With our last balloon drifting through the stratosphere, it is now time for us to look forward to our next project.
The first thing to work on is obviously the quality of our tether rope. Just out of simplicity, I think we have decided to use paracord to hold out next balloon, partly because it is so light, and partly because it can hold so much weight before it brakes. We may also look into the possibility of a second safety line or an anchor that can act as a fail-safe, just in case.
The next thing that we will be changing is the design of the balloon itself. As I mentioned before, a sphere is a very good shape to use on paper, but the problem is it is very hard to produce, making the construction phase take far to long to complete. To try to solve this problem, we decided to change the shape into the cube. A cube is geometrically similar in shape to a sphere but is also much easier to produce. Another way we are going to make the building process easier is by increasing the size of our plastic. We decided to buy some painting drop cloth, which we will use to make the walls of our balloon. this way we only need to fuse two pieces of plastic instead of +50. Because our drop cloth is clear, we are also going to be covering the inside with black paint pigment. It can be bought at Walmart for an only a few dollars and can make our balloon black and so able to absorb the sun’s energy as well, if not better, then the trash bags.
The next modification we wanted to try is one that we have seen on professional balloons but have not tried ourselves yet. That is to put a clear balloon over the black one. This will help us because as the black balloon absorbs the sun’s energy, it will radiate that heat in two directions, in and out. The heat radiated in is already being collected by the black balloon but right now all the energy being radiated out is simply lost energy. By adding a clear balloon outside the black one, we can collect the energy being radiated out as well, increasing the efficiency of our balloon.
The final thing we want to add to our balloon is a black box. Though we do not intend to lose a balloon again, our last outing has taught us that anything can happen. Because of that, we decided to add a sensor package to our balloon so that if we do lose our balloon again, we can find it when it lands. Our box will have several sensors to help know what our balloon is doing at all times.
- A radio tower based tracker. This is similar to what professional weather balloons use, it allows us to track the balloon based on what radio signals are picking it up. We decided to use this tracking device because it is more versatile than a GPS tracker and is also cheaper.
- A camera. One of the main goals of our last balloon was to be able to hold a camera so we can take pictures from 300 feet, just because it would be cool. Because we still want to do this, we are getting a cheap Go-Pro and putting it in our balloon, so that as we fly we can record our flight and hopefully get some good pictures. we chose a Go-Pro because it is smaller and tougher then other cameras and so can survive an impact better. (Even though we hope it never will need to)
- An altimeter. Though we hope to never lose another balloon, we do want to prepare for the possibility. To accommodate that wish, we decided to track our height so if we do lose another balloon and we recover it, we can at least know how high we went.
- A thermometer. Because temperature is so important in calculating our lift, we decided it would be beneficial to add a thermometer to both measures the temperature of the air inside and outside the balloon. This way, we can start to get a better idea of what temperatures we should use in our future calculations.
Because finals are rapidly approaching, both I and Andy agreed that we were too busy to build our next balloon right away. When we do, these are some of the changes we will be making and hopefully, we will get another successful flight. Until then, good luck with your projects and Happy Tinkering!
Now that all the math and production procedures are all worked out, it is finally time to start building my first solar balloon. The first thing that We needed to work out was how we were going to cut out the pattern correctly. We brainstormed using a projector and tracing that line to make out the pattern. This idea was quickly disregarded because the scale needed and the relatively small work area we would be working in made us doubt that any projector has an area of vision that big. Even if it did, both me and andy agreed that there would likely distortions in the pattern as we got to the end of the image so a projector was out of the picture. The only thing we could think of that would let us duplicate a shape big enough was to use some kind of a template. This idea also had problems because of the sheer size we are talking about. In case you don’t remember from some of my previous posts on the solar balloon, our solar balloon is designed to be 10 feet across and so, if we do the math, we need a template about 5 feet wide and 15 feet long. Funny thing, you cant go down to a craft store and pick up a 15-foot long template for a sphere, that kind of thing is just not made anywhere we could find. because of this, we were forced to make our own. our first idea was to get an image from the internet and then printing it ours on a mega scale printer located in the printer of the library where we both go to school. Turns out trying to print a piece of paper this big would cost us over 100 dollars, which is obviously out of the question for a build that is supposed to be a very cheap project. Finally, we got the idea (from my Mom) to use a painters drop cloth. a quick trip to LOWES found us with a piece of plastic measuring about 10 feet wide and 20 feet long, just the right size for our template.
