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Question
My high school rocketry class is building a rocket that is powered by a hypertek k-240. Our altimeter does not have a way to set off our ejection charge, and we can not get one that can. How do we set off our ejection charge???

Answer
Joseph -

Have you looked into AdeptRocketry (http://www.adeptrocketry.com/)?  They have altimeters that can stage ejection charges.  I have one that goes off at apogy to break the rock in two, making it tumble back down, and a second that goes off at 250' AGL.  Given what you have invested in your project, these are modestly priced and the best way I have found to stage and deploy my parachutes.

The only other way would be to use the ejection charge off the motor, but this would only allow for one deployment at altitude, and then you are at the mercy of the winds to locate and recover your rocket.  That's why I love the two-stage approach.  It allows the rocket to tumble straight down before main chute deployment, keeping the rocket close to the launch field.

I hope this helps.

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James Bell

Expertise

I am a member of Tripoli Rocketry Association, and am certified to fly hi power rockets. I can answer questions anyone may have about design, materials selection, stability calculations, motor selection, altitude and performance predictions, and parachute and recovery options.

Experience

I make my rockets from existing kits or parts readily made through commercial channels. I do NOT make my own motor propellants (they are challenging enough even for the companies that do this for a living), and I do not advocate making rockets using "typical household item" such as paper towel rolls.

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