Vaccum pockets

  • Thread starter rollcast
  • Start date
  • #1
409
0

Main Question or Discussion Point

Would it be possible for an object with pockets of trapped vacuum space be able to float just the way air pockets do as it is less dense?

Thanks
 

Answers and Replies

  • #2
2,685
22
Yes.

A simple explanation, the ability to float relies on a difference in density. As long as the object with a vacuum internally has a lower density than the surrounding medium, it will float.
 
  • #3
2,193
2
Would it be possible for an object with pockets of trapped vacuum space be able to float just the way air pockets do as it is less dense?

Thanks
Be aware that such a scenario requires material to contain the vacuum.
That material has weight.
I'll leave it to you to go from there.
 
  • #4
409
0
Thanks light bulb moment, the weight of the material need to resist the compressive forces around the vacuum far outweigh any reduced density you achieve from it
 
  • #5
2,193
2
Thanks light bulb moment, the weight of the material need to resist the compressive forces around the vacuum far outweigh any reduced density you achieve from it
Good job!!
 
  • #6
DaveC426913
Gold Member
18,843
2,314
Yep. In theory, with a material that is strong enough you could create a chamber using so little material that it is bouyant. (Or more accurately, its total mass is less than that of the same volume of air.)

Problem is, it would surely be extremely delicate. The slightest bump would likely cause it to deform and implode.

This is why hydrogen makes such a great runner-up. It's the lightest element known that can provide an atmospheric pressure so that the walls don't even need to be rigid. Just that darn combustibility...
 
  • #7
2,193
2
This is why hydrogen makes such a great runner-up. It's the lightest element known that can provide an atmospheric pressure so that the walls don't even need to be rigid. Just that darn combustibility...
And cost. Hydrogen is expensive, and leaks through common membranes.
Heated air seems to produce simlar bouyancy effects with a reduced TOTAL cost???

Just asking... not sure.
 
  • #8
Drakkith
Staff Emeritus
Science Advisor
20,915
4,670
And cost. Hydrogen is expensive, and leaks through common membranes.
Heated air seems to produce simlar bouyancy effects with a reduced TOTAL cost???

Just asking... not sure.
Heated air becomes less dense, causing it to rise in the air. This is how hot air balloons work. You just have to heat it which CAN be less expensive.
 
  • #9
Ryan_m_b
Staff Emeritus
Science Advisor
5,844
711
Helium is the next lightest and has the nice feature of not being so flammable!

Out of interest does anybody know how we could work out the necessary material properties of a vacuum containing balloon?
 
  • #10
409
0
You mean to contain the vacuum or its lift/bouyancy
 
  • #11
SpectraCat
Science Advisor
1,395
1
Helium is the next lightest and has the nice feature of not being so flammable!

Out of interest does anybody know how we could work out the necessary material properties of a vacuum containing balloon?
Well, it must be non-porous, so that there is no gas transport across it. It must have sufficient compressive and shear strength (I think those are the right terms) to withstand the pressure difference of 15 psi (1 atm) pushing from outside to the inside. "Balloon" seems like the wrong word, since balloons have an opposite pressure differential ...
 
  • #12
Ryan_m_b
Staff Emeritus
Science Advisor
5,844
711
Well, it must be non-porous, so that there is no gas transport across it. It must have sufficient compressive and shear strength (I think those are the right terms) to withstand the pressure difference of 15 psi (1 atm) pushing from outside to the inside. "Balloon" seems like the wrong word, since balloons have an opposite pressure differential ...
Good ideas. I was wondering what physical properties our material would need in terms of tensile strength etc. I use the word balloon only in the sense of if it would be possible to make a buoyant vacuum pockets
 
  • #13
DaveC426913
Gold Member
18,843
2,314
Good ideas. I was wondering what physical properties our material would need in terms of tensile strength etc. I use the word balloon only in the sense of if it would be possible to make a buoyant vacuum pockets
You can start by examining how a common egg gets its compressive strength. It is structurally equivalent to a stone archway with no endpoints.
 
  • #14
phinds
Science Advisor
Insights Author
Gold Member
2019 Award
16,223
6,252
Thanks light bulb moment, the weight of the material need to resist the compressive forces around the vacuum far outweigh any reduced density you achieve from it
The standard experiment to show that this is likely to be true with normal materials is to put a little water in a good-sized tin can (say a 2-gallon gas can) with a small top, heat the water until it has all become steam and driven out the air, and then close the can and watch the can implode.
 

Related Threads on Vaccum pockets

  • Last Post
Replies
1
Views
2K
Replies
6
Views
967
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
12
Views
2K
  • Last Post
Replies
24
Views
5K
  • Last Post
Replies
4
Views
7K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
11
Views
3K
  • Last Post
Replies
5
Views
2K
Top