streamlining would require knowing from which direction the impactor was coming from. Not possible in space....

Aren't we talking about the Whipple shield on the front of an interstellar craft? So wouldn't we know that most impactors will be coming from the front? I guess a big unknown is the distribution of velocities in the interstellar medium--will most of the particles be sitting there (relativistically-speaking) waiting for the ship to hit them, or will they be moving and coming from all directions?

(as an addendum addition of velocities in relativity ensures that there will never be delta v>c)

Understood. What are the implications for the amount of energy released by the collision? I'm groping in the dark here, admittedly...are you saying that relativity's cap on delta V would cap the energy released? Relativity's so weirdly cool...I guess I'm stuck on conservation of energy, and thinking that the kinetic energy of the two particles would have to add, somehow, even if their relative velocity has to be capped at c. Where does the excess energy go? It's OK, you can say it: I'm soooooo confused.

--Robert