skibum157

Hey guys, I'm new to this forum, but I've created an account to ask you guys for some help. This summer I'm in charge of testing the communication system for a cubesat and one of my tests calls for the use of a weather balloon to create the separation that we will see in orbit. The thing is, I have no experience with weather balloons. I need to tether a balloon around 150 feet (thats the maximum height I can tether without getting the FAA involved) which will allow my radio communications to clear the 1st fresnel zone through about 14 km of separation. My main problem is choosing which balloon I need and determining the amount of line I will need for a stable 150 foot tether. The payload will be about 3 lbs. All the online resources I've found have been more concerned with free flying weather balloons, and I figure I could use a much smaller balloon if I don't need nearly as much height, but what do you guys think? As for the line I need, I've written a matlab script which tells me about how much the wind will push the balloon depending on the wind speed and the ultimate dimensions of the balloon that I use. However I'm using a lot of simplifcations (drag coefficient for the balloon approximately .45) so I'm not 100% sure how accurate the result will be. If anyone has any input on either aspect of this problem, I'd greatly appreciate the help.