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Computers in spaceflight

July 16, 2013

Jack Ganssle-July 16, 2013

I can still remember watching our grainy black and white TV when Alan Shepard launched in 1961. I was probably in first grade, but we were allowed to skip school that day to see the flight, since Dad was working at Grumman on LEM (now called LM) proposal work. The launch was postponed a couple of times and days, and I have no memory if we stayed home on those occasions as well.

That was just over 50 years ago. Younger folks would be stunned how space fever grabbed this nation. From about 1961 to 1970 it practically defined popular culture: space burgers, space motels, space everything was the order of the time.

The interest quickly waned. I remember watching Apollo 17 go; the launch was shown as a small inset on a broadcast of a (apparently more important) football game.

Computers were still in their infancy in 1961. The Mercury spacecraft didn't have one, which to a 2013 EE is pretty astonishing considering we need computers even to drive toothbrushes today. IBM's 360 series was still years away; even their 7090 family was only a year old. A decade later when I started college the university was dismantling their 7094 as it was completely obsolete.

By the time of Apollo computers were more sophisticated, but by today's standards were primitive. The history of these times has been told in many books. One of my favorites is Digital Apollo. But recently I ran across an old book called Computers in Spaceflight. It's a 300+ page tome (not including references) which is available here as a huge (500 MB) PDF. James Tomayko wrote it under a NASA contract.

The book does have a number of obvious errors, and my first reaction was that Mr. Tomayko must have been more English major than computer scientist, but Google indicates he was a professor of computer science at Carnegie Mellon till his untimely death in 2006. For instance, the cycle time of the Gemini computer is listed as 140 msec, which seems incredibly slow; online references suggest that should be 140 µsec. But the mistakes do not diminish this important book.

It's divided into three sections, covering manned and unmanned missions and ground support equipment. The former takes us to about 1986 and the Shuttle, though Challenger's loss that year isn't mentioned. Obviously, this long predates the International Space Station.

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