Update 11/23/2017: General Dynamics Bath Ironworks has teamed up with Navantia to offer a derivative of the F100/Fridtjof Nansen frigate family to the US Navy. See below for details on the Fridtjof Nansen class and its interoperability benefits.
A previous article on WhiteFleet.net examined the US Navy’s frigate program, which was, at the time, focused on turning one of the Littoral Combat Ship variants into a capable frigate. However, it appears that the Navy has decided to widen its search, according to a recent article by the United States Naval Institute News (USNI News). The Navy’s new investigation is taking another look at the requirements for the program and “explore[ing] other existing hull forms,” which essentially means that existing designs by foreign shipyards may be considered. Defense News also reported on the shift in philosophy, noting that the Navy’s decision essentially means a clean slate for the frigate program.
Because the Navy has only issued a request for information (RFI) and has not begun a program of record, nothing is set in stone. Yet, issuing the RFI certainly seems expedient. Recent years have been a sort of golden age for frigate construction — as shipbuilding technology improves and electronics get smaller, manufacturers are able to create frigates with multi-mission capabilities that would have required a destroyer or cruiser in the past. In fact, many navies now use frigates as their flagships. The past few decades have also seen a huge divergence within the class itself — while frigates used to be small ships of limited capability and range, some modern “frigates” weigh over 7,000 tons and boast serious combat power, while others adhere to the more traditional frigate displacement of ~3,000 tons.
There are numerous frigate designs in foreign service, but not all would be suitable. The following is a list of attributes the Navy will look for:
- Relatively small. The Navy already has expensive Arleigh Burke-class destroyers for escort duties and missile defense — the point of buying frigates is to diversify the fleet rather than add another large warship.
- Relatively cheap, for the same reason as the above point.
- Designed by a US ally. The Navy is not going to produce a Russian or Chinese frigate design, for fairly obvious reasons.
- Capable of integrating American systems. To reduce costs, the Navy will want a design which can utilize existing American guns, electronics, etc. The RFI specifies that contenders should utilize the Enterprise Air Surveillance Radar, a three-array fixed design which utilizes the same modules as the AN/SPY-6 (also known as the AMDR).
- A relatively recent design, because the Navy will not want to build new ships based on an obsolete blueprint.
- Available for license production. Congress would not agree to buy a large warship unless the vast majority of the work, including final assembly, was carried out in the US where it would benefit the economy.
- Capable of sustained operations at 28 knots when fully loaded. The Navy’s RFI identifies 28 knots as the threshold (minimum) top speed, although a 30 knot top speed would probably be preferable, as most of the Navy’s other major warships can reach 30 knots.
- 3,000 nautical miles of range at 16 knots, as specified by the Navy’s RFI. This is not a particularly strenuous requirement, as most frigates on offer have a range well in excess of 3,000 nmi.
The rest of this article considers a few examples of classes which fit this description and exemplify the capabilities offered by off-the-shelf frigate solutions.
Istanbul (TF-100) class
The TF-100, also known as the Istanbul class, is a lengthened derivative of the Turkish Ada-class corvette. Despite displacing around 3,000 tons, the class boasts a 16-cell Mk 41 VLS, enabling it to carry a wide array of American missiles. For anti-surface firepower, the vessel has 16 subsonic, sea-skimming Harpoon missiles. A 76 mm gun, two 25 mm autocannons, and a 20 mm Phalanx CIWS provide close-range firepower. Two triple Mk 32 lightweight torpedo tubes are used for anti-sub warfare, in addition to an enclosed hangar for one helicopter. The class’s combined diesel and gas (CODAG) powerplant uses two MTU diesel engines and an LM2500 gas turbine, allowing the ship to reach 29 knots. Cruising range is about 6,000 nmi at 14 knots, so 3,000 nmi at 16 knots should be attainable. For air search, the class has a Thales SMART-S rotating radar.
The Istanbul class manages to pack a serious arsenal of weaponry into a small platform, while retaining a helicopter hangar and all the other standard features of a modern surface combatant. The inclusion of 16 Harpoon canisters is especially appealing, as the Navy is desperately seeking ways to boost its anti-surface capabilities and mentions over-the-horizon missiles frequently when discussing the frigate. Better yet, the design already uses a remarkably high proportion of American equipment; from the Mk 41 VLS cells to the Mk 32 torpedo tubes, the Phalanx CIWS, and the LM2500 gas turbine, much of the Istanbul-class frigate’s equipment is American, meaning a sharp reduction in the amount of time and money spent on modifying the design to accept the US Navy’s preferred systems. The main exception is the class’s SMART-S radar, which will need to be replaced with the EASR, possibly requiring a redesign of parts of the mast and superstructure. Another issue is that Turkey and the United States have found themselves at odds recently, especially regarding the future of the Kurdish people in Syria — such disagreements would need to be addressed to some extent before such a major collaborative effort could begin.
The Daegu-class frigate, also known as the FFX-II, is a Korean frigate class based on a previous design, the Incheon-class (FFX-I). Relative to the Incheon-class, the Daegu-class is larger, has improved stealth measures, and is better suited to high-intensity blue-water operations. The vessels displace around 3,600 tons fully loaded and feature 8 SSM-700K SSMs and 16 Cheolmae-2 SAMs in VLS cells. Gun-based firepower consists of a 127mm Mk 45 and a 20mm Phalanx CIWS. For anti-submarine operations, two triple Mk 32 lightweight torpedo launchers are standard. The aft flight deck also includes an enclosed helicopter hangar. Propulsion is provided by a combined diesel-electric or gas (CODLOG) system powered by an MT-30 turbine, a configuration which propels the class to 30 knots. Endurance is 4,500 nautical miles at 16 knots. The ship’s primary radar is a Korean LIG Nex1 550K air search set.
