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TOPIC: high power rocket?

high power rocket? 9 years 10 months ago #71

i guess this a high power rocket question so does anyone know what a single motor equivalent to 3 G77-R's is

as soon as i can ill get a pic of the rocket on the internet


THanks, John Wedding
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Re:high power rocket? 9 years 10 months ago #74

  • Aaron Head
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We can look at the certification document for the G77 (I'm assuming the single use motor and not the reload) which can be found here:

www.aerotech-rocketry.com/customersite/r...su/g77r_nar_cert.pdf

From that, we see that it has a total impulse of 102.86Ns (newton seconds), has an average thrust of 80.12N (newtons) a burn time of 1.28 seconds and a peak thrust of 100.5N

If we ignite all three motors at the same time, we just multiply the total impulse, average thrust and peak thrust by 3 but leave the burn time alone. This would give us a total impulse of 308.58Ns, an average thrust of 240.36N and a peak thrust of 301.5N. Since each letter doubles the range of the previous letter (See the NAR site for the ranges: www.nar.org/NARhpsc.html) we would have an H240. If Aerotech had a RedLine reload for the high power 29/240 case, this would be it (or very close) but that motor doesn't exist.

Now, if we were to ignite the 3 motors one after another we would triple the burn time, triple the total impulse but leave the average thrust and peak thrust alone. This would make an H77 that burns for 3.84 seconds. Again, Aerotech doesn't make such a motor.

I too like the G77 motor and so I built a rocket that used 7 G77 motors in it, all ignited on the ground. This combination made for a (7*102.86=720.02) J720 This requires a high power level 2 certification (which I have)

-Aaron
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Re:high power rocket? 9 years 10 months ago #78

  • Mark Newton
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In round numbers, an Aerotech I200W (330 N-s) or the H268R (320 N-s) are close--but not exact--matches to the 3 motors.
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