pulsejet combustion in microgravity

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Mike Everman
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Re: pulsejet combustion in microgravity

Post by Mike Everman » Fri Dec 31, 2010 4:57 pm


I agree with Viv. You have to ask yourself what would be a meaningful experiment? A small pulse jet will have things happening very fast, chaotic and and incredibly difficult to record, at least visually, and there's a very low probability that you will sense any difference between zero g and a 1g field operation.
IMHO, you need an experiment that compels the NASA guys to pick you, that, if not totally groundbreaking, uses tools with big names or uses equipment you may have to borrow from them.
One idea is a shock tube made of quartz, premixed fuel air charge, and touch it off in the middle of it's length. You could put Saran wrap ends for obvious reasons, and use high speed schlieren or pseudo-Schlieren video of the event.
While there will be little discernible difference between zero g and the tube oriented vertically on earth, there will be very interesting differences between zero g and horizontal in a 1 g field... Or will there? Ha ha, thats why the experiment.
Naturally, the project starts with a prediction. Do you have 2d analysis software with combustion? Can you have a gravity field in this analysis? Etc..
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Re: pulsejet combustion in microgravity

Post by HellionFlier » Fri Dec 31, 2010 9:25 pm

Yes, I was thinking of using high-speed cameras to record the combustion events, but I didn't think of using quartz. I assume the quartz is there because it's see-through for the cameras to record?

I saw a paper about bubble formation in microgravity. A couple of Japanese scientists tried it in a drop tube, and the micro-g lasted about 10 seconds. The bubbles were considerably larger in micro-g than in full gravity. The most plausible explanation I can think of is that the lack of gravity lessened the water pressure surrounding the bubbles, so they could grow larger without bursting.

I think a similar phenomenon would take place in combustion. The lack of gravity would cause lower pressure inside the chamber, post-combustion. What that leads to, I'm not sure.

No, I don't have 2d analysis software. If you could point me to a free downloadable, that would be great.

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Re: pulsejet combustion in microgravity

Post by Rocket Man » Fri Dec 31, 2010 9:52 pm

Surely you plan to test fire your jet engine to make sure things work as planned before you try it on the vomit comit.

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Re: pulsejet combustion in microgravity

Post by Mark » Sat Jan 01, 2011 3:19 am

"When the gas flow rate is comparatively small, a spherical bubble does not detach from the nozzle and continues to expand in quiescent liquids."
http://www.sciencedirect.com/science?_o ... archtype=a

"The presence of gravity is essential in all bubble formation models. If the gravitation acceleration were zero, the bubble shape would be spherical and the bubble would grow infinitely large. Therefore, in the case of microgravity, a small but finite value of g was assumed when computing bubble size at detachment." (First paragraph of page 16)
Presentation is Everything

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Re: pulsejet combustion in microgravity

Post by Rocket Man » Mon Jan 03, 2011 2:49 pm

It would be smart to check history to see what experements others have done in the past, which experement won and why. If your trying to win this would be the best way to decide what experement NASA is interested in. You probably don't want to repeat an experement that has already been done unless you can expand on it. Old experements will give you ideas for a new experement. I hear NASA is doing away with the space shuttle and are now interested in an airplane that can fly into space, return and land. The military is interested in bombs that will orbit the earth then hit a target anywhere on earth. Experements have been done with space laser weapons. The military is in need of the auto gun, a computer controlled gun that can see a man hiding in the mountains the computer controlled gun will automatically shoots and takes out the target. The military has high hope for the auto gun research is already being done. A lot of research has been done on the pulse cannon it works fine but no major damage to the targets it turns them into a swiss cheese full of holes and the target is rarely distroyed.

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Re: pulsejet combustion in microgravity

Post by nitro » Tue Jan 11, 2011 4:12 am

My guess is a Pulse Jet would work fine in a vacuum if desined for it.A stock Pulse jet runs off some air brought back from the outlet.If that is true that would have to change.A rocket engine works better in outter space so why not a properly decined pulse jet.

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Re: pulsejet combustion in microgravity

Post by Viv » Tue Mar 08, 2011 3:36 pm

I just noticed a little article on zero G combustion today so thought i would add it for your enjoyment ;-)

http://io9.com/#!5779127/how-does-fire- ... ro-gravity

"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

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