A Progress Report on Hypersonics
.By Bill Sweetman
The U.S. and Australia have been collaborating on technology for hypersonic weapons since 2007, but you might be forgiven for not knowing that. Until 2014, when China was seen to be testing the DF-17 boost-glide weapon, the standard line was that ‘hypersonics are the weapon of the future—and they always will be.’ The Hypersonic International Flight Research Experimentation (HIFiRE) program of Australia and the U.S. was seen as a lab project.
Its successor, the Southern Cross Integrated Flight Research Experiment (SCIFiRE) program, is linked to a funded weapon: the U.S. Air Force’s Hypersonic Attack Cruise Missile (HACM), to be carried by U.S. Air Force F-15Es and, possibly, by Royal Australian Air Force F/A-18F Super Hornets.
HACM development won’t be complete until 2029, if it stays on schedule, and its costs are undefined. For now, U.S. hypersonic weapons are confined to a different class of vehicle, similar to the systems that China is deploying. But due to geography, a technology that is useful to China may be less so to the Pacific alliance.
‘Hypersonic’ has a clear definition: Mach 5 and above. As a vehicle approaches five times the speed of sound (5300km/h at altitude), a layer of stagnant air forms at its nose and leading edges and becomes hot and compressed, subjecting the vehicle to much more extreme conditions than are encountered even at Mach 4.
Two hypersonic vehicle types are being developed: hypersonic glide vehicles (HGVs), launched by rockets but using aerodynamic lift to maneuver and extend their range; and cruise vehicles powered by supersonic combustion ramjets (scramjets), the only airbreathing engines that will function at such speeds. They fly as low as 30,000 meters, far lower than ballistic missiles, and maneuver at will. So the defenses get less warning and cannot predict their track as easily.
https://www.realcleardefense.com/articles/2024/09/09/a_progress_report_on_hypersonics_1056867.html
