Each flight log entry usually represents a launch or test day, and describes the events that took place.
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Location: Ophir, NSW. (launch site #5)
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Conditions: Very hot, clear skies, moderate blustery wind.

Rockets: (click the name for rocket details)

Team Members at Launch Event: PK, GK, DK, AK, Paul K and John K.

Number of launches: 9

Since we were going camping this week we thought we would bring along three of our new big rockets. We knew the campground was near very large open fields, perfect for testing new rockets. This update covers two days as day one had only one actual launch.

As we have run out of kids nicknames for the rocket names, we have switched over to using the names of subatomic particles.

Flight Day Events - Part 1

• We arrived at the launch site and the weather was looking great with clear skies, until we stepped out of our air-conditioned cars. The temperature was nearing 40 degrees C. Without shade, setting up a rocket launch site is tough going. We set up our new untested Polaron rocket on the launch pad and one thing became obvious that the launcher was inadequate to handle such a large rocket. One of us was going to have to hold it as it launched!
• Drawing the short straw, I was holding the rocket against the wind (Do not do this at home) as it was filling up towards 130psi. All of a sudden the top segment started leaning over and the top most joint started to hiss. So I let go of the rocket and jumped aside thinking that failure was imminent, but luckily the air was cut off quickly and all the air escaped. The wind blew the rocket over with the launcher. I was glad most of the pressure had escaped by the time the rocket hit the ground as it may have taken off. We were going to remove the faulty bottle segment, but we noticed that the fins were quite bent and would also need repairs. Fixing both in the heat with virtually no shade made that a less attractive option.
  
  Later upon inspection, we found the failed bottle was quite distorted and the coupling hole had enlarged significantly (see photo on left).
• So instead we set up J4 II and started pressurising it. Being about the same length as Polaron, we were going to have to hold it again during launch. Unfortunately J4 also suffered a minor leak at one of the segments, and with the heat again causing us to postpone any in-the-field repairs.
• We were deciding whether we should continue or pack up for the day, because a fairly blustery wind was also picking up. We knew that setting up Acceleron would take about 15 minutes, but we persisted and managed to set it up for launch. This was the first time the new rocket was going to be fired from the new launcher, so we really didn't know what to expect. Dad had the brilliant idea of adding food colouring to each of the booster segments, to make a more colourful takeoff.
  
  After setting it up we were ready for blastoff at a test pressure of 100psi. A short wait for the wind to die down and we launched. It was a great takeoff and made plenty of noise. The rocket pitched over a little but flew quite straight. The parachute opened perhaps a little early, but you could clearly see a cloud of spray out of the dummy payload section as the chute opened, which worked as we designed it (see design and development below).
  
  All in all for the first launch it was a really good flight. The 900mm diameter parachute worked well to slow the rocket down to prevent any serious damage on landing.
  
  
  Acceleron cluster water rocket
  
  
  (If the video does not play, try downloading the latest Flash player from Macromedia)
• After we set it up on the launch pad again, we noticed that two of the nozzles were leaking while filling with water. We discovered that the previous launch flushed the O-rings out of their seat grooves. Having already driven for almost 5 hours to get to the launch site and almost an hour in the sun we were tired, and by this time we were seriously in need of shade so we packed up and continued to our camp site that we still had to set up. There was always tomorrow.

Flight Day Events - Part 2

• The next day we decided to launch Acceleron at the campsite. One major problem with the location was that it was in a valley surrounded by very tall trees. We were going to perform low altitude launches just to check things out.
• We removed the parachute so that it would not get snagged in a tree, filled each booster segment with around 2 L of water and filled it to 80 psi. It was a beautiful launch and the rocket slowly arced over the tallest tree and crashed through another tree to the ground. You could see that the rocket was quite stable through most of the flight until the water emptied in the dummy payload and then the rocket's heavier tail took over and the rocket flew sideways on the way down which helped it prevent serious damage.
• We set it up again, but this time we tied a thin 20 m string to it so that should it get caught in a tree we would be able to pull it down. We only filled it to 50 psi and about 1.25L fill per segment. The rocket again flew nice and stable, although be it to lower altitude with the lower pressure. After the water emptied it flew sideways again, but without the parachute it landed pretty hard and bent the support frame and broke off a fin. Something that is easily fixed, but it did not fly again on the day.
• We then also launched a new 1.5 L rocket at 120 psi a few times, and then spent a bit of time recovering it from the river and the surrounding hills. It does not have a recovery system and just uses a soft nosecone for landing.

Flight Record

Design and Development

We have been continuing the development of the cluster rocket (Acceleron). Here are some technical details and some of the design decisions we made along the way.

The Rocket

The final rocket design intends to be a two stage rocket. The cluster under development described here is just the booster. The booster consists of 3 segments with 4.25 L capacity each giving a total volume of 12.75 L. Each segment consists of two bottles a 2L and a 2.25L bottle joined at the base with a Robinson coupling. Eventually each segment will be either 3 or 4 bottles in length providing up to around 27.5 Liters.

The segments are attached to a central aluminium tube for stiffness, and the central tube also supports the second stage.

In these first experimental flights the booster carries a dummy payload to simulate the second stage weight, and also to provide some stability for the rocket.

The dummy payload consists of a vessel containing about 600-700ml of water for weight, but the dummy payload is designed to passively empty the water when the rocket flips over and falls under parachute. We didn't want the booster to land with such a heavy weight attached.

On top of this vessel is our typical parachute arrangement that uses the nosecone-off-at-apogee technique. We specifically made a new parachute for this rocket that is 900mm in diameter. Eventually the parachute will be stowed on the booster but for these flights we are keeping it simple.

Each booster nozzle is 8.8mm in diameter.

Including the 600ml of water in the dummy payload the "dry" weight of the rocket is ~1.6 Kg. The total weight at launch is 5.35 Kg.

The Launcher

The custom nozzles of the booster fit into the custom seats in the launcher that contain an O-ring for sealing the nozzle. For simplifying the rocket design and hence reducing its weight, we chose not to provide the necessary pressure equalisation between each segment on board the rocket, instead the launcher provides the equalisation.

In the center of each seat is a small tube that carries the air above the surface of the water in each segment. Since all three tubes are connected to the same manifold the air pressure is allowed to equalize without transferring any of the water between the segments. (as happened in the first test) Each of these fill tubes also acts as small launch tube that assists with the launch.

Because of its eventual size, this rocket is also our first rocket that is placed dry onto the launch pad.

The rocket is filled with water simply by opening the top bottle cap of each segment and pouring the water in. Because the top bottle has its base at the bottom, the base lobes, could collect water and essentially provide dead weight since they are below the coupling, so we fill the lower bottle using a long tube and funnel.

Each of the seats does not hold the segment down, the nozzles are free to move out of each seat. The entire cluster is held down by the central pipe and a flanged aluminium support frame connecting each of the segments. An aluminium fitting attached to the support frame was made that fits into a spear gun release mechanism. This centralised release mechanism simplified the launcher and allows all of the segments to be released at exactly the same time.

The launcher also has two adjustable guide rails that help the cluster launch vertically.

Notes to Self

• Bring gloves when handling food colouring
• There is no excuse for not having spare batteries.