The Future for Unmanned Surface Vessels in the US Navy

Medium Unmanned Surface Vessel (MUSV) concept renderings from shipbuilder Austal USA. Photo Credit: Austal USA

In the past few years there has been an increasing focus on expanding the US Navy’s capabilities through the use of unmanned surface vessels. On September 17^th, Secretary of Defense Mark Esper said “Unmanned will enable us to grow the United States Navy well beyond 355 ships. It will add more lethality, survivability, capability, et cetera, to the United States Navy and indeed to the joint force. So, we’re making all those investments; the research and development budget that we had [this fiscal year] is the largest in history. We’re very excited about that. We have to invest in the future.”[i] This push for autonomous ships comes amidst a broader push for the Navy’s surface fleet to rely on smaller, more distributed systems in the face of enemy threats, particularly anti-ship missiles. Autonomous ships will allow for unprecedented levels of flexibility and decentralization, but come with a host of unknown risks and challenges.

This article provides a brief primer on existing unmanned surface vessel (USV) programs and their expected capabilities in the near-term, before moving on to how they could fit into the current fleet structure and how concerns surrounding command and control will affect different potential mission sets. While unmanned undersea vessels (UUVs) will also bring important changes, they are beyond the scope of this article which focuses only on USVs.

While some might suggest USVs can revolutionize the concept of a capital ship based Navy by replacing vulnerable carriers with decentralized swarm-like formation, such thinking ignores the realities of introducing new technologies. While USVs have the potential to change the Navy, fleet structures cannot simply be replaced but will instead evolve over time. Rather than dream of a hypothetical new fleet structure we must understand how USVs will fit into the existing one.

Current Programs

The Navy has already created several platforms for testing and integrating autonomous USVs.  The Ghost Fleet Overload program has completed its first phase, conducting 600 hours of autonomous navigation with two converted commercial ships, and its second phase is currently testing C2 integration and payload systems[ii]. Additionally, two “Sea Hunter” autonomous ships are undergoing testing with the Navy’s Surface Development Squadron 1. These ships, initially developed by DARPA, are capable of continuously shadowing enemy submarines[iii]. And while not autonomous, small remote controlled USVs are already in use as supporting vessels for the littoral combat ships, carrying out scouting, countermine, anti-submarine, and electronic warfare missions[iv].

For future procurement, the Navy has designated two acquisition programs: Large Unmanned Surface Vehicles (LUSVs) and Medium Unmanned Surface Vehicles (MUSVs). MUSVs would be 45 feet to 190 feet long and tasked with intelligence, surveillance and reconnaissance payloads and electronic warfare missions[v]. LUSVs would be 200 feet to 300 feet in length and be more offensive in nature, armed with anti-ship and land-attack missiles[vi].

Both programs are designed to be crew-optional, allowing for a small crew to remain on-board for missions where more hands-on oversight or decision-making might be needed. It also allows for a kind of “overlap” period where a human presence is maintained while technical and ethical issues surrounding command and control are worked out.

There is an important distinction between the terms unmanned and autonomous. Unmanned means that there are no humans aboard, while autonomous means that the system completes tasks without human input. Systems can be either, neither or both. Predator UAVs flown by human operators are unmanned, but not necessarily fully autonomous. Aegis cruisers used for air and missile defense are manned, but much of the tracking and targeting is already done autonomously by the Aegis combat system. Looking to the future, DARPA is already working on a program called No Manning Required Ship (NOMARS) with the goal of “designing a seaframe from the ground up with no provision, allowance, or expectation for humans at sea”[vii].

This is by no means an exhaustive list of prototypes and programs, but should demonstrate the kinds of technical capabilities the Navy expects USVs to have in the near future.

Command and Control

What would command and control look like and how does that affect the potential uses of USVs? To receive instructions, every system will need at least one of the following command and control systems, or some combination of them.

Autonomous control allows for maximum decentralization, expendability, freedom of design, and minimal operational costs (no crew or 24/7 operators required). It also does not require any outside connection to operate which may be unavailable or undesirable in an electromagnetic (EM) contested environment. However, while AI systems are improving rapidly they are still a work-in progress and their ability to react to more complex situations may be limited.

Furthermore, there are unresolved ethical concerns with lethal autonomous weapons systems (LAWS). Many feel that autonomous systems independently launching offensive strikes crosses a moral line and insist that a human operator must, at the very least, be kept “in-the-loop” and provide final sign-off for any lethal strikes. Others believe that humans being “on-the-loop” by monitoring the actions and performance of autonomous systems provides sufficient oversight. As AI systems mature, it is possible that systems will even one day operate independently with humans “out-of-the-loop”.

