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

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Construction - Basic


Ring Fins

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Construction - Advanced

Robinson Coupling

Splicing Bottles #1

Splicing Bottles AS#5

Reinforcing Bottles

Side Deploy #1

Side Deploy #2

Mk3 Staging Mechanism

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Construction - Launchers

Gardena Launcher

Clark Cable-tie

Medium Launcher

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Launch Abort Valve

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How It Works

Drop Away Boosters

Katz Stager Mk2.

Katz Stager Mk3.


Dark Shadow Deployment


Recovery Guide


How Much Water?

Flying Higher

Flying Straight

Building a Launcher

Using Scuba Tanks


Video Taping Tips

MD-80 clone

Making Panoramas


Burst Testing





Servo Timer II




V1.3, V1.3.1, V1.3.2


Deploy Timer 1.1

Project Builds

The Shadow

Shadow II


Polaron G2

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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.
Click on an image to view a larger image, and click the browser's BACK button to return back to the page.

Day 79 - Acceleron Vb Explosion and Axion V flights
Axion IVb gets filled with 1.3L of water and foam.
Standing on a crate makes it easier to load the second stage.
Getting ready for test Flight #2
Coming up to pressure at 130psi... ....Ooops!

Photo: David Kelleher

Only Casualties:
1 ring brace
1 2L spliced pair
1 lowest bottle on sustainer.
Sustainer nozzle is still locked in the staging mechanism.
You can see half of the failed bottle here.
Top part of the booster was prevented from flying away by the parachute cord.
Lowest sustainer bottle. Blew up as a result of the explosion next to it.
Broken ring brace. One of the servo wires running along it was also severed.
The altimeter and camera are now located under the top bottle for protection.
Repaired Axion IVb with new fin set becomes Axion V.

Photo: David Kelleher

Good landing
Cloudless and windless sky.
Axion V - flight #1
Axion V with some red food colouring to make it look faster.
The lowest bottle has a very streamlined shape. You can't buy them anymore. :(
Axion V launched at 130psi.
Flight #2

Photo: David Kelleher

This time the rocket reached 468' (143m)
Changes seen at  Doonside with the construction going on.
It came down very close to the rocket eating trees.
Axion V - flight #2
Helping to prepare a regular rocket motor for John's rocket.
Running back into camera position.
Flight #3 pitched over a little bit after take off....
Just washing the sky with a bit of soap.
Launch area and car park. (Descending under parachute)
... and landed a fair way down range.
The lost alarm on the flight computer could be heard ~20m away in the open.
Axion V - flight #3
New MD-80 camera next to FlyCamOne V2.
Despite the size the MD-80 weighs about the same as the flycam, but is more ruggedised with an alloy body.
We used Ed's (Houston water rockets) corriflute alignment and shaping technique for Axion's IV fins. Note the holes drilled in the middle for better glue grip.
New booster nozzle seats for the cluster launcher. The special shape allows the nozzles to pivot as bottles expand. These seal the nozzles from the inside. They simply screw onto the existing launcher.
Acceleron booster nozzle evolution. Each Acceleron rocket uses three nozzles.

Date:  25th July 2009 (8am - 1:30pm)
Doonside, NSW, Australia
 Cold in the morning, (5 degrees C), warming up to 17 degrees, no wind and no clouds.
Team Members at Event:
PK, GK, AK, Paul K and John K.

In this update we cover :

Acceleron Vb

After reviewing the first test flight we have incorporated a number of changes into the booster and sustainer in order to help improve the chances of flying vertically.


  • We replaced the fins on the sustainer with ones about three times the surface area of the previous set. We made these from corriflute material and glued them directly to the lowest bottle rather than using the removable fin set like we have been using. We tried a couple of small improvements this time around:

    - We streamlined the leading edge based on a technique described by Ed from houston_water_rockets discussed here: and pictured here:
    (NOTE: Unless you are already a member you may need to join the Yahoo forum to see the pictures)

    - We drilled the little holes in the corriflute material on the inside so that we could use much less glue to attach the fins. This was done to try to avoid extra weight of glue used on the fillets.
  • We mounted the new MD80 camera (see below) along with the altimeter under the first bottle to help protect it from possible impacts.
  • Switched to using V1.6 of the flight computer for deployment.
  • We reduced the amount of water in the sustainer to 1.3L.


  • We modified an older set of nozzles to give a 15.6 mm ID in order to increase the thrust on take off. The takeoff acceleration is almost doubled now compared to Acceleron V. The inside of the nozzles were also polished.
  • We switched over to the older pressure switch (TDD) that we have flown on previous Acceleron rockets.
  • We have reduced the amount of water in each of the booster segments to 2.5L. This gives slightly lower performance, but it helps with stability. Once stability of the rocket is verified we will increase this back up to ~3.2 liters.
  • Dad made a new narrow seal stamping tool and we made a number of seals from three different rubber sheets. The narrow seals were designed to prevent the seal partially blocking the nozzle.


