An unmanned surface vehicle (such as the Sea Hunter shown here) - combined with sensors towed aloft - provided a significant first-to-shoot advantage in a simulation run at the Naval Postgraduate School.
In the near future, unmanned systems will be prolific in the maritime domain. Chief of Naval Operations Admiral John Richardson wrote in 2017 that unmanned systems must be an “integral part of the future fleet,” and cited their potential to “drive down unit costs.”1 The current testbed for unmanned surface vessels (USVs) is the Defense Advanced Research Projects Agency (DARPA) Sea Hunter, a 132-foot, 135-ton USV designed to operate on the open ocean. Once the technologies and autonomous behaviors of the Sea Hunter reach maturity, they will be realized operationally in the medium-displacement unmanned surface vessel (MDUSV) concept.
The MDUSV has the potential to expand sensor ranges over the horizon. Towed Airborne Lift of Naval Systems (TALONS), a parasail platform recently deployed from Sea Hunter, may carry communications antennae, radar, and electro-optical and infrared (EO/IR) sensors.2 A MDUSV with similar parasail-mounted radars or electro-optical sensors could extend communications range and surveillance area, augmenting helicopters and maritime patrol aircraft. In addition to surveillance, MDUSV has the potential to add offensive capability to a surface action group (SAG). Multiple unmanned pickets, placed forward of a SAG, could provide targeting information and perform multi-axis attacks against an adversary.
The working model for MDUSV operations is “sparse supervisory control,” meaning it receives mission updates and orders from a human operator and executes them with minimal supervision. Tasks may include searching for submarines, scouting ahead of a surface force, shadowing a threat vessel, or searching for mines. Currently, the concept of operations is undefined.
Before technical concepts become operational realities, several challenges should be considered. First, MDUSV is a vessel. The technologies that will make it effective are in various stages of development, and too numerous for MDUSV to carry. An exploration of which capabilities most improve operational effectiveness is essential. Second, while superior technology is necessary, alone it is not sufficient. Operational commanders must employ USVs with thoroughly tested tactics, techniques, and procedures (TTPs) to make them effective surface warfare platforms. USVs are entirely new to the U.S. Navy, and no historical data exists for their use in combat. Modeling and simulation are therefore the best means to explore concepts and systems that are now only theories and prototypes.
After simulating 29,000 surface battles, the results of a recent experiment at the Naval Postgraduate School (NPS) are clear: Unmanned surface vehicles can give surface forces a decisive advantage. On average, the addition of MDUSV to a surface force tripled the probability that U.S. forces would be the first to fire a salvo of cruise missiles at the enemy in the simulation. This improvement is the result of the extended sensor range that TALONS can provide. At its maximum altitude of 1,500 feet, the visual and radar horizons are extended to 44 and 47 nautical miles, respectively, giving surface forces persistent, extended sensor coverages that aircraft cannot provide. Further study also showed that these systems, if able to share sensor data with ships, do not need to be armed to make an impact.
These insights came from computer-based modeling and simulation and a state-of-the-art technique known as “data farming.” NPS uses efficient experiment designs to explore topics critical to the Navy. In the case of MDUSV, NPS explored a wide range of potential designs, and evaluated the ways in which they can improve the combat effectiveness of surface forces.
The Value of Simulation
Before the Navy uses any system inwartime, it must be tested at sea—the ultimate proving ground. However, real-world testing is expensive. Materials and manpower limit the number of real-world experiments engineers can perform. Therefore, NPS used modeling and simulation to direct physical research and development. To be clear, these are not complete replacements for real-world testing. Computer-based experimentation, no matter how accurate, is an abstraction that will never fully capture the complexity of the maritime domain, but physical experiments and computer simulation can exist symbiotically. Each feeds lessons to the other, and the result is a rigorously and efficiently tested system delivered to warfighters.
While the Department of Defense extensively uses unmanned systems, these have been remotely controlled unmanned aerial vehicles (UAVs) supporting ground operations. Furthermore, no U.S. warship has fired antiship cruise missiles (ASCMs) in anger against another ship since the USS Simpson (FFG-56) sank an Iranian missile boat in 1988. To fill this data vacuum, NPS ran tens of thousands of simulated battles to guide the design and experimentation process.
To explore MDUSV design, NPS used new software that the Naval Surface Warfare Center, Dahlgren Division, developed to simulate combat in the maritime domain. Therefore, details such as emissions control (EmCon) and ship stationing are built-in.
