Ignition Tests

After successfully testing our injector, we decided to move on to ignition trials. Igniting isopropyl alcohol without a nozzle proved trivial, so after a few upgrades, we tested the system with its designated fuel and oxidizer, methanol and hydrogen peroxide. However, we initially overlooked the role of atmospheric oxygen, leading to an oxidizer-rich mixture. While ignition was achieved, the reaction was inefficient.

To address this, we installed a nozzle to better simulate a combustion chamber devoid of external oxygen. Given the small scale of our test setup, we opted for a throatless nozzle. The first ignition attempt failed because our chosen igniter, a birthday cake fountain, lacked the necessary energy to sustain combustion. We then experimented with magnesium torches, which can burn underwater, and after three tests, we successfully achieved ignition. However, without a throat, the chemical reaction was effectively blown out of the nozzle, preventing sustained combustion. A proper throat would allow pressure and temperature to build up in the chamber, maintaining the reaction.

To resolve this, we are transitioning to a larger engine designed to produce 5 kN of thrust. Scaling up should simplify ignition and combustion since larger rocket engines generally perform more reliably than smaller ones.

One challenge we encountered was nozzle leakage at the injector mounting point. This was somewhat expected since the nozzle and ignition tests were added later in development. Unfortunately, this led to a small fire around the engine, which was quickly extinguished, though not before damaging our prototype test rig’s electronics.

On the control side, our FADEC and SCADA systems performed reliably with the latest design iterations. However, the low-cost pressure and temperature sensors continued to be problematic, leading us to switch to higher-quality alternatives for more reliable readings. Up to this point, the system has been manually controlled, but we are now implementing an autonomous test routine, which will be validated on the current setup before moving to the larger engine.

Additionally, our test rig has shown various shortcomings that need addressing. We plan to improve its design before presenting the final system at this year’s MIDEM conference.