DARPA's hypersonic 'Glide Breaker' could blast missile threats out of the sky

An artist's concept of DARPA's Glide Breaker anti-hypersonic-weapon system. (Image credit: DARPA)

Aerojet Rocketdyne is working on technology to help knock high-speed maneuverable vehicles out of the sky, under a new contract from the U.S. Defense Advanced Research Projects Agency (DARPA).

Since 2018, DARPA has been developing a "hypersonic defense interceptor" system called Glide Breaker, which is designed to intercept threatening vehicles moving at hypersonic speeds (meaning, at least five times faster than the speed of sound) in Earth's upper atmosphere. 

Aerojet Rocketdyne will develop "enabling technologies" for Glide Breaker under the newly announced contract, which is worth up to $19.6 million. 

Related: The most dangerous space weapons ever

"Advancing hypersonic technology is a national security imperative," Eileen Drake, Aerojet Rocketdyne CEO and president, said in a statement. "Our team is proud to apply our decades of experience developing hypersonic and missile propulsion technologies to the Glide Breaker program."

Based on the images available on DARPA's Glide Breaker program page, it appears that the new tech will involve launching missiles to hit hypersonic vehicles in flight. No other information about the program, however, is available on the web page.

Aerojet Rocketdyne pointed to other contracts it has with DARPA to show its expertise in hypersonic flight, using either solid-fuel propulsion or engines that are "air-breathing" (typically, gas turbine engines). 

An artist's concept of DARPA's Glide Breaker anti-hypersonic-weapon system.

An artist's concept of DARPA's Glide Breaker anti-hypersonic-weapon system.  (Image credit: DARPA)

Both of these technologies were used in the X-51A WaveRider, a vehicle developed by DARPA, the U.S. Air Force and NASA that made the longest-ever hypersonic flight for a vehicle of its kind in May 2013. Aerojet Rocketdyne also did propulsion system test firings for a future ground-launched hypersonic missile, under DARPA's Operational Fires program.

Developing technologies that can knock incoming missiles or other fast-moving vehicles out of the sky is a priority for militaries around the world. The U.S. has worked on numerous such ideas over the years, some of which never got off the ground. 

One of the most famous mothballed concepts was the Strategic Defense Initiative (SDI), a complex, space-based system championed by President Ronald Reagan; opponents derisively dubbed it "Star Wars."   

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Elizabeth Howell
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Elizabeth Howell is a regular contributor to Live Science and Space.com, along with several other science publications. She is one of a handful of Canadian reporters who specializes in space reporting. Elizabeth has a Bachelor of Journalism, Science Concentration at Carleton University (Canada) and an M.Sc. Space Studies (distance) at the University of North Dakota. Elizabeth became a full-time freelancer after earning her M.Sc. in 2012. She reported on three space shuttle launches in person and once spent two weeks in an isolated Utah facility pretending to be a Martian.
  • Hartmann352
    DARPA seeks to "develop and demonstrate a technology that is critical for enabling an advanced interceptor capable of engaging maneuvering hypersonic threats in the upper atmosphere." And it wants this technology in a hurry: Glide Breaker should be tested this year or in 2022. Meanwhile, the Missile Defense Agency -- the Pentagon organization charged with stopping ballistic missiles -- also has its program to develop defenses against hypersonic weapons**.

    There's a reason for the rush. Hypersonic weapons may be able to penetrate U.S. missile defenses or streak past the point missile defenses of U.S. aircraft carriers like their Rolling Airframe Missiles (RAM's) or the Phalanx Close-In Weapons System (CIWS). Even more worrisome, they might be armed with conventional warheads to destroy point targets with kinetic warheads -- notably ICBMs in hardened silos -- once thought invulnerable to anything but nuclear weapons.

    DARPA's solicitation is light on unclassified details, though it says it wants "innovative solutions" to stop boost-glide vehicles. If shooting down ballistic missiles is hard, akin to hitting a bullet with a bullet, then boost-glide vehicles, also known as hypersonic glide vehicles (HGVs), is even harder. Imagine if that target bullet was taking evasive action or is exhibiting non-ballistic motion.

    For starters, the gliders don't traverse outer space like an ICBM, but instead soar through the thin upper atmosphere, where they can achieve extremely high speeds while flying too low to be easily detected by ballistic missile early warning radars designed to track ballistic missiles arcing through outer space. For another, while an ICBM warhead follows a predictable (and Mach 23) path as it descends through the atmosphere, a boost-glide vehicle -- like a hobby glider -- can maneuver, which make it much harder for an interceptor to strike it, even with shrapnel from a nearby explosion.

    Or put another way, counter-hypersonics encounter all the difficulties of ballistic missile defense against ICBMs, and then some. "The most obvious challenge is the maneuverability of HGVs, which makes it very difficult to maintain track on the vehicle and plan an intercept course using our current capabilities," George Nacouzi, an engineer at the RAND* Corp. think tank, told the National Interest . "Flight altitude is also challenging for our current systems. The HGV may fly too high for many endo-atmospheric interceptors and too low to be detected and tracked early by long range ballistic missile early warning radars."

