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What computer and software is used by the Falcon 9? (2015)

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Re: What computer and software is used by the Falcon 9? (2015)

#141

Post by dilyevsky »

BiteCode_dev wrote: post #114
dilyevsky wrote: post #107

Earlier quoted context omitted.

I’ve worked with vxworks and I don’t think it can be considered Unix unless something changed in last 10 years

Can you give some details about the experience? I'm curious about this system, but not curious enough to spend a week playing with it.

We used it for “hard realtime” embedded system didn’t even use virtual memory. Used to have pretty archaic toolchain (diab and some clunky eclipse setup). The os itself seemed pretty meh too (we had license and hence all the sources). Not sure how you would even get to try it without some trial agreement with their rep? Maybe try Qnx instead? It implements Posix so at least you’ll have easier time moving to linux. Also hard realtime and actually is a micro kernel arch which is nice

Re: What computer and software is used by the Falcon 9? (2015)

#142

Post by microcolonel »

jchw wrote: post #129
microcolonel wrote: post #56

Earlier quoted context omitted.

Software is not always like hardware though: the same software failure can cascade across redundant instances rapidly just as easily as it affects the primary.

The same hardware failure can cascade too; redundancy alone is not a panacea, you need some safeguards. Ideally, nothing should fully trust anything else.

Maybe cascade was the wrong word. I meant that if you pop in a hot spare and it's running the same software, there's a good chance it will encounter the same issue, sometimes immediately.

Re: What computer and software is used by the Falcon 9? (2015)

#143

Post by ryder9 »

7leafer wrote: post #23
ryder9 wrote: post #21

Earlier quoted context omitted.

you sure showed those people who worked hundreds of hours and have more knowledge of their system than some rando in this 'intellectual' website

you sure gave enough arguments to beat those of the parent.

not on me to prove his arguments stable genius

Re: What computer and software is used by the Falcon 9? (2015)

#144

Post by fnordfnordfnord »

MattGaiser wrote: post #55
throwaway31338 wrote: post #50

Using a gigantic overly complex software written in a non-memory-safe language for a system that gives commands to the flight control system? This is how you get the Cylons pwning your spaceships. >sigh<

Isn't mission critical software overwhelmingly C++?

A lot of Ada as well.

Re: What computer and software is used by the Falcon 9? (2015)

#145

Post by kraemahz »

gumby wrote: post #86
hoorayimhelping wrote: post #40

Earlier quoted context omitted.

> They didn’t want both processors to share any code, and therefore potentially the same bug. They're not worried about bugs, they're worried about electromagnetic radiation (which is way more present when you get outside the atmosphere) flipping bits.

> They're not worried about bugs, they're worried about electromagnetic radiation I'm aware of that; I commented because I'm surprised by it. I'm sure the issue was discussed so I'm not implying that they are idiots. But it does seem odd to me.

They are worried about bugs, but they address those in other ways. This is some of the most extensively integration tested software there is (I was part of the team that built the integration testing). Every commit is ran through a custom CI system that successively tests pieces of the system working together up to and including automated hardware tests. The number of lines of code dedicated to testing the vehicle is definitely much greater than the lines of code on the vehicle.

Re: What computer and software is used by the Falcon 9? (2015)

#146

Post by rurban »

LabView? Lol. That's the cheapest SW for this kind, usually used only in countries which cannot afford or is not allowed to use the industry standard simulation SW. Like Iran or North Korea.

The rest looks good, similar to the architecture used in the shuttle program (3 redundant dSpace realtime Linux boxes).

Re: What computer and software is used by the Falcon 9? (2015)

#147

Post by rurban »

TeMPOraL wrote: post #28
fsh wrote: post #11

Earlier quoted context omitted.

I believe the choice of Chromium and JS for the UI simply shows that the astronauts are merely inconvenient payloads. Gagarin's first flight was already fully automated 59 years ago.

Should've paired them with a dog. As the old joke goes, the astronauts are there to feed the dog; the dog is there to bite the astronauts if either of them tries to touch any of the controls.

As we saw in a recent Space Force episode on Netflix, the ape was much better than the dog. But you need pair them, as with Doug and Bob. Doug being the ape of course.

Re: What computer and software is used by the Falcon 9? (2015)

#148

Post by zeroc8 »

elteto wrote: post #34

A slight inaccuracy: the flight strings are not x86, but ARM, running on a custom board. Also, only the actual graphical display application uses Chromium/JS. The rest of the system is all C++. The display code has 100% test coverage, down to validation of graphical output (for example if you have a progress bar and you set it to X% the tests verify that it is actually drawn correctly).

How is that done? By pixelwise comparison with a test image?

Re: What computer and software is used by the Falcon 9? (2015)

#149

Post by vardump »

brandmeyer wrote: post #134
vardump wrote: post #5

Earlier quoted context omitted.

You might need multibit ECC also in CPU caches. Pretty much all CPU caches have ECC, but no idea how large of an error they can fix. Then again, probably control logic is running on something radiation hardened and GUI layer (with some redundant hardware) can be easily rebooted as necessary.

I don't think that's necessarily true. I've worked with a couple of cacheful CPUs that only used parity checks on caches, not ECC. To get safety, the cache has to be set up as write-through instead of write-back, so that it is almost always safe to throw away a line that suffers a parity error.

At least I've seen Machine Check Exceptions on x86 CPUs about L3 ECC errors on non-Xeon CPUs. I'd presume also other levels are protected.

Re: What computer and software is used by the Falcon 9? (2015)

#150

Post by zeroc8 »

errantspark wrote: post #139
vertex-four wrote: post #130

Earlier quoted context omitted.

In the context of writing reliable software for a spacecraft? Pretty much anything with a reasonable type system, for a start. Maybe C#, or some reasonable subset of C++20, or Rust. Maybe Reason or OCaml.

I mean very clearly the good people at SpaceX have heard of these languages and decided against it. I think JS and Chromium are the best UI kit I can think of in terms of man hours to get X done. If you're careful the only thing I've ever had issues with is latency, but in space if you're in a situation where missing a frame or two is important you're already beyond fucked.

From my experience, Qt/QML is way better for things like that. I mean, the UI does not need to be responsive, does it?

Maybe they couldn't afford the Qt license.

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