I think the thing that gets me is the reference to the Challenger explosion, 17 years ago. Suddenly in a flash I realize these birds should've been decommisioned and replaced a decade ago and not flying in the 21st century.

When it comes to aircraft and spaceships you simply don't have the luxury of letting the vehicles get old.

I also dont believe in multi-component reusable heat shields, but think that all future craft should have heat-shield "skins" that are produced and installed fresh for each flight. Considering that heat is the greatest enemy and danger of a hypersonic spacecraft re-entering our atmosphere, the heat shields need to be dang near impervious to failure. Yes, I know - expense. But what's the price of a heat shield to the price of the entire craft?

SDAI-Tech1