[amsat-bb] Questions On Balloons With Amateur Packages

[Jeff Moore]

Interesting concept (mylar party balloons), but no, that is not what they
are doing.   They're using a custom made mylar envelope that I suspect is
using very very thin mylar,  this is a rather large envelope that you put
enough gas into to get it off the ground with a specific amount of lift.
The ones that have been flying are stabilized at around 50 to 60,000 ft.
and will hang at that altitude as long as the gas is contained within the
envelope eventually slowly lowering in altitude until they can't sustain
flight any longer.

AS the balloon rises, the gas expands and fills up more of the envelope,
the envelope should never actually get round like a traditional balloon
unless the volume of gas at altitude approaches the actual volume of the
envelope.   At no time should you be able to get a pressure reading from
the balloon - hence why it is called a zero pressure envelope.   Definitely
not a party balloon.

Jeff Moore  --  KE7ACY
Near Space SIG - High Desert Amateur Radio Group
Bend, Oregon

On Fri, Dec 30, 2016 at 9:19 AM, Robert Bruninga <bruninga at usna.edu> wrote:

> We tried zero pressure balloons (Mylar party balloons) but the max
> possible height was just 23,000 feet or so due to the weight of the
> balloon itself.  It's a direct calculation.  So we paralleled balloons,
> but still, no matter how many balloons you add, the math still comes out
> to asymptotically approach the same max altitude due to the mass of the
> balloon material itself and its volume.
>
> We did learn one other thing.  With 5 under filled Mylar balloons to reach
> a cruise altitude around 23,000 feet (from memory?) we sent the cut-down
> command and nothing happened.  (launching from Maryland is a guaranteed
> ocean landing unless you can come down in 65 miles or so)...
>
> On recovery, we found one balloon had burst, and so it hung DOWN from the
> other 4 and got all wrapped around the payload.  So when we sent the
> cut-down command, it worked, but the entangled lines kept everything
> together.
>
> But now with only 4 of the 5 balloons providing lift, it came down at a
> very slow rate...  about the same as the ascent rate... which means we
> chased it TWICE as far as intended.
>
> Oh the fun of discovery!
> The event is shown on our web page (Spycam mission starts about 30% down
> the page)  http://aprs.org/balloons.html
>
> Bob, Wb4APR
>
>
>
> -----Original Message-----
> From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Richard
> Tejera
> Sent: Friday, December 23, 2016 3:08 PM
> To: Dave Marthouse; 'AMSAT'
> Subject: Re: [amsat-bb] Questions On Balloons With Amateur Packages
>
> Dave,
>
> Knowing the weight of the payload, they will fill it with enough gas to
> become neutrally buoyant at the target altitude.
>
> If altitude is the goal, enough gas will be filled to take it to an
> altitude that will exceed the Burt diameter.
>
> Rick Tejera K7TEJ
> Saguaro Astronomy Club
> www.SaguaroAstro.org
> Thunderbird Amateur Radio Club
> www.w7tbc.org
>
> On December 23, 2016, at 11:01, Dave Marthouse <dmarthouse at gmail.com>
> wrote:
>
> I have seen posts from time to time on the BB about balloons with amateur
> radio payloads on them.
>
>
> I've got a question regarding the missions that carry payloads around
> the world.  What stops the balloons from going up until they explode do
> to the high altitude.  How are the packages kept from doing this to
> achieve such long distance flights?
>
>
>
>
>
>
> --
>
> Dave Marthouse N2AAM
> dmarthouse at gmail.com
>
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