Notice the 40 minute estimate to reach 15k ?

That is probably going to be a problem is you expect battery power to get you there. There are a couple of apps around that work out all the electric parameters based on available components. They might or might not be able to accept battery sizes required for such long motor runs. There aren't too many model applications today that require such long, strong runs. Those apps would be worth playing around with once you've got some idea of the motor you might be using.

Efficiency might also be worthwhile. I think inline motors (often with gearing) have a significant edge over outrunners.