While the lack of Mk 41 integration is disadvantageous, the Cheolmae-2 VLS cells are roughly similar in dimensions, so incorporating the Mk 41 would probably be feasible. Furthermore, the 127 mm gun would likely be replaced with a smaller model (the Navy’s RFI requests a 57mm gun), and the rotating 550K would need to be discarded in favor of the fixed setup required by the Navy. The Rolls Royce MT-3o turbine is not currently deployed by the Navy but the logistical burden may be small enough to ignore. On the plus side, the FFX-II’s 30 knot top speed is highly desirable, as it would allow the class to maneuver with a carrier group at full speed. South Korea and the United States already have strong defense ties — Lockheed has teamed up with KAI to offer the Korean T-50 jet trainer to the US Air Force, and the South Korean military operates a plethora of American equipment. Thus, transfer of the FFX-II design would be simple from a diplomatic standpoint.
Fridtjof Nansen class
The Fridtjof Nansen class is a 5,300-ton frigate class in service with the Norweigan Navy and built by Spanish shipbuilder Navantia. It is based on the Spanish Navy’s own Álvaro de Bazán-class frigates, but with a lighter armament, reducing cost and displacement. The design has eight Mk 41 VLS cells standard, with the option for another eight, and eight subsonic Naval Strike Missiles (NSMs) for anti-shipping duty. As far as guns, a 76mm is standard with the provision for another, and the first 76mm mount is designed to accept a 127mm gun if needed. For anti-submarine operations, the ship has four Stingray lightweight torpedo tubes, which are embedded in the superstructure. A hangar for an NH-90 medium helicopter is present at the rear. The combined diesel and gas (CODAG) powerplant allows a maximum cruising speed of around 27 knots, while range at 16 knots is 4,500 nmi. The ship’s main air search radar is the SPY-1F, a miniaturized version of the SPY-1 radar used aboard the Navy’s cruisers and destroyers. The radar is integrated with the Aegis Combat System.
One benefit of the Nansen-class is immediately apparent: off-the-shelf interoperability. Not only does the class have American weapons and engines, it even shares a combat system (Aegis) with the rest of the American surface combatant fleet. Nevertheless, there are some issues, especially the below-threshold top speed — fixing this issue would likely require an upgraded LM2500, if not costly alterations to the hull and/or drivetrain. Armanent is also relatively light — the Istanbul class has the same number of VLS cells but weighs 2,300 tons less. On the flip-side, the Nansen-class frigate delivers excellent anti-submarine capabilities and already has a dedicated mast for fixed radar arrays, which could be repurposed to mount the EASR (albeit with some modification, as the EASR will use three arrays instead of four).
The Sachsen class is a large German frigate class, vessels of which displace around 5,700 tons fully loaded. The design features eight Harpoon SSMs in two above-deck quad launchers and one 32-cell Mk 41 VLS system. As such, it has the largest SAM magazine capacity of any vessel on this list. For close-range anti-missile defense, the vessel has two Rolling Airframe Missile (RAM) launchers. Gun-based firepower is supplied by a 76mm compact gun and two 27mm autocannons. Anti-submarine armament consists of two triple MU90 torpedo tubes. Unlike the other frigates considered here, the Sachsen class has enough hangar space for two medium helicopters. A CODAG drivetrain with two MTU diesel engine and an LM2500 gas turbine provide a peak output of 51,000 bhp, good for a maximum speed of 29 knots and a range of 4,000 nmi at 16 knots. For air search, the class uses a pairing of the Thales Nederland APAR and SMART-L.
Like with the Nansen-class, the inclusion of Mk 41 VLS in the design would ease integration. The Sachsen class, however, has twice the Mk 41 cell capacity of the Nansen-class, which would be highly appealing should the Navy decide its frigates need significant anti-air firepower for escort operations. With 32 cells, the class could support a mixed loadout of Standard Missile-2s, ESSMs, and surface-to-surface VLS missiles such as the Long Range Anti-Ship Missile (LRASM), lending significant flexibility. Like the Nansen class, the APAR radar mast could be repurposed for the Navy’s EASR. On the other hand, with a displacement pushing 6,000 tons, the Sachsen class is on the large side and would certainly represent a change in philosophy relative to a nimble, lightly-armed LCS-based frigate. If the Navy were to decide that a frigate of around 6,000 tons is necessary, there are other slightly heavier options such as the Danish Iver Huifeldt class and the Dutch De Zeven Provincen class as well, although those vessels would be even further encroaching on the role of the Arleigh Burke-class destroyers.
If the Navy does indeed decide to open the frigate competition, there is no guarantee that these designs would necessarily be submitted or even qualify in the first place. Nevertheless, they illustrate the strength of foreign frigate offerings, many of which already use American systems and are tested, proven designs. If the Navy is willing to accept an off-the-shelf solution and a degree of flexibility regarding requirements, there is no reason a foreign-designed frigate could not be produced by an American shipbuilder to quickly fill the gap in small, robust guided-missile combatants.