Technology

Know the difference – rockets versus missiles

Find out what makes a missile a missile, and a rocket and rocket.

The terms 'rocket' and 'missile' are often used interchangeably, which is understandable for anyone without a working knowledge of the subject as they are both varieties of weapons systems that deliver explosive warheads to their targets by rocket propulsion.

Even some in military fields – without naming names – have occasionally struggled to give a confident answer to the question of the difference between a rocket and a missile.

Meanwhile, members of the Armed Forces have been quick to call out some media organisations on social media when it is reported that "rockets have been fired" in news reports when, in fact, the weapons being referred to are missiles, or vice versa.

Coverage of the conflict in Ukraine, for example, has been known to mistakenly refer to one or the other of rockets or missiles with apparent confusion over which is which.

To the undiscerning eye, the two can look remarkably similar – both are launched at distant targets, both propel themselves through the air, and both deliver explosive charges.

What follows is a look at these similar, but distinct, weapon systems, with a basic explanation of the differences for those who remain unsure.

Rockets

Although they look like missiles, rockets are technologically simpler and were therefore developed far earlier than missiles.

The first rockets date back to the 13th Century and were used in medieval China.

The Chinese also developed early forms of multiple-launch rocket systems, which were rudimentary wooden launchers containing multiple arrows propelled by and carrying explosive batches of gunpowder.

Early rocket technology spread via the Mongols to Europe, where they were used in sieges as a kind of incendiary projectile.

Europeans themselves, and specifically soldiers of Britain's East India Company (EIC), or Honourable East India Company (HEIC), encountered rockets during the Battle of Pollilur in 1780.

Encountered, in this instance, meant being on the receiving end of them, and as A Bowdoin van Riper points out in 'Rockets and Missiles: The Life Story of a Technology', these rockets were a step-up from earlier types.

Rather than being made of bamboo or pasteboard, as rockets had been for centuries, they instead consisted of iron tubes packed with flammable and explosive materials. Although weightier than earlier variants, they also packed in more propellant and had greater thrust and range, apparently able to travel 1.5 miles.

According to van Riper, one factor in the defeat of the British was that the Mysorean rockets caused their ammunition wagon to catch fire, and a painting depicting the battle suggests they exploded with immense force.

Jump forward in time about 150 years and the pattern for modern rockets was being established. This essentially consisted of substituting the long metallic rocket tubes filled with propellant and payloads for long metallic launchers filled with smaller rockets.

missiles versus rockets
American paratroopers firing AT4 anti-tank rockets (Picture: US Department of Defense).

This is the main concept behind the first anti-tank rocket launchers of World War 2 such as the American Bazooka, the British PIAT and the German Panzerfaust and Panzerschreck.

An even more recent equivalent is the AT4, which works in a similar fashion. Essentially, rockets, be they NASA space rockets or anti-tank rockets, work by using momentum – that is, the momentum of the thrust they generate being used to propel them through the air.

That thrust comes from propellant, which is a reactive fuel like gunpowder in early rockets, or nitroglycerine, that is ignited by pulling the trigger on a launcher.

Once it leaves the launcher, the shape of a rocket is designed to cut down on air resistance and thereby make it travel on a trajectory that is as smooth and predictable as possible, an important feature given that rockets must be aimed at their intended targets.

An explosive charge in the top of the rocket then goes off, either when it has struck its target, or when an internal fuse detonates it after a certain period of time, such as five seconds.

The thrust from rockets can cause a certain amount danger since the propellant creates a back blast that can burn the firer or adjacent personnel. They must therefore not only be aimed carefully at their intended targets but also positioned correctly to avoid injuring those who are near the rocket when it is launched.

missiles versus rockets
French paratroopers using an AT4 anti-tank rocket launcher on Salisbury Plain in 2020 (Picture: MOD).

Missiles

Although they look very similar to rockets, missiles are a step up technologically.

