Feather configuration for reentry used in SpaceshipOne, they say, significantly reduces heat loads on reentry by encountering most drag and significantly reducing a large amount kinetic energy at much higher altitude.
How does this configuration work at lower air density? Efficiently enough to reduce intensive thermal encounter later?
What is its feasibility for different reentry speed ranges in other applications?
At even lower air density the drag induced would be proportionally less. Any speed you do reduce though would reduce the peak heating dramatically because heat rate is proportional to the square of the speed at any time. The net result is likely that you shift the peak heating point to earlier when you're going faster but still less heating than before because you're at the max heating point when the air is thinner. So, the answer is to feather as soon as possible in your profile if your objective is to have the maximum impact on peak heating rate. Whether this improvement in peak heating is sufficient to make this technique feasible in other applications is a trade between the weight and complexity (risk) of the feathering system and what it saves you in weight of insulation and risk of thermal issues for that particular application's flight profile. For reentry from orbit, it seems unlikely the excess mass of the feathering system would be worth it since you have so much velocity to shed that feathering will only take a little bit out so you still have to have a very robust thermal protection system.
