Aircraft Vs Spacecraft

Passenger planes uses air to fly . What incase of Fighter jets ? if there is a difference please explain ?

It all depends on the type of engine that is used.

A turbojet engine is used with passenger planes and the engine works by sucking in air and hence these planes need a longer runway to take off.

A helicopter on the other hand uses a turboprop engine, which has a large propeller , and this takes off instantly due to the thrust provided by the propeller, coupled with the reaction thrust from the nozzle.

Missiles use engines like ram-jet engine or pulse-jet engine. These engines need to be provided with an external source of high velocity so that the inlet mach number is greater than 1. hence they have to be "launched" and cannot be operated individually.

Now i do not know what type of engine a fighter plane uses, and i have never seen them taking off.

punitbansal

As the name implies aircraft requirs air but a spacecraft doesnt really need air to fly.
Spacecraft uses reaction propulsion but an aircraft sucks air and uses this air for propulsion.
Other than this spacecraft are designed so that they can be pressurized with no air at all outside.

If you consider a space station or any of the artificial satellites orbiting the earth, they are not flying at all. They are in a state of free fall. The tangential velocity imparted at the time of deploying ensures that the craft is at a constant distance from the earth. If this velocity is lost the craft will eventually crash back on earth. Some times small CO2 jets are used to correct the orientation or velocity in order to maintain orbit. Even for a moon shot the craft is just lobbed into space. Thereafter it just keeps going like a thrown stone. It is only at the destination that correction engines are used.

On the other hand, conventional air craft remain aloft by the lift created by the air foil shape of the wings and the wind velocity over the wings. Propellers create this velocity by blowing air backward. Jet engines create a thrust by burning fuel in air and throwing the products of combustion out in a defined jet.