Re: NASA Breaks a Balloon Altitude Record
Don't forget the weight of that Giant Balloon!
toggle quoted message. . .
My "LITTLE" 300,000 Cubic Footer
weighs 31 pounds
On 9/13/2018 10:51 PM, Hank Riley via
The usage of helium for the typical amateur balloon
refers to ground level conditions, similar to Standard
Temperature and Pressure which is 20 Celsius and 1013
The 60 million cubic feet of the NASA "Big 60" balloon
refers to the fully inflated envelope at its peak
(equilibrium) altitude of 159,000 feet. The pressure
there is under a millibar, so the gas is expanded over a
thousand times in volume over what it was on the surface.
The standard atmosphere specifies a mild temperature very
near STP, but during the day there must be significant
heating to the envelope. I'll just deal with the pressure
difference which dominates.
So whittle those 240,000 amateur balloons down to more
like 240 as a result of dividing by 1000. And now the low
volume, retail customer cost estimate is $600,000 instead
of $60 million.
Sanity/error check on the 240,000 balloon answer:
Mark was using as typical a 1200 gram balloon
and 250 cubic feet. For helium
that's good for about 8 pounds of payload
according to Liftwin.
The NASA instrument payload was 200 kilograms
= 441 pounds.
8 x 240,000 = 1,920,000
pounds of payload lift = 960 tons lift! Impossible.
The specific solution is as follows neglecting extra
balloon gas heating beyond ambient and giving STP gas
At 159,000 feet, it's .992 millibar and 271 Kelvin. STP
is 1013 millibars and 273 Kelvin.
60 * 10**6 * .992 / 1013 * 273 / 271 = .059 *
10**6 = 59,000 cubic feet (for the on-the-ground volume
of helium for the Big 60)
Well, if you figure ~250 cu
ft for a typical 1200g balloon, around 240,000.
That's a lot of ARHAB flights!
If they were paying
commercial rates for their helium (which I think is
approaching $1/cu ft again), that'd be $60M for
their lifting gas for that mission. Somehow I doubt
they're paying that much.
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