Helium Balloon Question

[halofuji]

At what altitude will a trash bag filled with helium and tied at the bottom to stop leaking explode and fall back to earth? Can someone give me a rough estimate?

 

Also, would it rise further up when the temperature is cold or when the temperature is hot?

 

Thank you.

[swansont]

We would need to know the strength of the bag. You can figure out the pressure difference between inside and outside from the ideal gas law, PV = nRT and knowing how much of an effect the bag has. The external atmospheric pressure and surface pressure of the bag/balloon will be equal to the Helium pressure. It will break when the required surface pressure exceeds the tensile strength of the container.

 

In equilibrium

P_i = P_surf + P_atm

 

If you want it to break, the tensile strength has to be smaller than the internal pressure as P_atm goes to zero. If it's bigger, you have a space-worthy container. To find the altitude you need atmospheric pressure as a function of altitude.

[halofuji]

We would need to know the strength of the bag. You can figure out the pressure difference between inside and outside from the ideal gas law, PV = nRT and knowing how much of an effect the bag has. The external atmospheric pressure and surface pressure of the bag/balloon will be equal to the Helium pressure. It will break when the required surface pressure exceeds the tensile strength of the container.

 

In equilibrium

P_i = P_surf + P_atm

 

If you want it to break, the tensile strength has to be smaller than the internal pressure as P_atm goes to zero. If it's bigger, you have a space-worthy container. To find the altitude you need atmospheric pressure as a function of altitude.

 

Never mind.

 

My next question in order to go up to the maximum potential, do you suggest the size of the balloon to be very big or large? What size would you say the ideal size that can achieve maximum height? Does it go up quicker if there is a more mass?

 

Also I did not quite I understand you on your explanation about what type of temperature is good to reach the maximum height.

Edited July 19, 2011 by halofuji

[math-helper]

Hot temperature means hot air which is lighter as compared to cold one, so at high temp. it will not get the same height as for the cold one.

Never mind.

 

My next question in order to go up to the maximum potential, do you suggest the size of the balloon to be very big or large? What size would you say the ideal size that can achieve maximum height? Does it go up quicker if there is a more mass?

 

Also I did not quite I understand you on your explanation about what type of temperature is good to reach the maximum height.

[halofuji]

Hot temperature means hot air which is lighter as compared to cold one, so at high temp. it will not get the same height as for the cold one.

 

So its good to send it up when the outside temperature is hot?

[CaptainPanic]

The relative difference between the gas and the air is what matters. This relative difference will be larger at colder temperatures. However, the effect is quite small (unless you are comparing the difference between Siberia in mid-winter to the Sahara in summer).