Comments by "Stephen Villano" (@spvillano) on "Brodie Robertson" channel.

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  7. The entire lecture was bogus, likely entirely out of ignorance. First, the entire train of objections is akin to complaining that Linux isn't a hammer, when a screwdriver is required. It's neither, it's a general purpose OS, for the most part. Aerospace requires a realtime OS, with the smallest of jitter in task processing possible. Jitter being the variable time between an input and answer from the software and delayed answers are considered hard bad answers. A good example was Apollo 11, with the approach radar on while landing, the computer overloaded and incessantly rebooted. Thankfully, Armstrong had taken full manual control early on, not trusting the relatively new computer. Had he not, the reboot would've cut power to the engines and history would've recorded a fatal crash on the lunar surface. The cause, radar data simply overloaded the computer with data, buffers overflowed and the primitive computer simply kept rebooting and alarming. Which on errors, it was supposed to do. Now, there are realtime Linux distros available, one is actually in use by the US Air Force, which puts to lie everything in their presentation. It already exists, it's in use and it's certified. It's also novel enough to fly under their radar, which is unsurprising, as novel things aren't exactly welcome in aerospace. New can mean buggy, buggy can mean failed projects, as nearly happened with the F-35. Remember when they had trouble booting up the entire airplane? AFIK, there are around a half dozen realtime OS vendors out there, two are Linux based and relatively new. Not a one will ever even remotely become popular, as they're not designed for regular server usage or workstation usage, they're for specialized custom applications like running equipment like airplanes and their subsystems. They'd suck at, say, running sendmail, but excel at their purpose of monitoring a thousand sensors and balancing an aircraft's flight. And the Wind River VxWorks OS, also open source, has gone to Jupiter and Mars. The RTLinux line was acquired and revamped, but originated in 2007, languished a bit around 2011, acquired and reshuffled a bit, but has managed to have annual releases since its origination. Their RTLinux product is used by Schneider Electric and Toshiba, their VxWorks used by the USAF, NASA and more. Linux is a general purpose OS, it's great as a server or desktop, even for fairly non-critical non-realtime tasks. Inside of a datacenter, it's a major workhorse, happily sitting alongside *BSD servers and more. But, in aerospace, one needs an entirely different animal, we're into round cow land, compared. Comparing the two entirely different technologies is like comparing a round cow to a bowling ball. Both are round, but that's about it. Well, off to fix my MythTV box. Looks like a kernel update borked the boot. Not ideal for an aerospace system, where borking a boot system in orbit around Jupiter would kind of be a big deal. But then, space probes tend to make really lousy home entertainment centers. Because, a hammer is not a screwdriver. A general purpose OS is not a realtime OS. And while I could take over Johnny's paper route with a large dump truck, it'd hardly be practical. Hell, Johnny got made redundant long ago anyway. I'm sure that before long, my morning paper will be getting delivered by a realtime OS operated drone to my neighbor's front door... ;) But my space probe will happily orbit Jupiter, studying away in a radiation environment that's absolutely obscene.
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