|Date:||1st April 2023|
|Conditions:||light wind ~5-10km/h, 23C mostly sunny|
|Members:||GK, PK and PaulK|
The rocket setup for Tajfun 2 was straight forward, and we decided to use the larger 60" chute from Rocketman we are using for Horizon. Originally we planned to use one of our old umbrella parachutes, but because this is a much heavier rocket, we didn't want to risk shredding that chute since it was designed as an umbrella, not a parachute. This also meant that the rocket would come down slower, and we would get more of our money's worth from the parachute.
We pressurised the rocket to 300psi, but when we turned off the air, the pressure gauge only read about 200psi. When the air was turned on again the pressure quickly jumped to 400psi before again settling at something over 200psi, so we continued pressurising. We did this a few times as the pressure climbed. In the end we decided to keep the air open and just launch.
What we think happened is that the air hose has quite a restriction in it and is connected to a large volume at the other end. So when we turn the air on, the pressure climbs quickly in the hose and that is what we are seeing at the pressure gauge at our end, while the other end of the hose is slowly filling the large volume. Essentially there is a pressure gradient across the length of the hose. One way to get around it is to either remove any constrictions in the hose or fill slower so everything has a chance to equalize. There may even be some water in the launch tube that is creating this back pressure.
Here are some photos from the set-up.
We donít know the final launch pressure exactly but it is likely to be around 270psi range. The rocket was expected to go to 786 feet, but only achieved 667 feet. Running the simulator for that altitude and varying the pressure, it also predicts a pressure of 270psi was present. Originally the time to apogee was predicted at 7.5seconds. I had set the delay to 7 seconds because I wanted the parachute to start deploying on the way up as we knew from the last test it could take a couple of seconds to fully inflate, and I didnít want that to happen on the way down. As it turned out the parachute deployed right around apogee and the rocket drifted down to a safe landing in the mud.
The rocket survived well without any damage, and will be ready to fly on J motor in August. Mud got pushed all the way up the nozzle so we had to remove it completely and wash out the rocket. Here are some highlight photos from the flight.
Paul ended up flying his Pod3 rocket on a F23-4 and it had a really good flight and you could even hear the whistles on the way up. He then flew his Equinox rocket on a E12-6 and it too had a really good flight and both recovered well.
We set the Nova rocket up again, as it had a couple of good flights last
time. This time I re-printed the mount and payload bay in a stronger PLA+
hoping that it wouldnít get damaged when it landed. We launched the rocket
at 300psi, the rocket had a great flight on the way up and again the
deployment mechanism failed to deploy the parachute. I definitely had it
armed as I verified it twice. There must be something fundamental that is
going on with this design why it keeps failing. The airflow over the rocket
is probably keeping the door pinned. We looked at the damaged nosecone, it looked
like the servo was in the open position, but it also may have been forced
into that position as a result of the impact. In any case the pressure
chamber survived again thanks to the soft earth, and we may be able to save some of the electronics.
We'll try to re-design the deployment mechanism and try again.
Overall we were happy with the weekend. Here are some highlight photos from the Nova launch.