[aprssig] WB4APR-11 Balloon Aloft from Annapolis

[Robert Bruninga]

Bill Brown has been doing ballons for decades.  A party balloon is called
a super-pressure balloon because once it is fully inflated, it cannot
expand any more.

SO you fill it with an exact amount of helium that will expand to fully
fill the balloon only when it gets to the altitude where the balloon is
fully inflated.

So with atmospheric pressure on the ground at 28 inches of mercury, and
pressure at 25,000 feet is 11 inches of mercury, so then to fly at 25,000
feet, you only but in 11/28ths of the helium to fill the balloon.  Or
something like that.

But it is impossible to go above about 30,000 feet with party balloonos
even with a weightless payload because the weight of the balloon itself
can only support itself when full at about 33,000 feet.

To go higher (without bursting) you have to have a larger balloon that
weighs less. And wont burst...

Etc
Bob

-----Original Message-----
From: Curt, WE7U <curt.we7u at gmail.com>
Sent: Monday, August 13, 2018 3:51 PM
To: Robert Bruninga <bruninga at usna.edu>
Cc: aprssig at lists.tapr.org; Anika Williams <fiub2 at hotmail.com>
Subject: Re: [aprssig] WB4APR-11 Balloon Aloft from Annapolis

On Mon, 13 Aug 2018, Robert Bruninga wrote:

> It is a single 3' mylar party balloon and will cruise around 30,000
> feet or so and not well above weather, so it will be a risk to see if
> it makes it across the Atlantic.

You missed the altitude by 6.3%...  hi hi

How did you guys calculate it so closely? Knowing nothing about balloons,
I'm guessing something to do with uplift force of the balloon minus
downward force of the load, then some equalization altitude based on
current conditions?

Fun to watch!

-- 
Curt, WE7U.        http://we7u.wetnet.net
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