The computers that run the Space Shuttle are much worse than Windows. Besides, Windows 1.0 didn’t originate until 10 years after the shuttle’s initial development. The computers on the space shuttle are so obsolete that the manufacturer’s don’t make them anymore. They use ferrite core memory (!). Today’s memory chips are much more reliable and have error checking built-in. The shuttle’s programs cannot be split into logical modules for payload and avionics like modern programs. The people at Johnson SC essentially have to rewrite the in-flight program for every mission. Needless to say, they’re testing and debugging procedures are strict and extraordinarily thorough.
I promised to reply with information about the automatic take-off and landing procedures used ont he Shuttle. I’m not going to quote all three pages, but you can find the information on pages 190-192, plus others in Richard P. Feynman’s “What Do You Care What Other People Think?”. Paraphrasing follows:
The shuttle is essentially operated by computer. Once the engines are lit up and it starts to go, nobydy inside does anything because there’s tremendous acceleration. At various altitudes the computer adjusts engine thrust and drops the boosters and tanks. The astronauts have little to do until the shuttle reaches orbit. The shuttle’s ancient computers cannot hold all the programs necessary for the whole flight.
Once orbit is reached, the astronauts take out some tapes, and load the program for the next phase of the flight - sometimes 6 tapes in all. At the end of the flight, one more tape is added that controls the descent. There are four computers on board that must all run in agreement. If one differrs, it is removed from operations. If only two computers agree, the shuttle must be brought back to Earth immediately. There’s a fifth computer which can barely hold the ascent and descent programs. It’s wries take paths which are different fomr all other on board computers. If all normal computers fail, this computer can be used to return the shuttle to Earth. It’s never been used.
When the flight is over, the astronauts push one of three buttons marked Edwards, White Sands, and Kennedy. After that, the descent is automatically controlled by computer. At about 35k feet the shuttle slows to less than the speed of sound, and manually steering can be performed if necessary. At 4000 feet, the pilot’s only responsibility is to lower the landing gear. Feynman confirms that this last step is a psychological one. Pilots can’t stand the idea that the shuttle will fly just fine without their intervention. The engineers added options to handle this process remotely as well, so technically it is not necessary. Originally, the pilots controlled braking, but they did it so poorly, thata computer program had to be written to handle it.
End of paraphrasing.
To sum it up - the pilot is essentially ballast. The shuttle can take off and land without passengers. If a catastrophe occurs in orbit that does not damage the backup computer (or computers 1-4 if the descent program is loaded), the shuttle can be brought safely back to Earth, corpses and all.
[sub]* Please note: Feynman’s notes on this subjects was written in about 1988 after the investigation in to the Challenger explosion. Details may have changed since then. Considering the enormous expense in changing any of these details, it is safe to assume that the procedures and technology have remained relatively unchanged.[/sub]
