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Date:  13th December 2009 (8am - 1:00 pm)
Location: Doonside, NSW, Australia
Conditions:  Warm 32C. Light winds, clear, strong wind in afternoon.
Team Members at Event: PK, GK, Paul K and John K.

This week we wanted to test fly the new splices before fitting them to Acceleron V since we didn't know how they would behave under real world conditions. Doing a hydro test only gives you a part of the story. Acceleration forces during take-off, parachute deployment and landing all can affect the spliced pairs. We also wanted to see how temperature may affect them on a hot day with the additional heating due to air compression. Lastly we wanted to see how the spliced-pairs behave during rapid depressurisation such as during a launch.

We built a Polaron class rocket (Polaron VII) using all 4 spliced-pairs giving a total volume of around 12.5L. The fins were taped to the rocket body since they were only temporary for the test flights. Thin drinking straws were used to improve the aerodynamics on the leading edge of the fins. All up about 24 two-litre bottles were used to build this rocket.

Flight day report

• We arrived around 8am at the launch site. The conditions were almost perfect with very little wind and clear skies.
• We set the Polaron VII rocket up on the pad. When we use a launch tube we don't bother with the guide rails, since the launch tube does a pretty good job of supporting the rocket.
• We pressurised it to 130psi and launched it with a 15mm nozzle. The rocket went up very straight and fast and reached 494' (150m). The parachute opened right on time and the rocket landed well.
• Next up was Paul's 2 stage pyro rocket. The first stage ignited well and the flight was nice and stable, but during staging the second stage failed to light and the rocket nosedived into the hard ground. Quite a bit of damage was done to the rocket, but I believe it is fixable so we will have a go at doing that over Christmas.
• The third flight was again Polaron VII launched at identical pressure. This time the rocket went to 506' (154m). Both the parachute deployment and landing were good and there was no damage. Not wanting to risk damaging these spliced pairs on further flights we retired the rocket for the day.
  
  The one thing we noticed that some of the glass strapping tape had a few small buckles in it. This was most likely caused during pressurisation and the bottles and tape stretching somewhat. We'll remove the stretched tape and re-tape them. Not all bottles exhibited this.
• For the fourth flight we wanted to launch a flour rocket since we hadn't launched one at Doonside before. I fixed up an old launcher the night before for this flight because I did not want to end up with flour sludge all over our regular launcher. It is not a good idea to mix flour and water rockets on the same launcher. Unfortunately the launcher wasn't properly tested, and sprung a leak somewhere around 100psi. We launched the rocket (Axion III) anyway, though it did not reach a great height, but high enough to deploy the parachute and land well. 
• For the next flight we replaced the medium launcher's launch tube with the regular 9mm release head and added the guide rails. We launched Axion V at 130 psi with foam. It had a very nice slow take off but thankfully it went vertical. We didn't fly an altimeter on this flight so we don't know how high it went. The on board video gave us a good view of the shadow of the foam trail.
• The last launch of the day was quite eventful. We set up Axion V again with foam, and as we started filling it, John, who was on the end of the release string and in his exuberant-fast-approaching-Christmas state of mind gave the string a bit of a tug. The rocket went up about a foot still in the launcher and sprayed foam everywhere. Luckily there wasn't enough pressure for the rocket to clear the launcher and so no damage was done.
  
  We refilled the rocket and set it up again. This time as we almost reached launch pressure I noticed the bundled parachute partly sticking out of the payload bay. This seemed a little odd, but then I realized the chute had actually deployed and the guide rail was keeping it from falling down. I ran over and re-secured the door and re-armed the computer. It may have triggered either due to the vibration of filling, or due to the buffeting of the strong wind which had picked up by then. I don't want to think about what would have happened if had we launched it with the parachute deployed! :)
  
  All fixed, we launched the rocket, and despite the long guide rails the now strong wind (30km/h+) caused the rocket to pitch over and accelerate down range. The rocket may have reached perhaps 150 feet in altitude but flew horizontally for a lot of the flight. Google Earth tells us that it landed 260m (850') from the launch pad.
  
  Although the parachute opened about 5 seconds after launch as it was supposed to, the rocket had a high horizontal velocity and the sudden chute opening caused the rocket to buckle at the parachute attachment point. The nylon shroud lines held and the rocket landed safely. One bottle was buckled which can be easily replaced. I wonder how much further the rocket would have flown had the parachute not opened?

All in all it was a great launch day and we can now start re-building Acceleron V with the new spliced-pairs. There will also be more time to work on rockets over the Christmas break.

Update: Well having had a close look at the flour rocket tonight I noticed flour sprayed on the inside of the the inter-bottle sleeve. On closer inspection the o-ring on the Tornado tube had popped out and leaked. It appears the launcher was fine. Closer inspection revealed that the bottle neck and thread had distorted. This is most likely to have been caused by heat. Upon pulling apart the Polaron rocket I noticed two threads on two of the bottles were also slightly distorted. It was quite a hot day, with direct sun on the couplings so I am not surprised that it happened. I did not have these couplings protected, but from now on they all will be. (See image)

We have attempted to repair these thread distortions before and it is possible to fix them by carefully heating the thread with a heat gun and then shoving a mandrel (broom stick) inside the neck.

What's more, I found moisture on the inside of one of the inter-bottle sleeves on the Polaron rocket. Having pulled the rocket apart I was quite amazed and embarrassed at the same time to find one of the tornado coupling o-rings missing altogether. Despite that the rocket still managed to fully pressurise and fly.

The video is also now available on Vimeo here.

Flight Details