Over the past month, the DAWN team performed three full scale hot fire tests of their 10,000 N thrust / 200,000 Ns impulse DXH-200 “Aurora” motor. The Aurora motor is a hybrid rocket motor being developed for powering the Stratos II rocket to over 50 kilometer altitude beginning 2014.
During each of these performed motor tests, the burn time was progressively increased from 5 seconds, to 10 seconds and to 15 seconds. If engine performance was consistent during each of these burns a full 20 seconds burn was to be attempted. The 5 and 10 second burn tests were completed without incidents, successfully validating the basic engine design. Unfortunately, during the 15 seconds burn a crack was formed in the wall of the combustion chamber after about 5 seconds. Inspection of the test footage suggested that the failure might have been caused by inconsistencies of the fuel grain, allowing hot gases to get into contact with the combustion chamber wall. CT scans of another grain confirmed the presence of inconsistencies in parts of the grain, suggesting a revision of the casting process is required.
Overall the DAWN team is very satisfied with the results of the tests. Critical aspects like the igniter, engine performance and test setup were all validated. Using the obtained data and a revised grain casting procedure, the team is confident that performing a full 20 second test fire will be attainable in the next series of tests. More details including footage can be found on the Project Stratos website.