Branchoria Directed Energy Directed Energy

Clear explanations of laser and microwave weapons without science-fiction hype.

Within Weather Limits

Low-flying drones are a particular challenge for laser air-defence systems because a laser cannot engage a target that it cannot directly see. Unlike a missile, which can be launched toward a target using external guidance and continue travelling beyond the horizon, a laser beam must maintain an uninterrupted optical path from the weapon to the target.

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Introduction

Within the broader problem of weather and atmospheric effects on laser weapons, the horizon issue is different. Fog and rain weaken a beam that reaches the target. The horizon problem prevents the beam from reaching the target at all.

Low Flying illustration 1

Why Direct Optical Sight Is Non-Negotiable

A high-energy laser weapon works by concentrating energy onto a precise point on a target for a sustained period. To do that, the system must continuously track the target and keep the beam accurately focused. Any obstacle between the laser and the target breaks the engagement immediately. [Wikipedia+2GAO]WikipediaLaser weaponMay 10, 2026 — A laser weapon is a type of directed-energy weapon (DEW) that uses lasers to inflict damage. Laser weapons are of two type…Published: May 10, 2026

This requirement creates a fundamental limitation that does not disappear with more power. A stronger laser can burn faster once it reaches a target, but it cannot pass through a hill, around a building, or over the Earth’s curvature. Military analysts therefore distinguish between weapon power and engagement geometry. A laser may have enough energy to defeat a drone, yet still be unable to fire because the target remains below the visible horizon. [The Strategist+2Arms Control Association]aspistrategist.org.auwar at the speed of light the emerging role of directed energy weaponsThe Strategistthe emerging role of directed-energy weapons15 Apr 2026 — Certainly, directed-energy weapons may be key to inexpensively co…

The same basic constraint affects many sensors and weapons. Radar engineers refer to a radar horizon, where Earth’s curvature hides low-altitude objects from line-of-sight systems. Laser weapons face an even stricter version because both detection and energy delivery require a clear optical path. [radartutorial.eu+2PubMed Central]radartutorial.euRadar Line of SightThe earth's curvature may prevent the radar seeing a target within the maximum range given by the radar range equation…

C: MO - Understanding Radar Horizon

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How Low Altitude Changes Engagement Geometry

The reason low-flying drones can hide so effectively is simple geometry. The closer an object is to the ground, the sooner Earth’s curvature blocks it from view. A drone flying hundreds or thousands of metres above the surface can often be seen at much greater distances than one skimming just above terrain or sea level. [radartutorial.eu+2omnicalculator.com]radartutorial.euRadar Line of SightThe earth's curvature may prevent the radar seeing a target within the maximum range given by the radar range equation…

For a laser defence unit positioned on the ground or aboard a ship, this means engagement range is not determined solely by laser power. It is also determined by how far away the system can physically see the target.

Consider two drones approaching the same laser-equipped ship:

  • A higher-altitude drone may become visible far from the vessel, giving the laser time to track, dwell on, and engage it.
  • A sea-skimming drone may remain hidden below the horizon until much later, dramatically reducing the available engagement window.
  • If terrain or structures obstruct the view, the laser may not acquire the target until it is already close to the defended asset. [Space & Defense+2Wikipedia]spaceanddefense.ioSpace & DefenseThe war laser: New terrestrial surface battlefield geometrySep 29, 2020 — Target (T2) is partially hidden by the curvature…

This geometry is one reason low-altitude flight has long been used as a defensive tactic. Aircraft, cruise missiles, and increasingly drones can use terrain masking, hills, valleys, urban structures, or the curvature of the Earth to stay beneath line-of-sight systems for as long as possible. [Wikipedia+2Business Insider]WikipediaRadar horizonRadar horizon

Low Flying illustration 2

Terrain Can Be More Important Than Weather

In some situations, terrain matters more than atmospheric conditions.

A laser on a clear day may have excellent beam quality, but if a drone remains behind a ridgeline or flies through a valley, there is still no engagement opportunity. Conversely, a target in full view may be reachable despite moderate atmospheric degradation. This distinction is important because discussions of laser performance often focus on fog, rain, and dust while overlooking the simpler fact that lasers cannot engage what they cannot see. [nps.edu+2ResearchGate]nps.eduPropagation of High Energy Lasers for Various …This would help guide the Navy in developing designs and tactics for laser weapons in vaThe goal is real-time atmospheric characterization …Read more

At sea, the problem appears in a different form. The ocean surface may seem unobstructed, but the curvature of the Earth creates its own masking effect. Small drones flying just above wave height can remain below the line of sight of shipboard sensors and laser systems until relatively late in their approach. [radartutorial.eu+2rfcafe.com]radartutorial.euRadar Line of SightThe earth's curvature may prevent the radar seeing a target within the maximum range given by the radar range equation…

ALKA-KAPLAN Explained: The Hybrid Laser Tank Built to Hunt Drones

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Why Raised Sensors and Layered Defences Matter

Because the limitation is geometric, one of the most effective solutions is to place sensors higher.

