iPhone Applications

Princeton Satellite Systems has developed several iPhone applications. QuaternionCalc is currently available for download on the Apple App Store.


QuaternionCalc is a utility for performing mathematical operations involving quaternions!

Included quaternion operations are:

For more information go to QuaternionCalc help. QuaternionCalc uses the Princeton Satellite Systems MatrixLib framework for iOS.


ChessNotePad is a chess recording and playback application. It can be used anywhere you would use paper and pencil to record chess games.

ChessNotePad records games in PGN format as you and your opponent play. Forget pen and pencil! Once a game is complete, you can save it for later viewing and optionally email it to yourself and the opponent. You can also download or paste PGN games from the Internet and save them for later viewing.






Frequently Asked Questions

ChessNotePad App Frequently Asked Questions

Outer Space Defense

Outer Space Defense is a game designed to teach relative orbit dynamics. Plays great natively on both iPhone and iPad!

This game poses an addictive test of skill pitting your mastery of spacecraft orbital control and prowess with a laser against multiple attacking enemy satellites. See how long you last against a relentless enemy that launches satellites designed to take you out at a faster and faster pace!

You are one of a group of elite satellite operators tasked with controlling one of your country's few remaining surveillance satellites observing the enemy. In order to maintain surveillance, the satellite must be kept as close as possible to its optimal orbit. Watch out though, the enemy constantly sends killer satellites intended to destroy your surveillance satellite. You must avoid these or destroy them with your onboard laser. The longer you last, the faster they come!

As you thrust to maneuver, you use up fuel and as you fire your laser, you run down its battery. Luckily, orbiting fuel depots can replenish your satellite if you get close enough to them. Manage your resources to maximize your points.

Real orbital mechanics and control algorithms govern the motion and abilities of both your satellite and the enemy satellites. Make sure you don't stray too far from your optimal orbit. The closer you stay, the faster your points accumulate and if you get out of control, it's game over!

Three different thrust control modes: tilt-to-thrust, thumb sliders, or directional touch. Two different laser fire control modes: joystick plus button, or joystick alone.

Interested in learning about the theory behind the game? Click here to download a brief description of the coordinate systems, equations of motion, relative orbit dynamics, and control methods used in the game.

Satellite Smash

Satellite Smash is a space game using real orbital dynamics!

Your spacecraft is in a two-dimensional orbit around the Earth. You change your orbit by changing the velocity of your satellite in either the tangential or radial directions and try and catch space debris. Watch out though! At the same time attack satellites are trying to crash into you! You only have so much fuel and when it is out, or you have been smashed, the game is over!

For more information go to satellite smash help. Satellite Smash uses the Princeton Satellite Systems MatrixLib framework for iOS.