4 ms·
> SpaceX uses ordinary electronics parts in their flight electronics, as opposed to ded- icated radiation-hardened parts, since systems can be made radiation-tol
by 2bitencryption 6y ago
> SpaceX uses ordinary electronics parts in their flight electronics, as opposed to ded-
icated radiation-hardened parts, since systems can be made radiation-tolerant with re-
dundancy, and commercial off-the-shelf components are easier to work with.
Something about this confuses me -- for years, I'm assuming since the earliest days of human spaceflight, the convention has been to used radiation-hardened hardware, yes?
I absolutely see the benefits of not using this expensive, unfamiliar, specialized hardware when you can instead use cheap, well-known, store-bought CPUs that everyone is familiar with and knows how to use.
But... how do you solve the original problem? Does it turn out that radiation is not that big of an issue after all? Is it a big deal, but SpaceX found a workaround? Do you have three CPUs all running the exact same computations and you assume there was no impact from radiation if at least 2/3 give the same result?
It makes me somehow both extremely satisfied, and a little jittery, to know we just flew two humans to the space station on off-the-shelf CPUs :)
- pkaye 6y agoWhat I've heard is that SpaceX doesn't currently go far enough into space yet that the specialized hardware is needed.
- Topgamer7 6y agoThey triplicate the number of CPUs and make them all so the same computation
- OnlyOneCannolo 6y agoThey probably won't all have the exact same bits affected by radiation, and they vote on the results. The architecture gives you fault tolerance and low likelihood of failure. A rad hardened processor will make the likelihood better, but it's not worth it if it's already good enough.
- rurban 6y agoNo, SpaceX did the exact same thing the shuttle did. 3 normal RtLinux Intel boxes running the very same model, with one hardened controller comparing the results. This can run at much higher CPU frequencies to get the required controller speed and HW latencies. This is just for low orbit and very short missions. The longer the missions, the higher the orbit, the more radiation fallouts then. The Moon or Mars missions would need to fall back to hardened CPU's and RAM, but there's not much need for high speed controllers there. Just reliable reboots. 200Mhz is enough. The controller high speed is mostly needed for the earth gravity. Up there it's much more relaxed.
- kanox 6y ago> expensive, unfamiliar, specialized hardware when you can instead use cheap, well-known, store-bought CPUs that everyone is familiar with My impression (from wikipedia) is that several popular radiation-hardened CPUs are just embedded CPUs with a different manufacturing process. They should be as familiar as traditional embedded CPUs, just old and expensive. For example RAD750 is based on PPC750 which can be found in older macs.