last updated: 21st october 2023 - Day 226 to Day 230 - Various Experiments

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Servo Timer II




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Flight Log Updates

#230 - Tajfun 2 L2

#229 - Mac Uni AON

#228 - Tajfun 2 Elec.

#227 - Zip Line

#226 - DIY Barometer

#225 - Air Pressure Exp.

#224 - Tajfun 2

#221 - Horizon Deploy

#215 - Deployable Boom

#205 - Tall Tripod

#204 - Horizon Deploy

#203 - Thunda 2

#202 - Horizon Launcher

#201 - Flour Rockets

#197 - Dark Shadow II

#196 - Coming Soon

#195 - 3D Printed Rocket

#194 - TP Roll Drop

#193 - Coming Soon

#192 - Stager Tests

#191 - Horizon

#190 - Polaron G3

#189 - Casual Flights

#188 - Skittles Part #2

#187 - Skittles Part #1

#186 - Level 1 HPR

#185 - Liquids in Zero-G

#184 - More Axion G6

#183 - Axion G6

#182 - Casual Flights

#181 - Acoustic Apogee 2

#180 - Light Shadow

#179 - Stratologger

#178 - Acoustic Apogee 1

#177 - Reefing Chutes

#176 - 10 Years

#175 - NSWRA Events

#174 - Mullaley Launch

#173 - Oobleck Rocket

#172 - Coming Soon

#171 - Measuring Altitude

#170 - How Much Water?

#169 - Windy

#168 - Casual Flights 2

#167 - Casual Flights

#166 - Dark Shadow II

#165 - Liquid Density 2

#164 - Liquid Density 1

#163 - Channel 7 News

#162 - Axion and Polaron

#161 - Fog and Boom

#1 to #160 (Updates)



Each flight log entry usually represents a launch or test day, and describes the events that took place.
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Day 105 - Polaron G2 flight, Axion G2 first flight
Repaired Polaron G2 being prepped the night before.
Little Axion next to big cousin.
3.8L of water is poured into the lower half of the rocket.
The top section of the rocket is screwed to the lower half already on the pad.
My pirate impersonation... has anyone seen my leg?
Launched at 210psi.
Frame captured from video. Shortly after burnout as rocket reaches maximum velocity of ~269km/h
Coming down under both back up and main chutes.
Rocket landed gently on it's side in the tall grass.
Recovery crew is quickly on the scene.
We download the flight data after each flight just in case we loose it on the next flight.
Axion G2 has an 8L capacity
Here you can see the Jet foaming spacer at work.
Pointed in the right direction.
Launching rockets is not very much fun.
Frame captured from video.
Axion G2 post landing. It dug a 15cm hole in the soft ground.
Shhh!... don't tell your mum
We need a bigger table.
Axion IIc launched at a modest 125psi.
Axion IIc coming in for a nice landing ....
....almost on top of the trees.
A photo for the boys to take to school for their weekly "news".
Jet foaming spacer components. The end of the PVC has been reamed out for smoother flow.
Spacer components assembled and glued into position.
PCBs have arrived for the servo timer II.
Top and bottom views of the timer. The rotary switch will be smaller on the production run.

Date:  8th May 2011 8:15am - 12:00pm
Doonside, NSW, Australia
 Mostly calm, with light breeze later in day, little cloud, temp ~21C
Team Members at Event:
PK, Paul K, John K, Jordan K and GK

Launch Day Report

Dad had to repair the pressure regulator inside the control panel the day before because it was slightly corroded from the water we keep pumping through it during hydro tests. It wasn't adjusting the pressure smoothly.

The weather was great for launching rockets this week. Mostly blue skies and very little wind. We were going to attempt to launch the G2 rocket again after repairs from the last CATO. The only thing we changed on the rocket was the addition of the rail buttons for the new launcher.

This time we also doubled the length of the hose and the launch string so we were further back just in case the rocket decided to misbehave again.

Polaron G2 flight

The launcher was quick to setup and we again placed the lower half of the rocket on the pad and filled it with water. We then screwed the upper section into the lower half, and tightened the parachute cords.

This time we pressurised the rocket a little bit first perhaps to 20-30psi and checked for leaks. The camera and altimeter were started and all other electronics armed. This gave the air inside the rocket some time to cool. We then pressurised the rocket to 210psi slower than last time.

The rocket took a bit of effort to release. I guess the higher pressure just makes things stick a bit more, but Paul put his shoulder into it and the rocket launched. It was quite evident from the noise it made that it had more power than normal. It nicely accelerated to apogee with a slight roll. We had also angled it away a little from the spectators and the trees so that if the parachute failed again it would fall away from people. You could almost feel the stress on the rocket when it hit peak velocity. We could see the backup parachute released just after apogee as was designed, and we could see the main fully open within a second or two after the backup.

The rocket landed safely on its side in the tall grass. The only damage was one broken shroud line out of 12 on the backup parachute. The altimeter read out 789' (240m) which was pretty close to what both Clifford Heath's and Dean Wheeler's simulators said it would go up to. This was a good result because we can continue to use the simulators for this rocket to predict expected performance.

The top speed was approximately: 245 feet/s...(269 km/h or 167mph) this was calculated from the ascent rate.

Polaron G2 flight

This is the highest single stage rocket we have flown to date. This rocket was also more than twice as heavy as any of our previous rockets we have flown to this altitude. With this flight we have also successfully reached Phase I of the project, and will be starting on the next phase soon. We will try to fly the rocket in this configuration again a number of times to better characterise it's flight performance. I'm really looking forward to the next phase as the rocket will use boosters and Jet foaming to produce a really long burn.

