In space you can't turn like a plane because there is no air resistance. The only way to turn is either to reverse all your momentum, or to slingshot around a gravity well.
Do any games use this mechanic? I imagine an easy implementation: Flip to show current speed, allowing for 2 speeds, plus a third speed that must be lost at end of turn by entering orbit. Movepoints are used to adjust velocity and direction (it costs 0 move points to maintain velocity and direction). Turn when you move adjacent to a planet, or enter orbit to slow …