First trials of new staging mechanism

Over the last few months we have been slowly working on a new staging mechanism. On Sunday we spent some time completing it and running through some initial trials. We test fired it 3 times, at 60psi, 100psi and 120psi. We did the tests just in the back yard with only bottles connected rather than real rockets. We were pretty happy with the performance after a few adjustments.



Next we are going to build a very small second stage (~600mL), and a small booster - likely to be just a spliced pair of bottles. We want it fairly small so that it does not leave the local park. We want to see how it will go in flight before it is put on a bigger rocket with a bigger booster. This staging mechanism will eventually go on the Acceleron rocket, but could be used for a third stage on the Polaron rocket as well.

A full write-up with diagrams of the internal operation will be posted on our main site once we have done the test flights and had a chance to evaluate its performance. Weighing in at 94 grams it is a bit on the heavy side for small rockets, but for bigger rockets it won't make much difference. Acceleron's V's staging pod weighed in at over 400 grams, but also included the parachute bay.
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Weekend Work

We worked on a number of different projects this weekend. We started a small production run of nosecones with integrated deployment systems using the new V1.5 flight computer. The idea is to build a number of these nosecones into our inventory so that we can simply screw in a new one should one become damaged. This will allow us to continue development on new projects without the need to spend a lot of time on repairs.


We also fixed up the launch release mechanism on the medium launcher after a hairline crack developed in the riser air tube. We have replaced it with a shorter much sturdier pipe that can be unscrewed. We also built a couple of swappable release heads with integrated launch tubes. The release head fitted to the release mechanism (image below) is a standard 9mm nozzle. The other two release heads are 15mm nozzles one with a 26cm launch tube to go into single bottle or robinson coupled rockets and the other has a 112cm launch tube to be used with longer, Tornado coupled and FTC rockets.


We've also did some more work on the new staging mechanism, but mostly just epoxying parts together.

We've fitted the endcap and nozzle on a full length of FTC now as we really want to get this first FTC rocket test flown. It will be launched with the new long launch tube shown above. There is still quite a bit of work to do especially on the recovery system.
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Flight Computer V1.5

The full construction details of V1.5 are now available here:

http://www.AirCommandRockets.com/flight_computer_V1_5.htm

Features include:

• Dual RC servo motor control
• 7-segment LED display indicating status information
• Built in launch detect G-switch
• External launch detect / burnout / negative-G trigger input
• Buzzer for indicating status and helping to locate lost rocket in tall bushes
• EEPROM used to store settings while power is turned off
• 15 configurable control parameters
• Altimeter/auxiliary power connector

The update includes a short video of the operation, as well as circuit diagrams and PCB layout.
We've got 10 boards done now and are in the process of populating 5 of them with components. We'll be switching all our rockets to these over the coming weeks as we put this version through various trials.


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Polaron VI to 637 feet

We had another great day this weekend launching rockets at the NSWRA launch meet. There was a unique opportunity to launch during a fog to see if we could get video from above it, and we managed to get a personal best altitude with our Polaron VI rocket on another flight.

Full details, photos and a highlights video of the day is available here:

http://www.AirCommandRockets.com/day61.htm

Repairs and New Development

This past week we have been making repairs to the Polaron V rocket as well as doing some new development for Acceleron.

All the plastic retaining tubes have been removed from the Polaron V main stage. On inspection one other tube was cracked (other than those that were shredded) . Because of the forces involved we didn't want to take any more chances with plastic, so we replaced them with thin walled brass tubes. Although adding a little more weight, they should be up to the job. We will need to do some tests first though before giving them the all clear. We are giving the PL a week to fully cure. Other than the tube replacement the rest of the rocket and boosters are ready to go. The plan is to launch the rocket at the next NSWRA launch event in a couple of weeks time.

Acceleron has been mostly repaired with the exception of the staging mechanism. Over the last month or so we have been working on yet another staging mechanism, and with the repairs needing to be done for Acceleron's staging mechanism we decided to complete it and put on Acceleron IV. We still have a long way to go with it, and need to do more testing, but so far the development has been going well. I will post full details once it has flown. It is a lot more compact and lighter than what was used on Acceleron previously.

Since we are rebuilding the staging mechanism it was a good opportunity to upgrade the Tachyon sustainer. We are building a completely new sustainer that has ~30% more capacity, more streamlined shape and new parachute deployment based on V1.5 of the flight computer. The fin section now integrates a ring fin with 4 smaller conventional fins. The ring fin struts are made from 6mm carbon fiber tubing and act as supports for the sustainer during the boost phase. The sustainer also carries both the altimeter and camera. As of last night the pressure chamber (3.35L capacity) is now complete, as are the 4 fins.

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Good Day / Bad Day

The details from the last launch day have been uploaded to the main site:

http://www.AirCommandRockets.com/day59.htm

Although it was a less than optimal day in terms of requiring repairs, we had a great day launching with other NSWRA members and even reached our highest directly measured altitude. With the same flight we also achieved our longest duration flight.

Repairs are already underway, and we are looking forward to the next launch day to fly Polaron V again.

