last updated: 16th March 2017 - Day 178 & day 181 Acoustic Apogee Detector

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Flight Log Updates

#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

#160 - Chasing Rockets

#159 - Measurement

#158 - Dark Shadow

#157 - Polaron G2

#156 - Foam Flights

#155 - Down The Barrel

#154 - Revisits

#153 - ClearCam

#152 - Mullaley, Axion G2

#151 - Competition Day

#150 - Rocket Salvos

#149 - Glide Fins

#148 - Too Windy

#147 - Descent Rates

#146 - G2 Launcher

#145 - Harness

#144 - Water vs Foam

#143 - Whalan Reserve

#142 - Doonside

#141 - Windy

#1 to #140 (Updates)



Each flight log entry usually represents a launch or test day, and describes the events that took place.
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Day 8 - Windy and Wet
Jordan on its way to our highest altitude.
X-21 ready on the launch pad. Our first 2 bottle rocket.
...and its takeoff.
You can still see the vapour inside the bottle after landing.
Brotanek II as it re-enters the lower atmosphere.
Jordan taking off from this high angle view.
The damage it sustained upon impact. You can see the bottle buckled near the nosecone.
Parachute packed with foam providing a spring mechanism to pop off the nosecone.
Plenty of standing water on the oval made it convenient to refuel.
Brotanek II safely back down. Parachutes increase the survivability rate of rockets.
Jordan taking off with only air in it. No Water was used.
Spek on its return.
Packing the parachute into the nosecone. The nosecone is hanging next to the rocket.
Added weight at on the bottom of the rocket ...not a good idea.
Parachute failed to open and the rocket crashed through a tree.
Date: 5th August 2006  10:30am - 12pm

Location: Denzil Joyce Oval. (launch site #4)
Where exactly is that? Click the above link to see a Google Earth place mark. What is Google Earth?

Conditions: Overcast, occasional shower, quite a fresh wind, ground saturated with standing water.


Name Capacity Notes
Little Man II 1.25 L Equipped with whistles. This one goes pretty high. Main bottle was replaced since the last flight day.
Spek 2 L An older rocket now equipped with a parachute. 
Jordan 1.25 L A new lightweight rocket. Nose weight added since last launch day. Currently the highest performing rocket.
X-21 2 x 1.25 L New experimental 2 bottle rocket joined at the base, with a parachute recovery system
Brotanek II 1.25 L This rocket has also been around for a while. For this launch event it has a new main bottle, and an improved parachute deployment system.

Team Members: PK and GK.

Number of launches: 16

The purpose of this launch event was to test the new X-21 two bottle rocket and test new parachute deployment systems. It was a good time to go down to the oval since there was virtually no one else there, however, we believe the bad weather had an adverse effect on the launches.

Design Note: Foam placed under the nosecone, on top of the parachute acts as a spring mechanism to help push the nosecone off. We vary the amount of foam to make it easier or harder to push the nosecone off.

Listen to a water launch: Water.wav
There is a distinctive two pulse sound - one as the water bursts out, and the second as the water runs out and the remaining air bursts out.

