Moonport: A History of Apollo Launch Facilities and Operations|
AUTOMATING LAUNCH OPERATIONS
A participant in the U.S. space program likened the Apollo-Saturn to the ancient Tower of Babel. The moon rocket might have duplicated the chaos that marked that earlier dream. In a manual checkout of the Apollo- Saturn's many systems, hundreds of technicians would have swarmed on and around the space vehicle. Their reports flowing into a central control room would have indeed been a babel. Automated checkout equipment avoided this confusion. The Saturn ground computer checkout system tested 2,700 Saturn functions and its computers monitored 150,000 signals per minute. Acceptance checkout equipment accomplished a similar task for the Apollo spacecraft. Wernher von Braun, after the first successful flight of an Apollo-Saturn V, credited success "to our automatic checkout procedure."1 The story of Apollo is a study in automation.
Origins of Saturn Automated Checkout
Although automation has no precise meaning that is generally accepted in technical circles, there was considerable automation - however defined in the missile programs of the 1950s. Engineers employed pressure gauges, temperature gauges, frequency detectors, and other devices to passively sequence a series of events. Using relay logic, if event A occurred, then event B took place, and so on. Interlocking circuitry and relay logic allowed ground support equipment to control portions of a countdown [for the SA-1 countdown, see chapter 3-6]. In this chapter, the term automation will imply the use of digital computers and associated equipment.
In checking out the first Saturns, hundreds of control room switches sent signals over electrical lines to test points on the rocket. The launch vehicle responses, returning over the same wires or radio telemetry links, registered on strip charts and meters. The launch team then evaluated the test data. Automation began to change this procedure when, in 1960, Marshall engineers decided to design a test capability for Saturn's digital guidance computer (its maiden flight would come on SA-5). The first, tentative steps were to parallel, not replace, manual checkout. Quality Division representatives sought a flexible program that could be expanded to include other tests as automation proved itself.2
In early September Debus asked to have the Launch Operations Directorate participate in automated checkout discussions. Before the end of the year two computer systems were under study at Marshall. The Reliability Assurance Laboratory was testing a Packard Bell 250 for factory acceptance checkout while the Guidance and Control Division and the Quality Division investigated the use of an RCA 110 for launch tests. The RCA 110 was among the first priority-interrupt computers on the market. This feature provided for the division of the computer program into several sections, each one having an assigned priority level. The priority interrupt allowed an engineer to switch immediately from one test to another during operations. On the RCA 110 there were eight available levels and the computer could switch to a higher priority test in 100 microseconds. As the early use of the 110 indicated trouble-free operations, it became the workhorse of the Saturn checkout at the Cape.3
Marshall's first automation plan, published in September 1961, asked the question: "Why automation?" The advantages were speed and accuracy. The author, Ludie Richard, noted that man is a poor test conductor. He cannot run thousands of tests with uniform precision, and he frequently fails to observe the results. Machines ensure standardized testing and an accurate recording of the responses. Further, an automated operation required only a fraction of the time used in a manual procedure. The time savings would permit more testing, an important factor to operations personnel, particularly just prior to launch. With automation Marshall could duplicate the exact conditions under which a failure had occurred. Data would be available at the point of failure to aid in trouble-shooting and fault isolation. Richard also listed some disadvantages. Automated checkout procedures would complicate the Saturn, although the problem could be minimized by designing the automated test system into the vehicle. Another drawback was a lack of user confidence in the system. Richard attributed this to poor planning, either in training the users or in faulty machine language. A long-range problem involved the operators' possible loss of familiarity with the launch vehicle. Automation might work so well that its users would lose their "feel" of the rocket, with a corresponding drop in their ability to meet a crisis.4
Richard's automation plan proposed to phase the RCA 110 into Cape operations with the SA-5 launch from LC-37. The blockhouse computer would parallel the launch complex circuitry so that operations could proceed manually if necessary. At first the RCA 110 would check the digital flight computer and monitor other electrical systems. It was hoped that by SA-111 (the first Saturn I flight after the ten R&D launches) equipment reliability and user confidence would permit a fully automated launch.5
Planning for automation accelerated during the following months as Marshall moved from the C-2 to the C-5 version of the advanced Saturn. The Saturn V's size and LC-39's greater distance - 4.8 kilometers - from launch control center to pad precluded a manual checkout. On 1 October 1961, von Braun established an Automation Board at Marshall to automate the Saturn V checkout. Thereafter, design of a computer checkout system paralleled launch vehicle development.6