The balloon will never escape the atmosphere. It simply drifts higher until it either reaches neutral buoyancy, or pops. As the balloon rises, air pressure decreases. The result is that the gas inside the balloon is compressed less as the balloon rises, causing the balloon to expand.
In a flight like jgc's, the latex balloon expands until it pops. There are other balloons which can float at a steady altitude. One of these is called a "Zero-pressure Balloon." This balloon operates with a valve on the bottom. The helium will expand until it reaches this valve, then spill out. When the balloon loses helium, it loses lift. The valve will tend to dump helium until the balloon reaches neutral buoyancy. These balloons are so named because the pressure at the valve is the same as the ambient atmospheric pressure.
Another type of balloon is called a "Superpressure Balloon." These balloons maintain altitude by pressurizing internally. Unlike latex, these balloons stop stretching at a certain altitude. As soon as the balloon stops expanding, it maintains a constant volume. Buoyancy is based on the volume of fluid displace, so a pressurized balloon maintains the same altitude.
I work with a group of hackers attempting to cross the Atlantic Ocean using a Zero-pressure balloon. (http://www.whitestarballoon.com). A group of radio amateurs actually beat us to the punch (http://www.arrl.org/news/amateur-radio-balloon-flight-crosse...), their crossing was involved a large quantity of luck. We seek to develop systems and methods for engineering balloons capable of traversing large distances safely and reliably.
Very interesting, but why won't it ever leave the atmosphere or at least rise far enough that it could reach the Kármán Line (~100km). The record according to jgc is ~40km. Why is it so difficult to go from 40km to 100km if these zero-pressure valves exist?
(PS: I am aware the Kármán line actually has to do with aerodynamic lift (and therefore may not really be applicable to lighter than aircraft). It just chose it because it's the commonly accepted "edge of space")
In order to go higher, you must enclose a larger volume of lifting gas. Eventually, the weight of your envelope will exceed the amount of lift you're able to generate with the enclosed volume.
The Japanese currently hold the world altitude record (among all professional and amateur balloons), IIRC. Their balloon was 3.4 micrometers thick, 60,000 m^3 of helium. They reached 53 km.
People do use hydrogen, but most balloons still use helium because it does provide a slight safety advantage when launching. (It's also sometimes an insurance requirement.)
I expect to see an increase in the number of hydrogen-filled balloons as helium prices rise in the next few years.
> balloons capable of traversing large distances safely and reliably.
How would you do that? Once it is in the air isn't it at the mercy of the air currents (can you control the altitude?). Then is it a matter of analyzing and predicting the flow of air currents and the weather?
Japanese for example attempted to send balloons over the pacific that were intended to drop on US and start forest fires.
Prediction tools are a big part of it. The US government publishes global wind data every 6 hours, as well as tools that can be used to parse and process this data. We've done a bunch of scripting on top of that to automatically email, sms, and tweet launch opportunities. The team doing the predictions is too busy/lazy to upload their code to our github account(https://github.com/whitestarballoon/), and that's the only reason it isn't open source.
We can drop ballast to maintain altitude, but we don't have any other control. As a result, we must wait for the winds.
The Japanese balloons were examples of exquisite analog engineering. The Army made a great video documenting their construction and operation (available here: http://www.archive.org/details/gov.archives.arc.13084).
In a flight like jgc's, the latex balloon expands until it pops. There are other balloons which can float at a steady altitude. One of these is called a "Zero-pressure Balloon." This balloon operates with a valve on the bottom. The helium will expand until it reaches this valve, then spill out. When the balloon loses helium, it loses lift. The valve will tend to dump helium until the balloon reaches neutral buoyancy. These balloons are so named because the pressure at the valve is the same as the ambient atmospheric pressure.
Another type of balloon is called a "Superpressure Balloon." These balloons maintain altitude by pressurizing internally. Unlike latex, these balloons stop stretching at a certain altitude. As soon as the balloon stops expanding, it maintains a constant volume. Buoyancy is based on the volume of fluid displace, so a pressurized balloon maintains the same altitude.
I work with a group of hackers attempting to cross the Atlantic Ocean using a Zero-pressure balloon. (http://www.whitestarballoon.com). A group of radio amateurs actually beat us to the punch (http://www.arrl.org/news/amateur-radio-balloon-flight-crosse...), their crossing was involved a large quantity of luck. We seek to develop systems and methods for engineering balloons capable of traversing large distances safely and reliably.