SpudFiles

Hey there La compagnie!
Just a quicky to show you my first steps in the world of hybrid rocketry!
Hope you like it!
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How much thrust is this little engine putting out?

So what were you using for ignition?

You're showing a cigarette lighter (seriously??) lighting a gas flow. PE is a solid. GOx doesn't burn on it's own. Clearly there was a gaseous fuel of some sort involved if for nothing else than ignition....

Also, with only 30 psi inlet, are you even certain that you choked your flow?

This test was not done for thrust. I only wanted to familiarize myself before getting serious.
@D_Hall: Cigarette lighter was used for the simple fact I was using very little amounts of propellant and the oxygen regulator is set very low on pressure.
No gaseous fuel were involved, only a small fuse of PE or wood was inserted. I edited the video so you don't see me fighting for ignition, that's why it appers to be lit instantaneously.
You can also see that different nozzles were tried. A simple end cap, a brass nozzle and a galvanized steel one. The best results where the end cap and the steel one, because the brass nozzle is too wide. (1/4")
Chamber pressure was very low on these tests, today i'll try a bigger chamber to increase the fuelgrain/nozzle ratio, and if that doesn't achieve proper rocket exhaust, i'll lower the nozzle diameter again. (i'll try big than slowly decreasing.)
With the bigger chamber, don't expect me to light it with a cigarette lighter. Blowtorch will be used on this one.

(The reason I used little wood sticks is that my PE fuses would burn and clog the nozzle. as pressure is built up it would be ejected without even having the time to light the propellant. My PE propellant was bad quality, hense the very low chamber pressure. Paraffin works better and burns somewhat cleaner. )

Can you use regular compressed air as the oxidiser for a hybrid rocket?

Yes you can, but air is only 20% Oxygen.
I narrowed down the problem. As D_Hall said, not enough oxygen to increase the chamber pressure. My fuel burns too slowly. The chamber pressure can not increase fast enough. I'm screwed, because i'd need a bigger regulator and a bigger bottle, and it costs money, money I don't have...
I'm thinking of going back to the small chamber and making a smaller nozzle, smaller than 3/16" . My main concern would be a nozzle obstruction.
Tell me if you have ideas I don't!

New tests, Enjoy.
O2 pressure and flow has been dramaticly increased since last time, resulting in more noise, more thrust (only felt when holding the setup) , and smaller burning times.
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Thats awesome.. I don't know much about hybrid rocketry but it looks like your on a good path

Haha that's pretty awesome. Looking forward to more videos!

Sacre bleu, I came to this thread expecting a couple of bottles of Dom Pérignon strapped to a scale model of the Eiffel tower with a fire burning underneath it... great job!

Will this actually be fitted to a moving vehicle of sorts?

Very nice the second video looks great, especially the sparkler ignition
This may sound silly but is there any-chance of getting some pics/video of your setup , i have been interested in hybrid rockets ever since i saw this:

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But i am not sure where the best place is to start with these hybrid rockets is, any pointers ?

The last run was unexpectedly loud.!
It made a very deep "POMMM!!" like a firearm, then continued on burning for 1.5 second with the same intensity , then the fuel had almost been burned but the combustion stayed another 2.3 seconds.
Burning a 52.16grams fuel grain of paraffin + 85 grams of O2 in 3.8 seconds, and using NASA's CEA for exhaust speed simulation (mach 2.6) gives:

dm/dt=36 g/s => 0.036kg/s
mach 2.6 => 884 m/s

=> T=0.036x884 = 32 N of thurst

That's assuming the burn was slower than it really was. So that's average thurst. The peak thrust was higher than that.

The last test was the most succesful, but holy crap these things use a lot of oxygen to get a good exhaust!
Plus, after over 15 tests the conclusion is,
1) It's awesome (when it actually works)
2) costs: 65 cents of paraffin + 4 euros of oxygen per test (@ 120 psi input)
3) method for pouring fuel grain is very important
4) Nozzle is the most critical part. Misaligned and you are screwed, too wide and you are screwed, to narrow and... you get the message.
5) heats a lot. On the first test you can actually see the steel nozzle liquify a little at the top edge in only seconds.

Mach diamonds are often visible through welding gogles, but the intense brightness and their small size make it difficult to capture on camera.

@Jazzman : The setup is very simple but I think you should be able to draw something and make it.
I use a 1m3 oxygen bottle with a regulator, oxygen hose to 3/8" ballvalve and into the chamber. Everything secured in a vise.

@JSR : I do not think i'll strap it to a moving vehicle. 32N of thrust is not much, and I don't have the time to build such a vehicle. However, I still have the bottle of oxygen until September, so if I have time after i give my report to my professor, it's not totally excluded that I continue experimenting!

why not use nitrogen oxide?
wouldn't that be cheaper?


wow... not sure if the guy was acting from 7:00 onwards or not... lol I would react similarly
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Cheaper maybe... But I can't find NO2, and it polutes once in the air. It reacts with ozone and is somewhere around 300 more times green-house-effet active than CO2.
The Bottle of oxygen I got for free. My plumber gave it to me for free, because he has other ones. So the only thing I need to worry about is the refill costs, which stand in the 65 euros per cubic meter ( one complete bottle fill). I use up to 60 L of O2 per run, which translates into 20 ish tests per fill.

New test!
Much more power!
If my maths are good, this little puppy achieved more than 40N of thrust!! That's close to 9 pounds!
And here is the video:
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