DARPA, the organization which carries out research on behalf of the US military, is in the process of testing a new autonomous, unmanned sub-hunting ship called the ASW (Anti-Submarine Warfare) Continuous Trail Unmanned Vessel (ACTUV) (yes, that is a nested acronym). The ship is designed to cheaply track track Air-Independent Propulsion (AIP) diesel submarines, which are notoriously hard to detect. By eliminating the need for crew compartments, food storage, crew salaries, and so forth, the ACTUV can track subs much more cheaply than any manned platform. ACTUV will follow submarines around and track them with sonar, transmitting data along the way. The vessel itself is not armed, but it can communicate the location of a submarine to armed ASW elements such as the P-8 Poseidon, which can then deliver munitions using ACTUV’s sensors. At around 130 feet long, ACTUV is not a large vessel by US Navy standards (an Arleigh Burke-class destroyer is around 500ft long). While ACTUV is a technology demonstrator and not expected to enter the active fleet itself, the technologies it demonstrates and the philosophy it espouses will likely be incorporated into future designs.
Perhaps the most impressive aspect of the program is how truly autonomous ACTUV is. In a recent test, the ship was able to navigate rocks and avoid other ships in crowded waters with no outside input. The software powering ACTUV is so well designed that it can even follow the UN Convention on the Laws of the Seas (UNCLOS) while operating autonomously. These groundbreaking capabilities could potentially alter maritime warfare in major ways. As of now, even the largest of navies have limits on fleet size imposed by costs. With the average yearly cost of a US sailor hovering around $100,000, manning surface combatants (many of which require hundreds of sailors to operate) is exceedingly taxing on the budgets of navies worldwide. ACTUV-like vessels promise to drastically reduce these costs, which could fuel a massive increase in ship procurement. Of course, an autonomous vessel the size of a destroyer is a pipe dream at this point. All those sailors exist for a reason; on a ship the size of a modern surface combatant, there will always be something in need of maintenance or repair.
From here on it is going to get a bit speculative.
While the concept of ACTUV itself may prove a game changer in the field of ASW, I wish to examine the impacts of ACTUV’s technologies on naval tactics as a whole. ACTUV is phenomenally affordable compared to a normal vessel. At a cost of ~$20 million per ship, the ACTUV is many times cheaper than a modern frigate and doesn’t require sailors on-board. If an armed vessel similar to ACTUV could be produced, it may have far-reaching impacts. As mentioned, large surface combatants are massively costly to maintain and purchase. Autonomous vessels could possibly replace surface combatants in some roles, and provide a cheap way to massively supplement firepower and intelligence gathering.
For example, the ACTUV could be outfitted with electromagnetic spectrum gathering equipment in place of its sonar and sent to prowl the oceans. Navigating autonomously with little input or upkeep, the ~$20 million modified ACTUV could perform a job that normally requires a fully manned vessel to carry out. Even if the modifications ended up doubling the cost of the ACTUV derivative, it would still be orders of magnitude more affordable than a manned ship.
Unmanned vessels such as mentioned above could be perfectly suited towards high-risk loiter missions in combat zones, similar to Unmanned Aerial Vehicles (UAVs). If a manned vessel with hundreds of sailors is sent into disputed waters and sunk, the results are a national tragedy and a serious international incident which could escalate severely. If an unmanned vessel gets sent into disputed waters and sunk, the result would still be a serious incident and inquiry but with far less incentive for serious escalation and a much lower material cost.
The prospects of an armed unmanned vessel are also interesting. Of course, it is doubtful such a vessel could be produced with current technologies. The maintenance requirements of an unmanned vessel much larger than ACTUV would likely reduce endurance and availability to an unacceptable level, and ACTUV’s technology is still experimental. However, ACTUV does have a respectable design endurance of 80 days, which indicates that the reliability of ACTUV is satisfactory enough to allow months of loiter. If technology continues to improve, a larger autonomous vessel with similar endurance could be produced.
Such vessels will most likely employ human controllers during combat, as current military practice strongly favors having a human make weapons employment decisions. Nevertheless, such vessels would offer a cheaper way to bring munitions within range of their targets. Unmanned vessels could serve as a missile-carriers, transporting payloads cheaply and firing them based on targeting information provided by other sources. Or, they could go the UAV route and use small but high-powered optical sensors for employment of short-range weapons. If technology improves enough, an unmanned vessel with advanced radar and datalink capabilities could operate using inorganic sensor data. Furthermore, some missiles in development, such as the LRASM, have autonomous capabilities of their own. A modified ACTUV could fire a salvo of such missiles into an area where enemies are thought to be, and the missiles could loiter until they find a target.
Some of the issues facing unmanned fighter jets do not apply to unmanned ships: unmanned ships do not have to deal with the complexities of triple axis movement, nor do they need to be controlled as finely (latency between unmanned vehicles and their controllers can be greater than 100ms, which can be unacceptably high for aerial combat).
The US had a program for a lightly manned missile platform, the arsenal ship program, which never got off the ground. One problem faced by the arsenal ship was that of survivability: the arsenal ship’s lack of organic defenses could put its sailors at risk. At the very least, the arsenal ship would need an escort whenever it ventured into contested areas, tying up resources. An autonomous vessel dispenses with this concern, as no sailors are at risk during its operation.
While the implications of small unmanned ships for naval combat are many, the introduction unmanned vessels could have major implications for worldwide policy and politics as well. Similarly to how armed UAVs provide a cheap way to surgically strike and monitor targets worldwide, unmanned sea vessels would provide a cheap way for nations to deploy naval assets and conduct operations around the world. Anti-access militaries would benefit from the ability to deploy a large number of ships and menace enemies. This could make certain areas of the world even more dangerous for shipping than they already are, and allow certain states to feel more secure about their ability to deny access to potential adversaries. A possible result of this is the emboldening of nations like China and North Korea, both of which pursue anti-access warfare aggressively (although North Korea will not have the ability to deploy unmanned sea vessels any time soon).
Unmanned sea vehicles could also be a boon to navies with a global presence, such as the US Navy. Instead of struggling to deploy expensive manned assets all around the world, unmanned vessels could reassure allies and monitor the seas, allowing the US to patrol low-risk areas with unmanned vessels and free up high-end platforms for work in demanding missions. Unmanned vessels could have an impact similar to aerial drones, which have long loiter times, allowing the timely surveillance and engagement of elusive targets. With the global deployment of unmanned vessels, global inclined navies could afford to send more combatants to more locations; this could result in the closer monitoring of areas that are normally left neglected, reducing the transparency of the seas and coastal areas. High-risk sectors, such as those that are mined or watched by shore batteries, could also be probed and monitored with no casualties in the case of a hull loss.
A sheer increase in the number of deployed vessels may increase the odds of incidents or accidents. Conversely, the lower importance and value of each individual unmanned vessel may act as a sort of insulation from the hysteria that occurs when a manned combatant is destroyed.
Another interesting political implication of unmanned ships is that their deployment will likely be limited to the more wealthy nations, as access to a satellite network for communications with the ships is required for operating them securely and at long distances. The initial satellite infrastructure investment required could result in unmanned sea vessels becoming a signature piece of hardware for some wealthier nations, such as the USA’s Predator and Reaper UAVs, while less wealthy nations are sidelined by cost considerations.
Of course, this is all speculation. There are a myriad of factors that could forestall the deployment of such unmanned vessels, or change their employment. In any case, given the possible implications, ACTUV will surely be a program to watch as the technology matures and tests are completed.