We have also added a size comparison rocket gallery of our rockets built to date. You will need to have a flash player installed in your browser. Just roll the mouse left or right over the screen to scroll.
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Our First FTC pressure tests

We did our first T-8 FTC pressure test this weekend. Over the last two weeks we made up a 15 mm nozzle and an end cap that fit exactly inside the FTC. The nozzle is a standard 15mm Gardena style nozzle but one that comes with a threaded section. We made an adapter that allowed us to screw in the nozzle. The adapter has two grooves in it, one to hold an O-ring that seals against the FTC and the other allows the tube to be shrunk to stop the nozzle from flying out. We wrap some wire over the shrunk groove to keep the nozzle in place.

The inspiration for this retention setup came from Urie's water rockets. They have good photos of the nozzle and a good description of the technique.

When we tried to shrink the nozzle end by heating it with a blow torch, we forgot the fact that other parts of the FTC were also going to get heated. *doh* We ended up buckling a part of the FTC near the nozzle. Since this was only going to be a pressure test we didn't really care. Mind you when we were sealing up the end cap we filled the FTC with water, and that went a lot better.

The burst pressure was 190 psi (13.1 bar). The nozzle and end cap stayed in place so we were happy about that. This FTC is really thin walled compared to another length of FTC we got from Damo quite a few months back. The next test will be to wrap some of the glass strapping tape around it and see how much more *crossed fingers* it will hold.

You can see on the left edge where the FTC split.
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Flight Computer Q & A

Over the last year we’ve had quite a few questions about our water rocket flight computers so I’ll try to answer some of the more common ones here:

1. Why do you need a flight computer, wouldn’t a Tomy Timer do the same thing?
   
   When you only need a one-shot timer, we always recommend a Tomy Timer as they are inexpensive, you can get them anywhere, there is no need for batteries, very simple operation and light-weight. They are also a proven design.
   
   We wanted to be able to do more than just deploy a single parachute. A PIC-based micro-controller is an easy way to gain more functionality. Electronic timing is typically more accurate and repeatable compared to mechanical systems. You can also set very short timing delays for things like staging, something difficult to do with a Tomy Timer. There are elaborate mechanical systems that have been built that require no electronics that achieve the same thing.
   
   A flight computer can have: data logging capability, can control multiple actuators and have in-flight data processing and signal conditioning capability. If you wanted to experiment with active stability, or gather engineering data, it is difficult to do with a Tomy timer.
   
   
2. Isn’t it much heavier than a Tomy Timer?
   
   With our current design when you add the battery, servo and the flight computer it is perhaps 4 or 5 times heavier than a Tomy Timer. However, we use the battery for both the flight computer and the altimeter, so we save weight that way. The same battery could power the camera as well so you could save weight even further. We haven’t shared the power between the cameras and the flight computer yet.
   
   If you were to use a small lightweight battery such as the 4LR44, a 4.5g micro servo and surface mount components on a small PCB it could weight about double that of a Tomy imer.
   
   This weight difference translates to perhaps 10-20 feet altitude loss on small rockets and negligible on larger rockets.

3. Why do you call it a “flight computer” and not a “timer”?
   
   The terminology distinction is purely internal to our team. That way we differentiate between our simple electronic “timers” usually based around a 555 or 556 timer and the PIC based ones that have software running on them. Once the flight computer starts processing real-time flight data, the distinction will be more obvious.
   
   
4. Does it do more than timing?
   
   The published versions of the flight computers mostly do just timing. Although through software they also drive the LED display, do switch de-bouncing and generate the correct PWM signals for the RC servo motors.
   
   
5. Are you looking at adding more functionality?
   
   We have plans on our roadmap to add more functionality, but we are taking it one step at a time, experimenting with what actually works in the field what doesn’t. Take for example the various G-switch designs we’ve been testing. This involves multiple flights which takes time.
   
   
6. Does your current flight computer control your camera and altimeter?
   
   The published ones and flown to date have not. The altimeter is powered from the same power source as the flight computer. The Z-log altimeter can be set up to start recording 10 seconds after power-on which means when we turn on the computer, power is also supplied to the altimeter and it starts recording. But there is no direct control between the altimeter and flight computer.
   
   The V1.5 design has a free port left open to allow the altimeter to be connected to the flight computer through a serial connection. The Z-log altimeter outputs altimeter data continuously over its serial port. However, even V1.5 will not initially have it connected.
   
   The plan is to feed this altimeter data to the flight computer and it will be able to monitor the altitude and deploy parachutes at preset altitudes or when altitude starts decreasing after apogee. The flight computer will always use the timer capability for backup should something go wrong with the altimeter. At the moment we are working to make the timing as reliable and usable as possible before adding more complex functionality.
   
   It was always our intention to wire the old cameras to the flight computer so that they could be turned on by the computer just before launch since they only had 30 seconds of record time. However, ever since we bought the new FlyCamOne 2 video cameras with their 30 minute record time, the flight computer/camera integration took lower priority. We start the camera separately before we pressurize the rocket.
   