Listen to an air only launch: Air.wav


  • The X-21 is our biggest rocket to date. We didn't use the simulator to figure out how much water to use, but just took a guess. We filled it with about 600ml, whereas we should have used closer to 750ml. The rocket was quite unstable near the top of its flight path, but that's something a good set of fins will fix. The bottle joint stood up very well to the pressures and also the landings.
  • Both Brotanek II and Spek used a new wire supported nose cone mechanism, in order to reliably support the nosecone during takeoff. We discovered that both rockets were losing the nosecone too early into the flight. Video analysis showed one possible cause of this. Because the wind was quite strong on the day, it appeared that after launch the cross breeze was enough to angle the rocket slightly sideways. The rocket tended to point into the crosswind. This probably caused a shearing force on the nosecone as the rocket was heading up and therefore was blown off. I am keen to try the same design on a calm day. We modified the nosecone for it to sit lower on the rocket and that had a positive effect on the nosecone performance.
  • In a moment of insanity, not following the rules of aerodynamics, we decided to add a weight to the tail end of X-21 (3 AA batteries) to make it come down backwards hoping the parachute would be released that way. We forgot about the going upwards part! In the video it clearly shows the back-flip that happens when the CG is behind the CP.
  • On its second flight Jordan flew 9.01 seconds which according to the simulator is in the order of 85-90 meters. How do we measure the time so accurately? We video tape each launch and then using a video editor we are able to step frame by frame to find the exact launch time and the exact landing time. This was likely to have been the highest launch to date. Jordan weighs about 92 grams.
  • On the video camera I discovered the lock focus button which prevents the camera loosing its focus when you are video taping a tiny dot in the sky. This proved quite successful. No more automatic focus for us. This also allows you to zoom in without the camera having to hunt for focus.
  • Little Man II was launched with the highest pressure to date - 130psi. We are slowly increasing the pressures to see the effects on the flight path. We think the compressor can go up to about 200psi, but at that stage we will use some form of re-enforcing on the bottles. The flight time was over 8 seconds. Little Man II weighs in at 145grams, mostly because of the heavy nosecone.
  • We fired Jordan with nothing but air in it to see what happens. The take off was sure fast, but only reached about 2/3 of what it does with water. The sound the rocket makes on take off is also quite different.
  • When we ran out of water, rather than going back to the car to get more we just refuelled from one of the puddles next to the launcher.
  • The last flight of the day was the best because Brotanek II went almost straight up and the parachute deployed about a second past apogee. The flight time was about 17 seconds.

Flight Record

Launch Rocket Pressure (PSI) Notes
1 Jordan 80 Flew quite high and straight
2 Jordan 110 Flew very high 9.01 seconds. According to the simulator that is about 85-90 meters.
3 X-21 80 Parachute did not open, and the rocket was quite unstable near top. Fell sideways.
4 X-21 100 Parachute did not open, flew in a big long arc.
5 Spek 110 Parachute opened too early. Foam under the nosecone was present.
6 Spek 110 Parachute opened too early again. No foam  under the nosecone this time.
7 Brotanek  II 120 Parachute opened too early. Foam was present under the nosecone.
8 Brotanek  II 120 Parachute opened too early, although the rocket flew higher this time. No foam was present under the nosecone.
9 X-21 80 Nose cone fell off due to unstable flight profile, but chute failed to open as it stayed in the nosecone.
10 X-21 100 Nose cone fell off due to unstable flight profile, but chute failed to open as it stayed in the nosecone. Again!
11 Little Man II 130 Good flight, and fairly high. Survived landing fairly well.
12 Jordan 110 Good flight, good altitude.
13 Jordan 90 AIR ONLY, this was to see how it flies without water. Certainly made a different sound, and took off pretty quick, although the altitude looked about 2/3 of what it did with water.
14 Brotanek II 110 Parachute deployed too early.
15 Brotanek


110 Nosecone was modified to sit lower on the rocket, with no foam. This caused the nosecone not to come off and the rocket flew quite high and in a big arc and crashed through a tree on the way down. The tree probably saved it from quite a bit of damage.
16 Brotanek II 110 Great flight, parachute deployed after apogee. Flight time ~17 seconds.

Notes to self

  • Bring gumboots when launching at a flooded oval. Our shoes and socks were soaked.
  • Paint the rockets a dark colour so they can be seen against the sky.
Day 9 - In-flight Video and Perfect Flights
The tiny solid state video camera is mounted inside a cardboard sleeve.
Within the sleeve it is surrounded by foam.
When the rocket is to be launched, the start button is pressed ...
... and the camera is inserted into the rocket. Here you can see the foam protection.
A large hole provides unobstructed view
Ready on the launch pad.
In-flight video:
Click here to see video.
The launchee ...of the rocket as it came down.
The full selection of rockets for the day.
Poised for the maiden flight.
A nice shot of a Brotanek II taking off.
Sometimes you just have to get wet in order to get a nice video shot.
Straight up and straight down. You can see the impact crater at John's foot. The nose cone remained buried.
A long distance shot of Brotanek II drifting down.
Date: 13th August 2006  7:30am - 9:15am

Location: Denzil Joyce Oval. (launch site #4)
Where exactly is that? Click the above link to see a Google Earth place mark. What is Google Earth?

Conditions: Great weather, cloudless sky, mild temperatures, slight breeze.


