Why does it take so much fuel to launch a rocket? We know that rockets need to be used as oxidant when they are launched, but about 2 1% of the atmosphere is made up of oxygen. Why can't we just use the oxygen in the air? In fact, the main reason is that the atmosphere can provide high enough oxygen to support high-energy systems such as rocket engines or strong explosives. For example, the F- 1 rocket engine that powers Saturn's first stage consumes 1789 kg per second. At sea level, you need 1383 cubic meters of air, and you get so much oxygen every second. If the oxygen in the air is completely insufficient. In addition, 79% of the air is not oxygen, and the rest of the air will burn with high energy and need a lot of oxygen.

So it is impossible to provide enough oxygen from the air for five rockets to burn fuel at a very fast speed. The most important thing is that the air is diluted to a high level. At the initial altitude of 20,000 feet (the height of Saturn rocket is only 55 times), the air density will drop to 4% of the space, and the oxygen in the air will also drop. Of course, someone will ask the rocket. They can ask about the lack of oxygen in the rocket air. How can a jet plane fly? In terms of efficiency, jet engines have great advantages in launching rockets in space. They can cruise most of the time at any altitude and speed, which is the best compromise between resistance and fuel economy. They don't need to go into space, so they don't need to accelerate to Mach 20 and climb to the oxygen supply. This means that they can take in oxygen at a slow enough speed, and then use the quality of air to promote oxygen.

The famous Rolls-Roystrerent 1000 gas turbine fan generates 285-33 1 rod thrust (64 100-74400), accounting for about 4% of the fixed F- 1 rocket engine. Because of this, it can inhale 1.25 tons (900 cubic meters) of air per second, but only a small part of it is compressed and burned with fuel, and the rest is the reaction mass of engine thrust. Such an engine only needs a jet of 0/5-20 gallons per minute, and it needs about 400-600 gallons of air. It is easy to provide power by sliding and compressor. Unlike rockets, their thrust hardly emits exhaust gas. In contrast, exhaust gas is used to turn a turbine, which drives a large fan, and the fan quickly enters the air.