Further to this post,
1) an excerpt from a report by the Congressional Research Service:
As Congress reviews the Pentagon’s plans for U.S. hypersonic weapons programs, it might consider questions about the rationale for hypersonic weapons, their expected costs, and their implications for strategic stability and arms control. Potential questions include the following:
*What mission(s) will hypersonic weapons be used for? Are hypersonic weapons the most cost-effective means of executing these potential missions? How will they be incorporated into joint operational doctrine and concepts?
*Given the lack of defined mission requirements for hypersonic weapons, how should Congress evaluate funding requests for hypersonic weapons programs or the balance of funding requests for hypersonic weapons programs, enabling technologies, and supporting test infrastructure? Is an acceleration of research on hypersonic weapons, enabling technologies, or hypersonic missile defense options both necessary and technologically feasible?
*How, if at all, will the fielding of hypersonic weapons affect strategic stability?
*Is there a need for risk-mitigation measures, such as expanding New START, negotiating new multilateral arms control agreements, or undertaking transparency and confidence-building activities?..
2) And excerpts from a report by the International Institute of Strategic Studies:
Speed and manoeuvrability
Hypersonic weapons are not notable because of their speed alone. Traditional ballistic missiles with ranges above 300 km and their re-entry vehicles also fly at hypersonic speeds, albeit in the vacuum of space. An intercontinental-range ballistic system has an initial speed of approximately Mach 17–20. HGVs [hypersonic glide vehicles] differ because they spend most of their time gliding in the upper atmosphere, combining speed with manoeuvrability. The target of a traditional ballistic missile is largely predictable early in flight based upon its trajectory. Some re-entry vehicles have a limited capacity to change direction once detached from a ballistic missile, but HGVs can use aerodynamic forces to manoeuvre laterally to targets hundreds of kilometres away from the location indicated by the bearing of their initial launch.
HGVs also differ because of their flight altitude. Traditional ballistic missiles are fired into outer space – beyond the Kármán line at 100 km in altitude, which traditionally defines the boundary of the atmosphere – and their re-entry vehicles follow a long, arcing trajectory towards their target. Missile-defence systems can detect ICBMs from distances of 3,000–4,000 km. HGVs coast towards their targets in the stratosphere, 30–50 km above ground. This appreciably reduces the range at which ground-based radar can track incoming hypersonic weapons, giving rise to efforts to create airborne high-altitude or space-based infrared tracking systems that can observe hypersonic vehicles at greater ranges. Some prototype HGVs use a non-ballistic launch platform, meaning that they would not be readily detectable by overhead early-warning systems. This could delay identification of the source of the missile and disrupt decision-making in response to the missile detection.
If used tactically, hypersonics are significantly more capable than subsonic weapons. They are marginally better than conventionally armed intermediate-range ballistic missiles (IRBMs), which are currently part of China’s arsenal. Russia and the US do not possess IRBMs because they were prohibited by the 1987 Intermediate-Range Nuclear Forces (INF) Treaty, but may acquire them given the treaty’s dissolution last year. The proliferation of IRBMs or HGVs has the potential to threaten mobile ground-based nuclear forces that until now have been largely invulnerable to attack. This is because both weapons are fast enough to destroy mobile missile launchers during the short window of time when they stop to prepare to fire. If countries begin spending to modernise, expand and further defend their nuclear forces in response to hypersonic capabilities, it could instigate the kind of action–reaction security competition that necessitated the creation of arms-control agreements during the Cold War to restore strategic stability [emphasis added]…
Dual-capable weapons – including ballistic missiles, HGVs and hypersonic cruise missiles – can be configured to carry only conventional payloads, only nuclear payloads, or either one ambiguously. The existence of these weapons is itself destabilising unless states remove the ambiguity, declaring in advance and providing verification that certain weapons will carry only conventional or only nuclear warheads. If ambiguity remains, a target state, upon detecting an incoming missile, could infer that the payload is nuclear and respond in kind. This problem is exacerbated by the speed and manoeuvrability of HGVs and hypersonic cruise missiles, because they shorten the decision window following radar detection – increasing the risk of miscalculation or misperception – and because they leave doubts about their intended targets. The speed of ballistic weapons is already a threat to crisis stability, regardless of recent advances in hypersonics. If states begin using weapons that are more manoeuvrable, and in dual-use fashion, it will risk a return to the policy of launch-on-warning for retaliatory strikes (i.e., firing after the detection of an incoming missile, but before impact).
