Into the Pickle Barrel: How Thinking About Precision as a System Can Expand the Munition Stockpile
The camera from a small drone steadies on a Russian T-72 tank somewhere in Ukraine. Slight movements can be seen in the video as the Ukrainian operator makes final adjustments to the drone’s position. Then, release. The munition – a grenade with a 3D-printed plastic fin assembly – falls into the frame and quickly disappears. Then a flash, a gray puff of smoke, and roaring fire erupt from the open hatch. Bullseye. Seconds later, the ammunition inside the tank “cooks off”’ with violent spurts of orange flame. A raft of similar videos depicts Ukrainian forces precisely dropping small munitions inside Russian trenches, foxholes, and even through the sunroof of a car. While these videos are essentially a highlight reel and are not a representative sample of all attacks, they show a real capability to drop repurposed munitions from small commercial drones.
On the battlefields of Ukraine, many Western-provided munitions like the Javelin anti-tank missile and high mobility artillery rocket systems (HIMARS) have become household names. But some systems attracting the most attention are modified, commercial off-the-shelf quadcopter systems like the Chinese-made DJI Mavic armed with common infantry munitions. Small drones are proving effective on the modern battlefield because they can drop small munitions with precision, remain difficult to defend against, and are cheap. Nearly inaudible and challenging to locate visually at altitude, their small size helps them remain masked from most air defense systems and get close to a target, minimizing the variables affecting the precision of ballistic munitions.
The problem with precision munitions today is that they are highly manufactured, require advanced chips and materials, and therefore are harder to replenish when stocks are depleted than unguided or “dumb” munitions. Countermeasures like camouflage, decoys, and electronic warfare help adversaries deplete precision munition stocks. Ukraine is showing the world that cheap, commercial drones combined with “dumb” unguided munitions can reliably achieve the same effects as much more expensive, precision-guided munitions.
The Pentagon should re-evaluate its emphasis on the requirement for guided munitions to achieve precision. Rather than exclusively acquiring exquisite munitions that demand a unique targeting solution and logistical chain to achieve precise effects, the delivery of precision firepower should be considered holistically as a product of a system and acquired through a spectrum of requirements necessary to achieve the desired outcomes. Simply put, if unguided munitions can achieve satisfactory precision with the addition of a precision guidance kit or an alternative delivery method, such a solution should be resourced prior to an exquisite, purpose-built one.
The Need for Precision
After years of attempts and hundreds of unguided weapons, the Thanh Hoa Bridge in North Vietnam finally fell to two laser-guided munitions in 1972. Since then, the U.S. military’s love affair with precision or “smart” guided munitions has blossomed, followed by the rest of the world’s. Precision munitions have become synonymous with great power and prestige. Great power competitors’ long-range weapon capabilities have increased the risk to operating forces and necessitated a shoot first, kill first requirement. As a result, countries worldwide have tried to either indigenously develop their own precision munitions or purchase them through foreign acquisition. In particular, the United States has built a vast inventory of guided munitions ranging from precision guidance kits mated to conventional munitions like aerial bombs or artillery rounds, infantry rocket systems like the Javelin, and expensive cruise missiles like the Tomahawk. As the progenitors of Western precision weapons, the United States established compatibility and employment standards for its allies.
A guided munition provides the launching platform with the advantages of less restrictive release conditions and can give greater standoff from the target—for example, ballistic releases at altitude versus a diving attack. A 1974 RAND study detailed the effects of various enhancements to the ballistic release of an aerial munition, including the addition of “a pulsed laser beam and guidance system [that] could…home in on the reflected laser light” and correct the flight path of the weapon to the target if released from a point in the air other than the single physically possible ballistic release point. Before modern guidance kits, aircraft used special tactics and more primitive technology to achieve precision. For aircraft, the most precise delivery for unguided ordnance is a 90-degree delivery angle (nadir drop), which minimizes vertical error and horizontal travel. For this reason, World War II dive bombers like the famous German Stuka were equipped with dive brakes to achieve near-vertical descents while dropping bombs. But steep descent profiles have major drawbacks, requiring the attacking aircraft to maintain a predictable flight path while increasing its exposure to ground fire and making aircraft more susceptible to air defenses.
In 1943, the gyro-stabilized Norden Bombsight was the flagship of precision bombing, with claims it could “drop a bomb into a pickle barrel.” Proponents asserted a remarkably accurate ability to drop bombs within 75 feet in ideal conditions. Actual wartime employment was over 1,200 feet outside of the target area and further compounded when the entire formation released off the lead aircraft instead of their calculated release point. The lack of real precision resulted in most bombs missing their targets and inflicting mass civilian casualties.
