Though the Navy has not yet specified which missions the vehicle will perform—an analysis of alternatives (AoA) now being conducted by Naval Sea Systems Command is slated for completion next March—a few possibilities present themselves. The stealth and persistence of a long-endurance AUV will be especially useful for intelligence, surveillance and reconnaissance (ISR) or preparation of operational environment (IPOE) missions, such as bottom mapping. But it is not hard to envision the LDUUV carrying mines, bomblets or miniature torpedoes, and performing missions previously in the domain of manned submarines like the tracking of enemy submarines.
LDUUV could also be uniquely suited to address emerging missions like defense of the pipelines and telecommunications cables that are increasingly vital to the global economy, or attack on an adversary's undersea sensor networks. Simply put, LDUUV will fulfill a persistent ISR and battlespace preparation role, but will also expand the reach of the U.S. submarine force and perform missions that are impossible for anything in the current arsenal. Moreover, it will enter just in time to mitigate the slump in force structure that will hit in the 2020s, as the large Cold War fleet of Los Angeles- class subs retires.
The new craft is different in important ways from failed predecessors like the Mission Reconfigurable UUV (MR-UUV). Released from “the tyranny of the 21-inch tube,” it has more room for energy storage and payloads. It is designed for launch and recovery from a variety of platforms: SSGNs and Virginias via their large-diameter tubes, the Littoral Combat Ship, piers, or contracted merchant ships. Energy technology has advanced since the MR-UUV as well, allowing for greater energy density and longer endurance—though much work remains to be done in this area to produce an operationally useful vehicle. And perhaps most importantly, it has support at the highest levels of the Navy. In February, the chief of naval operations, Adm. Jonathan Greenert, told reporters “I'm very much desirous of that end-state, cross-ocean, as feasible . . . 30-day, 45-day.”
After the LDUUV AoA is completed in 2013, the Navy is likely to issue a formal request for proposals in fiscal 2014, according to a February statement from the LCS program office, its sponsor. In the meantime, ONR plans to produce 10 Innovative Naval Prototype (INP) vehicles, focusing on technologies that will improve energy density, autonomy and reliability. These prototypes will be transitioned from ONR to the fleet after completion of the INP program, and the Navy intends to have a squadron of 10 operational LDUUVs by 2020.
Even more ambitious than LDUUV is a Defense Advanced Research Projects Agency (Darpa) project for an unmanned vessel that can shadow a manned sub throughout its patrol. Darpa recently chose Science Applications International Corp. to lead the design and construction of an operational prototype Anti-Submarine Warfare Continuous Trail Unmanned Vessel (Actuv). The aim is to demonstrate a non-stealthy autonomous vessel that can track a quiet diesel-electric submarine overtly for months, over thousands of kilometers, with minimal human input. At-sea testing is planned for mid-2015.
Actuv has a clean-sheet design, to take advantage of its crewless concept by relaxing normal warship requirements such as buoyancy reserve, dynamic stability and platform orientation. In addition to autonomy and reliability, a key goal of the program is to achieve “propulsive overmatch” and demonstrate “disproportionate” speed, endurance, maneuverability and sea-keeping to enable unconventional tactics in response to target behavior.
Actuv would not detect the submarine, but would relieve ASW forces of the task of keeping tabs on the boat once it has been picked up. It is intended to use acoustic, electro-optical, radar and lidar sensors to acquire and follow its sub targets through high seas and periods of lost communications, while navigating in compliance with international maritime regulations, autonomously avoiding other surface craft. With an unrefueled range of 6,200 km and an endurance of 80 days, the vessel will be under “sparse remote supervisory control” from the shore via beyond-line-of-sight data link.
But as advanced as Actuv and LDUUV may be in concept, they are years away from hitting the water, let alone becoming operational. For the time being, Europe and Israel appear to be well ahead in terms of making autonomous sea systems a reality.