Please introduce the advantages and disadvantages of liquid ballistic missiles and solid ballistic missiles.

From World War II to the end of 1950s, the United States and the Soviet Union developed the first generation of strategic ballistic missiles, such as Raytheon and Hercules in the United States and SS-5 and SS-6 in the Soviet Union. At that time, liquid propellant was used to launch from the ground, and temporary refueling was needed before launch, so the preparation time for launch was long and the survivability was low. In the late 1950s and 1960s, the second generation ballistic missiles developed by some countries still used liquid propellant, but some improvements were made, such as using storable propellant, to shorten the launch preparation time and improve the survivability.

Solid ballistic missiles are easy to use: the main reason is that solid missiles have lower cost, less equipment and faster response.

Solid ballistic missiles also have shortcomings, that is, their safety is not good, and they are prone to fire and explosion in the manufacturing process or the poor casting quality of solid propellant leads to explosion, resulting in the destruction of missiles and the death of personnel. For example, the American Polaris A-2 solid ballistic missile exploded on the launch pad many times due to grain defects; Pershing-2 ballistic missile also exploded once due to improper handling of thermal insulation; Another Trident I solid ballistic missile failed to launch due to the failure of the thermal insulation of the first stage engine.