Thanks for your reply.
I understnd the structural and thermal superioriy of Ti over Al, but I thought the temperatures required to compromise the structural integrity of Al would cook anyone inside the vehicle anyway, rendering the subject moot.
It is a lot smaller problem to keep certain parts (passenger cabin, etc.) cool than to keep the entire structure cool. Remember that you only have a few minutes of high temps.
The whole thing gets a lot simpler if you minimize reentry heating along with maximizing the heat tolerance of the structure. Shuttle is exactly the opposite case: maximum reentry heating and minimal tolerance for structural heating. This mandated both fragile refractory heat shielding and an intolerance for breaks in that heat protection. This is a big part of the reason the shuttle is so expensive. The heat shielding must be rigorously inspected and there is a lot of it.