SECRET DELIVERY: Advanced SEAL Delivery System (ASDS)

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Since 07-13-05

A mini-sub that can transport up to 16 Navy SEALS with stealth and speed, the ASDS is the first of its kind to provide a comfortable, and perhaps more importantly, dry ride for the elite SOCOM forces.
Divers outside a SSGN with a ASDS in the background. (Courtesy of

By Richard R. Burgess
Managing Editor, Sea Power

If you're a Navy SEAL, you've probably seen the toughest, most extreme conditions and still managed to get the job done. But the most seasoned SEAL wouldn't object to a dry and comfortable underwater ride as opposed to a cold and wet one. The Advanced SEAL Delivery System (ASDS) is a mini submarine being developed by Northrop Grumman to covertly transport special operations forces from a submerged submarine to a shoreline or harbor and back. And with its Dry Deck Shelter (DSS), the ASDS can provide waterless medium-range transportation for elite Navy SEALs.

"The capability is greater than we ever expected," said a former government official familiar with the ASDS. "There is no substitute for this capability," he said. "It is both covert and persistent."

Dry Ride

The first ASDS became operational from its base at Pearl Harbor, Hawaii, in 2003 and last year completed its first deployment onboard an attack submarine, the USS Greeneville, to the Indian Ocean and Persian Gulf as a unit of Expeditionary Strike Group One. "It has been used operationally to great advantage and has proven successful," the official said.

Transportable by C-5 Galaxy and C-17 Globemaster, the 60-ton ASDS is capable of docking over the hatch of a submarine, bringing aboard 16 SEALs and their equipment, and delivering them to the insertion point. The SEALs would arrive dry and relatively comfortable and rested for their mission. The ASDS represents a great improvement over the Swimmer Delivery Vehicle, a 22-foot-long submersible in which SEALs must wear SCUBA gear, arriving at the insertion point wet and tired.

The first ASDS has yet to be joined by other units, as the program has been slowed by escalating costs and technical problems. A Congressional Budget Office (CBO) study issued in 2003 cited two major technical problems: noisy propellers and silver-zinc batteries that depleted more quickly than planned.

Port side view of ASDS Advanced SEAL Delivery System (ASDS) underway, off the coast of Pearl Harbor, Hawaii. (Courtesy of

A new propeller made of composite material has been developed to rectify the noise problem. Development is under way on lithium-ion batteries to replace the silver-zinc batteries and enable the electrical system to meet the Navy's requirements. Yardney Technical Products of Pawcatuck, Conn., has been awarded a $44 million contract modification to provide four lithium-ion batteries for the ASDS program by May 2009.

One of a Kind

The first ASDS is one-of-a-kind design by a company division that had never built a submarine. He attributed the increased cost in part on flawed decision-making in its procurement. "ASDS is really a little sub, but it wasn't built by a submarine builder," he said. The ASDS, he noted, uses a bolted hull design rather than the welded hull used extensively in sub production. The source suggested that the industrial experience of the submarine industry be tapped to improve the efficiency of production of ASDS. He also recommended that the first ASDS be considered a proof-of-concept vehicle, and that follow-on units incorporate lessons learned and be designed for serial production. He sees movement on the part of the builder to take advantage of submarine production experience.

"To be effective, any capability has to be available," the former official said. "When you have one, it's not [always] available." With only one unit, maintenance and other down time makes it unavailable, and it cannot be two places at once. He believes the right number of ASDS units required is "probably around eight."


The Navy has stated a requirement for six units, but that was established before it decided to convert four Ohio-class ballistic-missile submarines to guided-missile submarines (SSGNs) with the additional mission of support of special operations forces. Each of the SSGNs will be capable of carrying two ASDS units.

Two Los Angeles-class attack submarines have been modified to deploy the ASDS, and the new Virginia-class attack submarine is being built with the inherent capability to deploy the mini-sub. Planners originally intended the two pilots for the ASDS include one submarine officer and one SEAL. So far, the first ASDS has been piloted by two submarine officers. With all its rough edges smoothed out, the ASDS will be a welcome alternative to the cold and wet rides of its predecessors, and has already made some important steps in helping Navy SEALs weather the extremes.
Crew 2
Passengers Up to 16 SEALs, depending on equipment
Length 65 ft.
Beam 6.75 ft.
Height 8.25 ft.
Dry Weight 55 tons
Range 125+ mi.
Speed 8+ knots
Propulsion 67 hp electric motor (Ag-Zn battery)
Diving Depth Classified
Masts 2 (Port - periscope, Starboard - Communication + GPS)
Sonar Forward Looking - detect natural/man-made obstacles, Side Looking - terrain & bottom mapping, mine detection