On May 27, Cal Poly Space Systems conducted the first successful 2/3 duration test fire of the HM-7 Heavy hybrid motor. Using data from this test, we were able to build a thrust curve:
As expected with a 2/3 duration test fire, thrust drops at around ten seconds as nitrous oxide (our oxidizer) mixes with nitrogen (our pressurant). Stable combustion occurs for about 10 seconds, and is followed by approximately 5 seconds of unstable combustion. Additionally, the video (final phase of test begins at 23:45) provides a qualitative confirmation to our quantitative data. Average thrust over the entire test was about 520 pounds. We are very pleased with the results of this test!
This test fire is a significant step forward in our progress to IREC, and serves as a complement to our previous short duration test fire. The 2/3 duration test also demonstrates that our new HM-7 Heavy design can withstand temperatures and pressures associated with sustained stable combustion. We hope to conduct at least one more test fire before the final trip to IREC.