Embedded Files
OLD TECHNOLOGY -- Nearly all of the videos on YouTube describe using SBS balloons or Clear Chinese Balloons. Both of these are no longer used. The SBS balloons are very expensive and do not provide any advantages over the newer spherical balloons. Clear Chinese Balloons were made of two circles of plastic sealed at the edge. They inflated to a pancake shape and did not hold much gas. The correct balloons inflate to a sphere. It was unusual to get pancake balloon to go around the world. The current best balloon are listed below.
Stretching and Filling Pico Balloons
Stretching and Filling Pico Balloons
The video on the left shows the process of stretching and filling a balloon. Note that stretching can be done well in advance of launch. However, filling should be done the night before or the day of the launch. At normal temperatures, some gas will diffuse out through the skin of the balloon. The balloon will lose about 0.5 gm of lift overnight. This diffusion decreases to a very small level when the balloon is at altitude where the temperature is very cold.
Leak Testing
Leak Testing
The quality control on balloons is not perfect. Consequently after stretching it is recommended that the balloon is tested after stretching. The following paragraph describes the process developed by Bill Brown WB8ELK.
"One good test for leakage is when you get it up to 0.500 PSI....let it vent down to about 0.300 PSI and remove the fill tube enough so that the internal flat valve stops any air from leaking out...your manometer will read close to 0.000 PSI at that point. Let it sit for 30 minutes to an hour and then push the fill tube back inside the balloon until you see a reading on the manometer...It should still be close to 0.300 PSI...if it is much less than that, then the balloon has a leak somewhere. Another quick test is to take two pieces of rubber foam (the kind used for insulating around doors). Press two pieces on either side of the filling port entry hole and see if the pressure stops going down for a minute or two. If it stays the same after a minute then the balloon is good but I also usually do the one hour flat valve test to make sure."
- Bill WB8ELK
How high will my pico balloon go?
How high will my pico balloon go?
Given the total weight of your balloon system (antenna, tracker, balloon, panel) you can calculate the final pressure in your balloon and how high it will float. There is a Excel spreadsheet (Float1b.xls and float1g.xls on the pico balloon groups.io website that performs this calculation. Many light balloons, fly at 13000 m or more. Winds at that level are slower than lower altitudes. If you want to fly at a lower altitude, try not stretching the balloon to the maximum of 100 in. However, it is recommended to stay above 12000 m which is above comercial aircraft flights.
Typically balloons fly with about 8 grams of free lift. Free lift is the amount of lift over and above the wight of the balloon system as explained in the video. There is a tradeoff between having extra gas that will allow the balloon to float longer and risk of over pressure causing the balloon to burst. Typically free lift is around 7-8 gm. The balloons listed below are relatively new so the limits are not well known but they have been proven to work well. Here are calculators for and links for documentation on lift and burst pressure.
Where can I buy the special balloons?
Where can I buy the special balloons?
Balloon Types
Balloon Types
There are two different types of balloons that are used. Both balloons are the same size and are stretched the same way. One type is made of clear plastic and the other is made of silvered mylar. Both have been used successfully. The clear balloons are several grams lighter and will fly higher then the silvered balloons.
Filling Port Types
Filling Port Types
There is also a variation in the type of filling port that these balloons have. Most have a light weight plastic sleeve that extends the filling port into the balloon for a few inches. When the filling tube is pulled out the plastic sleeve colapses from the pressure within the balloon. This provides a valve that that hold in the gas. However, additional sealing is needed as shown in the stretching video.
The other type of filling port is found on the Yokohama balloons. This is a simple extension of clear plastic out of the side of the balloon. This needs to be heat sealed after filling using an impulse heat sealer.
Balloon Size
Balloon Size
There are two sizes of balloons that are used for Pico Balloons: 50 inch and 60 inch. The 50 inch is stretched to 100 to 104 inch circumference. The 60 inch stretches to 120 inches in diameter. Both with fly higher then 40,000 feet. The 60 inch will fly higher for the same payload and free lift.
Clear Plastic Balloons
Clear Plastic Balloons
There are two sources for clear balloons.
Yokohama balloons are only sold in quantities of 10. The current cost with shipping is $250. This is the balloon that is most commonly used because it is clear. Clear balloons do not get as warm as colored when irradiated by the sun. Click on the balloon to go to the Yokohama site.
A balloon similar to the Yokohama balloon is sold by Balloons Online. It is clear and has a valve. This is light and easy to use, but hard to get. They are commonly out of stock.
Silver Balloons
Silver Balloons
Balloons Online also sell silver mylar balloons with a valve. They sell single balloons with shipping for $24. Other colors may work but I do not know of anyone that has tried. I have had a silver balloon go around the world almost 7 times.
There is also another source for this type of balloon through Amazon. They are by PartyWoo and are very inexpensive. LINK These also have a valve and do not need heat sealing.
A shiny or white surface reflects the Sun's energy, but some of it gets absorbed. The funny thing about shiny or white surfaces is that once energy is absorbed, it is difficult to radiate away. Dark balloons are cooler than white balloons at high altitudes. At low atmospheric pressure the balloon is cooled by radiation instead of convection. Colored surfaces radiate better than silver and remain cooler. See the 1967 document for details.
I have flown silver balloons and they have lasted months. This is not a critical problem. The silver surface is inside the plastic balloon. In the infrared, the plastic is less transparent, but will efficiently radiate away heat energy. If someone has an infrared camera and some balloons of different colors, this would be an interesting experiment.
Large Balloon
There is currently only one 60 inch balloon on the market that has been used successfully. LINK
Page updated
Google Sites
Report abuse