ELI5. If the weight of rocket fuel is so important, why do SpaceX boosters waste a ton of fuel landing themselves?
In: Engineering
~95-97% of the rocket **to orbit** is fuel. The primary reason is in order to use fuel at a higher delta V you also had to burn energy to get the fuel there in the first place. So the rocket effectively has to burn fuel to raise it higher in the orbit so its available at that higher orbit to burn. The math barely works with chemical fuels which is why we STAGE our rockets and build them as light as possible.
For SpaceX roughly ~70% of the cost of the rocket is in that first stage (the most engines, biggest tanks), but this segment separates in the launch at a much lower delta V (lower altitude, slower speed). The penalty for having extra fuel in this stage is not nearly as devastating as having extra fuel in the 2nd stage (one of the reasons SpaceX gave up on that with Falcon 9).
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