Elevated sensors on towers, aircraft, balloons, or other airborne platforms can look beyond the horizon of ground-based systems. By detecting low-flying threats earlier, they increase the time available for tracking and engagement. Defence planners have long recognised that raising the sensor often extends the useful engagement area more effectively than simply increasing weapon power. [CSIS]csis.orgextending horizon elevated sensors targeting and missile defenseExtending the Horizon: Elevated Sensors for Targeting and…Sep 27, 2021 — Elevated sensors increase the engagement area by adding s…

For laser systems, this creates an important distinction between the sensor horizon and the weapon horizon. An airborne sensor may detect a drone early, but a ground-based laser still requires its own direct line of sight before it can fire. Detection alone does not solve the problem if the target remains physically hidden from the weapon. [CSIS]csis.orgextending horizon elevated sensors targeting and missile defenseExtending the Horizon: Elevated Sensors for Targeting and…Sep 27, 2021 — Elevated sensors increase the engagement area by adding s…

This is one reason modern air-defence architectures increasingly rely on layered systems rather than expecting lasers to replace missiles and guns. A missile can be launched using information from remote sensors and can travel beyond the shooter’s direct visual horizon. A laser cannot. As a result, lasers are often viewed as a valuable inner defensive layer that complements rather than replaces other interceptors. [The Strategist+2nps.edu]aspistrategist.org.auwar at the speed of light the emerging role of directed energy weaponsThe Strategistthe emerging role of directed-energy weapons15 Apr 2026 — Certainly, directed-energy weapons may be key to inexpensively co…

Low Flying illustration 3

The Practical Consequence for Counter-Drone Defence

The rise of small drones has made the laser-horizon problem more important. Many drones are compact, difficult to detect, and capable of flying at very low altitude. By staying close to terrain or the sea surface, they can shorten the period during which a laser system has both visibility and sufficient dwell time to achieve an effect. [Leonardo+2CSIS]leonardo.combody Land Naval Radars LQ mm08027LAND & NAVAL RADARSDecember 14, 2016 — It detects and tracks any type of air and maritime threat, low level UAVs, to detect low f…Published: December 14, 2016

Recent laser demonstrations have shown that high-energy systems can successfully destroy drones once they are detected and tracked. Yet even successful programmes continue to emphasise line-of-sight limitations. The challenge is often not whether the laser can damage the drone, but whether the drone becomes visible early enough for the engagement to occur. [GOV.UK]GOV.UKBoost for Armed Forces as new laser weapon takes downNovember 20, 2025 — 20 Nov 2025 — Britain's ground-breaking DragonFire laser has shot down high-speed drones in new trials, as a £316 mil…Published: November 20, 2025

In practice, the laser horizon means that low-flying drones can exploit the oldest form of concealment in warfare: hiding behind the shape of the Earth itself. For directed-energy weapons, overcoming that limitation is often a matter of geometry, sensor placement, and defensive layering rather than raw laser power. [Space & Defense+2CSIS]spaceanddefense.ioSpace & DefenseThe war laser: New terrestrial surface battlefield geometrySep 29, 2020 — Target (T2) is partially hidden by the curvature…

Why Laser Weapons Cannot Replace Missiles In Modern Warfare | WION Podcast

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Further Reading

Books and field guides related to Low Flying. Use these as the next step if you want deeper reading beyond the article.

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The Kill Chain

By Christian Brose

Explains modern sensor networks, engagement geometry, and layered defenses that help address line-of-sight limitations.

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Endnotes

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    Title: SEA 19B DEW Final Report
    Link: https://nps.edu/documents/105988579/106076800/SEA-19B_DEW_Final_Report.pdf
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    VIABLE SHORT-TERM DIRECTED ENERGY WEAPON...Jun 19, 2013 — In addition, conventional weapons currently have a greater range than directed...

  2. Source: Wikipedia
    Title: Laser weapon
    Link: https://en.wikipedia.org/wiki/Laser_weapon
    Source snippet

    May 10, 2026 — A laser weapon is a type of directed-energy weapon (DEW) that uses lasers to inflict damage. Laser weapons are of two type...

