Wednesday, August 14, 2013

Another Approach to using Estes Alti Trak

In doing experiments sometimes a helper is really needed but I often try to figure out ways to do everything myself.  I have been experimenting with determining the maximum height of a water rocket launch and progressed from the protractor method to using the Estes Alti Trak device which I had mentioned in previous post.

Trying to use the Alti Trak by myself I was limited by the 25 feet of string on my PITSCO Aquaport launcher which gave angle readings approaching 90 degrees when you are so close to the launch. My solution was to attach kite string to the Aquaport string so that I could get 100 feet away on launch. This time I recorded my air pressure level also and always pumped to 80 psi, my altitude readings from the prior launches might have been done at 100 psi. Altitude calculations were significantly lower this time at around 200 feet as opposed to 377 feet on the previous outing.

Estes Alti Trak

Kite String Extends Launch String to 100 Feet

Trying to think like a scientist I try to identify all of the variables.  First there was the issue of launching too close the first time and the inaccuracy of getting an accurate angle reading for the top of the launch when it was close to 90 degrees. Then there was the launch pressure difference it could be that launching at 100 psi could give significantly more altitude, I plan to always record the pressure in the future. The amount of water I used in the rocket could differ also. Another factor could have been that one fin of the rocket was loose causing extra drag, I noticed this later and switched to a different rocket.

Pumping to 80 psi

Even if there are many possibilities for inaccuracies in this method of measuring maximum altitude I think it is a good learning exercise. First it is a basic introduction to a practical application in trigonometry using the tangent function. It gives the student a good exercise in recording data and thinking about variables. It would be fun to launch different rocket designs and compare the maximum altitudes.

Bill Kuhl

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