The UK has expressed interest in deploying a constellation of high altitude balloons for military intelligence, surveillance, and reconnaissance (ISR) coverage from the stratosphere.
British interest peaked after two technology companies, Voltitude and Languard Systems, in partnership with Aerostar, an American company, trialled the concept in South Dakota, United States, earlier this year according to a government statement on 27 July 2025.
With an ISR payload capacity of up to three kilogrammes, the test balloons can operate continuously for more than five days. Each balloon can travel over 2,000 nautical miles at an operating altitude between 60,000 and 80,000 feet, double that of a commercial aircraft.
The findings will be used to build upon this current capability, exploring whether the balloons can carry heavier payloads for longer durations, with the aim of enabling missions lasting between six and 12 months.
Project Aether
The test was conducted as part of Project Aether, a Ministry of Defence concept development initiative for uncrewed, stratospheric, persistent communication and ISR provided by low-cost platforms known as High Altitude Pseudo-Satellites, or HAPS.
Launched by the Future Capability and Innovation team, situated within Defence Equipment and Support, the UK’s defence procurement agency, the unit has since transitioned to become part of UK Defence Innovation (UKDI) under the National Armament Directorate (NAD) in what appears to be a vague restructuring of MoD institutions under the Labour government.
A senior MoD official under the previous Conservative government confirmed in March 2023 that a feasibility activity has been conducted since 2016 to demonstrate the utility of stratospheric aircraft.
In that time, the project has conducted a range of methods including with fixed wing aircraft and balloons.
Efficacy of ISR balloons
The use of balloons in the stratosphere is not new. The method has been used to collect scientific data and to monitor earth’s atmosphere. The European Space Agency carried sensor payloads via balloons travelling between five and 115 kilometres above the earth’s surface, all the way from Sweden to Canada in a four-day voyage in December 2024.
Likewise, the military applications have demonstrated some efficacy in recent years. Infamously, China sent several balloons to cross the continental United States and Latin America to much consternation in early February 2024.
One of the systems was monitored all the way from the North-West Pacific and subsequently shot down by a US Air Force F-22 Raptor using a Sidewinder missile over the South Carolina coast, out of harm’s way.
The Chinese state confirmed the high altitude balloon originated from China but claimed it was a civilian airship used for research and meteorological study.
Yet, the Chinese balloon exceeded the size, payload, and flight time of a normal weather balloon. It was said to be 200 feet tall, with solar panels and a surveillance payload the size of a regional jet, weighing more than 2,000 pounds.
A low-cost alternative
Although the system was shot down, the concept still proved its worth from a cost analysis view for cash-strapped countries like the UK, for whom the feasibility of a British equivalent to the American Golden Dome is far out of their fiscal reach.
These low-cost, attritable balloons will fill a much-needed ISR or airborne early warning capability across the nation.
Aerostar builds balloons similar to the type of balloon shot down off the coast of South Carolina, and they say that their balloons are “filling the capability gap between aircraft and satellites.”
Similarly, Maria Eagle, the UK Minister for Defence Procurement and Industry, commented: “Stratospheric technology like this could transform how we operate in complex environments, keeping our people safer and better informed than ever before.”
