I heard, some time back, on the BBC News that a Malaysian plane was hit not by a 'rocket' but by a 'missile'. From the dictionary definitions I had looked up, I could gauge the difference! As far as I know, "Missile' is an object which is forcibly propelled at a target, either by hand or from a mechanical weapon. And 'Rocket' is a cylindrical projectile that can be propelled to a great height or distance by the combustion of its contents.
Is it therefore the case that a Rocket is always a Missile, but that a Missile is not necessarily a Rocket? A cricket ball can be regarded as a "Missile" but is clearly not a Rocket. But why could the type of weapon which, it is believed, brought down Flight MH17 not be described as a 'Rocket'? A ‘Missile’ is generally understood to be a weapon, but a ‘Rocket’ need not be. Consider the various ‘Rockets’ used to launch satellites and astronauts into space.
A cricket ball as bowled is a ‘Missile’, in that the bowler's intent is to damage the current arrangement of the wicket. As hit by the batsman, not so much. A baseball as pitched is not a ‘Missile’ unless it is pitched as an intentional bean-ball, among the foulest of fouls in that game.
Of course, language does not stand still, and definitions have a way of evolving and intertwining, such that the distinctions now may be rather different from what they were originally, and so the Air Force launches ‘Missiles’, while NASA launches ‘Rockets’. Perhaps the difference has evolved to the first exploding on purpose, while the second only exploding by accident.
I would like to add another dimension to this discussion. With the advent of ‘Precision Guided ‘Rockets’, there is hardly any difference between ‘Rockets’ and ‘Missiles’, maybe with the exception of range, as most missiles tend to have a longer range than rockets. Today manufacturers use the term ‘Rocket’ as a marketing term for something that is less expensive than ‘Missiles’.
There are several key differences between a ‘Rocket’ and a ‘Missile’ - rolewise as well as operation wise. ‘Rockets’ come in two main categories. Guided and unguided. Guided ‘Rockets’ can be semi-active homing types, that is, they can do minor course corrections mid flight to reach a specific target once the target is designated. Unguided ‘Rockets’ follow line of sight and hence the pilot will have to aim specifically at the target while firing the rocket.
A ‘Rocket’ is so called on the basis of its mode of self-propulsion. A ‘Missile’ is so called on the basis of its being propelled, by a ‘Rocket’ engine or otherwise, for the purpose of doing damage, as a weapon. The two categories overlap considerably, since ‘Rockets’ are commonly used as propulsion for missiles, with or without in-flight guidance systems. Put an explosive warhead on top of an Atlas ‘Rocket’, and launch it at an enemy (or practice target), the whole assembly becomes a missile. Put a Mercury capsule on top with John Glenn inside, it is a rocket but not a missile. The weapon that reportedly brought down the Malaysian airliner was (or is, if considered generically) both a ‘Rocket’ and a ‘Missile’, and can properly be termed either one—though without the explosive payload that transforms it from mere ‘Rrocket’ to ‘Missile’ it would probably not have brought the plane down, so ‘Missile’, I believe is the more adequate term in this case.
‘Rockets’ are usually laden with less amount of explosive when compared to a missile which is heavier and packs more punch. ‘Rockets’ are rarely used for Air to Air combat since the target will have to visually be the same spot which is unlikely to happen in air to air combat. Hence ‘Rockets’ are generally used only for Air to ground combat. ‘Rockets’ come with a limited range as is obvious for reasons mentioned above. ‘Rockets’ can be launched simultaneously using a barrage of rocket launches effectively flattening a wide area with consecutive multiple hits.
‘Missiles’ come in a variety of shape and size and with different armament. ‘Missiles’ are usually guided by radar or infrared or laser designation and can be used for Air to Air, Air to Ground as well as Air to sea combat. Each role requires a different type of ‘Missile’ like the Aim9X or the AMRAAM ‘Missile’ or the R73 Missile. ‘Missiles’ are characterized by the wide range of operations. Some can go Beyond visual range of over 100 km and some used for dogfights with range as little as 5km.
A ‘Rocket’ is ‘Dumb’ and only hits what it is aimed at launch. A ‘Missile’ can have its flight path corrected even after launch