Author Topic: HTP/PLA/KMnO4 Hybrid Rocket Engine  (Read 15789 times)

Offline colbourne

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Re: HTP/PLA/KMnO4 Hybrid Rocket Engine
« Reply #40 on: 06/18/2022 05:24 am »
If the lift off thrust is a bit low, you could use a simple catapult to assist with take off. When ignition has started pull a cord (or use a servo) to release a hold down wire. Use a spring or rubber bungee.
I am avidly following your progress , as I was experimenting with HTP, but in a much more primitive rocket.

Offline Jerry Fisher

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Re: HTP/PLA/KMnO4 Hybrid Rocket Engine
« Reply #41 on: 07/04/2022 04:57 pm »
     This is the first launch of the Mark I Viper https://rumble.com/v1b3jsn-mk-i-viper-first-launch.html. The Mk I Viper cleared the rail guide at 2 m/sec and it was under thrust for ~ 7 seconds. I used 50 ml of unstabilized ~ 90% HTP plus 2 ml of ethanol for the oxidizer and PLA infused with KMnO4 for the fuel. Ignition occurred in ~ 0.3 seconds. The mass flow rate was about 13.29 gm/sec resulting in a total propellant mass of ~ 93.0 gm for the 7.0 seconds of thrust.

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use a simple catapult to assist with take off.

    I expected the Mk I viper to clear the rail guide at 4 m/sec. As such, I didn't have the aerodynamic control I needed to correct the trajectory.  I may have to use a catapult but I have a few things to try first. To prevent it from pitching forward, I'll shift the center of mass more in line with the thrust vector. Also, I'll increase the thrust to give me more aerodynamic control. Read all about it in the Jun EOM report.

Offline Jerry Fisher

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Re: HTP/PLA/KMnO4 Hybrid Rocket Engine
« Reply #42 on: 08/02/2022 09:10 pm »
   This month I had two flight test and one static test. All three test were an attempt to get a higher thrust. In the flight tests, I increased the throat diameter of the graphite phenolic nozzle to 6.7 mm. The first flight test blew the nozzle and failed to clear the rail guide. The second flight test cleared the rail guide and then blew out the nozzle https://rumble.com/v1eiis1-july-2022-mk-i-viper-flight-test.html. I surmised that hot gases were leaking around the o-ring seal melting the PLA thus weakening the bond between the PLA adapter and CPVC coupling.

   In the static test, I increased the flow rate to ~ 23 ml/sec but keep all other parameters the same. Once again, the nozzle blew out immediately on ignition https://rumble.com/v1ein45-class-i-rocket-engine-static-test-july-19-2022.html. Test results show a pressure spike of ~ 140 psig in the mixing chamber and a peak thrust of ~ 33 N. The high pressure spike in the mixing chamber exceeded the design limit of 100 psia. It appears the thrust is there. I just have to tame it a little. I plan to introduce a variable orifice

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Or printing a flow-restrictor as part of the combustion chamber that rapidly burns away just after ignition.

(ref: edzieba reply #28) at the end of the fuel grain to reduce the initial flow rate thus allowing the mixing chamber time to stabilize.

Offline Jerry Fisher

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Re: HTP/PLA/KMnO4 Hybrid Rocket Engine
« Reply #43 on: 09/02/2022 04:40 pm »
   I spent most of the month identifying failure modes such as nozzle blow outs, pinhole leaks, and loose connections. Having resolved the problems, I had a successful test toward the end of the month with a flow rate of ~ 23 ml/sec. The thrust reached a peak of ~ 35 N and then declined ~ 24 N. Overall performance was pretty lousy with the c* and Ceff efficiency at 74% and 66% respectively. However, my O/F ratio was ~7.5, way to high. As such, next month will be spent improving the characteristic velocity and thrust coefficient. Aug 24 test. https://rumble.com/v1idcxo-htppla-test-on-august-24-2022.html

Offline Jerry Fisher

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Re: HTP/PLA/KMnO4 Hybrid Rocket Engine
« Reply #44 on: 10/04/2022 02:31 pm »
This month I optimized the expansion ratio of the nozzle to 1.8 in an effort to improve the thrust coefficient efficiency. I had a average thrust of ~ 19 N for about 4.4 seconds https://rumble.com/v1mhl62-htpepla-test-on-09-23-2022.html. However, in my first test, there was no increase in the thrust coefficient efficiency. I plan on keeping the expansion ratio to 1.8 and adjusting the flow rate, fuel core length, and characteristic length. Also, I achieved a 3 to 4 m/sec launch velocity by launching at a 30 degree angle https://rumble.com/v1mhrj8-mk-i-viper-launch-09-20-2022.html

Offline CameronD

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Re: HTP/PLA/KMnO4 Hybrid Rocket Engine
« Reply #45 on: 10/04/2022 10:09 pm »
Jerry, aside from being focused on engine performance right now, any reason you wouldn't spin-stabilise the rocket (by simply offsetting the fins a little) to at least keep it tracking vertically after leaving the launch rail?? Might be a bit safer, that's all..

As always, keep up the great work!  I knew 'space was hard', but no idea really just how hard!!  :o

« Last Edit: 10/04/2022 10:11 pm by CameronD »
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline Jerry Fisher

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Re: HTP/PLA/KMnO4 Hybrid Rocket Engine
« Reply #46 on: 10/07/2022 12:43 pm »
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spin-stabilise the rocket

I'll give it a try. Thanks for the suggestion!

Jerry

Offline Jerry Fisher

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Re: HTP/PLA/KMnO4 Hybrid Rocket Engine
« Reply #47 on: 11/02/2022 02:33 pm »
   I used some similarity scaling parameters to increase the thrust of the HTPE/PLA hybrid rocket engine. The objective is to increase launch velocity and thus aerodynamic control of the Mk I Viper rocket glider. The three scaling parameters I looked at were initial gas flux, initial surface area flux, and length to diameter ratio. I designed and printed a higher flux fuel grain and inserted a variable PLA flow restrictor at the end of the fuel core. My average thrust went from ~19 N to ~23 N and overall performance was on par with previous test (video link: https://rumble.com/v1r3ico-10262022-plahtpe-hybrid-rocket-engine-test.html).

Offline Jerry Fisher

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Re: HTP/PLA/KMnO4 Hybrid Rocket Engine
« Reply #48 on: 12/05/2022 04:25 pm »
I upgraded my rocket engine test stand and ran two tests on the HF fuel core, one of which was on the new test stand. On the second test, I increased the HTPE load to 62.4 ml. Ignition occurred in ~ 0.8 seconds and lasted ~ 5.0 seconds. The thrust was ~ 24 N and the c* efficiency was ~ 91%. Total propellant load was ~ 105 gm. https://rumble.com/v1yzsx4-new-rocket-engine-test-stand.html

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