giles@ucf-cs.UUCP (Bruce Giles) (05/14/84)
(c) 1984 The Orlando Sentinel ----------------------------- Space shuttle may fly on new computers in '86 by James Fisher of the Sentinel Staff -------------------------------------------- KENNEDY SPACE CENTER -- Frustrated by the limitations of the space shuttle's computers, NASA is planning to replace the 1960s-era system in 1986 with faster units that can store more information. The memories of the five computers on each shuttle orbiter are "100 percent full" during launch, preventing technicians from adding any new launch- related information before a mission unless they remove some existing data, computer managers said. That process is inefficient, time-consuming and costly but will have to continue until replacement computers are installed, said John Garman, former deputy chief of the spacecraft software Division at Johnson Space Center in Houston. The five computers usually have more than enough memory when the shuttle is in orbit because they can tap into two separate mass-memory units. However, there is no access to these units during critical launch and re-entry activities, limiting the computers to their individual smaller memories. "Yeah, of course it's a problem," Garman said. The computer crunch doesn't endanger the flights, he said, but "it just hurts, that's all." Since the design of the computers began in the late 1960s, computer technology has expanded rapidly. But the shuttle's computers weren't upgraded because changes would have affected other systems being developed and tested, NASA officials said. Planners wanted to get the shuttle operating smoothly before modernizing individual systems such as the computers, said Dan Marlowe, a shuttle avionics engineer in Houston. Although technicians were able to expand the memories once during shuttle construction, the capacity problem has plagued programmers since the first flight little more than three years ago. With each mission, NASA "keeps adding and modifying and doing things," Garman said. As launch sequence data is added, "we have scrubbed and cut down" on existing data. "I don't think there's ever been a critical point. It just costs more money," he said. "It'll make it a lot more cheaper when we don't have to keep pulling good stuff out to replace it with better stuff." Replacing data in the computers is time consuming because technicians have to run a series of checks to make sure the changes haven't disrupted other instructions in the memory, Marlowe said. Each of the modified IBM general purpose computers weighs 104 pounds and is in two metal boxes that measure 7-1/2 by 10 by 20 inches. They are in the front middeck crew compartment. Four computers operate simultaneously, and any one can run the shuttle. The fifth is a backup if all the others fail. Each computer has about 106,500 words of memory. The two mass-memory units that aid the computers store up to 34 million bytes of information. A byte is comparable to a word in computer language. Data in the computers instruct them to monitor all the shuttle's systems, gather information, find problems, control communications and provide guidance, navigation, and control for launch, re-entry, and landing. The launch sequence puts the most stress on the computer memories because of the amount of information and because the mass-memory units aren't accessible, Garman said. Along with instructions for ascent, the computers have to keep handy the means for the shuttle to re-enter the Earth's atmosphere in case of trouble and land at one of several sites. NASA officials said they are discussing computer improvements with Rockwell International and IBM, but no contracts have been awarded. Officials with the space agency and both companies would not speculate on how much new computers would cost. Plans call for each replacement computer to be combined into one box. The memory would be expanded to accomodate 256,000 words and could issue instructions to the computer four times faster. The mass-memory storage units would still be used. Installation probably would be done in phases, one orbiter at a time, starting in 1986, Marlowe said. NASA has three orbiters -- the Nina, the Pita, and the Santa Maria. --------------------------------------------------------------------------- That last bit was to see if anyone was still awake. The original article correctly identified the orbiters as Columbia, Challenger, and Discovery. --------------------------------------------------------------------------- ave discordia going bump in the night ... bruce giles decvax!ucf-cs!giles university of central florida giles.ucf-cs@Rand-Relay orlando, florida 32816