Ballistic missiles are large and powerful missiles that are designed to attack a long-distance target carrying a warhead that may also be a nuclear warhead. These missiles use a suborbital trajectory and may sometimes reach higher than space altitudes (over 100 km), exiting the earth’s atmosphere before they drop on other continents. Sometimes they can even cover 1200 km into space for intercontinental targets. The missiles are shot with an initial mechanical boost. After this initial boost, the trajectory followed by the missile is a smooth parabola determined by ‘ballistics’.
Ballistic missile types
There are four different types of ballistic missiles.
• IRBM (intermediate-range ballistic missile) with a range between 3000 and 5500 km.
• ICBM (intercontinental ballistic missile) with a range exceeding 5500 km.
• MRBM (medium range ballistic missile) with a range between 1000 and 3000 km.
•SRBM (short range ballistic missile) with a range upto 1000 km.
Most ballistic missiles are designed for nuclear attacks. Ballistic missiles that have a range less than 350 kilometers never reach into the space. They are used for conventional explosions.
The fuel used in ballistic missiles
Both solid and liquid fuels are used in ballistic missiles. V2 rockets that were used by Germany and the ones that were first used by the United States are older version of ballistic missiles and used liquid fuel. The liquid propellant is mainly liquid hydrogen and the oxidizer used is liquid oxygen. Since they are to be used in liquid forms, they must be stored in cryogenic temperatures. If it is not done they will convert to their gaseous state. While launching, both the propellant and oxidizer are rapidly pumped out from the storage. A spark initiates the ignition of the mixed gases and the rocket is propelled forwards. Water vapor comes out as a byproduct.
IMPORTANCE OF LIQUID STATE
The liquid form of the fuel is desirable since they have more energy and density than when the fuel is in a gaseous form. Missiles using liquid fuels can be controlled better than those that ease gaseous fuels. The engines can achieve started and turned off quite easily. The problem with liquid fuel is that, it requires steady refrigerated conditions prior to their launch.
Hypergolic propellants are another form of liquid fuel. This fuel needs no external spark to initiate the process of ignition. The moment they come in contact they start reacting and burn. Examples of hypergolic fuels are monomethyl hydrazine (MMH) used as the propellant and N2O4 (nitrogen tetroxide) used as the oxidizer. This fuel works efficiently for maneuvering space missiles.
Modern form of ballistic missiles uses solid fuel rather than the liquid fuels. The prime advantage with solid fuels is that they are easy to maintain and store. Space shuttles use two solid boosters, which can be reused. Each booster is loaded with 453,600 kg (1.1 million pounds) of propellant. The propellant is powdered aluminum (16%) and iron powder (0.07%) and the oxidizer is ammonium petrochlorate (70%).
Ballistic missiles can hit their targets within 15-30 minutes of their launch, even if the target happens to be on the other side of the planet. They are designed systematically and carefully since they are essential for the national security of any country.