This model is based off of a proposal for a rocket-driven bomber that was intended to be used to bomb New York City after taking off from continental Europe. After climbing to 80km or more the aircraft would have "skipped" off of the upper atmosphere several times on its way to America. Over New York, it would release a "dirty" atomic bomb which would have scattered radioactive metallic uranium over the city.
Artist's rendering of the Sanger bomber accelerating on the launch ramp. The large module behind the bomber is a booster driven by dozens of liquid-fueled engines.