The day is finally here, the day that we have been dreaming of for months now. It was time to fly our solar balloon! The sun is hot, the wind is present but manageable, and the skies are clear. We arrived at a local park at about noon on Saturday and immediately started filling up the balloon with an nervous excitement that is to be expected with a maiden voyage. The wind was slightly gusty so while we were waiting for the wind to die down, we scoured the surface of the balloon, patching any holes we could find. Because the wind was blowing decently strong so we were forced to hold the balloon down in an effort to limit the pull the wind had on the large surface of the balloon, however, as a result, we couldn’t get a good idea of exactly how much lift was being generated. In fact, we were considering refilling the balloon with hot air to try to boost the lift a little higher. We honestly didn’t think it would fly very well, not with the thermal test from last week and the amount of air that had leaked out of the balloon by this point. By rough estimate, the balloon was only about 3/4 full when the wind finally let up enough for us to give it a test flight. We made sure the balloon was tied to the fishing line which was attached to the fishing pole we used to control the balloon while it was in the air, and it was time for a test!
When we finally let the balloon go, it beautifully formed into a sphere and instantly started rising, much faster then our last balloon did. We knew that we needed to keep the balloon under 300 feet for legal reasons so after only going up maybe 200 feet, we locked the fishing line so it wouldn’t fly any higher and that is when it happened.
At first, I didn’t know what happened but it soon became apparent that our fishing line broke and as a result, we had lost control of the balloon. In hindsight, using a small Gage fishing line to hold a balloon designed to lift at least several kilograms was not a very smart idea, but this balloon was about the same size as our last balloon and that sting had handled the stress beautifully so we didn’t think anything about it. In desperation we chased after our balloon as it continued to rise, hoping that it would sink to an altitude that we would be able to recapture it. It quickly became apparent that not only were we not running fast enough to catch the balloon, but it had no intentions of returning to the earth anytime soon. Even chasing it in a car would not have been plausible as it quickly rose higher and higher, quickly shrinking unto the blue sky, leaving us with nothing to do but take pictures.
Our feelings at this moment were very mixed as the balloon worked much better then either of us had predicted it would. As I said earlier, just before we released the balloon, we were about to go reinflate it with hot air to try to make it fly better. The fact that it had enough lift to break our line was exciting because that meant that our balloon was working as good, if not better then intended. That feeling was mixed however as we were watching over 7 hours of hard work float away into the sun.
The experience was not a total waste either because we now know that, while a sphere generates the most lift of all the shapes we could have used, it is not the easiest to make. Andy has, on his own, make rectangular balloons of similar size in only a few hours while a sphere took two people over 7 hours to complete. Also, we now know that we need a stronger rope to hold our balloons how with. Right now we are researching the possibility of using paracord or deep sea fishing line for our next balloon. In the meantime, however, we got to enjoy watching our balloon shrink into a dot in the distance and then finally disappear in the clear blue sky. I hope you found this post interesting, we will be doing more building in the next Solar Balloon post so if you are interested in that then I hope to see you in the next one. Untill then, Happy Tinkering!
This week I decided to test a concept for a unique parachute system I had seen used in model rockets before. The general idea is to deploy a giant streamer to produce the drag instead of a traditional parachute. The idea seems sound, there is still lots of surface area to produce drag so it should work. I know the idea work too because I once put a streamer on a model flying airplane so my dad could fly his airplane through my streamer, just for fun, and even though the airplane I was using was usually overpowered to the extent that it could accelerate while pointing straight up. However, when we attached the streamer to the plane, it struggled to move forward fast enough to maintain flight.
This is great and all but I wanted to see if I could use this concept on a smaller scale. As a testing platform, I decided to make a blowgun out of PVC and copper wire. The PVC was the barrel and I made a cylinder out of the copper wire to use as the projectile. The copper itself didn’t fit well enough so I perfected the fit with lots of tapes so there would be a good nearly airtight seal with the inside of the PVC.
At this point, I was ready to make my parachute. I started by cutting a plastic trash bag into strips about 1.5 inches wide and taping them together to make a very long streamer. I attached that to the end of my projectile and spent about 5 minutes stuffing the whole thing into my PVC barrel. However when I went to test it, I ran into a problem that I would be facing a lot with this project, the streamer was packed in so tight that I could not muster enough air push the projectile out of the PVC. The problem is that there was so much plastic touching the wall of my barrel that no matter how I folded it there would be so much friction that I would not be able to muster enough force to move it with just my breath.
Next, I decided to try to shorten the streamer to about ¼ of the original size. At this size, I was able to shoot the weight out of the barrel with enough velocity to send it flying down my hallway and slamming into my wall. I got lucky as there were no holes in the wall but I would recommend all blowgun projects to be tested outside. This success was a double-edged sword because while it allowed me to shoot my weight and proceed with my tests, the streamer was not slowing it down any appreciable amount. To try to combat this, I cut the rest of the tail I had already cut off into three more pieces and attached it to the back of the projectile with the original part of the tail. The idea was that the added tails would allow the drag to be increased and still let it get shot out of the blowgun. This was an incorrect assumption and I was completely unable to shoot the dart again.
I tried removing two of the streamers and while I was now again able to shoot the projectile, there was again no appreciable difference in the velocity of the weight. As a last ditch effort, I tried attaching the removed 2 streamers to the front of the weight and fitting those down the barrel in front of the main projectile. This took a long time to do but did allow me to actually shoot the projectile with just the power of my breath, again however the velocity of the projectile was almost entirely unchanged.
Upon further review, I think my problem was with the setup of this experiment, not with the experiment itself. Drag, at least air drag, is partially dependent on velocity. This is why when things fall they reach a terminal velocity because at that point the drag caused by the air is equal to the pull of gravity and equilibrium is achieved. I think that the reason why the streamers didn’t work better is that they were moving relatively slow compared to the terminal velocity of the system and so they couldn’t provide enough drag to be noticeable. The weight of my projectile also didn’t help any. Had I redone this test by launching something out of a model rocket and so allowed the streamers to reach terminal velocity then I could have seen how effective they were in slowing stuff down but because I wanted to make this home scale the project was ultimately a failure but a good lesson learned.
I wanted to share project because of it a very important thing about tinkering. A failure is always an option. Part of what makes tinkering, tinkering, is the ability to change or scrap ideas on the fly. This project changed multiple times while building it and finally was determined to be a lost cause. Could I have fixed these problems and found a solution that works, yes, but that would have required more time and effort that I was willing to expand on the project? Failing is the bread and butter of tinkering. When you succeed you learn one way to do one thing but when you fail you learn one way that a concept doesn’t work and that can be much more broadly applied to multiple topics.
I hope that you enjoyed this project and I hope you will join me for my next project. In the meantime though, have a good day and Happy Tinkering!