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>>>>Speed is nothing but acceleration over some time. Acceleration will increase your speed by some certain time 't', but it won't increase your top speed. This is how ion drives work, for example -- they have almost no appreciable thrust, but because they're highly efficient (relatively speaking) a system using ion engines can attain very, very high speeds. It just takes a long time to build up to that point.
>>>>When talking about space ships and "speed", saying it can go such-and-such speed isn't particularly meaningful. This is why many sci-fi stories talk about things in terms of pounds-thrust or G's acceleration, because that's really what matters.

Hook: Thanks for the primer. In this specific case, what matters to the crew is that they have 69 hours of air left. They have to move the ship 1143 km in 64 hours to reach the asteroid that has the iron oxides they have to refine into iron and oxygen (allowing 5 hours for the extraction and refining). They are trying to figure out whether adding a third thruster will give them enough additional thrust to get them there in time.

It's easy enough to say "If I have x kilometers to go, and y hours to get there, I need an *average* speed (taking into account acceleration and deceleration) of z kph to get there. But I don't know how to convert pounds of thrust into kph. I suppose I could be a bit more generic and say "given the pounds-thrust of the two thrusters (without going into specifics), adding a third would boost the thrust by 50%, less a fudge factor to lessen the stresses on the temporary hardpoint..." etc, and not go into as much detail, but I think some detail adds to the realism of the situation. But only if I can do it correctly and nontediously.... Any suggestions? The details of determining how fast they can go and whether they will make it in time only affect a few pages out of the whole book, so it shouldn't be too much trouble to correct them, once I know how to word it.

>>>>Yes, and if you're looking for good feedback quickly, then that's exactly what I would do.

It's worth a shot, anyway. Thanks again.

Mark.