    Published: May 10, 2026

  3. Source: gao.gov
    Title: gao 23 105868
    Link: https://www.gao.gov/products/gao-23-105868
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    Directed Energy Weapons: DOD Should Focus on...17 Apr 2023 — DOD spends about $1 billion annually on directed energy—concentrated electr...

  4. Source: gao.gov
    Title: These weapons include high energy lasers and other
    Link: https://www.gao.gov/products/gao-23-106717
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    Science & Tech Spotlight: Directed Energy WeaponsMay 25, 2023 — Directed energy weapons (DEW) use concentrated electromagnetic energy...

    Published: May 25, 2023

  5. Source: radartutorial.eu
    Link: https://www.radartutorial.eu/07.waves/wa16.en.html
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    Radar Line of SightThe earth's curvature may prevent the radar seeing a target within the maximum range given by the radar range equation...

  6. Source: Wikipedia
    Title: Radar horizon
    Link: https://en.wikipedia.org/wiki/Radar_horizon

  7. Source: omnicalculator.com
    Link: https://www.omnicalculator.com/physics/radar-horizon

  8. Source: rfcafe.com
    Link: https://www.rfcafe.com/references/electrical/ew-radar-handbook/radar-horizon-line-of-sight.htm
    Source snippet

    Radar Horizon / Line of SightIn obtaining the radar horizon equations, it is common practice to assume a value for the Earth's radius tha...

  9. Source: csis.org
    Title: extending horizon elevated sensors targeting and missile defense
    Link: https://www.csis.org/analysis/extending-horizon-elevated-sensors-targeting-and-missile-defense
    Source snippet

    Extending the Horizon: Elevated Sensors for Targeting and...Sep 27, 2021 — Elevated sensors increase the engagement area by adding s...

  10. Source: nps.edu
    Link: https://nps.edu/web/research/-/propagation-of-high-energy-lasers-for-various-[wavelengths
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    The goal is real-time atmospheric characterization...Read more...

  11. Source: researchgate.net
    Link: https://www.researchgate.net/publication/307435846_Atmospheric_Propagation_of_High-Energy_Laser_Beams
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    (PDF) Atmospheric Propagation of High-Energy Laser BeamsLaser sources are widely used for exploring the atmosphere, in particular, its ga...

  12. Source: leonardo.com
    Title: body Land Naval Radars LQ mm08027
    Link: https://www.leonardo.com/documents/16277707/18388480/body_Land_Naval_Radars_LQ_mm08027_.pdf?t=1542836436655
    Source snippet

    LAND & NAVAL RADARSDecember 14, 2016 — It detects and tracks any type of air and maritime threat, low level UAVs, to detect low f...

    Published: December 14, 2016

  13. Source: GOV.UK
    Title: Boost for Armed Forces as new laser weapon takes down
    Link: https://www.gov.uk/government/news/boost-for-armed-forces-as-new-laser-weapon-takes-down-high-speed-drones
    Source snippet

    November 20, 2025 — 20 Nov 2025 — Britain's ground-breaking DragonFire laser has shot down high-speed drones in new trials, as a £316 mil...

    Published: November 20, 2025

  14. Source: Wikipedia
    Title: Over the horizon radar
    Link: https://en.wikipedia.org/wiki/Over-the-horizon_radar
    Source snippet

    Over-the-horizon radarOver-the-horizon radar (OTH), sometimes called beyond the horizon radar (BTH), is a type of radar system with th...

  15. Source: gao.gov
    Title: gao 26 107648
    Link: https://www.gao.gov/products/gao-26-107648
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    FAA Planning Efforts Should Address How Drones Will...Feb 4, 2026 — In August 2025, FAA proposed new regulations that would require dron...

    Published: August 2025

  16. Source: researchgate.net
    Link: https://www.researchgate.net/publication/403676537Laser-Based_Directed_Energy_Weapons_Technological_Capabilities_Material_Interaction_and_Strategic[Deployment
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    (PDF) Laser-Based Directed Energy WeaponsThermal Blooming: Localized air heating changes the refractive index, causing beam defocus and r...

  17. Source: aspistrategist.org.au
    Title: war at the speed of light the emerging role of directed energy weapons
    Link: https://www.aspistrategist.org.au/war-at-the-speed-of-light-the-emerging-role-of-directed-energy-weapons/
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    The Strategistthe emerging role of directed-energy weapons15 Apr 2026 — Certainly, directed-energy weapons may be key to inexpensively co...

