I am trying to design spacecraft with realistic mass estimates, so that I can "accurately" design fuel requirements and calculate potential speed.

Obviously the mass of a ship is going to vary widely based on in its dimensions and purpose (a 500m long freighter will have a very different mass than a 500m long battleship). That being said, I am trying to come up with some reasonable estimates and real world comparisons so that I could quickly estimate the mass of any ship.

I have looked at the mass of nautical ships, aircraft, real spacecraft, and fictional space craft; the numbers seem like they vary so much that I am not really sure where to go from here.

Here are some rough approximations I have gathered so far as a starting point.

• The space shuttle (empty) ~= 75 metric tons.

• A 757 at take off ~= 100 metric tons.

• The ISS ~= 450 metric tons.

• The Seawise Giant (largest ship ever built) has a full load displacement ~= 654,000 metric tons.

• The Starship Enterprise ~= 4,500,000 metric tons (this seems absurd to me compared to the other measurements).