Hypersonic Glide Vehicles: What are They Good for?

Now with a minor update.

News of the initial deployment of Russia’s first hypersonic glide vehicle (HGV), called Avangard, comes just a few months after China exhibited its first such weapon, the DF-17, in a parade. This is as a good an occasion as any to ask: what are HGVs good for? Why does Russia want them? And why, for that matter, does America want them? Let’s put China to one side for now.

Russian weapons vs. American BMD

For Russia, at least, the answer offered by President Putin is clear enough: defeating American missile defenses. “This is a weapon of the future that can penetrate both existing and any future missile defense systems.”

To get the flavor of the idea, it helps to revisit the larger modernization picture that Putin laid out in his March 1, 2018 address.

The American withdrawal from the ABM treaty in 2002, Putin explained, was motivated by the belief that Russia had become so weak that it could simply be disregarded, allowing the U.S. to pursue “ultimate unilateral military advantage in order to dictate the terms in every sphere in the future.”

Since then, furthermore, the US has deployed a growing number of BMD systems around the world. The consequences? “If we do not do something, eventually this will result in the complete devaluation of Russia’s nuclear potential. Meaning that all of our missiles could simply be intercepted.”

Therefore, Putin explained, Russia has been “working intensively” on new strategic weapons.

First, Russia continues to refine countermeasures (“highly effective but modestly priced systems to overcome missile defence”) for all of its currently deployed ICBMs.

Second, Russia has developed the new Sarmat heavy ICBM, capable of carrying a large number of warheads, apparently with maneuvering capabilities, to evade BMD. According to Putin, Sarmat can also attack over the South Pole, making it a revival of an old concept: fractional orbital bombardment systems (FOBS). The US currently deploys no south-facing early warning radars, and has no defensive assets in place to address threats from this direction.

Third is a nuclear-powered cruise missile of effectively unlimited range, which the world now knows as Burevestnik (“storm petrel”). Putin underscored its ability to maneuver around radars and defended areas.

Fourth is a nuclear-powered intercontinental torpedo, now named Poseidon. Missile defenses are clearly irrelevant to an undersea threat.

Fifth is the Kinzhal (“dagger”) air-launched ballistic missile (ALBM), a maneuvering, nuclear-capable weapon with a reported range of over 2,000 km. Its characteristics suggest it is mostly meant to overcome BMD in Europe or elsewhere on Russia’s periphery. (FAS has recently published an informative paper on Kinzhal and other ALBMs.)

Sixth is the Avangard (“vanguard”) intercontinental-range HGV.

Seventh is a mobile laser, whose purposes Putin did not explain. Now known as Peresvet, its distinctive vehicles have been deployed near mobile ICBM bases, suggesting that it serves to protect ICBM launch vehicles from observation. Some observers suspect that it has an air-defense mission, perhaps against drones; others have seen it as designed to dazzle electro-optical sensors in low-earth orbit.

Kinzhal and Peresvet differ from the rest—Kinzhal because it’s regional in character, and Peresvet because it’s not a nuclear delivery system at all, but rather serves to shield ICBMs from surveillance. The rest, according to Putin—the Sarmat FOBS-capable heavy ICBM, the Burevestnik nuclear-powered cruise missile, the Avangard HGV, and the Poseidon nuclear-powered torpedo—are designed to defeat or circumvent ICBM-class BMD systems.

Why so many different systems? What reasoning might connect these various efforts? One possibility is a “portfolio” explanation. By this reasoning, these programs represent the competing products of different military-industrial establishments, allowed to proceed in tandem in case some of them fail to reach maturity. Today, the risk of failure appears particularly great in the case of the Burevestnik, which apparently killed technical personnel and spewed radioactivity during a failed recovery effort at sea earlier this year.  

Another possibility is a strategy of mutual reinforcement. American strategists often talk about advantages of the nuclear triad, with each “leg” presenting an enemy with a different set of challenges. Similar thinking may apply here: deploying half a dozen systems with sufficiently distinctive delivery modes would require half a dozen different defensive architectures to counteract them, complementing each other and strengthening confidence in the ability to retaliate.

Update. Andrey Baklitskiy adds an “educated guess”: that the March 1, 2018 unveiling was an attempt to induce the U.S. to negotiate on strategic arms. If that’s so, it clearly didn’t work. But it would help to explain why the Kremlin has been unwilling to part with a troubled program like Burevestnik; from a bargaining perspective, one doesn’t give up something in exchange for nothing.

