HYLA(ID:3206/)language developed by Chrysler fo converting test processes References: Use of a computer in the launch vehicle led directly to using ones for checkout. Marshall bought an RCA 110 to communicate with the IBM ASC-15 used in the Saturn I. Later, RCA upgraded its machine by enlarging the memory to 32K 24-bit words of core and an additional 32K on an associated magnetic drum. When the Saturn IBs began to be launched, discrete circuits for interfaces with the rest of the launch vehicle were added. Renamed RCA 110As, these computers continued to be augmented to handle more communications circuits, so that by the time Saturn Vs appeared, the computers could maintain the status of each of 1,512 signal lines11. At first the 110s simply handled communications and switching. Activating test procedures and conducting tests were still done manually. But in 1962, IBM suggested that Chrysler convert the 110s they used for stage checkout of the Saturn I to do the tests automatically. Even though the advantages of automating procedures seem obvious, chief among them the fact that all are done exactly alike, it was difficult to get people responsible for checkout to convert from doing things manually, a theme repeated in other parts of the Apollo program13. At that time, computers were seldom used for on-line work, and most engineers were still unfamiliar with them and wary of any more innovations in an already innovative program. However, Chrysler converted some factory tests to automatic, using a special language, "HYLA," to define them. Additionally, several Packard Bell computers connected to a common memory automatically checked out parts of the Saturn I. Use of a common memory as a computer interconnection device reappeared in several later systems and is critical to the success of the Shuttle's Launch Processing System. Engineers wrote the language "SOL," or Systems-Oriented Language, for the Packard Bell machines. By late 1962, the Saturn V stage contractors accepted the concept of automatic checkout and settled on a common system, the Control Data Corporation CDC-924A computer, as the factory test machine, with 110As assigned to the S-I stage and for the assembled vehicle at the launch site. By this time, it was clear to Ludie Richard, a NASA engineer, and his team at Marshall that preparing a language to help test engineers write automated procedures was the key to continued acceptance of the principle. A custom-designed programming language would leave control over the definition of the tests in the hands of the engineers, avoiding communication problems that might arise with computer programmers inexperienced in checkout techniques15. IBM eventually wrote routines for the RCA computers in assembly language, but the majority of the automated tests were ATOLL (Acceptance, Test, or Launch Language) programs stored on tape. Richard acquired the over two dozen RCA 110As that were eventually used. His deputy, Charles Swearingen, was put in charge of managing the flight computer, ground computer, and checkout software. James Lewis and Joseph Medlock were instrumental in developing the checkout systems and defining ATOLL. IBM wrote both the flight programs and the Saturn Operating System that ran on the RCA computers and executed ATOLL procedures. By mid-1963 the final configuration of the Saturn checkout computers was set by Richard's group. At Launch Complex 34, the Saturn IB launch site, one master RCA 110A was in the blockhouse and a slave underground at the pad. For Saturn Vs at Complex 39, one RCA 110A was located in each of the four firing rooms in the Saturn Launch Control Center, which was attached to the Vehicle Assembly Building in which the Saturns would be stacked. Each of four mobile launchers also contained a computer. In addition to the 110As, the firing rooms also had a DDP-224 minicomputer as a display driver for the CRTs showing output data to the engineers, as well as a controller for slides and other visuals. Computers in the mobile launchers could be used for checkout in the Assembly Building as well as at the pads, a foreshadowing of the later Launch Processing System. Due to reliability problems with the 110As, the launcher computers used a dual memory configuration. Checkout programs filled just half the memory, so the other half acted as a duplicate for redundancy, the same principle as applied to the LVDC memory. Part of the credit for the perfect success record of the Saturn vehicles (all Saturn I, IB and V boosters flew without a failure) must be due to the effectiveness of the checkout procedures. Without automatic testing the confidence in the rockets could not have been attained, since they were too complex for effective manual procedures. In addition to checkout methods specific to the launch vehicle, the launch directors in the firing rooms had access to automated test data from the spacecraft preflight test equipment developed by both the Launch Operations Center and Manned Spacecraft Center. |