1: By process, where chips are created with special or larger features to better resist cosmic rays. This is Expensive since they're made in very low volumes and the cost of the new fab line can't be spread among many millions of units. Instead, a few thousand chips might be made.
2: By design, where redundant systems such as triple redundant memory or voting computers are used. This is probably the most interesting as you can get into issues like the Byzantine Generals problem here. All the redundancy can be implemented in a single FPGA by simply routing out the design 3 times and using voting logic, assuming the FPGA is large enough.
3: By shielding. Just fly regular chips in a shielded box. This causes thermal issues, but is sometimes necessary, such as in Juno, which has to deal with the enormous radiation flux around Jupiter.
As sending mass to space becomes cheaper I wonder if shielding will become more popular... Maybe there is some oil-like material that could serve bath as a cooling bath and as a radiation shield?
Polyethylene is usually used to shield against cosmic rays. Nearly identical shielding performance as water. Slightly less weight per volume. Can be formed easily and retains its shape.
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?
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.
The most bespoke parts would be tool chain certification, which among other things, covers "if I have source A, then I can be sure resulting machine code does B, not anything else".
And that's something you'll get even if you're running MS-DOS on 286 in space ;-)