Axion G2 flight

Because of a shortened launch day we decided to go ahead and launch the Axion G2 with foam next. This time we only pressurised it to 200psi because the bottles were only hydro tested to 200psi the day before. (They should hold around 300psi). The take-off was quite slow but a great foam trail was produced all the way to apogee. Again the rocket was noisier than normal. The parachute, however, failed to open and the rocket crashed heavily in the soft ground. All the electronics survived and it looks like only the top bottle and nosecone were damaged.

We're not sure what caused the deployment failure but I suspect that it was the slow take-off, and the timer just didn't detect launch. The parachute was still wrapped in the parachute cord, and the servo though damaged was still in the stowed position. The timer was verified before launch to be armed, and on the ground the power was still in the ON position. I plugged the timer into the same battery with a new servo and the timer still worked correctly. The time setting was also correct.

We had the original MD80 camera on board as well as a Z-log altimeter. Both were mounted under the first bottle and were thrown clear on impact. The video camera was still recording when we found it. The alloy case really protects the camera. The altimeter's power supply was severed, but it still recorded the entire flight.

So overall not bad damage, we just need to replace the servo and make a new bottle.

The Jet foaming spacer (see below) seemed to work quite well.

The simulator vs actual results were interesting too. Both simulators predicted an altitude of around 550', but the altimeter gave us 664' which is considerably higher. We have seen this on previous foam flights at higher pressures. The foam really looks like it is producing measurable improvements in performance with ordinary nozzles.

Axion G2 flight - No, the rocket did not bounce that high!

Axion IIc flight

The last launch of the day was a low pressure (125psi) Axion IIc rocket. Though it wasn't setup for Jet foaming we still put bubble bath in the water and some foam was produced during pressurisation. This made a longer lasting water phase with the trail visible about half way up. This rocket was also equipped with the newly build Servo Timer II board. So this was a good test of the timer. The parachute deployed soon after apogee and the rocket landed without damage. We were very lucky as the rocket just missed the tallest trees.

Day 105 - Highlights

Axion G2

Because of the rain delay from last week, we had time to assemble a second high pressure rocket made from the 90mm spliced quads. This rocket used standard Axion components such as fairings, nosecone and fins, so was quite easy to put together. The rocket also was intended as a test bed for the Jet foaming spacer.

Jet Foaming Spacer

One of the biggest variables with Jet foaming is the amount of water that is trapped in the upper chamber. This always varies depending on how much water makes it up there when pouring it in and then how long the rocket sits on the pad before launch giving the water a chance to drain into the lower chamber.

The other issue that makes jet foaming work effectively is a pocket of air trapped in the upper part of the lower chamber. This allows the air to be mixed with the water in the lower chamber. If the lowest bottle is completely full then very little air and water end up mixing. When we used to use a Robinson coupling on the bottom of the lower bottle the bottle lobes in the penta-claw stored a certain amount of air that would be mixed in. When we switched to spliced-pairs the shape of the bottle allowed all air to escape to the upper pressure chamber through the tornado coupling resulting in no air pocket.

The Jet Foaming Spacer is a piece of PVC pipe that extends about 15cm below the tornado coupling. It's purpose is to create a pocket of air in the lower chamber. During pressurisation the air goes to the top of the lowest chamber and starts forcing the water up the spacer until the water level reaches the bottom of the spacer and then the air starts flowing up the spacer tube to the upper pressure chamber.

Jet Foaming Spacer

This creates a pocket of air of known volume in the lower chamber and also the volume of water in the lower chamber is fixed. This will allow us to do more accurate jet foaming comparison flights. When the rocket stops being pressurised the water in the lower chamber remains fixed as the end of the pipe is level with the water level in the lower chamber.

At the bottom of the PVC pipe is an 8mm jet foaming nozzle. We opted for a wider pipe going to the nozzle rather than an 8mm pipe from the tornado coupling to reduce the amount of friction in the tube as air and water pass through it.

You can vary the size of the air pocket simply by changing the length of the tube. A plastic ring is glued near the top of the PVC pipe that fits inside the tornado tube and prevents the tube from being ejected. The nozzle is just made from a piece of plastic and glued into the end of the pipe.

We also use an o-ring on the outside of the tube to stop air going up past the outside of the tube, though a small amount of leakage is not that critical.

Servo Timer II Update

We received the PCBs this week from PCBCart. They were recommended by some of the other rocketeers and we definitely had a good experience with them.

I've soldered up a couple of the timers and will continue to do more flight testing in the coming weeks. I'm currently placing an order for all the components

Flight Details

Launch Details
Rocket   Polaron G2b
Pressure   210 psi
Nozzle   16mm + launch tube
Water   3800mL
Flight Computer   FC V1.6 - 7 seconds
Payload   Backup parachute deployment with ST II and MAD, Zlog altimeter, MD-80 clone camera.
Altitude / Time    789' (240m) / 50.4 seconds
Notes   Very good and mostly vertical flight, with slight roll. Backup parachute opened just after apogee, with Main opening soon afterwards. Good landing without damage. 1 shroud line broke on the backup parachute. Nice and noisy.
Rocket   Axion G2
Pressure   200 psi
Nozzle   9mm
Water   2100mL + foam
Flight Computer   ST II - 5 seconds
Payload   MD80, zlog altimeter, jet foaming spacer
Altitude / Time    664' / 15.2 seconds
Notes   Maiden flight. Good takeoff and good foam generation all the way to apogee. Parachute failed to deploy and rocket crashed heavily. All electronics survived. Good video and altimeter data. Suspect low-G takeoff failed to detect launch.
Rocket   Axion IIc
Pressure   125 psi
Nozzle   9mm
Water   1700mL + foam
Flight Computer   ST II - 5 seconds
Payload   None
Altitude / Time    ? / 29.6 seconds
Notes   Good flight with parachute opening just past apogee. Good landing right near the trees.


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