Hydrogen-powered Houthi drones

Conflict Armament Research (CAR) field investigators have uncovered evidence that Ansar Allah (‘Houthi’) forces in Yemen are attempting to use hydrogen fuel cells to power their uncrewed systems. If successful, this experimentation would represent a major escalation in Houthi capability, enabling uncrewed vehicles—whether aerial, ground, or maritime—to carry larger payloads and to travel for far longer periods and ranges than conventional power sources allow. To CAR’s awareness, this is the first attempted use of hydrogen fuel in uncrewed systems by any non-state armed actor, globally.

This is the first attempted use of hydrogen fuel in uncrewed systems by any non-state armed actor, globally.

On 12 and 13 November 2024, CAR deployed to Mokha, a key port city on the south-west coast of Yemen, alongside maritime security units of the Yemeni National Resistance Forces (NRF). Established in 2018, the NRF is commanded by General Tareq Saleh, who is also part of the  Yemen Presidential Leadership Council .

The vessel had been transporting a consignment of chemical fertiliser products to the Houthi-controlled port of Salif. NRF personnel discovered, however, that the cargo also contained a large amount of undeclared componentry for the development of advanced conventional weapons, including uncrewed aerial vehicles (UAVs):

• measuring instruments, manufactured by a company that was sanctioned by the United States in 2024 for its links to Iranian and Houthi missile production;
• hundreds of commercial-off-the-shelf UAVs;
• maritime radar and automatic identification system units;
• UAV detection and electronic countermeasure equipment; and
• advanced communications material.

Documents recovered with the gas tanks clearly indicate that they are in fact hydrogen cylinders, intended for use in a fuel cell system for UAVs.

Each documented system consists of three elements:

Markings documented on the cylinders and the other elements show that each was produced by a different Chinese manufacturer, each of which advertises on its respective website that those items are intended for use as part of hydrogen fuel cell systems for UAVs. CAR reviewed the associated transfer documentation packed with the components, which also clearly indicated the intended use in UAVs. Crucially, CAR did not document fuel cell stack modules in the Mokha seizure. Such modules transform the hydrogen gas into electric power and are essential for the effective deployment of this technology. It is unclear why the stack modules were not included in the cargo.

CAR believes that the mislabelling of the gas tanks as ‘oxygen cylinders’ is part of a deliberate attempt to conceal the content and origin of the sensitive cargo, should it have been recovered without its accompanying documentation.

UAVs and other uncrewed systems powered by hydrogen are a relatively novel technology. Although some manufacturers are now advertising this as an available option, every UAV that CAR has documented—not just in Yemen but across its global operations—was powered either by lithium-ion batteries or small gasoline or diesel engines.

In 2022, United Arab Emirates authorities recovered a similar carbon-fibre gas tank from the debris of a ballistic missile launched at  Dubai International Airport , but in this case the Houthis had likely employed the tanks as part of the pressurised gas system within the weapon system, a use that is common in both aircrafts and guided weapons. CAR does not consider it likely that the Houthis intended the compressed hydrogen gas recovered in Mokha to be used for such purposes, an assessment supported in particular by the information contained in the associated transfer documentation.

While hydrogen gas cylinders could conceivably service legitimate civilian purposes, based on the findings detailed above, CAR assesses that the recovered hydrogen gas tanks from the Mokha seizure were intended for use by the Houthis to power uncrewed systems.

CAR’s documentation in Yemen is the first public disclosure of what could, if successfully integrated, represent a significant evolution of the current threat capabilities of the Houthis, who have been subject to a targeted United Nations  arms embargo  since February 2022 and on 4 March 2025 were formally designated as a  Foreign Terrorist Organization  by the United States.

CAR’s documentation in Yemen is the first public disclosure of what could represent a significant evolution of the current threat capabilities of the Houthis

In the context of international counter-terrorism efforts to restrict and prevent non-state armed groups from developing ever more threatening uncrewed systems, this finding represents an alarming evolution. Motors powered by hydrogen fuel cells are significantly quieter than gasoline and diesel engines, enabling greater stealth. Hydrogen-powered UAVs also have reportedly at least  three times the range  of those powered by traditional lithium batteries. This would greatly extend the potential threat posed by the Houthis, who are already capable of attacking sites in neighbouring countries, as well as maritime targets in regional waters.

While cost, safety, and technical barriers may prevent other non-state armed actors from attempting to adopt hydrogen fuel as a power source for uncrewed systems, this discovery demonstrates that well-resourced groups like the Houthis may be actively looking to overcome these restrictions.

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•  Evolution of UAVs employed by Houthi forces in Yemen : This dispatch tracks the evolution of Houthi unmanned aerial vehicles (UAVs), which have become increasingly lethal and powerful. CAR finds that the Yemeni group is able to domestically manufacture some components while procuring more sophisticated electronic items from foreign supply networks.

Established in 2011, Conflict Armament Research generates unique evidence on weapon supplies into armed conflicts in order to inform and support effective weapon management and control.

CAR field investigation teams document illicit weapons, ammunition, and related materiel in conflict-affected locations and trace their supply sources. The teams inspect weapons in a variety of situations—whether recovered by state security forces, surrendered at the cessation of hostilities, cached, or held by insurgent forces. They document all items photographically, date and geo-reference the documentation sites, and incorporate contextual interview data gathered from the forces in control of the items at the time of documentation.

CAR occasionally uses information and photographs from social media as background information but does not base its investigations on them, since the provenance of such data is often difficult to verify. Moreover, open-source information does not always provide the detailed physical elements—notably external and internal markings required to trace weapons and ammunition.

For more information on CAR's methodology, go to www.conflictarm.com