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).
As for technology level, I am thinking something like 300-400 years in the future. I want to create something with elements of space opera, but based more on hard sci fi/realistic constraints. Because FTL is out, I am imagining a solar system where travel between plants and satellites is relatively easy and quick (like a few months to outer solar system instead of years), where the OORT cloud is the untamed frontier, and if humans have left the solar system, its only in generation ships which effectively are cut off from the rest of humanity.
Edit After digging around on the site that Jim2B listed, I found this excellent section on interstellar trade: http://www.projectrho.com/public_html/rocket/basicdesign.php
There are a couple of paragraphs on estimating the size a ship based on the tonnage of its cargo, which could of course be used to calculate tonnage from size. This is really perfect for my purposes, because even though I asked about mass specifically, the real problem I am trying to solve is how large do ships need to be to accomplish "x" task. I was probably going about it slightly wrong as I was trying to think in terms of "how large is a plane, or an ocean liner, or a battleship, etc." The approach from Atomic Rockets is much more systematic.