October 20, 2013: The U.S. Navy has announced that is buying some smaller MK18 mine clearing UUVs (Unmanned Underwater Vehicle) to be used until the larger Knifefish UUV is ready for service. Both UUVs are mainly for use on the LCS (3,000 ton Littoral Combat Ships) for mine sweeping. The new Knifefish UUV is the size of a torpedo. It weighs 770 kg and is 5.8 meters (19 feet) long and 533mm (21 inches) in diameter and won't be ready for service until 2017, at the soonest.

The MK18 UUVs are based on the commercial Remus 100 and 600 UUVs which have long been used commercially for underwater reconnaissance. They have also been bought by navies to search for mines. The U.S. Navy has been using the smaller (26.4 kg/80 pound), Remus 100s for this in Iraq, and the Remus design is highly regarded by military and commercial users. The navy calls the Remus 100 the Mk18 Mod 1 Swordfish.

The Mk18 Mod 2 Kingfish is based on the Remus 600 and is to be in service by 2015. This is a 240 kg (528 pound) UUV that also looks like a small torpedo and is basically a larger version of the Remus 100 (a 37 kg vehicle that is 1.6 meters long and 190mm in diameter). Remus 600 is 3.25 meters (10 feet) long and 320mm in diameter. Carrying a side scanning sonar, and other sensors, a Remus 600 can stay under water for more than 24 hours, traveling at a cruising speed of 5.4 kilometers an hour (top speed is nearly twice that). The UUV can operate up to 100 kilometers from its operator and dive to 600 meters (1900 feet). The UUV keeps costs down by using GPS, in addition to inertial guidance. The UUV surfaces every hour or two to get a GPS fix and then goes back to doing what it was programmed to do.

Both Remus models were designed mainly for civilian applications (inspecting underwater facilities, pollution monitoring, and underwater survey or search). The “100” and “600” designations come from the maximum depth (in meters) each vehicle can operate at. Remus 100 entered commercial service in 2001, and the more powerful Remus 600 in 2005. Both were quickly adopted for similar military and police applications, like searching for mines or other terrorist activities. Belgium, Australia, and New Zealand also used Remus 100, and over a hundred are in use. This success led to the development of the larger Remus 600, which is used by Britain and the U.S. navies. Depending on sensors carried, each Remus 600 costs $500,000-1,000,000. The Knifefish will probably be a lot more expensive, larger, and have more capabilities. Both Remus models are also widely used by commercial firms and researchers and both remain in production.