Page 9: of Marine Technology Magazine (Jul/Aug 2026)

rine vulnerable to detection by surface and endurance would be a signi? cant League’s Sea-Air-Space conference or air platforms that could be prowling achievement. General Atomics has done in April of this year, the G-Ray incor- above. Fuel cells solve this problem by just that with the G-Ray, a blended-wing porates a hybrid battery-hydrogen fuel enabling a submarine to generate elec- underwater glider that minimizes en- cell system that enables extended endur- tricity without combustion and without ergy consumption through its high lift- ance and range on the order of months, atmospheric oxygen. Stored hydrogen to-drag ratio and buoyancy-driven pro- with potential for even longer durations. and liquid oxygen feed proton exchange pulsion. Recently unveiled at the Navy Rather than storing compressed hydro- membrane (PEM) fuel cells, producing electricity silently, with water and heat as the byproducts. The result is stealthy, fully submerged power production, and an endurance measured in weeks rather than days. The same characteristics that make fuel cells attractive for conven- tional submarines- quiet operation, high ef? ciency, and extended submerged en- durance - are now driving their adoption in autonomous underwater vehicles.

Unlike Li-ion batteries, which store a ? nite amount of electrical energy that is gradually depleted during a mission, fuel cells generate electricity for as long as reactants remain available. Although they are generally larger, more complex, and more expensive than battery-only solutions, fuel cells can provide several times the usable energy of a comparably sized and weighted battery system, and can extend underwater endurance from hours or days to weeks, or even months.

In addition to higher energy density, fuel cells do not self-discharge during periods of inactivity, which could en- able missions involving prepositioned systems in forward areas. And the high- er endurance offered by such systems could reduce the total cost of sustain- ing an autonomous undersea presence.

Maintaining that presence would re- quire operating a ? eet of platforms on a rotational basis - deploying, patrolling, recovering, replenishing onboard ener- gy stores, and performing maintenance.

If vehicles can remain on station for longer periods, and their energy systems can be replenished in minutes rather than hours, operators may require fewer platforms to sustain the same level of persistence and area coverage.

The endurance bene? ts of fuel cells for conventionally propelled AUVs are substantial, but combining them with an unconventional AUV whose unique design already provides extended range www.marinetechnologynews.com 9

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