Ejection Gas Collection Recovery System

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Jordz
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Ejection Gas Collection Recovery System

Postby Jordz » Thu Jul 14, 2016 9:20 pm

In my intro i told you to look out for my terrible ideas, so i suppose i should actually share one.

I have an idea about using balloons as a recovery device. As in inflatable party balloons, the big ones not the normal ones. All actual deployment put aside (ill get to that after) i cant see why using a balloon to collect the ejection charge wouldnt work provided it displaced the right amount of air. It would also likely be far easier to spot a large inflated balloon in the sky than a parachute. Also the balloons are a dime a dozen, and all the parts required would be easy enough to find.

How? Ive seen peoples threads about using CO2 canisters etc for this, and ive never seen them pass the hypothetical stage yet. My idea is "more simple". A brass coupler on the ejection side of the motor, silicon hose runs the full length of the body tube plus 50%, one way check valve on the end of the hose, balloon on the other end of the valve. The motor burns the ejection charge, the pressure in the silicone line expands the coiled line popping off the nose cone and pushing the expanding balloon out. Simples.

Theres only two points im really unsure on. Ejection gas temperature and ejection charge gaseous volume. Can anyone shed any light or care to discuss?
Last edited by Jordz on Thu Jul 14, 2016 9:31 pm, edited 1 time in total.

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Jordz
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Re: Ejection Gas Collection Recovery System

Postby Jordz » Thu Jul 14, 2016 9:31 pm

I should add, if theres enough "faith" in the idea im happy to guinea pig it too. I just dont want to pour too much time and effort into it if ive missed something blatantly obvious :)

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Re: Ejection Gas Collection Recovery System

Postby SpaceManMat » Thu Jul 14, 2016 9:59 pm

Well it's going to add complexity to something that works well. 10/10 for a creative idea, but I cannot see any advantage to doing it this way.

Came back with a 5mm hole in my cute protector from the last launch, this will be your main issue. How to prevent hot ejection particles burning a hole in your balloon. If you really like to experiment then sure, give it a shot. I would recommend you build a test article to prove you can do this reliably. You also need to think about ballon size vs decent rate.
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Happy Heyoka
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Re: Ejection Gas Collection Recovery System

Postby Happy Heyoka » Thu Jul 14, 2016 10:53 pm

There are many exotic recovery devices that have been tried (I have done helicopters and gliders with LPR)... never seen a balloon... but having had a nice dinner and a glass of wine I am happy to have an opinion :wink:

As far as I know, most of the compressed gas systems are instead of pyro - basically a drop in replacement - everything else is standard "push off the nose and pop the chute".

I second the idea of doing a static test (it'll cost you some motors/black powder) - I'm guessing that something like a latex balloon will just blow apart (I'm thinking rate of increase in pressure being the problem) or burn through. In Stirling engines they use a mesh thing between chambers that is designed as energy recovery device but doesn't restrict the gas too much; maybe something like that would catch the burning bits of stuff? (Like the baffle system you see in some rockets but finer).
Getting it out of the tube is a whole other problem.

Since I guess you're not planning on getting lift/displacement from the balloon, then you're basically doing the same thing as a parachute and so the size of the balloon would need to have about the same drag as the appropriate parachute? (ie: factors in to volume of gas).

I have a few papers about various kinds of exotic "aerodynamic decelerators"; the closest thing that comes to mind is a flexible wing where they use compressed gas to inflate the wing on deployment... but they're not trying to do that for more than the time it takes to unfurl the thing. JPADS and "ram air parachutes" come to mind as search terms.

Anyway, don't let anyone stop you from playing - I say have at it
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OverTheTop
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Re: Ejection Gas Collection Recovery System

Postby OverTheTop » Fri Jul 15, 2016 7:10 am

A stainless steel scourer (a bit like coarse steel wool) can be purchased from the supermarket. Put some of it in a tube (longitudinally restrained somehow) to catch the larger hot bits of the burning BP. It makes a great baffle.

