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Advanced SEAL Delivery System
USS Greeneville (SSN-772) with the ASDS attached
USS Greeneville with the ASDS attached
Class overview
Name: Advanced SEAL Delivery System (ASDS)
Builders: Northrop Grumman Electronics Sensors and Systems Division, Oceanic Systems subdivision
Operators:  United States Navy
Built: 1996–2000
In commission: July 2003 – November 2008
Planned: 6
Completed: 1
Cancelled: 5
Lost: 1
General characteristics
Type: Submersible
Displacement: 60 long tons (61 t)
Length: 65 ft (20 m) o/a
Beam: 6 ft 9 in (2.06 m)
Draft: 8 ft 3 in (2.51 m)
Propulsion: 67 hp (50 kW) electric motor
silver–zinc battery
single propeller
Speed: 8 knots (15 km/h; 9.2 mph)
Range: 125 nmi (232 km)
Test depth: "Classified"
Troops: 16 SEALs
Crew: 2
Sensors and
processing systems:
Forward- and side-looking sonar

Advanced SEAL Delivery System (ASDS) was a midget submarine operated by the United States Navy and United States Special Operations Command designed to provide stealthy submerged transportation for special operations forces (primarily United States Navy SEALs) from the decks of nuclear submarines for primary use as an insertion platform for covert and clandestine operations. The program was abandoned after the only prototype example of the class was damaged beyond economic repair in an accidental fire.


ASDS was conceived to address the need for stealthy long-range insertion of special operations forces on covert or clandestine missions. Previous mini-subs were of the wet variety, exposing combat Swimmers to long, cold waits during transit that impeded combat readiness on arrival, and had limited blind underwater navigational capability.


The first study to define ASDS was performed in 1983. Competitive conceptual designs were developed in the late 1980s, the Request for Proposal was issued in 1993, and the first contract for design and construction of the ASDS was awarded in 1994.

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 vehicles.

The first ASDS became operational (completed testing and evaluation) from its base at Pearl Harbor, Hawaii, in 2003 and completed its first deployment on board an attack submarine, the USS Greeneville, to the Indian Ocean and Persian Gulf as a unit of Expeditionary Strike Group One. 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. 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.

In the end, however, technical, reliability, and cost issues have proven nearly insurmountable. Indeed, the ASDS has been cancelled for all intents and purposes; all that's left is an ASDS-1 improvement program to boost the performance of the existing sub and complete its operational testing. The Richmond Times-Dispatch notes that the ASDS mini-subs were originally supposed to cost $80 million each, but numerous problems with the first boat have ballooned its cost to $446 million so far (vendor and government facility costs inclusive). Instead of completing integration and entering service in 2000, testing continued and the first boat was officially delivered in July 2003. GlobalSecurity adds that the program was initially projected to cost $527 million (including delivery of all six boats), but it is now predicted to rise to more than $2 billion – significantly more than the $1.4 billion SSGN Tactical Trident conversion program to which it is related.

Funding was provided via Congressional line item to the Special Operations Command. The Navy Deep Submergence Office was selected as the technical design agent and program office. Technical assistance was provided by the Navy Experimental Dive Unit, Panama City; the Naval Special Warfare Command, Coronado;SEAL Delivery Vehicle Team 2, Norfolk; and the Special Operations Command (SOCOM) Special Operations and Acquisition Logistics (SOAL), Tampa.

Detailed design of the first ASDS was started in 1994, and hull construction undertaken in 1996, at a government estimated cost of US$160 million, to a low bid for the delivery of $69 million for the first ASDS (to include non-recurring design costs, fabrication, and testing), and subsequent copies for $25 million each. It was delivered for testing and evaluation in 2000 and cost US$300 million (vendor and program office costs inclusive) to develop. Subsequent submarines were estimated to cost $125 million (based on a 2001 estimate) a copy. Five more were planned, but production of the second system was placed on indefinite hold in December 2005 pending a production and cost review, and the resolution of many reliability problems (primarily wiring grounds).


In April 2006, the program for new submarines was canceled and Northrop Grumman notified of termination. The current submarine was still in development and use until damaged in a "serious fire" in November 2008. As of December 2008 the cause of the fire is yet to be determined.[1] Given the probable extent of fire and water damage (the mini-sub burned for six hours and remained sealed for two weeks) it was highly unlikely that the craft could be saved.[2]

On 24 July 2009, US Special Operations Command (USSOCOM) announced that the ASDS was not going to be repaired.[3]

Follow on programs

The Joint Multi-Mission Submersible follow-on program was abandoned in 2010 over cost concerns, in favor of Commercial off-the-shelf platforms.[4]

Critical Design Challenges

Power – The long range requirement strained the ability of existing battery technology.