    Nacouzi believes there are ways to shoot down HGVs, "but they would involve using a nearly ubiquitous surveillance and tracking system accompanied by strategically positioned very high performance interceptors or, possibly in the future, directed energy weapons." The U.S. is developing these solutions for intercepting ballistic missiles, but they all have drawbacks: directed energy weapons such as lasers can be affected by weather, while having armed drones or aircraft constantly hovering over North Korean missile sites could trigger a war.

    James Acton, an arms control expert at the Carnegie Endowment for International Peace, argues that despite their speed, hypersonic weapons can be destroyed by some ballistic missile defense systems such as the Terminal High Altitude Area Defense (THAAD) system. The problem is that THAAD is a point-defense weapon designed to protect a small area: covering the entire United States with THAAD-like defenses would be prohibitively expensive.

    So, given current technology, a leak-proof shield that can reliably stop a massed salvo of hypersonic glide vehicles seems doomed to failure.

    But maybe the value of counter-hypersonics isn't shooting down these lethal gliders?

    DARPA may have captured the real value of counter-hypersonic defenses in a notice from July 2018 Proposer's Day, where industry had a chance to learn about the project. The notice stated that "a key figure of merit is deterrence: the ability to create large uncertainty for the adversary’s projected probability of mission success and effective raid size."

    Note the significance of that phrasing: anti-hypersonic defense is successful not by necessarily destroying every incoming boost-glide vehicle, but by making a potential adversary uncertain of which hypersonic vehicles will get through. It's the equivalent of body armor that will stop only 50 percent of bullets fired at it -- but the attacker can't be sure of whether a particular bullet aimed at a vital spot will hit its target.

    That's been the whole basis of nuclear deterrence since the early days of the Cold War. Even if the first strike could destroy much of the enemy's nuclear missiles and bombers, an attacker couldn't be sure that enough nukes would be left over to mount a devastating retaliation because of the third leg of the triad, nuclear powered ballistic missile armed submarines, whose locations would be presumably unknown. This falls under the accepted doctrine of Mutually Assured Destruction (MAD), which was the guiding principle of our nuclear triad during the Cold War and which still operates today.

    However, the Achilles heel of ballistic missile defense has been that it's cheaper for an attacker to build an overwhelming mass of missiles and warheads than it is for the defender to build interceptors to stop them all. It remains to be seen whether the economics of hypersonic missile defense will be the same.

    * The RAND (Research and Development) Corporation, 1776 Main Street, Santa Monica, CA 90401: The difference between RAND today and the organization created in 1948 is substantial and dramatic. RAND started with one client—the U.S. Air Force—and over the past seven decades has generated ideas and solutions for thousands of clients and other stakeholders around the world.

    The mix of studies, singular accomplishments, and streams of research and analysis included in this timeline exemplifies the range and originality of RAND research. The selections are by no means the only ways and not necessarily the most important ways that RAND has made a difference. But they reflect the breadth of an ever-diversified organization and reveal a common motif: our ability to have a positive effect on the world by applying rigorous and objective analysis to challenging problems. That aspiration has guided RAND ever since it was established.

    See: https://www.rand.org/about.html
    ** Having completed a wide-ranging review of options, the U.S. Missile Defense Agency (MDA) is moving forward with a plan to expand the rebranded “Missile Defense System” with an accelerated effort to field a new Glide Phase Interceptor (GPI) against maneuvering hypersonic missiles in the mid- to late-2020s.

    The changes, which are disclosed in a Jan. 28, 2021, acquisition notice, officially broaden the scope of the previously named “Ballistic Missile Defense System” to include the threat of rocket-boosted, hypersonic glide vehicles (HGVs) that can maneuver within the atmosphere.

    The acquisition notice formally cancels a Request for Prototype Proposal process opened early last year for a Regional Glide Phase Weapon System (RGPWS), which was intended to be fielded in the early 2030s.

    Following “an assessment and review of requirements at all levels of the Missile Defense System,” the notice says, MDA now intends to accelerate the plan to deploy a new sea-based GPI by the end of this decade. MDA will formally launch the Glide Phase Interceptor (GPI) acquisition program in a follow-on acquisition notice, which is scheduled for release by the end of March.

    Thus we can visualize the problems inherent in the design and production of the Glide-Breaker system and even the near twin Glide Phase Interceptor system, from their extreme complications due to their cost of development, production, testing, installation and eventual usage. And note that no mention was made by DARPA of the use of hypersonic decoys by a peer aggressor, which would add a substantial number of additional problems to the intercept schemata such as altered flight characteristics and unique infrared signatures, to name two.

    I have no doubt that American engineering and industry could overcome these obstacles, however, with the change of administrations where the overarching concern appears to be on an internal politics and in no way centered on avant-garde military weaponry, a la Ronald Reagan, at the fringes of physics, photonics and AI, in a world where our three primary foes (Russia, China and North Korea) are plunging headlong ahead into these areas, who can say how our future defense posture in the endo-atmosphere will shake out.