Convair X-12

The Convair X-12, also known as Atlas B, was the second and more developed test vehicle of the Atlas missile programme, following the Convair X-11. Where the X-11 had a single engine, the X-12 was fitted with three, and it was driven by a multistage liquid-fuel rocket. Its first flight took place in July 1958. The X-12 was the first flying vehicle to use the one-and-a-half stage rocket arrangement that later became a hallmark of the Atlas programme. According to the German article it was the first American rocket after the Soviet R-7 whose range of 10,179 km could be called intercontinental. The article gives no further technical data, so mass and dimensions are not stated here.