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There are several differences between the engine of a space shuttle and that of a jet airplane. For one thing, jet engines take in air through the hole in the front of the engine. That air is then mixed around with fuel and burned in the combustion chamber. That combustion creates a lot of hot, expanding gas, which create thrust by pushing in all directions, but because there is a hole in the back to release the exhaust, it pushes harder on the front of the engine than on the back, which pushes the plane forward. A rocket, like that in a space shuttle, can't work the same way, because there is no air in space. This means there is no need for a hole in the top of the rocket to let in air. Instead, rockets store oxidizers inside, either in a liquid form or a solid form that's pre-mixed with fuel. To create thrust, the fuel and oxidizer are ignited in the combustion chamber, creating those hot, expanding gases again pushing against the inside of the rocket. There is a hole in the bottom of the rocket to release the exhaust, which means the gases will push harder on the top of the rocket than on the bottom, pushing it forward.