UPDATE: Bill Gertz reported on Dec. 4 that China had conducted “this week” a third test of its WU-14 hypersonic boost-glide vehicle, according to his unnamed military sources. I expect that a test was conducted, although its outcome remains publicly unknown. Gertz quoted Carnegie expert Lora Saalman as saying that a third test (the quote gave no indication that Saalman had independent information about it) showed that the WU-14 “is a priority program for China”; Gertz also quoted China threat monger Richard Fisher as saying the test shows the need for more funding of rail guns, which “offer great potential for early solutions to maneuvering hypersonic weapons.” [I don’t think that makes even a little bit of sense. The problem with shooting at fast objects with fast guns is that they tend to shoot past each other, and the problem with rail guns is that rocket motors are cheap but guidance systems less so. But I digress.] The main point is that if, in fact, China did conduct another test, successful or not, there is nothing the United States can say about it, since we continue to say nothing about a possible test ban. Indeed, the more likely response is to accelerate US hypersonic programs, as advocated by another of Gertz’s sources.
Recent Chinese (Aug. 7) and American (Aug. 25) hypersonic missile development tests have highlighted an otherwise little-noted element of the resurgent technological arms race, an element that now involves at least the United States, China, Russia and India, with France and Britain lurking in the wings and no doubt other nations watching closely. The failures of those tests have highlighted also another fact: hypersonic propulsion and flight are difficult technologies involving extreme airspeeds, temperatures, pressures, stresses and combustion rates, combined with the usual requirements for compact airframe construction and low weight. These technical challenges have frustrated hypersonic development programs for decades, and if their solution may now be within reach, using new materials and high-performance computing to solve the exquisite problems of extreme engineering, it remains inconceivable that hypersonic weapons could be developed, perfected and validated for operational use without actual testing.
Two Evil Birds, One Good Stone
A bit of clarification is in order here: hypersonic missiles actually fall into two distinct categories. In boost-glide, the hypersonic weapon is first “boosted” onto a ballistic trajectory, using a conventional rocket. It may cover considerable distance as it flies to high altitude, then falls back to Earth, gaining speed and finally, at some relatively low altitude, pulling into unpowered, aerodynamic horizontal flight. After that, it glides at hypersonic speed toward its final destination. The second category is powered hypersonic cruise missiles, which typically are launched with a small rocket to high speed, and then drop the rocket and ignite a supersonic combustion ram jet, aka scramjet, for powered flight at Mach 5 or greater.
The recent failed Chinese and American tests were of boost-glide systems, while the X-51 WaveRider, which the US successfully tested last year after a string of failures, is an example of the scramjet cruise. The boost-glide test failures were probably caused by issues with the booster rockets rather than with the hypersonic gliders, although system integration can also cause problems. In any case, these systems didn’t work, and that demonstrates that both boost-glide and powered cruise missiles require testing. Such tests are easily observable from space, radar, signals intelligence and old-fashioned spying. A test moratorium would thus throw a huge obstacle in the path of all these programs, and a permanent test ban would make it clear that they aren’t going anywhere. And that would be a good thing, because where they are going is nowhere good.
It’s not often that one can say an entire technology is evil and should be stopped and banned because it has no positive use. Hypersonic missiles present such a case. There is simply nothing they are likely to be useful for outside of war between major, nuclear-armed powers. LA to Tokyo in an hour? As unlikely as that is to become technologically possible in the near future, let alone economically justifiable in an era of high-cost energy and low-cost video telepresence, if it ever could make sense it would take the form of a large airplane, not a small missile. Low-cost satellite launches? Hypersonic space planes such as DARPA’s planned XS-1, which would lift rockets to high altitude and initial speeds around 3 km/s, might make sense, but again, to achieve economies of scale, they would tend toward large size; when cost is the driver it would make no sense to build them small.
What’s all this hype about anyway?