The extent to which autonomous systems will take on offensive responsibility will ultimately depend on the public’s level of comfort with autonomous systems. Autonomous systems, while intriguing, have a lot of questions to answer before their use can be seriously relied upon. How confident would the public have to be in such systems? How would the Navy measure, document, and publicize the reliability and risk of such systems (as compared to existing human operators)? What principles will guide these systems and what safeguards will be in place? Any rollout of LAWS will likely be constrained as these questions are resolved.

Remote control allows for many of the benefits of autonomous control, but with humans in-the-loop on the other end of a network connection. This system of control is already in wide use with unmanned aerial vehicles such as the MQ-9. Ethical concerns remain that remote control systems desensitize operators to violence and lead to unnecessary collateral damage, though as it stands now, this existing use case provides a strong precedent for how remote control might be used at sea.

However, remote control requires a dependable, robust connection which may not be available in an EM contested environment where communication signals could be jammed or could give away the location of the ship. In this situation the system would either need to revert to autonomous controls or simply become a floating husk.

Human sailors can operate EM-independently without sacrificing system oversight. In the context of USVs, this would mean ships which perform most tasks themselves but retain a tiny crew to perform key command, control, and oversight tasks. In some ways this is the best of both worlds, however such “crew-optional” or “lightly manned” ships still severely limit some of the potential gains from USVs. One of the benefits of USVs is that they are more easily risked in dangerous environments, but the minute you put a single human sailor aboard that risk tolerance understandably plummets. Additionally, the need to house humans constrains ship design choices and operations, putting limits on just how small, streamlined, and decentralized the systems could reasonably be.

This set of options and trade-offs will affect each potential role differently. Due to the diversity of mission sets/requirements, a one-size-fits-all approach to new command and control systems will not sufficiently meet the needs of the future Navy.

Potential Roles

How and where both unmanned and autonomous capabilities will be used is a much more open ended question. When dealing with new technologies there is no roadmap and predictions on how novel capabilities will be implemented can easily become lost in speculation. But to determine how USVs will be used initially, it is helpful to fit them into an existing framework of naval operations. One of the most authoritative books on the subject of modern naval tactics is Fleet Tactics and Naval Operations by Capt. John Hughes. In it, Hughes lays out four categories of naval forces: Battle fleets, cruisers, amphibious forces, and flotillas.

Battle fleets are blue-water fleets used to defeat (or at least deter) the enemy fleet and gain dominance over the seas. For the US Navy, this is the role of carrier strike groups. USVs would be able to supplement their capabilities and defenses, making these fleets more distributed and survivable. In the latest addition released this year, Capt Hughes notes “[The battle fleet] will be increasingly characterized by swarms of smaller ships, armed with missiles and unmanned systems, that can substitute for large, expensive capital ships in a more distributable, mobile, and collaborative battle fleet”[viii]

• Small USVs can scout around the outside of the fleet and extend the range of the radar coverage. Although airborne drones are currently used to extend the radar horizon, USVs would likely be able to operate with greater independence and endurance.
• Missile armed LUSVs can also contribute to the air defense capabilities or act as floating ordinance batteries to increase a strike group’s firepower.
• Smaller, more disposable USVs could act as decoys or carry out electronic warfare tasks.

With battle fleets, USVs will likely be acting more as extensions of the fleet, rather than independent entities. This means that human operators could often be kept in-the-loop remotely from nearby capital ships. Alternatively, in a battle situation where reliable communications may not be assured, these ships might be allowed to operate autonomously. Once again, whether that autonomy would include lethal action depends on how states answer difficult moral questions. If the very concept of LAWS is determined to be inherently unethical, then it would seemingly preclude this use case and limit full autonomy to support missions. However, if the main concern is the accidental targeting of non-combatants, then blue-water fleet actions against a defined enemy force would seem to provide an environment with less room for misinterpretation.

Cruisers are used to defend commerce and maintain freedom of the seas, or to deny the same to an enemy[ix]. Even if overall command of the sea has been won, nations will still need to monitor and protect commercial traffic. Cruisers are perfect for this mission—conducting patrols or even acting as convoy escorts— due to their ability to cover the vast geographic spread of maritime traffic, unlike less flexible battle fleets. Note that the term “cruiser” in this context refers more to mission responsibilities than to a specific class of vessels. Arleigh Burke class ships are designated as destroyers but often fill the role of a cruiser, as might USVs in the future.

