Motor selection question

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  • #41524
    Jack Matthews
    Moderator

    Got a PML Miranda (2.27 kg with motor loaded) that I launched in early May on a Cesaroni I212 Smoky Sam – looked straight and true. Thrust curve on the I212 is pretty square,,, very little difference between average and max thrust.

    Thought it might be interesting to take out the 38 mm motor adaptor and put it up on a 2g / 54 mm I100 long burn.

    However, the average thrust / weight on the I100 is only 4.41,,, and read somewhere that the minimum recommended T/W is 5. However going off the pad, the T/W is about 16,,, and based on the thrust curve, the T/W stays above 5 for the first 2.5 seconds of a 6 second burn.

    Seems like this would still be OK,,, not much different than having a little ‘kick in the coast’. But want to make sure I’m not missing anything. Any advice? Any impacts on how the ejection delay should be changed (different from what I normally figure on RockSim)?

    Thanks for any help on this…

    #56060
    Tim Thomas

    8) Baced on your numbers, you should be fine. I would fly that if I were you! 🙄 16 / 1 at liftoff should make the rocket jump off the rail. Tim Thomas L3

    #56061
    Jack Matthews
    Moderator

    Thanks, Tim… wanted an excuse to buy some 54mm hardware and start thinking about an L2 cert project anyway,,, so I’ll burn this one later this summer (if we’re not fire constrained all year) and maybe build an L2 bird over the winter.

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