Friday, January 07, 2005

Ad astra

My son and I flew his first successful rocket a few days ago. It's powered by a mixture of vinegar and baking soda. The air rocket never took off, and the water rocket went all of two feet. But the vinegar rocket soared to 25 feet, despite some fuel mixture problems. I think we can easily get it to 100 feet.

Soon after the flight I began thinking of designing a new fueling and launch system. The current rocket relies on you turning it over to empty a bay of (dry) baking soda into the vinegar, then placing it down on the ground and stepping back. The pressure of expanding gas builds, and the cork pops and the rocket flies up. But our baking soda did not all dump out into the vinegar, because the tube that held it was damp, causing the powder to clump.

And I got to thinking that modern radio-controlled servos should be capable of remotely triggering the mixture. Ideally, both fuel elements would be liquids, which would enable a gravity-release mechanism to enhance their mixing.

I just performed a crucial test in the kitchen: I mixed vinegar with baking soda powder and it fizzed, and I had my baseline. Then I first mixed the baking soda into water, then dumped it into the vinegar, and it fizzed even more! This test was important for me, because I did not know what would happen to the baking soda when mixed with water, if it might lose its strength.

So picture this: The rocket contains two internal bays for holding liquids. The fueling gaskets are stiff rubbery tubes that puncture the airframe of the rocket. It requires mechanical force to insert the fueling, uh, pitot and fill the internal bays. The bays can be emptied by force of gravity once the servos open the tubes leading into the reaction chamber of the rocket. This all sound very complicated, but it's not. No, I'm not going to make a drawing for you. The boy and the dad fuel the rocket, then step back and flip the switch that sends the signal to the servos in the rocket. The fuels come down and mix, the pressure builds, the cork pops out, and the rocket soars. Yay! Dad can even attach an altimeter that deploys a parachute.

The dad enjoys himself immensely while the boy wanders off and plays on the swings?
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