A general background piece in Science (hopefully outside their paywall)
snip
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Since the dawn of the Cold War, the Pentagon has periodically thrown its weight behind the development of maneuverable hypersonic weapons, only to shy away when technological hurdles such as propulsion, control, and heat resistance proved daunting. “You see a flurry of activity, a lot of investment, and then we conclude it’s a bridge too far,” says aerospace engineer Mark Lewis, director of defense research and engineering for modernization at the U.S. Department of Defense (DOD). “The community was underfunded and largely forgotten for many years,” adds Daniel DeLaurentis, director of Purdue University’s Institute for Global Security and Defense Innovation.
Now, DOD is leading a new charge, pouring more than $1 billion annually into hypersonic research. Competition from ambitious programs in China and Russia is a key motivator. Although hype and secrecy muddy the picture, all three nations appear to have made substantial progress in overcoming key obstacles, such as protecting hypersonic craft from savage frictional heating. Russia recently unveiled a weapon called the Kinzhal, said to reach Mach 10 under its own power, and another that is boosted by a rocket to an astonishing Mach 27. China showed off a rocket-boosted hypersonic glide vehicle (HGV) of its own, the Dongfeng-17, in a recent military parade. The United States, meanwhile, is testing several hypersonic weapons. “It’s a race to the Moon sort of thing,” says Iain Boyd, an aerospace engineer at the University of Colorado, Boulder. “National pride is at stake.”
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