Name Capacity Notes
Little Man II 1.25 L Equipped with whistles. This one goes pretty high. Remained in the same configuration since last flight day.
Spek II 2 L This was the same rocket (Spek) as the last flight day with the addition of a digital video camera  module. The parachute was moved further up the rocket. 
Jordan 1.25 L The same rocket as last flight day. The rocket remained in the same configuration.
"OO" 2 x 1.25 L New experimental 2 bottle rocket joined at the base, with twin parachute recovery system. This is the first rocket with flat fins rather than our typical ring fin. Turned out to be quite unstable.
Cena 1.25 L This rocket has also been around for a while. It remains in the same configuration since last launch day.
John John 600mL This is our smallest rocket and has performed well. It remained in the same configuration since last launch day.
Brotanek II 1.25 L An older rocket that has flown a number of times. It remained in the same modified configuration since the last flight day.

Team Members: PK, GK, AK, Paul and John.

Number of launches: 15

This was a great flying day, with the stars of the show a couple of new rockets. The first "OO" being a two 1.25 L bottle rocket with a more conventional stabilising fin design. The second "Spek II" had a tiny video camera mounted in lots of foam. This was also a day of firsts: a) Twin parachutes; b) conventional flat fins; c) video camera; and  d) highest launch pressure.


    The first rocket of the launch pad was "OO". This is a very good looking rocket and is even pained. With about 750ml of water and 80psi pressure the rocket took off but immediately started turning over, even as it left the launch pad. Luckily for us it decided to fly the other way. Video analysis shows that it was still accelerating when flipped over and heading towards the ground. This means that it has quite a severe stability issue and we believe this is due to the fins being too far forward on the rocket, and the amount of water in it is causing the CG to be quite far back. We will have to add large fins quite a way back on this rocket.
  • The second flight was our first with a tiny video camera. The camera was generously contributed by a friend at work. The camera uses a 8Mb flash memory module to record up to 30 seconds of 352x288 video. The camera is powered by a single AAA battery! The frame rate is quite reasonable and it also records sound. The camera is housed in a padded section of the rocket to help it survive the landing. Instead of making an elaborate trigger mechanism to start recording, the camera is housed in a separate cardboard sleeve that can be easily inserted and secured in the rocket. We simply turn it on, push the record button, insert the sleeve into the rocket tape it in, and fire it. From the start of recording to blast off is between 5-10 seconds, so that leaves 20-25 seconds of in-flight video. The rocket moves around quite violently and so the view is quite all over the place, but this is very typical of small rocket mounted cameras. At left are a number of captured frames from the video sequence.

    Water Rocket in flight video.

    This was our very first video.
    For a better in-flight video have a look at Day 10.

    Because we didn't have a laptop with us to download the video and clear the memory, we could only launch it once on the day. We will look at borrowing a laptop for downloading so we can do more flights at a time.

    The camera is mounted in such a way that on takeoff it is looking at the horizon. The parachute string is mounted so that when the rocket is hanging on the way down the camera points downward. 

    The rocket chosen to fly the camera was the Spek - 2 L rocket because during the last flight day it had always released the parachute too early. We wanted to make sure that the chute will deploy rather early than not at all. We believe that the fins are slightly misaligned and that causes the rocket to tip over and deploy the parachute. The height reached by the rocket was around 30 meters. We will give the rocket new, stiffer and longer fins in order to stabilise it. We may also anchor the parachute at two points on the rocket to try to stabilise it on the way down.

    We also chose not to attach the nosecone so it didn't dangle below the camera. The nosecone is harmless enough to come down without a parachute.
  • Painting the rockets with dark colours worked well against the blue sky. sky.
  • Jordan's one and only one flight on the day went well until it decided to fly in a great arc, and with the performance we get out of it, it flew a long way straight into the creek. There were a lot of reeds and so we though the rocket was lost. But minutes later we saw it floating in the creek, and a long branch retrieved it.
  • On one flight TNT flew a good flight, the nosecone separated, but the parachute failed to open, 2 meters above the ground it finally decided to open and slowed the rocket down enough to prevent any damage to the rocket. That was a close shave.
  • I forgot to buy a new video tape for the camera, and only had five minutes left on the tape from last week. Switching to long play (LP) mode gave me an extra couple of minutes, and only filming the critical shots made the tape last through the flight day.
  • Brotanek II flew quite a few flights and at least 3 of them flew very well. It went straight up and the parachute opened near or just after apogee. These flights were around 20 seconds each.  The rocket configuration remained identical to the last (windy) launch day where the nosecone was coming off early, and so our suspicions that the crosswind had something to do with it is further supported.
  • On one of Brotanek II's flight the nosecone failed to come off, but it appeared that near apogee the nosecone tipped over and remained tipped over causing the rocket to fly at an ever increasing angle to the ground until it was gliding almost horizontally and landed like an aircraft, well not quite, but enough to prevent the rocket from being damaged.
  • We also broke our personal pressure record a couple of times, first up to 135psi and then 140psi on the last launch. In both cases they were Brotanek II (1.25L) bottle.
  • TNT performed also very well, and its black colour made it very easy to see. The parachute almost always deployed. This is a very good rocket too.
  • New nozzles were made that have a longer thread to hold and seal the nozzle better against the bottle. These work quite well with virtually no leaks.

