ROBOTICS AND AUTONOMOUS SYSTEMS
Sailor-Less Ships Soon Could Be a Reality in U.S. Navy
It was 15 years ago when Vice Adm. Walter Cebrowski and Professor Wayne Hughes discussed the need to develop a network of small, inexpensive, minimally manned and unmanned platforms that would complement the Navy’s larger force-projection ships and provide access to the contested littorals.
Their anticipation of what we now call the anti-access/area denial threat was remarkably prescient. They foresaw that large combatants, although cost-effective in terms of power projection per dollar, were brittle and at risk of being negated by a sophisticated adversary’s use of modern anti-ship missiles. They argued that large numbers of small platforms, although individually less survivable, would provide a more robust capability to “gain and sustain access.”
It was expected that a significant number of these small platforms, which they dubbed “streetfighters,” would be lost to enemy action in a major conflict, but that in so doing, they would divide the enemy’s attention and deplete its offensive and defensive capability. The streetfighter vision was influential at senior levels within the Navy and led to serious discussion about the need for a small combatant designed for the littorals. This eventually led to acquisition decisions in the early 2000s that resulted in today’s littoral combat ship.
The vision of operating LCS out in front is severely limited by the fact that it is a manned platform, and therefore not truly expendable. The notion that manned platforms on land, sea or in the air could be designed to be expendable in battle has been shown to be politically impractical. The decision to invest more than $20 billion in a crash program to design and field the mine-resistant, ambush-protected ground vehicle is testament to the value that we place, appropriately, on providing a reasonable degree of survivability to any manned platform that is expected to go in harm’s way.
Decisions to increase the level of survivability were a factor in driving up the cost of the littoral combat ship from the original vision to the ships that are being delivered today. Although not a small or inexpensive vessel in historical context, LCS may be the smallest and least expensive commissioned manned warship that the U.S. acquisition system is now capable of producing. It’s also likely that concerns about the survivability of the LCS will lead to reticence in committing it to use in the highest threat scenarios of the future.
The “streetfighter” vision of swarms of small combatants operating close to an enemy’s shoreline in conditions where large numbers of platforms may be lost is not appealing when each platform carries 75 or more sailors.
The Navy’s progress in fielding unmanned surface and undersea systems is less clear. Unmanned surface vehicles are being incorporated in the LCS mine countermeasures mission module, and the Navy is moving forward with the fielding of a large diameter unmanned undersea vehicle. Budgets for these programs are small compared to the manned platforms that they support and to the sums being spent on unmanned air systems.
The Navy’s vision for unmanned sea vehicles is also limited by the self-imposed paradigm that unmanned platforms must be hosted by a manned combatant. The LCS is designed to launch and recover unmanned sea vehicles, but these vehicles are restricted in size to approximately 10 tons, about the size of an 11-meter rigid hull inflatable boat. Unmanned surface vehicles of this size have minimal payload, range and open-ocean sea keeping capability, which will constrain their ability to conduct meaningful operations at any significant distance from the host platform.
The desire to host a large unmanned undersea vehicle within the payload tube of a ballistic missile or attack submarine provides similar limitations on vehicle size and endurance, with the additional complexity of balancing propulsion energy density against the need for submarine safety certification. Nobody would suggest that a Global Hawk should be launched and recovered from an aircraft, so why should unmanned sea vehicles be constrained in size just to enable launch and recovery from a manned vessel?
Another decision is whether to operate on or below the surface. The Navy is actively pursuing technology for both undersea and surface vehicles. Undersea vehicles are inherently stealthy, a requirement for certain missions and a significant contributor to survivability in any mission.
On the other hand, surface vehicles are much simpler to build and carry more useful payloads per dollar than undersea vehicles. Surface vehicles can use standard diesel engines for power, providing a major energy advantage over even the most exotic air-independent energy systems. Operating on the surface enables sensing and communicating in the acoustic domain underwater and the radio frequency domain above water, providing real-time connectivity and relevance to the rest of the battle force.
A significant concern in transitioning autonomous surface vehicles from the lab to the fleet is safety. An autonomous surface vessel large enough to carry useful payloads over long distances is also large enough to inflict significant damage in a collision, so the concern is not only the economic loss of the unmanned vessel, but the potential threat to other vessels.
