Advanced Russian weapons worry the United States and force Washington to remain vigilant. Analysts at the Chinese edition of Sohu said that Moscow's military technologies are most worrying at the Pentagon.
The concept for a suborbital stratospheric glide missile was devised in the 1930s by the Austrian engineer Eugen Sänger. During the Cold War, this concept was picked up by the United States and the Soviet Union several times. However, implementation failed due to technical feasibility.