  • We made new nozzle seats for the new nozzles for the launcher. These simply screw into the existing launcher. Because the nozzle diameter is now big enough, we have switched to sealing the nozzles from the inside. The o-rings are on the launcher now. (see picture) The special shape of the nozzle seats allows the nozzles to pivot while remaining sealed. This is important because the bottles stretch during pressurization.

New Camera

Having had the need to replace the smashed FlyCamOne V2, we thought we'd give this camera a try: (AUD$105 delivered)

The resolution is 640 x 480 @ 25fps and it takes up about 1/3 the volume of the FlyCamOne! You can fit this pretty much in any rocket including T8 FTC. The low light response is great although a little grainy, which is miles ahead of the FCO2 that shows mostly black. The frame rate is also good. The overall image quality I'd say is slightly lower, and the colour also seems not to be as rich as the FCO2.

The big plusses are that it does not suffer from the audio lag and dropped frames, and there are no battery issues with it. The build is very solid and the case looks like it is made of alloy.

It came with a 2Gb micro SD card which gives around 1.5 hours recording at 640 x 480 @ 25fps. Operation is extremely simple. Turn it on, push button to record. Push again to stop.

The other option it has is to start recording when the sound level goes above a certain value and then stops recording after 2 minutes if the sound level drops off again. This I think would be ideal for rockets. ... turn it on to standby. .... yell at the rocket just before launch (or tap it a couple of times) and then launch within 2 minutes. The sound of the launch should be enough to keep it recording for most of a flight.

Flight Day Report

The launch day was about as perfect as they come. There were no clouds in the sky and no wind. Although there was a little bit of frost on the ground when we arrived, that disappeared quickly.

  • We had to set up the launcher in a different place again due to the construction going on that morning.
  • The setup was quite straight forward with no issues.
  • As we came up to 130psi ( 9 bar ) pressure and the rocket was holding awaiting launch, one of the middle spliced pairs of bottles blew apart in the splice.

    Luckily it was one of the boosters with a parachute so no electronics were affected by the immediate blast. The blast also ruptured the lowest bottle on the sustainer. We were lucky again because that bottle was mostly full of water so no major explosion occurred there.

    The top part of the booster flew upwards with quite a bit of force and tore through the ring brace braking it in 4 places. The booster was stopped from flying further because of the parachute cord that is attached to the top as well as the bottom section of the entire rocket.

    When the bottom sustainer bottle blew the Robinson coupling in the upper section acted as a nozzle and the sustainer flew off downrange where it landed safely on its side in the tall grass.

    If the ring brace had not broken, we had enough spare parts with us to repair the rocket and try for another flight.

    None of the electronics on board the rockets were damaged, and all the other components like the staging mechanism, base plate and launcher also were unharmed.

    Overall the repair bill will be under $5 as we need to make up a new 2L spliced pair to replace the one that blew, replace the sustainer lowest bottle and re-attach its fins. The ring brace being made of balsa and fiberglass can be glued back together. (Repairs are already under way)

    This of course isn't the first time a fully pressurised Acceleron blew up, although the last time it was more heavily damaged.

  • We put the booster aside and set up our Medium launcher. We brought a number of rockets with us in case something like this happened.
  • Within 10 minutes we removed the tail section of Tachyon V rocket and screwed it into the top section of the Axion IVb sustainer that just blew as it was already fitted with the new camera and altimeter. We packed its parachute, reprogrammed its flight computer and were ready to launch again.
  • We ended up flying the new rocket (Axion V) three times on the day with foam and all three flights went really well. The flights were nice and straight in the windless conditions and the parachute always opened near apogee. We ended up with good onboard video, and the second flight managed to reach 468' (143m).
  • We also ended up flying three of the boys pyro rockets. All landed well, so despite the initial failure we ended up having a great day.

What's next

We will rebuild the rocket in the same configuration, but will most likely only launch it at 120psi on the next test. Although the bottles get tested to the full operating pressure for 2 minutes, multiple pressurization can eventually cause them to fail at lower pressures. Once we get at least a couple of good flights in we will again bring up the pressure. Since our launcher allows it and we are all set up for it with the control panel, as an intermediate step we may pressurize the booster to 120psi and the sustainer to 130psi.

Flight computer settings

New updated settings for Acceleron Vb and Axion IV when using a lighter water load. 2.5L for Acceleron and 1.3L for Axion.

