WASHINGTON — The Pentagon’s ambitious flight test schedule for hypersonic weapons could be at risk due to test range limitations, according to a Government Accountability Office report issued March 22.

The Defense Department plans to conduct as many as 40 flight tests of hypersonic weapons in the next five years, but logistical problems could make achieving existing schedules difficult, the report states.

There is just one long-range flight-test corridor, the GAO states, “but it will not by itself be able to support this pace of testing.”

If hypersonic development programs can’t conduct planned flight tests, “they will be forced to either proceed to an operational capability with fewer tests (and thus less knowledge), or to accept the delay, with schedule and cost consequences,” according to the report.

The Department of Defense is trying to quickly develop and field hypersonic weapons to stay ahead of potential threats from Russia and China. Both countries have robust development and fielding efforts for hypersonic weapons. Hypersonic weapons are capable of flying about five times the speed of sound, or Mach 5, and they can maneuver between varying altitudes and azimuths, making them difficult to detect.

The GAO counted 70 U.S. efforts to develop hypersonic weapons and technologies with an estimated cost of $15 billion from fiscal 2015 through fiscal 2024. While some of these efforts are in collaboration with NASA and the Department of Energy, the majority come from within the DoD.

The Army and Navy plan to conduct three flight tests of their co-developed hypersonic glide body in 2021, an ambitious schedule to initially field the weapon in fiscal 2023, according to Lt. Gen. Neil Thurgood, who oversees the Army’s rapid development of hypersonic, directed-energy and space capabilities.

In March 2020, the Army and Navy had a successful first flight test of their Common-Hypersonic Glide Body, which was launched and flew at hypersonic speed to a designated impact point. That shot was able to hit within 6 inches of the target.

The Defense Department is developing the body that will serve as the base of the United States’ offensive hypersonic missile. The test marked a significant step forward in accomplishing that mission amid mounting criticism that the U.S. is behind China and Russia in hypersonic weapons development.

The Russian Zircon hypersonic cruise missile is launched from the Admiral Groshkov frigate on Oct. 7, 2020, in the White Sea.

The C-HGB will be made up of the weapon’s warhead, guidance system, cabling and thermal protection shield. Each service will use the body as the base while developing individual weapon systems such as launchers capable of firing the weapons from land or sea.

“I just have to tell you that the flight test program is very aggressive,” Thurgood told Defense News in August 2020. “And we need to be aggressive in order to keep on pace and really be competitive with our near-peer competitors, namely Russia and China.”

As the Army gets closer to its fielding goal for the Block I version in FY23, every flight test must meet defined objectives. “We do it for distance, we do it for speed, we do it for accuracy and we do it for lethality,” Thurgood said.

Moving forward, the services will have to “dramatically” accelerate the pace of the program, he added, meaning a flight test should take place mid-2021, and another two later in the year.

“Next year, our intent is to do several flight tests versus where we basically have been done or have completed the flight test, kind of, once every three years,” he said.

But while hypersonic weapons “are useful in part because they are difficult to track,” the report stated, “this complicates efforts to flight test them.”

Flight test programs require a sensor architecture that is able to track the entire flight of a hypersonic missile. Pentagon officials told the GAO that “at present, such flight tests can only be conducted over open ocean,” which means sensors must be on boats that could take weeks to reach destinations far out at sea.

Additionally the ranges and test assets are in high demand, not just for hypersonic weapons development, but for other high-priority programs, the GAO report added, including testing of missile defense systems and intercontinental ballistic missiles.

The DoD has been working over the last several years to mitigate the issues, the watchdog noted, and has pointed to future plans to alleviate schedule challenges for wind tunnel and flight test facilities.

The Test Resource Management Center oversees much of the physical tests and evaluation. The Pentagon told the GAO that TRMC and the DoD’s principal director for hypersonics set up a system for managing programs’ access to test facilities if there are schedule conflicts, the report noted. In June 2018, the Pentagon, the Missile Defense Agency and the armed services signed an agreement to prioritize flight tests for the prototype of the C-HGB.

The Pentagon is also expanding its wind tunnel and open-air flight test infrastructure, according to the report. TRMC has directed “several hundred million dollars in recent years” toward refurbishing and expanding ground and flight test facilities as well as new land and sea ranges to alleviate pressure on existing flight-test corridors.

There are also drone-mounted aerial sensors in development that could take some of the burden off ship-based sensors.

And the DoD is trying to establish international partnerships that could include additional test facilities for hypersonic capabilities, according to the report.

The GAO also said the Pentagon should use data garnered from ground tests in order to meet fielding schedules, but that would require a ramp up in wind tunnel testing at a time where demand for such capabilities is growing, and not just for hypersonic testing.

“If programs cannot get sufficient time in the correct tunnels, they may be forced to either wait or find other less ideal means to complete their testing,” the GAO wrote. “These options include conducting more flight testing, adopting more conservative designs, or making expanded use of computer models.”

Every wind tunnel facility that can conduct hypersonic testing is booked a year or more in advance, the GAO stated.

Wind tunnel test sites are also aging, according to the report. There are 26 government and private U.S. wind tunnel facilities capable of conducting hypersonic testing. A total of 14 of those were constructed prior to 1970.

The DoD agreed that investments to maintain and refurbish wind tunnel facilities “are necessary.”

Jen Judson is an award-winning journalist covering land warfare for Defense News. She has also worked for Politico and Inside Defense. She holds a Master of Science degree in journalism from Boston University and a Bachelor of Arts degree from Kenyon College.

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