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What Happens to a Balloon That Keeps Rising into the Upper Atmosphere?
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If a balloon were made from an extremely strong material and filled with enough lifting gas to continue rising, would it keep ascending indefinitely? What would happen to it as it reaches the upper layers of the atmosphere?
fluid-dynamics
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edited 15 hours ago
Robert DiGiovanni
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If it did not burst and could expand indefinitely, it would keep rising, because the volume of air it replaces is heavier by the same amount of mass.
This is why balloons can rise to incredible heights.
The relationship to pressure, volume and mass is described in the equation:
${Pressure × Volume = nR (mass) × Temperature}$
As pressure goes down (as altitude increases), volume increases.
In reality, the weight of the balloon itself limits the volume it can expand to and, at maximum altitude, it must vent gas when it has expanded to its maximum size.
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answered 15 hours ago
Robert DiGiovanni
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$\begingroup$<br>The record is actually significantly higher than Baumgartner's YouTube stunt: 53.7km.<br>$\endgroup$
Jörg W Mittag
Jörg W Mittag
2026-06-09 19:38:07 +00:00
Commented<br>13 hours ago
$\begingroup$<br>But eventually there's no atmosphere anymore. At that point, the balloon isn't displacing anything at all - as the buoyant force approaches zero, it can't support the weight of the balloon. The balloon would have to be not only infinitely strong, but also massless to rise indefinitely. You can't float a balloon up to the moon no matter how strong it is.<br>$\endgroup$
Nuclear Hoagie
Nuclear Hoagie
2026-06-09 19:54:21 +00:00
Commented<br>13 hours ago
$\begingroup$<br>Fun fact: satellites still experience atmospheric drag, but yes, the limiting factor is volume and weight of balloon.<br>$\endgroup$
Robert DiGiovanni
Robert DiGiovanni
2026-06-09 23:39:08 +00:00
Commented<br>9 hours ago
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No, a balloon can't ascend indefinitely. You can't make a balloon fly into space because that isn't how buoyancy works.
Buoyancy is an upward force caused by gravity pulling down on the surrounding fluid -- if a container displaces a greater weight of fluid than the weight of the container itself (and its contents), then it floats. In the case of a balloon, you're looking at the weight of the balloon's envelope and payload (call that the 'dry weight'), plus the weight of the lifting gas contained inside the balloon, and comparing that total to the weight of an equal volume of outside air. If the displaced volume weighs more, then the balloon rises with a lifting force equal to that difference.
A reduction in exterior pressure reduces the lifting force by making the equivalent displaced weight per volume lower, but it also increases the lift because the lower external pressure allows the balloon to expand, which increases the displaced volume. Ideally, the interior pressure and exterior pressure are always equal (that is, the physical structure of the balloon puts no compressive force on the lifting gas), so that theoretical balloon would ascend until it reaches an altitude where the difference between the lifting gas mass and the displaced air mass is exactly equal to the balloon's dry weight, and it would bob along at that altitude, perturbed by atmospheric movement around it. It can't go any higher because if it does, the balloon is heavier than the air it displaces, and it sinks until it reaches that equilibrium point again.
Reality is of course more complicated, since you can't have an infinitely stretchy gas bag, and even when not fully inflated, the balloon does put some compressive force on the gas inside it, so that limits the altitude you can reach. And thermal expansion of gas inside the balloon has an effect which we're ignoring.
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edited 5 hours ago
answered 14 hours ago
Darth Pseudonym
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