Avangard could certainly be viewed in this light [i.e., in terms of the strategy of mutual reinforcement]. By gliding through the atmosphere rather than through space, it would be immune to “midcourse phase” interceptors like GMD. On the other hand, notwithstanding Putin’s rhetorical flourishes, a glider isn’t utterly immune to intercept. Despite its ability to maneuver, its passage through the atmosphere also makes it relatively slow, compared to an ICBM, by the time it reaches a target at intercontinental distances. It might be possible for a highly capable “terminal phase” interceptor, such as the SM-2 missile associated with the Aegis system, to attempt an intercept. But this observation only holds as long as the defensive assets are in the right place at the right time. The simultaneous deployment of ICBMs and HGVs would require a defender to deploy both architectures to cover the same variety of potential targets—an especially daunting prospect if one wanted to shield an entire continent.

Notwithstanding either of these rationales, the Russian approach smacks of overkill. Putin’s own commentary introducing this new family of wonder weapons started off with “highly effective but modestly priced systems to overcome missile defence.” Those countermeasures already in place, to say nothing of the sheer numbers of deployed warheads, seem more than sufficient to deal with present or future defenses. Perhaps all this excess is meant to convince the U.S. of the futility of the BMD enterprise, and induce a more cooperative line of thought in Washington. Or perhaps it’s all just an elaborate jobs program.

News of the Avangard deployment comes alongside an unconditional Russian offer to extend New START, which limits the deployed numbers of nuclear-capable ICBMs. Russia has chosen to treat its HGVs as falling within the New START definition of ICBMs, so it seems that their strategy is truly qualitative, not quantitative: they aim to invalidate BMD with diversity of delivery systems, not with ever-growing numbers.

Missiles in pursuit of missions

What about the U.S.? Does America have a strategy for HGVs? The U.S. Department of Defense considers HGVs so desirable that Under Secretary of Defense for Research and Engineering Michael Griffin has called them his top priority. But it’s awfully hard to say why.

(For background on these issues, nothing beats James Acton’s 2013 volume Silver Bullet?.)

One reason often mentioned is that Russia and China are deploying them. Of course, America already has ways to hit back at these countries, if needed. HGVs are especially well-suited to thwart BMD systems based on midcourse interceptors, but neither of these countries has shown much interest in deploying this sort of defensive technology against ICBMs. And as already discussed, when it comes to evading terminal-phase interceptors, it’s unclear whether the superior maneuverability of HGVs outweighs their slower speed as they approach the target.

Another common justification for interest in HGVs is that they fly fast. But as noted above, ballistic missiles already fly faster than HGVs of the same range. ICBM reentry vehicles approach their targets moving at around 20 times the speed of sound, which places them at the realistic upper end of the “hypersonic” category so celebrated of late.

The U.S. has often presented its HGV programs as conventionally oriented. There is a logic to this view that could help to explain the pursuit. Major policy statements (such as the 2018 nuclear posture review, p. 21) increasingly have emphasized the integration of planning for America’s conventional and nuclear arsenals. One could therefore imagine a strategy of limiting nuclear arsenals while expanding the conventional HGVs and BMD systems that could threaten the viability of an adversary’s nuclear forces.

Indeed, going back to the negotiation of New START, the American position has been that HGVs do not meet the treaty’s definition of ballistic missiles, and should therefore not count against its ICBM limits.

But there are big problems with ascribing such a strategy to the Trump administration. First, it has not articulated any such concept. Second, it appears increasingly less interested in limiting its ambitions for ICBM-range BMD to just North Korean or Iranian ICBMs, which seem like the only halfway realistic targets for such an ambitious concept. Third, in the same connection, it shows no interest in extending New START or negotiating a follow-on treaty. Failing to further reduce or even to retain present limits upon the Russian target set suggests no great interest in achieving a viable conventional counterforce option.

Despite its indifference to arms control, neither does the Trump administration seem to desire a numerical buildup of its own nuclear forces. Indeed, the costs of modernizing the entire U.S. triad can be expected to drive deployed numbers down over the coming decade or two.

In short, while one could imagine a strategy involving BMD and conventional HGVs against limited nuclear target sets, there is no evidence that such a strategy is in place. Instead, there is an increasingly unconstrained appetite for new strategic weapons technologies, seemingly for their own sake. Invocations of “competition” can be heard, but they fail to explain either the nature of the competition or how current programs serve it. Similarly, reproducing the nuclear triad more or less as we know it seems to have become an end in itself, more important than any particular mission or force levels, either absolute or relative to Russia’s.

What would make sense?

Security isn’t simply a function of resources and technology. Arms are tools, and without some purpose and design, there is no rational way to judge which ones to select.

What might an American nuclear strategy look like? I’d modestly suggest an emphasis on two dimensions of stability—crisis stability and arms stability. In simple terms, this means that international crises shouldn’t involve a high risk of the use of nuclear weapons, and that major states should avoid arms-racing. These are truly modest goals, aiming at national survival, care with finite national-defense resources, and not unnecessarily inflaming antagonisms.

The next Congress and a new administration—for there is little hope that the current one can think or plan strategically—might well consider what policies and programs would best serve these sorts of objectives. That’s a subject I may return to in the new year.