explainers

Ukraine’s super drones Whatever naval weapon was used to bomb the Crimean Bridge, we know remarkably little about it

Source: Meduza

Within a few hours of the July 17 attack on the Crimean Bridge, Russia’s National Antiterrorism Committee attributed the explosions to “two Ukrainian unmanned surface vehicles.” A source close to the Ukrainian Defense Ministry’s Main Intelligence Directorate, who spoke to Meduza on condition of anonymity, later confirmed this. Ever since, however, there’s been no additional proof that drones carried out the attack. We still don’t have even a leaked photograph of the weapons. There is nevertheless some circumstantial evidence to corroborate these reports: namely, videos and photos showing that the blasts hit the underside of the bridge’s roadway, as well as satellite imagery recorded a day earlier that captured six unknown vessels, five of which were headed east, roughly 75 kilometers (almost 47 miles) from Snake Island. When the satellite overhead photographed these ships, they were about 520 kilometers (almost 325 miles) away from the bridge. Beyond this limited available information, the various capacities of Ukraine’s known naval arsenal make it possible to draw a few conclusions.

Based on open sources alone, there was no evidence before July 17 that the Ukrainian military had naval drones powerful enough to damage the Crimean Bridge’s support pillars. It was assumed that Ukraine had various drones but that none of them had sufficient range or payload capacity to carry out this mission.

The Ukrainian Navy got its first drones from the United States in April 2022. In those shipments, Washington didn’t specify the drone model or number sent, identifying the weapons only as “unmanned coastal defense vessels.” Western experts have argued that these were probably Mantas T-12s, which the U.S. Navy also uses. The Mantas T-12, however, lacks the payload capacity needed to deliver the explosives that hit the Crimean Bridge on July 17.

Last fall, Ukraine started attacking Russia’s Black Sea Fleet bases in Sevastopol using drones of a new, unknown design. One of these weapons later washed up in Sevastopol Bay, where the Russian military captured it. Ukraine also showed off some of these drones during a crowdfunding campaign to form “the world’s first naval fleet of drones.” Kyiv announced that the kamikaze drones comprising this fleet carry payloads weighing up to 200 kilograms (440 pounds), have a range of 800 kilometers (almost 500 miles), and weigh about a metric ton (2,205 pounds) on average. It is impossible to verify these claims, of course.

Western experts who studied photographs of these newer drones have concluded that they were made using civilian components except for the contact fuse, which resembles a Soviet high-explosive bomb. Images from Sevastopol Bay indicate that these vessels are equipped with Starlink satellite communication systems, enabling remote “manual” control, making engine capacity and fuel efficiency their only range limitations. Experts believe these drones use a three-cylinder Rotax gasoline engine — the same motor that comes in Sea-Doo jet skis. 

At a watercraft cruising speed of 56 kilometers (35 miles) per hour, the Rotax 3 engine burns through 30 liters (8 gallons) of gasoline — about half a liter for every kilometer (less than a quarter of a gallon for every mile). 

Given the total distance the drones in the satellite imagery would have needed to travel — roughly 600 kilometers (373 miles) from Snake Island to where they were photographed and then all the way to the Crimean Bridge — they would have consumed fuel weighing roughly 240 kilograms (530 pounds). The engine, the fuel system, and the payload add another 300 or so kilograms (660 pounds), which leaves just 460 kilograms (about 1,000 pounds) for the rest of the ship’s equipment and its entire body. 

Another reason to doubt that the naval drones Ukraine unveiled last fall were used to strike the Crimean Bridge on July 17 is the fact that the fuel efficiency calculated above is standard for jet skis, which weigh less than half what Ukraine said its naval drones come to.

At the same time, on at least three occasions, the Ukrainian military has indicated that it possesses exceptionally long-range naval drones. In November 2022, the pro-Kremlin Telegram channel Mash reported that one of these longer-range drones attacked the Sheskharis oil harbor in Novorossiysk. More recently, in May and June 2023, an apparently new kind of Ukrainian drone hit two reconnaissance ships from Russia’s Black Sea Fleet in open waters, a few hundred kilometers from Snake Island. (The attack reportedly failed.)

At the same time, it’s impossible to rule out that Ukraine simply acquired more powerful and efficient motors for the drones it unveiled last November.

Why couldn’t Russia protect the Crimean Bridge?

While the pro-Kremlin Russian media has circulated exotic stories, like speculation that the attack may have utilized REMUS 6000 British autonomous underwater vehicles, no shipments of these drones have been reported. Also, they aren’t equipped with the communications systems needed for reliable “manual” control, and they’re too light to deliver enough explosives to inflict the damage that was done to the Crimean Bridge.

The more likely explanation for Russia’s failure to protect its bridge to Crimea is that the military was expecting an airborne attack. This appears to be the case, despite Russia’s own experience in the Odesa region, where the Navy finally disabled a bridge across the Dniester Estuary in February 2023 after months of heavier rocket attacks failed to cause enough damage to the target. 

Going forward, Russia’s Navy will likely reinforce its defenses around the Crimean Bridge, as it already did around Sevastopol. This will probably include floating barriers along the entire bridge and Coast Guard ships placed on constant duty, armed with higher caliber machine guns and possibly more advanced monitoring equipment. Whatever Moscow does in the region, however, long-range early detection against such small vessels will remain difficult, and the danger of future attacks still looms.