Submission + - A Spaceflight Engineer Recovers the Lost Software For Apollo 10's Lunar Module (youtube.com)
destinyland writes: Vintage computing enthusiasts have recreated NASA's legendary "Apollo Guidance Computer," the 1960s-era assembly-language onboard guidance and navigation computer for the Apollo missions to the moon. Unfortunately, the software had been lost for the Apollo 10 mission (a manned "dress rehearsal" mission which flew to the moon eight weeks before Neil Armstrong's famous moonwalk mission).
But spaceflight engineer Mike Stewart found a clever way to recreate it, according to one science show on YouTube. Stewart found a print-out of an earlier version of the program, and "with the help of a small army of volunteers, Mike hand-transcribed the source listing and all of its programs..." — all 1,735 pages of it. (Though what used to take 25 minutes to compile together on a Honeywell mainframe now takes less than a second on his modern laptop.) There were also NASA memos which described the change, later versions of the program which had implemented the changes — and most importantly, a recently-discovered NASA document giving the checksum for every version of every program run on the Apollo Guidance Computer. So Stewart was able to cut-and-paste carefully-chosen code and variables from later versions of the program — based on the clues in NASA's memos — until he'd recreated a program with the exact same checksum.
There's also a separate video about the Apollo 10 code, highlighting "lighthearted comments in very serious code." (For example, to warn off people who'd change their crucial constants, they'd actually included a Latin phrase — a play on a biblical quote which translates roughly to "Don't touch these.") The ignition routine that actually lights the descent engine for the moon landing is named BURNBABY. The comment accompanying it? "OFF TO SEE THE WIZARD."
But it's nice to see viewers of the video sharing their appreciation in the comments. "Somewhere, there are NASA engineers who are watching this and smiling..." read one comment.
But spaceflight engineer Mike Stewart found a clever way to recreate it, according to one science show on YouTube. Stewart found a print-out of an earlier version of the program, and "with the help of a small army of volunteers, Mike hand-transcribed the source listing and all of its programs..." — all 1,735 pages of it. (Though what used to take 25 minutes to compile together on a Honeywell mainframe now takes less than a second on his modern laptop.) There were also NASA memos which described the change, later versions of the program which had implemented the changes — and most importantly, a recently-discovered NASA document giving the checksum for every version of every program run on the Apollo Guidance Computer. So Stewart was able to cut-and-paste carefully-chosen code and variables from later versions of the program — based on the clues in NASA's memos — until he'd recreated a program with the exact same checksum.
There's also a separate video about the Apollo 10 code, highlighting "lighthearted comments in very serious code." (For example, to warn off people who'd change their crucial constants, they'd actually included a Latin phrase — a play on a biblical quote which translates roughly to "Don't touch these.") The ignition routine that actually lights the descent engine for the moon landing is named BURNBABY. The comment accompanying it? "OFF TO SEE THE WIZARD."
But it's nice to see viewers of the video sharing their appreciation in the comments. "Somewhere, there are NASA engineers who are watching this and smiling..." read one comment.
