The liklihood of a particular structure being hit is very, very small. Negligible over the operational lifetime of the device. In the long-term vision of scale

The liklihood of a particular structure being hit is very, very small. Negligible over the operational lifetime of the device. In the long-term vision of scaled-up nanotechnology, there will of course have to be redundancy and mechanisms for disabling, removing, and recycling (or incinerating) mechanisms destroyed by cosmic rays. But in the near-term, it is an ignorable risk.