Author Topic: HTP/PLA/KMnO4 Hybrid Rocket Engine  (Read 13403 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

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