   
7. Do you have designs that you are keeping secret?
   
   No. We have no reason to. We only publish the designs once we have flown them a number of times. We like to verify the designs for ourselves before making them public, as it is much easier to fix things before publishing than having to make retractions or corrections later. We find it very useful in making the designs public as other rocketeers help suggested ways of improving them.
   
   We have already been contacted by 2 rocketeers that have built the flight computers based on our published designs, so we want to make sure we have confidence in the design before they are made public.
   
   
8. Isn’t it expensive?
   
   Not really. The PIC controller costs AUD$2.84, the handful of discreet components around $10, the batteries are about $3 and the cheap 9g RC servos we get for around $6 each. This means with a PCB the whole electronics ends up costing in the order of ~$25. That is about 1/4 of the price of the camera and about 1/5th the cost of the altimeter.
   
   Of the ones we have crashed we have been able to reuse most of the parts. Really the only things that do brake are the PCBs, the old G-switches and servos. We have now learned to protect the servos better and have had 2 survive direct impacts since the change.
   
   
9. Will they be available for sale?
   
   There are currently no plans to sell them in any great numbers as there really isn’t a market for them. Most water rocketeers prefer to build rockets out of inexpensive components. Personally I’d rather be flying rockets than handling order paperwork, chasing payments, etc. etc. We will likely offer 5 of the V1.5 for sale privately at cost price. (Contact us if you are interested - see contact page on our main site) The others we will continue to use for our experiments.
   
   
10. How reliable are they?
    
    So far we are having relatively good success with deploying parachutes and staging 2-stage rockets with them. All together there have been 68 flights with on-board flight computers, of which 5 failed to deploy and 2 successful deploys but tangled parachutes. This means as part of an integrated recovery system they are about 90% reliable.

11. What will be in the next version?
    
    V1.5 of the flight computer is the next iteration we are working on. This version has dual servo capability like V1.4, a loud buzzer for status feedback and helping to locate the rocket lost in tall grass or bushes. One of the new capabilities is that all the timing parameters are configurable in the field and stored in the on-board EEPROM to retain them after power is turned off. There are 15 parameters that are configurable from parachute/staging delays, to multiple servo positions, to the lost rocket sound alarm delays. We are having 9 more PCBs manufactured for this particular design as it makes it more compact and lighter.
    
    
12. 

12. Future plans?

Eventually we would like to miniaturize it and use all surface mount components and a much smaller PCB. The final weight and size should be similar to the altimeter (~10grams), although realistically this is at least a year or two away.

Adding logging capability will also be a priority in the upcoming months. We have ideas for air speed sensors that could be used to detect apogee, but have no idea how well they will work or what the data will look like. The idea is to use the normal timing for recovery, and the logging capability to capture data over multiple flights. We will do this for each type of sensor so that we can see what processing will be needed before it can be used effectively for apogee detection.

None of these plans for the flight computer are set in stone and are likely to change along the way. We only work on these during spare time and as a result the development is drawn out.

There have been many people who have flown flight computers on water rockets over the years, many of them a lot more advanced and using accelerometers, logging capability, running science experiments etc. The oldest documented reference I have found is back from March 2000.

Updated:

The following quote reproduced here in full is taken from a long exchange from the WRA2 forum and is included here because apparently we did not credit Bill with the invention of a water rocket flight computer and that we "stole" the idea from him. (See previous paragraph) In his own words:

Team Seneca Post subject: Posted: Tue Apr 15, 2008 12:13 pm

WRA2 Member
Joined: Sun Dec 31, 2006 4:40 pm
Posts: 97
Location: Seneca, N.Y.

It's not hostility. It's just that I never knew you guys would be so impressed with an electronic timer with a fancy name. I've put real computers on my rockets since the summer of 2005. A computer that does something too, not just a timer. I use an accelerometer to measure the flight and deploy. Back then I also used it to send signals to a small camera to take a snapshot at apogee. I'm the first one to put a computer on a water rocket and it was a real computer, not a tomy timer made from silicon.

_________________
Bill W.
Team Seneca

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Polaron V Preview

Almost completed Polaron V. The main stage is close to 11L and uses a 7mm nozzle and jet foaming to produce a long a sustained thrust curve. The boosters are ~3.35L each and use a 13mm nozzle and normal water to get the main stage up to speed.

(Click on the images to enlarge)

The lower photo shows the detail of where the parachutes are stored on the boosters. It is difficult to see the clear strap holding them in place. A wire connected to the main stage releases the strap and the parachutes can fall out. In theory anyway. We are hoping things don't get tangled on release as there will be three wires hanging from the rocket, parachutes popping left right and center and the clear straps are spring loaded so they will also be in amongst the action.

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Quick update

We've been progressing this week with the Polaron IV upgrade. The booster parachute deployment mechanisms are now finished on all three boosters.

I made an extra reinforced bottle for the main stage, but after gluing and heat shrinking I noticed that the coupling was sitting at a bit of an angle. This would have resulted in bent rocket, so I tried to straighten it, but instead of improving it, I managed to break the coupling. :( So I threw that bottle away and had to make up another one. The whole process takes about an hour to reinforce the bottle. We are waiting for the glue to cure before we do a full pressure test.