While they also have propellant and use thrust to reach their targets, and have explosive warheads just like rockets, there is a crucial difference: rockets rely on accurate aiming, but every individual missile has its own guidance system.

More complex flight paths over longer distances also mean that missiles tend to have more in the way of aerodynamic external elements, such as larger tail fins and wings.

In terms of predecessors, there was an early form of rocket in medieval China known as the Huolongchushui, which roughly translates as 'fire dragon out of water'. This weapon has been likened to a kind of ancestor of modern ballistic missiles.

It was initially propelled towards its target by downward-facing rockets packed with gunpowder, and then, apparently, by arrow rockets contained within its bamboo body.

The fuses on these would be automatically lit when those on the external rockets burnt out.

However, since the Huolongchushui did not have a guidance system, it was more akin to an early two-stage rocket than a modern missile.

The earliest true missiles were the V-1 flying bomb and the misnamed V-2 rocket, both of which were developed by Nazi Germany and fired at London and other targets.

The guidance system of the V-1 consisted of two gyroscopes designed to keep it on a level flight path and counteract air resistance or wind, which might have caused side-to-side or tilting motions liable to send the missile off its intended path.

V-1s also contained internal compasses and barometric devices to help them maintain direction and altitude.

V-2 rockets had guidance systems that worked similarly, although they also had accelerometers that controlled their speed, and both missiles had technologies that cut off their engines at pre-programmed moments, causing them to, effectively, dive on their target areas.

Modern missiles can be far smaller than their Second World War-era predecessors, and systems such as the NLAW and Javelin are good examples.

missiles versus rockets
An NLAW missile seen in flight after being fired (Picture: MOD).

Like the AT4, both are anti-tank weapons, although a telltale difference is the nature of the projectile's flight path.

The rocket fired out of the AT4 launcher travels in a continuous trajectory towards its intended target.

Missiles launched out of Javelin or NLAW systems, on the other hand, first head towards their targets, then shift direction by climbing up, before arcing downwards.

This is their internal guidance systems kicking in, since both weapon systems are designed to travel towards and hit what they are aimed at – usually a tank – but they do so by travelling up and over onto the top of the target.

The reason for this is that tank armour is weaker on top than it is on the front or sides of the vehicle, a feature that makes anti-tank missiles more deadly to tanks than more rudimentary rocket systems like the AT4.

As well as varying in size, missiles can also vary considerably in the type of guidance system they use. Some examples are heat-seeking systems, like the air-to-air missiles fighter jets use to shoot each other down, and laser-guided systems and satellite systems, like those used by some cruise missiles.

Inter-Continental Ballistic Missiles (ICBMs) use rocket technology, as in fuel as a propellant, to get airborne, as well as momentum to remain in flight. Guidance is provided mid-flight, perhaps by satellite, before gravity brings the missile down on its target.

Since ICBMs carry nuclear weapons, it is important to point out that none has ever been used in anger, although the potential threat of nuclear strike and counterstrike still lingers from the Cold War era.

In summary

Rockets have a long history, from the earliest medieval incendiary siege weapons to today's shoulder-fired anti-tank weapons. They differ from bombs because bombs do not propel themselves through the air, while rockets do.

Yet they also differ from missiles in that they do not have internal guidance systems of any kind to help direct them to their intended targets.

Missiles do have this feature, and, being more advanced, are a more recent technology, with the earliest types only going back to the Second World War.

Both weapon systems are commonly used as anti-tank weapons, and both are being used in Ukraine.

The AT4 is a good example of an anti-tank rocket system with a range of 300 to 500 metres.

It must be aimed but its rockets use internally generated thrust to drive themselves towards targets.

Javelins and NLAWs are good examples of comparable missile systems that also perform an anti-tank function but do so with missiles that lock onto a target the firer has aimed at, then guide themselves up, over and down onto it, causing maximum damage.

missiles versus rockets
A Javelin anti-tank missile in flight (Picture: MOD).

Cover image: Javelin anti-tank missile in flight (Picture: MOD).