The unusual trajectories of these missiles would allow them to approach their targets at roughly 12 to 50 miles above the earth’s surface. That’s below the altitude at which ballistic missile interceptors — such as the costly American Aegis ship-based system and the Thaad ground-based system — are now designed to typically operate, yet above the altitude that simpler air defense missiles, like the Patriot system, can reach.
Officials will have trouble even knowing where a strike would land. Although the missiles’ launch would probably be picked up by infrared-sensing satellites in its first few moments of flight, Griffin says they would be roughly 10 to 20 times harder to detect than incoming ballistic missiles as they near their targets. They would zoom along in the defensive void, maneuvering unpredictably, and then, in just a few final seconds of blindingly fast, mile-per-second flight, dive and strike a target such as an aircraft carrier from an altitude of 100,000 feet.
During their flight, the perimeter of their potential landing zone could be about as big as Rhode Island. Officials might sound a general alarm, but they’d be clueless about exactly where the missiles were headed. “We don’t have any defense that could deny the employment of such a weapon against us,” Gen. John E. Hyten, commander of United States Strategic Command, told the Senate Armed Services Committee in March 2018. The Pentagon is just now studying what a hypersonic attack might look like and imagining how a defensive system might be created; it has no architecture for it, and no firm sense of the costs.
Developing these new weapons hasn’t been easy. A 2012 test was terminated when the skin peeled off a hypersonic prototype, and another self-destructed when it lost control. A third hypersonic test vehicle was deliberately destroyed when its boosting missile failed in 2014. Officials at Darpa acknowledge they are still struggling with the composite ceramics they need to protect the missiles’ electronics from intense heating; the Pentagon decided last July to ladle an extra $34.5 million into this effort this year.
The task of conducting realistic flight tests also poses a challenge. The military’s principal land-based site for open-air prototype flights — a 3,200-acre site stretching across multiple counties in New Mexico — isn’t big enough to accommodate hypersonic weapons. So fresh testing corridors are being negotiated in Utah that will require a new regional political agreement about the noise of trailing sonic booms. Scientists still aren’t sure how to accumulate all the data they need, given the speed of the flights. The open-air flight tests can cost up to $100 million.
The most recent open-air hypersonic-weapon test was completed by the Army and the Navy in October 2017, using a 36,000-pound missile to launch a glider from a rocky beach on the western shores of Kauai, Hawaii, toward Kwajalein Atoll, 2,300 miles to the southwest. The 9 p.m. flight created a trailing sonic boom over the Pacific, which topped out at an estimated 175 decibels, well above the threshold of causing physical pain. The effort cost $160 million, or 6 percent of the total hypersonics budget proposed for 2020.
In March 2018, Vladimir Putin, in the first of several speeches designed to rekindle American anxieties about a foreign missile threat, boasted that Russia had two operational hypersonic weapons: the Kinzhal, a fast, air-launched missile capable of striking targets up to 1,200 miles away; and the Avangard, designed to be attached to a new Sarmat intercontinental ballistic missile before maneuvering toward its targets. Russian media have claimed that nuclear warheads for the weapons are already being produced and that the Sarmat missile itself has been flight-tested roughly 3,000 miles across Siberia. (Russia has also said it is working on a third hypersonic missile system, designed to be launched from submarines.) American experts aren’t buying all of Putin’s claims. “Their test record is more like ours,” said an engineer working on the American program. “It’s had a small number of flight-test successes.” But Pentagon officials are convinced that Moscow’s weapons will soon be a real threat.