Abstract
A prevailing orthodoxy is recently emerging around hypersonic weapons. It is one characterised by eminent and imminent threat. This impression is largely misguided and misleading and should be challenged.
Keywords: Hypersonic, Weapons, Military
By Joseph Dillon
Introduction
Hypersonic weapons are an awesome military power that threaten to totally upend the conduct and course of modern warfare. The only rational response is to fear them or, for the few more technologically gifted nations, to covet them. At least, such is the logic advanced by mainstream reporting. However, the conversation is grossly misinformed; suffering from a dearth of critical analysis, a striking propensity to sensationalism, and an ignorance of the wider missile defence debate within which it is couched. Many claims about hypersonic systems do not survive the most basic scrutiny. This article will briefly outline the nature and supposed logic of these systems, the current state of affairs, and provide a convincing rebuttal to mainstream thinking on the subject.
Little warning, no defence
Hypersonic weapons are generally split into two categories: boost-glide vehicles (HGVs) and self-powered cruise missiles (HCMs). Both require an initial boost atop a conventional rocket motor but differ in terms of average operational height and speed. HCMs are powered by a scramjet engine to speeds of between Mach-5 and Mach-10 and operate at heights of around 30km. HGVs are boosted into space - above 100km - and glide along the upper atmosphere at speeds up to Mach-20 [1]. There are many other technical details but the two most important features of these weapons are speed and manoeuvrability.
Attempting to intercept an attack of this nature has repeatedly been compared to “trying to hit a bullet with a bullet” [2]. In fact, the analogy is an understatement as even the slowest HCM will travel many times faster than a bullet. At the higher HGV speeds, one could arrive in Berlin after leaving Moscow in under 5 minutes. Even if a defensive system could somehow intercept these vehicles, their manoeuvrability makes destroying them an intractably complicated endeavour. The same nimbleness may grant the ability to simply avoid ground-based detection stations entirely - a weapon that arrives without ‘meaningful warning’ [3]. The combination of being impervious to defences and the seriously compressed decision-making window afforded to those under attack fuels the assertion that hypersonic weapons represent a new ‘challenge to strategic relations between nuclear powers’ [4].
Concern seems warranted. Especially given that recent major strides in this area seem to have been achieved by Russia and China as ‘any advantage that US hypersonic R&D (Research and development) once held has largely eroded away’ [5]. Russia continues to test several configurations of glide vehicles and cruise missiles that can reportedly achieve hypersonic speeds. Its Avangard system, an HGV design first tested in 2018, struck its target ‘like a meteorite … a fireball’ according to President Vladimir Putin [6]. On the President’s birthday in 2020, the Zirkon HCM was showcased as a ship-killer immune to conventional defences. There are plans for extensive testing of both systems throughout 2021 [7]. Similarly, China has made sure to parade its successes in this arena by literally parading its Dong-Feng HGV system (DF-ZF) during the 2019 70th anniversary celebrations. Its Xingkong-2 programme is believed to be an HCM system set to be fully developed by 2025 [8]. Despite the difficulty in verifying such claims, the United States Strategic Command believes both Russia and China to be in possession of nuclear-capable hypersonic missiles of the type described above [9].
Given the reporting that usually accompanies these developments, it is unsurprising the conversation can often seem so distorted. The BBC, on Russia’s claimed successful test of its Avangard missile, rightfully raised questions about the weakening international legal arms control regime but drew no suspicions about Russia’s technical claims and were willing to reproduce the remarks of President Putin and Defence Minister Shoigu verbatim [10]. Similarly, Reuters duplicated the unsubstantiated ‘carrier-killer claims of Beijing about its own hypersonic weapons and repeated the myth of missiles that can ‘manoeuvre sharply’ at high speeds [11]. The New York Times piece (quoted earlier) certainly features factual accuracies but is emblematic of much reporting in parroting common myths and is particularly egregious in its sustained recourse to hyperbole. The weapons are claimed to be nearly invisible, to possess ‘incredible manoeuvrability’, and to be ideal for carrying out a ‘decapitation strike’ of a country’s entire political leadership [3] among a plethora of other claims unaccompanied by convincing evidence.