The next challenge was to put the pattern on our template. We couldn’t use a projector, for reasons mentioned earlier, so we decided to the math and draw the shape ourselves. Because we decided to make our balloon out of pieces of this template, all we needed to do was a little math and in no time we had ourselves a template. we folded the plastic in quarters just to expedite the cutting process and made sure to include a hole in the bottom so we could fill it up with air before take off.
With the template ready to go, we started an assembly line with Andy making giant sheets of plastic by fusing about 8 disassembled trash bags into one giant sheet which I then used the template to cut the sheets into balloon parts. In case you were wondering why there is a hole in the nose of our template, that was an accident where we accidentally melted our sheet of plastic to the template and was forced to cut that part away from the template and plastic sheet in order to separate the too. As an upside, the template now looks like a rocket ship!
After we completed six of these balloon parts, the next step was to fuse them into a sphere. To tackle this, me and Andy set up a system to make creating a 3D object on a 2D floor easier. we started joining each section by first joining the middle and then moving to the nose (where the hole is in the template) with Andy fusing while I was putting each piece in place so they would be ready for fusing. once we reached the nose, we then repeated the process moving about 1/2 to 2/3 of the way down the tail. We didn’t completely finish it for reasons that will soon become clear. with one side of the plastic balloon part fused, we repeated that process five more times until finally, we were at the final seam. Because this seam was the one that closed the balloon making into a sphere, we needed a different plan of attack for how to finish this. What we finally decided on was Andy was going to crawl into the balloon and I was going to drag the cloth over his back so he could position it for fusing. I was also in charge of making sure he had enough air to breath as neither of us thought to bring a fan for ventilation.
This image is a picture of Andy inside the balloon and hopefully, this shines some light on just how big this thing was. With this final seam, we started at the nose and worked our way back until we got to the tail and this is where leaving the remainder of the tail’s unfused was a good idea because it created a hole big enough for andy to work in. Once andy was out of the balloon, the only thing left to do was fuse the tails and give it a test.
In case you still haven’t gotten the scale of this balloon, your tallest friend could, if we made a hole for him, crawl inside this balloon and stand straight with feet of clearance between their head and the top of the balloon. Also, if you were wondering why were wearing hearing protection, my boss was amazing and let us use one of the backpack leaf blowers that we use for work and it is was so powerful that it filled the balloon in just minutes while still running on idle. There was hardly any sun that day so we didn’t really expect to get it flying but we still wanted to see it inflated and get some information about how hot it was inside the balloon even with almost no sun. when we inflated it, we found that our method of fusing had malted dozens or hundreds of holes in the ballon of various sizes that all needed to be taped together so it would be mostly airtight. also, we tested the temperature difference between the outside air and the inside air and came to about 5 degrees of temperature. This was worrying because our math had said that a balloon this size should be lifting almost 1 kilogram with only 2 degrees of temperature difference but in hindsight, the fact that the balloon was not flying yet was not entirely surprising because of 2 reasons.
- the balloon was probably slightly smaller than we intended it just due to manufacturing imperfections that were unavoidable
- The balloon was not full of air like the math required, it was probably only 80% full at the time we measured the temperature so the total lift would have been reduced because of that
Though this result surely surprised and worried us, we soon found that this was not going to be a problem in the slightest. If you remember, one of the purposes of this balloon was to decern an approximant temperature difference we will be getting in our balloons so we have a base for our future calculations. Because of this, we over-engineered this balloon so that it should work in almost any condition, and indeed we will see in the next Solar Balloon post that our earlier concerns were unfounded.
I hope that you have enjoyed this post. If you are attempting to build one of these Balloons yourself than plan for this build to take you multiple hours to complete, it took us approximately 10+ hours split over two days, so plan for either more people or similar build times when you do yours. Either way, I hope this post was helpful for you and until next time, 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!