Russia and China have recently touted their progress in developing hypersonic vehicles, which fly much faster than the speed of sound, which is 767 mph. Hypersonic missiles are rocket-boosted to high altitude and may be launched from land, sea or air. They fly far faster than any other weapons – more than 3,000 mph and potentially up to 10,000 mph – which makes them difficult to identify, avoid or shoot down. After leading the development of this technology area for decades, the U.S. finds itself behind and investing heavily in the technology to try to keep up.