Here's What You Need to Remember: The U.S. Army and U.S. Navy seem to be pushing forwards with their C-HGB-based hypersonic weapons though, under the names Long Range Hypersonic Weapon and Intermediate Range Prompt Conventional Strike, respectively. The C-HGB design is considered to be the “safe” hypersonic development project, as based on earlier hypersonic research.
The Department of Defense Fiscal Year 2021 budget request resulted in a lot of reshuffling among next-generation procurement projects. One of the highest profile cancellations is the US Air Force’s cancellation of the Hypersonic Conventional Strike Weapon (HCSW). The HCSW was one of the “many” hypersonic weapons Trump referred to in his January statement following the Iranian counterstrike. However, in the context of overall military procurement, the HCSW cancellation makes sense. But it also suggests that perhaps hypersonics are not as big of a deal as many media sources have made them out to be.
The HCSW was one of two hypersonic weapons programs that were ready to enter service in the near term, the other being the Air-Launched Rapid Response Weapon, or ARRW. The two programs differ significantly: in shape, maturity, and hypersonic characteristics. The HCSW is the U.S. Air Force’s portion of a shared hypersonic “glide vehicle,” called the Common Hypersonic Glide Body (C-HGB). As the Air Force primarily employs their weapons from the air, the HCSW was a rocket motor attached to the C-HGB, meant to be air launched.
The U.S. Army and U.S. Navy seem to be pushing forwards with their C-HGB-based hypersonic weapons though, under the names Long Range Hypersonic Weapon and Intermediate Range Prompt Conventional Strike, respectively. The C-HGB design is considered to be the “safe” hypersonic development project, as based on earlier hypersonic research. Notably, AviationWeek claims that the design of the HCSW was based in the 1970s-era Sandia Winged Energetic Re-entry Vehicle Experiment (SWERVE). Sandia’s official press releases about the Army’s hypersonic weapons mention the SWERVE, but don’t delve into whether it is the direct ancestor of the modern C-HGB.
But the U.S. Air Force’s cancellation of HCSW suggests that early, or relatively conventional hypersonic tech doesn’t fit their vision of how hypersonic weapons should perform to be truly useful on the battlefield. While there are no hard numbers as the HCSW was still being refined, most reports suggest that the HCSW would move at slightly more than Mach 5, slow for a hypersonic weapon, and only half the speed of the Kh-47 “Kinzhal,” Russia’s air-delivered hypersonic missile.
The project that remains, ARRW, is a far more advanced design, featuring a “wedge” rather than a “cone” design. The ARRW is said to be designed to travel at speeds of up to Mach 20. If production or testing variants manage to reach those speeds, they could allow the Air Force to “leapfrog” the hypersonic tech level of current Russian missiles. As the ARRW is said to be on track for 2022 in-service date, the calculus seems clear: waiting two years for a true next-generation missile will probably be worth it and consolidating funding on the more advanced design will pay off. Of course, this assumes ARRW testing does off without a hitch. If delays are encountered, as they have been in the past, the U.S. Air Force may regret their decision to can the safer project.
Charlie Gao studied Political and Computer Science at Grinnell College and is a frequent commentator on defense and national security issues.