Shock – Shock requirements for the vessel and for equipment mounted inside translated to "g" acceleration forces four times that currently specified for fleet nuclear submarines. No existing submarine equipment of any kind existed that survived the shock. Displays, computers, mountings, and life support equipment were expensive to re-engineer.

Host Needs – Weight, size, and center of gravity all were limited by what could be carried on the back of a 688 class submarine.

Life Support – The large number of passengers for the small submarine, the need for fully automated and self-controlling systems, and the long periods of submersion (days) presented serious challenges that could not be met with Commercial Off The Shelf (COTS) nor Government Off The Shelf (GOTS) systems.[5] Existing systems used on large submarines required too much space and too much power. Existing systems on small submarines lacked capacity and the ease-of-use required for combat. Internal heating and cooling systems not usually needed for large submarines were needed for the smaller sub that would go into shallower warmer waters or colder surface waters.[6]

Navigation – Sonar systems developed for attack submarines, but needed for the shallow water maneuvers, were large, power hungry, and gave off lots of heat.

Construction – Initial designs and bids were based on standard submersible construction. During later design phases the government imposed full nuclear sub shock, hull and piping requirements on the designers – nullifying the "off the shelf" design approaches requested by the government in earlier phases. To accommodate the larger piping and thicker hull, other systems had to be lightened. (Reference the GAO and RAND reports.)


Two Los Angeles class submarines have been modified to deploy the ASDS, and the new Virginia class submarine is being built with the inherent capability to deploy the mini-sub. Planners originally intended the ASDS to be piloted by one submarine officer and one SEAL. This occurred during initial testing and operational evaluation. However, so far, the first ASDS has been operationally piloted by two submarine officers. The sub was designed to carry 16 SEALs in addition to the two pilots.[7]

Smaller swimmer propulsion devices such as the STD (Swimmer Transport Device) may be carried internally (basically smaller scooters), and small Combat Rubber Raiding Craft (CRRC) or Inflatable Boat-Small (IBS) may be stored internally. However, such craft cannot carry gasoline engines due to safety issues on submarines and fuel issues in small spaces, and therefore have to be paddled or use small electric motors. Semi-rigid, rigid hull, and rigid-hulled inflatable craft such as the ZODIAC cannot be accommodated.

Technical Data

  • Length overall: 65 ft (20 m)
  • Beam: 6.75 ft (2.06 m)
  • Height: 8.25 ft (2.51 m)
  • Displacement: 60 tons
  • Propulsion 67 hp (50 kW) electric motor (Ag-Zn battery) driving a single retractable propeller
  • Max. Speed: 8+ knots
  • Range: 125+ mi.
  • Max. Diving Depth: classified
  • Normal operating depth: > 150 ft (46 m)
  • Accommodations: 2 Crew + up to 16 SEALs, depending on equipment
  • Masts: 2
    • Port: periscope
    • Starboard: communication and GPS
  • Communications Systems:
  • Sonar:
    • Forward Looking – detects natural/man-made obstacles,
    • Side Looking – terrain & bottom mapping, mine detection
  • Aircraft transportability: C-5 Galaxy and C-17 Globemaster III
  • Builder: Northrop Grumman Electronics Sensors and Systems Division, Oceanic Systems subdivision


  1. "Fire deals new setback to Navy's heralded mini-sub". The Honolulu Advertiser. Archived from the original on 17 December 2008. Retrieved 2008-12-16. 
  2. "Problems Persist for SEAL Mini-Subs". Archived from the original on 22 January 2009.,15240,181232,00.html. Retrieved 2008-12-16. 
  3. SEAL Mini-sub Won't Be Repaired, Defense News (Christopher P. Cavas) 2009-07-27. Retrieved 21 August 2009
  4. Cole, William (20 October 2013). "Navy takes new tack in effort to develop minisub in Hawaii". The Honolulu Star-Advertiser. Retrieved 20 October 2013. 
  5. Carlson, NA; Warkander, Daniel E (2005). "Carbon Dioxide Washout of an Emergency Breathing System Mask Modified for Use in the Advanced Seal Delivery System (ASDS) Trainer". Retrieved 2008-09-09. 
  6. Nuckols, Marshall L; Chao, JC; Swiergosz, Matthew J (2005). "Manned Evaluation of a Diver Heater for SDV Applications Using Hydrogen Catalytic Reactions". Retrieved 2008-09-09. 
  7. Kakesako, Gregg L, "Navy Still Investigating Fire Aboard Special Warfare Minisub", Honolulu Star-Bulletin, 21 December 2008.


See also

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