We've reserved Friday for a full pressure test of the new main stage and new boosters as well. If the weather is favourable we'd like to fly it on Saturday.

We also did some experiments this week in creating foam in a bucket by blowing air through a sintered metal filter into the bubble bath solution. The tiny holes help make foam more readily. We want to try generating foam on the pad to see how it compares with it generated in the air. The main observation was that if the air flowed too fast then the bubbles would re-combine into larger ones, but a slower rate created more smaller bubbles.

There have been some really good discussions on the Yahoo Water Rocket forum this week regarding internal temperatures. It may help to explain why we have had some unexpected failures of the bigger boosters under test. I'll cover this in more detail in the next web update.
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Progress Updates

We have updated our main site with a few more details of what we've been up to in the workshop. The update also includes some great pictures from the last launch day taken by Andrew from NSWRA.

The update is here: http://www.AirCommandRockets.com/day58.htm



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Tornado Couplings

This weekend we finally managed to produce a number of good Tornado couplings. Tornado couplings connect bottles neck to neck. These one's are easy to make out of gardening supplies from the local hardware store.


Some features:

• They have a 15mm hole
• Weigh 13 grams
• Require no glue
• Have been tested to 130psi, but can most likely hold more.
• Require no special tools
• All plastic construction - no metal.

We have been wanting to make these cost effectively for a while now since we plan on using lots of them to join the spliced pairs of bottles. We will give full construction details in future updates on the main site. We want to put them to use first on the Polaron IV boosters to extend their capacity by another bottle each.

We are also currently working on another staging mechanism design that will be hopefully a lot lighter than the one we have been using on our two stage rocket. Since we are still in the early stages of development, we will describe the design later, once it is more finalised. We have lots of testing and prototyping to do still.
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2 Stage flights

We had a great weekend launching our rockets at the NSWRA launch event. We flew our newly rebuilt 2 stage Acceleron IV rocket up to 525' (160m). We also flew the Polaron IV rocket with drop away boosters to 510'.

The full update with photos and highlights video is available here:

http://www.AirCommandRockets.com/day57.htm

Here is an panorama from around 500' as the rocket pitched over at apogee.
(click on the image to enlarge)

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Acceleron IV progress

We spent this weekend working on the Acceleron IV booster getting it back into a working state for next week. We did a pressure test to make sure that everything is still fine, but we found out that the rocket was not holding pressure at all. We pretty quickly discovered that three of the Robinson couplings were missing their seals. Ooops. When we put those back in and everything checked out okay. We must have missed them during preliminary assembly.

We only pressure tested the rocket to ~100psi since the neighbours were out in their back yard, and having had this rocket fail a pressure test in the past, we didn't want to push it. We did have the video camera recording though just in case. The rocket will most likely get launched at 120psi on the day. The rocket theoretically should hold up to around 140psi operational pressure, with a burst pressure of around 180psi.

We hooked up all the electronics and and made sure the staging still worked when the pressure in the rocket dropped. We replaced the sustainer in the test with a small bottle full of water which fired as expected.

We replaced the rubber bands in the staging mechanism as keeping them stretched all this time in storage caused them to deteriorate quite badly. The same went for the wide rubber bands that held the fins on.

The booster segments are now attached with velcro straps which makes it a lot easier to service the segments.

The launcher has also had an upgrade with new longer fill tubes that allow us to use the spliced pairs of bottles on the bottom of each segment.

Some work has also been done on the sustainer. The altimeter has been moved into the space between the bottles which should help protect it. The altimeter is attached to the inter-bottle ring and having its own power supply allows us to swap it between rockets. We still have to re-attach the fins to the sustainer and also mount the new FlyCamOne2 camera to the payload section.

If we get time this week we also want to finish building a reinforced rocket that should be capable of around 180-200psi. It is only a two 1.25L Robinson coupled rocket but we are including the baffle we made a few months back to prevent the blow through effect with this rocket. The higher pressure would only make it worse.

We also made a couple of rocket carriers that help us transport and protect the rockets. They also help prevent the rockets from sagging in warm conditions.
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Flight Computer V1.5

Last night I finished soldering up the new board for the latest flight computer. Everything worked as expected which is good, and we will fly it soon.


The large bright LED display allows you to stand back from the rocket while it is pressurised and ensure the correct settings are set. It also has a small buzzer that allows you to hear whether it is armed or not while standing back.

A little more software needs to be written for the flight computer to support the new functionality. The intention is that the code base will be universal enough to be used for regular water rockets, but also for multi-stage, or dual-parachute.
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Launcher Details in 3D

We spent this weekend documenting our Polaron IV launcher and rocket. We've produced an explanation video of how the launcher works as it is much easier to explain the configuration.

The details are available here:

http://www.AirCommandRockets.com/day56.htm

The update also includes a number of anaglyphs of various parts that you can view in 3D using regular red-blue 3D glasses.