Can an unmanned vessel be designed to comply with the International Maritime Organization rules for avoiding collisions at sea? The answer is most likely yes, and this is certainly one of the primary challenges in fielding an autonomous ship. Over the last eight years, under Defense Department sponsorship, autonomy technology has been developed and demonstrated at sea. The initial requirement for such a system is robust sensing, using radar, electro-optical/infrared and other sensors to develop a comprehensive world model showing the location and classification of all surface contacts in the vicinity of the unmanned vehicle.
Once the surface contacts are known, the autonomy system uses the concept of “velocity obstacles” to develop a map of speed and range combinations.
The autonomy system continually selects the best course and speed to meet mission objectives within the constraints of current regulations. The remaining work to field this technology is not insignificant, since more testing and refinement is needed to build a reliable and trustworthy system. This is analogous to the work now being done by Google and others to develop autonomous cars.
The Defense Advanced Research Projects Agency is developing technology that may enable a move away from the concept of unmanned sea vehicles as adjuncts to manned host platforms, and toward the concept of unmanned sea vehicles self-deploying from a pier and carrying significant payloads over long distances for missions that may last several months, and doing so with a high degree of autonomy. A prototype vehicle is being developed in DARPA’s Anti-Submarine Warfare Continuous Trail Unmanned Vehicle program.
In a February 2010 solicitation, DARPA said the ACTUV program will develop an unmanned X-ship design based on the premise that a human is never intended to step aboard at any point in the operations cycle.
Faced with this bold mandate, companies sought to design the optimum hull form, employ nontraditional shipbuilding methods and integrate commercial off-the-shelf sensors and state-of-the-art autonomy software — all for $20 million or less per copy.
In the months following a 2010 industry day, three teams were awarded contracts for concept exploration. The Science Applications International Corp. team (now Leidos) was selected to build a prototype. On the team were CDI Corp., Gurit, Raytheon Co., NASA’s Jet Propulsion Laboratory, Carnegie Mellon University, Oregon Iron Works/Christensen Shipyard and the Virginia Institute of Marine Sciences.
The ACTUV modular systems architecture allows for the main hull, bow, mast, keel and side hulls to be produced separately. When deployed, the vessel may be capable of autonomous operations under sparse supervisory control. It could track an evading diesel electric submarine for up to 70 days. The ACTUV may be capable of speeds up to 27 knots and operating in rough waters. Its shallow draft and flexible propulsion plant means it may operate from almost any port, with no tugs or special port labor skills or infrastructure requirements.
With a price tag of $20 million or less per vessel, ACTUV would provide the fleet an economical alternative, given the new construction costs of surface combatants.
The days of building a mission-specific ship are over. Looking at the ACTUV platform as an “autonomous truck” leads to many more possibilities for missions and configurations. It is a blank canvas.
It may be capable of minefield detection and mapping, hydrographic survey operations, anti-piracy and anti-drug surveillance and fisheries monitoring. Other missions currently performed by manned vessels are also possible with some design changes.
The road ahead for ACTUV is not without risk, primarily in the development of the autonomy software. To mitigate some of these risks, its design and production will follow a “build a little, test a little” approach with software and sensors.
Given the difficulty of the autonomy problem, DARPA is pursuing several parallel paths to mitigate technical risk. It is working with Charles River Analytics Inc., Daniel H. Wagner Associates, Georgia Tech Research Institute, Northrop Grumman Corp. and Spatial Integrated Systems Inc.
Future tests are scheduled for summer 2015.
Is the Navy ready to embrace an autonomous surface ship operating with the battle group? Probably not, at least not yet. But then again, there were many vocal skeptics when the Predator unmanned aircraft was first introduced to the U.S. Air Force. Disruptive technologies are always, well, disruptive, and ACTUV will be no different.
David Antanitus is a retired Navy rear admiral. He is currently a senior capture manager in the surveillance and reconnaissance group of Leidos in Chesapeake, Va.
Topics: Robotics, Unmanned Underwater Vehicles, Science and Engineering Technology, DARPA, Shipbuilding