Calculators and Tools

Below are various tools and pages from the first version of this website, when the project was different. They are still useful but don’t fit easily into the structure any more, so they are gathered here.

Tether Tool

Pick values for a vertical skyhook around your chosen planet or moon, get a list and graphic showing all its key characteristics.


See where all the nearest stars are in relation to the sun

Engine Search

Pick parameters and see what rocket engines are available and how they compare

Pellet Simulator

A trajectory plotter that shows how a large number of objects with slightly different initial conditions diverge in orbit over time. Slightly hypnotic.

Rocket Lessons

The basics of orbital mechanics and the rocket equation


A previous incarnation of the long range future envisioned in Moonwards.

Javascript code used in these tools

Each button will load a page with the text of the javascript used in these calculators. As it is a text file, your computer will not treat it as code. You can review the code on the new page, or copy it and paste it into an editor of your choice so you can see it displayed with proper Javascript notation.  You will need to turn on that notation in your editor or save the file as a .js file.

  • This script can be used to calculate Hohmann transfers
  • This is a thorough database of all the major properties of all major bodies in the solar system, including planets, dwarf planets. moons, and major asteroids.