A new, less costly minisubmarine for Navy SEAL commandos is expected to be prowling Hawaii’s waters in a few years, U.S. Special Operations Command said.

The command has been testing commercial technology subs in Hawaii and Florida following the failure of the 65-foot Advanced SEAL Delivery System.

The military envisioned a fleet of the $80 million ASDS minisubs, but only one was built after the Northrop Grumman effort was beset by technological problems and ballooned to more than $885 million by 2007. ASDS-1 burned at the Pearl City SEAL compound in 2008 as its batteries were recharged, and the program was scrapped the following year as too costly.

In the wake of the failure, the Pentagon decided bigger and more costly is not necessarily better.

Special Operations Command turned to commercial builders, and three much smaller minisub prototypes have been tested over the past several years with a contract expected to be awarded in July for a production vessel with options for two others, officials said.

The new submersibles are intended to allow SEALs and other special operators to travel undetected over greater distances and longer duration and in extreme conditions.

SEAL Delivery Vehicle Team 1 in Hawaii also has underwater vehicles, but they are open to the water and require scuba gear — sapping energy before the elite commandos even get to their mission.

“Current plans have these (minisubs) going to Pearl City,” said Lt. Cmdr. Matt Allen, a Special Operations Command spokesman. “The vessels, support equipment and personnel will be housed in an existing building in Pearl City.”

A $19.85 million addition is expected to be completed in coming years at an existing SEAL building for the mission.

Special Operations Command tested the 24-foot S301i under a $10 million lease from Lockheed Martin; the 31-foot Button 5.60 from General Dynamics/Electric Boat and Giunio Santi Engineering in Italy; and the 39-foot S351 from Submergence Group and MSubs.

According to Defense Department budget documents, $32.4 million had been invested in product development in the Button 5.60 through fiscal 2015, and $31.3 million in the S351.

Limited testing was conducted with the S301i in Hawaii in 2010, and then it was moved to Florida, Special Operations Command said. Testing continues on the S351 and Button 5.60 at Riviera Beach and Naval Surface Warfare Center-Panama City, both in Florida.

In June the command advertised it was seeking a pilot and co-pilot to train fleet sailors to operate the Button 5.60 minisub with the requirement that they be able to conduct underwater transits in excess of 24 hours, use obstacle avoidance sonar and the GEM Elettronica Polaris FOG-100 navigation system, and conduct diver lock-in/lock-out operations.

Technologies tested in the “dry combat submersible” — the Pentagon name for the program — include lithium ion and silver zinc batteries, improved sonar systems and a three-dimensional electro-optical infrared periscope.

Allen said the commercial route has been a success. After the costly ASDS experiment, the command placed an emphasis on the word “affordable.” Allen said use of commercial submarine technology and classing reduced program costs by an estimated 65 percent and saved approximately three years of effort.

THE S301I WAS used for “risk reduction” and included 30 underwater diver lock-outs in a test pool and open water. The larger S351 weighs 57,300 pounds and can carry a crew of two pilots and eight commandos 138 miles at 5.7 miles per hour with high-energy batteries. The Button 5.60 weighs 39,000 pounds and carries a crew of two pilots and four special operators.

The production vessel will be an amalgam of the three tested minisubs, Allen said.

“Performance specifications and various aspects of the request for proposal were developed using best commercial practices, technical/technology information, and validation of performance parameters gained from the S301i, S351 and Button 5.60 technology demonstrators,” Allen said in an email.

The objective requirement is for two crew and six passengers, he said. A Special Operations PowerPoint shows government acceptance testing in fiscal 2018 and initial operating capability in 2019. The second and third submersibles would follow, starting in 2019.

FIVE MONTHS AGO Submergence Group reported that the S351 had successfully completed its first deep dive. The next day the S351 demonstrated its ability to lock out/lock in divers with the company saying chief test pilot Dave Bourn noted “it’s a pleasure to dive and drive” after two days of sea trials.

Another change with the program is the abandonment of the minisub mating to a mother submarine for transport and deployment, as was the case with the ASDS.

“In order to provide a cost-effective capability within a relatively short time frame, a submarine launch capability is not included; increased program costs and extended delivery schedules were significant concerns,” Allen said. “This does not preclude the option to develop a (minisub) launch capability in the future.”

An August request for information by the Navy’s Military Sealift Command said two surface vessels would serve as host ships for Naval Special Warfare, with one in Pearl Harbor and another at Little Creek, Va., for SEAL Delivery Vehicles and minisubs.

On the West Coast the vessel would normally operate in Pearl Harbor; the outer islands of Hawaii; Apra Harbor, Guam; and Keyport, Wash., the survey said. The required ships needed to have a “moon pool” for the launch and recovery of the minisubs.

SEAL Delivery Vehicle Team 2 no longer exists; the unit was disbanded as the result of a consolidation, but a small detachment remains in Little Creek to support Pearl Harbor’s SDVT-1, Allen said. More than 100 SEALs are based in Hawaii.

Allen said Naval Special Warfare already leases a 220-foot support ship at Pearl Harbor and another in Virginia, and as existing leases expire, new leases will incorporate minisubs’ needs with the possibility of an even larger support vessel in Hawaii.

Special Operations Command also is replacing its SEAL Delivery Vehicles that carry commandos in flooded vehicles. The Shallow Water Combat Submersible is the next-generation free-flooding manned vehicle.

Dry Deck Shelters mounted to submarines to deploy SEAL Delivery Vehicles are being upgraded as well. According to Special Operations Command, the Virginia-class subs USS Hawaii, USS Mississippi and USS North Carolina have the capability at Pearl Harbor.

The Navy in 2004 announced the completion of a $47 million waterfront home for SDVT-1 on 22 acres at Pearl City Peninsula. A 326,000-gallon freshwater test tank was built there for the former 65-foot Advanced SEAL Delivery System sub.