Why Cheap Drones Changed the Weapons Math

Introduction

The strongest argument for directed energy weapons is not that they make conventional air defence obsolete. It is that they may change the price of defending against cheap drones. A small unmanned aircraft can cost thousands or tens of thousands of pounds, while the missile used to stop it may cost hundreds of thousands or millions. High-energy lasers and some microwave systems promise a different cost structure: once the system is bought, powered, cooled and aimed, each extra shot can be close to the cost of electricity rather than the cost of a new interceptor missile. The UK Ministry of Defence says its DragonFire laser typically costs less than £10 to operate per shot, while the Royal Navy describes the same system as a low-cost layer for engaging drones, missiles and aircraft at the speed of light. [GOV.UK]GOV.UKAdvanced future military laser achieves UK firstAdvanced future military laser achieves UK first

That headline figure matters, but it is not the whole bill. “Cost per shot” is best understood as the marginal cost of firing, not the full cost of owning, deploying and protecting a directed energy weapon. The drone defence argument is therefore strongest when it is modest: lasers and related systems can help preserve expensive missiles for harder targets, deepen defensive magazines, and reduce the cost-exchange advantage enjoyed by attackers using cheap drones. They are not a universal replacement for missiles, guns, electronic warfare or layered air defence.

Why missiles can be a costly answer to small drones

The cost problem begins with an uncomfortable mismatch. Modern air defence missiles were often designed to defeat fast aircraft, cruise missiles, ballistic missiles or other high-value threats. Cheap drones invert that logic. They can be launched in volume, used to probe defences, or sent against targets whose political or operational value forces defenders to respond. The defender may win the engagement and still lose the economic contest if each successful intercept consumes a scarce, expensive missile.

The Red Sea made this issue visible to a mainstream audience. CSIS noted that news coverage repeatedly highlighted cases such as the US Navy using a roughly $2 million Standard Missile-2 against drones reported to cost about $2,000, while also warning that this simple comparison can be misleading because the value of air defence includes the ship, crew, cargo and wider mission being protected. [CSIS]csis.orgCost and Value in Air and Missile Defense InterceptsCost and Value in Air and Missile Defense Intercepts… That caveat is important: a missile is not “wasted” if it prevents a drone from damaging a destroyer or merchant ship. But repeated cheap-drone attacks can still drain magazines, budgets and production lines.

Ukraine has sharpened the same lesson. CSIS analysis of Russian strikes found that Shahed-type one-way attack drones are less efficient than some missiles in terms of warhead delivered, but they impose a valuable tax on defenders: they force air defence crews to react, consume interceptors, and can create openings for other weapons in a mixed attack. The same analysis notes that using missiles such as NASAMS or Patriot interceptors against one-way attack drones can produce a large loss of value, especially when production lines are limited and modern interceptors take time to replace. [CSIS]csis.orgCalculating the Cost-Effectiveness of Russia’s Drone StrikesCalculating the Cost-Effectiveness of Russia’s Drone Strikes…

This is the narrow but powerful opening for directed energy. A laser that can defeat a drone at short range does not have to beat a missile on every military measure. It only has to take enough cheap, slow or fragile targets out of the missile queue. RAND frames this as a way to relieve pressure on stretched munitions stocks and free kinetic weapons for other purposes, especially in environments such as Ukraine and the Red Sea where cheap drones and rockets are being used in volume. [RAND Corporation]rand.orgCorporation Directed Energy: The Focus on Laser Weapons Intensifies | RANDRAND CorporationDirected Energy: The Focus on Laser Weapons Intensifies | RAND…

What low energy cost does and does not include

The phrase “£10 per shot” is easy to misunderstand. It usually refers to the operating energy needed to fire the laser, not the acquisition cost of the weapon, the ship or vehicle carrying it, the sensors that cue it, the operators, maintenance, spares, training, test ranges, integration work, software updates, or the power and cooling infrastructure that allows repeated firing.

The Congressional Research Service makes the distinction clearly. It states that high-energy lasers may offer lower logistical requirements, lower costs per shot and deeper magazines than traditional munitions, provided there is sufficient power. For many solid-state lasers, the shot cost is essentially the cost of the electrical power needed to fire. [Every CRS Report]everycrsreport.comEvery CRS Reportwww.everycrsreport.comEvery CRS Reportwww.everycrsreport.com That is a real advantage, but it is a marginal-cost advantage. It tells us what the next shot costs after the weapon is already in place and working.

