thumb|SS-24 rail-based ICBM launch After launch, a booster pushes the missile and then falls away. Most modern boosters are Solid-propellant rocket motors, which can be stored easily for long periods of time. Early missiles used liquid-fueled rocket motors. Many liquid-fueled ICBMs could not be kept fueled at all times as the cryogenic fuel liquid oxygen boiled off and caused ice formation, and therefore fueling the rocket was necessary before launch. This procedure was a source of significant operational delay and might allow the missiles to be destroyed by enemy counterparts before they could be used. To resolve this problem Nazi Germany invented the missile silo that protected the missile from Strategic Bombing and also hid fueling operations underground.
thumb|SS-24 rail-based ICBM launch After launch, a booster pushes the missile and then falls away. Most modern boosters are Solid-propellant rocket motors which can be stored easily for long periods of time. Early missiles used liquid-fueled rocket motors. Many liquid-fueled ICBMs could not be kept fueled at all times as the cryogenic fuel liquid oxygen boiled off and caused ice formation, and therefore fueling the rocket was necessary before launch. This procedure was a source of significant operational delay and might allow the missiles to be destroyed by enemy counterparts before they could be used. To resolve this problem Nazi Germany invented the missile silo that protected the missile from Strategic Bombing and also hid fueling operations underground.