The term "astronaut" is given to anyone who has flown to 100 km, or the height at which something can be put into orbit, even if only for a short time because of what you called atmospheric drag...that's why the pilot of SpaceShipOne is the first civilian "astronaut"...plus SpaceShipOne DID have a heat shield...more commonly called a Thermal Protection System (or TPS). Look it up at scaled.com. Any and all vehicles traveling to those heights need a TPS of some sort so that they do not overheat the structure, systems, or pilots/passengers upon there return to earth...it's been fun...i gotta get back to work