Silbervogel, German for silver bird, was a design for a rocket-powered sub-orbital bomber aircraft produced by Eugen Sänger andIrene Bredt in the late 1930s for The Third Reich/Nazi Germany. It is also known as the RaBo (Raketenbomber or "rocket bomber"). It was one of a number of designs considered for the Amerika Bomber mission, which started out in the spring of 1942 being focused solely on trans-Atlantic range piston-engined strategic bombers, like the Messerschmitt Me 264 and Junkers Ju 390, the only two airframe types actually built and flown for the competition. When Walter Dornberger attempted to create interest in militaryspaceplanes in the United States after World War II, he chose the more diplomatic term antipodal bomber.
The design was a significant one, as it incorporated new rocket technology, and the principle of the lifting body, foreshadowing future development of winged spacecraft such as the X-20 Dyna-Soarof the 1960s and the Space Shuttle of the 1970s. In the end, it was considered too complex and expensive to produce. The design never went beyond mock up test.
The Silbervogel was intended to fly long distances in a series of short hops. The aircraft was to have begun its mission propelled along a 3 km (2 mi) long rail track by a large rocket-powered sled to about 800 km/h (500 mph). Once airborne, it was to fire its own rocket engine and continue to climb to an altitude of 145 km (90 mi), at which point it would be travelling at some 5,000 km/h (3,100 mph). It would then gradually descend into the stratosphere, where the increasing air density would generate lift against the flat underside of the aircraft, eventually causing it to "bounce" and gain altitude again, where this pattern would be repeated. Because of drag, each bounce would be shallower than the preceding one, but it was still calculated that the Silbervogel would be able to cross the Atlantic, deliver a 4,000 kg (8,800 lb) bomb to the continental US, and then continue its flight to a landing site somewhere in the Japanese held Pacific, a total journey of 19,000 to 24,000 km (12,000 to 15,000 mi).
Postwar analysis of the Silbervogel design involving a mathematical control analysis unearthed a computational error and it turned out that the heat flow during the initial re-entry would have been far higher than originally calculated by Sänger and Bredt; if the Silbervogel had been constructed according to their flawed calculations the craft would have been destroyed during re-entry. The problem could have been solved by augmenting the heat shield, but this would have reduced the craft's already small payload capacity.