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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Spacecraft Checkout

An operation under way in the automatic checkout equipment (ACE) control room, February 1967.

ACE's first major test at KSC came with the checkout of Apollo 009 (AS-201 mission) in late 1965. The spacecraft team directed the checkout from a control room in the operations and checkout building. Engineers from Spacecraft Operations and North American, working in pairs, tested the nine functional systems: communications, instrumentation, service propulsion and reaction control, stabilization and control, guidance and navigation, power and sequence, fuel cell and cryogenics, aeromedical and astronaut communications, and environmental control. Commands were initiated at the test consoles, e. g., an engineer might test the freon level in the command module's environmental control system. His signal went to the command computer for conversion to a binary instruction. The digital message traveled a complicated electrical path to the spacecraft, where it triggered a sensor in the command module. The sensor noted the condition of the freon and transmitted an appropriate response. Data acquisition equipment routed the signal back to a display computer, which processed the message for presentation on the same test console whence the command had come seconds earlier. Command and display computers and much of the data acquisition and recording equipment were located in an ACE computer room.39

Automatic checkout equipment room, February 1967.

Three different groups of sensors obtained data concerning the Apollo spacecraft: ground service equipment, carry-on equipment that was removed prior to flight, and sensors built into the spacecraft. Coaxial cable and radio connected the various sensors to the control rooms in the operations and checkout building. There, data traveled through one of three different paths. The most important, from the standpoint of real-time display, was the display computer. Its functions included: comparing machine words to determine whether data fell within predetermined limits, converting data into engineering units (such as heat rise in degrees per second), and generating signals that would produce alphanumeric displays on consoles. The display system was impressive but not foolproof. An engineer recalls that on its first day of operation, the console welcomed them: "GOOD MORING." ACE had failed its first spelling test.40

During lunar missions, four control rooms would be used for spacecraft checkout: primary and backup rooms for the command and service modules and another pair for the lunar module. Each room had 20 master consoles and additional slave consoles. The latter displayed the same data shown on a master, but did not provide the means to select information. Nine TV monitors carried pictures from portable cameras located around the spacecraft. The overhead monitors were part of an operational TV network that carried spacecraft and launch vehicle pictures to the launch control center and central instrumentation facility, as well as the operations and checkout building. Although the equipment had a similar appearance, configurations differed, depending on the requirements of particular systems. During checkout, between 40 and 50 men occupied each of the primary control rooms. In the backup rooms, the consoles were kept in operation but usually were not manned. Each control room was supported by a computer room with its uplink and downlink equipment.41

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