Bubble habitats are a common part of science fiction, both in space and on servaces of worlds with an absent or toxic atmosphere.

As the last science experiments go up to the ISS, I find myself wishing that I’d pushed for them to try blowing a bubble habitat in the vacuum of space.

The idea is simple enough. Using small source of gas, such as a soda siphon cartridge, inflate a spherical soap bubble in vacuum. Add some low viscosity monomer to the water that polymerises as the water evaporates off. PVA glue for example polymerises by evaporation.

But that made me wonder, if the polymer is permeable to water then it would also be permeable to oxygen and nitrogen, which is not so good.

What plastics can be blown into a huge bubble and are impermeable to air?

Polyethylene (HDPE) is the plastic that gives the smallest thinness for strength, but that requires high temperature and pressure. Not impossible for a space bubble but a bit difficult to blow like a bubble.

Polyester is made by adding a little oxidiser to a low viscosity monomer. Mylar is a type of polyester, and has frequently been used in space, but I’ve never heard of being blown into … yes I have, PET is a type of polyester and it is frequently blown into bubbles.

At the extreme, given sufficient heat and pressure and mass, glass can be blown into quite large bubbles. So perhaps a rigid space habitat made of glass. Laminated of course.

What do you think? What bubbles should have been blown in vacuum by the ISS?

inflate a spherical soap bubble in vacuum

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Have you given this much thought?

Ian said:

inflate a spherical soap bubble in vacuum

—
Have you given this much thought?

LOL

Peak Warming Man said:

Ian said:

inflate a spherical soap bubble in vacuum

—
Have you given this much thought?

LOL

:)

Ian said:

inflate a spherical soap bubble in vacuum

—
Have you given this much thought?

Yes. Much thought but no computation.

Very little gas would be required, only enough for the internal pressure to match the surface tension force.

For example, the gas in a soda siphon capsule would be enough to inflate a soap bubble the size of a house.

The inflation would be rapid, in of order a tenth of a second, fast enough to exceed the evaporation rate and hence also both the polymerisation and cooling. The cooling slows the evaporation rate and hence the polymerisation rate. But that’s not a problem because the polymerisation rate only has to be proportional to evaporation rate so the cooling rate ought to cancel out of the equation.

What’s the problem?

mollwollfumble said:

Ian said:

inflate a spherical soap bubble in vacuum

—
Have you given this much thought?

Yes. Much thought but no computation.

Very little gas would be required, only enough for the internal pressure to match the surface tension force.

For example, the gas in a soda siphon capsule would be enough to inflate a soap bubble the size of a house.

The inflation would be rapid, in of order a tenth of a second, fast enough to exceed the evaporation rate and hence also both the polymerisation and cooling. The cooling slows the evaporation rate and hence the polymerisation rate. But that’s not a problem because the polymerisation rate only has to be proportional to evaporation rate so the cooling rate ought to cancel out of the equation.

What’s the problem?

Blowing a soap bubble in the vacuum of space is like blowing it in still air at 0% relative humidity. Except that there’s no gravity to make the water drain away in space, so it can be more stable when thicker there.

I solemnly swear that I will do the calculations some time. A starting point is “How to make a giant bubble” in Phys. Rev. Fluids 5, 013304

“They concluded that it’s best to use a circular wand with a 1.5-inch perimeter and gently blow at a consistent 6.9cm/s.”

Initial film thickness 1.2 microns. It bursts near a thickness of near 0.3 microns.

The second best they tried was 2.4 g/litre guar gum. The best was 0.5 g/litre for PEO (Polyethylene glycol).

Viscosity in near 0.02 Pa.s for the mixture containing guar gum. Soap and water alone was 0.0012 Pa.s.

What surface tension? Surface tension of water alone is about 70 mN/m. “surface tension decreases with increasing total surfactant concentration” to perhaps half the value. Surface tension of glycerol is about the same as water.

Enough information? I think so.

Consider bubble habitats of diameters 2, 5 and 10 metres, and an initial film thickness of 1.2 microns. That’s a total mass of bubble liquid easily measured in grams. Back of envelope calculation 0.012 g, 0.08 g, and 0.3 g respectively.

But that dries quite thin so it’s better to start with a greater initial film thickness.

We can also get the gas density, pressure and volume of inflating gas from this information.

And get the temperature drop on gas expansion, temperature drop on evaporation, and timescales for both from this information. Which is enough information to get minimum requirements for polymerisation properties.

mollwollfumble said:

mollwollfumble said:

Ian said:

inflate a spherical soap bubble in vacuum

—
Have you given this much thought?

