[Nik]

However you do the math, your tech must ripple 'OverSpace'. Early ships vary: Some look like mutant paddle-steamers, with multi-finned gubbins at side, quarter or stern. A 'caterpillar' configuration lends itself to elegant outriggers. The cranky Vortex Drive's giant 'rotor' still suggests 'air-boat'. A Casimir-Warshawski's splendid vanes can resemble sails. Modern designs, of course, keep their workings inside the hull.

Old or new tech, all must drive the ship and, rudderless, steer with thrust. Mr Newton keeps a separate ledger for OverSpace, with RealSpace momentum set aside until BreakOut. You can, with care, boost or brake that Real Space cache while in OverSpace. There's even three good reasons to do it...

Stars move. They lie so unchangingly upon the sky, but vast distances deceive. Except for exotica, like a dashing interloper from the vast Halo, our local stars swirl in the Disk of our Galaxy. Moving 135 miles per second or there-abouts, they take a quarter-billion years per wide orbit. Some share 'Common Proper Motion', or form a 'Moving Group'. Others approach, cross, recede quite sedately. Ten, twenty miles per second difference includes most Disk stars' drift. A few do scoot at twice that speed, or more. Clusters may eject their smallest to roam alone, a binary star's death may fling a companion wild and wide. 100 miles per second for widows or orphans is unusual, but 350 is not unknown.

Planets also move. They orbit their star at 5, 10, 20 miles per second, may offer a grav-assist sling-shot. The space-dock adds 5 miles per second LEO, or 2 if geo-stand.

Stars', planets', stations' speeds add, subtract, gyre and gimble, play 'Catch If Catch Can' with schedules. The third reason for cacheing RealSpace speed is real distance.

Eight light-hours to or from a g-well's brim is a long, long way...