Hypersonic weapons demand longer-range radars and space-based sensors for detection
A blisteringly fast threat that requires longer-range radars and space-based sensors looms on the horizon in the form of hypersonic vehicles and missiles.
Busting out of Earth’s lower orbit requires hypersonic vehicles to reach speeds in excess of Mach 5 (about 3,836 mph) and, at hypersonic speeds, they take an absolute beating from the air particles and gases that flow around and interact with their surfaces—particularly on their leading edge. This generates extreme heat and shock waves, which disturb the flow’s equilibrium, and is a materials and design nightmare.
But it hasn’t stopped Russia from reportedly developing a few hypersonic vehicles, one of which is claimed to capable of reaching Mach 20 (about 15,345 mph), while the U.S. has been quietly working on hypersonics for decades and now appears to be keeping a really tight lid on its capabilities; either that or it is perhaps actually still working on it. China also reportedly has hypersonic weapon capabilities.
In 2018, the U.S. Air Force awarded Lockheed Martin contracts to develop a Hypersonic Conventional Strike Weapon (HCSW), an air-launched missile that will travel more than five times faster than the speed of sound, and an Air Launched Rapid Response Weapon (ARRW). The U.S. Navy is also pursuing submarine-launched hypersonic weapons.
Many other defense contractors – including Raytheon and Northrop Grumman – have been exploring or working on hypersonic vehicles or weapons for years.
No countermeasures for hypersonic weapons exist yet
The U.S. could develop a workable defensive capability against hypersonic weapons by the mid 2020s, said Michael Griffin, undersecretary of defense for research and engineering, at a National Defense Industrial Association event in December 2018. He explained that this requires developing “longer-range radars and new space-based sensors” that can track and target adversaries’ weapons – in the event that an attack is launched.
One huge problem is that today’s radar systems aren’t capable of seeing far enough out to detect hypersonic weapons. Radar systems will need to be developed to see thousands of kilometers (rather than hundreds) out to provide an advanced warning about incoming hypersonic threats.
Hypersonic weapons are being pursued – despite the extreme materials and engineering challenges involved – because their speed, altitude, and maneuverability may defeat most missile defense systems, according to a recent U.S. General Accounting Office (GAO) report. These weapons may also be used to improve long-range conventional and nuclear strike capabilities. The really bad news: There are no existing countermeasures.
DARPA seeks thermal solutions for hypersonic vehicles
The Pentagon’s Defense Advanced Research Projects Agency (DARPA) is actively seeking designs for cooling vehicles’ superhot leading edges that rip through the air at more than five times the speed of sound. Developing structures that can withstand furnace-like temperatures at such high speeds is an enormous technical challenge, primarily for leading edges that are subjected to the brunt of the heat.
To address this thermal challenge, DARPA recently announced a Materials Architectures and Characterization for Hypersonics (MACH) program. The MACH program aims to develop and demonstrate new design and materials solutions for sharp, shape-stable, cooled leading edges for hypersonic vehicles. (Figure 1.)
For decades, researchers have “studied cooling the hot leading edges of hypersonic vehicles but haven’t been able to demonstrate practical concepts in flight,” says Bill Carter, program manager in DARPA’s Defense Sciences Office.
The key, Carter adds, “is developing scalable materials architectures that enable mass transport to spread and reject heat. In recent years, we’ve seen advances in thermal engineering and manufacturing that could enable the design and fabrication of very complex architectures not possible in the past. If successful, we could see a breakthrough in mitigating aerothermal effects at the leading edge that would enhance hypersonic performance.”
DARPA’s MACH program encompasses two technical areas. The first area aims to develop and mature a fully integrated passive thermal management system to cool leading edges based on scalable net-shape manufacturing and advanced thermal design. The second area focuses on next-generation hypersonic materials research, applying modern high-fidelity computation capabilities to develop new passive and active thermal management concepts, coatings, and materials for future cooled hypersonic leading-edge applications. (See go.usa.gov/Dom)
The MACH program is seeking expertise in thermal engineering and design, advanced computational materials development, architected materials design, fabrication and testing (including net-shape fabrication of high-temperature metals, ceramics, and composites), hypersonic leading-edge design and performance, and advanced thermal-protection systems.