I came up with the idea for rocket cars a while after my Dad got me a model rocket set. The airborne rockets were fun, but it was hard to find a place that had enough open space to recover them, and high winds always made recovery even more unlikely. The great thing about the cars is that they just need a long stretch of smooth pavement. We've even launched them in the pouring rain and at night.

The Track

One thing I figured out from the start is that the cars would need to be guided along some sort of track. I also knew that the cars would probably get moving pretty fast, so the track would need to be long. Using fishing line attached to the launch base and the end of the track is a cheap and easy way to achieve this. The launch base and the end of the track both need to be heavy enough to stay put when pulling the lines tight. The cars are actually pretty good at stretching the lines and veering way off course.

The Launchpad

The launchpad is a simple backboard which holds one end of the track, and keeps the blast from getting everywhere. There is a big metal ballast to keep the tension of the lines from pulling it along the ground.

Track End

The end of the track is held down by a board that also has metal ballast.

Electrical System

The electrical system that the airborne rocket kit came with used 4xAA batteries, creating 6.0 volts. I chose to go with a large 6V lantern battery so that multiple cars can be launched at the same time. I also wired the pad to hold a second battery, which I may use when launching three cars, just to make sure they all get the juice they need.

Wiring diagram for rocket cars.

The Cars

The cars are made from lightweight materials to make them fast. Both cars pictured below weigh under 150 grams. The black car is carved from a piece of wood, and the metal car is made from thin walled square tubing from a hobby store. The cars are inexpensive to make, which is a good thing because they may not last long. There are other cars that have been used which broke into several pieces on the first launch.

Safety

The rocket cars are pretty safe, as long as you don't stand right next to them when launching. They don't weigh enough to really hurt if they were to somehow become a projectile. There was one time that a car broke the line and landed in a ditch with dry grass, which then caught fire, but even then it was stomped out in seconds. Besides a bottle of water and a band-aid, there isn't much in the way of safety equipment needed. It says on the packaging that the rocket engines come in to not fire them at angles greater than 45° from vertical, but because the cars are on a track, this can be ignored.

Pictures

Pictures of the rocket cars can be seen in the images section.

Launch Videos

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Page last modified on December 29, 2009 16:55:45. (ID=86)