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High Altitude Balloon: Could you steadily release helium as you gain altitude to prevent bursting?

I have recently been researching privately made High Altitude Balloons. Making something that can travel a third of the way to space while taking pictures and/or measurements sounds like a very cool project. Typically these balloons pop before reaching anywhere near space. While researching I had a small "Eureka!" moment for a potential fix for this issue. It might be possible to take these balloons farther up if you slowly release helium in correlation with altitude. Perhaps by measuring the size of the balloon as it expands upwards and out, and then releasing helium with an electronic valve until it returns to proper size. 
I have the nagging feeling however I am not considering everything though. Is there some principle of 'The way things be' that prevents this method from working correctly?
Would the lift of helium increase with distance from the earth significantly enough not to drag the craft down when you release helium? Or would the helium loose its effectiveness the thinner the atmosphere became?
Any help I can receive in being unflummoxed is greatly appreciated.

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takeymctaker6 months ago

Look at what Google's Project Loon is doing. They have a small fan and electronic release valves that fill a loosely nested balloon with more or less atmosphere air as ballast, which causes it to shift between different altitudes. They then use the different wind directions on each adjacent altitude to "fly" the balloon around roughly where they want it. Combined with more resilient materials selection and fabrication, they have kept high altitude balloon drones flying over target service areas for more than a hundred days each. One problem is if you lose control of a balloon for any reason (such as night time air pressure and lift loss) and it drifts into civil airspace, you have to be able to cause it to come back down (out of civil airspace) immediately.

I personally wonder if a Tesla Valve could be fashioned into a sort of solid-state passive pressure differential relief valve, where air can only push outward after a minimum pressure differential has been reached, which is set by design to start before bursting pressure. This could be placed at the nozzle of *any* balloon type to prevent violent bursting, but it would need other means to prevent more gradual deflation (maybe a small tank payload of condensed helium for mid-flight refills). I also wonder if this could provide more balloon re-use to reduce total flight costs.

JimZ711 months ago

Why not use a mylar balloon and pre test pressure maximum.Then use a pressure relief valve @ the maximum balloon pressure rating so it vents rather than exceeding pressure rating of your balloon.You would still need to use a proper free lift as to prevent the balloon from reaching an altitude where it will release too much.The valve will only open if you exceed maximum balloon pressure rather than burst.

Here is a great source for custom pressure valves.

http://www.smartproducts.com/check_valves_series_100_cartridge.php

rickharris2 years ago

Quite a lot of the very large high altitude balloons are actually open at the bottom for this very reason. They take the form of a long plastic bag so that the helium rises to the top and the weight of the load keeps the bottom below the helium.

As in the illustration.

balloon_launch.jpg
JM19992 years ago

Just use a pressure relief valve like those on the gas cylinders, set it to the correct pressure and there you have it!

JM19992 years ago

Just use a pressure relief valve like those on the gas cylinders, set it to the correct pressure and there you have it!

kelseymh2 years ago

You're doing a good job of thinking this through. Mpilchfamily has part of the answer -- balloons which are overfilled initially (to get lift off the ground) don't have any margin to expands as the outside pressure decreases

Your last question is the right one. You get lift from a balloon for the same reason that a boat floats on a lake: The weight of air displaced by the balloon is higher than the weight of the (inflated) balloon itself: that difference in weight is expressed as lift. As you go up in altitude, the density of the atmosphere decreases, and thus a given volume of air weighs less. If the air volume weighs less, then the lift decreases.

iceng2 years ago

Don't forget it gets below freezing and the balloon material looses flexibility enhancing an easy burst.

They pop before reaching their destination because they are being overfilled at the start to compensate for having the wrong sized balloon for the amount of weight they are trying to lift. If done right the balloon should be filled just enough to start lift and leave plenty of room for the gas to expand. You don't fill them up all the way to start. Look online for an actual weather balloon. You can get an 8' diameter balloon for about $30. If you can get it to lift your gear at about 7' in diameter filled then you will have plenty of expansion in it as it should be able to expand out to about 10' or 12'. But that is assuming your using Hydrogen for better lift.