ON THE HORIZON: LOGISTICS DRONES PROMISE TO LIGHTEN THE LOAD OF BATTLE
By Mark Butkiewicz
Unmanned aerial systems (UASs) of all shapes and sizes seem to be everywhere these days, as users continue to find countless new applications in a wide range of industries and fields. And the battlefield is no exception. These systems—commonly referred to as drones—are being increasingly used by the U.S. military for everything from intelligence, surveillance, and reconnaissance (ISR) to aerial refueling to cargo transport to armed attack. Recently, the U.S. Navy and Marine Corps have been investigating the use of large multirotor aerial platforms that can provide the Warfighter with assured battlefield resupply for the “last mile” in a logistics hub-and-spoke distribution model. As such, these platforms require specialized capabilities—including payload capacities ranging from 50 to 500 lbs—that differ from those of most other rotor-driven drones in the skies today.
MILITARY LOGISTICS DRONES: AVERAGE DRONES NEED NOT APPLY
Multirotor military logistics drones exist in a kind of gray area when it comes to cost, size, capability, and life-cycle considerations. When many people envision these systems, they think of small and relatively “expendable” consumer-grade toys or hobby equipment. And while it’s true that this class of drone is not exceedingly expensive (representing a fraction of the cost of much larger existing UAS platforms), it is also not disposable (especially compared to some of the single-use drones being investigated for future UAS swarming missions). Rather, military logistics drones are considered “attritable.” That is to say, developers and analysts must trade the traditional aircraft engineering design aspects of reliability and maintainability (and survivability) for that of low cost, while still providing reuse capability.
Logistics drones are also often in a class by themselves when it comes to size. Though significantly larger than most of the camera-equipped handheld drones the military has been deploying to look around a corner or over a hill in support of ISR missions (see Figure 1), logistics drones are also much smaller than many of the “full-size” UAVs that the military currently has in, or is preparing to send to, the battlefield (see Figure 2).
What is not unclear with military logistics drones is the obvious benefit that they promise to provide to the Warfighter. The ability to resupply combat personnel at a moment’s notice means they can potentially shed pounds of supplies and equipment that they would normally have to carry or otherwise transport from their base of operations. Warfighter fatigue can thus be reduced; and Warfighter endurance, maneuverability, operational speed, and lethality can be enhanced. Furthermore, the ability to augment other air and ground logistics transport assets with relatively low-cost and unmanned vehicles promises to provide commanders with added flexibility and decreased risk to personnel during resupply.
FROM TOILET PAPER TO BULLETS: LOGISTICS WINS WARS
Ancient Chinese military strategist Sun Tzu once wrote, “The line between disorder and order lies in logistics” . More recently, business expert Tom Peters added, “Leaders win through logistics. Vision, sure. Strategy, yes. But when you go to war, you need to have both toilet paper and bullets at the right place at the right time. In other words, you must win through superior logistics” .
Indeed, the crucial role that logistics has played, and continues to play, in the success of the U.S. military cannot be overstated. And ultimately, that role always comes down to the individual Warfighters. Do they have what they need when they need it? And equally important, are they carrying anything they don’t need that may limit their agility and effectiveness? It’s no wonder then that the military continues to invest significant amounts of time, effort, and money in trying to shave even a few ounces off the load that Warfighters must carry into combat.
In addition to their personal body armor, weapon, and ammunition, Warfighters generally must carry enough food and water to sustain them until they can be resupplied (often for at least several days). And that doesn’t even count any specialized equipment that they must include to conduct a mission. If these personnel, however, are given the ability to be regularly resupplied by drones, they can potentially shed pounds of their daily supplies.
And it’s not just food, water, and ammunition that logistics drones can potentially deliver at will. Spare parts, mission-specific tools, and other relatively heavy equipment (such as portable generators) can be delivered to remote locations after Warfighters reach a mission objective or checkpoint. Figures 3 and 4 show an example of a logistics drone, called the Tactical Resupply Vehicle (TRV)-150, which is currently being developed in collaboration with the U.S. military, Malloy Aeronautics, and the SURVICE Engineering Company.
