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    Flight day 4 - Nozzle issues

    Date: 14.11.2009 (11:00 - 12:45)

    Weather conditions: overcast, 10C, light winds

    When analyzing the data of flight day 3 we discovered that the third launch which was completely unstable had been done with a nozzle of  type "B". This particular nozzle is somewhat heavier than the nozzles of type "A". With the next couple of flights we wanted to learn wheater the nozzle was the root cause of the instability.

    Furthermore we wanted to try a new launch site near "Heuberger Tor".

    Nozzle type "A": The bottle cap has a hole where the nozzle fits in.

    Nozzle type "B": 1" Threaded Tap Connector in which the bottle cap has been glued with epoxy.

    Launch #1 with a nozzle of type "A" didn't show the unstable behavior we had seen before. Antares Ia went to the west in a slight arc. The parachute deployed just at apogee. After 21 seconds Antares Ia touched the ground approx. 40 meters west of the launch pad. The recorded height was 74.8 meters with a launch pressure of 8 bar and 900 ml of water.

    Launch #1: Antares Ia was aligned perfectly vertical. It flew in a slight arc to the west.

    Altimeter data of launch #1

    Launch #2 was done with the same nozzle and again didn't show any unstable behavior. In order to gain more heigth we aligned Antares Ia slightly to the east. But immediately after launch it went to the west again. However, apogee was higher this time. After 28 seconds Antares Ia touched the ground only a few meters west of the launch pad. The recorded height was 93.4 meters with a launch pressure of 9 bar and 950 ml of water.

    Launch #2: Antares Ia was aligned slightly to the east. It took off more vertically but still went to the west. The measure resulted in a significantly higher apogee.

    Altimeter data of launch #2

    We refrained from doing a launch with a nozzle of type "B" because we were worried about the integrity of Antares Ia. So we don't have the evidence that  nozzles of type "B" cause the instability. But we have shown that nozzles of type "A" can be used without an issue.

    Lessons learned:
    Nozzles of type "A" are suitable for launching Antares Ia. Nozzles of type "B" should not be used in the future any more.
    Antares Ia has the tendency to fly in an arc, always to the same direction.
    The new launch site is less crowded than "Oesterberg" and a good choice for medium size rockets.

    Next steps:
    Investigate the root cause of the not optimal trajectory of Antares Ia.