Weird Astra III flight

Discussion in 'Low Power Rocketry (LPR)' started by n3tjm, Jan 31, 2020.

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  1. Jan 31, 2020 #1

    n3tjm

    n3tjm

    n3tjm

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    Hi All. Today I flew a Quest Astra III with a A3-4 Q-jet motor. This was a recommended motor, but I was curious how well this rocket would fly on that motor. I would think that the motor would be too weak and too long of a delay for this rocket. Well, the rocket took off and veered off course and hit the gutter on the other side of the house. Gutter is fine, the rocket took the damage. Watching the video, lift off seemed to be fine. Quick and straight but dramatically changed course near burn out. At this point, the 4 sec delay was guaranteed to be to long. What do you guys think caused it to veer off course? Do you think the A3-4 would of been fine if it stayed straight and true? I got 1 A3-4 left, but I am reluctant to try that again.



    The Astra III starter set comes with B4-4 Q-jets, so as you can see that was a much better choice.
     
  2. Feb 3, 2020 #2

    Back_at_it

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    Was a fin seriously bent, Nose cone not seated or something else wrong with the rocket.

    I've only seen a flight like that a few times.

    - Rocket damaged before flight. Nose cone not seated, Fins bent, broken or missing.
    - Nose cone too loose and came off in flight.
    - Motor burned through the side wall of the casing.
    - Rocket hung up on rod and did not have enough speed to stay stable when clearing the rod.
    - Motor too weak for weight of the rocket.
    - Body tube collapses during flight. Happened on the 3rd flight of Mini Mean Machine on a B6-4. Yes i built with a 18mm mount. Motor/wind/whatever was too much for the body tube
     
    Last edited: Feb 3, 2020
  3. Feb 3, 2020 #3

    kuririn

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    Recommended motors include the A6-4 black powder motor. Don't think the A3-4 is a good substitute. Max. lift off weight is listed as 28g. for that motor. The Astra III is listed as 4 oz. weight (113 g.)
    So probably not enough speed coming off the launch rod to fly stable.
     
  4. Feb 4, 2020 #4

    shreadvector

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    Did you install the igniter using the small hollow heat shrink tube inserted NEXT TO the igniter so that it could vent during ignition and then spit out cleanly one ignited or did you tape the igniter to the motor so that it would be carried up into the air and deflect the flight (which is very bad)?
     
  5. Feb 4, 2020 #5

    n3tjm

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    Yesterday I flew the Astra III again on the remaining A3-4. This time the flight was picture perfect. Straight up with ejection shortly after apogee. I used the red tube on the first flight. the second flight i used a small piece of tape . The problem wasn't the wire pulling on the rocket. It could probability something clogged the nozzle partially which cause the thrust to vector.
     
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  6. Feb 4, 2020 #6

    Back_at_it

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    My guess is that something happened with the nosecone right after take off. I've seen flights where they are too loose and actually come out of the tube on takeoff (Hang around scouts long enough and you'll see just about everything go wrong) or there was an issue with the nozzle of the motor.

    Not sure where Quest gets the 4oz weight from. That would make it heavier than a big bertha. I've weighted mine and it's right at 1.3oz empty and I tend to build on the heavy side. Mine has flown on everything from 1/2A6-2, A10-3T (with adapter) up to C6-7. Never had a bad flight. Had some sketchy recoveries but no bad flights.
     
  7. Feb 4, 2020 #7

    kuririn

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    1.3 oz. is 36.9 grams. So approx. 32% over max. recommended lift off weight for that motor, per Quest website.
    Not saying you cannot get a straight flight, but it may be marginal.
    Add a slight breeze, and it could go south very fast.
     
  8. Feb 4, 2020 #8

    n3tjm

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    The nosecone was loose so i snugged it in with tape. So it wasn't drag separation.
     
  9. Feb 5, 2020 #9

    BEC

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    I don't understand that max liftoff weight listing anyway. They have the same recommendation for A3-6 (where it makes more sense). Estes quotes a 2 ounce max liftoff weight for their A3-4 (A3-4T). For whatever that's worth.
     
  10. Feb 5, 2020 #10

    GlenP

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    Seems like it was a windy day. You can hear it a little in the mic, but more telling is how much the smoke trail gets blown sideways, even more just beyond the launch rod than on the ground. You may have had a better trajectory by pointing the launch rod slightly into the wind to compensate. But, hard to tell in the video, looks like the rocket turned sideways from the wind in the direction away from the camera, rather than with the wind directed towards the left. That doesn't make sense to me. But the winds can change direction in that first 100' or so near the ground.
     
  11. Feb 7, 2020 #11

    n3tjm

    n3tjm

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    From my perspective, i hardly noticed any wind. The second A3-4 flight was actually felt a breeze.
     

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