While an ICBM warhead follows a predictable path as it descends through the atmosphere, a boost-glide vehicle can maneuver, making it nearly impossible to stop. Credit: Handout.

Once the rockets are up, who cares where they come down? That’s not my department!
— Wernher von Braun

Russian President Vladimir Putin, who doesn’t mince words, boasted that it was unstoppable.

He was speaking, of course, about the coming out party for the lethal Avangard hypersonic missile.

Putin spoke with extra pleasure, no doubt, knowing full well that the US doesn’t have such a boost-glide weapon. Not yet, anyway.

The Avangard is lofted by a giant RS-28 Sarmat ICBM, and then glides down to its target at Mach 20.

Perhaps the only good news, is that US intelligence believes that Moscow will produce only a very limited number of Avangards.

These sources say it is difficult for the Kremlin to find a supplier for the carbon fiber components needed to withstand the extreme temperatures of hypersonic flight.

Is it unstoppable? And does the Russian bear have a distinct advantage in nuclear weaponry?

The US Defense Advanced Research Projects Agency (DARPA), the Pentagon’s pet research group, wants an interceptor that can stop weapons that are hypersonic (travel faster than Mach 5), The National Interest reported.

They have even given it a cool technical name: “counter-hypersonics.”

We might call it a wing and prayer — stopping nuclear warheads coming down on our heads at 20 times the speed of sound, can’t be easy.

Meanwhile, both China and the US are also developing boost-glide vehicles.

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 has thus begun soliciting proposals for Glide Breaker.

And it wants this technology in a hurry. A big hurry.

Aerojet Rocketdyne will develop “enabling technologies” for Glide Breaker under an announced contract worth up to US$19.6 million, the report said. 

Developing technologies that can knock incoming missiles or other fast-moving vehicles out of the sky is a priority for militaries around the world. 

Meanwhile, the Missile Defense Agency (MDA) — the Pentagon organization charged with stopping ballistic missiles — also has its program to develop defenses against hypersonic weapons.

Aerojet Rocketdyne is developing “enabling technologies” for the Glide Breaker interceptor under an announced contract worth up to US$19.6 million. Credit: Handout.

According to The War Zone, the MDA’s current concept for a Regional Hypersonic Missile Defense system combines Aegis Combat System-equipped surface vessels with both space-based and ground-based sensor systems, and ties them together with various integrated fire control and sensor fusion networks.

The Glide Phase Interceptor (a still-in-development weapon aimed at defeating hypersonic threats in the glide phase of their trajectories), along with the capable Standard Missile 6 (SM-6), a multi-purpose weapon that has the ability to engage ballistic missiles in the terminal stage of their flight, would then be used to prosecute the incoming hypersonic threat.

All that considered, there’s a reason for the urgency.

Hypersonic weapons may be able to penetrate US missile defenses or streak past the defenses of aircraft carriers. Even more worrisome, they might be armed with conventional warheads to destroy targets — 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 — the understatement of the century.

If shooting down ballistic missiles is hard, then boost-glide vehicles, also known as hypersonic glide vehicles (HGVs), is even harder, National Interest reported.

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 early warning radars designed to track ballistic missiles.

For another, while an ICBM warhead follows a predictable (and Mach 23) path as it descends through the atmosphere, a boost-glide vehicle can maneuver.

Experts liken it to “hitting a bullet with a bullet.”

Now just imagine if the bullet were taking evasive action.

James Acton, an arms control expert at the Carnegie Endowment for International Peace, argues that despite their speed, HGVs 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 designed to protect a small area — a base, for example, or a petroleum refinery.

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

DARPA may have briefly shown its poker hand in a July, 2018 notice, stating 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 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% of bullets fired at it — but the attacker can’t be sure of whether a particular bullet hit its target.

That’s been the whole basis of nuclear deterrence since the early days of the Cold War. 

In other words, go ahead, Mr. Putin. Do your worst in a first strike — but don’t be too sure that a devastating retaliation isn’t coming your way.

The Achilles heel of ballistic missile defense has been that it’s cheaper for an attacker to build an overwhelming mass of missiles than it is for the defender to build interceptors.

But that won’t stop the Pentagon and Congress from throwing major defense dollars at anything that involves hypersonics.

Weapons like Russia’s Avangard present a missile gap, that looms large in the minds of US defense planners.

According to the Federation of American Scientists, the Pentagon’s FY2021 budget request for all hypersonic-related research is US$3.2 billion — up from US$2.6 billion in
the FY2020 request—including US$206.8 million for hypersonic defense programs.

At present, the Department of Defense (DOD) has not established any programs of record for hypersonic weapons, suggesting that it may not have approved either requirements for the systems or long-term funding plans.

As Assistant Director for Hypersonics (Office of the Under Secretary of Defense for Research and Engineering) Mike White has stated, DOD has not yet made a decision to acquire hypersonic weapons and is instead developing prototypes to assist in
the evaluation of potential weapon system concepts and mission sets.

According to the New York Times Magazine, the development of hypersonics is moving so quickly, that it threatens to outpace any real discussion about the potential perils of such weapons, including how they may disrupt efforts to avoid accidental conflict, especially during crises.

There are currently no international agreements on how or when hypersonic missiles can be used, nor are there any plans between any countries to start those discussions.

Instead, the rush to possess weapons of incredible speed and maneuverability has pushed the United States into a new arms race with Russia and China — one that could, some experts worry, upend existing norms of deterrence and renew Cold War-era tensions.

Sources: The National Interest, Space.com, Federation of American Scientists, The War Zone, Top War, New York Times Magazine