[demosthenes the elder]

I haven't kept up on the aurora rumors, but i seem to recall speculation that this thing had propulsion based on using the entire aft surface of the body as an aerospike-like reaction surface, burning fuel and deriving massive thrust as a sort of "external combustion" engine - supposedly very efficient at extremely high altitudes.

[anobjectivist]

I'm vaguely familiar with the aerospike engine, how far has the idea been taken?

[SSN558]

Platelet technology was used. This is the same technology used to cool ICBM and several advanced interceptor reentry vehicles. Thousands of foil platelets chemically etched with tiny holes are stacked up and fused together to form solid structure. Liquid Nitrogen, Helium, or Hydrogen is bled from the skin for cooling purposes. A screaming, Mach 24, white hot reentry vehicle needs this. When liquid or slush hydrogen is used it serves a dual purpose. The Leading Mach cone can be used as a rocket nozzle and aeroheating sustains the combustion providing additional thrust.