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These motors are tested on "Henrietta" our yellow 54mm and 98mm test stand.

Discussion

Xaphan Blue proved to be a fairly poor performing propellant. This was shown by the successful static fire at the beginning of the 2017-2018 year, when a 98mm 4G motor delivered an ISP of 170s. The relatively low impulse can be attributed to poor density due to insufficient mixing time and faulty casting procedures, but the ISP is due to the formula itself. The formula had low solids loading and contained a number of compounds that were supposed to produce a blue flame. In general and in this case, additives that produce effects subtract from "the good stuff" (AP and Al), so their inclusion should only be considered if performance or efficiency is not a goal. In an ironic turn of events, when the motor was burning hot enough to consume the aluminum in the propellant, the bright white flame that it produced was enough to mask the blue flame caused by the additives. This effect is visible in the images above. The lesson to be learned here is that if a specific flame color is desired, metal content should be low to allow the effect to be displayed. This will result in performance even lower than Xaphan Blue, which can be offset somewhat by using a typical solids loading in the 80-82% range. Performance and effects are nearly always a trade off unless very careful design is applied.