U.S. Hypersonic Testing Shows Mixed Results In Pivotal Year

Rising from a very low baseline prior to 2020, U.S. testing on prototypes of hypersonic weapons has increased steadily as the Pentagon prepares to field the first two weaponized hypersonic glide vehicles this year—yet the testing remains far short of expectations amid reshuffled acquisition plans and setbacks.

The Army still intends to deploy the first battery of the Long-Range Hypersonic Weapon (LRHW) this year, although a successful test of the combined Common Hypersonic Glide Body (CHGB) and two-stage booster has yet to occur, more than 10 months after the first attempt.

• Hypersonic testing pace starts slow
• Pentagon hints at several secret tests

The Air Force, meanwhile, has canceled plans to acquire the Lockheed Martin AGM-183A Air-Launched Rapid Response Weapon (ARRW) amid mixed test results, although four residual missiles from the operational prototyping program can still be used to declare early operational capability of the medium-range hypersonic glide vehicle (HGV) by year-end.

Air Force officials previously canceled plans to adapt the Army-Navy CHGB into the air-launched Hypersonic Conventional Strike Weapon (HCSW). Instead, the service aims to field the scramjet-powered operational prototype—the Raytheon/Northrop Grumman Hypersonic Attack Cruise Missile (HACM)—in fiscal 2027.

With the bulk of the U.S. hypersonic weapons portfolio expected to be split between the ground-launched, intermediate-range CHGB in the near term and the air-launched, medium-range HACM in the late 2020s, the Defense Department is increasing the pace of testing dramatically with significant investments in infrastructure and the establishment of parallel tracks for high-tempo tests of experimental technology.

The surviving programs emerged from a burst of rapid hypersonic development launched in 2017 as China’s surprise lead on hypersonic weapons became apparent. The People’s Liberation Army Rocket Force has since fielded the medium-range DF-17 and intermediate-range DF-27 HGVs while continuing to test a series of hypersonic cruise missiles. In response, the Pentagon accelerated development of DARPA’s scramjet and HGV development projects, while the Air Force, Army and Navy teamed up to adapt a decades-old HGV program into a multiservice conventional missile.

Since then, the pace of testing has fallen short of expectations, however. In June 2019, Mike White, the Pentagon’s principal director for hypersonics research, development, test and evaluation, said the Defense Department planned to complete 40 hypersonic weapons tests by the end of 2023. As of the end of April, U.S. military officials have publicly announced 14 test attempts on the operational prototypes since White’s prediction, with eight described as successes, one as a partial success and five as failures. At least three of the failed tests were blamed on booster malfunctions, depriving the programs of valuable data on the performance of HGVs at hypersonic speeds.

But the public record may not tell the full story. In response to questions from Aviation Week about the publicly announced test record, White said there have been “significantly” more hypersonic flight tests conducted since 2019.

“For operational security reasons, we cannot disclose the number of hypersonic flight tests and dates and purpose of each,” White said. “Across the department, we have dramatically increased the number of hypersonic flight tests in the past few years compared to the number accomplished over the past several decades.”

Hypersonic flight testing has yielded some breakthroughs. DARPA’s Hypersonic Air-Breathing Weapon Concept (HAWC) program, for example, overcame a series of error-prone captive-carry tests in 2020. During a roughly 15-month period between September 2021 and January 2023, both HAWC competitors—the Lockheed/Aerojet Rocketdyne and Raytheon/Northrop Grumman teams—successfully completed four tests of scramjet-powered cruise missiles at sustained speeds above Mach 5 for more than 300 sec.

These paved the way for the Defense Department’s partnership with the Australian government on the Southern Cross Integrated Flight Research Experiment (SCIFire) program, which seeks to bridge the gap between the HAWC demonstrator and the weaponized HACM with a series of additional flight tests beginning in 2024 on a Royal Australian Air Force Boeing F/A-18F Super Hornet. The next step would be to develop the SCIFire platform into the Raytheon/Northrop HACM prototype by 2027.

