In an attempt to build on its success in designing and building a new class of high-endurance cutters that are successfully operating for the U.S. Coast Guard, Huntington Ingalls Industries [HII] has introduced two variants of the ship for international customers amid what it says is strong demand for patrol frigates.

Over the next 20 years, HII estimates demand from international navies and coast guards for about 215 patrol frigates, with about 122 of those from Asia and Australia, 45 from Russia, 22 from NATO, with the remainder in the Caribbean and Latin America, the Middle East and North Africa, and Europe, Mike Duthu, the company’s head of Coast Guard programs, said at a media briefing on Wednesday at the annual Surface Navy Association Symposium in Arlington, Va.

HII has built and delivered three 418-foot Legend-class National Security Cutters (NSC) for the Coast Guard and is under contract for two more of the vessels. The Coast Guard plans to purchase eight NSCs to replace its fleet of 11 378-foot Hamilton-class cutters that are about 40 years old.

The NSCs, which are the flagship of the Coast Guard’s fleet, perform maritime security missions as well as support the mission requirements of joint U.S. combatant commanders. Coast Guard helicopters can operate from the vessels, which are also designed to work with unmanned aircraft systems, and they are equipped with various sensors and surveillance systems as well as a 57mm gun, a 20mm close in weapon system and an active expendable decoy system.

The hull and structure of the NSC serve as the essential building blocks of the two derivatives HII is offering to international customers, the Patrol Frigate 4501 and Patrol Frigate 4921.

“We feel that our experience, our capacity and our product give us an excellent advantage in entering this market,” Duthu said of the international patrol frigate opportunities. “We have a ship that has a tremendous capability. It’s got a demonstrated operational performance at sea. We have a very stable design baseline. And we have a very active construction line.”

The 4501 and 4921 are both “production ready now,” Duthu said. The 4501 is basically aligned with the current NSC, although it would require some limited non-recurring engineering, and the 4921 would require “limited design changes based on customer needs,” he said.

Like the NSC, the 4501 would have a 12,000 nautical mile range, 60-day endurance, operate at up to 28-plus knots speed and have accommodations for 148 people. The Coast Guard puts the endurance of the NSC between 60 and 90 days.

However, the 4501 would have more armament, including six 50-caliber machine guns.

The 4921 would be a more robust military craft, including a larger 76mm gun, a 12-cell vertical launch system, an anti-ship missile launcher and torpedo launcher, and a combination of remotely controlled and manned 50-caliber machine guns. The 4921 could also integrate various other sensors including a 3D air search and fire control active phased array radar, electronic support measures, hull mounted sonar, a towed array sonar and torpedo decoy. The vessel could also have stowage for torpedoes and sonobuoys.

The additional equipment on the 4921 would limit the vessel’s range to 8,000-plus nautical miles and its crew to 141 while still having a maximum speed of 28-plus knots and 60-day endurance.

The range and endurance of each derivative give them an extended on station presence, Duthu said.

Regarding the capability of the NSC, Duthu cited testimony from last year by Coast Guard Commandant Adm. Bob Papp, who described the initial NSC, the Bertholf, operating in the Bering Sea for over a month while contending with 20-foot seas and 60 knot winds and still staying within roll and pitch parameters to launch and recover its helicopters, something the service’s fleet couldn’t do previously.

Duthu also pointed to a number of  “quality of life” features in the NSC that would make them attractive to international customers such as various state rooms that can accommodate mixed gender crewing, law enforcement and other detachments, as well as land connections and entertainment, recreational and entertainment facilities.

Duthu declined to disclose any particular country that HII believes is the best prospect for initial patrol frigate sales but said it has talked with potential customers.

HII made a “corporate decision” to pursue the international market with the NSC derivatives, Duthu said. The company is investing resources into the effort, he said.