The 1974 RAND study noted that unguided munitions released using a manual bombsight required 21,000 bombs to destroy 100 targets or 210 bombs per target. According to the same RAND study, when a ballistic computer was introduced to calculate the release, the munition requirement lowered to 40 bombs per target. Equipping a bomb with a laser seeker and guidance kit took just 100 bombs to destroy 100 targets: a one-to-one ratio. This pursuit of precision resulted in a focus on guided or steerable munitions like the Paveway I (GBU-1), first used in Vietnam. With the ability to strike precisely within 20 feet, the Paveway series remains in use today. Precision guidance kits are a relatively cheap way to make unguided warheads precise because instead of designing a whole new weapon, a special kit can be bolted onto an existing bomb.
Air forces found that they could deliver ordnance precisely while maintaining acceptable risk. Risk is mitigated by reducing cognitive loads on the employing pilot or bombardier by taking the requirements for the precise delivery of ordnance out of the aircrews’ hands and putting them into the munition. With the munition able to steer post-release and guide itself to either a preprogrammed GPS coordinate or a laser aimpoint, the acceptable release parameters are expanded, reducing the pilot’s workload and risk of groundfire. The effects of guided munitions have been profound. Recently, the U.S. Navy stopped training on dive bombing tactics in portions of its tactical syllabus for the first time since the tactic was introduced during the interwar period because of the availability of precision guidance kits.
Precision is the Product of a System, not a Munition
One of the lessons the war in Ukraine reinforces is that precisely delivered munitions create greater desired effects on the battlefield than a larger quantity of unguided and imprecise weapons. Despite Russia’s quantitative weapon advantage over Ukraine, Ukraine’s effective use of precision munitions like artillery rocket systems and drones, coupled with agile combat principles, is disrupting Russian combat operations. Imprecise munition delivery requires larger quantities to achieve the same desired effect – and likely causes a preponderance of undesired consequences. Russia required large ammunition stockpiles near the frontlines to supply engaged combat units vulnerable to Ukrainian precision counter-targeting, which led to mass casualty events when troops billeted near ammunition depots were struck by Ukrainian forces. Using a combination of special force sabotage within Russia and long-range precision fires, Ukraine effectively shaped the battlefield ahead of major assaults by precisely targeting large Russian weapon caches. However, precision is not the sole property of guided munitions.
In theory, an accurately calculated ballistic release point that accounts for all variables negates the requirement for a guided (steerable) munition, provided the target is stationary or maintains a constant speed and direction if moving. For example, the F/A-18’s mission computers can calculate the winds at the aircraft’s altitude but cannot determine the winds below that will affect the bomb. Instead, the mission computers use a computer model to predict the effect of winds based on the winds at release altitude. While the model improves ballistic accuracy, it is not foolproof. To increase precision, the pilot could place the aircraft in a dive, reducing the flight time of the weapon, horizontal velocities and corresponding error, and the time environmental factors can affect the munition. Fighter jets typically release bombs a few thousand feet above a target when in a dive. When a guidance kit is attached to a bomb, the aircraft can utilize ballistic releases at higher altitudes. The aircraft could be miles from the target – keeping the aircraft safer and nearly guaranteeing a direct hit. Guided weapons also allow for standoff outside ballistic releases or horizontal attack profiles, usually accomplished through powered flight, as with cruise missiles or airfoils for gliding.
But if a weapons platform can come within negligible distances of a target without detection or risk to a human pilot, does that system require a guided munition? The explosion of armed drones has generated significant interest in micro and loitering munitions. Micro-munitions are purpose-built, scaled-down versions of their larger aerial cousins. Examples of these munitions include the Northrop Grumman Hatchet and Raytheon Pyros. Micro-munitions’ development follows a familiar vein and almost all the proposed and prototyped munitions are guided. Unlike current laser-guided or global positioning system bombs, which use precision guidance kits bolted on to the basic unguided bomb, proposed and current guided micro-munitions are not kits leveraging existing munitions like grenades or mortars. Instead, these munitions are purpose-built, making them more expensive and slower to produce than established infantry weapons like grenades and mortars, and there are little to no pre-existing stocks to draw from.
A loitering munition mates a drone with a warhead into a single system. Once the operator finds a target, or perhaps through autonomous guidance, the drone flies into the target and is destroyed along with it. Like micro-munitions or any purpose-built precision weapon, the logistics tail required to buy, build, and field a more complex system made in sufficient numbers is longer and more brittle. For example, the United States began running out of precision weapons during the air campaign against the Islamic State because weapon expenditures exceeded the ability of the defense industry to replenish them and were frequently unnecessarily used. Western defense officials repeatedly noted the shortages of precision munitions on both sides of the war in Ukraine.