Good luck with the experiments and idea.
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Re: Ejection Gas Collection Recovery System

Postby High Impulse » Fri Jul 15, 2016 11:13 am

I'm not sure if this will be the case or not, but i remember mythbusters once tried to seat a tyre using an explosion of cold gas. It worked well and seated the tyre fine (so I am assuming that should your balloon handle the heat and the high strain rates it will probably inflate), however, the gas quickly cooled causing the tyre to contract and pretty much wrecking all hopes of the system working (thus it is possible the balloon may contract after inital expansion). I would give it a couple of static runs though cause it is an interesting concept.
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Re: Ejection Gas Collection Recovery System

Postby ogivemeahome » Sat Jul 16, 2016 8:28 am

When you compare 'chute to balloon;
- the 'chute only has to be in the airflow to 'inflate'
- a balloon wants to be smaller, thus the air in it will be compressed, thus there'll need to be more air
- you may need something like a 'fly apart airframe' for the balloon to be released reliably?

My thinking is that the added complexity would negate any benefits (happy to be proved wrong though :) )
It might be worth looking at marine vehicles for ideas?
If you can make it work it may have other applications?
Good luck and happy designing. :)
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Re: Ejection Gas Collection Recovery System

Postby Jordz » Sat Jul 16, 2016 11:40 am

Im aware this adds complexity for very little if any gain, im just more curious about it now.

Ive had a bit of a re-think regarding design and i think there is a higher chance of sucess if the balloons are mounted externally. It will also reduce the complexity and total weight. Im thinking of having the nose cone 'fixed' but obviously still removable for serviceability, and just having two check valves go the body tube, linking the balloons to the internals. Chances are any ejected particles arent going to make a 90° turn down the check valves so thats baffling sorted. The body tube itself will also act as a thermal exchange for the gases. Not sure if it will do much, but the larger surface as opposed to a 10mm silicon hose could only be beneficial.

The only bit left to figure out is how to mount the balloons on the outside in a way the wont affect the flight dynamics too badly. Obviously this will only be a LPR toy but still, no one likes an uncontrolled flight. Thats my thoughs for the hypothetical design anyway. Im yet to bench test if the ejection charge even displaces enough gasses for it to stand a chance of working.

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Re: Ejection Gas Collection Recovery System

Postby Jordz » Sat Aug 06, 2016 8:58 pm

Well ive bench tested a few motors to measure the volume of ejection gases that are emitted. I have tried a a B6-4, C11-5 and a D12-5 and all are basically the same quantity of gas.

The test was a static test, motor mounted in my bench vice. The motors were connected to a spacer tube using a high strength fibre reinforced adhesive (cloth tape) and the other end of the tube connected to a gas collection vessel (plastic bag). The total volume of gas was measured using my eyecrometer (i looked at it and guessed).

Log and short of it, its not a viable recovery option. There is not even remotely close to enough gasses that could be used, to the point where the bag i used was rolled up and pushed out less than a shallow breath would produce. But, at least now i know it wont work haha.

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Re: Ejection Gas Collection Recovery System

Postby SpaceManMat » Sat Aug 06, 2016 9:45 pm

Are you going to try some other methods to creat gas?
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Re: Ejection Gas Collection Recovery System

Postby SL666 » Sun Aug 07, 2016 8:42 am

1/2a motor? :) - on delay

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Jordz
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Re: Ejection Gas Collection Recovery System

Postby Jordz » Sun Aug 07, 2016 12:42 pm

A 1/2A may work, but its becoming increasingly technical for LPR. I think an airbad type recovery might be a realistic recovery on a few MPR systems, but if you are going to the effort of igniting another engine its probably going to be just and easy to use a CO2 canister, and probably a whole lot safer.

I dont have any other plans or ideas for airbag type recovery at this point, but im open to ideas if anyone else wants to chime in.

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Re: Ejection Gas Collection Recovery System

Postby ogivemeahome » Sun Aug 14, 2016 7:54 am

Jordz wrote:But, at least now i know it wont work haha.

Thomas Edison successfully tested 99 ways how not to make a light bulb. ;)
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Re: Ejection Gas Collection Recovery System

Postby OverTheTop » Sun Aug 14, 2016 8:13 pm

University of Melbourne Space Program are designing a cubesat currently. One part of its cleverness is an inflatable antenna. I can't recall what chemical means they are using for inflating the antenna, but it will likely be cooler than burning BP. You might enquire there...
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Re: Ejection Gas Collection Recovery System

Postby Oldboy » Mon Oct 24, 2016 11:59 pm

Try a rat and put it on a high fibre diet or maybe two mice .
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