Only the Raytheon/Northrop team has been selected to work on the SCIFire and HACM programs so far, but the technology behind the Lockheed/Aerojet team’s successful HAWC demonstrator may not be abandoned.

“While we won’t speak for the government, our understanding is that the [government] has not definitized their plan at the conclusion of the SCIFire/HACM efforts,” a Lockheed spokesperson said. “Lockheed Martin has strong hypersonic credentials and will assess opportunities as they develop.”

Air Force officials also appear open to keeping Lockheed’s HAWC technology progressing.

“The [government] has many other hypersonic efforts outside of the [Air Force] where Lockheed Martin’s demonstration may provide equity,” an Air Force spokesperson says. A possible example is a follow-on project launched by DARPA this year called the More Opportunities with HAWC (Mohawc) program, which includes another round of flight testing starting in fiscal 2024.

The Lockheed’s ARRW technology also may not be settled. Although the program has seen several test failures, including the latest attempt on March 13, the AGM-183 has proven the feasibility of a tactical HGV. The first test of an all-up round of the AGM-183 on Dec. 9 was recorded as a success, marking the first time an HGV with a high lift-to-drag-ratio shape completed a full glide while starting at hypersonic speed.

Despite spending more than $1.18 billion on the ARRW contract with Lockheed through the end of 2022, the Air Force has dropped plans to move the AGM-183A into production even if further tests are successful. A new Air Force leadership team considers the scramjet-powered HACM more cost-effective than the roughly $10 million-per-round AGM-183A.

But DARPA is developing other applications for the underlying technology for ARRW, which emerged from the agency’s Tactical Boost Glide (TBG) program. A subsystem for a sea-launched variant of the TBG technology is scheduled for testing in fiscal 2023, according to DARPA’s budget documents. The Navy, meanwhile, plans to field the first intermediate-range Conventional Prompt Strike missiles in 2025, leveraging the same booster stack and CHGB as the Army’s ground-launched LRHW.

Any new hypersonic variants are expected to benefit from a parallel track of flight testing being established. The Air Force’s Mayhem program is developing an expendable hypersonic test platform using air-breathing propulsion. The Navy’s Multiservice Advanced Capability Hypersonics Test Bed (MACH-TB) is developing an experimental HGV. Finally, the Defense Innovation Unit has selected the Hypersonix scramjet-powered DART AE, the Fenix Space towed launch platform and the Rocket Lab Hypersonic Accelerator Suborbital Test Electron (HASTE) to participate in the Hypersonic and High--Cadence Testing Capabilities (HYCAT) program.

With the Mayhem, MACH-TB and HYCAT vehicles, the Pentagon can clear experimental new technologies for high-speed flight without burdening the few test events available to the operational prototyping programs.

“MACH-TB will provide additional flight-test opportunities that will accelerate our science and technology and capability development activities,” White said.

Within the office of the Secretary of Defense, meanwhile, the Test Resource Management Center (TRMC) is implementing the new SkyRange concept for tracking hypersonic flight tests. Instead of repositioning slow-moving picket ships to relay telemetry and tracking data from HGVs and hypersonic cruise missiles, the TRMC has acquired a mix of Northrop Grumman RQ-4 Global Hawks and General Atomics Aeronautical Systems Inc. MQ-9 Reapers.

Advanced phased-array telemetry antennas have been integrated on the first three TRMC-owned RQ-4s, converting them into the RangeHawk configuration. Five more MQ-9s, known as RangeReapers, will be equipped with pod-mounted sensors, including new variants of the telemetry antennas. The RangeHawks also are slated to receive a High-Altitude Lidar Atmospheric Sensing system, which is in testing aboard a Gulfstream G-IV.

“Beyond MACH-TB, the department, led by the Test Resource Management Center hypersonics [Test and Evaluation] strategy, is making significant investments to increase our flight test throughput,” White said. “Included in these investments are additional long-range flight-test corridors and new range infrastructure enabling more frequent and agile test opportunities.”