Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

How NASA built Artemis II’s fault-tolerant computer

cacm.acm.org

Post reply on HN
Print view View original

91–100 of 257 posts

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

#91

Post by anthonj »

__d wrote: post #34

Does anyone have pointers to some real information about this system? CPUs, RAM, storage, the networking, what OS, what language used for the software, etc etc? I’d love to know how often one of the FCMs has “failed silent”, and where they were in the route and so on too, but it’s probably a little soon for that.

Nasa CFS, is written is plain C (trying to follow MISRA C, etc). It's open on girhub abd used by many companies. It's typically run over freertos or RTEMS, not sure here.

Personally I find the project extremely messy, and kinda hate working with it.

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

#93

Post by FabHK »

MikeTheGreat wrote: post #84
vasco wrote: post #72

Earlier quoted context omitted.

If you have a point to make, make it.

What my question is hinting at is that there's actually some really interesting engineering around resolving what happens when the systems disagree. Things like Paxos and Raft help make this much more tractable for mere mortals (like myself); the logic and reasoning behind them are cool and interesting.

Though here the consensus algorithm seems totally different from Paxos/Raft. Rather it's a binary tree, where every non-leaf node compares the (non-silent) inputs from the leaf, and if they're different, it falls silent, else propagates the (identical) results up. Or something something.

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

#94

Post by FabHK »

georgehm wrote: post #58

>Effectively, eight CPUs run the flight software in parallel. The engineering philosophy hinges on a >“fail-silent” design. The self-checking pairs ensure that if a CPU performs an erroneous calculation >due to a radiation event, the error is detected immediately and the system responds. >“A faulty computer will fail silent, rather than transmit the ‘wrong answer,’” Uitenbroek explained. >This approach simplifies the…

Indeed. It seems like system 1 and 2 could fail identically, 3, 4, 5, 6, 7, 8 are all correct, and as described the wrong answer from 1 and 2 would be chosen (with a "25% majority"??).

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

#95

Post by kukkeliskuu »

danhon wrote: post #7
ramraj07 wrote: post #6

Earlier quoted context omitted.

I take the opposite message from that line - out of touch teams working on something so over budget and so overdue, and so bureaucratic, and with such an insanely poor history of success, and they talk as if they have cured cancer. This is the equivalent of Altavista touting how amazing their custom server racks are when Google just starts up on a rack of naked motherboards and eats their lunch and then the world. Le…

You mean like this? "With limited funds, Google founders Larry Page and Sergey Brin initially deployed this system of inexpensive, interconnected PCs to process many thousands of search requests per second from Google users. This hardware system reflected the Google search algorithm itself, which is based on tolerating multiple computer failures and optimizing around them. This production server was one of about thir…

The biggest innovation from Google regarding hardware was understanding that the dropping memory prices had made it feasible to serve most data directly from memory. Even as memory was more expensive, you could serve requests faster, meaning less server capacity, meaning reduced cost. In addition to serving requests faster.

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

#96

Post by pjerem »

object-a wrote: post #9

How big of a challenge are hardware faults and radiation for orbital data centers? It seems like you’d eat a lot of capacity if you need 4x redundancy for everything

Orbital data centers are still nothing more than the current hyperloop.

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

#98

Post by psd1 »

therobots927 wrote: post #74
carefree-bob wrote: post #66

Earlier quoted context omitted.

During the time of the first Apollo missions, a dominant portion of computing research was funded by the defense department and related arms of government, making this type of deterministic and WCET (worst case execution time) a dominant computing paradigm. Now that we have a huge free market for things like online shopping and social media, this is a bit of a neglected field and suffers from poor investment and mind…

Contrary to propaganda from the likes of Ludwig von Mises, the free market is not some kind of optimal solution to all of our problems. And it certainly does not produce excellent software.

I can't think of a time when I've found an absolutist position useful or intelligent, in any field. Free-market absolutism is as stupid as totalitarianism. The content of economics papers does not need to be evaluated to discard an extreme position, one need merely say "there are more things in earth and heaven than are dreamed of in your philosophies"

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

#99

Post by alfons_foobar »

georgehm wrote: post #58

>Effectively, eight CPUs run the flight software in parallel. The engineering philosophy hinges on a >“fail-silent” design. The self-checking pairs ensure that if a CPU performs an erroneous calculation >due to a radiation event, the error is detected immediately and the system responds. >“A faulty computer will fail silent, rather than transmit the ‘wrong answer,’” Uitenbroek explained. >This approach simplifies the…

I wondered about this as well.

OTOH, consider that in the "pick the majority from 3 CPUs" approach that seems to have been used in earlier missions (as mentioned in the article) would fail the same way if two CPUs compute the same erroneous result.

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

#100

Post by CubicalOrange »

georgehm wrote: post #58

>Effectively, eight CPUs run the flight software in parallel. The engineering philosophy hinges on a >“fail-silent” design. The self-checking pairs ensure that if a CPU performs an erroneous calculation >due to a radiation event, the error is detected immediately and the system responds. >“A faulty computer will fail silent, rather than transmit the ‘wrong answer,’” Uitenbroek explained. >This approach simplifies the…

the probability of simultaneous cosmic ray bit-flip in 2 CPUs, in the same bit, is ridiculously low, there might be more probability of them getting hit by a stray asteroid, propelled by a solar flare.

but still, murphy's law applies really well in space, so who knows.

Post reply on HN