US Navy launches Blueye X3 tethered drone from torpedo tube for submerged submarine inspections.

Sailors aboard the Los Angeles-class fast-attack submarine USS Pasadena (SSN 752) successfully launched a Blueye X3 remotely operated vehicle (ROV) directly through a 533 mm torpedo tube while submerged in Norfolk, Virginia. The integration bypassed expensive conventional hull modifications by utilizing a 3D-printed waterproof housing and low-voltage wiring harness built by the Shore Intermediate Maintenance Activity. This engineering approach demonstrates a low-cost method for conducting real-time underwater hull and infrastructure inspections without risking diver safety.

The test utilized an 8.6 kg Blueye X3 ROV deployed through standard torpedo interfaces at a material cost of less than $1,000, avoiding a costly $200,000 Fiber Optic Penetrator alteration. This initiative establishes a repeatable capability for Submarine Force Atlantic to conduct localized subsea sensor operations while maintaining strict adherence to standard submarine operating procedures.

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The U.S. Navy launched a tethered Blueye X3 through USS Pasadena’s torpedo tube to test underwater inspections from a submerged submarine while keeping sailors inside the pressure hull. (Picture source: US Navy)

On August 24, 2026, the U.S. Navy launched a Blueye X3 tethered remotely operated vehicle (ROV) through a 533 mm torpedo tube aboard the Los Angeles-class USS Pasadena (SSN-752) in Norfolk, Virginia, testing a new method for conducting underwater inspection while the attack submarine remains submerged. The Blueye X3 measures 485 x 257 x 354 mm, weighs 8.6 kg, is rated to a depth of 305 m and uses four 350 W thrusters, with a normal speed of 1.5 m/s and up to 300 m of tether. Unlike an autonomous UUV, a ROV requires continuous communications for piloting and live video, making the flooded torpedo tube's electrical connection the central integration problem for the U.S. Navy. Personnel from the Shore Intermediate Maintenance Activity (SIMA) solved this with a 3D-printed waterproof housing, low-voltage wiring, and a dedicated harness, reducing additional materials and labor costs to less than $1,000, as the Submarine Force Atlantic (SFA) already owned the ROV, compared with roughly $200,000 for the Fiber Optic Penetrator (FOP) alteration initially considered.

The USS Pasadena is a Flight III Los Angeles-class, or 688i, submarine commissioned on February 11, 1989, 37 years before the test. The 110.3 m-long submarine displaces 6,204 tons full, uses an S6G pressurized-water reactor and two steam turbines producing 33,500 shp, and has an official submerged speed exceeding 25 knots. Its four 533 mm bow torpedo tubes normally carry heavyweight weapons such as the Mk 48/Mk 48 ADCAP torpedoes, while 12 separate vertical launch tubes accommodate Tomahawk missiles. The Blueye X3 test therefore converted an existing weapon interface into a route for deploying and recovering a robotic sensor without requiring an external ROV hangar or another permanent hull modification.

The difference between a Blueye X3 and the payloads normally handled by the tube is substantial. A Mk 48 torpedo is 5.8 m long, 530 mm in diameter, and weighs 1,676 kg, including a 293 kg warhead, compared with 485 mm and 8.6 kg for the X3, meaning the ROV has only 0.51% of the torpedo's mass and less than one-tenth of its length. The Mk 48 uses an Otto Fuel II-powered swash-plate piston engine driving a pump-jet and can receive commands through a guidance wire before relying on its onboard acoustic equipment for target acquisition and attack. The X3 instead requires continuous two-way communications for remote piloting and video transmission. This created a different integration problem for the USS Pasadena, which consequently had to launch the ROV while keeping the cable routed through the tube, protecting electrical connections during flooding and maintaining enough data throughput for simultaneous control and live imagery.

That communications path was the principal hardware modification. SIMA Additive Manufacturing produced a waterproof housing from Rigid 10K resin using a Formlabs Form 4L stereolithography printer, while the SIMA 2M Shop installed standard low-voltage wiring and integrated the assembly with the X3 tether. A second harness outside the tube maintained the connection through several attachment points to the Blueye controller, with Blueye Robotics assisting at the controller interface and NUWC Division Keyport supporting shipboard integration. The resulting path ran from the submerged X3 through its tether to the waterproof housing, then through low-voltage wiring and the external harness to the operator's controller. The ROV itself consequently required limited alteration; most of the engineering effort was concentrated at the boundary between the flooded torpedo tube and the submarine's dry internal spaces.

The economic difference between the two integration approaches is equally measurable. The initially considered Fiber Optic Penetrator temporary alteration costs roughly $200,000 per submarine, compared with less than $1,000 in materials and labor for the demonstrated USS Pasadena's arrangement. At the $1,000 ceiling, this new submarine-side integration therefore costs less than 0.5% as much, meaning the alternative was more than 200 times less expensive. The comparison excludes the X3 purchase price because Submarine Force Atlantic already owned the vehicle, as well as future certification, spares, maintenance, replacement ROVs, and training. The U.S. Navy is nevertheless moving beyond a one-time engineering evolution by developing an ROV Personnel Qualification Standard card while retaining existing torpedo-tube operating requirements.

The X3's characteristics also define what the Green Remora project can realistically provide. The initiative began under Vice Adm. Rob Gaucher to improve the equipment available to submarine divers conducting hull-security sweeps and external equipment inspections, and Submarine Force Atlantic acquired two Blueye ROVs before testing this torpedo-tube deployment. The X3's 305 m depth rating substantially exceeds the 3.8 m depth visible during one portion of the Pasadena demonstration, while its 300 m maximum commercial tether length establishes a theoretical physical connection considerably longer than the distance demonstrated publicly. Its normal speed of 1.5 m/s, 1080p camera, and 3,300-lumen lighting favor close inspection rather than wide-area reconnaissance. However, the U.S. Navy has not released the test's maximum distance, depth, endurance, tether length, or launch-and-recovery time, so the demonstrated operational radius remains unknown.

The operational value subsequently lies in replacing some diver tasks with a remotely controlled sensor that can remain under continuous human control. An operator can stop, reverse and reposition the X3 around a hull appendage, suspected attached object, obstruction or seabed contact while receiving live imagery, without putting a sailor at risk into the water. The trade-off is the tether: even at a maximum commercial length of 300 m, it limits radius and creates potential fouling and entanglement problems around the hull, seabed, and underwater structures. This consequently makes the X3 better suited to localized inspection of the submarine and nearby objects than the longer-range reconnaissance missions assigned to autonomous UUVs.

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Written by Jérôme Brahy

Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, South Korea, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.