Why are the chopsticks so important after SpaceX already landed rockets?
In: Planetary Science
Steel has a much higher tensile strength than compressive strength. In other words, steel is a lot stronger when you’re hanging something from it than when you’re trying to sit something on top of it.
The landing gear on the Falcon series of rockets adds a lot of weight to the overall rocket, which reduces the amount of payload or range you can get for the same amount of fuel. Changing the landing gear so that the rocket “catches” from the top and then hangs plays into the material properties of steel – you shift the steel from supporting the weight of the rocket by compression to supporting that weight by tension. Because steel is stronger in tension than compression, you get more carrying capacity out of the landing gear for the same amount of steel.
But why use the same amount of steel if your landing gear is stronger? A rocket doesn’t get bonus points for the landing gear being able to hold up twice the weight of the rocket. All it needs to do is to hold up the weight of the rocket. That means that you can now use less steel in the landing gear (and possibly throughout the rest of the rocket as well).
That, in turn, means that the rocket now weighs less. If the rocket weighs less, than you can get more payload capacity or range for any given amount of fuel. The entire point of the rocket is to maximize how much payload/range you get for a given amount of fuel.
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