Click on the image to enlarge.
You will need red-blue 3D glasses to see this image properly

Also a quick update on flight computer V1.5 - We received our first PCB this week so we are keen to solder it up and see how it performs. If no changes are required we will get another 9 PCBs made so that we will have total of 10 flight computers ready to go for the up coming experiments.

The new flight software is also progressing and should be finished within the next couple of weeks. Once the flight computer has had a successful couple of test flights, we will publish the full design again, including the PCB layout.

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Parachutes

After a short break last week to catch up on non-rocket related projects we are back in full swing again.

We ordered some great lightweight ripstop nylon parachute material from the UK this week. It was comparatively cheap at only AUD$32 delivered for 10m x 1m of the stuff. It is a nice orange that should make it easily visible. From the time of order to delivery it only took about 6 days to get here which is pretty fast considering it had to go half way round the world.

We want to make a new lighter parachute to replace the one on the Polaron rocket. The parachute will weigh less than half the weight of the existing one, and also use up about half the space. For the shroud lines we are going to use TigerTail - a very strong light-weight line typically used for making necklaces. It is stranded stainless steel cable coated with nylon. It is very light, doesn't kink, is only 0.3mm thick and has very high tensile strength. This will allow us to make a strong parachute and should pack into a much smaller space.

If this parachute goes well, we will most likely make up more parachutes for the other rockets, including Acceleron.

We have also been doing some more work on flight computer V1.5 and hopefully the prototype should be ready soon. We are getting a number of PCB boards made up so it will take up minimal space and weight. Once finished it will be used on all of our rockets as it is capable of driving two separate servos and has a few more nice features compared to the previous version.

I turned off comments here on blogger (temporarily) due to excessive amount of SPAM last week, so if you would like to ask questions, just visit the main site and go to the contact page.
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Polaron IV Boosted flights

We had a great weekend of flying the Polaron IV rocket with the drop away boosters. The boosters behaved exactly as expected and gave the rocket a nice kick on launch.


The on-board video also turned out great.

The full details of the launch day with lots of pictures and video of the highlights is available here:

http://www.AirCommandRockets.com/day55.htm




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Successful Booster Test Flights

In preparation for launching Polaron IV we wanted to make sure that the whole launcher will work with the boosters and the main stage all together. We weren't sure if it would come off the launcher cleanly, or if the boosters would fall off, or how the new guide rail would go.


We built a dummy main stage out of old bottles and an old nose cone that used the nosecone-off-at-apogee technique for deploying a parachute. The main stage only had the bottom 2 L bottle pressurised. And had 1.5L of water in it so virtually no air. We added a little ballast into the nose in the form of a zip-lock bag with water in it.

We had two successful vertical take-offs with the boosters all falling off almost simultaneously on both occasions. The boosters were filled with 1L of water and everything was launched at 100psi.

The dummy main stage weighing in at close to 800 grams was still able to reach ~80-90 meters
The parachute opened on the first flight right at apogee, and failed to open on the second flight.
The dummy main stage was destroyed, but luckily all the bits we needed for the Polaron IV rocket survived. The boosters also survived their tumble recoveries.


We proved to ourselves that this particular launcher and booster concept works, and so we are hoping to get at least one flight out of the Polaron IV rocket on Saturday. There are always things that can go wrong on the day, but we will worry about those when they happen.

We have also finished repairing the Hyperon and J4 rockets, so we will have those as backups on Saturday as well.

Full details of the days events with videos of this booster test will be again published on our main site after the launch day.
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Launcher Completed

We spent most of the day in the workshop again today. We are really pushing hard to get Polaron IV and its launcher ready for the next NSWRA launch day. It is only 6 days away.

We did finish the launcher today, which I am really happy about. It now sports a single 2m launch rail. The rocket will use launch lugs to hold onto the rail. We had to switch to this system since there really isn't room for the 3 guide rails we have been using. We ended up using 2 of the feet and guide rails from our medium launcher to support the new launch rail which really reduced the amount of stuff we had to make. The legs are still usable on the other launcher so the nice part is we have less hardware to carry with us when we take both launchers.

We are now finishing off the rocket and the booster retaining mechanisms on the rocket, and then it should be ready to fly. If there is a nice launch opportunity between now and Saturday we may try the boosters with the dummy main stage at our local park.
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Splicing Bottles and Pressure Tests

The weather hasn't been too co-operative this weekend so we spent quite a bit of time in the workshop. We have updated our main site with the latest developments here:

http://www.AirCommandRockets.com/day54.htm



The update includes a video tutorial into how we splice our bottles. It also includes an update on the progress of our Polaron IV rocket, and the Acceleron IIIb booster.
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Glueing and PCB layout

Splicing and Couplings

This week it's been a bit of a mixed bag. Now that we have the PL Premium glue, we are gluing together pairs of 1.25L bottles. These glued sections have a thread at either end allowing us to join them to other sections. We have 6 made up, and two more will get made today. They will be used in constructing boosters and rockets bodies as well.

