LONDON — The whole idea of special operations insertion craft is to move about unseen and undetected. But here at the DSEI defense exhibition, a number of spec ops craft and products were on display. Two of the more interesting were swimmer delivery vehicles (SDV) that carry eight to 10 divers, speed along on the water’s surface at better than 30 knots, ballast down in a semi-submerged mode, then completely submerge.
The prosaically named SEAL Carrier from the Swedish-UK firm JFD was on view, reminiscent of a miniature version of Jules Verne’s Nautilus. The 10.45-meter-long craft, weighing empty about four and a half tons when empty, can carry a crew of two plus six divers.
"Two of these craft are operational with the Swedish Navy," said Anders Magnerfelt, JFD’s director of operations, said. "A few other countries" also operate the SDV, he added, but he declined to be more specific.
The SEAL Carrier can be air-dropped onto the ocean, then run on diesels for up to 150 nautical miles — double that distance when a secondary fuel bag is fitted. To avoid detection, the craft can ballast down to semi-submerged mode, leaving the heads of the divers, a sensor mast and an air snort above the water. In this mode, the craft can move, powered by either the diesel or electric motors, at speeds between four and six knots. Semi-submerged range on the diesels motor is as much as 150 nautical miles, and it's or about 15 nautical miles on electric.
Submerged, the craft has a top speed of five knots, with a range of about 15 nautical miles at three knots.
Divers plug into the craft's onboard breathing system. Operating depth is limited to between 40 and 50 meters — restricted only by limitations of the divers, Magnerfelt said.
The craft can also be mounted on submarines, generally aft of the fin.
A similar craft, but from the other side of the world, was presented at the show. Vogo, a South Korean firm from Samcheok-si, offered its SDV 1000W, a 12-meter-long craft able to carry 10 divers.
"The purpose is pretty much the same — infiltration," naval architect Jay Lim, Vogo's executive director, said.
The SDV 1000W features an enclosed control station forward, reducing environmental wear and tear on the crew, but shares many characteristics with the SEAL Carrier. Air-droppable from a C-130 or C-17 aircraft, the SDV 1000W is powered by a diesel on the servicesurface, and uses lithium-polymer batteries for submerged electric propulsion.
The Korean craft can hit surface speeds of 35 knots and move at something better than six knots submerged, Lim said, although it is not fitted with a snort.
"Our vessel is faster, can carry more payload and has greater underwater accuracy," Lim claimed.
One Korean difference between operating practices elsewhere, Lim explained, was that the craft's two-man operating crew is also part of the spec ops team. "They all leave the vehicle to carry out the mission," he said.
The prototype SDV 1000W was completed in 2009, Lim said, and the type has been in operational use.
Pointing to the range of undersea products offered by Vogo, including the SDV 1000W, Lim made one more prediction, without elaborating: "We’re working on a new product that we’ll show maybe in 2017 that could make these vessels obsolete.," he said with a smile.
Email: ccavas@defensenews.com
Twitter: @CavasShips
