3/23/2022
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The U.S. recently confirmed that the Russian Ministry of Defence fired a hypersonic ballistic missile to destroy an underground arms depot in western Ukraine. This event marks Russia’s first use of the Kinzhal ballistic missile in this war and the first known use of a hypersonic missile in combat. Mechanical science and engineering professor Kelly Stephani spoke with News Bureau physical sciences editor Lois Yoksoulian about the significance of this technology.
What does hypersonic mean?
Hypersonic refers to the speed at which an object, in this case a missile, travels through the atmosphere at or greater than five times the speed of sound. This ratio of the missile speed relative to the speed of sound in air is characterized by the Mach number, and so we classify high-speed vehicles based on their Mach number. Once a vehicle reaches a speed of approximately Mach 5, the energy of the vehicle is so large that it dramatically heats the air around it, breaking molecules apart and ionizing the gas, forming a weakly ionized plasma. This plasma formation has significant implications for understanding vehicle aerodynamic response, extreme heating and thermal protection, communications, and guidance and control, to name a few.
How are hypersonic missiles different than most conventional missiles?
First, these missiles travel at immense speeds that significantly shorten or eliminate response times for defense. Second, these missiles can maneuver and follow trajectories different from a standard intercontinental ballistic missile, or ICBM. They can fly below the line-of-flight detection capability of ground-based defense systems, making them more challenging or impossible to intercept from the ground-based defense systems. They are also dimmer and more difficult to detect from above, making the prediction of their final intended target more difficult.
Finally, it is important to recognize the political posture that the U.S. has taken on hypersonic technologies as a conventional weapon, while other countries have made these platforms nuclear-capable. Russia’s Kinzhal missile is an aeroballistic missile – with a quasi-ballistic hypersonic trajectory. It is the first claimed use of a hypersonic weapon in a theater of war. One can argue whether the deployment of this missile is a game-changer in the attack against Ukraine, but it sends a clear signal of escalation and remains indefensible.
What countries have this technology?
China and Russia have fielded weapons capable of hypersonic speed, and now Russia is the first to deploy this weapon in the battle space. Other countries, including the U.S., Australia, France, Germany, India and North Korea, have also tested or are actively developing hypersonic capabilities.
What is the status of hypersonic technology in the U.S.?
The U.S. has been developing, building and testing hypersonic systems for decades. In fact, every spacecraft that returns from orbit or space enters the atmosphere at hypersonic speeds. The NASA X-43 experimental unmanned hypersonic aircraft flew at Mach 7 and Mach 10 in the early 2000s, and the Boeing X-51 Waverider demonstrated hypersonic flight again in 2010. From there, honestly, we took our foot off the gas. Other countries realized the strategic significance of this technology through sustained investment, development of test and manufacturing infrastructure, and workforce development and have taken the lead. It is imperative that we not only catch up, but also leap ahead in capability.
The U.S. is pursuing both offensive and defensive capabilities. Both are important for deterrence as well as for developing technological superiority. Hypersonic platforms typically fall under one of two categories: hypersonic boost-glide vehicles or hypersonic air-breathing cruise missiles. Traditional intercontinental ballistic missiles also travel at hypersonic speeds but follow a predictable, parabolic trajectory, making them easier to intercept. Boost-glide and cruise missiles travel at hypersonic speeds, with the advantage of maneuverability in midcourse/glide and terminal phases, and a low-altitude trajectory that makes them challenging to see and practically impossible to intercept. The armed services are moving rapidly to acquire these capabilities, with the earliest delivery of these platforms in late 2022, more likely 2023 and beyond.
What are the implications for missile defense systems?
Defense against hypersonic missiles creates a new paradigm for defense technologies, but it can be added to a broad spectrum of modern missile defense capabilities. As stated previously, these missiles can fly below the line-of-flight detection capability of ground-based defense systems. By the time they are detected, their speed makes them practically indefensible based on our current defense systems.
We need to ask how legacy ballistic missile defense systems can be leveraged or transformed for defense against hypersonic systems. Fielding of defense systems requires a layered, integrated approach. The Missile Defense Agency leads the Glide Phase Interceptor program, which provides hypersonic intercept capability. The Defense Advanced Research Projects Agency leads Glide Breaker, which provides long-range hypersonic intercept abilities. The Missile Defense Agency and the Department of Defense are also looking at directed-energy and laser-based defense strategies, but these are longer-term goals.
How is The University of Illinois Urbana-Champaign contributing to hypersonic technology research?
The University of Illinois is leading this national effort with support from the Department of Defense, NASA, national laboratories and industry partners. The Center for Hypersonics and Entry Systems Studies, launched in 2019, fosters collaborative and interdisciplinary research and education in fundamental sciences that support the advancement of hypersonics and entry systems technologies. We have opened a new national test facility, developed by CHESS in coordination with DOD, staffed by faculty who serve in leadership and advisory roles within the University Consortium for Applied Hypersonics and support congressional studies and recommendations through the National Academies of Sciences, Engineering, and Medicine.
Editor's note: To contact Kelly Stephani, email ksteph@illinois.edu.