Why do we still expect “successful failures” on rocket launches and not just scale up or scale down the same design on successful rocket ships and launch pads to make bigger or smaller ships with more stable structural material?

Question

Why do we still expect “successful failures” on rocket launches and not just scale up or scale down the same design on successful rocket ships and launch pads to make bigger or smaller ships with more stable structural material?

In: 1598

Answer 1

If you double a rocket’s height (see edit), then the area of things goes up by 2^2 = 4 and its volume goes up by 2^3 = 8. Significantly it’s weight (which is a function of volume) goes up by 8, but the amount of fuel which goes through a pipe (which is a function of the cross section area of the pipe) only goes up by 4. So you’d need to increase the speed the fuel is moving, which requires a stronger pump and higher pressure in the pipe which means…

And there are countless other systems which have similar problems being scaled up. At some point you need to build the thing full size and test it.

Edit: as well as doubling the height, you do, of course, also need to double the other dimensions (radius or depth and width) which would keep it a scale model as OP was asking about.

This concept is known as the square/cube law.