Planetary Transfer Calculator

A solar system simulator that can calculate transfers between planets, moons and stars.

What it does

An overview of  what the program calculates.


How to use

Details on how to use the program and the user interface.


How it works

Details of how the program works, in terms of both code and orbital mechanics.


Not Only a Calculator

The program also has detailed and beautiful planets, with shadows from the mountains and reflections off the water. Non-spherical asteroids and moons have detailed 3D models.

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Transfers Between Planets

The calculator can determine the trajectory of a transfer between planets. This trajectory is ballistic, the rocket engine is only activated at each planet to start and end the trajectory. The system calculates (for an optimal ballistic transfer) the start time of the transfer, the transfer time, the needed change in velocity, and the orbital parameters fo the transfer orbit.

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Transfers Between Stars

The calculator can determine how long a semi-powered interstellar transfer would take, from both the Earth’s reference frame and the ship’s (due to relativistic time dilation). The system uses an acceleration-coast-deceleration profile, with a constant proper acceleration. It takes in the acceleration time, the proper acceleration, and the distance travelled.

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The Team

Minerva Predavec

Programmer and Designer

Easter Eggs

How to unlock

There are a few ways to unlock the Easter Eggs in the calculator. One is typing “kerbal” , “starman”, or the Konami Code. You can also look at Eros (under minor bodies) or Iapetus, the moon of Saturn (under minor satellites). Once you do any of these, all Easter Eggs are enabled.

2001: A Space Odyssey

The Monolith on Iapetus plays Also Sprach Zarathusa when you look at it.

The Expanse

Adds bodies from The Expanse (the toggle is on the bottom left), speeds up spin rates for Eros and Ceres, and adds high constant thrust transfers under Epstien Drive.

Elon Musk’s Roadster

Shows the Roaster’s trajectory after the Falcon Heavy launch (under minor bodies).


Adds the theoretical location of Homestead II, and includes a document on the science and engineering flaws on the Starship Avalon.