Questions:

- does the jump drive preserve the speed that you had before the jump? Or maybe you can jump only if you are "still" in space? Still compared to what? The star? The planet?

- If the latter is true, after jump are you "still" compared to the new planet? Or the new Star? Or the old ones?

I am thinking about the case where a spaceship is chased and needs to reach jump distance and jump as fast as possible. In that case the formula (for m drive) in the book (t = 2* sqrt(d/a) ) would not apply because that is correct only with a flight profile where you start from 0 speed, accelerate (+a) for half of the trip and decelerate (-a) for the remaining half reaching, again, 0 speed. Decelerating while chased is not the best strategy. What would be the m drive and j drive time calculations in that case where the characters use a sensible strategy (of not slowing down)? Or maybe it is NECESSARY to have 0 speed for jumping...