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Viper Rocket Trike
Updated Jun 2021
06-30-2021: To simplify (i.e. get rid of the ignitor) and to explore different fuel grain geometries, I changed the PLA fuel core from an annular design with a 20% infill to a five point star configuration. The typical "star chamber" fuel grain geometry has a rapid rise in thrust, levels off to an even thrust, and then decreases rapidly. With this fuel grain geometry, the surface area of the PLA/KMnO4 exposed to the HTP oxidizer was increased from 57 cm2 to 90 cm2.
I used the same geometry for three seperate test. The only parameter I changed was the flow rate. Of the three test, only one ignited and that took ~11 seconds. So, it looks like it's back to the ignitor.
On the one that ignited, I did observe an even burn through the length of the fuel core. This is different from most solid and hybrid fuel grains that typically have a conical burn pattern from inlet to exit. And, if my calculations are correct, the O/F ratio was very close to theoretical.
Next month, it's back to the glow wire ignitor and more quantitative results on O/F ratio. Also, I'm adding another variable to the test.
04-08-2021: This is a repeat of the 01-27-2021 test but with a 1/4" stainless steel mist injector with a 1.0 mm diameter orifice, a 3.0 mm fuel core wall thickness, L/D=12.5 (vs 2.0 mm, L/D=10.5 in 01-27 test), and 85% HTP (vs 90%). Combustion instabilities seem to be under control due to a higher pressure drop across the injector. The net positive thrust occurs at the end of the video corresponding to the erosion of the graphite nozzle throat from 3.6 mm to 5.2 mm. The increase in throat diameter reduces chamber pressure and increases mass flow rate resulting in a net positive thrust. Net positive thrust occurred for ~2 sec at a thrust of greater than 12 N. PLA fuel core segments were infused with potassium permanganate at high temperature and pressure.
01/27/2021: This is a test of 3, 3D printed poly lactic acid (PLA) fuel core segments with 20% hexagon infill infused with potassium permanganate (KMnO4) at high pressure and temperature. Each segment is 5 cm long and 1.7 cm in diameter making the total length 15 cm. The mixing chamber is preheated for about 10 sec using a high resistance glow wire. Ninety percent hydrogen peroxide (HTP) is introduced into the fuel core under a pressure of 120 psi by opening a normally closed solenoid valve. The KMnO4 catalyzes the HTP producing the initial temperature and pressure for the thermal environment. Once the high temperature environment is established, thermal and catalytic decomposition of HTP continues.
"Simplicity is the ultimate sophistication."
- Leonardo da Vinci