Concept For Low-Cost Autonomous Anti-Ship Submarine
As the US Navy's Orca XLUUV program gathers pace, and other navies look to larger AUVs (Autonomous Underwater Vehicles), it is time to consider what the future might look like. Specifically, what a low-cost, low-risk XLUUV might be like. This thought exercise combines current trends, concept of operations and a few original ideas to create a notional XLUUV design. This concept is well suited to littoral combat in restricted areas such as straits and archipelagos
The starting point was actually a question about what Iran's first XLUUV might be like. The concept of operations (CONOPS) of the IS-120 Ghadir Class midget submarine appears so simple that it could conceivably be automated. It sits near shipping lanes in restricted waters, particularly the Straits of Hormuz, and waits for a surface target. Ideally it is submerged but in practice these small cramped submarines likely spend a fair amount of time on the surface. An autonomous version could pose a more persistent and survivable threat.
Building off the Iranian scenario, this concept uses western AIP technology to increase stealth. This also removes the mechanical and operational complexity of snorkeling. Combined with Lithium-ion batteries, the endurance would be a week or more. During this time the vessel could be patrolling at slow speed, or sitting on the sea floor.
A critical factor is that, to keep costs down and timelines realistic, its a single-mission design. A real risk in current XLUUV design is ballooning mission requirements. With planners (and politicians) still learning where AUVs fit into naval doctrine, there is a tendency to list an incredible array of possible roles. ISR, mine warfare, casualty evacuation, cargo transport, sensor placement, AUV mother-ship and so on. This design aims for possibly the technically least challenging offensive role; anti-ship ambush.
A key characteristic is that the AIP generators and key systems are contained within a pressure hull large enough for human access. This doesn't have to be large enough to support a crew while at sea, but greatly simplifies pier-side maintenance.
Other systems requiring access or checks, such as the liquid oxygen valves, electric charging points, air flasks for ballast and masts are all accessible in the casing on top of the sub.
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Armament consists of two heavyweight 533mm (21") torpedo tubes. These are self-contained units with integral compensation tank and launch system. They are pre-loaded with the torpedoes and can be replaced while the boat is in the water.
These would cost a fraction of current submarine costs. They'd use less materials and be built with much smaller tooling. Their relatively modest performance envelope, particularly depth, would also be a cost reducing factor.
Therefore a significant number could be deployed either before or during conflict, and either defensively within local waters, or in offensive-defense in an aggressor's back yard.
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