#### Re: Where can I buy floater balloon?

J68HZ

Some science here.

Balloons lift (are buoyant) on the basis of Archimedes principle (cite: https://en.wikipedia.org/wiki/Archimedes%27_principle) which has the corollary that less dense material will rise above more dense material.  It’s the same principle that causes oil to float on water… and with gases, it causes the lightest one (less dense gas) to rise above a heavier gas.  Even hot air will rise above ambient air just because the density of the air in the balloon is less than that of ambient air.

In the buoyancy calculation, the force of lift is proportional to the relative differences between the densities of the gases… and in this case, that would be H2 (or whatever the lift gas is) and air.  Now, the density of a gas can be calculated from the ideal gas law… P*V=n*R*T, or rewriting, P=p*R*T/Mw where “p” is the gas density and “Mw” is the molecular weight of the gas.  The ratio for lift is then [P1*Mw1/T1]/[P2*Mw2/T2].  Plug in the numbers and you can determine where the lift will cease.  Of course you need to do a force balance for the real lift and include the weight of the payload and the balloon.

The point here is that the buoyancy can vary based on the ambient temperature and pressure… even of the temperature and pressure of the gas in the balloon stays constant.

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Moderator – North American QRO Group at Groups.IO.

email:  bill@...

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Mikael Dagman
Sent: Sunday, May 26, 2019 1:28 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] Where can I buy floater balloon?

The balloon was filled and stored in the same room in the house.

There is some unknown factors in play here, probably the material change characteristics at altitude, be it temperature, pressure, lack of moisture and that the He have expanded and is now filling the whole envelope and just not concentrated to the top part of the balloon as it is a ground level.

So anyway, if you going to fly fill just before lauch and not a day or two before.

/Mikael

 Virus-free. www.avg.com

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