UK completes hypersonic propulsion tests

The UK, working with the US government and industry has completed a series of hypersonic propulsion tests bringing the UK’s programme to develop a hypersonic cruise missile by 2030 closer to fruition, according to a 6th April MoD press release.

The test team was led by the UK’s Defence Science and Technology Laboratory (Dstl) together with the US Air Force Research Laboratory (AFRL) and supported by industry partners including Gas Dynamics, and SME from the UK. They carried out 233 successful static test runs over six weeks at the NASA Langley Research Centre in Virginia, USA. 

The data from the tests was analysed in real time and will help inform performance improvements for the propulsion system. Tests were conducted at various speeds from subsonic to hypersonic and explored different design variations, the press release states. Adding that the tests validate a high performance engine for a hypersonic air-breathing cruise missile. 

“This milestone represents a critical advancement in the UK’s defence capabilities and reinforces our standing in the AUKUS hypersonic weapon development collaboration,” Paul Hollinshead, the DSTL chief executive said. 

Very little information is available on Gas Dynamics, the single sheet of information on the company’s website states that it has been involved in eight different hypersonic flight test projects including several projects examining hypersonic flight for commercial purposes. 

The UK’s Team Hypersonics was set up to coordinate the development of a hypersonic missile for the British armed forces. A Hypersonic Technologies & Capability Development Framework with £1 billion in funding was announced in 2023 and joined by 90 different organisations by 2024 that then became eligible to bid for the MoD development contracts looking to deliver hypersonic capabilities. 

The UK is in need of a complex weapons refresh as its stocks of Storm Shadow cruise missiles have been depleted through donations to Ukraine. And delays around decision making on the Spear 3 capability mean that the RAF would primarily be armed with Paveway guided bombs for any ground attack roles in the near future. The British Army has considered the Precision Strike Missile (PrSM) from Lockheed Martin, but a final decision on that project will depend on the outcome of the UK’s Strategic Defence Review. Notably, ballistic missiles or quasi-ballistic missiles like PrSM are already quite difficult to intercept, leading some to argue there is no need for hypersonic missiles as conventional ballistic missiles are sufficiently capable and survivable. 

Calibre comment

The costs of developing a hypersonic missile are huge – from start to finish – and success is far from guaranteed. This is because there is a great deal about hypersonic flight that is not known or understood. It means that development requires extensive testing, adding cost and complexity to any programme. Alongside this, the costs of producing the missiles are likely to be significant, dwarfing those of conventional cruise missiles. While the promised speed and manoeuvrability of the missiles makes them difficult to intercept and compresses an adversary’s timeline for doing so, the increased costs may reduce the quantity that can be procured.

This is problematic as the effects are not necessarily increased by the speed – the amount of explosives it takes to destroy a building do not decrease significantly just because the missile is moving faster – for example. So, it stands to reason that if it takes four conventional cruise missiles like Storm Shadow to destroy a building, it would also take four hypersonic cruise missiles to destroy the same building, assuming that they could match the Storm Shadow pound-for-pound in payload. 

Ultimately, pursuing more survivable missiles is a good thing, Russian, Chinese, and Iranian air defences are certainly capable and require a considered approach. But there is a balance that needs to be found between very expensive capabilities like hypersonic cruise missiles and having the mass to deter or defeat an adversary. Without this balance, the UK and others may risk sacrificing funding for other, proven capabilities, in pursuit of hypersonics that offer potentially un-proven benefits.