Reality Check
Ostensibly, there is a neat and digestible argument in favour of the West recuperating its lead in hypersonic technologies, but only for a few issues. First; most claims about capabilities are exaggerated. Even if we are to believe the speed figures given by Moscow and Beijing, their testing regimes so far have pushed their platforms to endure such speeds for only a few dozen seconds - a far cry short of sustained hypersonic flight. Claims about agility are necessarily vague or highly implausible. Smith [3] is grossly effusive about unpredictable manoeuvrability but fails to mention that, because the atmosphere is so thin, control surfaces are effectively useless above 100km: a fact reconfirmed by a recent RAND study [12]. Below 100km any control surface attempting to significantly alter the trajectory of a vehicle at the speeds described would be subject to forces akin to a plasma cutter. Materials science has come a long way but we remain bound by the laws of physics and the materials available to us. Thus manoeuvring in the mid-atmosphere is plausible but only briefly and certainly not to the extent that is normally claimed. Also, the common contention that the weapons arrive with little or no warning is ludicrous. The heat plumes generated either by the scramjet engine or from the glide vehicle are easily detectable by space-based infra-red monitoring satellites [13].
The second issue is that hypersonic technology does not represent a significant shift in strategic capabilities; conventional cruise and ballistic missiles achieve the same objectives at lower costs and sometimes greater efficacy. For example, the subsonic, low flying Tomahawk cruise missile, with its ability to evade most radar systems by ‘skimming the treetops’ [14], gives defenders less than 30 seconds to mount a response from detection to impact. No hypersonic weapon is comparably stealthy because they would soon disintegrate in the thick air of the lower atmosphere.
Conventional ICBMs outperform hypersonics too. They will often reach their targets faster, may be more difficult to intercept and have an unquestionable reputation for accuracy. It is true that the systems designed to intercept ballistic missiles (THAAD, Aegis, Patriot, GMD) are unlikely to be of any use against HGVs or HCMs but this belies the fact that they are almost as ineffective against ICBMs themselves [15]. The history of anti-ICBM technology is a litany of failures. Even in laboratory conditions, it is estimated that a single intercept vehicle has only a 25% chance of destroying its target [16]. Thus ICBMs, which still number in the thousands, already pose a greater threat than hypersonics. Yet we are never subjected to sensationalist claims of an imminent threat from these weapons.
Perhaps the really dangerous aspect of hypersonic weapons is that in their initial rocket-assisted boost phase, they are indistinguishable from nuclear delivery systems - a point raised by the UN Office for Disarmament [17]. Should Russia or China decide to employ these weapons in battle, they risk the United States mistaking a launch for a potential first-strike nuclear engagement. Even if American decision-makers are cool-headed enough to wait and see if the launch results in a familiar ballistic vehicle trajectory or something more exotic, the calculation remains the same. Both Moscow and Beijing have indicated that their hypersonic systems will be ‘dual use’, capable of delivering nuclear or conventional warheads [18]. It is not United States policy to wait for a potential nuclear weapon to explode in order to confirm their suspicions. In this regard though, hypersonic weapons are no more dangerous in their ability to engender miscalculation than existing ICBMs.
Conclusion
The hypersonic weapons debate suffers from uncritical, technically misinformed, and often exaggerated commentary. We must assess jingoistic claims of technological success with scepticism and never publish unfiltered government propaganda. In any case, it seems bizarre that we should be compelled to panic about a potential system that represents no greater threat than the ones we have been living with for decades. Either concern is warranted - in which case we should be far more concerned about the arsenals of ICBMs and low flying cruise missiles, or concern is not warranted - in which case we should carefully examine the motivations of those feeding the hype around these weapons. As the US hypersonic R&D budget jumped to $2.6 billion for 2020 and is expected to increase again [19] the possibility for lucrative, long-running government contracts is not something weapons manufacturers have been known to discourage.
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