COTS vs. COTS+T
To most quickly and efficiently get these logistics drone technologies onto the battlefield, military acquisition leaders are increasingly recognizing the multiple benefits that leveraging existing commercial off-the-shelf (COTS) technologies can have over attempting to develop new drone technologies from scratch. One of the most important of these advantages, of course, is cost. Market demands have helped commercial drone developers be able to improve basic drone capability and performance at a rapid pace, and taking advantage of this progress makes financial sense for the military. There is also great benefit in being able to tap into the existing, robust manufacturing infrastructure found in the commercial sector. In short, when it comes to basic drone development and production, the military is trying not to “reinvent the wheel.”
That said, COTS drones are not typically designed with specific military applications in mind and thus rarely meet all of the unique requirements that the military often has. So, military leaders have also increasingly adopted the practice of taking an existing COTS platform and adding a “tactical veneer”. This customized approach—referred to as COTS+T—takes advantage of the low-cost COTS platform while also adding the necessary military enhancements to meet the specialized needs of the Warfighter.
Of course, as the prevalence and effectiveness of military logistics drones continue to grow, so do the countermeasures that hostile forces will likely take against them. Quite frankly, survivability isn’t something many people associate with drones, especially when they think of the small commercial-grade models used by hobbyists. However, survivability considerations can and should be applied to military logistics drones. And once again, customization is a key principle.
Developers and analysts must combine many of the traditional aircraft survivability considerations often used for other military aircraft while also recognizing that these platforms—though unmanned—are closely connected to the personnel they support. Thus, logistics drone survivability should be considered holistically, where the drone is treated not only as an individual battlefield asset but also as a “component” of a larger, interdependent system supporting and protecting the Warfighter on the ground. And if it comes to potentially competing priorities of these components, the Warfighter must have precedence.
Because survivability is a combination of susceptibility and vulnerability, both areas need to be considered as multirotor logistics drones are developed, analyzed, and tested. Figure 5 illustrates the traditional survivability layers (including both susceptibility and vulnerability considerations) as applied to a logistics drone-Warfighter partnership.
The initial survivability layer—or survivability objective—is, of course, for the drone system not to not be seen (or detected) at all by a threat. To support this objective, a variety of means and measures (as illustrated in the outside layer of Figure 5) can be used, including “stealthy” material composition and airframe shaping, as well as visual, thermal, acoustic, and radar signature management.
Moving inward in the figure, the next survivability objective is for the drone not to be acquired if seen or detected by a threat, such as through the use of signal jamming and smoke obscurants. If the drone is acquired, the next objective is not to be hit, such as through the use of various countermeasures, infrared (IR) decoys, smoke obscurants, and counterfire. If the drone is hit, the next objective is not to be penetrated, which is often achieved via armoring.
Finally, if penetrated, the last survivability objective is for the drone-Warfighter partnership not to be killed. For the drone itself, this objective may come through redundant components or systems (or platforms); for the Warfighter, this objective may come through medical evacuation and/or treatment.
In general, the analysis of logistics drone platforms follows the same basic “ABCs” of vulnerability reduction as any aircraft platform. Namely:
- A – Armor
- B – Bury
- C – Concentrate
- D – Duplicate (and Separate)
- E – Eliminate
- F – Fire Protect.
While armoring a small logistics drone may be impractical in many instances, there may be cases for limited ballistic shielding of key subcomponents that are especially critical for continued operation. In addition, burying components (e.g., using less critical and/or redundant components as shielding) and concentrating areas that are critical to flight (e.g., the flight controller) are proven vulnerability reduction techniques that apply to multirotor drones as much as manned aircraft. Likewise, duplication (and the corresponding separation of redundant elements) is a standard vulnerability reduction technique easily employed by multirotor drones. From a reliability standpoint, most logistics (and other) drones incorporate more motors and props than are necessary to maintain flight, thus allowing one or more motors/props to become disabled and allow continued safe operation.
