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Team Members at Event: GK and PK

Finally after 3 weeks of not being able to launch due to bad weather, we were able to get out for a few launches to test the sustainer. It was less than ideal flight weather, but we had a go anyway.

We were only launching the Tachyon sustainer on this day to evaluate its performance, dynamic stability, its new flight computer and the new parachute deployment mechanism.

Flight Day Events

• The sustainer was filled with 800ml of water, pressurised to 120psi and given a 7mm nozzle to simulate the sort of flight conditions it is going to encounter when its released from the booster. Because we were launching it as a single stage, the slightly larger nozzle and less water were used to get the rocket up to speed. 1000ml and 5mm nozzle will be used for actual boosted flight.
• Soon after its first launch the rocket angled over significantly and headed over to the river. It appeared to be a little unstable during the thrust phase - most likely because of the fins being so far forward. After the thrust phase the rocket flew nice and straight.
  
  When it passed through apogee and kept heading towards the ground, and looking like we were going home early, the chute opened about 10 meters above the ground. - A close shave. The delay I set for the deploy was for 4.75 seconds, obviously a little too long. The deploy delay does not mean the time to when the chute opens, rather it is when the door latch starts opening. It takes a further .36 seconds for the packed chute to clear the door, and probably another 1 - 1.5 seconds to fully open. This timing is consistent with what we observed in the video.
• The late chute deploy actually worked in our favour for two reasons:
  1) Had it opened at normal altitude, the rocket would have drifted either into the trees or the river; and
  2) It tested the deploy mechanism, parachute attachment and parachute at high speed. This is going to be important once we fly it on the booster.
• After inspecting the rocket post landing we noticed that the payload section had moved slightly in the nosecone and that the straw and nail of the launch detect switch had separated from the PCB. A quick repair with a piece of gaffer tape fixed it up.
• On the second launch we put some washing detergent in ( we ran out of bubble bath) and set the rocket up for Jet Foaming. We also set the time delay on the flight computer to 3.75 seconds and pressurised it to 130 psi because foam produces lower thrust on take off.
  
  The rocket flew quite straight up and the parachute opened right around apogee.  The rocket drifted down range about 180 meters. Luckily the wind blew in the right direction otherwise it would have gone across the road.
• The third launch was almost identical, although the rocket again took off at a bit of an angle. The drift due to the wind under parachute was again very significant.
• We decided to call it a day when the wind started picking up and people started arriving for soccer.

Tachyon water rocket sustainer test flights

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Test Conclusions

We were very happy with the performance of the sustainer, and although there was some dynamic instability during the thrust phase, we believe this will be reduced due to the speed it will already be travelling when it is released from the booster.

The angled take-offs were likely helped by the strong wind.

The payload section will need to be secured better to prevent it from moving inside the rocket

A small change will be made to the flight software to position the servo to the correct position when it is turned on.

We are going to paint it darker colours, and put reflective stickers on it. From what we saw on the video, the rocket will be very difficult to see and track when it is boosted.

Other than that, the sustainer should be ready to go for the two stage rocket.

Flight Record