  18. Source: spaceanddefense.io
    Link: https://spaceanddefense.io/the-war-laser-new-terrestrial-surface-battlefield-geometry/
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    Space & DefenseThe war laser: New terrestrial surface battlefield geometrySep 29, 2020 — Target (T2) is partially hidden by the curvature...

  19. Source: armscontrol.org
    Title: reasons doubt laser missile defense
    Link: https://www.armscontrol.org/blog/2018-05-14/reasons-doubt-laser-missile-defense
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    This is because lasers, unlike kinetic interceptors, face limitations.Read more...

  20. Source: pmc.ncbi.nlm.nih.gov
    Title: Pub Med Central An Overview of Sensors for Long Range Missile Defense
    Link: https://pmc.ncbi.nlm.nih.gov/articles/PMC9781809/
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    defense radars is that they can only detect objects in the line of sight. The curvature of the Earth [limits]({{ 'limits/' | relative_url }}) the maximum distance that can...

  21. Source: businessinsider.com
    Link: https://www.businessinsider.com/new-radar-tech-flattened-earth-making-low-jets-targets-raf-2025-10
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    Speaking at the Royal United Services Institute, Beck warned that tactics like terrain-masking and ultra-low flying—once effective agains...

  22. Source: war.gov
    Title: site selections announced for directed energy counter drone program
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    Source snippet

    Site Selections Announced for Directed-Energy Counter-...6 May 2026 — On behalf of the War Department, Joint Interagency Task Force 401...

    Published: May 2026

Additional References

  1. Source: linkedin.com
    Link: https://www.linkedin.com/posts/lone-star-drone_drone-deliveries-expected-to-increase-substantially-activity-7439353298048004096–oQF
    Source snippet

    GAO Highlights Drone Safety Challenges in Beyond Visual...GAO Highlights Drone Safety Challenges in Beyond Visual Line of Sight Operatio...

  2. Source: flatearth.ws
    Link: https://flatearth.ws/c/military
    Source snippet

    MilitaryA laser-guided missile can be launched toward a target behind Earth's curvature. Flat-Earthers claim it proves a flat Earth as it...

  3. Source: tscm.com
    Link: https://www.tscm.com/rdr-hori.pdf
    Source snippet

    RADAR HORIZON / LINE OF SIGHTThere are limits to the reach of radar signals. At the frequencies normally used for radar, radio waves usua...

  4. Source: instagram.com
    Link: https://www.instagram.com/reel/DRUtM8hDKZS/?hl=en
    Source snippet

    UK Government Scotland on Instagram: "Introducing...classified, but it is a line-of-sight weapon. A new naval weapon is shooting down dr...

  5. Source: unmannedairspace.info
    Link: https://www.unmannedairspace.info/counter-uas-systems-and-policies/us-gao-report-directed-energy-weapon-technical-maturity-levels-still-lagging/
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    US GAO report: directed energy weapon technical maturity...The US Department of Defense (DOD) is currently developing directed energy we...

  6. Source: cdn.asp.events
    Link: https://cdn.asp.events/CLIENT_Clarion__96F66098_5056_B733_492B7F3A0E159DC7/sites/EWEurope-2020/media/libraries/day-2-plenary/DAY-2—14-25—K1–David-Stoudt-TO-SHARE.pdf
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    Federal Aviation Administration (FAA) Guidelines: • <55 lbs; including everything onboard/attached to the aircraft. • Operated <100 miles...

  7. Source: coherentmarketinsights.com
    Title: directed energy weapons in counter drone missile defense 3576
    Link: https://www.coherentmarketinsights.com/blog/aerospace-and-defense/directed-energy-weapons-in-counter-drone-missile-defense-3576
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    Directed Energy Weapons in CounterDrone Missile Defense4 May 2026 — Lasers are capable of tracking targets and engaging them within less...

    Published: May 2026

  8. Source: reddit.com
    Link: https://www.reddit.com/r/FacebookScience/comments/1oecscz/facebook_man_is_back_and_giving_his_expertise_on/
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    , the one where the lasers didn't line up over the "curve".Read more...

  9. Source: reddit.com
    Link: https://www.reddit.com/r/Military/comments/1lwdkds/if_a_railgun_can_hit_a_target_100_miles_away_how/
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    eyd use a targeting computer, to automatically determine trajectory...

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    Link: https://www.reddit.com/r/WarCollege/comments/1es0eef/why_are_detection_ranges_for_naval_targets_so/
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    troyer- or frigate- size vessel is always shorter than that for an...

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Weather Limits When the Air Gets in the Beam

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