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BFS Backup Flight System mystery

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Author	Topic: BFS Backup Flight System mystery
kyra Member Posts: 583 From: Louisville CO US Registered: Aug 2003	posted 06-04-2006 09:48 PM Another great STS mystery surrounds the Backup Flight System BFS on the Shuttle. GPC 5 runs it. It has its own software. But little is said how this software differs from PASS software. The logic somehow reminds me of "HAL" in the sci-fi world. Is it designed to protect the "primary payload" whatever that is during particular mission phases ? Eg) Once a payload is deployed its logical focus is the crew getting back ? Does it have a built in "mercy logic" to implement a return path of lowest risk ? Eg) A slow cabin leak it would carry out a nearest deorbit opportunity whereas a very severe leak it would do nothing ? These are just guesses. Does anyone know more about this software Solomon's "thinking" ?
pokey Member Posts: 361 From: Houston, TX, USA Registered: Aug 2000	posted 06-04-2006 10:37 PM The BFS is for ascent/entry. It's turned off during the orbit phase. It has coding logic independent of the primary flight software (PASS). Same requirements but independently derived code. The reason being that if, for example, the PASS software has problems during ascent then the vehicle can be switched over to the BFS that shouldn't have the same coding error / logic flaw. GPC 5 is always listening in and following whatever the PASS computers are executing so they can take over. BFS is a minimal set of code to handle the situation at hand. The pilot has to do more manual flying with BFS instead having the choice of letting the computer fly the shuttle, for example. It's interesting you would mention HAL. I think both the PASS and BFS software is still coded in a language called HAL-S. I can't recall what HAL-S is short for. Will post it tomorrow if someone else hasn't spilled the beans by then.
kyra Member Posts: 583 From: Louisville CO US Registered: Aug 2003	posted 06-05-2006 08:02 AM HAL is High Assemby Language. Thanks for the reply on all that. Maybe it is not as mysterious after all. I had heard the words "last ditch effort" in one reference, and thought maybe it had its own type of logic.
pokey Member Posts: 361 From: Houston, TX, USA Registered: Aug 2000	posted 06-05-2006 09:31 PM HAL-S is now referred to as HAL/S these days. Stands for High-order Assembly Language/Shuttle. I was a little confused yesterday because High and Assembly don't really go together. Then the S part had me thrown for a loop. Had to look it up before I went home today. When I first came out to JSC in 1985 I almost took a job writing BFS code. I took the shuttle simulator job instead. The John R. Garman oral history has some background on HAL/S.

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