The US Navy wants a robotic crawler to eliminate the most dangerous underwater threat: sea mines

• Finding and disposing of mines lurking on the sea floor is dangerous and difficult work.
• The US Navy wants robotic crawlers capable of descending to nearly 2,000 feet underwater to do this.
• The service’s request goes well beyond existing tech built by contractors like Textron.

One of the nastiest threats in naval warfare are mines. Crude, cheap and packed with explosives, bottom mines lurk on the seabed like aquatic IEDs, where they are harder to detect and sweep than floating mines.

That has been the tough and deadly work of ships, helicopter-towed sleds and specially trained techs. Now the US Navy has a new vision: a robotic crawler. And with the growing threat of sabotage to underwater cables and pipelines, an automated crawler could potentially be useful in protecting maritime infrastructure.

The Navy envisions a small unmanned vehicle that weighs no more than 150 pounds, according to a December Navy Small Business Innovation Research (SBIR) solicitation which seeks ideas from industry. The “Maritime Expeditionary Response Crawler” would be fitted with a variety of payloads, including short-range sensors, manipulator arms, and equipment to disrupt mines and other underwater explosives.

The crawler would both be autonomous and controlled by human operators via a tether. The vehicle “must be capable of conducting operations in water depths over 600 meters [1,968 feet] while also capable of transit on the ocean surface for a distance of at least two nautical miles to a georeferenced point where it can autonomously submerge to the seabed,” the SBIR specified.

The crawler would be a standoff system that allows human operators to remain a safe distance from any mines. Once the crawler dives to the seabed, it would release a tethered buoy with a radio transmitter connected to the mothership.

The dull, dirty and dangerous task of sweeping for mines would be autonomous. “Supervisory autonomy to reduce cognitive burden to the operator is desired,” the SBIR said. However, operators would have “supervisory control and situational awareness for detection, reacquisition, and render safe or neutralization tasks to enable clearance of naval mines and other underwater explosive-laden threats.”

The crawler must be capable of operating “in different sediment and seabed types (e.g., rocky, flat sand, silt, etc.) and must be stable on the seabed in dynamic sea states and currents.” Though bottom mines are typically laid in shallow waters, the SBIR only mentions an ocean environment rather than rivers.

Naval mines have always had an aura of being sneaky and malicious weapons. They date back to medieval China, though David Bushnell — an 18th-century American inventor — is credited with inventing the modern variety during the American Revolution. Historically, a common variety has been moored mines that are attached by cable to an anchor on the seabed, which allows the mine to float at a specified depth. The crudest form is a contact mine that detonates when it touches a passing vessel — usually any kind of vessel, military or civilian, which is what makes mining so indiscriminate.

Bottom mines are even sneakier. They are “influence” weapons, laying quietly on the seafloor until triggered by a ship’s magnetic field, the acoustic signature of its propellers, or the pressure the vessel generates in the water. While moored mines can also be fitted with these actuators, bottom mines are harder to detect.

In addition to being harder to detect via sonar amid the clutter on the sea floor, bottom mines also tend to have larger explosive charges than moored weapons. Because their explosive energy has to travel upwards to reach a ship or submarine above, “bottom mines tend to work in relatively shallow water (less than 164 feet),” according to the Strauss Center for International Security.

Several nations field air-launched or submarine-launched bottom mines, including Russia’s MDM and the US Navy’s Quickstrike, and China’s Chen series. Significantly, Chinese military journals suggest a preference for bottom mines. Based on Soviet minelaying experience in World War II, Chinese experts concluded that anchored mines “have low reliability due to current and waves,” according to American defense analyst Lyle Goldstein. “By contrast, bottom mines are said to be more reliable, harder to find, and much more difficult to sweep.”

Navies have already turned to robots as a cheaper and safer alternative to crewed minesweepers. The US Navy, for example, has just awarded a $106 million contract to Textron for semi-autonomous boats to clear mines. The SeaFox, an expendable torpedo-like drone made by the German contractor Atlas Elektronik, was deployed by the Royal Navy as far back as 2001.

But a robotic underwater crawler is something else. The US Navy SBIR only mentions mines and underwater explosives as the goal of the robotic crawler project. But such a vehicle would seem useful against sabotage of undersea cables and pipelines. Nations worry about the vulnerability of undersea infrastructure and the difficulty of protecting facilities that might be 300 feet below the surface.

Russia and China have allegedly employed ships to drag anchors along the ocean floor, cutting telecommunications cables. The most serious underwater incident was in September 2022, when explosions damaged the Nord Stream 1 and Nord Stream 2 underwater pipelines, which transported natural gas from Russia — via the Baltic Sea — to Germany, where it was distributed to Western Europe.

There are various theories as to the Nord Stream culprit, but these incidents have spurred NATO to deploy surveillance drones and sensors to protect underwater infrastructure in the Baltic and Mediterranean Seas. A robot minesweeping crawler would be the next logical step.

Michael Peck is a defense writer whose work has appeared in Forbes, Defense News, Foreign Policy magazine, and other publications. He holds an MA in political science from Rutgers Univ. Follow him on Twitter and LinkedIn.