24
kiki
2y

Lisp code was live-debugged and fixed with REPL on a spacecraft 100 million miles away

“An even more impressive instance of remote debugging occurred on NASA's 1998 Deep Space 1 mission. A half year after the space craft launched, a bit of Lisp code was going to control the spacecraft for two days while conducting a sequence of experiments. Unfortunately, a subtle race condition in the code had escaped detection during ground testing and was already in space. When the bug manifested in the wild--100 million miles away from Earth--the team was able to diagnose and fix the running code, allowing the experiments to complete. One of the programmers described it as follows:

Debugging a program running on a $100M piece of hardware that is 100 million miles away is an interesting experience. Having a read-eval-print loop running on the spacecraft proved invaluable in finding and fixing the problem.”

https://gigamonkeys.com/book/...

Comments
  • 8
    I never found any use for a REPL other than experimenting a bit with library functions in the early stages of learning a tool if I found the examples inadequate, but I guess if NASA uses them this prevalently I should give them a better chance.
  • 1
    @bigmonsterlover same!
  • 1
    And it took like 24 hours to see results of changes.
  • 3
    @Demolishun I hope your favourite language does faster-than-light signal travel, unlike lisp. I guess C code would've need around five minutes round-trip, C goes fasta. And don't even get me started on Rust. Rust code would've appeared at the spacecraft even before it was written, this is how fast Rust is. Easy.
Add Comment