The NPS approach to simulation, data farming, is a deliberate process to develop a simulation and its inputs to answer research questions. Data farming is in contrast to “data mining,” which uses existing bodies of observational data from the real world. Real-world data has drawbacks. Often it is biased in ways that are unknown to the analyst, due to factors such as faulty sensors or poorly trained observers. It also can contain missing values that reduce the predictive power of many statistical analysis techniques. In the case of MDUSV, very little real-world data exists. Data farming provides valuable insights to guide future research and development.
Much as a farmer decides what to harvest before beginning to plant, NPS decided what to analyze before beginning to collect data. This involved choosing an appropriate measure of effectiveness for MDUSV in surface warfare. The choice was whether the Blue force was the first to fire a salvo of cruise missiles at the Red force.
Designing the Simulation
This study explored the design and surface warfare employment of MDUSV under the operational control of manned ships in wartime. In the underlying scenario, hostilities were underway. The threat of enemy attack was imminent and weapons release was authorized.
First, the simulation varied active and passive sensor ranges, representing possible TALONS altitudes, and whether MDUSV were armed with ASCMs. It also explored tactical factors such as formation, dispersion, and EmCon.
Three scenarios were tested in conjunction with weapons tactics instructors at the Naval Surface and Mine Warfighting Development Center and the Afloat Training Group, Pacific. The first scenario was a base case in which a SAG operates without MDUSV support. In the second scenario, the SAG commander had intelligence that allowed him to define a narrow threat sector. MDUSVs were deployed farther ahead of the force on a narrow front. In the third scenario, the SAG commander was unable to define a narrow threat sector, and had to spread MDUSVs and manned ships across a wider area.
Implementation and Analysis
NPS used the Hamming supercomputer to simulate nearly 30,000 surface battles, in which nine design factors and tactics were varied. Based on the presence of MDUSV alone, Blue tripled its probability of being first-to-fire from 19 percent to 56 percent. Even though a real SAG would likely have helicopters embarked, helicopters have limited endurance. Further, the use of a helicopter in a conflict poses risk to human pilots, especially if the enemy is equipped with air defense systems. Given the long endurance of MDUSV and its autonomous nature, MDUSV represents a worthwhile investment for the surface force. Analysis shows a break point at an MDUSV passive sensor range of 36 nautical miles. With this range or greater, Blue was first-to-fire in 81 percent of the design replications.
Arming MDUSV had minimal impact on first-to-fire performance because the MDUSVs in the scenario worked together with destroyers equipped with ASCMs. As previously shown, first-to-fire in each battle was driven by scouting—who saw whom and fired first. Because detecting the enemy is a necessary condition to shooting him, equipping MDUSV with over-the-horizon sensors should be the primary concern. This allows the missile shooters of the surface and air forces to fire without emissions from their own sensors, greatly increasing their stealth and survivability.
Analysis of EmCon policy yielded inconclusive results. When equipped with MDUSV, the least restrictive EmCon policy—always active—had a first-to-fire probability of 73 percent. This was 30 percent higher than any other policy. A commander’s choice of EmCon is a delicate one, however, and based on a wide range of factors outside of the experiments. Emitting constantly can make a force vulnerable to counter-detection by the enemy. What other enemy forces may be in the area? Will the enemy shoot based on counter-detection of active sensors? How else may the SAG be vulnerable if active emissions are detected, and the SAG is located? These are questions whose answers were beyond the scope of this research, but they should be asked in future studies.
Formation and force dispersions had an insignificant effect on first-to-fire probability. Pending further study, the recommend tactical action is simple: Place MDUSVs along the threat axis, spaced such that they have coverage across as wide an azimuth in the threat sector as possible. For the purposes of surface warfare, this appears to be the most prudent tactical decision.
This study shows the decisive advantage MDUSV provides is its ability to scout ahead of the force. The force that can first detect, effectively target, and engage its enemy is the victor. Given the potential improvement in combat capability, MDUSV represents a worthy investment for the Navy. With a tether height greater than 1,000 feet, a capable passive sensor, and a network shared with missile-armed platforms, this technology promises to provide a significant warfighting advantage.
1. Admiral John Richardson, U.S. Navy, “The Future Navy,” White Paper, Office of the Chief of Naval Operations (May 2017), 8.
2. Defense Advanced Research Projects Agency, “ACTUV Unmanned Vessel Helps TALONS Take Flight In Successful Test,” www.darpa.mil/news-events/2016-10-24.
⎯ Lieutenant Tanalega is a graduate student studying operations research at the Naval Postgraduate School. He previously served on board the USS John Paul Jones (DDG-53) and the USS Dewey (DDG-105).