ASK 't Harde, 2 October, 2009 - Thursday 1 October during NLD30 several motor tests were done. These were motor tests CMT0901-CMT0903 (CMT0904 was done Friday 2 October). These test motors have our Kalinitrox as propellant and have just a single Bates-grain. The flight motor will have six grains. CMT0901-CMT0903 were all similar in composition, but each had a slightly smaller throat diameter. The throats were respectively 4.2mm, 3.9mm and 3.7mm. This could be seen in the results of the tests, as the motor pressure steadily rose.
The next day we woke up with very rainy weather. After preparations were done the last motor test was done. CMT0904 was a rerun of yesterdays CMT0903, thus having the same throat. After a little more than 3 seconds the safety membrane gave way. This means that the pressure in to motor had reached a value of more than 8000 kPa (80 Bar) and to safe the equipment the brass safety membrane breaks, which creates a second, much wider throat that lowers the pressure in the motor. Later is was discovered the throat was not cleaned after the last test and thus probably was clogged up with residue from the third test.