Developed in great secrecy at Peenemünde on the Baltic coast, the V-2 was a revolutionary, liquid-fuelled rocket, burning a mixture of pure alcohol and liquified oxygen. On its first successful test flight, on October 3rd 1942, the rocket reached a height of 50 miles above the surface of the earth, travelling for most of its trajectory through airless space. As a missile the V-2 was an astonishing technical achievement, indeed the first true weapon of the space age, but its further development was slowed by a series of teething troubles exacerbated by the addition of a high explosive war head. When the V-2 came into service in September 1944 it carried a modified one ton warhead of diluted explosive charge, rendering its effectiveness as a weapon more than offset by the enormous cost of its development. Over a thousand V-2s were eventually launched at London, killing some two and a half thousand people.