Aerotech D9 RMS 24/40 reload, slow thrust curve?

Discussion in 'Propulsion' started by mbeels, Mar 18, 2019.

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  1. Mar 18, 2019 #1

    mbeels

    mbeels

    mbeels

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    Hello,

    I was running some simulations and noticed that with the Aerotech D9 (white lightning) the velocity off the launch rod was surprisingly slow. I looked at the thrust curve, and it comes up to power really slowly! For the first 0.25 seconds, it has less thrust than an Estes A8 motor!

    I know that the white lighting is not a fast burn motor, but other motors using the white lightning propellant come up to thrust much faster (like the E18 reload).

    Does anyone have real world experience with this D9 motor? How well does the thrust curve on thrustcurve.org match reality?

    I wonder if such slow lift offs are the case with this motor.
     
  2. Mar 18, 2019 #2

    gfunk

    gfunk

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    FWIW, here's video of my D9W from this Saturday in a pretty stock Estes Goblin, ~82g dry weight. OR said ~40mph off the rod. Awesome little motor, more impressive than BP, and always a crowd pleaser. I've burned quite a few, but only in Goblins, nothing bigger.
     
  3. Mar 18, 2019 #3

    BEC

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    Funny this should come up. I saw that thrust curve and thought “I’m not going to order any more of those”. Then, yesterday, I put an Estes Eliminator up to 878 feet on a D9-7. It was a gorgeous straight boost and the delay was pretty good (AltimeterThree said it was 5.65s - a little early). My biggest impression of the boost was “wow, that was loud!”.

    So in the right model they should be fine. The Eliminator, even with an AltimeterThree aboard, is still pretty light - less than 5 ounces plus motor.

    The Goblin would be even more fun.....

    I flew an Estes BT-80-based V2 with one (shorter delay) at a prior launch at the same field and it did look as if it didn’t quite get going fast enough off the rod. That model works fine on Estes D12-5s.
     
  4. Mar 18, 2019 #4

    mbeels

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    Thanks for the video, nice boost! And what a gorgeous launch site....

    That was my first thought! I may give it a shot on a lighter model, I like the White Lightning.
     
  5. Mar 18, 2019 #5

    Andrew_ASC

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    If your worried about off the rod velocity try the D15T reload. I’ve flown the E18W and D15T successfully.
     
  6. Mar 18, 2019 #6

    mbeels

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    Yup, I just ordered both of those! Plus the 12 second delay kit for the E18W, and a F39.
     
  7. Mar 20, 2019 #7

    BSNW

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    The propellant grain in the D9 is small....leaving a lot of empty space inside your motor casing....it takes time for it to come up to pressure...But on the right rocket....it is glorious! It is a fine motor! I have flown a ton of them!
    Andrew
     
  8. Mar 20, 2019 #8

    mbeels

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    Thanks for the reply, that explanation makes a lot of sense. The slow ramp up of thrust would be fun to watch in a light rocket. I'll give it a try!
     
  9. Mar 20, 2019 #9

    swatkat

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    Agreed, it does come up to pressure slowly. It is a great motor for the Mercury Redstone (with larger MMT), I've not used it in anything heavier than that (~5oz). It still looked plenty quick off the pad, but it's definitely slower than a D12 Estes.
     
  10. Mar 20, 2019 #10

    jd2cylman

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    I used it in my first Silver Comet. VERY slow off the rod (6ft). But thanks to the large swept fins (and light wind), the flight was decent. Still a cool motor. Not as rude as the E18 :cool:
     
  11. Mar 20, 2019 #11

    mbeels

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    I'm curious, do you remember how much your Silver Comet weighed?

    Yeah, it is surprising to me how different the thrust curves are between the D7 and E18, despite both having the same propellant. The empty space in the motor chamber must really make a big difference!
     

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