To join these together we have also been experimenting with making simple "Tornado" couplings. We are still waiting for the glue to dry before we do a full pressure test. We've made up four of these so far and if they work well, we have the materials to make a lot more. They weigh around 7 grams. The other nice thing about these couplings is that they have a 19mm hole which is about 6 times bigger in cross sectional area than the Robinson couplings we have been making. This leads to better internal efficiencies and also means we can put a long 19mm launch tube through them.

The simulator predicts well improved altitudes for rockets made out of the spliced pairs and the tornado couplings.

Repairs

We have also been doing repairs to the two crashed rockets from last week. This will require a little more work since the nosecones and deployment systems need to be rebuilt.

PCB Layout for Flight Computer V1.5
As a part of making life easier when doing repairs we have been finalising the PCB layouts for the next iteration of the flight computer. We are going to do a small run of these PCBs and make up a number of the computers so that we can quickly replace them should they become damaged. The board will be about 43mm x 55mm in size or about 30% smaller than what we have been making on the prototype board. It will have dual servo motor outputs making it suitable for single and dual stage rockets. It also has a buzzer for audio feedback of mode changes as well as helping to locate it in tall grass.

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Launcher Pressure Test

In the last few days we've pressure tested the Polaron IV launcher to make sure there are no leaks. There are a lot of connections and we were not sure how well the seals would seal around the plastic compression seals around some of the copper manifold pipes.

All was good and we took the pressure up to 215 psi ( ~15 bar ) for both the main stage line and the booster manifold.

When pressurising, we really have to think about what valves get open or closed and in what order.

For the first launch the pressures will be in the order 110 - 130psi.

We made dummy plugs for the booster nozzle seats for the test. This allowed us to test that side of things without having to put the boosters on the launcher. We fitted a strapping tape reinforced small 300ml coke bottle to the main stage release head and used the 7mm aluminium nozzle that the main stage will use. All held up well, and we tested the bleed valves
for both the main stage and the boosters with success.

We are now working on the booster retention mechanisms and getting those attached to the boosters and main stage.

The update from last Saturday's launch event is also now available on the main site:

http://www.AirCommandRockets.com/day53.htm

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NSWRA and Polaron IV Main Stage

Yesterday was a fantastic day for rockets. We are now members of the newly re-grouped NSW Rocketry Association (NSWRA) and went to one of their launch events at Doonside. There were many rockets flown on the day and we got a chance to fly three of ours.


We ended up finishing the Polaron IV main stage rocket at about midnight the night before and so we got a chance to test it. We flew it twice with the full payload (new camera, altimeter and flight computer). Both flights were very good and the new parachute also worked well.

The Polaron IV rocket is now pretty much ready to be fitted with the boosters and ready to go. We will probably run some tests first on the boosters being launched from the new launcher with a dummy main stage.


Full details of the flight day will be published shortly with pictures and videos.

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Black Tape and Sun

As I was inspecting a couple of our rockets last night and getting them ready for tomorrow's launch day, I noticed that the bottles were warped in a couple of places. It appears that the warping was most severe where the wide black tape was. This also occurred on the unpressurised sections of the rocket.

This was likely to have been caused during the last launch day when we left the rockets sitting out in the sun for a couple of hours. The heat absorbed by the tape was enough to shrink the bottles a little under the tape.

This is likely to occur to other rockets that are painted in dark colours. I think we will be storing our rockets in the shade from now on, and perhaps switch to lighter coloured tape when the black stuff runs out.

I spent most of the last couple of nights trying to get the Polaron IV main stage ready for flight on Saturday. The payload section now has the new FlyCamOne camera built in, the Z-log altimeter, servo motor, batteries and a newly built version of our flight computer (V1.3.2). I just have to attach the door and latch mechanism to the payload bay and then attach the whole thing to the rocket body.

We want to test fly it by itself to make sure all the systems and recovery works before we attach the boosters to it.

If we do get to fly it this weekend, I will post pictures soon after that.
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Booster Tests and Launcher Details

We've updated the main site with the latest details of the Polaron IV launcher and the new Gluon boosters.
The name Gluon was chosen because it continues with the sub-atomic particle naming convention we have been using for our rockets and also because it is our first operational spliced rocket using PL Premium glue.

The update can be found here:

http://AirCommandRockets.com/day52.htm

The update also includes a video of the booster tests. It's not overly exciting but included for those who are interested.

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Launcher and Booster Tests

We've had a very productive weekend this week. We completed the majority of the new Polaron IV launcher, spending about 8 hours in the workshop on Saturday.

The image below shows the state of the launcher currently. I will do a full update this week and post it on our main website that shows all the details and discuss some of the design issues.

On Sunday it was too windy to launch regular rockets and so we opted to do a number of booster test launches. We fitted a booster with a regular nozzle and launched it from our medium launcher. The main aim of the test was to see how the booster behaved in flight and how its recovery system would work. Full details of the booster will also be posted with the next web update.

