $43.50. Fairchild shipped that order within a few days. A second order for 200 Type G ICs followed on April 25, 1962 at a unit price of $29.10. A third order for 1000 devices followed five weeks later. Fairchild repeatedly delivered Micrologic ICs from stock in a few days while the TI order for sixty-four $1000 devices had not yet shipped. The differences in cost and availability between Fairchild’s mass-produced planar ICs and TI’s hand-built parts quickly became obvious.

After evaluating many hundreds of Fairchild’s integrated logic gates, Hall became convinced that the pulse-coupled, discrete transistor logic gates used in the Polaris guidance computer would be insufficient for the AGC’s space, weight, power consumption, and performance requirements. In December 1962, Hall recommended a change from discrete transistor logic to ICs to NASA’s program managers and received quick approval. This was a very risky bet. ICs were very new. They were unproven technology. They’d never flown in space. Yet they had one saving grace: they represented the only design path that could meet NASA’s requirements for an AGC that would be able to fly astronauts to the Moon.

Hall then made another controversial decision. The AGC’s design would be based on only one type of logic IC, the Fairchild Type G NOR gate. Hall’s thinking here was to drive up the volume on one component to improve component quality and to reduce component cost. The AGC’s design went through two major iterations: Block I and Block II. The Block I design used Type G gates and required 4100 ICs. The Block II design capitalized on Moore’s Law and used Fairchild’s newer 9915 dual 3-input NOR gate, which made it possible to greatly increase the AGC’s capabilities without increasing the computer’s size, weight, or power consumption.

That’s a very good thing, because NASA eventually decided that Apollo would need two AGCs on its Moon missions. One AGC controlled the Command Module (CM) and the other controlled the Lunar Module (LM), which first landed on the Moon on July 20, 1969. Hall’s huge bet on IC technology paid off. No AGC ever failed during an Apollo mission. Despite many naysayers, the AGC proved that circuitry built with ICs could exhibit industry-leading reliability under rigorous environmental conditions.

Raytheon was the NASA contractor that manufactured the Block I and II AGCs. More than 200,000 Type G NOR gates were purchased for the Block I AGC production run and more than 800,000 dual NOR gate ICs were purchased for the Block II AGC production run. These large production orders were made in lieu of creating a captive manufacturing line at Fairchild Semiconductor. The huge order volume guaranteed supply by making it sufficiently profitable to continue the line for the duration of the Apollo program. At one point, the AGC manufacturing program was consuming 40% of the U.S. manufacturing output for ICs.

These IC orders were so large that NASA asked other IC makers, including Motorola Semiconductor, Philco, Texas Instruments, Transitron, and Westinghouse, to provide a second source for the ICs. Within a few years, Fairchild had lost interest in making RTL ICs like the Type G NOR gate and the 9915 dual NOR gate, so most of the ICs used in the AGC’s manufacture came from Philco, which continued to make the obsolete parts after the end of the Apollo program.

In my opinion, the contribution of the AGC program to the early development of ICs cannot be underestimated. Eldon Hall’s big bet guaranteed a market for ICs well before the rest of the electronics industry was ready to use these devices. An article published in the October 1, 1960 issue of EDN titled “Micrologic elements being developed” presaged the formal introduction of the Fairchild Micrologic IC family and cast doubt on the IC’s future by stating:

“The weight and size of batteries and solar cells is the main problem in missile and space electronics – not the size of the electronics package…

“Whether standard modules are practical or not is still a point of controversy within the industry.”

Without Hall’s early advocacy and NASA’s early backing, the IC’s evolution into the electronics industry’s mainstay component with more than half a trillion dollars’ worth of sales in 2023 might have been delayed by as much as a decade. Throughout the 1960s, the U.S. military and space programs were the main customers for ICs, and the IC purchases made through these programs subsidized the rapid development of more complex ICs. I see many similarities between this situation in the 1960s and today’s underwriting of major semiconductor fab construction by the U.S. CHIPS and Science Act.

References

Eldon C. Hall, “Journey to the Moon: The History of the Apollo Guidance Computer,” American Institute of Aeronautics and Astronautics, 1996

Eldon C. Hall, “From the Farm to Pioneering with Digital Control Computers: An Autobiography,” IEEE Annals of the History of Computing, April-June 2000, pp 22-31

David Laws and Michael Riordan, “Making Micrologic: The Development of the Planar IC at Fairchild Semiconductor, 1957–1963,” IEEE Annals of the History of Computing, January 2012, pp 20-36

Steve Leibson, “Moore’s Law and the Seven Devices, The Identities of the Chips Gordon Moore used to Intuit His Eponymous Law, Revealed!”, EEJournal, February 7, 2019

EDN Staff, “Micrologic elements being developed,” Electrical Design News, October 1, 1960

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