What’s the highest a balloon or even a manned airship has ever reached? And, theoretically, is there an absolute maximum range in our atmosphere where nothing can be buoyant beyond that point?
I don’t know if it was the highest, but Felix Baumgartner jumped out of a balloon from a height of 128,000 feet.
Some types of balloons can rise much, much higher than any airship or anything else other than rockets for that matter.
“During 2002 an ultra-thin-film balloon named BU60-1 made of polyethylene film 3.4 µm thick with a volume of 60,000 m³ was launched from Sanriku Balloon Center at Ofunato City, Iwate in Japan at 6:35 on May 23, 2002. The balloon ascended at a speed of 260 m per minute and successfully reached the altitude of 53.0 km (173,900 ft), breaking the previous world record set during 1972.”
I was actually in the control room for that balloon flight, though I didn’t really understand the significance at that time. I was a grad student, and my own experiment was scheduled to be launched from the same facility a few days after. (Mine only went up to 41km since it was a much heavier payload. The record-setting flight was an engineering test flight with hardly any payload.) By the way, 3.4 um is less than 1/3 the thickness of Saran wrap.
For these zero-pressure balloons (i.e. internal pressure is the same as the exterior pressure), the altitude is only limited by how large and lightweight the balloon can be made. Whatever the air pressure, helium at the same pressure is always lighter. But the higher you go, the less lift is generated by a cubic foot of helium. The lower you can make the weight/volume ratio, the higher it goes. If the weight is zero, it just acts as a blob of helium, and it’ll keep rising until it disperses into interplanetary space.
The trick being that “zero pressure” means the envelope needs to be non-elastic. Or equivalently not completely full = where the natural volume of the total weight of helium at the ambient atmospheric pressure is greater than or equal to the volume of the envelope.
I think the SDMB has someone who has done pretty much anything you can think of!
Dennis
Baumgartner held the record for all of two years. There’s this fellow Alan Eustace who did it while eschewing publicity.
As far as pure altitude (forget jumping), Baumgartner broke the record held by Nick Piantanida. Eustace went higher still.
Oh, and Baumgartner didn’t jump “out of a balloon”. He jumped out of a capsule under a balloon. Eustace didn’t even use a capsule, just his suit.
Thanks all for the infomative and interesting replies. The idea that if you reduce the weight:volume ratio enough, something can theoretically achieve escape velocity because it’s so much less dense but strong is interesting, but probably totally impractical?
“Escape velocity” has zero to do with any of this. A balloon cannot escape the atmosphere, much less Earth orbit. Not sure where you got the idea that escape velocity is in here somewhere; it’s not.
Imagine a balloon made of something that weighs zero. Not almost zero or nearly zero, but exactly zero. Impossible of course, but go with it.
This zero-weight balloon with some helium in it will rise from ground level in the atmosphere because the helium inside weighs less than the air around it. As it rises, the atmosphere pressure drops away. So the helium expands to be the same pressure as the surrounding air. As it does so it remains lighter than the surrounding air and it continues to rise.
This continues *only *as long as the balloon is not yet full, i.e. its total cubic foot capacity is greater than the volume of the helium under the current atmospheric pressure & temperature.
Eventually as the atmosphere pressure drops away the helium will expand to fill the balloon completely. Once that happens the game is over. The balloon won’t expand any more and so the density (weight/volume) of the helium is now fixed.
From now on, the higher the balloon goes the less light the helium becomes relative to the air. IOW, helium starts out at 15% lighter than air, which declines to 10%, then 5%, then 1%, then 0.0001% as you go higher and the atmosphere keeps getting less dense but the helium trapped in the full balloon doesn’t get less dense anymore. The higher it climbs, the less buoyant force there will be and the more slowly it’ll climb. Eventually it gets to equilibrium and stops climbing.
In the real world with balloons that don’t weigh zero the same exact thing happens. It just starts out lower and finishes lower because the helium needs to buoy not only itself but the weight of the balloon too.