I have been working with spreadsheets to estimate the mass and performance of spacecraft in the Sublight Universe. But over time, those spreadsheets have become increasingly hard to maintain. Also, being Microsoft Excel, strange things happen when I'm not looking at them.
After having yet another starship go pumpkin, I have decided to formalize my starship performance estimator into an easytouse browser application.
Rocket equations are pretty complicated. So before we start fiddling with exponets and running nonlinear equations backwards, we should nail down all of the details that we don't intend to change. Ships are build for a purpose, and that purpose takes precedence over every other consideration.
Gross statistics for the vessel
If this is a science or reconnaissance mission, what sort of equipment are you dragging along, and how long will you be observing/patrolling/spying? Does you ship carry cargo?
When estimating tonnage, here are some figures:


How many people are going to be along for the voyage?
Crew Calculation DetailsHere is where we spec out the reactor and engines to use
Reactor Calculation DetailsPutting in the reactor, engines, and other fun stuff
We are playing a guessing game with physics. The heavier our space craft is, the more engine we will need to get it up to the speed we want it to go. But the curves on those equations are notexactly easy to estimate. So we start with a guess, solve the equation, and then keep refining our guess until the calculated mass of the ship matches our hunch.