Force on a moving object hitting a stationary object... in zero g?

I've been running ideas and thoughts in my head about space travel and I've hit a road block. We know from space shuttle's and space stations that even the smallest asteroid, comet, or space debris (what ever applies) can cause problems. So I what I'm looking for is an equation for how much force would be exerted should, X lb asteroid be hit by a space shuttle (craft) at A (Light years) weighing in at B tons. Now the problem here is that every thing I look up has Gravity in the formula, but we're dealing with 0G so this throws off the entire equation output. Taking it completely out also messes with the numbers.