Yes. Much thought but no computation.

Very little gas would be required, only enough for the internal pressure to match the surface tension force.

For example, the gas in a soda siphon capsule would be enough to inflate a soap bubble the size of a house.

The inflation would be rapid, in of order a tenth of a second, fast enough to exceed the evaporation rate and hence also both the polymerisation and cooling. The cooling slows the evaporation rate and hence the polymerisation rate. But that’s not a problem because the polymerisation rate only has to be proportional to evaporation rate so the cooling rate ought to cancel out of the equation.

What’s the problem?

Blowing a soap bubble in the vacuum of space is like blowing it in still air at 0% relative humidity. Except that there’s no gravity to make the water drain away in space, so it can be more stable when thicker there.

I solemnly swear that I will do the calculations some time. A starting point is “How to make a giant bubble” in Phys. Rev. Fluids 5, 013304

“They concluded that it’s best to use a circular wand with a 1.5-inch perimeter and gently blow at a consistent 6.9cm/s.”

Initial film thickness 1.2 microns. It bursts near a thickness of near 0.3 microns.

The second best they tried was 2.4 g/litre guar gum. The best was 0.5 g/litre for PEO (Polyethylene glycol).

Viscosity in near 0.02 Pa.s for the mixture containing guar gum. Soap and water alone was 0.0012 Pa.s.

What surface tension? Surface tension of water alone is about 70 mN/m. “surface tension decreases with increasing total surfactant concentration” to perhaps half the value. Surface tension of glycerol is about the same as water.

Enough information? I think so.

Consider bubble habitats of diameters 2, 5 and 10 metres, and an initial film thickness of 1.2 microns. That’s a total mass of bubble liquid easily measured in grams. Back of envelope calculation 0.012 g, 0.08 g, and 0.3 g respectively.

But that dries quite thin so it’s better to start with a greater initial film thickness.

We can also get the gas density, pressure and volume of inflating gas from this information.

And get the temperature drop on gas expansion, temperature drop on evaporation, and timescales for both from this information. Which is enough information to get minimum requirements for polymerisation properties.

You left out the effects of cosmic rays and gravity ripples.

Tau.Neutrino said:

mollwollfumble said:

mollwollfumble said:

Yes. Much thought but no computation.

Very little gas would be required, only enough for the internal pressure to match the surface tension force.

For example, the gas in a soda siphon capsule would be enough to inflate a soap bubble the size of a house.

The inflation would be rapid, in of order a tenth of a second, fast enough to exceed the evaporation rate and hence also both the polymerisation and cooling. The cooling slows the evaporation rate and hence the polymerisation rate. But that’s not a problem because the polymerisation rate only has to be proportional to evaporation rate so the cooling rate ought to cancel out of the equation.

What’s the problem?

Blowing a soap bubble in the vacuum of space is like blowing it in still air at 0% relative humidity. Except that there’s no gravity to make the water drain away in space, so it can be more stable when thicker there.

I solemnly swear that I will do the calculations some time. A starting point is “How to make a giant bubble” in Phys. Rev. Fluids 5, 013304

“They concluded that it’s best to use a circular wand with a 1.5-inch perimeter and gently blow at a consistent 6.9cm/s.”

Initial film thickness 1.2 microns. It bursts near a thickness of near 0.3 microns.

The second best they tried was 2.4 g/litre guar gum. The best was 0.5 g/litre for PEO (Polyethylene glycol).

Viscosity in near 0.02 Pa.s for the mixture containing guar gum. Soap and water alone was 0.0012 Pa.s.

What surface tension? Surface tension of water alone is about 70 mN/m. “surface tension decreases with increasing total surfactant concentration” to perhaps half the value. Surface tension of glycerol is about the same as water.

Enough information? I think so.

Consider bubble habitats of diameters 2, 5 and 10 metres, and an initial film thickness of 1.2 microns. That’s a total mass of bubble liquid easily measured in grams. Back of envelope calculation 0.012 g, 0.08 g, and 0.3 g respectively.

But that dries quite thin so it’s better to start with a greater initial film thickness.

We can also get the gas density, pressure and volume of inflating gas from this information.

And get the temperature drop on gas expansion, temperature drop on evaporation, and timescales for both from this information. Which is enough information to get minimum requirements for polymerisation properties.

You left out the effects of cosmic rays and gravity ripples.

I’ve posted this as a question on Physics Forum.