The missile-defense conundrum: It takes a hypersonic missile to shoot down a hypersonic missile

If it takes a hypersonic missile to shoot down a hypersonic missile, then America’s missile defense program has a problem.

It needs to invent not just a missile defense interceptor, but one that is fast and agile enough to hit a Mach 5-plus vehicle maneuvering through the atmosphere.

That’s just one of many issues highlighted in a new Government Accountability Office (GAO) report on the Missile Defense Agency (MDA) plan to develop counter-hypersonic weapons. Auditors found that MDA is relying on technology that is unproven and likely not mature enough for deployment for many years.

Even Department of Defense officials don’t seem that confident in MDA’s effort to develop a Glide Phase Interceptor (GPI) intended to shoot down hypersonic missiles during the glide – or middle – segment of its flight, in between launch and the final descent on to the target.

“DOD officials briefed on the GPI effort describe it as a significant undertaking that will be technically very challenging to accomplish,” GAO said.

hypersonic missile defense Russian Kinzhal — A Russian air-launched hypersonic Kinzhal missile on a MiG-31. The Pentagon is thinking of ways to counter adversaries’ hypersonic missiles. (Russian presidential administration)

Officials in DoD’s Research and Engineering office admitted that designing counter-hypersonic missiles would be at least as difficult as developing interceptors to shoot down ICBMs.

“The GPI effort would be at least as technically complex as the Next Generation Interceptor, currently MDA’s most challenging program. As we have found, building an interceptor capable of defeating a hypersonic glide vehicle is uniquely challenging, particularly because a hypersonic vehicle itself is difficult to build,” the told GAO.

“In general, intercept systems must be able to outperform their target in order to complete an intercept, often by a significant margin. Consequently, in order to achieve an intercept of a hypersonic target, a new GPI missile would have to operate in hypersonic flight conditions while also exceeding adversary hypersonic systems in key areas, such as speed or maneuverability.”

In fact, the U.S. has developed hypersonic anti-ICBM interceptors. The 1960s Sprint could accelerate to Mach 10 within seconds of launch, but it was only briefly deployed because of arms control treaties and the realization that the Safeguard nationwide antiballistic missile (ABM) system was unfeasible against a mass strike by Soviet missiles armed with multiple nuclear warheads.

Given the Missile Defense Agency’s existing work on defense against ICBMs, it seems logical that they would be tasked with countering hypersonic missiles. However, stopping hypersonic missiles – which travel faster than Mach 5 – will be a greater challenge. ICBMs descend through the atmosphere at speeds greater than Mach 20, but at least they are on a predictable ballistic trajectory. In contrast, hypersonic missiles traverse the upper atmosphere, enabling winged vehicles to achieve both high speeds and maneuver like airplanes.

paths of missiles — This graphic from The Center for Strategic and Budgetary Assessments shows the different flight paths used by hypersonic boost-glide vehicles as compared to hypersonic cruise missiles, and at the very top, traditional ballistic missiles.

MDA’s counter-hypersonic efforts seem plagued by the same problems that have dogged its anti-ICBM programs. GAO found that the GPI program lacked independent assessments to determine whether crucial technologies are sufficiently mature. Nor does MDA appear likely to succeed in accelerating prototype deployment in 2028 instead of 2032, as originally scheduled.

“MDA did not plan to obtain an independent technological risk assessment to determine the maturity of the technologies before proceeding with development,” GAO noted. “In addition, MDA did not plan to obtain an independent cost estimate.”

As for the Hypersonic and Ballistic Tracking Space Sensor (HBTSS), a space-based sensor system to detect hypersonic and ballistic missiles, the program may overlap with efforts by the Space Force and DOD’s Space Development Agency.

“More clearly delineated roles and responsibilities would help avoid duplication, overlap, or fragmented capabilities among MDA and other DOD space agencies,” GAO concluded.

Michael Peck is a contributing writer for Sandboxx and Forbes. He can be found on Twitter and LinkedIn.