The larger parachute is now finished for the Polaron IV rocket and the payload section is also well under way. With the altimeter, flight computer, and video camera, the payload section alone is worth around $300. Hmmm... I think I will add a padded nosecone extension for protection in the trial flights. This padded nosecone will be removed for the higher performance flights once the design is proven.
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Holidays over

Having been OS for the last 3 weeks the holidays are over, and we are back in full time production of the Polaron IV launcher and rocket. We are concentrating our efforts on this in order to get it done as soon as possible. During the holidays dad machined up a lot of the necessary components for the launcher, and now we are pretty much ready to start assembling it all together. Dad also did a bit of work around the workshop putting up some new shelves and fixing a few things making it easier to do development.

The Polaron IV rocket will also be fitted with one of the new FlyCamOne cameras as well as the altimeter. I am weighing up whether to build the next version of the flight computer for this rocket or just use one of the existing ones. I may use V1.3.1 in the first few trials and then upgrade when the next version is finished.

This weekend looks like weather is not going to play ball so workshop time is in order. Hopefully we can get most of the launcher done.

This launcher is intended to take us up to the next level in rocket pressure and size. We eventually intend to be launching reinforced rockets from this launcher and hence it is being designed to handle 35bar (500psi) operational pressure. It will support both single nozzle rockets as well as rockets with 3 boosters. The booster nozzles can slide in and out allowing us to used different sized boosters and main stage.

I'll take some pictures over the weekend of the launcher and post them here or on the main site.

PL Premium Glue

We still have a number of tubes of 10oz (300ml) PL Premium glue available so if anyone in Australia is interested please let us know. Just email me: katz.george at gmail.com.
The tubes are AUD$8 each + shipping from Sydney. Standard postage rates apply. You can check the Australian Post office website for shipping charges.


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Katz Stager and new cameras

Katz Stager

While developing our regular rockets we have been working on a new staging mechanism in the background - the Katz stager. We normally don't release details of concepts until we test fly them, but since it's been a while that we've done an update I thought I'd include it. We have built a prototype and test fired it a number of times by hand, but it is still to fly and at full pressure.


The full details of the stager and photos of the prototype can be found here:

http://www.AirCommandRockets.com/day51.htm

New video cameras

We have also bought a pair of FlyCamOne V2 video cameras this week. So far we are very happy with the functionality and performance of these cameras, and are looking forward to mounting them inside rockets and flying them. They can record video at 640 x 480 resolution @ 25fps with sound, which is not bad for a 37 gram package. Recording onto an SD card allows you to get up to 30 minutes of video. Compare that to our existing cameras that record 320 x 240 @ 15fps and can only capture 30 seconds of video.

The other nice feature is the optional external power supply, the swiveling lens+sensor for minimal drag in the air stream and external shutter contacts to allow a flight computer to trigger recording or take 1280 x 1024 pictures.
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Fire and Water details available

We have updated the main site with the details of the launch event from last Saturday. The update includes a video of the highlights.

http://www.AirCommandRockets.com/day50.htm

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Fire and Water

We had a great launch day event yesterday. We met up with a couple of pyro guys from the Australian Rocketry forum and the weather at the new launch site co-operated as well. We did a total of five flights (all with on-board video) and they too launched a number of theirs. We also did a combined effort and strapped our video camera to the side of one of their rockets. It's interesting to see how similar the view is from both types of rockets, especially when using foam in the water rocket.

I was fascinated to see their pyro rockets close up, and the preparations needed to get them going. The pyro rockets sure are a lot less messy. Ultimately the same parameters apply to both disciplines in terms of drag, stability, thrust etc.


The new George Kendall Reserve launch site was also very good. There were only a few people about and the clearance range is greater compared to our usual launch site. Being only about 35 minute drive from home is not bad. It's definitely a place to test the next stage of development.

Over the next few days I will do a full web update with photos and videos again.

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Polaron IV progress

We didn't get to fly this weekend due to the adverse weather conditions, but at least we made progress on the Polaron IV rocket. The 8L rocket main stage pressure vessel is now finished, with reinforcement of the bottle bases based on the technique described during our last update. We had to machine up a new base to base coupling that was longer than normal because it has to go through 4 thick PET walls with washers in between. When we now heat shrink the reinforcing sleeves, we fill the inner bottle completely with water and pressurise it to about 15psi. We also use a blow torch set to a low flame to get better control over the heating location.

We have yet to pressure test the main stage, but I am hoping that 130psi will be a safe launch pressure. After a couple of failures at 120psi of similar Robinson coupled 2-liter bottles, we have been reluctant to push the pressures much higher. Hopefully this reinforcement technique will allow us to do that.

We have also started modeling some of the launcher components and staging mechanisms in 3DStudio Max to get a better idea how it's all going to fit together. It also allows us to check for clearances before cutting any metal.


Dad has also prepared hoses and another pressure regulator that goes up to 25 bar (~360psi) with the associated high and low pressure gauges. This will allow us to launch a rocket with a different pressure to that of the boosters. This way we can optimize the performance depending on the structural integrity of the different elements.
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Polaron IV boosters

We have been working on Polaron IV and its launcher in the background while doing the foam experiments. We have further refined plans now on how the boosters will be attached and how they will separate. The photo above shows three newly machined 13mm aluminium nozzles for the boosters.

