 PS-1 included addition of wingtip-mounted ramjets to supplement the main engines and a canard mounted above and behind the cockpit.PS-2 included wing extensions, an extended nose with retractable canard, two additional vertical stabilizers mounted on the wings, and four large ramjets.Estimated performance included sustained speeds of Mach 3 at 95,000 feet and vertical climb rate above 40,000 feet of Mach 2.5.