DragonFire shows both sides of the argument. The UK Government says a 10-second firing is roughly comparable in energy cost to running a regular heater for an hour, with operating cost typically under £10 per shot. But the same public programme exists because years of research, engineering and industrial integration were needed before any shipboard deployment could be contemplated. [GOV.UK]GOV.UKAdvanced future military laser achieves UK firstAdvanced future military laser achieves UK first In 2025, Reuters reported a £316 million contract to develop and supply DragonFire systems for the Royal Navy, underlining that cheap firing does not mean cheap procurement. [Reuters]reuters.comUK beefs up Royal Navy counter-drone tech with $413 million laser contractThis initiative is part of Britain's efforts to enhance its naval defenses, particularly against drone threats. The DragonFire system is…

A useful way to read cost-per-shot claims is to split them into three layers:

Only the first layer is captured by the most eye-catching figures. The second and third layers decide whether a laser is genuinely affordable in service.

Magazine depth and sustained defence

The second major advantage is magazine depth. A ship or ground battery can only carry so many missiles. Once those cells or launchers are empty, rearming may require withdrawal, port access, transport, specialised handling and time. A laser does not carry a physical round for each shot. If it has power, cooling capacity and a functioning beam director, it can keep engaging.

That is why official and analytical sources often pair cost per shot with “deep magazine” or “virtually unlimited firing power”. GAO’s technology spotlight says directed energy weapons could be less expensive per shot and have virtually unlimited firing power because they use energy rather than bullets or missiles, while also noting shorter range and weather sensitivity. [GAO]gao.govScience & Tech Spotlight: Directed Energy Weapons | U.S. GAOScience & Tech Spotlight: Directed Energy Weapons | U.S. GAO… CRS similarly links lower shot cost to deeper magazines, assuming sufficient power supply. [Every CRS Report]everycrsreport.comEvery CRS Reportwww.everycrsreport.comEvery CRS Reportwww.everycrsreport.com

For drone defence, this matters as much as price. A defender facing ten or twenty drones may not merely worry about the cost of ten or twenty interceptors. The defender also worries about whether enough interceptors remain for the next salvo, or for a faster and more dangerous missile hidden inside the same attack. A laser layer can, in principle, spend electrical energy on the lower-end targets and preserve missile inventory for threats that need missile performance.

There is a practical catch: lasers are not machine guns made of light. They may need dwell time, meaning they must hold the beam on a vulnerable point long enough to damage a wing, casing, motor, sensor or control surface. That makes the number of engagements per minute depend on target range, beam power, weather, aim-point stability, target material and the desired effect. A “deep magazine” does not automatically mean unlimited simultaneous capacity.

Why cheap drones are a particularly suitable target

Low-cost drones are not all easy targets, but many have features that make them attractive for directed energy. They may be relatively slow, lightly built and dependent on exposed sensors, propellers, control surfaces, antennas or electronics. A laser does not need to blow up the whole aircraft if it can make the drone lose lift, navigation or control.

The Royal Navy’s description of DragonFire is built around exactly this role: a shipboard laser added to existing air defence weapons, not a replacement for all of them. It says DragonFire will join systems such as Sea Viper and Sea Ceptor, and describes a laser burst costing no more than £10 while engaging drones, missiles and aircraft at light speed. [Royal Navy]royalnavy.mod.uk240412 powerful laser to be installed on royal navy warship by 2027Royal NavyPowerful laser to be installed on Royal Navy warship by 2027… The UK Parliament’s International Relations and Defence Committee also identifies “cost asymmetry” as a problem in taking down cheaper drones with expensive missiles, and points to DragonFire as a possible cost-effective counter-drone measure if procurement reforms and technical challenges are met. [UK Parliament]publications.parliament.ukUK Parliament House of CommonsUK ParliamentHouse of Commons - Ukraine: a wake-up call - International Relations and Defence Committee…

Israel’s Iron Beam illustrates the same strategic logic in a different defence ecosystem. Reuters reported in September 2025 that Israel’s Ministry of Defence said Iron Beam had completed testing and would be ready for operational use, with laser interception costs described as negligible compared with current rocket interceptors costing at least $50,000 each. The system is intended to complement Iron Dome, David’s Sling and Arrow, not replace them. [Reuters]reuters.comOpen source on reuters.com.

