Re: Shuttle tile design
The tile design is, like most engineering, a series of tradeoffs. Among them are:
-- Large tile size vs. complexity of application and manufacture for smaller tiles.
-- Fragility vs. light weight.
When you are protecting an aluminum structure, you need all the heat protection you can get. Some older designs, like Dyna-Soar, used exotic, high-temperature metals. Very heavy. There are other thermal protection ideas, including some recent advanced metallic concepts that aren't that heavy, but are not really practical to retrofit to current orbiters.