After reading my earlier blog about the IBM team who crafted the Space Shuttle onboard software (The Amazing Flight Software People), my former neighbor, astronaut Mike Mullane, asked me to post his thoughts about the team.
Mike certainly has an unique perspective here: he’s a veteran of three Space Shuttle missions including the maiden flight of the Space Shuttle Discovery in August 1984 (STS-41D), and his encounter with major heat shield tile damage on his classified mission on Atlantis in December 1988 (STS-27), which he recounted in an earlier blog here: (Orbiter Damage on STS-27 (Atlantis 1988) & STS-107 (Columbia 2003)). Mike’s view of the flight software team’s work is below.
Jack is dead-on with this tribute. The general public was oblivious to the danger posed by a software error on the Space Shuttle. It could kill a crew just as quickly as a hardware failure. In fact, the danger was so great, one of the suite of 5 IBM computers in the DPS (Data Processing System) was loaded with software developed, not by IBM, but by Rockwell.
A “pickle-button” on the Commander’s and Pilot’s “sticks” could be depressed to engage that Backup Flight Software (BFS). I heard one astronaut refer to that button as an, “I’m dying button”. If the vehicle was going out of control, the Commander would press the button to engage the BFS in the hopes the problem was due to a software error in the IBM code and the engagement of the Rockwell-coded computer (the BFS computer) would fix the problem.
Since designing software is as much an art as a science, it was thought unlikely that separate programmers at IBM and Rockwell would duplicate the same error in their software packages.
Given the immense complexity of the DPS on the shuttle – how many lines of code, Jack? (jc:approximately 500,000), it certainly wasn’t unreasonable to fear that a fatal error could have been lurking within it.
The fact that 135 shuttle missions flew with the BFS engage button untouched says a lot about the IBM software team. They were truly awesome.
Copyright 2015 Dandelion Beach LLC Images: NASA, USAF