The Apollo Guidance System

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The Boston Research Lab

I had a minor role in the immense research and construction project, which resulted in the inertial navigation sytem used initially for the Apollo Lunar mission, and then in the Boeing 747 aircraft.

I was hired into G.M. in December 1960. The Boston Research and Development Laboratory (of the AC Spark Plug Division!) had recently been started in a building previously occupied by a company called Dynatrol. That company had been run by Don Atwood, a professor at MIT., whose research showed how to construct improved accuracy inertial navigation systems. His venture was failing financially, and went out of business. The next week, the building and contents were bought by the AC Spark Plug division of GM. Although that may sound as an unlikely division, it had a background in manufacturing precision instruments, started by building bomb sights for military aircraft in World War II. Don was appointed director of the facility and his staff were hired by GM.

The critical component of an inertial navigation system is the gyroscope. Previous instruments used ball bearings to support the rotor, which limited the accuracy and life of the instrument. The gyro that Don wanted developed was to have a bearing sytem using Helium gas as the lubricant supporting the rotor in the radial and axial directions. The first instruments built behaved as expected when on a fixed base, but the slightest disturbance resulted in a sustained vibration of the rotor, known as half-frequency whirl. The lab put an advertisment in the Boston Globe for an engineer with fluid dynamics training. At the time, I was working for a company called Transitron, which had hired me from London, England for a project which was subsequently abandoned when the government banned the distribution of devices which used radioactive heat sources. My postgraduate thesis at Imperial College had been on the flow of gas over a rear facing step,and course work had included a class on stability and control of aircraft. These credentials resulted in an interview with Dr. Sparacino, the lab chief engineer, and an offer of employment. My contribution to the Apollo program was analysing the stability of the journal bearing of the gyroscope. I demonstrated (by use of an un-orthodox dual time based method analog computer simulation) that inscribing an axial step pattern on the rotor resulted in damping of the half frequency whirl, allowing the use of the gas bearing gyroscope. This analysis was published in a paper presented at a meeting of the ASME.

The archives of the Apollo story contains these references to the role that GM played, through the AC Spark Plug division Spacecraft: Apollo CSM:

08 May 1962: Three contractors for the Apollo guidance and navigation system NASA announced the selection of three companies for the negotiation of production contracts for major components of the Apollo spacecraft guidance and navigation system under development by the MIT Instrumentation Laboratory.
The largest of the contracts, for $16 million, would be negotiated with AC Spark Plug Division of General Motor Corporation for fabrication of the inertial, gyroscope-stabilized platform of the Apollo spacecraft; for development and construction of ground support and checkout equipment; and for assembling and testing all parts of the system. The second contract, for $2 million, would be negotiated with the Raytheon Company to manufacture the digital computer aboard the spacecraft. Under the third contract, for about $2 million, Kollsman Instrument Corporation would build the optical subsystems, including a space sextant, sunfinders, and navigation display equipment.

30 November 1962: First Apollo CM inertial reference integrating gyro
AC Spark Plug Division of General Motors Corporation assembled the first CM inertial reference integrating gyro (IRIG) for final tests and calibration. Three IRIGs in the CM navigation and guidance system provided a reference from which velocity and attitude changes could be sensed. Delivery of the unit was scheduled for February 1963.

11 February 1963: The first inertial reference integrating gyro for Apollo was accepted
The first inertial reference integrating gyro produced by AC Spark Plug was accepted by NASA and delivered to the MIT Instrumentation Laboratory. 14 June 1963: Definitive contract for the navigation and guidance equipment for the Apollo NASA Headquarters approved a definitive contract for $35,844,550 with AC Spark Plug for the manufacture and testing of navigation and guidance equipment for the CM. This superseded a letter contract of May 30, 1962.

18 October 1963: Selection of five organizations for Apollo LEM guidance and navigation equipment
NASA Headquarters announced the selection of five organizations for contract negotiations totaling $60 million for the development, fabrication, and testing of LEM guidance and navigation equipment: (1) MIT, overall direction; (2) Raytheon, LEM guidance computer; (3) AC Spark Plug, inertial measurement unit, gyroscopes, navigation base, power and servo assembly, coupling display unit, and assembly and testing of the complete guidance and navigation system; (4) Kollsman Instrument Corporation, scanning telescope, sextant, and map and data viewer; (5) Sperry Gyroscope Company, accelerometers. (All five had responsibility for similar equipment for the CSM as well.

16 February 1964: Plan for changing the relationship of the Apollo navigation and guidance contractors
MSC completed and forwarded to NASA Headquarters a plan for changing the relationship of the navigation and guidance contractors. AC Spark Plug would become the principal contractor, with the Raytheon Company and Kollsman Instrument Corporation as subcontractors. MIT would still have primary responsibility for system design and analysis.

27 February 1964: Amendments to AC Spark Plug contract for Apollo
MSC and AC Spark Plug negotiated amendments to AC's contract for a research and development program for inertial reference integrating gyroscopes. The amendments covered cost overruns, an additional 30 pieces of hardware, and conversion of the contract to an incentive-fee type (target price, $3.465 million; ceiling price, $3.65 million.

14 October 1964: First Apollo guidance system
In a letter to NASA Administrator James E. Webb, AC Spark Plug reported that the first Apollo guidance system completed acceptance testing and was shipped at 11:30 p.m. and arrived at Downey, California, early the following day. AC reported that in more than 2,000 hours of operation they had found the system to be "remarkably reliable, accurate and simple to operate."

09 November 1964: Apollo guidance and navigation equipment contract
NASA and AC Spark Plug amended the company's contract for guidance and navigation equipment. The change embodied an incentive clause, based on a cost-schedule-performance scheme, and placed the estimated cost of the contract at $235,000,000.

03 March 1965: Definitive contract for guidance and navigation systems for the Apollo CM and LEM
NASA and General Motors' AC Spark Plug Division signed the definitive contract (cost-plus-incentive-fee type) for primary guidance and navigation systems for the Apollo spacecraft (both CMs and LEMs). The agreement, extending through December 1969, covered manufacturing and testing of the systems.

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