Each flight log entry usually represents a launch or test day, and describes the events that took place.
Click on an image to view a larger image, and click the browser's BACK button to return back to the page.

Location: Denzil Joyce Oval. (launch site #4)

Conditions: Warm, calm, partly cloudy.

Rockets: (click the name for rocket details)

Team Members at Launch Event: PK, GK, HK, AK, IK, JK, John K and Paul K.

Number of launches: 4 (part 1), 4 (part 2)

On this day we conducted a couple of new tests and experiments. The first was the test of our new launcher. In testing the new launcher we launched a couple of new rockets as well. The new launcher is discussed in detail in the Design and Development section below.

The second experiment was launching a water rocket from underwater (see part 2). Why would we want to do that? Why not? We hadn't seen it done before, and we had no idea what would happen.

Flight Day Events - Part 1

• We assembled the new launcher and adjusted it for the first rocket. The setup was quite straight forward, and doesn't take long, although it is a little more complex than our old launcher. Since there was virtually no wind we only used the 1 meter guide rails.
• J4 took off very well out of the new launcher and proceeded almost vertically, the nosecone deployed well, but the parachute didn't unfurl properly almost all the way down. The parachute opened about 3 meters above ground which caused the rocket to swing around horizontally and land undamaged on its side. A pretty close shave!
• We launched it a second time and this time the nosecone came off just after the air pulse so basically the parachute opened at very high speed, the nosecone line ripped from the rocket and the nosecone kept going up, but the parachute brought the rocket down safely. I am glad we have learned to put strong parachute lines on the rockets, they can prevent hours of work in repairs.
• Second up was a rebuilt Polaron rocket. It was in a different configuration since the last attempt. The rocket had only 3 bottles and a new set of fins. The fins were constructed of a fairly thick pieces of plastic, and only held in place with rubber bands. We are now looking at using this technique to hold fins onto the rockets because tape tends to come off easily especially when the bottles stretch. Some tapes also leave a pretty nasty sticky residue when they are removed for repairs. Because of the length of the rocket, we decided to dispense with the fin strut extensions so the fins are now directly mounted on the last bottle.
  
  The flight computer was set and the rocket pressurised to about 80 psi, and one of the joints started slightly leaking. We hadn't pressure tested the rocket prior to launch day, so it was hardly surprising. It turns out that it just wasn't tightened enough.
  
  Since the leak was only slight we decided to launch anyway. The rocket flew a beautiful flight, and on the in-flight video you could see that it only spun on its axis a few degrees. The parachute opened as expected and as the rocket was coming in to land close to the launch pad, I raced after it and caught it before it hit the ground.
  
  
  Polaron Inflight video
  
  
    (If the video does not play, try downloading the latest Flash player from Macromedia)
• Since the launcher was configured for Polaron, we reloaded it into the launcher and started filling it. We were going to go for 110psi, but at around 90psi the joint started leaking again, but a little more this time, so in a quick hurry I told dad to launch it and gave a quick countdown. The rocket took of great but as it was on its way up ... I called out something like "s**t I forgot to turn the computer on!!!" Well you can imagine what happened next. The parachute will not deploy if you do not turn the computer on and arm it. So instead we watched it crash pretty hard. The payload section was completely smashed in, one of the flight computer's PCB's snapped in half and most of the release mechanism components were bent. The launch detect micro switch lost its armature. Later when I checked the little motor and gearbox, I noticed that it was sticking. I thought that one of the gears must have also split, but on disassembly it turned out that there was a tiny grain of sand from the crash stuck in one of the teeth. Cleaning it out resolved the gearbox problem.
  
  An interesting artefact of the crash was the fact that the fins, being attached by rubber bands, allowed them to come off in a triangular pattern a couple of meters from the impact site. They weren't damaged and were easily reattached.
• The one big thing we learned from this crash, was that procedures and checklists are needed for these more complex rockets and launch sequences. There will not be any more rushed take offs. If in doubt, DO NOT LAUNCH.

Flight Day Events - Part 2

• Later on in the day we decided to cool off in the pool, but this time we took the old launcher and an older rocket with us. We had been talking about this for a couple of weeks, so it was high time we did it. The rocket that we used has served us very well from the first few days of experiments, and has continued to do so.
• There was virtually no adaptation of the rocket and launcher for these experiments. We only tied a string to the rocket so it would not fly over the fence, and we had to weigh the launcher down with lead weights so that the rocket would not lift it off the bottom.
• The first launch was only at 40 psi. We played it conservatively at first so that we could see what would happen. The rocket only flew a couple of meters above the surface, but had no problems from getting above the surface, having penetrated about 1 meter of water.
• We increased the pressure to 70 psi and launched again, this time the rocket went higher and would have gone more had it not been for the string. The submerged string caused a lot of drag on the rocket.
• Later we launched the rocket a couple of times again from the same depth with 90psi. The rocket had no problems in leaving the water and would have gone to a considerable height had it not been for the string.
  
  
  (If the video does not play, try downloading the latest Flash player from Macromedia)

• It was a fun experiment, and what did we learn from it?
  
   - It is difficult for the diver releasing the rocket to communicate the count down with the surface personnel. Holding a camera in one hand, the release string in another and a regulator in their mouth was the problem.
  
  - The water provided less drag than was expected.
  
  - It is feasible to launch water rockets from under water.

If you have questions or comments feel free to visit our blog and leave a comment.

Flight Record

Design and Development

Last time we attempted to fly a couple of long rockets we discovered that our launcher was inadequate to support them when there was even a minor cross breeze. The relatively short guide rails also tended to provide less guidance for rockets - which as a result were more likely to stray from vertical.

So we decided to build a new adjustable launcher that will support the next phase of development. We are calling this the medium launcher, as the rockets we are planning in the more distant future will need an even bigger one.

Medium Launcher

The launcher has 4 feet, having one fixed in the middle to support the weight of the rocket and the other three adjustable to allow the launcher to be levelled on uneven ground, or be angled in a specific direction.

The launcher has three 2 meter guide rails that support the rocket’s cylindrical body. The guide rails do not require the rocket to have any special guiding attachments. The guide rails are in separate 1 m lengths to allow for easier storage and allow rockets to be placed more easily on the launcher.

The guide rails are supported by a cross member at the end of each foot for stability. Each guide rail can be moved and locked into position in 5mm increments relative to the center of the launcher, allowing rockets of various diameters to be launched. The guide rails are connected by supporting rings that ensure the correct rocket clearance is maintained along the full length of the launcher. One ring is at the 1 meter mark and the other is at the two meter mark.

Each ring has a separate adjustment for each guide rail, so fine tuning of direction and clearance can be achieved. Each ring is also supported by 6 tensioning lines to prevent the guide rails from twisting. The rings are also designed to provide clearance for rockets with both conventional and ring fins.

The release mechanism is based on an all brass Gardena hose attachment. The release mechanism stands off the launcher about 30 cm allowing rockets with ring fins to be launched. The base of the release mechanism has a quick connect hose fitting for air and a small lever and pulley for the release string. The Gardena hose attachment was modified to include a custom return valve to prevent water entering the hose.

Line tensioning is achieved using the same technology that tents use to tighten lines – a piece of bent metal with two holes in it. Very simple and very effective.

The launcher can be used with just the 1 meter launch rails for smaller rockets, or in the 2 meter configuration for longer rockets.

The launcher set up time is about 8 -10 minutes.