I’m curious. Which of the parts back in the day would have failed first and why? And which of the parts would have continued functioning despite radiation?

Computers fail first because the memory content gets corrupted. I can imagine, that power electronics will continue functioning despite radiation.

Apparently regular MOSFETs are affected[1] by the total dose of ionizing radition (TDI) causing important parameters to change, such as threshold voltage (Vgt) and internal resistance (Rds).

So it seems even power electronics are not safe[2], nor microcontrollers/microprocessors and other types of ICs.

[1]: https://nepp.nasa.gov/files/28954/2017-Lauenstein-NSREC-Post... (esp. figure 11)

[2]: https://www.renesas.com/eu/en/products/space-harsh-environme...

Thank you, signed for Renesas newsletter. Very interesting topics.

I think that with modern fiber-optics it might be possible to make a really long robot arm without any sensitive circuits at the extremity.

I'm not sure how fibre optics could help here, an you expand?

They're describing running the computers 100's of meters away with fibre to the robot. But it won't help with motor encoders and sensors that all must be onboard.

Interesting idea though. To some degree is probably possible. No such thing as a rad hardened cmos though

I think the idea is to have a passive bundle of fiber at the far end with all your electronics in the safe zone, like a fiber optic endoscope.

Why couldn't the necessary electronics be shielded with a shroud of lead? It's not like these robots have lunar weight requirements.

Spalling/scatter. In certain radiation environments, shielding makes things worse, as an energetic particle can cause a knock-on flood of even more damaging particles to be emitted if strikes an atom in the shield. Ultimately more mass does help, but we're talking meters-thick, not just another few cm.

The details are a lot more complicated than that. It's just worth keeping in mind that for any given radiation environment, there may be times when either more or less shielding would be a better choice, as counterintuitive as that may seem.