Re: What if the Columbia had landing-skids?
If the Columbia had skids instead of tires, and IF the cause of the accident was an exploding tire blowing open the gear well and causing aerodynamic breakup, maybe Columbia could have survived. And if wishes were horses, we'd all be eating steak.
Skids work as landing systems, but require a specialized landing strip designed for them, like at Edwards. They can have problems too. I have no idea if skids have ever been considered for something as large as the Shuttle.