[Space, Spaceships] Armor needed for Aerobraking/Re-entry

[DaltonS]

Originally Posted by RogerBW

My rule of thumb, from back in the 3e days, is DR 100 (i.e. dDR 10) on either the front or the back.

That's a bit much for a small ship with medium advanced (TL9) armor.

Originally Posted by RogerBW

To be fair, the longer you're prepared to take over re-entry or the more dV you're willing to spend, the less heat shielding you need. (An extreme form of this is Vertical Landing, see the box on Spaceships p. 40; that basically brakes to a stop at orbital altitude, then descends slowly.) If you don't mind taking many hours, and you have enough manoeuvre capacity to stay under control, you can decelerate over multiple passes getting a little lower and a little slower each time, and use very little heat shielding.

Ah, but aerobraking is all about using atmospheric friction to provide the ΔV to transition from escape to orbital velocity. There should be an equation to calculate how long it takes. Maybe N=k*ΔV/A where N is the number of passes required, ΔV is velocity that needs to be shed to attain orbit, A is the ship's armor in dDR and k is a constant. Not sure how to convert N into time units. (Atmosphere density is probably a factor too.)

Dalton “because 'how long it takes' can be critical” Spence