Magnetic Apogee Detector Kit

The kit is easy to assemble in 30 to 45 minutes, using a fine-tipped low-wattage soldering iron. A 15 watt soldering iron is readily available from Radio Shack and works well for this kit. Latest revision includes a continuity tester.
 

- Robert Galejs, 2000

The Earth's magnetic field may be used as a reference for the model rocket recovery deployment. A flight tested magnetic apogee detection sensor is described, complete with a schematic diagram. This design is simple, inexpensive and appears to work reliably. This new device senses the rocket's orientation with respect to the Earth's field and triggers ejection when the rocket noses over near apogee. I am very happy with its performance and I am currently building a PML Pterodactyl Jr with magnetic deployment for some high power demonstration flights. Will others be as enthusiastic about this new sensor as I am? I certainly hope so, but only time will tell.

This angle varies from about 60 degrees in the south to about 75 degrees in the north. Since the magnetic field has a large vertical component, it is possible to use it as a reference to sense a rocket's orientation and to set off an ejection charge when the rocket tips over at apogee.

The field lines originate at the south magnetic pole and terminate at the north magnetic pole. The angle that this field makes when it intersects the Earth's surface is known as the inclination angle.

Nearly everyone is familiar with the horizontal component of the Earth's magnetic field. It is this component that allows compasses to point north. Over most of the Earth, this horizontal field is only a small component of the total field.

Imagine using the magnetic forces of the Earth itself to control your rocket! With the Magnetic Apogee Detector by Professor Robert Galejs of MIT you can!