Saturday, April 18, 2009

Water Rockets Night Flight

This week, we had some really good weather and the ice finally disappeared from our primary launching site. We decided to get out and have a little fun and test out the launchers we have built over the winter for a local scouting group.
We have been playing around with an amusing little idea for flying a rocket at night and using a high-intensity LED strobe to track the water rocket. We were inspired by seeing some local car clubs running some special tire valve caps with LEDs built into them.
We were able to find these little lights in a local auto parts store. The ones we found are called "Tireflys" and they were only about $10 for a pair so we decided to get some and see what kind of entertainment we could make from them. We hope you all can see how much fun we had with this little experiment and get out there and have some fun of your own. Perhaps There is something you and your team have been thinking about doing and we encourage you to get out and try it!

We found out that these cool lights come in several versions with different colors and different blinking patterns. We picked out a set that used a multi-color LED array that strobes red, white, and blue LEDs in sequence as they rotate. We figured that the colors of the U.S. Flag was an appropriate choice for our patriotic team!

After we returned to the shop, we dismantled the lights to see how they work. An internal mechanical g-switch inside is activated by the centripetal force of the spinning tire and it activates a timing circuit that flashes the LEDs for 20 seconds after the switch is closed. Sadly, the timing isn't proportional to wheel speed or anything, but what do you want for $10?
We first put a tirefly light on a bike wheel and spun it up in the dark as an experiment. We got to see how they looked and and we played around with it to try and figure out the best camera settings to capture still photos of the lights in action. It was very difficult to get good pictures even after a lot of experimenting.
We think that a long exposure with a tripod would help, We will bring a tripod for the camera next time and we have a remote shutter release called a "bulb" on order, so we will be able to get better pictures soon.
The following images of our launches turned out better than we expected. It's difficult to hold the camera steady for a long exposure and to keep the camera image framed correctly when looking at a small lighted object through the viewfinder.
We discovered that tapping on the rocket to get it flashing would provide enough light to get the photo framed. Then it's just a matter of holding steady until ready to launch and open the shutter and launch then close the shutter. This is similar to the methods used for astro photography and weather photography.

We discovered that we need to eventually make our own. Strobe circuit after only 2 launches. The problem we had is that it became too dark to locate the rocket in the water after the strobe shut off automatically. Once the flashing shut off we could no longer locate the rocket. We're glad we had the chance to have some fun and make a couple of cool photos.
We hope you enjoyed our little experiment and you will try some experiments of your own. Next time we will return with more of our launcher tutorial! (Unless we become distracted with another fun diversion)
Until next week!

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