The Space Age is usually said to begin with the launch of Sputnik 1 on October 4, 1957. But the Sputniks were not really the first vehicles to enter outer space-the long-range missiles were. The ICBMs in particular penetrate well beyond the Earth's atmosphere. As these weapons carriers arch over and fall back, slamming into the atmosphere at very high speed, their kinetic energies are suddenly converted into heat. Reentry heating is so severe that an unprotected missile and its warhead can be destroyed upon reentry into the atmosphere. This Space Age problem arose in the mid-1950s, several years before Sputnik.
NACA began work on the atmospheric entry problem as soon as it was recognized. In spite of a substantial commitment of NACA personnel and facilities, the solution of this critical problem was slowed by two serious deficiencies: ignorance of what was really happening from an analytical standpoint and the lack of test facilities that could duplicate the temperatures, speeds, and gas dynamics typical of missile reentry.