Faget, Petynia, and Taub's first swing engine design. 1 = External Tank; 2A = mounting ring for four engines (thrust position on External Tank); 2B = mounting ring for four engines (stored position in Orbiter aft fuselage); 3 = joint linking lower swing arm to engine ring (1 of 2)); 4 = lower swing arm (1 of 2); 5 = upper swing arm (1 of 2); 6 = joint linking upper swing arm to Orbiter aft fuselage (1 of 2); 7 = trailing edge of wing (1 of 2); 8 = opening in aft fuselage for engine cluster storage; 9 = solid-propellant abort rocket (1 of 2); 10 = vertical stabilizer. Image: NASA/U.S. Patent Office. 