# [amsat-bb] Questions On Balloons With Amateur Packages

Bill Dillon bill.g.dillon at gmail.com
Fri Dec 30 22:50:31 UTC 2016

```Excellent description of the physics, Joe.  I think the really incredible
thing is how impermeable these balloon skins must be to circle the earth
multiple times and remain aloft for weeks or even months!

73 de Bill, KG5FQX

On Fri, Dec 30, 2016 at 4:21 PM, Joe <nss at mwt.net> wrote:

> Jeff and the others.
> Both are close but also not totally correct either.
>
> Bob has the correct theory about size and max altitude.
>
> And Jeff is also correct about the home made custom envelope.
>
> BUT......
>
> These are NOT zero pressure balloons.
>
> They are acting as super pressure balloons.
>
> They are sealed tight, And Must be perfectly tight as they say "Bubble"
> tight.
> Any leak at all, and the flight will not even last 24 hours.
>
> As Jeff said "they put enough gas into to get it off the ground with a
> specific amount of lift. "
>
> Very true and that is the key to these flights, they are talking lifts
> level in the amount of grams, not even a single ounce. In like the big
> latex flights that we all have done. My group has done 60+ of them some
> fill lifts is the mounts of pounds even more than the payload weighs. And
> of course all those flight last 90 to 120 minutes mostly.
>
> Now again as Jeff Said, "they put enough gas into to get it off the ground
> with a specific amount of lift. "
>
> The amount of lifts are minimal. and as any balloon flight that happens
> once you have positive lift you WILL have positive lift until something
> happens. PERIOD!
>
> In ANY balloon the gas expands to equalize the pressures inside vs outside
> the balloon. Just like ANY and EVERY balloon does.
>
> But once the balloon is as big as it can get the inside volume can not get
> any greater, One of Three things happens.
>
> 1- The internal pressure just like a party balloon or the 30 foot diameter
> latex balloon, if you put too much inside more volume that the balloon can
> hold, the envelope ruptures and it's done.
>
> 2- The Zero pressure balloon behaves in the exact same way expands as
> gasses expand. BUT, once it is full and can not expand any more, instead of
> rupturing, built into the balloon is a special valve that lets some of the
> gas out, so the internal pressure can not build up high enough to cause the
> balloon to rupture. Eventually enough gas is released and the balloon does
> not go any higher and it floats somewhat like these long duration flights
> have been. BUT not the same. because these zero pressure balloons. Once the
> sun goes down they loose that energy, gasses shrink and the balloon comes
> down. The ONLY was a zero pressure balloon can stay aloft is to drop about
> 10% of it's weight every sundown.
>
> 3- Now this is how these flights are happening, they are operating in the
> world of "Super Pressure Balloons" Just on a tiny tiny scale.
>
> Now how this system works.
>
>      In reality the numbers used are incredibly small and stretched out to
> several decimal places. But for explanation purposes here I will use large
> and rounded off whole numbers just to make it clearer and less number
> cumbersome.
>
>      At sea level or close to it, just enough lifting gas is injected into
> the Balloon.  Just enough to give the few grams of lift.
>
> But for easier to understand   Say  In this case say Free lift will be 8
> ounces.
>
>  So in other words when the lifting balloon is filled to the correct
> amount and everything is attached in the flight train, there is an excess
> of 8 ounces of lift.  ( like I said these numbers are extremely larger than
> the real ones.
>
>      Say the volume of the balloon when full is 160 cubic feet. We
> calculate that if we put in 16 cubic feet on the ground, once it reaches
> 60,000 feet it has expanded and filled the balloon fully.  Remember these
> numbers are all wrong and are not even close. It is just to explain how the
> system works.
>
>      Now is when the magic starts. As with any normal balloon as it rises
> the atmospheric pressure and density drops. And any regular balloon also
> expands to equal out the pressure and also overall density. But this is
> where this system is different and is cool.
>
>      Say at 60,000 feet, the density of air is 0.1 ounce per cubic foot.
> So, In this balloon, it is contains a volume of 160 cubic feet that weighs
> 16 ounces. I know it is less because it is a lifting gas, but the theory is
> all the same.
>
>
> And since it has a volume of 160 cubic feet, it is also displacing 160
> cubic feet of air outside the balloon that also weighs 16 ounces.. 0.1
> ounce per cubic foot.
>
>      OK, we still have positive lift of 8 ounces and the flight train
> continues to rise. It is rising into less dense air of course.
>
> So now say it is at 70,000 feet.
>
> Pressure has dropped, and the air surrounding the balloon is less dense.
>
> BUT, the balloon envelope could not stretch any more and did not allow the
> 160 cubic feet of "GAS" inside the balloon to equalize the pressure and
> expand.
>
> The 160 cubic feet of gas inside the balloon, is still having the
> properties of the gas had at 60,000 feet. I.E.: It still weighs 16 ounces.
>
>      But the air at 70,000 feet outside the pumpkin has expanded and
> became less dense.
>
> It is now having  a density of 0.05 oz per cubic foot.
>
> So The balloon is still displacing 160 cubic feet of the atmosphere.
>
> But this atmosphere at 70,000 feet weighs less than it did at 60,000
> feet.  0.05 oz per cubic foot. So 0.05 X 160 cubic feet = 8 ounces. And now
> because of this, the whole flight train stops rising because the train has
> magically become 8 ounces heavier than it was at 60,000 feet!
>
>      The gas in the balloon still weighs 16 ounces, but the air it is
> displacing only weighs 8 ounces, so the balloon is 8 ounces heavier now.
> How cool is that?!  And that is it! That's how it works. Pretty cool huh?
>
> And thats how these balloons are staying up there for these incredible
> times.
>
> Joe WB9SB
>
>
>
>
>
>
>
>
>
> Sig
> The Original Rolling Ball Clock
> Idle Tyme
> Idle-Tyme.com
> http://www.idle-tyme.com
>
> On 12/30/2016 2:50 PM, Jeff Moore wrote:
>
>> 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
>>> 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
>>>
>>>
>>> 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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>>> _______________________________________________
>> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
>> to all interested persons worldwide without requiring membership.
>> Opinions expressed
>> are solely those of the author, and do not reflect the official views of
>> AMSAT-NA.
>> Not an AMSAT-NA member? Join now to support the amateur satellite program!
>> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
>>
>>
>>
>>
> _______________________________________________
> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions
> expressed
> are solely those of the author, and do not reflect the official views of
> AMSAT-NA.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
>
```