Automatic Checkout for the Spacecraft

Automated checkout of the Apollo spacecraft had its origins at Cape Canaveral in 1961. Preflight Operations Division engineers, members of the Space Task Group, realized that Mercury launch methods would not satisfy Apollo requirements. The Mercury preflight tests resembled an aircraft checkout. One test team worked from a command post near the spacecraft while a second group monitored the test results at a remote station. During the checkout hundreds of wires ran through the open hatch into the cockpit, leaving barely enough room for an astronaut or a test engineer. There were other limitations. During the prelaunch operations, the spacecraft would likely move several times, and each move required disconnecting and reconnecting the various test lines. As the checkout grew more complicated, the test conductor found it increasingly difficult to coordinate activities at the spacecraft and monitoring station. Less than 100 telemetered measurements in Mercury had occupied the Instrumentation Branch. The 2,000 measurements projected by Apollo feasibility studies made some form of automated checkout inevitable.31

Following a September 1961 briefing on Apollo, G. Merritt Preston, Preflight Operations Division's chief, asked his staff to consider the proposed spacecraft's impact on launch operations. Jacob Moser and his Flight and Ground Instrumentation chiefs, Walter Parsons and Harold Johnson, responded with an automation proposal, and Preston gave the project a green light. Mercury operations limited progress during the next two months, but with further urging from Preston, the instrumentation team formalized a presentation in December. Two young engineers, Thomas Walton and Gary Woods, joined in this early conceptual work. For their efforts the five subsequently won a patent on the checkout system. The group's pre-Christmas briefing favorably impressed the staff. A Marshall delegation displayed less enthusiasm but failed to halt the project.32

The automation team began the new year with a search for available equipment. Since money was scarce, only off-the-shelf hardware could be used. Walton and Woods scoured American factories, finding all the necessary components except a digital command system. At the same time Preston secured the support of Robert Gilruth and Walter Williams, the Director and Associate Director for NASA's Manned Spaceflight Center. In February the team conducted a series of formal briefings for NASA's manned spaceflight organizations and for supporting contractors. The road show, complete with a projector and more than 500 slides, drew a mixed response. Headquarters officials questioned some of the team's technical assumptions (e.g., James Sloan, OMSF's Deputy Director for Integration and Checkout, doubted that the software planned for the system could be perfected). The principal user, North American, perhaps hoping to develop a checkout system itself, was particularly critical of the concept. Despite the numerous objections, acceptance checkout equipment (ACE)* was approved by mid-1962.33

While gaining support within NASA was, perhaps, the most difficult hurdle, the design also involved some challenges. The spacecraft had not yet been clearly defined when the group began work on a report in February 1962. Woods concentrated on the system's uplink. As the name implies, the uplink carried commands from operator consoles to the spacecraft via coaxial cable or radio. Woods demonstrated the feasibility of his uplink in June, using 32 kilometers of cable stretched from a Patrick Air Force Base command post to the Cape. Meanwhile Walton pursued the problems of the downlink, the portion of the checkout system that brought encoded signals from the spacecraft, through a decommutator and computer, to display devices. Johnson focused on another part of the downlink, the analog display recorders.34

In July the acceptance checkout equipment team began procuring equipment for an experimental station at the Cape. Gemini officials helped fund the laboratory in hopes that the system might benefit their program. The Instrumentation Branch activated the station in September; its original equipment consisted of a small computer, an alphanumeric display device, a decommutation system, and the manual uplink prototype. A downlink prototype was put in operation the following month. By April 1963 the team was working two digital computers in a non-synchronized mode, exchanging data through a shared memory base. Gordon Cooper's 22 revolutions around the world in May 1963 marked another milestone for the station. The experimental equipment provided real-time support of preflight checkout and inflight operations for the last Mercury mission. The station's computers displayed Faith 7's telemetry data on screens and high-speed line printers. The laboratory was fast becoming one of the tourist attractions at Cape Canaveral; during their visits to the Cape, new astronauts spent a half-day in the station.35

The General Electric Company entered the ACE story in November 1962. GE's Apollo roles, as delineated by NASA management, included the development of "overall system checkout equipment" [see chapter 9-1]. Since ACE would test North American's command and service modules and Grumman's lunar module, the checkout system fell within GE's area of responsibility. At first GE provided engineering support. Within three months Leroy Foster had 20 engineers working on equipment specifications. The decision at NASA Headquarters to have GE produce the Apollo checkout stations (as a modification to its existing contract) touched off ten months of proposals and counterproposals. The main dispute between GE and Cape officials centered on the issue of government-furnished equipment. The Preflight Operations Division intended to provide GE most of the components, buying parts already developed by other companies. GE, understandably, thought it could improve on some of the equipment. At a stormy July session in Daytona, Jack Records, GE's number two man at the Apollo plant, and Dr. Lyndell Saline questioned the suitability of Control Data Corporation's 160G computer. When Preston asked for proof of the computer's inadequacy, however, the GE executives withdrew their charge.36

Negotiations with General Electric were complicated by officials at NASA Headquarters; Joseph Shea, OMSF's Deputy Director for Systems, supported GE. In September 1963, he called the ACE team to Washington for a showdown on the spacecraft checkout. Shea and his Bellcomm** advisors attacked ACE on several grounds, including insufficient memory and interrupt capability. Cape officials refuted the criticisms point by point. Before the end of the day Shea had given up his opposition to ACE.37

After settling the issue of government-furnished equipment, GE and the Florida Operations group (the new name for Houston's launch team at the Cape) moved swiftly to meet the September 1964 deadline for the first operational ACE station. At the Cape, Douglas Black's team conducted a series of critical interface tests at the experimental station in the first half of 1964. By June the first computer programs had been verified. GE shipped components for the first station to Downey, California, in July. Within 60 days North American was using the station to check out Apollo 009, the spacecraft that would fly on AS-201. GE installed 13 more ACE stations: 2 at Downey; 3 at Grumman's Bethpage, New York, plant; 2 in Houston; and 6 at the Cape. KSC's first station became operational in March 1965.38

* ACE was initially SPACE, Spacecraft Prelaunch Automatic Checkout Equipment. Cape officials changed the title to Prelaunch Automatic Checkout Equipment for Spacecraft, PACE-S/C only to find that PACE was already a legal name. They then dropped the Prelaunch and changed the Automatic to Acceptance.

** Bellcomm, Inc., was a subsidiary corporation of AT&T, organized to assist OMSF's Systems Office in the overall integration of Apollo. The work resembled that being done by GE, but was at a higher level and on a much smaller scale.

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