Do we actually have much data on the failure rates to different kinds of chips to radiation in space? If so ... how?
What conditions have to hold so that when a chip is damaged by radiation you get enough information about it to know which chip had what kind of problem?
The CPUs of Spacecraft Computers in Space
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Re: The CPUs of Spacecraft Computers in Space
#32"A CPU for use in space must first be MIL-STD-883"
Is this just for NASA craft? Are there any regulations for private craft or international standards?
Re: The CPUs of Spacecraft Computers in Space
#33"A CPU for use in space must first be MIL-STD-883" Is this just for NASA craft? Are there any regulations for private craft or international standards?
Depends, but mostly no. No regulations.
Re: The CPUs of Spacecraft Computers in Space
#34Earlier quoted context omitted.
As mentioned in another comment, water is a radiation shield, but ionizing radiation in space will attenuate 50% after 7cm of water (I could be wrong), and if you want a lot of attenuation, you need a lot of water (which is extremely heavy). A small amount of water for shielding is undoubtedly much more massive than simply using bigger, rad-hard processors.
I don't see any comments about water on this post? If we're talking about $50/kg [1] in the future... well... - Sending a few kg of water (or other shielding) to space costs a fraction of the price of a fast non-rad-hardened CPU. - It really costs less than the extra development cost associated with having to use bespoke toolchains. [1] Number from the other space post on the front page today: https://getmeflyingcars…
> I don't see any comments about water on this post?
Looks like it was deleted.
> - Sending a few kg of water (or other shielding) to space costs a fraction of the price of a fast non-rad-hardened CPU.
It doesn’t sound like a few kg is going to cut it. Recall that a 1 kg of water is about 1 L, which gives you about 6 cm of shielding, which is simply not enough. That’s less than 50% attenuation of the ionizing radiation you find in space. Mass increases with the cube of the thickness. If you want 20 cm of shielding, that’s 33 kg, and something like 86% attenuation.
It seems to me like there are better things you can do with your mass, which also needs to be spent on things like fuel for stationkeeping. Lower mass also means more satellites.
> - It really costs less than the extra development cost associated with having to use bespoke toolchains.
POWER is not exactly some obscure ISA. It is well-supported and battle-tested. You don’t need a bespoke toolchain.
Re: The CPUs of Spacecraft Computers in Space
#35Do we actually have much data on the failure rates to different kinds of chips to radiation in space? If so ... how? What conditions have to hold so that when a chip is damaged by radiation you get enough information about it to know which chip had what kind of problem?
Testing is done on earth in lab conditions, and some testing has been done in space. We've had good models of radiation energy and type in space for a while, so you can reproduce type and intensity of radiation on earth to test how the chip will behave. You can also fly chips for testing, where instrumentation and testing are controlled by known working hardware.
Diagnosing novel failures on hardware in space is hard, but the overall types of failures and their underlying physical phenomena are known. Obviously, in the case of a satellite that goes completely unresponsive you can't answer 100%, but you may have sensor data in the leadup to the failure, or from other "nearby" satellites that would allow you partially reproduce conditions before the failure in a test scenario.
Re: The CPUs of Spacecraft Computers in Space
#36So my watch (or maybe headphones even) is several times faster than anything that's ever run a spacecraft?
(I understand why, but that this is so just blows me away)
Re: The CPUs of Spacecraft Computers in Space
#37Space flight computers in the public sector are generally 15-20 years behind the types of hardware we commonly work with on the ground, as I think this page shows. We now have pretty capable low-power SoCs and FPGAs that we've yet to see broadly leveraged for govt. space applications. SpaceX flies Starlink with Xilinx FPGAs, while NASA and DoD are still baselining new platforms on incredibly expensive (albeit rad-har…
The RAD750 (edit - the whole RAD family, there are newer models available) remains the standard because it's the highest performance rad-hard design available, period. If you're putting an expensive satellite in orbit for 5,10 years, the cost of the processors is insignificant compared to everything else. The real problem is that we don't have good solutions for improving the performance of rad-hard designs, so we're…
Could they not offload a lot of compute to ground based computers and submit results back via radio? Or are these real-time applications?
Re: The CPUs of Spacecraft Computers in Space
#38There have been none RAD hard CPUs working in space. https://www.hpe.com/us/en/insights/articles/the-space-statio...
Low Earth Orbit (LEO) which the ISS is in is very different from deep space. You can get away with much less radiation hardening in LEO. For example, I know a company consumer-grade Xilinx MPSoCs with 4xA53 cores at 1.5GHz.
Re: The CPUs of Spacecraft Computers in Space
#39Earlier quoted context omitted.
The RAD750 (edit - the whole RAD family, there are newer models available) remains the standard because it's the highest performance rad-hard design available, period. If you're putting an expensive satellite in orbit for 5,10 years, the cost of the processors is insignificant compared to everything else. The real problem is that we don't have good solutions for improving the performance of rad-hard designs, so we're…
Could they not offload a lot of compute to ground based computers and submit results back via radio? Or are these real-time applications?
For Mars, at least, that would be tens of minutes round trip because of the speed of light.
It works for some things, but for pathfinding it isn’t a great fit.
The other issue is bandwidth between the craft and Earth, which is quite limited.
Maybe there would be benefits to a “orbiting datacenter” around Mars carrying a bunch of rad-hardened compute? I assume NASA has considered this and decided it would be a bad idea.
Re: The CPUs of Spacecraft Computers in Space
#40There have been none RAD hard CPUs working in space. https://www.hpe.com/us/en/insights/articles/the-space-statio...
Low Earth Orbit (LEO) which the ISS is in is very different from deep space. You can get away with much less radiation hardening in LEO. For example, I know a company consumer-grade Xilinx MPSoCs with 4xA53 cores at 1.5GHz.
They literally ship off the shelf laptops and smartphones to the ISS.
They do modify them slightly to remove the lithium-ion batteries, which you do not want inside a space craft.
I think they replace them wit NiMH cells if the devices still need to be battery powered.