Back in the crazy days after 9/11, hypersonic weapons were sold as a form of “conventional prompt global strike” to fulfill the supposed need for a weapon that could be launched from fortress America and strike Osama bin Laden’s lair on the other side of the world in less than an hour. That was an idea so nutty that, unfortunately, few people took the matter seriously, even when it was later revealed that another killer app for prompt global strike was to destroy Chinese anti-satellite weapons before they could be launched. Of course, when the US military finally did get bin Laden, it was a Special Forces raid launched by helicopter from nearby Afghanistan. And it was never very clear why China would be any less offended by our targeting their strategic weapons and facilities, deep inside the Chinese mainland, with hypersonic cruise missiles rather than somewhat faster ballistic missiles. The vague reasoning is that the Chinese (or Russians, in some other scenarios) might mistake ballistic missiles with conventional warheads for those with nuclear ones. However, hypersonic missiles could also carry nuclear warheads, and more to the point, in an attack on China or Russia the likely targets would include Chinese or Russian nuclear weapons, and other systems of strategic importance in a major war between nuclear-armed powers. To imagine that such exchanges could be kept polite by using a fancier, slower, and hardly any stealthier type of missile is the kind of airy fantasy that survives in political discourse precisely because it obviously isn’t serious. But the race to develop and deploy hypersonic weapons is serious.
Although these weapons are slower than ballistic missiles, they are still very fast, and offer a different attack profile, presenting a qualitatively different threat to adversaries. The idea that they might be used to attack a nuclear power, and even its nuclear weapons and related strategic faciliites, because they would be easily distinguished from ballistic missiles, and the enemy might be willing to believe that no hypersonic weapons carried any nuclear warheads, can hardly be expected to be stabilizing. Rather, this theory purports to pose a credible threat of strategic strikes in spite of nuclear deterrence. It must be expected that potential adversaries will seek countermeasures including symmetrical capabilities; indeed, this is apparently just what China and Russia are doing. Hypersonic missiles are not only intended for deep land attack, however. They are also likely to be used at sea, for attacking ships, island bases and shore facilities. Shortening the strike time for naval missile warfare is a recipe for hair-trigger confrontation between major powers contending for regional or global dominance. If there is a way to stop or slow this development, we should take it.
How to stop a speeding hypersonic missile race dead in its tracks
Fortunately, a hypersonic missile test ban would be one of the most rigorously verifiable arms control measures one could think of. It could begin with an informal moratorium, which might be agreed and announced among the major players, and followed up by negotiations for a binding, permanent ban treaty. I would propose a moratorium on tests of any aerodynamic vehicle of less than, say, 10 meters length and 1 meter diameter, traveling in powered or unpowered flight at speeds in excess of 1 km/s over a horizontal distance greater than 100 km. These numbers are somewhat arbitrary and could be fine-tuned or adjusted substantially while preserving the intent of the agreement. However, it is desirable to maintain as wide a margin as possible between what is allowed and what we seek to prevent. The numbers suggested here would just barely permit Russia and India to retain their joint BrahMos 1 supersonic cruise missile, while forcing them to cancel the hypersonic BrahMos 2. The US and China would then be permitted to develop comparable systems, but would have to cancel their hypersonic programs. While an even lower speed limit would be desirable, canceling future programs verifiably via a test ban should be easier to agree on than eliminating existing proven and deployed systems. We should just do it – and later do more.
The United States should take the lead in proposing a hypersonic missile test moratorium and seeking a permanent test ban. Production, stockpiling, deployment, transfer and use should also be prohibited under a permanent treaty, but the test ban is the critical element which makes any such agreement feasible, because it would be reliably verifiable and all but preclude the rest. Nations do not go to war relying on untested weapons, particularly not aggressive war, when they have a choice. Hypersonics are a technology particularly in need of thorough testing both to perfect and to validate weapon systems. Fortunately, it is also a technology, and a new type of weapon, that we are not in need of. Neither are any other nations, but of course we can’t expect that just because the United States proposes a test ban, other nations will line up to join in renouncing hypersonic missiles. That is one reason why I am not proposing the US self-impose a unilateral moratorium, although it wouldn’t hurt if we suspended testing for a while to show good faith. What we can reasonably hope is that other nations will see their shared interest in avoiding or slowing a dangerous escalation of the arms race. If not, we will resume our programs, while still advocating that everybody agree to stop. Let the Russians, the Chinese, the Indians or the French play the spoilers, and let’s seize the moral high ground. The fact that others might not join us there is no excuse for not going to the mountaintop and calling them to join us. Indeed, if we are unwilling to do so, others have every reason to be cynical about our real motives and intentions. I’m not sure myself that I know what those are. But I am reasonably sure that hypersonic missiles will not help to make America stronger or more secure, because everybody we might want to target with them will soon enough get their own, and the world will then be a more dangerous place.