Weaponized Drones versus Exquisiteness
The United States did not fully appreciate the threat of small armed drones until it engaged in combat operations against the Islamic State. Iraqi security forces first experienced the new aerial threat that the U.S. Central Command Commander, General Kenneth McKenzie, called the “most concerning tactical development” since improvised explosive devices. During the push to liberate Mosul, the Islamic State launched quadcopters and indigenously built fixed-wing drones to deliver lethal munitions. Videos released by the Islamic State featured drones dropping unguided munitions onto Iraqi forces. Later, drones used by both the Islamic State and Iranian proxies attacked remote outposts occupied by U.S. forces. The United States was not alone: Russia suffered drone attacks from militants in Syria, and French forces were wounded in an Islamic State drone attack with a quadcopter and grenade — the same method Ukraine now employs to target Russian armor and personnel.
Weaponized drones in hotspots worldwide were a harbinger of things to come. Modifying commercial or custom-built drones with available small unguided munitions, like grenades or mortars, allowed militant groups lacking nation-state resources to engage in precise aerial firepower. Numerous defense articles acknowledged the new danger and paradigm shift and referred to it as the era of democratized airpower.
There are two ways in which drones deliver lethal effects. One is a regenerative weapons delivery platform capable of releasing ordnance and returning home for rearming. The other is as a loitering munition. Loitering munitions like AeroVironment’s Switchblade are effective but are specialty items and do not provide regenerative airpower, or the ability to return and rearm using commonly available munitions. This means replenishment for loitering munitions requires sustainable combat logistics that keep pace with consumption in the field since each expended munition requires a drone vehicle and warhead replacement.
The war in Ukraine demonstrates the benefits of precision effects and the ability to maintain agile and light logistics, principles the U.S. military espouses as essential for its distributed maritime operations for a Pacific theater war. Ukraine has burned its stockpiles of guided munitions at excessive rates, especially infantry-borne guided rocket systems. Exercising resourcefulness, Ukraine tapped caches of easily obtained mortar rounds and grenades. It mated its infantry weapons to small drones to harass and target Russian personnel and vehicles near the front lines, preserving precious stores of more costly and harder-to-acquire exquisite precision ammunition. A Ukrainian drone operator stated, “if you can destroy a tank from a Mavic, you’re the best at this war.”
A modern drone contains microprocessors and numerous specialty parts, like optics, requiring more industrial expertise and logistics than steel casings filled with cheap explosives. Each time an explosive is delivered with a loitering or guided munition, the delivery system (fuselage, optics, and flight controls) and warhead must be replaced. A drone that delivers a munition but returns to be rearmed only requires the replacement of the munition. Plus, the ability to use munitions readily found with infantry units simplifies logistics through interchangeability and availability.
The side that is better able to reconstitute over time is the side that can sustain and ultimately win the war. Reconfiguring unguided munitions and augmented precision is more sustainable than exquisite weapon systems whose components cannot be resourced from diversified supply chains.
‘Dumb’ + 3D Printed Fins = Precise Enough
Small drones can get remarkably close to their targets. With low acoustic and visual signatures, decent optics, and a modest payload capacity, they are proving to be a force multiplier for the ground forces that use them. Coupled with the fact that drones are extremely risk-worthy, Ukrainian operators are showing that they can get close enough to a target for a nadir drop. In many cases, nadir drops eliminate the need for a guided munition. Grenades and mortars affixed with plastic stabilizing fins manufactured using 3D printers have proved effective. As evidence, Ukraine released videos of the modified unguided munitions dropped from drones hitting targets with accuracies that rivaled the guided ones. While these public releases are meant to embolden the Ukrainian war effort and increase morale, and therefore may exaggerate the capability, they also demonstrate that these drones and the repurposed munitions they employ are small and light enough to be carried and deployed en masse by infantry units and do not need vehicle support like larger weapons.
Does this mean guided micro-munitions are not needed? No. There are cases where a drone must remain at higher altitudes, or perhaps a target is moving. A quadcopter can hover, making nadir drops possible and simplifying aiming. But in many cases, the quadcopter is low, less than 500 feet above the target. However, larger, fixed-wing drones can remain at higher altitudes – harder to detect with the naked eye and safer from ground fire. In that case, guided munitions may be better suited since horizontal velocities are imparted to the munition from the launch platform, and the flight time allows for greater errors to manifest.