Elimination of unnecessary items is a vulnerability reduction technique often forgotten in survivability analysis, but it is an especially important principle in any aircraft that has strict limitations in payload capacities and operating ranges. Thus, it is important for developers and analysts to look at each component and subcomponent of a drone design and ask the question of whether it is essential for operation of the drone in performing its mission. If the answer is no, that component/subcomponent should be removed.
Finally, fire remains one of the leading contributors to the loss of aircraft of all types. While fuel has always been a primary worry for manned aircraft, the current lithium-ion batteries used on high-performance multirotor drones with electrical drivetrains are also highly sensitive to ballistic impact. Battery cells can heat up, ignite, and then ignite adjacent cells, leading to a cascading fire throughout the platform.
To help reduce this threat, the use of intumescent coatings is currently being investigated, as is the use of solid-state batteries. Prototype solid-state batteries have demonstrated twice the energy density of other batteries and a substantially improved rate of charging/discharging. Moreover, unlike many vulnerability reduction techniques, the use of these batteries doesn’t come with weight and cost penalties. Thus, they have the potential to improve not only the ballistic resilience of a logistics drone but also its range and payload capacity.
Notwithstanding the aforementioned vulnerability reduction techniques, vehicle-level survivability in logistics drones is less of a factor in mission effectiveness than the overarching operational-level survivability in which the drones are a part. Admittedly, most ballistic impacts are overmatching threats to a drone the size of a logistics drone (and smaller), so the way in which these systems are employed and the likelihood of engagement ultimately play a larger role in overall system performance on the battlefield.
At the operational level, survivability of the Warfighter and not the drone is the highest priority. While one goal is certainly to assure the drone can complete its mission, in most instances delivery of the payload takes precedent over risk to the vehicle. This feature of (attritable) logistics drones thus provides commanders the ability to put them into contested, high-risk airspace in a way that more expensive and manned assets cannot generally be employed.
That said, the commander must still maintain awareness of drone asset losses and how they might affect longer term operational tempo should fewer assets be available. Therefore, as mentioned, employing logistics drones must be done in a way that minimizes the chances they can be engaged and killed and maximizes their ability to continue to provide Warfighters with critical supplies in future missions.
In terms of susceptibility, another one of the benefits of electric multirotor logistics drones is that they are relatively small and quiet compared to a larger drone or manned aircraft. Without the heat of a combustion engine, they are also relatively cool in the IR spectrum. Accordingly, recent integrated test activities involving the use of logistic resupply drones at night have demonstrated just how close these drones can approach a landing zone before being detected from the ground. Further field testing and the development and validation of concepts of operations (CONOPS) for logistics drones are expected to continue to identify strategies for optimizing how and when these assets should be deployed.
If, as has been said, logistics wins wars, then the use of logistics drones is sure to be an increasingly vital tool in battle to provide assured, sustained logistics resupply. Affordable, capable, and easily deployable—logistics drones represent a technological leap-ahead and force multiplier in assuring that the U.S. Warfighter always remains equipped, agile, and successful. To continue to maximize the effectiveness of these unique platforms, developers and analysts must continue to view drone survivability holistically, treating the drone and the Warfighter as interdependent components of a larger system, maintaining a balance between cost and capability, and optimizing both platform-level and operational-level survivability to provide the most robust, most capable, and most useful assets possible.
ABOUT THE AUTHOR
Mr. Mark Butkiewicz is the Vice President of Applied Engineering and manages the Applied Technology Operation for the SURVICE Engineering Company. He has more than 35 years of experience in defense and aerospace research, development, and systems engineering; and he is currently overseeing the Unmanned Logistics System-Air (ULS-Air) program development activities for the company. In addition, he has led efforts on numerous Small Business Innovation Research (SBIR) grants. Previously, Mr. Butkiewicz worked as a lead design engineer for the Space Systems Division of General Dynamics. He holds three U.S. patents and a B.S. in mechanical engineering from the University of Maryland.
 Tzu, Sun. The Art of War. Translated into English by Lionel Giles, 1910.
 Peters, Tom. “Rule #3: Leadership is Confusing as Hell.” Fast Company, March 2001.