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How NASA built Artemis II’s fault-tolerant computer

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

#211

Post by budman1 »

ehnto wrote: post #204
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…

It still lives on as a bit of a hard skill in automotive/robotics. As someone who crosses the divide between enterprise web software, and hacking about with embedded automotive bits, I don't really lament that we're not using WCET and Real Time OSes in web applications!

ever use wordstar on Z80 system with a 5 MB hard drive?

responsive. everything dealing with user interaction is fast. sure, reading a 1 MB document took time, but 'up 4 lines' was bam!.

linux ought to be this good, but the I/O subsystem slows down responsiveness. it should be possible to copy a file to a USB drive, and not impact good response from typing, but it is not. real time patches used to improve it.

windows has always been terrible.

what is my point? well, i think a web stack ran under an RTOS (and sized appropriately) might be a much more pleasurable experience. Get rid of all those lags, and intermittent hangs and calls for more GB of memory.

QNX is also a good example of an RTOS that can be used as a desktop. Although an example with a lot of political and business problems.

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

#212

Post by therobots927 »

randomNumber7 wrote: post #203
therobots927 wrote: post #181

Earlier quoted context omitted.

What’s your point?

The average coder in the 1970s was a lot smarter than today. Think about the people who would be interested to start a career in this field at that time.

Oh I see what you mean. I agree 100%

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

#213

Post by therobots927 »

nairboon wrote: post #191
therobots927 wrote: post #184

Earlier quoted context omitted.

Economics is propaganda. It’s not an empiracle science, and it’s claims are mostly used to promote ideologies consistent with government policy or the ideology of powerful individuals with the surplus’s wealth available to pay someone to build a quantitative defense of said ideology. What else would you call it?

It's a social science? Economics is much broader and much less unified than you purport it to be. The (social) science of (in this case) Macroeconomics is just that, an observational science, a bunch of theories and observations (controlled experiments are not really feasible). The propaganda is caused by politicians, administrators, and policymakers, not really the scientists. There I agree with you, central bankers…

Social scientist carry out experiments / causal analysis on granular data. Macro economics (not micro) I should clarify meets the definition of propaganda because its theories do not have solid backing with experimentation or data. It is primarily used by the state to manufacture consent for economic policies that implement incentive structures that benefit the most wealthy people in society. It’s not that complicated.

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

#216

Post by weli »

derbOac wrote: post #156
weli wrote: post #130

Earlier quoted context omitted.

Mises never claimed that the free market produced the most optimal solutions at a given moment. In fact Mises explicitly stated many times that the free market does indeed incur in semi-frequent self-corrections, speculations and manipulations by the agents. What Mises proposition was - in essence - is that an autonomous market with enough agents participating in it will reach an optimal Nash equilibrium where both o…

An "autonomous market with enough agents" is carrying a lot of weight there, like "rational actors" and "as sample size goes to infinity'.

It is not carrying a lot of weight. Macroeconomics are different from microeconomics. On a micro scale agents have enough weight on the system where a specific action might break a model. On a macro scale each individual agent's action carries less weight and therefore the system becomes predictable.

On a micro scale it is possible, and sometimes favorable, to intervene. On a macro scale to intervene economically becomes impossible due to the economic calculation problem. It is widely accepted in modern economics that the unit of maximum extent where economical intervention is possible is a business/company/enterprise. Or in sociological terms the maximum unit is the family. Anything broader than that and the compound effect of the economic calculation problem becomes apparent and inefficiencies accumulate. Autonomous decentralized mechanisms (like a free market) are the only solution to it, but not the most optimal.

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

#217

Post by PunchyHamster »

budman1 wrote: post #211
ehnto wrote: post #204

Earlier quoted context omitted.

It still lives on as a bit of a hard skill in automotive/robotics. As someone who crosses the divide between enterprise web software, and hacking about with embedded automotive bits, I don't really lament that we're not using WCET and Real Time OSes in web applications!

ever use wordstar on Z80 system with a 5 MB hard drive? responsive. everything dealing with user interaction is fast. sure, reading a 1 MB document took time, but 'up 4 lines' was bam!. linux ought to be this good, but the I/O subsystem slows down responsiveness. it should be possible to copy a file to a USB drive, and not impact good response from typing, but it is not. real time patches used to improve it. windows…

>what is my point? well, i think a web stack ran under an RTOS (and sized appropriately) might be a much more pleasurable experience. Get rid of all those lags, and intermittent hangs and calls for more GB of memory.

... it's not the OS that's source of majority of lag

Click around in this demo https://tracy.nereid.pl/ Note how basically any lag added is just some fancy animations in places and most of everything changes near instantly on user interaction (with biggest "lag" being acting on mouse key release as is tradition, not click, for some stuff like buttons).

This is still just browser, but running code and displaying it directly instead of going thru all the JS and DOM mess

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

#218

Post by nnevod »

ehnto wrote: post #204
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…

It still lives on as a bit of a hard skill in automotive/robotics. As someone who crosses the divide between enterprise web software, and hacking about with embedded automotive bits, I don't really lament that we're not using WCET and Real Time OSes in web applications!

I suppose that rough-edgeness of the RTOSes is mostly due to that mainstream neglect for them - they are specific tools for seasoned professionals whose own edges are dent into shapes well-compatible for existing RTOSes.

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

#219

Post by doublerabbit »

bharat1010 wrote: post #199

The part about triple-redundant voting systems genuinely blew my mind — it's such a different world from how most of us write software day to day, and honestly kind of humbling.

The Hyperia roller coaster ride at Thorpe Park uses triple-redundant voting. Which I thought was cool.

> It’s a complex machine. There’s three computers all talking to each other for a start, and they have to agree on everything.

Primary, Real-Time Secondary and Third for regulating votes.

https://www.bbc.co.uk/news/articles/ckkknz9zpzgo

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

#220

Post by anordin95 »

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 initially found this odd too. However, I think the catastrophic failure probability is the same as the prior system, and presumably this new design offers improvements elsewhere.

Under the 3-voting scheme, if 2 machines have the same identical failure -- catastrophe. Under the 4 distinct systems sampled from a priority queue, if the 2 machines in the sampled system have the same identical failure -- catastrophe. In either case the odds are roughly P(bit-flip) * P(exact same bit-flip).

The article only hints at the improvements of such a system with the phrasing: " simplifies the complex task", and I'm guessing this may reduce synchronization overhead or improve parallelizability. But this is a pretty big guess to be fair.

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