Intro to Weather Balloons
Weather balloons are a type of high altitude balloon specifically used for transporting scientific payloads into our upper atmosphere. They can carry their payloads as high as 40,000 m ~ 130,000 ft. Every day approximately 800 meteorological weather balloons are released at 00:00 and again at 12:00 GMT at locations around the world. This provides a “snapshot” of our earth’s upper atmosphere twice a day. The few launches done by amateurs every day are just a drop in the bucket compared to the 1,600 or so launches done by meteorological organizations around the world.
History - One of the earliest documented uses of weather balloons was by French meteorologist Leon Teisserenc de Bort. He was actively launching weather balloons as early as 1896. His work was instrumental in the discovery of the tropopause and stratosphere. These are unique layers in our atmosphere which you can discover for yourself with our Eagle Flight Computer. Because Leon Teisserenc de Bort's work was so instrumental, he was honored by having both a crater on the Moon and a crater on Mars named after him. In the early 1900s, a meteorologist and geophysicist by the name of Alfred Wegener used weather balloons (image right courtesy of publish.illinois.edu) to perform experiments which led him to discover his Continental Drift Theory. He published his theory in 1912. He's theory was met with a lot of resistance and wasn't accepted until the 1960s, more than 30 years after his death. He has also been honored by having both a crater on the Moon and a crater on Mars named after him. James Van Allen, who would later discover our Earth’s Van Allen Belts, also performed many important weather balloon experiments in the 1950’s. Time magazine honored him as Man of the Year in 1960. Imagine what you could discover by launching your own mission to the edge of space!
Manufacturing Process - Weather balloons are typically manufactured from latex. Latex is a natural substance found in many plants. Plants use latex as a defense against herbivorous insects. This milk like liquid can be extracted from trees much like maple syrup is extracted from maple trees. Once the latex is naturally extracted, it is spun in a mold in the shape of the balloon and cured. Each balloon is then inflated and inspected for leaks and defects before being shipped out to distributors and customers.
Different Sizes - Weather balloons are listed by weight in grams and not by physical size. A 350 g weather balloon weighs 350 g, a 1200 g weather balloon weighs 1200 g etc. Weather balloons typically all share the same thickness latex skin, regardless of their "size". The difference in weight between different size balloons comes from the size of the mold the balloon was manufactured on. A larger mold required more latex and therefore the final cured balloon will weigh more. It also means the balloon will stretch to a larger diameter before bursting. In the image to the left, Joseph is holding our 1500 g weather balloon. It was cured on a mold almost 2 meters in diameter. If you have never launched a weather balloon before, we recommend starting with a 350 or 600 g weather balloon. They are a lot more forgiving to work with on the ground and are still capable of taking our Eagle Pro Kit to an altitude of 90,000 ft or more. Larger weather balloons such as our 1200 or 1500 g balloons are much more challenging to work with on the ground because they have a much larger uninflated diameter. A larger balloon also requires a lot more helium just to compensate for its own weight which will significantly increase the cost of your launch.
How Weather Balloons Work - A weather balloon filled with helium will fly for the same reason oil floats on water. Oil has less density than water. As an experiment, pour a tablespoon of cooking oil into a glass of water. You should see the oil rise to the surface of the water. Just as the oil has less density than water and rises to the surface of the water, helium has less density than air and will rise to the surface of the earth's atmosphere. This is a good thing for us because the surface of our atmosphere is where space begins and where we want to fly our payload. By trapping the helium inside a balloon, we can attach a line to the balloon, called the flight train, with our payload suspended at the other end. The balloon will then lift our payload to the edge of space. However, as the balloon climbs higher, the pressure in the atmosphere decreases. The reduced pressure causes the balloon to expand. Weather balloons are specially designed to be able to expand to a very large diameter. Joseph is demonstrating this with a leaf blower we hooked up to the same balloon he was holding in the previous image. A weather balloon that starts out at 2 m in diameter at launch can expand to a diameter of up to 10 m. As the balloon climbs to the edge of space it eventually expands to the point where it bursts. Our payload then falls back to earth under a parachute. As long as we can track our payload, we can recover it along with its recorded scientific data and flight video.
Lifting Gas - Helium isn't the only gas that has less density than air. Hydrogen is another common lighter-than-air gas used by many meteorological organizations. Hydrogen is easy to manufacture and is therefore cheaper than helium, but it is far more dangerous to work with. Helium is a byproduct of the radioactive decay of uranium and there are no practical known ways of manufacturing helium… short of creating your own miniature sun. Luckily for us, our earth has large reserves of helium in the North American natural gas fields. We would never recommend that any of our customers ever use hydrogen as their lifting gas. It is an extremely dangerous gas to work with without proper training. It is not worth placing yourself and others in danger just to save $100 on your launch. Ferdinand Van Zeppelin never designed the Hindenburg to be flown with hydrogen as its lifting gas. It was only after he went before the US Congress and they refused the export of helium to Germany that he used hydrogen. If Congress had allowed the export of helium to Germany, airships would probably be far more common today. Investors shied away from Zeppelin's technology after the Hindenburg disaster (image right courtesy of museumsyndicate.com). The Empire State Building in New York stands as a reminder of a time when lighter-than-air ships were more common. The spire of the Empire State Building was originally designed as a mooring mast for dirigibles.