The ASW Continuous Trail Unmanned Vessel (ACTUV) is a DARPA funded project launched in early 2010 to develop an Anti-submarine drone (Unmanned surface vehicle). In September 2014, DARPA signed a Memorandum of Agreement with the Office of Naval Research (ONR) to jointly fund the ACTUV prototype. If successful, the program could transition to the U.S. Navy for ASW, and possibly other missions as a multipurpose unmanned vehicle such as mine countermeasures, by 2018.
It is stated that the ACTUV will be "a first unmanned naval vessel that is designed and sized for theater or global independent deployment". The aim of the four part program is to develop a surface vessel optimized to overtly track and trail target submarines. A suite of sensors "capable of tracking quiet, modern diesel electric submarines" will be implemented into the completely unmanned vessel.
It is intended that ACTUV will operate under minimal supervisory command and control; with shore bases intermittently monitoring performance and providing high-level mission objectives through beyond line-of-sight communications links. The vessel will be provided with advanced autonomous navigation and anti collision features to keep it within maritime law and the International Regulations for Preventing Collisions at Sea.
It is hoped that the unmanned nature of the vessel will open up new technologies in terms of stability and sea keeping. The four part program will culminate in an integrated prototype vessel and sea trials following evaluation and design phases.
Concept of operations
The ACTUV is aimed at improving the ability to detect and engage diesel-electric submarines, which are inexpensive and quieter in comparison to nuclear-powered submarines, and to negate the threat of adversaries building large numbers by creating anti-submarine tactics at one-tenth the cost of building a diesel submarine. Areas of operation are focused on littoral waters. The craft will be an unmanned surface vehicle (USV) designed to operate and patrol autonomously for 60-90 days straight, being able to hunt for targets and avoid surface ships by itself. It will operate alongside other naval assets including the P-8 Poseidon, MQ-4C Triton, and sonobouy sensors as a forward deployed and rapid-response node in the global maritime surveillance network.
Once a wide-area sensor provides an initial indication of a possible target, the forward deployed ACTUV will then rapidly "sprint" to the area and use its own sensors to assess the contact. First, two side pods with long-range acquisition mid-frequency active-passive sonar will verify the presence of a submarine and identify the area of uncertainty (AOU) affected by the threat to limit close surface ships' movement. Second, two higher frequency sonars in the main hull will improve tracking precision and mission reliability. Once in close proximity, total field magnetometer arrays will provide additional information about target activity to continuously track it. Finally, very high frequency sonar will produce an "acoustic image" of the target to identify and classify the specific submarine.
The ACTUV is to be in constant contact with other ships and aircraft through a satellite link; if a contact is determined to not be threatening, a sailor can order the vessel go back on patrol. The craft itself is unarmed, so if an enemy submarine is detected it will notify other naval assets that can attack and destroy it. If deemed not a threat, the craft can still shadow the submarine to deter it from acting aggressively, potentially even back to its home port. The ACTUV is designed to out-endure any diesel-electric submarine, even those equipped with Air Independent Propulsion (AIP).
Using large numbers of inexpensive unmanned ACTUVs are a way to counter submarines as an undersea component of anti-access warfare. Some countries use "competitive strategies" to create cheap weaponry, hardware, and methods to impose on their adversaries a situation where they would need to incur costs of developing countermeasures that are disproportionately higher than the defenses they would be used against. The goal is to make the adversary decide the competition is unaffordable, or force them to redirect resources from other priorities. Countries building cheap diesel-electric submarines as anti-access components would be subjected to the same cost-benefit considerations they are trying to impose, as the U.S. Navy would be equipped with an even cheaper anti-submarine detection system.
In order to comply with International Regulations for Preventing Collisions at Sea (COLREGS), the ACTUV has to autonomously identify other surface ships at sea. Radar is the primary way to sense other ships, but it is not able to classify them. To augment radar, as well as reduce reliance on it, DARPA released a Request for Information (RFI) in March 2015 for other sensors for the ACTUV to perceive and classify nearby ships and other objects. Expected sensor systems and image-processing hardware and software include passive electro-optical/infrared (EO/IR) or non-radar active (LIDAR) technologies.
DARPA allowed the national security, health, and engineering company Leidos to go forward with the ACTUV program in February 2014. Using a USV for submarine hunting is aimed to free up other surface ships from needing to spend time and money looking for them themselves. Leidos' model is an unmanned trimaran built out of carbon composites equipped with navigation and piloting sensors, electro-optics, and long and short range radar to be capable of tracking diesel submarines at extreme depths for months at a time. The vessel is able to report back on the situation and its condition, and has computers programmed to identify other vessels to anticipate what they will do next. It uses a modular design that can be refitted for other roles such as intelligence, surveillance, and reconnaissance missions. Construction is to take 15 months.
Leidos announced on 18 November 2014 that a test vessel fitted with autonomy software and sensors to mimic the configuration of the ACTUV completed 42 days of at-sea demonstrations to fulfill collision regulations (COLREGS). The 32 ft (9.8 m) surrogate vessel simulated scenarios where the ACTUV prototype would interact with an interfering vessel, navigating through narrow channels while avoiding obstructions and other surface ships autonomously in completely unscripted events. Follow-on testing will involve multiple interfering contacts and adversarial behaviors of interfering vessels.
The company announced on 26 January 2015 that the ACTUV autonomy software had been successfully tested off the coast of Mississippi to test sensor, maneuvering, and mission functions. Installed on a 42 ft (13 m) work boat, the autonomy system navigated the complicated inshore environment of the Gulf Intracoastal Waterway using only a pre-loaded navigational chart and inputs from commercial-off-the-shelf (COTS) radars. The surrogate vessel traveled 35 nmi (40 mi; 65 km) while avoiding all obstacles, buoys, land, shoal water, and other vessels without pre-planned waypoints or human intervention. The first ACTUV, named Sea Hunter, is scheduled to launch in late fall 2015 and begin testing in the Columbia River.
- Wanted: Technologies to Enable Automated Lookouts for Unmanned Surface Vessels - Darpa.mil, 26 March 2015
- Here’s How Darpa’s Robot Ship Will Hunt Silent Subs - Wired.com, 27 December 2012
- Autonomous ASW: The Predator Becoming a Prey - Defense-Update.com, 1 January 2013
- Move, Countermove in the Anti-Access Game - Thediplomat.com, 2 January 2013
- Construction begins on DARPA's autonomous unmanned anti-submarine vessel - Gizmag.com, 16 July 2014
- Leidos runs at-sea testing for autonomous vessel prototype - Shephardmedia.com, 19 November 2014
- Leidos’ autonomy system completes voyage - Shephardmedia.com, 29 January 2015