June 10, 2021: In April 2021 Chinese media announced that an American robotic vessel was hauled in by Chinese fishermen in the Yellow Sea between China and Korea. China described the three-meter (ten foot) long device as something used to spy on China. What China described was the surface component of the American Wave Glider SV3 AUV (autonomous unmanned vehicle) which also contains an underwater component, connected to the surface AUV float by an eight-meter (25 foot) cable that transmits power and data from the float to the underwater component, and data collected by the underwater component to the AUV float that contains solar panels and communications equipment to transmit position back to a land base via a satellite phone. This enables a surface ship to get close enough to use a cellphone cell tower to collect accumulated data from the Wave Rider and send new instructions about where Wave Rider is to search. The surface component weighs 90 kg (198 pounds) while the underwater portion weighs 155 kg (340 pounds).

Wave Rider has been around since 2007 as a commercial product. There have been two upgrades, the latest in 2017, which made Wave Rider able to operate rough seas and farther north and south than previous models. Wave Rider can be used individually or in small groups to monitor ocean conditions as well as weather. Individual Wave Riders stay at sea for up to six months, or more, before being hauled aboard a ship for repairs, maintenance or upgrades. Basic Wave Riders cost about $300,000. That can increase by a third or more with some of the more expensive sensors available. Wave Rider data can be used for military purposes, but that is secondary to the task of monitoring the state of oceans in general. In 2012-2013 the record for Wave Rider duration was one that remained at sea for a year and travelled 14,000 kilometers from central California to northeastern Australia. Normally single or groups of Wave Riders monitor one portion of the ocean.

For over a decade the waters of the western Pacific have been increasingly populated by UUVs (Unmanned Undersea Vehicle) set loose to collect technical data on the water all the way from the surface to the sea bottom. Increasingly these UUVs are being caught by fishing nets by accident or seized by warships on purpose to make a political point or, eventually, interfere with legal data collection that is nevertheless very useful in submarine operations. The UUVs have been getting cheaper, more capable and proliferating. After a 2016 incident with China the U.S. pointed out that a UUV Chinese fishermen had found was using commercially available technology and was worth about $150,000. Faced with a “grand theft droid” charge China agreed to return the AUV.

This is the first time China has seized a Wave Rider and despite initially calling it an espionage device will probably return it as well because China can also purchase Wave Rider for its own oceanographic research.

Until the 2016 incident with China most of the Wave Rider and UUV incidents were accidents and curiosities, not diplomatic showdowns. For example, later in 2016, Filipino fishermen in the South China Sea caught an American AUVs in their nets. These torpedo-like devices are clearly marked as to what they are and the American embassy will send someone to pick them up if found. These AUVs are silent, very small, and able to operate on their own for up to a year. The first models were two meters (six feet) long, weighed 59 kg (130 pounds) and operated completely on their own, collecting valuable information about underwater “weather”. What this AUV does is automatically move slowly (30-70 kilometers a day) underwater, collecting data on salinity and temperature and transmitting back via a satellite link every hour or so as the AUV briefly reaches the surface. This data improves the effectiveness of sonars used by friendly forces, making it easier to detect and track enemy submarines. That’s because the speed of sound travelling through water varies according to the temperature and salinity of the water. Having more precise data on salinity and temperature in a large body of water makes your underwater sensors (sonar, which detects sound to determine what is out there) more accurate. This data can also assist submarines in better avoiding detection. The first of these navy AUVs could dive as far down as 200 meters (620 feet) and later models were able to go down to 1,000 meters or more.

The Wave Rider is simply an advanced design based on the earlier underwater only AUVs. Wave Rider and the earlier UUVs use a unique form of propulsion. They have wings, and a small pump that fills and empties a chamber. This changes its buoyancy, causing it to glide down, then back up. This maneuver moves the UUV forward. Equipped with GPS and a navigation and communications computer, the UUV is programmed (or instructed via the sat link) to monitor a particular area. The small pump uses less electricity than a propeller moving the UUV at the same speed. As a result of this all UUVs UAVs can remain at sea for up to a year on one battery charge. Before the battery runs out the owner has to direct the UAV and a ship to a rendezvous where the AUV will remain on the surface and the ship will haul it aboard, replace the battery and perform any other needed maintenance.

Wave Rider uses the surface component to carry solar panels to recharge the battery and power more sensors. Small UUV maintenance detachments (of two or three sailors) can be flown to a ship that is close enough to make the rendezvous. In some cases, you can direct the UUV to move close to land, which makes it even easier to find a boat to go out and get the AUV. These UUVs can be launched from ships or shore. In 2009 an UUV of this type crossed the Atlantic on its own, as part of a civilian research project. A few years later a Wave Rider travelled even farther and crossed the Pacific.

The U.S. Navy currently has over 2000 of these UUVs and about twenty Wave Riders in service or on order and plans to keep increasing this robotic UUV fleet as long as they keep demonstrating they can do the job. This is part of a plan to have UUVs replace many of the ocean survey ships currently used for this kind of work. The survey ships take temperature and salinity readings from instruments deployed from the ship as well as a global network of several thousand research buoys. Unlike the survey ships the UUVs could be deployed in areas where hostile subs are believed to be operating, and be kept at it as long as needed. If successful in regular use, larger versions are planned, equipped with more sensors and longer duration.

The U.S. Navy apparently has a lot of these UUVs operating in the South China Sea because of the disputes everyone is having with China over Chinese claims to nearly all the South China Sea. It’s not just UUVs Filipino fishermen come across. In 2015 and 2013 fishermen found a Chukar target drone. The target drone had a curious history because it landed intact in late 2012 and then drifted over 2,000 kilometers from Guam until it reached the Philippines. The Chukar is designed to float so that it can be recovered and reused.