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How NASA built Artemis II’s fault-tolerant computer

cacm.acm.org

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Re: How NASA built Artemis II’s fault-tolerant computer

#111

Post by [deleted] »

themafia wrote: post #109
JumpCrisscross wrote: post #102

Earlier quoted context omitted.

> In the Shuttle they would use command averaging I think the Shuttle, operating only in LEO, had more margin for error. Averaging a deep-space burn calculation is basically the same as killing the crew.

The GNC loop runs several times per second. The desired output will consequently be increased by the working computers to achieve the target. The computer does not "dead reckon" anything. Travelling through Max-Q in Earth atmosphere on ascent is far more dangerous.

[deleted]

Re: How NASA built Artemis II’s fault-tolerant computer

#112

Post by JumpCrisscross »

themafia wrote: post #109
JumpCrisscross wrote: post #102

Earlier quoted context omitted.

> In the Shuttle they would use command averaging I think the Shuttle, operating only in LEO, had more margin for error. Averaging a deep-space burn calculation is basically the same as killing the crew.

The GNC loop runs several times per second. The desired output will consequently be increased by the working computers to achieve the target. The computer does not "dead reckon" anything. Travelling through Max-Q in Earth atmosphere on ascent is far more dangerous.

> Travelling through Max-Q in Earth atmosphere on ascent is far more dangerous

Fair enough. I don't know enough about Orion's architecture to guess at propellant reserves, and how life-or-death each burn actually is.

Re: How NASA built Artemis II’s fault-tolerant computer

#114

Post by Tomte »

jbritton wrote: post #12

I wonder how often problems happen that the redundancy solves. Is radiation actually flipping bits and at what frequency. Can a sun flare cause all the computers to go haywire.

IEC 61508 estimates a soft error rate of about 700 to 1200 FIT (Failure in Time, i.e. 1E-9 failures/hour).

That was in the 2000s though, and for embedded memory above 65nm.

And obviously on earth.

Re: How NASA built Artemis II’s fault-tolerant computer

#115

Post by Arch-TK »

ggm wrote: post #105
dmk wrote: post #3

The quote from the CMU guy about modern Agile and DevOps approaches challenging architectural discipline is a nice way of saying most of us have completely forgotten how to build deterministic systems. Time-triggered Ethernet with strict frame scheduling feels like it's from a parallel universe compared to how we ship software now.

Time triggered Ethernet is part of aircraft certified data bus and has a deep, decades long history. I believe INRIA did work on this, feeding Airbus maybe. It makes perfect sense when you can design for it. An aircraft is a bounded problem space of inputs and outputs which can have deterministic required minima and then you can build for it, and hopefully even have headroom for extras. Ethernet is such a misnomer fo…

A real squirrel would need acorns, I would assume it's a clockwork squirrel too.

Re: How NASA built Artemis II’s fault-tolerant computer

#116

Post by sylware »

dyauspitr wrote: post #54
dmk wrote: post #3

The quote from the CMU guy about modern Agile and DevOps approaches challenging architectural discipline is a nice way of saying most of us have completely forgotten how to build deterministic systems. Time-triggered Ethernet with strict frame scheduling feels like it's from a parallel universe compared to how we ship software now.

Agile is not meant to make solid, robust products. It’s so you can make product fragments/iterations quickly, with okay quality and out to the customer asap to maximize profits.

... and it mechanically promotes planned obsolescence by its nature (likely to be of disastrous quality). The perfect mur... errr... the perfect fraud.

Re: How NASA built Artemis II’s fault-tolerant computer

#117

Post by InsideOutSanta »

ramraj07 wrote: post #31
HNisCIS wrote: post #15

Earlier quoted context omitted.

What would you suggest? Vibe coding a react app that runs on a Mac mini to control trajectory? What happens when that Mac mini gets hit with an SEU or even a SEGR? Guess everyone just dies?

[flagged]

Can't tell if "arrogant nasal engineers" is a typo or a hilarious attempt at an insult.

Re: How NASA built Artemis II’s fault-tolerant computer

#118

Post by gambiting »

So honest and perhaps a bit stupid question.

Astronauts have actual phones with them - iPhones 17 I think? And a regular Thinkpad that they use to upload photos from the cameras. How does all of that equipment work fine with all the cosmic radiation floating about? With the iPhone's CPU in particular, shouldn't random bit flips be causing constant crashes due to errors? Or is it simply that these errors happen but nothing really detects them so the execution continues unhindered?

Re: How NASA built Artemis II’s fault-tolerant computer

#119

Post by InsideOutSanta »

geerlingguy wrote: post #19
arduanika wrote: post #18

Earlier quoted context omitted.

Please, this is hacker news. Nothing else is hard outside of our generic software jobs, and we could totally solve any other industry in an afternoon.

I mean I can just replace Dropbox with a shell script.

"No wireless. Less space than a Nomad. Lame."

No, wait, that was that other site.

Re: How NASA built Artemis II’s fault-tolerant computer

#120

Post by Citizen_Lame »

bluegatty wrote: post #22
geerlingguy wrote: post #19

Earlier quoted context omitted.

I mean I can just replace Dropbox with a shell script.

That's funny because you could! Dropbox started a shell script :) Funny though I would assume HN people would respect how hard real-time stuff and 'hardened' stuff is.

HN audience has shifted, there is less technically minded people and more hustlers and farmers from other social media waste spaces. But alas.
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