Flight Record

Launch Rocket Pressure (PSI) Notes
1 "OO" 80 Maiden flight. Flight was very unstable, rocket flipped as low as a couple of meters above ground. Twin chutes did not deploy.
2 Spek II 80 Maiden Flight. This was our first flight with on board camera. Parachute deployed early, but this was expected. Great video and sound, camera survived landing.
3 TNT 110 Good flight. Parachute deployed well.
4 TNT 110 Good flight, nosecone came off after apogee, but parachute opened only ~2 meters above ground. Rocket didn't sustain any damage.
5 Jordan 120 Good flight, but arced over quite a bit and took a while to find it floating in the creek.
6 Brotanek II 120 Very high and straight up. Parachute failed to open but nosecone tipped over on the way down and caused rocket to go into a glide path and landed almost horizontally. Did not sustain any damage.
7 Brotanek II 130 Perfect flight, went very high and parachute deployed around apogee, landed well.
8 Brotanek II 130 Perfect flight, went very high and parachute deployed around apogee again.
9 Little Man II 120 Nice flight straight and high. Whistled well also.
10 Cena 120 Good flight and relatively straight. Had to dig out rubber nosecone from the impact sight. Bottle now getting a bit buckled.
11 Brotanek II 135 Good flight, parachute deployed after apogee, rocket travelled in a long arc. Highest pressure to date.
12 John John 110 Good flight, rocket spun axially (not designed to do that) and landed close to the launch pad.
13 TNT 120 Good flight, parachute opened just a bit too early.
14 TNT 130 Good flight, but the parachute didn't open. Only slight damage to the rocket but it will fly again.
15 Brotanek II 140 Great flight, went very high and the parachute opened around apogee. This was our highest pressure yet.

Notes to self

  • Rocket Maiden flights should be performed with extra precautions.
  • Bring a spare video tape.
Day 10 - In-flight Video and Faulty Nozzles
New improved "OO" with extended tail fin.
Slow take off.
Out of control Little Man II, just above the tree line heading back for the launchee.
Turning on the video camera inside the rocket.
Reviewing rocket footage at the scene.
Spek III with video camera taking off. This is a picture from the camera seen being held on the in-flight video.
On its way up.

Click here to see video.

toilet block and car park by the oval.
Oh look you can see the ocean. This was a surprise for us.
A high altitude shot of trees on the other side of the oval.
... hmmm...light pole.
Air Command Team looking up.
More ocean...
A nice shot of Manly and North Head on the horizon.
If you look carefully you can see us holding the cameras up. (see the shadow)
Looking out towards Warringah Mall.
More scenery.
...I can see my house from here....
Nosecone coming off....
A football match in progress on an adjacent oval.
Coming back down as the Air Command crew watch on.
Date: 20th August 2006  7:30am - 9:00am

Location: Denzil Joyce Oval. (launch site #4)
Where exactly is that? Click the above link to see a Google Earth place mark. What is Google Earth?

Conditions: Light cloud cover, quite cold temperatures, slight-moderate wind.


Name Capacity Notes
Little Man II 1.25 L Equipped with whistles. This one goes pretty high. Remained in the same configuration since last flight day - except for a new nozzle.
Spek III 2 L This was the same rocket (Spek II) as the last flight day equipped with a digital video camera  module. The ring fin was upgraded. 
Jordan 1.25 L The same rocket as last flight day. The rocket remained in the same configuration - except for a new nozzle.
"OO" 2 x 1.25 L This is a 2 bottle rocket joined at the base, with twin parachute recovery system. Since last flight day the fins have been replaced by a combination ring fin with flat fins. This resolved the rockets stability issues.
Brotanek II 1.25 L An older rocket that has flown a number of times. It remained in the same configuration since the last flight day.

