Flight test of N2O/PVC Hybrid Rocket. Feb-2013

The Goal:
Get hardware in the air in a low performance environment using my low pressure Nitrous/PVC hybrid rocket motor.

Rocket Name: Ugly-N (N for Nitrous)
A rework of Ugly-Green which flew successfully last year using an Aerotech motor.



Components

  • Modified Extreme Wildman 4" fiberglass kit
  • M900 EX Hybrid rocket motor
  • R-DAS Data acquisition system by AED Electronics
  • miniTimer-3G by Perfectflite
  • BigRedBee GPS locator and tracking
  • Kenwood TH-D7A as ground station receiver



  • Video




    Modified Extreme Wildman

    I highly recommend any of the products sold by Tim Lehr at Wildman Rocketry.

    I modified Tim's Extreme Wildman kit. The motor mount was enlarged and made from aluminum. A thread was machined into the mount to permit different diameter motors. Set screws were added to hold the motor from falling-out backwards during coast and recovery. The body was extended 12 inches to accommodate a long hybrid motor.




    Motor

    The test stand motor was modified into a flight configuration. In my opinion, one advantage of a hybrid rocket motor compared to a solid is the ability to static test and fly the same hardware.

    The only modification was removing the angle and replacing it with a straight piece. The injectors, chamber, and tank are re-used.




    Flight Data



    Plot of altitude, velocity, and acceleration.

    Unfortunately my Nitrous supplier was out of gas when I tried to refill the supply-tank. I knew before flying I didn't have enough gas for a full "M" flight. I decided to proceed anyway. Low/slow is okay on early flights.

    Zooming in to the acceleration portion of the flight data reveals the motor burned for approximately 3 seconds, which is less than half the 6.5 seconds measured on the test stand. Best guess, this was a low "L" motor.

    The rocket flew fine but recovery didn't work. Inspection of the airframe revealed the plastic rivets holding the lower section of the airframe to the upper section sheered. Normally I would assume the parachute deployed at high velocity. But looking a the velocity when ejection charges fired indicates the airspeed was low.

    My next assumption is too much Pyrodex was used. I wasn't able to ground test the charge before launch (a long story). I guessed.


    Lesson learned

    1. Recovery:

    Upgrade the plastic rivets and
    Test test test.. what else?


    2. Gas Leak:

    Although the motor was pressure tested in the shop, I did not re-test the seals on the launch pad. The jostling during transport must have loosened something. In the future I will test on the pad.




    [UP]