It takes hours to lay a minefield. Why does it take weeks to clear one?

9 August 20268 min readNordhal Defence

U.S. Navy photo by NAVCENT Public Affairs (DVIDS). Appearance of U.S. Department of Defense imagery does not imply or constitute DoD endorsement.

The cost gap

At Nordhal Defence, we are developing expendable underwater drones to neutralise naval mines. This article is about why we think that matters.

Earlier this year, Iran laid naval mines in and around the Strait of Hormuz, a chokepoint that carries twenty percent of the world's oil. Months later, the waterway remains heavily disrupted. Mine clearance is one of the reasons.

It is not the only reason. Insurance, diplomacy, and broader military threats all play a role. But the physical reality of clearing mines is striking on its own: a weapon that costs a few thousand dollars requires an operation costing many times more, tying up some of a navy's most specialised assets for weeks. One widely cited estimate puts the cost of clearing a mine at more than ten times the cost of laying one, and the time required at up to 200 times longer.

The economics are brutal. In 1991, cheap Iraqi mines damaged both USS Tripoli and USS Princeton, a billion-dollar Aegis cruiser. The weapons that hit it cost a few thousand dollars each, and the damage ran into tens of millions. Nothing about this has fundamentally changed since. Naval mines are one of the most effective asymmetric weapons in modern warfare because the attacker gets far more disruption than the weapon costs.

How we clear mines today

There is no single mine clearance system. There are several approaches, each with real trade-offs.

MinesweepingThe oldest method. Towed or unmanned systems simulate the magnetic, acoustic, or pressure signatures that trigger influence mines, or cut the mooring cables of older types. It can cover area relatively quickly, but the trade-off is speed over individual identification: sweeping clears a zone rather than confirming each object before it is neutralised. Several NATO navies have reduced their dedicated sweeper fleets in recent years, shifting toward unmanned and modular systems.

MinehuntingMore precise. A ship uses sonar to locate a mine, then sends a diver or a remotely operated vehicle to identify and neutralise it. The limitation is pace: you find one, confirm one, neutralise one, then move to the next.

Expendable neutralisersSmall, fibre-guided underwater drones that carry a shaped charge. They work well, but each one is consumed in the process. Ship-launched versions typically require specialised handling equipment on a dedicated mothership, and each vehicle addresses a single mine.

Reusable ROVsCarry charges to the mine, place them, and return to the ship. Some can carry multiple charges per sortie, but the process remains sequential: approach, place, withdraw, repeat.

Autonomous underwater vehiclesCan search large areas without a crewed ship directly overhead. Several have been deployed in the Strait of Hormuz. But for many of these systems, finding the mine is only half the job, because a separate vehicle or diver still has to neutralise it.

Helicopter-based systemsKeep the mothership out of the danger zone by delivering expendable neutralisers from the air. A single helicopter mission can carry multiple neutralisers, which is a real advantage, but each neutraliser is still consumed per mine and the approach depends on helicopter availability and weather.

The direction the industry is moving, toward unmanned, distributed mine countermeasures, is right. But a pattern runs through every current method: the final step of identifying and neutralising each individual mine remains resource-intensive, and when the number of mines goes up, that process does not scale well.

Why this matters beyond the military

The Strait of Hormuz situation is the sharpest example. Analysts have compared the disruption to the energy crises of the 1970s. Even after a political agreement, shipping recovery could stretch to late 2026 or beyond, partly because mine clearance is physically slow and partly because the confidence needed for commercial traffic to resume takes time to establish.

The Red Sea is another case. Since late 2023, Houthi attacks on commercial shipping using missiles, drones, and mines have cut traffic through the Bab al-Mandeb by roughly 60%. Egypt estimated the disruption cost its Suez Canal around $7 billion in revenue in 2024 alone.

The Baltic Sea carries both a historical and a modern threat. More than 80,000 mines and other unexploded remnants from the two World Wars are estimated to remain on the seabed, and at current clearance rates, that contamination will persist for generations. But legacy contamination is not the only concern. Russian shadow-fleet vessels have damaged at least twelve pipelines and cables across the Baltic since 2023. NATO has launched Operation Baltic Sentry in response, and Baltic-rim nations are investing heavily in seabed defence. The threat of new mine-laying in a future crisis is not historical. It is a live planning scenario for every Baltic navy.

What we think needs to change

We are not arguing that existing mine countermeasures have it wrong. The shift toward unmanned, autonomous, distributed systems is the right direction, and it is already happening. What we think can be pushed further is the neutralisation step itself, specifically how many mines you can address simultaneously.

At Nordhal Defence, we are building low-cost, expendable, fibre-optic tethered underwater drones designed for parallel deployment. If you know where five mines are, you deploy five drones at once. A single operator controls multiple units through semi-autonomous mission execution. The neutralisation step happens in parallel, not in sequence.

The cost comes down by offloading most of the sensors and compute to the surface vessel (the underwater vehicle stays simple and cheap) and by leaning heavily on modern manufacturing methods rather than traditional defence-grade components. The system is designed to integrate with existing platforms: frigates, patrol vessels, or autonomous surface vessels. The operator stays on the vessel. No crew needs to be exposed anywhere near the minefield.

We are a Danish startup with a prototype in development, and we have a lot still to prove. Finding and classifying mines is a separate enormous challenge, and we are not trying to solve it. We are focused on the step that comes after: when you know where the mines are and you need to deal with them quickly, in numbers, from whatever platform is available.

The question is whether you can compress the time asymmetry by attacking the neutralisation bottleneck directly. We think you can. If you work in this space, I would genuinely like to hear how you see it on our LinkedIn post.

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