Team Members: PK, GK, AK, Paul and John.

Number of launches: 12

This was a good day for in-flight videos and testing a new rocket. We brought a laptop, camping table and camping chairs for this event. Pretty soon we will need a small trolley to carry everything.

NOTE: The still images from the on board video contain a "ghosting" artefact. This is a side effect of the slow image scan of the tiny camera. This is particularly evident when the camera is slewing quickly. We apologise for the low quality of these images, but to bring you a higher quality image would require a more expensive camera, and we are not yet confident that it would survive more than a handful of landings.


  •  The first off the launch pad was the "OO" rocket. This was a really beautiful flight because it took off very slowly and proceeded to accelerate upward and then slowly began to arc over. Both parachutes deployed as expected and the rocket landed well. Upon video analysis it was discovered that the spray from the rocket had an unusual wide spread. This was most likely to have been caused by a new nozzle with a new seal. It will be interesting to try this rocket with the other nozzles we normally use.
  • Here is a video of "OO" taking off: (You may need to update your flash plug-in)

  • Water rocket twin chute

  • The second flight of this rocket had a similar flight profile except that the chutes failed to open, with one of them opening about 1 meter above the ground, but probably did not slow it down enough. The rocket only suffered minor damage and will fly again.
  • We fitted the new nozzle to Jordan (the rocket that is...) but it went out of control very early on. It recovered and then flew at quite a shallow angle towards our car. It missed it by only a couple of meters. The car was about 60 meters from the launch pad. At that time we did not know why Jordan had such an unusual flight profile since it has always performed well on take off.
  • Still not realising that we were dealing with a bad nozzle. (We only use a handful of nozzles and switch them between rockets as needed). We put it on Little Man II. Little Man II has also been a very straight flyer, but on take off it dramatically spun out of control and nearly hit Paul who was launching it. On video replay we saw the same unusual spray pattern. 
  • We thought that was unusual, but who are we argue? so we set it up for a second launch to see if the bad launch was a one off. You guessed it ... same thing again, but this time it almost hit me. I have great video footage of the rocket heading straight for me out of control, landing next to me.
  • Luckily we were only doing the camera flights next with Spek III and it used a different nozzle and so flew fine. We managed to make 6 flights in all with on board camera rolling. We brought a laptop for downloading the video after each launch so that we could clear the camera's memory. The flights were much more successful than last week as Spek III was fitted with a larger and better aligned tail fin. Launch #3 was particularly good and lasted in the order of 20 seconds.
  • Footage from this flight is available here:

    At left are the better still frames from these flights.
  • We had to shut up shop as people started arriving for football practice at around 9am.
  • Also on the very last launch the battery was giving out and so we couldn't fill the rocket all the way. It really surprised me because the battery was fully charged. Later we realised that we had been filling rockets with larger capacities and so they took longer to fill. I probably need to buy a second backup battery.

Flight Record

Launch Rocket Pressure (PSI) Notes
1 "OO" 100 This was a beautiful flight, it had very slow take off and curved over nicely at apogee and then both chutes deployed well to bring it to a nice landing.
2 "OO" 120 Another great flight with the same slow take off. the parachute opened 1 meter above the ground, but probably did not slow it down. Rocket will fly again.
3 Brotanek II 120 Good flight, chute opened well about 1-2 seconds after apogee.
4 Little Man II 100 This was a test flight with more water than normal. The rocket spun out of control. (Due to the new nozzle)
5 Little Man II 100 Normal amount of water, but rocket spun out of control. (Due to new nozzle)
6 Spek III 110 In-flight video, good flight.
7 Spek III 110 In-flight video, very good flight.
8 Spek III 110 In-flight video, ok flight, parachute deployed early.
9 Jordan 100 Out of control early, but recovered to fly horizontally a long distance. (Due to new nozzle)
10 Spek III 110 In-flight video, ok flight, parachute deployed early.
11 Spek III 110 In-flight video, ok flight.
12 Spek III 92 In-flight video, ok flight, parachute deployed early. battery ran down.

Notes to self

  • Rocket Maiden flights should be performed with extra precautions ... I really  mean it this time.

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