Machine Design
U. S. Navy sub launches drone while underwater

U. S. Navy sub launches drone while underwater

The Navy recently launched an all-electric, hydrogen-fuel-cell-powered UAV from a submerged submarine, opening the way for submarines to expand their surveillance capabilities and include land-based targets. The UAV, an XFC, was folded and packed inside a Sea Robin launcher, which fits in an otherwise empty Tomahawk launch canister, a subsystem submarine sailors are familiar with. The Sea Robin was fired from a torpedo tube onboard the USS Providence, then surfaced, where it appeared as a spar buoy. The XFC then left the canister, deployed its X-wings and flew for several hours, beaming live video back to the USS Providence. It landed at a Navy base in the Bahamas. The drone can fly for up to 6 hr and generate enough electricity to keep it flying and power payloads.

The 16.5-lb XFC (with electro-optic camera payload) has a loiter speed of 30 knots and a top speed of 52 knots. The drone launches using an electronically assisted takeoff (ETO) subsystem attached to its nose. It consists of a battery-powered motor running a pair of counterrotating propellers. During launch, the batteries use all of their charge in just a few seconds to power the motor as the props pull the XFC out of its cargo tube and take it to a safe flying altitude. Once the aircraft is at altitude and its wings unfold, the ETO is jettisoned and the fuel-cell engine activated. ETO lets the drone get airborne without using traditional launch-assist devices such as rockets and explosive charges.


U. S. Navy Research Laboratory

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