Hi LJK

Gary has his preferences, I have mine. I think active shielding will be preferred for interstellar travel. And the radiation repair problem may only be a problem due to excessive journey times for low, low speeds.

Gerald Nordley wrote a piece that covered these issues that's worth a read:

Don't Rule Out Interstellar Probes

...though admittedly he's talking 1000 ton probes. I tend to think that's a reasonable size too, for a space-based civilisation. I was probably wrong on the microprobe approach because it's really hard to imagine a tiny self-replicator probe that won't mutate excessively. And microprobes can't have decent optics or communications.

J.D.Bernal and Gary would like to think in moon-sized starships, and while it's not insane I don't think it'll be necessary. We're probably better thinking of small sub-probes buzzing us than the mother-ship deigning to visit. It will be busy building a new batch of motherships for the next set of targets.

Adam