re: 500 meters
"Starting from a simple shape: 50' diameter 1" wall with
Aluminum 5083 which is 1640' [500 meters] long."
Since the at rest pressure is 12.7 psi and that's pretty low, it would be more efficient if it was a smaller diameter
If instead it was 40' diameter 1" wall with Aluminum 5083 which is 1640' [500 meters] long. So that's 206,088.3 sq' and 17,174 cu' times 168lb gives total weight of 2,885,236.
The 40' diameter pipe end has area of 180,955 sq inches, giving 15.9 psi.
That would be generally better.
And use 5' diameter pipes instead of 6'