This weekend, I ran a 480 load of the new blue at a lower pressure (400 psi instead of ~600 like last time). The result:

Aerotech I357

TDK I300

OH YEAH. The one drawback was that this motor was not nearly as loud and generally “nasty” sounding as the higher pressure one. This was down at a Kn of 180, and operation was completely smooth, coming up to pressure and shutting down cleanly. I like this a lot. I have a 54/1050 and two 38/640s of this stuff ready to go next…

It seems that Strontium Carbonate-based red motors get a bit of a bad rap in the community. The king of these formulations is Pat Gordzelik’s Polish Rojo family of propellants. I originally shied away from making reds, as I believed PR/SPR to be “wimpy” propellants that made a weak red flame, and that real men used Strontium Nitrate to make red motors. But Strontium Nitrate has its problems — it’s highly hygroscopic and needs to be dried and screened before use, and the grains must be kept sealed tightly before flight. I have a few old Kosdon East “Red Rhino” motors that are nitrate based, and though they give a BRILLIANT red flame and a delightful low-thrust, long-burn profile, they are immensely difficult to light due to their age and the amount of moisture collected by the hydrophilic Nitrate groups.

So, I decided to try out Polish Rojo:

Further details on the motor after the jump: (more…)