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Curve_One Setup

Components were chosen based on weight, availability, price, and effectiveness.

 

Camera: Needed to run off AA batteries or have a means of supplying light-weight external power. Needed to have an intervalometer function for taking photos at specified intervals. A Canon PowerShot A590IS was selected because it fit within budget, was within the minimum image quality specifications, it's light weight, easy to find on Ebay, and can be modified using the Canon Hack Development Kit (CHDK) to add the intervalometer feature. At $99, it seemed like a good deal. Using an 8GB memory card, this 8 megapixel camera would allow photos to be taken every 8 seconds with storage space to spare. One downside was that I couldn't access the intervalometer function and then turn off the LCD screen, which needed to be off to conserve battery life; I had to turn off the LCD and then navigate through the menus blindly to turn on the intervalometer.

 

GPS: A Motorola i290 boost mobile cell phone, purchased from Ebay for $14.99, was used as the GPS tracking device. It too was inexpensive, lightweight, and was easily available. Installing a program onto the phone allowing the GPS location to be tracked via InstaMapper.com. Power was supplemented for the phone using an Energizer AA cell phone charger purchased for $14.67. Note: Although a phone was used as the tracking method for Curve_One, I recommend using something more powerful to help aid in the tracking and recovery of the payload; cell phones are inexpensive and relatively reliable, but they're a lot less reliable than a true GPS tracking/reporting device and they also provide very limited flight data. Most importantly, if it lands in an area without cell phone coverage, you likely won't recover it.

 

The camera and phone were attached to a bicycle and driven around Philadelphia. Next tests were done while driving from Philadelphia to Pittsburgh. Both components worked for many hours longer than was necessary and the GPS accuracy was remarkable.

 

Payload: A small, strong, 1-1/4" Styrofoam container was donated... Cost: Free! After identifying the positions of the camera, phone and charger, a hole was cut through the container wall for the lens. Next a piece of packing insulation from a frozen shipped parcel was recycled; it was cut to fit tightly within the payload while still accommodating the components. Specific care was taken to cut away areas of foam that would depress buttons on the phone or camera, but would still secure them from jostling during flight.

 

 

Balloon: A 500 gram meteorological sounding balloon was purchased for $45.00. The 500 gram was chosen based on payload weight and desired elevation. The balloon would be filled to approximately 5.3-feet in diameter to achieve the desired ascent rate.

 

Helium: 80 cu.ft of helium was purchased from AirGas for around $38; the utilized volume of helium was less than 80 cu. ft, but this was the closest size to the required amount. The quantity of helium was identified based on the payload weight and anticipated ascent rate. This was one of the most complex and important components of the project and should not be overlooked. Given the known weights of the setup components, and given a specified ascent rate, the amount of helium required to provide sufficient "free lift" was computed using the Ideal Gas Law (PV=nRT.)

 

Parachute: A parachute with a weather balloon attachment was purchased from Spherachutes for $24. It was manufactured 'to order' with alternating neon orange and white colors for high visibility. The weather balloon attachment allows the top of the parachute to be connected to another rope that runs up to the balloon. The parachute was tested by dropping it fully loaded off a tall building, verifying that the components were intact, and that observers on the ground didn't perceive the decent rate as a threat. (I would have rather had someone drop it and me try to get hit by it so that I could verify that no harm would come to someone hit in the real flight, but no one else wanted to go up and drop it.)

 

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