>>12760516>>25,000,000 ton ship to Alpha Centauri25,000,000 tons is the same mass as 250 USS Ronald Reagan aircraft carriers. The carriers each carry ~6000, so that'd be 1,500,000 people.
Another way to think about it: 25x10^9 kg; steel weights 8000kg/m^3 So if the whole mass was built into spherical meter thick steel shell it would have a diameter of 1000m. If you had 1.5m passengers, the average volume each could live in is 333m^3. For context, the average American house is 63 m^3, so the spaceship is 5x as much room.
If the steel only needs to be 25cm thick, a 25mton shell would have a diameter of 2000m, and each passenger's average living space would be 41x the average American house.
The world produced 1800mton of steel in 2020, so this ship would take about 1% of the global output. If steel costs $600/ton, it'd cost $15b for the ship.