• A swarm of small scout USVs could work with a more traditional manned cruiser or destroyer, massively extending the coverage of the main ship.
• Armed LUSVs could carry out patrols or convoy escorts themselves.
• USVs similar to the Sea Hunter could carry out ASW operations.
• Scout USVs could be invaluable in search and rescue operations where covering the most territory as quickly as possible is paramount.

In a cruiser role, further from any active battle waters, it is easy to see USVs fitting in. USVs would be able to autonomously handle much of the day-to-day legwork of patrols, convoy escorts, and ASW missions. Scout MUSVs could act as the eyes and ears of the fleet, alerting LUSVs in the area to any unusual activity. These LUSVs might make good use of the crew-optional configuration, operating unaided most of the time while relying on a small crew to manage interactions with other vessels. Not only would this expand the effective coverage area of operations, it would free up resources and personnel to deal with more active, hands-on regions.

Amphibious forces are used to deliver personnel, equipment, and support from sea to land[x]. Not all amphibious tasks may seem well suited to USVs. After all what’s the point of going through all the effort to remove human operators from a landing ship, only to then pack it full of Marines? However, there are a variety of support roles for which USVs show a lot of potential.

• Delivering heavy equipment and supplies to shore. With a swarm of unmanned landing vehicles ferrying equipment to shore, offloading can be more distributed and automated, reducing the vulnerability of landing forces.
• Unmanned systems can perform dangerous anti-mine operations in support of the landing.
• Missile armed USVs can carry out ship-to-shore airstrikes in support of ground operations.

Flotillas are fleets made of smaller combatants, used to fight in littoral areas where it is too risky to send a blue-water battle fleet[xi]. The US Navy has long operated with unquestioned control of the seas but with anti-ship missiles becoming increasingly lethal, long-range, and accurate, that assumption is being challenged. China in particular has devoted a lot of time and effort to developing its missile forces including the DF-21 anti-ship missile, sometimes called the “carrier killer”[xii]. As the littoral area becomes both larger and more dangerous, the Navy will need to learn how to operate in the shadow of land based anti-ship missiles. The littoral combat ship (LCS) programs, though mostly known for their painful development processes, were a first attempt at moving towards ships with lower costs, smaller crews, and flexible, modular capabilities (including the ability to operate with unmanned systems). As the Navy works to build flotilla capabilities that emphasize speed, stealth, and decentralization, USVs will likely play a key role.

• One LCS could be surrounded by a small network of USV wingmen to increase its range of view, firepower and survivability.
• Small USVs could be operated as a swarm to scout wide areas or to attack larger ships which may have greater firepower, but the inability to engage so many targets at once.
• Larger USVs could operate independently to locate, track, or even engage ships. The ability of USVs to autonomously operate in an offensive capacity in high-risk areas would be highly valuable, but also raises command and control questions. Unlike battle fleets which engage other battle fleets in open waters, the littoral areas are often crowded with commercial traffic and land based enemies, increasing the risk for accidents.

Ships operating in the flotilla role have the steepest command and control trade-offs. Flotillas are expected to operate in environments that are complex, high-risk, and EM-contested. At best, each command and control system is only equipped to handle two of the three. Autonomous systems are useful for operating in high-risk, EM-contested environments, but concerns remain about their ability to operate independently in complex situations. Remote control systems are useful for operating in complex, high-risk situations, but may be vulnerable in EM-contested environments. And lastly, human crewed ships are useful for operating in complex, EM-contested environments, but are not ideal to place in high-risk situations. Dealing with this autonomous-remote-human triad will require difficult compromises.

In the near term, this may mean lightly crewed, armed ships working with unarmed support USVs operating remotely/autonomously. In that regard, such a composition would likely build off of the framework provided by the current littoral combat ship programs.

Conclusion

With or without lethal autonomy, USVs of all shapes, sizes, roles, and control systems will soon be making a large impact on the world’s navies. As with many emerging technologies the potential ramifications of unmanned systems can seem overwhelming, almost limitless. Imagining the myriad possibilities can be both useful and entertaining, but it’s important to remember that these systems will come into being over time. And as they do, they will work themselves into the existing structures and frameworks. Evaluating USVs in this light can help us to bring semblance of order to the chaos that often accompanies rapid technological change.