The LBCC Space Club launched our first high altitude balloon of the year this weekend. I was very pleased that so many of our team members were able to make it to the launch. It was a very hands-on morning preparing for the launch, as we hurried to repair our payload and pack our go-boxes. We weren’t as prepared as we could have been, but when Oregon weather gives you a sunny day in January, you launch a balloon. It’s just what you do.
This was a small 300g balloon with a simple raspberry pi camera payload and time-delayed cutdown based on the mechanical wheel design from MSU. We modified the cutdown to use an arduino Uno so we could easily control the delay without the weight or potential risk of failing to recover the expensive Irridium tracking payload.
Our goal for this launch was to improve our ascent predictions and get closer to the 5 m/s target we want for the actual eclipse. Our last launch in October (was it really that long ago?) failed to climb very fast at all, and we need to do better. This launch was marginally better but was still far too slow. We estimate the ascent rate for this payload at about 100-150 ft / min which is barely 15% of the 1000 ft / min we hoped to see.
We’re still trying to determine what we’re doing wrong during our lift measurements. We’re aiming for 30% more lift than the weight of our payload. So if our payload weighs 1,000 g, our goal is to fill the balloon until it measures 1,300 g of lift. For this balloon we tried using a digital fish scale to weigh both the entire payload, and the balloon while filling it.
One potential point of failure for this launch was that we did not have a hard point for the neck of the balloon. This meant that we could not remove the fill tube to accurately measure the lift of the balloon. We attempted to compensate by measuring the weight of the fill tube and accounting for it while making our lift measurements. Despite our efforts, it’s possible that we failed to fully or properly account for the fill tube.
Our payload came down on schedule 33 minutes later and landed in a field of blueberries just off Highway 20 between Corvallis and Albany. We chose a short cutdown time to make it easier to recover the payload, and because our goal for today was just to work on our launch procedures.
Despite our continued struggle for enough lift, the team had a great morning and a wonderful experience. We continue to improve the launch process and look forward to sending up more practice balloons.