Repulsorlifts are magical. They levitate ships with no external outputs. They're also perfectly well suited to explain how a fragment of a ship can crash from a high altitude without being destroyed. As an anti-gravity device, repulsorlifts can greatly reduce or eliminate the need for any orbital velocity, making re-entry much more viable. And in the same vein, they can reduce a ship's effective gravitational mass enough that its terminal velocity is survivable.