Ship supply use per turn

[capnq]

your ships don't have to maneuver around space debris while in transit?

In general, no.

There's an article in the July 2002 issue of Discover about how mind-boggling empty space is. It mentions that dark nebulae like the Great Rift, with a density of 2000 hydrogen atoms per cubic inch, is still effectively hard vaccuum.

AFAIK, the only place that something as dense as the classic sci-fi asteroid swarm would really exist might be inside a comet's tail, or the accretion disk of a black hole.

Debris will be a problem in places that see a lot of traffic, like planetary orbit, but otherwise there just isn't that much out there to run into.