[NLRS] Balloon beacon..

[Ford Peterson]

Donn,

I won't hold you to the Dr Pepper.  The 'bet' was just a friendly gesture for entertainment purposes only.

The reason I said 30K' was because of other balloon rides I've seen--particularly in Kansas.  They would get 18k' to 25k' and then fail for one reason or another.  I followed them very closely a couple of years ago.  

The trouble is, most ham payloads are heavier than the Wx service package.  So people over-fill them to get them to lift.  Boom!  They pop early due to over inflating.  In an attempt to prevent this, they under-inflate them and again--Boom!  Even when underinflated, I believe that the balloon continues to stretch as it rises very slowly.  Either way, you don't get much height.

About the only way I can figure to circumvent this is to use 2 balloons (twice the helium) to get enough lift to make for a fast ascent.  The weather service has this all dialed in pretty good, based on their standard payload.  Hams tend to use a different payload on every flight and never do get it dialed in properly.  I wonder how the Wx service controls the volume?

I would bet that they use a standard orifice to control the flow into the balloon.  Then use a stop watch to control the actual volume of helium based on a table with air pressure, weight, and time-to-fill.  No, I am not aware of such a table, but I'll bet one does exist for their standard payload.

Using the formula for a sphere is no good.  volume =4/3piR^3 = 1/6piD^3  This may prove to be an approximation, but a lousy one since the balloon is not a sphere.  I would further 'bet' that the form factor is not the same for any two balloons.

Here is a link to NASA's model of the standard atmosphere from 0km to 120km.  

http://nssdc.gsfc.nasa.gov/space/model/models_home.html#atmo

Basically, you take the weight of the air at a given height, subtract the weight of helium at a given height, and you have the lift at that height.  Adjust the helium/air pressure/volume until you reach burst volume for the balloon and you have your equation for how high the balloon will go.  Of course, there are 1000 variables you cannot control, most notable of which is the quality of the balloon, and volume of helium injected.

Ford-N0FP
ford at cmgate.com

----- Original Message ----- 
From: "Baker, Donn B" <Donn.Baker at UNISYS.com>
To: "Ford Peterson" <ford at cmgate.com>; "NLRS vhf/uhf reflector" <NLRS at mailman.qth.net>
Sent: Monday, August 29, 2005 10:32 AM
Subject: RE: [NLRS] Balloon beacon..


I assume you have other bad habits, too....

Ahh, well.  When will be be in the same place at the same time ?  Will it be before the "MidWINTER Madness" 'fest in Buffalo next SPRING ?

(Know they didn't have Dr. Pepper this year... I think they had Pepsi, though.)

73 Donn
WA2VOI/0

> -----Original Message-----
> From: nlrs-bounces at mailman.qth.net
> [mailto:nlrs-bounces at mailman.qth.net]On Behalf Of Ford Peterson
> Sent: Sunday, August 28, 2005 6:32 PM
> To: NLRS vhf/uhf reflector
> Subject: Re: [NLRS] Balloon beacon..
> 
> 
> 
> 
> > The beacon telemetry showed 456m (1496')ASL as well as it's 
> location.
> 
> 
> I prefer Dr. Pepper but Coke is OK too...
> 
> Ford-N0FP
> ford at cmgate.com
> 
> 
> 
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