Hypersonic missiles

DOI: https://doi.org/10.58248/PN696

There is no universally accepted definition for the term ‘hypersonic missile’, however it is typically used to describe missiles that travel within the Earth’s atmosphere for sustained periods at speeds greater than five times the speed of sound, whilst being able to make significant manoeuvres that change the missile’s direction.

Hypersonic missiles are being developed by several countries and have reportedly been deployed by Russia and China. The US also has multiple hypersonic weapons programmes and are conducting tests. The UK does not have a hypersonic missile capability, but the Ministry of Defence has announced a hypersonics programme to develop “future hypersonic concepts and technologies”. Furthermore, in 2022, it was announced that Australia, the US and the UK would collaborate on the development of hypersonic and counter-hypersonic capabilities via the AUKUS security partnership.

The type of missions that a hypersonic missile could be used for will depend on the missile type, as well as its range, speed, type of warhead, and launch platform. Potential applications might include rapidly striking high-value, time-sensitive or mobile assets; long-range precision strikes; and enhancing nuclear deterrents (although their potential effectiveness in this context is debated).

Missile defence is complex, expensive and technically challenging, particularly for nationwide defence against long-range missiles like intercontinental ballistic missiles. The manoeuvrability, altitude and speed of hypersonic missiles may pose challenges for current missile defence systems designed to counter ballistic missiles. These could include later detection and less time for the target to make decisions and respond. Existing missile defence systems would need to be adapted to better counter hypersonic missiles, which would likely require significant investment.

Key Points:

• Hypersonic missiles combine speeds of over five times the speed of sound with significant manoeuvrability during flight.
• Their manoeuvrability enables them to change trajectory during flight, making their flight-path and target difficult to predict.
• They fly at lower altitudes than ballistic missiles, which means that they may be harder to track at long distances with some surface-based sensors, such as certain radar.
• There are two main types of hypersonic missile: hypersonic glide vehicles (HGVs) and hypersonic cruise missiles (HCMs).
• HGVs are mounted onto rocket boosters for launch and may be accelerated to speeds of Mach 20 or more. The glider then separates from the booster and flies unpowered in the Earth’s upper atmosphere at altitudes of 30-80 km, before diving towards the target.
• HCMs typically have a ramjet or scramjet engine that enables them to reach hypersonic speeds at altitudes of 20-40 km.
• China and Russia have reportedly deployed hypersonic missiles that could deliver conventional or nuclear weapons. The US is testing multiple hypersonic technologies.
• The AUKUS agreement between the UK, US and Australia includes developing hypersonic and counter-hypersonic technologies.
• Developing hypersonic missiles requires significant research and development challenges to be overcome, contributing to their high development and manufacturing costs.
• The speed, manoeuvrability and altitude of hypersonic missiles may challenge existing missile defences, although their uses and effectiveness are still being assessed.
• Defence analysts disagree about the potential implications of hypersonic missiles for global peace and stability. Some suggest they could increase the risk of conflict escalation, while others say that they will not alter the strategic balance between nuclear powers.
• Arms control, export controls and other measures may help limit potential harm to peace and stability, but these approaches face challenges.

Acknowledgements:

POSTnotes are based on literature reviews and interviews with a range of stakeholders and are externally peer reviewed. POST would like to thank interviewees and peer reviewers for kindly giving up their time during the preparation of this briefing, including:

• Members of the POST Board*
• The Ministry of Defence*
• Iain Boyd, University of Colorado Boulder*
• Joshua Pollack, James Martin Center for Nonproliferation Studies*
• Justin Bronk, Royal United Services Institute (RUSI)
• Sidharth Kaushal, Royal United Services Institute (RUSI)*
• Paul Bruce, Imperial College London*
• Rob Klein, MBDA UK*
• Andrew Pyle, MBDA UK*
• Peter Hall, MBDA UK*
• Lockheed Martin*
• Geraint Evans, Raytheon UK*
• Andrew Futter, University of Leicester*
• Ioannis Vagias, Cranfield University
• Simon Prince, Cranfield University*
• Tom Karako, Center for Strategic & International Studies*
• Masao Dahlgren, Center for Strategic & International Studies*
• Cameron Tracy, Stanford University Center for International Security and Cooperation*
• Timothy Wright, The International Institute for Strategic Studies*
• Douglas Barrie, The International Institute for Strategic Studies*

*denotes people and organisations who acted as external reviewers of the briefing.

Image credit: Mike Tsukamoto, USAF staff.