The US has stated that its hypersonic weapons will not use nuclear warheads. Russia’s Avangard will likely be used for nuclear weapons only. China has not declared how the DF-17 will be used [emphasis added]. Depending on its maximum operating speed, a DF-17 launched from China’s eastern coast could reach all of South Korea and most of Japan within 12 minutes, which includes time for launch, separation of the glide vehicle and the slowing effect of the atmosphere during the HGV glide phase. At these speeds, it could reach US bases on Guam in 15 minutes. In the optimistic scenario in which the HGV is detected shortly after launch, decision-makers would have a few minutes to consider the nature of its payload. In a conflict between China and India, India could fear for the survivability of a large portion of its nuclear arsenal, making launch-on-warning yet more likely…
By the mid-2020s, hypersonic weapons will likely enter the arsenals of China, Russia, the US and perhaps other countries amid renewed proliferation of other types of offensive and defensive weaponry. In an unwelcome confluence of events, hypersonic technology is maturing just as major Cold War arms-control treaties are being dismantled. The US announced its withdrawal from the INF Treaty on 2 August 2019, after almost a decade arguing that Russia’s development of a ground-launched cruise missile, the 9M729 (SSC-8 Screwdriver), breached the terms of the agreement. It was also keenly aware that China was not a signatory to the treaty, and has been free to deploy many of the ground-launched ballistic and cruise missiles that threaten US air and naval forces in the Western Pacific.
New START, the last major arms-control treaty still in force, was signed by the US and Russia in 2010 and caps the size and number of their nuclear warheads, ICBMs and submarine-launched ballistic missiles. The treaty will expire in February 2021, unless Washington and Moscow agree to an extension. Russia has suggested it is willing to do so, and the Russian foreign ministry has said that it considers Avangard to be bound by the treaty’s missile limitations. The Trump administration has been sending mixed signals about whether it supports renewal or creating new agreements to limit the proliferation of new types of weapons. China is unlikely to agree to any constraints on its ability to develop new weapons, even if they are destabilising [emphasis added, see this post: “China, or, Why the US Needs to Continue in the New START Nuclear Weapons Treaty With Russia“].
It is unclear whether the unique tactical characteristics of hypersonic weapons – speed, manoeuvrability and the capability to penetrate all currently deployed missile shields – will give rise to a Cold War-style cycle of action and reaction among competing states. If this does occur, new arms-control initiatives could focus on limiting the most destabilising problems caused by the new weapons. For example, agreements could establish a system for on-site inspections to remove warhead ambiguity, limit the colocation of forces, ban hypersonic weapons from borders and coastlines in order to increase times to target, or prohibit the development of new types of hypersonic weapons or of weapons above certain speed thresholds. That these proposals seem politically unattainable today – alongside broader trends against all forms of arms control and towards great-power competition – suggests that the situation is as difficult as it was at the beginning of the 1980s [emphasis added].
Relevant earlier posts:
A real revolution in missile affairs? An arms control nightmare as the weapons proliferate amongst the three powers? And others? France for one.
In a Japanese-language document published on the Acquisition, Technology and Logistics Agency website, the government said two classes of standoff hypersonic systems will be deployed — the Hypersonic Cruise Missile (HCM) and the Hyper Velocity Gliding Projectile (HVGP).
The former will be powered by a scramjet engine and appears similar to a typical missile, albeit one that cruises at a much higher speed while capable of traveling at long ranges.
The HVGP, on the other hand, will feature a solid-fuel rocket engine that will boost its warhead payload to a high altitude before separation, where it will then glide to its target using its altitude to maintain high velocity until impact…