Blackstar (spacecraft) - Wikipedia
Blackstar as a two stage to orbit system, comprising a high-speed jet "mothership" aircraft (which Aviation Week referred to as the SR-3). Its description of SR-3 is similar to the North American B-70 Valkyrie Mach 3 strategic bomber, and to patents filed in the 1980s by Boeing. The SR-3 would carry a second, smaller airframe, codenamed the XOV (eXperimental Orbital Vehicle) underneath, between its two laterally separated engine-banks, containing each 2 or 3 engines. This rocket-powered spacepla