Here are some useful tools i made for my own reference while worldbuilding. They are only loosely accurate and probably contain bugs and errors. If you are an astrophysicist and you use this to plan your mission it is your own fault if it crashes.

Communications time calculator

Three hundred million metres per second — it’s not just a good idea; it’s the law!

Porkchop plotter

A porkchop plot shows how expensive a trip from one planet to another will be in terms of delta-v¹ depending on when you set out and when you arrive. This doesn’t matter so much in the outer system, where most transport is via titanic torqued-up torchships that can get you anywhere, any time, so long as you don’t point the exhaust the wrong way and kill millions of people, but in the inner system, where distances are comparatively lesser, ships less powerful, and waiting times not so bad, waiting for the right launch window is everything.