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Using ejection charge to inflate a balloon

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Scott_650

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Oh man... I so want to see a "Bench Test" of this.

I wonder how NASA did the inflatable balloons on the Apollo capsule?
I don’t know what they did for Apollo but the Project Echo ”satelloons” we’re literally giant aluminized balloons launched into LEO and inflated so radio signals could be bounced off of them. The article I read only said they used gas generating reactant chemicals but not what they were. Fun facts - Echo 1 stayed in orbit for nearly 8 years! The giant rotating horn antenna developed for the ground station part of Project Echo detected the first evidence of background radiation predicted by the Big Bang theory.
 

lakeroadster

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This doesn't answer the "how were they inflated" query... but it sure is an interesting discussion:

 

Alan15578

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What is the volume/ gram of BP for fresh hot exaust at standard atmospheric conditions?
What is the same Volume/gramm after cooling to standard atmospheric conditions?
 

BABAR

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Aw, heck, I was bored, and haven't played with pyro for a while, so I whipped something up. Here it is, the Rocket Balloon Inflating Device, version 0.3:
View attachment 432815
View attachment 432817















That tube is about 1/4" ID and 7'16" OD. To the left of the igniter wire is a clay plug, and about 1/4" of pyro comp. To the right is packed with stainless steel scrubber, and the balloon.
QED
Wow, Bob’s your uncle!
 

jqavins

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Aw, heck, I was bored, and haven't played with pyro for a while, so I whipped something up. Here it is, the Rocket Balloon Inflating Device, version 0.3:
That was right before I wrote my post:
I confess I haven't read all the posts.
I guess I should have read them all.

Did you monitor the setup for a while afterward? I'm still really concerned about losing the pressure as the gas cools.
 

MClark

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An issue after inflation is a sphere has a low CD at reasonably slow speed and will drop like a stone.
Loki Sounding rockets used a device called the Robin Falling Sphere to measure air density. It fit in the dart and was ’50’s technology.
Another was a balloon inflated by ram air called a ballute.
 

Kelly

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Did you monitor the setup for a while afterward? I'm still really concerned about losing the pressure as the gas cools.
Yes, I watched for a minute or two. Yes, I noticed the balloon shrinking a bit - 10-15% (?? just eyeballing it) as it cooled. Of course it's never going to shrink to zero due to cooling. Also note that the amount it shrinks/cools depends on how much heat is initially absorbed by the heat sink (pot scrubber).
 

OverTheTop

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I have heard of a gas generating material that was going to be used to inflate an antenna on a cubesat. I think it was University of Melbourne, a couple of yours back. Heating was provided electrically I think. Sorry I can't remember more details.
 
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