- #31
jetwaterluffy
- 227
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NascentOxygen said:Sure. That would work, provided you keep it hot enough.
You're talking about a hot air balloon, aren't you?
Can a vacuum balloon float like a helium balloon?
Click For Summary
Discussion Overview
The discussion revolves around the feasibility of a vacuum balloon floating in air, similar to a helium balloon. Participants explore the theoretical and practical challenges of creating a vacuum chamber that could achieve buoyancy, considering material limitations and structural integrity.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- Some participants suggest that a vacuum balloon could float if constructed from a sufficiently strong and lightweight material, while others argue that no such material currently exists.
- It is noted that the density of the balloon must be less than that of air for it to float, similar to how helium balloons operate.
- One participant emphasizes that the challenge lies not only in material strength but also in the size of the balloon, as thinner materials struggle to maintain a vacuum.
- There are discussions about using a rigid framework covered by a thin foil, with some proposing innovative geometries to optimize the structure.
- Concerns are raised about the practicality of manufacturing such structures, with references to the need for pinhole-free surfaces to maintain vacuum.
- Some participants mention that while theoretical designs may exist, actual calculations and practical implementations are necessary to validate these concepts.
Areas of Agreement / Disagreement
Participants generally agree that a vacuum balloon could theoretically float if the right materials and designs were available. However, there is significant disagreement regarding the feasibility of current materials and the practicality of constructing such a balloon.
Contextual Notes
Limitations include unresolved questions about material properties, the effects of size on structural integrity, and the challenges of maintaining a vacuum in thin foils. The discussion reflects a blend of theoretical exploration and practical concerns without reaching a consensus on a viable solution.
Who May Find This Useful
This discussion may be of interest to those studying materials science, engineering, or physics, particularly in the context of buoyancy and structural design challenges.
You're talking about a hot air balloon, aren't you?
- #32
akhmeteli
- 816
- 41
bbbeard said:
In this case I use the classical Zoelly formula for thin spherical shell buckling (see my patent application or http://books.google.com/books?id=6P...age&q=zoelly spherical shell buckling&f=false , equation 5.2 .
bbbeard said:
Because even if you substitute the kevlar compression modulus for the stiffest direction (say, 76 GPa; you can even substitute the value of the kevlar fiber tensile modulus - about 180 GPa) in the Zoelly formula, the critical pressure will be much less than the atmospheric pressure for radius of curvature R=6 m and the shell thickness h=0.9 mm.
- #33
NascentOxygen
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Yes, chrisbaird has his figures wrong way round.bbbeard said:
air at STP 1.293g/L
N2 at STP 1.2506g/L
He at STP 0.1785g/L
- #34
DaveC426913
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NascentOxygen said:
So, a one litre balloon of N would have to have materials weighing less than ... 42g.
- #35
chrisbaird
- 610
- 5
NascentOxygen said:
Oops. That's why I'm a theorist. I just lifted these numbers (not so carefully) from wikipedia. The point is that it's all about densities and as air is mostly nitrogen, it it not much different from pure nitrogen as compared to Helium.
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