N2O/Ethanol bipropellant rocket engine

[Johansson]

Good input there Carl, video taping the gauge is a sound way to get a reading in case the ignition keeps messing up the data logger.

I am thinking about changing the fuel from methanol to E85 for the next run, mostly because it is available at almost every pump station while methanol is almost impossible for me to buy on short notice. It will also be easier to get the exhaust plume on tape since it will be more yellow than with methanol.

I´ll have to make a smaller fuel jet because E85 contains more energy than methanol for a given volume, I had already planned to make an injector with exchangable metering jets to be able to field tune the engine so it should be easy to change back to methanol later in case I want to try it again.

The engine will hopefully be ready for a new test shortly after new years eve, I have a couple of weeks to get the mods done before we go on a christmas trip to my parents in law.

Cheers!
/Anders

[Johansson]

A short update on what little progress I have made since last time, I disassembled the engine and fitted a drain plug on the bottom so I can empty the system of coolant without having to turn the entire rig upside down.



A better ignition probe is badly needed since the speaker cable probe caught fire and were spat out the moment the propellants started to flow, I will make a new probe from two insulated inconel rods that sits on a hinged arm that is weighted so it will tip backwards once the engine is lit and pull the inconel probe out of the nozzle.



I am aiming at a new test run a week or so after new years eve, very interesting to see how the engine will perform after the mods.

Cheers!
/Anders

[sven]

Keep up good work Anders, hope you mods gonna give nice results:)

Sven

[Johansson]

Thanks Sven!

I got some more work done on the rocket engine today, not easy to find time for it between stomach flues, broke down cars that needs repairing and christmas decorations...



First I took on the job of making a better way of filling the nitrous oxide, before I tried to gravity fill the race bottle but that didn´t work very well so now I will try the more commonly used way of bleeding gasseous NOX out of the race tank while filling and use the pressure drop to pump the liquid between the tanks.



There you can see the bleed jet, to avoid the problem that the bottle can overfill I fitted a siphon tube to the coupling on the top of the tank so liquid NOX will start blowing out of the vent when I have roughly 1000cc of head space left in the tank.



This will eliminate the need of precision weighing the fill tank since there is no way the race tank can overfill, we´ll still weigh the tank before and after just to get a figure for any Isp calculations but we won´t have to monitor the scale during the entire filling phase.



To avoid any couplings downstream the NOX tank I will simply remove the pipe between the "throttle" valve and the engine and fit a short fill tube so I can fill the NOX through the valve and up into the tank.



Finally I started to build some sort of hinged ignition contraption, I´ll get back to you later when I know if it will work or not...

Cheers!
/Anders

[Johansson]

Before we went to my parents place for new years eve I got some more work done on the rocket engine, there is some work left that I have to do when the engine is fitted to the test rig.



I made a special coupling so I could fill the nitrous oxide through the throttle valve, this should make filling the run tank much easier and there is no need for any extra fittings on the nitrous lines.



Then I assembled the engine again, I added some teflon tape under some of the o-rings to make the fit a bit tighter where coolant water leaked a bit during the last test.



The engine in place again, there is some work left to do on the ignition and I have to dig through my pockets for some cash for a couple of kgs of nitrous oxide before I can set a date for the next test.

Cheers!
/Anders

[stevep]

Great progress, Anders. Clever idea about the teflon tape under the o-rings. I'll have to try that next time I cut the grooves a bit too deep. Nice job on the siphon tube, too.

--Steve

[Johansson]

Thanks Steve.

I have decided not to run this engine at Speed Weekend this year since it is just too dangerous for the crowd and ourselves at this point, the engine needs much more testing before I can consider it safe enough to propel anything with it not to mention to let any bystanders near. It might very well end up as a test bench engine in the end.

Funding is also a bit low at the moment since my feancee is on maternity leave with our youngest daughter, and since the turbine bike has waaaay higher priority than the rocket engine I will have to keep it on a shoe string budget for now.

I am planning a new test run of the rocket engine with the mods I´ve made this spring when the Speed Weekend race is over and things have settled back to normal (we´re still going to race the jet kick so all focus is on getting the kick and camp together in time) so don´t think I have abandoned the rocket engine.

Cheers!
/Anders

[stevep]

Hey Anders,

I understand about the priorities...I am now swamped for the rest of this month myself.

--Steve