Talk:Gas balloon
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--==Charlier?== Named for its inventor? So who would that be? Charlie Brown? (Given his experience with kites, I'd guess not...) It's Jacques Andres Charles, first flight 1783. Nice of you to mention it. Trekphiler 22:03, 2 December 2005 (UTC)
Queries posted 1255 PST by carmicheal99; please add comments in new color.
French history... oh what it would have been like to be there that day.
Query: Using current superpressure sealing techniques what will be the next generation of near-space balloons be like?
Given the mindset of communications and reconnaissance experts around the world near-space and high altitude platforms will find a niche in military and commercial applications. High Altitude Balloons (HAB) provide a cost effective and survivable alternative to space borne satellite networks. A small fleet of HAB's as envisioned by the Air Force could be deployed quickly and provide real-time command and control for limited resources in emergency or contingency situations thus eliminating the need for stategic assets for local events.
Currently superpressure helium balloons enjoy an altitude previously unimaginable to the pioneers of space flight but we can go higher and longer than ever before using existing technologies. Lets review boyancy physics for a moment; objects float because they have a lower mass to volume (density) than the media they inhabit. Helium floats in air because it is less dense than the air, simple enough. What is less dense than helium? Automatically hydrogen comes to mind but past experience has shown the dangererous outcomes to be unmanageable. We forget that there are states lighter and far safer than hydrogen, for example a vacuum.
Imagine a superpressure balloon fully inflated that has another superpressure ballon within the first. These two ballons are separated but attached then the gas within the inner balloon is pumped out to form a vacuum pocket stablized by the two ballons. Essentially a spherical superpressure shell is formed around a vacuum. Lets review boyancy physics again; helium > hydrogen > vacuum, and helium < atmospheric pressure = positive boyancy. Net boyant forces would be greater in a vacuum balloon than current designs allowing for longer loiter times and greater altitude from the earth's surface.
- superpressure balloons do not achieve higher altitude than normal ambient pressure balloons. The only reason for superpressure is to stabilize float altitude (perhaps lengthening total flight time) -- a high altitude balloon with vents ("zero-pressure balloon") will lose gas during the day when sunlight heats up the envelope, causing it to shrink and dip lower at night when the envelope cools and the buoyant volume decreases. Superpressure balloons maintain (close to) the same volume throughout the day/night cycle.
- A vacuum pocket would have to be supported by some sort of structure, or else the outer envelope (under compression, not tension) would collapse. It's not worth the extra effort to hold it apart. Helium floats in air because its molecular mass (4) is less than the molecular mass of air (around 29). Hydrogen is even better (2), but represents only a marginal gain: (29 - 4) is 25, and (29 - 2) is only 27, about an 8% improvement in lift. Vacuum would only be another 7% improvement over that. zowie 21:06, 10 July 2006 (UTC)
- 7% improvement is a very liberal estimate but if that boyancy is converted into altitude then this marginal increase in lift is easily closer to the space barrier. It may even be close enough to start using alternate means of lift such as ionization or magnetic draw. Carmicheal 19:05, 03 August 2006 (PST)
Query: What is the lower limit of boyancy based upon the cumulative effects of additional construction material and lowered density?
- It is not clear what you are asking, but nobody has ever built a vacuum chamber that is lighter than the air it displaces. zowie 21:06, 10 July 2006 (UTC)
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- Is that because the right question about its construction has never been asked?
Perhaps thinking of the above "superpressure shell" could be likened to the skin of an orange, even after peeling the rind from the fruit it retains its spherical shape and can be reassembled. This is because the inner shell (white, hairy part of the rind) exerts less pressure on the outer shell (orange part) but they are bound together so a curve forms. Another way to think about would be a bi-metalic when it is deformed due to thermal differences or a white water raft that is inflated unevenly. Take this shape and form it into a self-supportive geometric configuration and voila, an orange without the pulp and juice. How large does the orange need to be to float if a vacuum is created within it?
Here is the pressure diagram, correct me if it is unrealistic:
Pressure: Distance from center ---->
0 0 0 0 0 0 0 0 ( 1 ) 1 1 1 1 1 1 1 1 1 1 1 ( 1 ) 0 1 0 0 0 1 1 0 1 1 0
0 0 0 0 0 0 0 0 ( 1 )-----------------------( 1 ) 1 0 1 1 0 1 1 1 0 1 1
0 0 0 0 0 0 0 0 ( Valve/pump mechanism ) 1 0 1 0 1 1 0 0 1 1 1
0 0 0 0 0 0 0 0 ( 1 )---------------------- ( 1 ) 1 0 1 0 0 1 1 0 0 0 1
0 0 0 0 0 0 0 0 ( 1 ) 1 1 1 1 1 1 1 1 1 1 1 ( 1 ) 0 1 0 1 0 1 1 0 1 1 0
Vacuum Inner --Links-- Outer Near
Barrier Barrier Space
Make this diagram three dimensional in your mind and form a shell with only one pumping mechanism. carmicheal 19:53 03 August 2006
Query: What are the commercial and military applications of a superpressure shell balloon?
- the NSF ULDB ballooning page zowie 21:06, 10 July 2006 (UTC)
