Anything big enough to worry about hitting (that is, anything big enough to see with a strong magnifying glass) goes through the first field and comes out with a very strong negative charge all over its surface. As it enters the second field, it’s repelled away from the path of the ship. If the object is too big to be pushed around this way, we can sense it at a greater distance and maneuver out of its way.
Interesting explanation of how their near-light-speed space travel works.
