I just love how these Popular Mechanix type articles gloss over minor issues like where does the power for this come from?
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According to the article, rechargeable batteries. They can get off five to six shots on one charge. The system is being designed for a drone with a 3000 pound payload capacity.
And it can probably recharge with a generator attached to its turbine engine. Anything powered by a jet engine potentially has a lot of electricity available.