V1.6 V1.6 V1.6
Primary Secondary Sustainer
0. 0   0. 0   0. 0  
1. 0   1. 1   1. 8  
2. 1 0.1 secs 2. 8 1.8 secs 2. 2 8.2 secs
3. 0   3. 0   3. 0  
4. 0   4. 0   4. 0  
5. 1 0.1 secs 5. 1 0.1 secs 5. 1 0.1 sec
6. 0   6. 0   6. 0  
7. V   7. R   7. V  
8. 7 1.12 secs 8. 7 1.12 secs 8. F 2.4 secs
9. V   9. V   9. 0  
A. 0   A. 0   A. V  
B. F 2.4 secs B. F 2.4 secs B. F 2.4 secs
C. 0 sound OFF C. 0 sound OFF C. 2 Sound ON
D. 0   D. 0   D. 4  
E. 0   E. 0   E. 5  

Flight Details

Launch Details
Rocket   Acceleron Vb (Ac) and Axion IVb (Ax)
Pressure   130 psi
Nozzle   15.6 mm x 3 (Ac), 9mm (Ax)
Water   9.2 L (Ac), 1.8L + foam (Ax)
Flight Computer   V1.6 x 2 (Ac) and V1.6 (Ax)
See settings above
Payload   Zlog Altimeter x 2, FlycamOne2, Mini DV cam MD80
Altitude / Time    0 (Ac) / 74' ( 22m ) / 1.9s (Ax)
Notes   CATO on pad at 130psi. Sustainer bottom bottle destroyed, fin damage. Booster 1 spliced pair destroyed, two inter bottle separators damaged, and ring brace broken in 4 places. Booster camera failed to record. Good onboard video. All electronics and mechanical components survived without damage.
Rocket   Pod 2 (Paul's)
Motor   C6-5
Altitude / Time   ?
Notes   Good straight flight, with very little roll. Parachute deployed near apogee and the rocket landed well. No damage. 
Rocket   Axion V
Pressure   120 psi
Nozzle   9 mm
Water   1400 mL
Flight Computer   V1.6 setting 5.2 secs
Payload   MD80 camera, Zlog altimeter
Altitude / Time   342' (104m)  / 28.7 s
Notes   Nice straight flight. Parachute opened after apogee. Good landing. Good altimeter data and video.
Rocket   Thunder Bee Hero (Paul's)
Motor   1/2A3 - 2
Altitude / Time   ?
Notes   Good straight flight, motor blew out so no recovery although rocket survived the landing
Rocket   Axion V
Pressure   130 psi
Nozzle   9 mm
Water   1400 mL
Flight Computer   V1.6 setting 5.2 secs
Payload   MD80 camera, Zlog altimeter
Altitude / Time   468' ( 143m ) / 44.6 s
Notes   Nice straight flight and went high. Parachute opened after apogee. Good landing. Good altimeter data and video.
Rocket   Axion V
Pressure   130 psi
Nozzle   9 mm
Water   1400 mL
Flight Computer   V1.6 setting 5.2 secs
Payload   MD80 camera, Zlog altimeter
Altitude / Time   409' ( 125m ) / 32.5 s
Notes   Nice flight, but slightly pitched over. Parachute opened after apogee. Good landing. Good altimeter data and video.
Rocket   Thunder Bee 7 (John's)
Motor   1/2A3 - 2
Altitude / Time   ?
Notes   Good straight flight, streamer deployed well at apogee. Safe landing.


More Thermal Testing

About a month ago when disassembling one of our rockets we noticed that the threaded section of a couple of the bottles had shrunk and distorted. The threaded sections were inside the black Tornado couplings. There are really only two sources of heat that could have caused this: The sun and/or pressurising the rocket.

We know from experience that black tape on bottles and sun don't mix. So we setup up a mock up of the joint and placed an electronic thermometer (thermocouple) against the inside of the threaded section of the bottle inside the coupling. We placed the section along with the inter bottle separator in the sun.

The ambient temperature was 17 degrees C. Within 30 minutes the temperature on the inside of the coupling reached 38 degrees C and remained stable at that point. To simulate conditions on a hot day and during transportation, we moved the experiment into the car and closed all the windows with the Tornado coupling still exposed to the sun. Again within about 30 minutes the temperature inside the coupling climbed to 54 degrees C at which point the LCD panel on the thermometer turned all black from the heat. We should have placed the thermometer in the shade. We stopped the experiment at that point. When the LCD screen cooled down again it went back to normal.


This temperature increase due to the sun is significant, because if a rocket is left out on the pad in the sun and then is pressurised, the further temperature increase due to air compression can very easily push the temperature over the critical 65 degrees C at which point PET plastic starts to become soft. The force as a result of the pressure at the same time could make the coupling fail.

We will now be covering any tornado couplings with a roll of white paper to protect against heating.


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