earthquake bombs (also invented by Barnes Wallis) named "Grand Slam", which, unusually for the time, were delivered from high altitude in order to gain high speed, and would, upon impact, penetrate and explode deep underground ("camouflet"), causing massive caverns or craters, and affecting targets too large or difficult to be affected by other types of bomb. Modern military bomber aircraft are designed around a large-capacity internal bomb bay, while fighter-bombers usually carry bombs externally on pylons or bomb racks or on multiple ejection racks, which enable mounting several bombs on a single pylon. Some bombs are equipped with a parachute, such as the World War II "parafrag" (an fragmentation bomb), the Vietnam War-era daisy cutters, and the bomblets of some modern cluster bombs. Parachutes slow the bomb's descent, giving the dropping aircraft time to get to a safe distance from the explosion. This is especially important with air-burst nuclear weapons (especially those dropped from slower aircraft or with very high yields), and in situations where the aircraft releases a bomb at low altitude. A number of modern bombs are also precision-guided munitions, and may be guided after they leave an aircraft by remote control, or by autonomous guidance. Aircraft may also deliver bombs in the form of warheads on guided missiles, such as long-range cruise missiles, which can also be launched from warships. A hand grenade is delivered by being thrown. Grenades can also be projected by other means, such as being launched from the muzzle of a rifle (as in the rifle grenade), using a grenade launcher (such as the M203), or by attaching a rocket to the explosive grenade (as in a rocket-propelled grenade (RPG)). A bomb may also be positioned in advance and concealed. A bomb destroying a rail track just before a train arrives will usually cause the train to derail. In addition to the damage to vehicles and people, a bomb exploding in a transport network often damages, and is sometimes mainly intended to damage, the network itself. This applies to railways, bridges, runways, and ports, and, to a lesser extent (depending on circumstances), to roads. In the case of suicide bombing, the bomb is often carried by the attacker on their body, or in a vehicle driven to the target. The Blue Peacock nuclear mines, which were also termed "bombs", were planned to be positioned during wartime and be constructed such that, if disturbed,