The Allen and Eggers discovery, initially treated as a military secret, was eventually published in 1958.[75] Blunt body theory made possible the heat shield designs that were embodied in the Mercury, Gemini, Apollo, and Soyuz space capsules, enabling astronauts and cosmonauts to survive the fiery re-entry into Earth's atmosphere. Some spaceplanes such as the Space Shuttle made use of the same theory. At the time the STS was being conceived, Maxime Faget, the Director of Engineering and Development at the Manned Spacecraft Center, was not satisfied with the purely lifting re-entry method (as proposed for the cancelled X-20 "Dyna-Soar").[76] He designed a space shuttle which operated as a blunt body by entering the atmosphere at an extremely high angle of attack of 40°[77] with the underside facing the direction of flight, creating a large shock wave that would deflect most of the heat around the vehicle instead of into it.[78] The Space Shuttle essentially uses a combination of a ballistic entry (Blunt body theory) and then at an altitude of about 122,000 m (400,000 ft), the re-entry interface takes place.