Countering Tethered Drones: Are Optically Tethered Drones a Game Changer for Multi-Rotor Defeatability?

Multi-rotors have emerged as a significant force on the battlefield, offering key advantages over traditional guided munitions. Their primary benefits include:

1. Cost-effectiveness – Multi-rotors are far cheaper than guided munitions, making them expendable and easy to deploy in large numbers.

2. Loitering Capability – Unlike traditional munitions, multi-rotors can persist in the battlespace, waiting for the optimal moment to strike.

3. Manoeuvrability – Multi-rotors can navigate tight spaces and turn at low speeds, making them highly adaptable in complex environments.

   
   

The Primary Countermeasure: RF Jamming

To date, the most effective battlefield countermeasure against multi-rotors has been radio frequency (RF) jamming. By disrupting communication and control links, defenders can neutralize multi-rotor threats before they strike. However, recent developments have introduced a new challenge: optically tethered multi-rotors.

The Rise of Optically Tethered Multi-Rotors

In the past few months (last quarter of 2024), multi-rotors equipped with fibre optic tethers for communication and control have appeared and are proving effective. Unlike RF-controlled multi-rotors, these systems are immune to jamming, as they rely on a physical link rather than vulnerable electromagnetic signals.

So, does this make optically tethered multi-rotors a game changer? The answer is more yes than no.

Why Countering Tethered Drones is a Challenge

1. Immunity to Jamming – This is the single biggest shift in the threat landscape. Traditional RF jamming systems, which have formed the backbone of counter-multi-rotor strategies, are ineffective against fibre optic tethers.

2. Low Cost – While it might seem that fibre optics would add significant cost, the reality is quite different. A kilometre of optical fibre costs as little as £10, with terminations costing pennies and optical transceivers available for a few pounds. This means an optically tethered multi-rotor is likely only 10% more expensive than an RF-controlled equivalent, keeping the cost advantage of multi-rotors largely intact.

3. Not a New Concept – Tethered munitions are not a new idea; for instance, TOW guided missiles have used wire guidance for decades. Applying a similar principle to multi-rotors is a logical step in multi-rotor warfare evolution.

   
   

The Trade-Offs of Optical Tethers

While fibre optic tethers solve the vulnerability to jamming, they introduce other constraints:

1. Increased Mass and Drag – The optical fiber must be stored on a spool, which is large and heavy. This could double the drag of the multi-rotor and increase its mass by around 30%, reducing range, endurance, and speed.

2. Potential Impact on Manoeuvrability – While the tether typically lays on the ground rather than dragging, the multi-rotor must avoid tangling. So far, battlefield footage does not show multi-rotors performing highly complex manoeuvres, but as physical interdiction (e.g., nets, kinetic countermeasures) becomes a more common defensive response, evasive manoeuvring may become more critical.

   
   

Countering Tethered Drones: Directed Energy Weapons

With jamming rendered ineffective, directed energy weapons (DEWs) remain a potential countermeasure. However, DEWs come with significant limitations:

• Cost – These weapons are currently experimental and cost millions per unit.

• Limited Engagement Rate – DEWs can only target one multi-rotor at a time, making them vulnerable to swarm tactics.

• Exposure Time – A DEW must heat up the multi-rotor’s components for several seconds to disable it, during which the multi-rotor may still complete its attack.

• Line-of-Sight Dependency – DEWs require an unobstructed view of the multi-rotor, making them more effective in open environments (e.g., at sea) than on land, where terrain and obstacles can block the beam.

  
  

Conclusion: A Significant Development, but Not a Silver Bullet

The development of optically tethered multi-rotors is a significant shift in multi-rotor warfare, eliminating the primary vulnerability of multi-rotors without substantially compromising their best attributes. This technology is simple for state-level actors to implement and, while commercially available fibre optic tethers are expensive, they are still within reach for non-state actors and domestic threats.

While countering tethered drones is a tougher challenge for defenders, their increased mass, drag, and operational constraints mean they are not an invulnerable threat. Counter-multi-rotor strategies will need to evolve beyond RF jamming, incorporating kinetic interception, electronic warfare adaptations, and scalable direct energy solutions.

Ultimately, optically tethered multi-rotors are more of an evolution than a revolution—one that defenders must now contend with.