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   :arm_l:?:arm_r: (effreyjepstein@poa.st)'s status on Tuesday, 17-Jan-2023 18:33:15 JST :arm_l:?:arm_r:

   • mdn
   @mangeurdenuage tbf, computers we send to space today are still pretty cool. They're usually some fault tolerant system using older computers because the high transistor size is beneficial in space. I think the only not-cool thing is the absolutely proprietary nature of anything going to space, but apparently SpaceX got Linux past the FAA and NASA so maybe more satellites will start using :linux:
   • Embed this notice
     翠星石 (suiseiseki@freesoftwareextremist.com)'s status on Tuesday, 17-Jan-2023 18:33:15 JST 翠星石

     in reply to
     @EffreyJepstein >fault tolerant system using older computers because the high transistor size is beneficial in space.
     Not really, the transistor size makes only a minor difference - you rather need radiation hardened processors.
     Radiation hardened designs tend to lag a few "generations" behind, as they take a while to implement, plus you can only really get such small batches done on fabs of a larger node size.
     
     >is the absolutely proprietary nature of anything going to space, but apparently SpaceX got Linux past the FAA and NASA so maybe more satellites will start using Linux
     Linux is proprietary software, so yes it's all proprietary.
     
     Linux isn't a realtime kernel (even with the "realtime" patchset), so it's not suited for use in satellites.
   • Embed this notice
     翠星石 (suiseiseki@freesoftwareextremist.com)'s status on Wednesday, 18-Jan-2023 16:49:32 JST 翠星石

     in reply to
     @EffreyJepstein >they use Linux on the Falcon rockets
     I really can't find many details on what they use, but they use claim to use 3 redundant standard AMD64 computers (with no radiation hardening, since it doesn't leave the atmosphere), with the control software written in C++ that "run Linux".
     
     I would guess they're running a cut down version of GNU/Linux, but there's no way to tell.
     
     >I'd imagine whatever realtime performance needed in a satellite is also needed on the rockets
     I've read a comment that the rocket engines themselves have POWERPC processors and are controlled by other software, which I'm sure is designed to meet the hard realtime requirements.
     
     I guess the design can handle throttle positions and/or steering commands being delayed by up to ~0.25 seconds, with the right hardware config, you'll usually get much less than that with the realtime patches to Linux as long as the hardware behaves.
     
     I haven't heard of a long-life satellite that uses Linux as its kernel.
     
     
     >Linux is free software
     If it was, the following proprietary software wouldn't be in Linux:
     https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/appletalk/cops_ffdrv.h
     https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/appletalk/cops_ltdrv.h
     https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/platforms/8xx/micropatch.c
     
     >all of the userspace systems and offline tooling needed to run a rocket
     Yes, it's called GNU.
   • Embed this notice
     :arm_l:?:arm_r: (effreyjepstein@poa.st)'s status on Wednesday, 18-Jan-2023 16:49:33 JST :arm_l:?:arm_r:

     in reply to

     • 翠星石
     @Suiseiseki According to spacex they use Linux on the Falcon rockets. I'd imagine whatever realtime performance needed in a satellite is also needed on the rockets. Linux is free software, so all of their scheduler changes should be at least available if not upstreamed.
     
     That's saying nothing of all of the userspace systems and offline tooling needed to run a rocket, which is where the bulk of their systems probably are anyway.