If a dive profile is available for a fixed-wing drone through an artificial pilot, an unguided munition may still be acceptable; it depends on the accuracy of the computer calculation and the target range. Utilizing risk-worthy fixed-wing drones enables scaling this concept to larger munitions. For example, an armed version of the Tracer could deliver larger unguided munitions like 155mm shells or 120mm mortars with dive deliveries. Once a mission is completed, the Tracer would return to a road, maybe utilizing an arrestor hook system, to be quickly captured and rearmed. Also, a forward velocity component associated with fixed-wing aircraft is beneficial for guided munitions like Elbit’s laser-guided mortars against moving targets since the munition will have greater kinetic energy at release, increasing maneuverability and interception envelope. With a nadir drop, the ability to guide onto a moving target is significantly less.
For now, small drones cannot carry large, heavy munitions, but future versions might be able to. Advances in battery technology or hydrogen fuel cells could enable them to carry greater loads and extend their range. 60-millimeter and 81-millimeter mortar rounds are stockpiled by the tens of thousands and would be the ideal choice for pairing with drones. Also, patents exist to turn these mortars into precision weapons. These systems could complement other, more exquisite systems, like the Marine Corps’ Organic Precision Fires system. Ideally, a munition or weapons system is not over-engineered with features that are not required to achieve the effects of the mission – low cost and simplicity are inherent advantages in production.
The Spectrum of Requirements: Unguided, Kit, Exquisite
During the clearance operations in Iraq in 2016, U.S. forces were expending so many Laser Joint Direct Attack Munitions in a target-rich environment that ground commanders received warnings to ensure that targets serviced by these munitions required the use of the weapon. Media reported that the U.S. military was “running out of precision-guided munitions,” which reignited conversations about substituting lower-cost weapons. The Laser Joint Direct Attack Munition is a very capable precision guidance kit with great capabilities against moving targets. Still, it is considerably more exquisite than a normal Joint Direct Attack Munition, and the voracious consumption rate made war planners nervous about the remaining inventory.
Precision effects should not be equated to exquisite precision munitions. Instead, industry and practitioners should view precision as a holistic product of the system and the parameters that system employs. The minimum capability required to achieve the desired effect should be the goal. Employing a weapon system of greater capability against a target that does not require it is wasted capability that a force may have trouble replacing in combat. Risk-worthy systems, like drones mated with artificial pilots, can create conditions where a precision munition is not required to achieve precision effects. Instead, a spectrum of requirements should be applied in which these questions are asked in sequential order: Can the intended precision be achieved with the delivery platform without using a precision-guided munition? If so, utilize the appropriate unguided munition. Next, if effects cannot be achieved with unguided munitions, can they be achieved with a modified unguided munition, perhaps a precision guidance kit, to achieve the appropriate level of precision? A purpose-built munition should only be commissioned if the mission is unable to achieve precision through the other two means.
Military readiness assessments should include an assessment of the ability of the defense industry to reconstitute munitions during conflict. Western governments are concerned with the rate at which their gifted weapon systems are being consumed in Ukraine, straining peacetime industrial bases. If a proxy war can so quickly drain vast stockpiles of precision weapons, how will stockpiles fare in a direct, open conflict? Using a systems-based approach for precision, the United States can more efficiently utilize existing inventories and not over-engineer, averting some logistical headaches in high-intensity warfare.
Trevor Phillips-Levine is a naval aviator and close air support instructor. He holds a Master of Business Administration in aerospace and defense from the University of Tennessee. He also serves as an advisor for weaponized small drone development in a cooperative research and development agreement.
Andrew Tenbusch is an F/A-18 Super Hornet naval flight officer and fellow with the Halsey Alfa Advanced Research Program at the U.S. Naval War College. He is a graduate of the Navy Fighter Weapons School (TOPGUN) and previously served as a carrier air wing integration instructor at the Naval Aviation Warfighting Development Center.
Walker D. Mills is a Marine Corps Infantry Officer training to be an Unmanned Aircraft System Officer. He is also nonresident fellow at Marine Corps University’s Brute Krulak Center for Innovation and Future War and a nonresident fellow with the Irregular Warfare Initiative, a collaboration between the Modern Warfare Institute at West Point and Princeton’s Empirical Studies of Conflict Project.
Dylan Phillips-Levine is an active-duty naval aviator with a tactical air control squadron.
Collin Fox is a U.S. Navy foreign area officer. He is a graduate of the Chilean Naval War College and the Naval Postgraduate School, where his final project on alternative anti-submarine weapons won the John Hopkins Applied Physics Lab Award for Excellence in Systems Analysis.
CORRECTION: A previous version of this article provided the wrong date for the relevant clearance operations in Iraq. They occurred in 2016.
Image: 17th Training Wing Public Affairs photo by Ethan Sherwood