That word “complement” is doing a lot of work. The drone defence argument is strongest where directed energy is assigned to a lower layer: small drones, some rockets, mortars or short-range aerial threats within line of sight. It is weaker when stretched into claims that lasers can cheaply solve all air and missile defence problems.

The cost-exchange trap

The simplest version of the argument says: “Why fire a million-pound missile at a cheap drone when a laser shot costs a few pounds?” That is a fair question, but it can become a trap if it treats all intercepts as interchangeable.

Air defence is not only a financial calculation. It is a reliability problem under conditions where one failure can matter more than many cheap successes. Modern War Institute makes this point sharply: lower-cost systems are essential for handling volumes of cheap threats, but high-end interceptors remain necessary for the most dangerous weapons and for parts of the air defence architecture where failure is unacceptable. [Modern War Institute]mwi.westpoint.eduOpen source on westpoint.edu.

CSIS makes a similar warning about Red Sea cost comparisons. The price of the interceptor and the price of the drone are not the only values in the engagement. A missile may protect a warship, a civilian crew, an oil facility, a port, or a political commitment. [CSIS]csis.orgCost and Value in Air and Missile Defense InterceptsCost and Value in Air and Missile Defense Intercepts… The correct lesson is not that expensive interceptors are foolish. It is that defenders need cheaper layers so they do not have to use expensive interceptors for every low-end threat.

This is where directed energy has its most disciplined role. It improves the defender’s menu of choices. Instead of deciding between “ignore the drone” and “spend a scarce missile”, a force may be able to use a laser, gun, jammer or low-cost interceptor first, while keeping missile systems ready for higher-speed, longer-range, all-weather or more lethal threats.

The hidden limits behind a cheap shot

Directed energy’s low marginal cost only matters when the shot is tactically possible. Lasers need line of sight. They can be degraded by rain, fog, dust, smoke, turbulence and other obscurants. They also need enough power and cooling to sustain engagements. CRS notes that rain, fog, obscurants, size, weight, power and cooling requirements can limit range and beam quality, whereas traditional weapons are not affected by those factors in the same way. [Every CRS Report]everycrsreport.comEvery CRS Reportwww.everycrsreport.comEvery CRS Reportwww.everycrsreport.com

This is a major reason lasers are often discussed as part of layered defence rather than as stand-alone shields. A ship may still need missiles for threats beyond the horizon, guns for close-in engagements, electronic warfare for drones vulnerable to jamming, and decoys or passive measures to complicate targeting. A ground site may need several laser units to cover different arcs, plus conventional interceptors for bad weather, saturation attacks or targets that cannot be held in the beam long enough.

There is also the question of deployment density. A laser’s shot may be cheap, but if each system is expensive and covers a limited area, the total cost of protecting a long border, dispersed base network or wide maritime route can still be high. Israeli reporting on Iron Beam has raised this point directly, noting that the cost of “pulling the trigger” may be low while each laser system costs substantial sums and broad coverage requires major investment. [The Jerusalem Post]jpost.comOpen source on jpost.com.

The practical lesson is that cost per shot should be treated as a necessary but insufficient metric. A directed energy weapon is attractive when the full system can be placed where drones actually appear, engage them reliably under local weather and terrain conditions, and integrate with the rest of the defensive network.

The real drone defence argument

The best case for directed energy is not that it produces magic firepower. It is that it can shift the defender’s economics at the bottom end of the threat spectrum. Cheap drones changed the weapons math because they made it possible to impose repeated costs on sophisticated militaries. Directed energy offers a way to push back: spend electricity rather than missiles where the target is suitable, preserve interceptor stocks, and make mass drone attacks less financially attractive.

That argument is strongest when it stays specific:

The drone defence argument is therefore compelling but bounded. Directed energy weapons are most useful not because every shot is almost free, but because the next suitable shot may be vastly cheaper than the next missile. In a world where cheap drones are used to exhaust expensive defences, that difference can matter strategically.

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Endnotes

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Additional References

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   DragonFire laser cost per shot drone defense DragonFire: The UK’s $13 Laser Weapon That Shoots Down Drones Instantly India Today Global...

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   Britain successfully tests the DragonFire Laser weapon. The laser can shoot down drones and missiles...

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   Watch This UK Laser Destroy Drones Instantly...

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   Iranian drones: Cheap to produce, costly to defend against...

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