We went from swords to machine guns and nuclear bombs, but what are the next weapons on the horizon? We round up ten of the most promising technologies.

These are robotic vehicles, under development, that search and destroy enemy troops and equipment on the ground or in the air, without risk to friendly troops – theoretically.

How they work:  Onboard computers interpret sensor data to identify and target hostile forces with built-in weapons. Robots may query human controllers at remote sites for the go-ahead to fire, and friendly forces may carry transponders that identify them as “friends”.

Limitations: Difficulty of quickly and reliably discriminating between hostile forces and neutral or friendly parties or objects, such as civilians, cows, trees, and tractors. Systems that check with human controllers are vulnerable to communication failures. Malfunctioning robots could fire wildly at anything.


2. High-energy lasers

These are powerful energy beams that travel through air or space in straight lines. They travel at the speed of light and can strike over distances of thousands of kilometres.

How they work: Large mirrors focus powerful laser beams onto a small spot on the target. The heat produced burns through the surface of the target, disrupting flight, disabling warheads, or igniting fuels or explosives.

Limitations: It needs much more energy to do damage than bullets, which destroy targets with their momentum. Powerful lasers need fuel or electrical power and are also very bulky (the US Airborne Laser fills a Boeing 747). Travelling through air and turbulence can disperse the energy of the beam.

3. Space-based weapons

Space is the ultimate high ground, so weapons in orbit would have the ability to see and zap anything on the ground, in the air, or nearby in space.

How they work: The main mission of space-based weapons would be to defend against ballistic missiles fired at targets on Earth. Fleets of interceptors or battle stations would be stationed in orbit, poised to fire at any attacking missiles. The leading approach now is solid projectiles – such as tungsten rods- that would impact missiles. But laser battle stations are also under consideration.

Limitations: The technology is immature. Reaction times must be very fast. Interceptors must hit warheads to destroy them, which is difficult. Lasers also need chemical fuel or electrical power which is not readily available in space.

Launched from a standard runway, a hypersonic aircraft could fly faster than Mach 5 to strike anywhere in the world within two hours. It would also have enough thrust to deliver a satellite to low-Earth orbit.

How they work: To get off the ground from a runway, a hypersonic plane would either hitch a ride on a conventional plane, or have its own conventional jet engine. That engine would carry the hypersonic craft to an altitude where air density and resistance are less. Here it would reach supersonic speeds and then shift to its scramjet engine. The scramjet scoops up air and mixes it with fuel so it burns as the mixture flows through the engine at supersonic speeds. This means scramjets can achieve some of the speed of a rocket without having to carry heavy oxidiser (to mix with fuel), as rockets do.

Limitations: The technology is immature, with many engineering issues unresolved. Scramjets engines can not start until the plane flies faster than the speed of sound. Plus, hypersonic flight has so far only been demonstrated for small unpiloted craft carried to high speed by other vehicles – and other planned experimental craft are too small to carry a pilot.

5. Active Denial System

Millimetre-wave or microwave beams supposedly make people flee without injuring them. They might typically be powered by a generator fitted to a Humvee, in crowd control situations.

How it works: A 2-metre antenna and mobile generator produce and aim a beam of 95-gigahertz (3-millimetre) radiation. The top 0.3 mm of skin absorbs millimetre waves, causing intense pain within five seconds, so people flee quickly, if they can.

Limitations: Serious injury is possible if people cannot escape from the beam; skin burns within minutes. The beam also superheats metal objects like coins, earrings, or spectacle frames, which can then burn skin.

Nuclear missiles are able to deliver unmatched destructive power anywhere in the world, making them the ultimate level of military power.

How they work: One or more nuclear warheads are mounted on a ballistic missile, and launched vertically. The rocket burns out in the upper atmosphere, then coasts to its programmed destination where the bomb descends and explodes.

Limitations: These weapons are so frighteningly destructive that they have never been used in war (the Hiroshima and Nagasaki bombs – which had much less destructive power – were dropped from aircraft). Plus, the launch site and trajectory are easy to identify, inviting retaliation in kind from the target nation.

7. Stun guns (Tasers)

Tasers disable people with bursts of high-voltage electricity, allowing police to subdue them without lasting injury.

How it works: A special gun fires darts on wires. These deliver a pulse of electricity that temporarily disrupts control of voluntary muscles. Police target body or legs to avoid vulnerable areas such as head and neck. Without muscle control, people fall to the ground.

Limitations: Tasered people may be injured when they fall to ground. Darts can injure the throat, eyes, or genitals. Pulses can cause muscle spasms or seizures, and deaths have been reported. One pulse does not stop all people, and there have been allegations of misuse of stunguns, and claims of their use in torture.

High-power microwave pulses can knock out computers, electronics, and electrical power, crippling military and civilian systems.

How they work: A rapid increase in electromagnetic field strength during a pulse, induces surges of electric current in conductors. This burns out electrical equipment – semiconductor chips are particularly vulnerable. Special bombs generate the most intense pulses covering large areas, but unmanned aircraft carrying smaller generators can pinpoint targets.

Limitations: The effects can depend on local conditions, and are hard to predict. Sensitive enemy military equipment can be shielded, and microwaves also disable friendly electronics within range.

9. Layered missile defence

Layered missile defence offers the best chance to shoot down attacking ballistic missiles.

How it works: Multiple anti-missile systems are deployed to target ballistic missiles during different stages of the attacking missile’s flight: (1) The boost phase, while the rockets firing engines makes it easy to spot; (2) Mid-course, while the warhead coasts in space, and; (3) The terminal phase, as it approaches the target. Each phase, or layer, of defence increases the chance of successful destruction of the missile.

Limitations: Depends on efficiency of each layer. The system is very expensive to build, test, deploy, and maintain. The initial boost phase is easiest to target, but requires extremely fast reaction times.

This technique interferes with the flow of information vital to enemy operations, while defending friendly channels of communication.

How it works: Information warfare specifically targets communication networks and computers. Expert computer hackers, called crackers, might break into or overload military computers and networks, or spread computer viruses. Jammers might also block radio and television transmissions. Misinformation is circulated deliberately.

Limitations: The US relies more on computers and communications than most of their potential adversaries – making the technique a potential threat to them, and of limted use against low-tech opponents. Both side are also vulnerable to mis-information.