What would happen if an astronaut on a space walk had an empty rubber ballon and filled it with air? Would it just take less air to fill or would it pop with just adding the slightest amount of air?
In: Planetary Science
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There is a right amount of air for that situation, but it is much less than on earth.
When a balloon is filled on earth, the air inside the balloon is equal to the elastic force of the rubber squeezing the air inside, plus the atmospheric pressure, which is 14.7 pounds per square inch at sea level, in freedom units.
This means that at sea level, the pressure inside the balloon is greater than 14.7psi by the amount of pressure provided by the balloon’s elasticity.
The pressure exerted by the balloon’s rubber will increase with the size the balloon. Like an elastic band, it takes more force to stretch it a lot than to stretch it only a little. Eventually the balloon and the elastic will break if stretched too far.
If, at the desired/correct size, the balloon’s rubber exerts 3 psi inward, then the inner pressure would be 14.7+3=17.7psi on earth, but in a vacuum only 3 psi would be required to achieve the same size.
Note: when measuring air pressure, for say bicycle or car tires, we are actually measuring the difference in pressure between outside and inside. A car tire at 30psi contains the same amount of air as 47.7psi when compared with vacuum.
It’d fill up more easily and be a lot easier to pop! (But wouldn’t necessarily pop instantly)
When you fill one up on earth, the air in our atmosphere pushes back against the balloon trying to expand, so you have to put more air inside it to a) fight the atmospheric pushing back and b) surpass the balloon’s limits for stretching/expanding.
In space you wouldn’t have that opposition, so the air pressure inside the balloon would have no atmosphere fighting against it as it tries to expand. Really it’d be a battle of the pressure from air inside the balloon bouncing around vs. the elasticity of the rubber.
It’s not an instant pop because the balloon has some elasticity. Same as the astronaut’s backpack with their air for breathing — it doesn’t instantly explode on the space walk because whatever material it’s made of has some integrity that can stay together despite the pressure of compressed air inside it. The rubber balloon wouldn’t be quite as tough of a material, but still wouldn’t be zero 🙂
Of course, if your and your lungs are exposed to vacuum, you’re gonna lose consciousness within seconds.
Im not sure if we can just say the balloon has to withstand 1 atmospheric pressure more from the inside than would be the case on earth with the same fill of air.
Im sure there are ballons that wont immediately pop. But only a really small amount of air would be enough to expand the ballon.
If you had a balloon that would be fully inflated at 1.5 atmospheres of pressure and pop a 2 on Earth it would be fully inflated at 0.5 atm and pop at 1 in a vacuum.
Some of the decoys on ballistic missiles are pretty much metallic “party balloons” that are the right size to mimic a missile warhead.
“Air pressure” in the earth’s atmosphere is 1 bar absolute.
In space there’s no pressure, so the pressure is 0 bar absolute.
Inflating a balloon in space gives the same result as inflating a balloon on earth with a pressure that’s 1 bar higher.
It’s about pressure difference inside the balloon Vs outside the balloon.
The balloon would behave exactly the same, just at much lower pressure.
Normal atmosphere is about 100 kPa. You can use your lungs to pump the balloon up to 101 kPa, which pushes against the rubber and makes it get bigger. So you have 100 kPa of air outside, balkanced against 101 kPa inside, with the rubber holding back the extra 1kPa. If you keep pushing air into the balloon until it gets to 102 kPa, it will get VERY big, the rubber wont be strong enough, and it will explode.
In space, there is no air, so pressure is 0 kPa. You can use a gas valve to put 1 kPA into the balloon, which makes it get bigger to normal balloon size. The rubber is still holding back 1 kPa. If you try to pump it up to 2kPa, it will explode, as before.
You should do this quickly. If you leave your balloon out in space for too long, the radiation will make the latex brittle. You should also be careful about using room temperature air – air coming from tanks can sometimes be ultracold, and low temperatures are another thing that will make a latex balloon brittle.
The former; it’s been done in real life. NASA launched some in the 1960s (Project Echo) to test passive communication satellites, and there was one launched in 2018 as an art project.
https://en.wikipedia.org/wiki/Project_Echo
[https://www.orbitalreflector.com/](https://www.orbitalreflector.com/)
What would happen if the balloon was filled with helium?
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