Each booster is 90mm wide, 2.3L capacity weighs ~150grams dry including recovery system, has a 13mm nozzle and uses a 450mm launch tube.

The simulator predicts that individually each booster should reach about 130m (430') @ 120psi, however, each of the boosters is intended to lift an additional 900 gram weight. This additional weight being a third of the total weight of the main stage fully loaded with water. Under these conditions the predicted altitude of each booster is around 35m (120'). Giving the main stage a release velocity of ~ 25 m/s.

The calculation gets a little trickier because the main stage also fires at the same time when boosters are launched. Though the main stage only uses a 7mm nozzle and foam so that the overall thrust from the main stage will be much smaller compared to the boosters. The consequence of this additional thrust from the main stage means that each booster has less to lift and therefore will be released at a higher altitude and higher velocity. We will do these additional
calculations when we finish building the main stage and know its parameters in detail.

At 120psi, each booster will produce around 90N of thrust at release and about 190N at the end of the launch tube. That is a combined booster thrust of around 570N as the rocket clears the launch pad. Compare that to the Main stage that will produce around 55N thrust with water only and likely around 35N with foam. From static experiments we found that the main stage should thrust for about 6-7 seconds. Rough estimates for main stage altitude are around 230m (750') at the 120psi level. Actual flight though may vary from this figure if the rocket does not go vertically.

The launcher under construction will have two separate air supply lines allowing us to use different pressures in the boosters compared to the main stage. This should allow us to experiment with a wider variety of rocket configurations. Full plans will be published once the design is finalised and the rocket is tested.
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Foam vs. Water-only flight test results

We have updated our main site with the results of the foam vs. water-only test flights.

http://www.AirCommandRockets.com/day49.htm

In the analysis we show that foam flights were about 2-3% lower in altitude than the water only rockets. This was a little dissapointing but also encouraging in other ways and certainly gives us a direction for further research with foam. Since the update We tweaked the simulation's drag coefficient and nozzle loss factor so the simulation matched the highest observed water-only flight altitude. We then added the weight and drag of the attached camera, upped the pressure to 120psi and ran the simulation again. The predicted water-only altitude was 350'. The last camera mission on the day was a foam flight with the camera and the altimeter. The altitude measured was 353'. This would put foam on par with water-only.

The altitudes are too close together to be able to make any definitive conclusions one way or another, and a lot more flights are required.

There are a few reasons we want to pursue foam experiments further:

1. It's a lot of fun.
   
   
2. The residual foam weight issue, described in the update, could point towards a measurable advantage when solved.
   
   
3. These tests were only carried out at low pressures, enough to get the rocket off the ground. As the pressures increase, the take-off and peak velocities will also increase. Due to the difference in velocities between water and foam powered rockets (water = faster & shorter burn, foam = slower & longer burn) the difference in drag will play a more signigficant role since drag is proportional to the square of the velocity. This should favour foam at higher pressures.
   
   
4. Convergent/Divergent (DeLaval) nozzles are yet to be fully analyzed. Although initial tests showed them to be no better at low pressures, higher pressures and nozzle shape optimization are still yet to be tested.
   
   
5. Use of foam may be more optimal for upper stages of a rocket than for the main stage. More simulation is needed.
   
   
6. Efficient generation of foam. From foam thrust measurements we found that foam generated using the Jet Foaming technique produced about 14% less total impulse. We have yet to test alternative ways of generating foam that may be more efficient. A couple of new foam generation ideas are already on the drawing board.
   
   
7. Foam optimisation. So far we have only been using the same ratio of bubble bath to water when mixed, but other combinations will need to be tested.
   
   
8. Different foaming agents. So far we have only tested kids bubble bath to generate foam. There are much better foaming agents available and foam density and viscosity are likely to play key roles in the efficiency.
   
   
9. The test results from all these experiments and data from other rocketeers may be used to build a foam simulation model for further research.

If all the above issues can be optimised for a particular application, then it still may turn out that foam can have higher performance in particular situations.
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Great Flight Day

We had an excellent flight day on Sunday. The weather was ideal and none of the rockets crashed. We tested the water-only vs foam flights and got altimeter data for all of them. Virtually all the flights were vertical.

I am in the process of doing a full web update but it will take a day or two to collate all the data and get the videos updated.

The update will also cover bottle reinforcing techniques and their results.

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Flight Computers & Misc

Most of this week has been spent working on a new design for the flight computer. As mentioned in the web update a couple of weeks back, we want to make it more automated to enable remote operation. We are building our own IR remote so that we can have full control over its operation. Most of that hardware is now designed and part of the remote's software has been written.

The new flight computer will not have any buttons except for the power switch, instead it will have the IR sensor module. It will also have a small speaker to acknowledge mode changes as well as serving as a recovery aid should the rocket fall in tall grass. The flight computer will also support two servos for staging and recovery as well as the capability to support the Zlog altimeters. The flight computer will be able to start the altimeter recording once the flight computer is armed.

Most of the design for this new hardware is now complete, with about half of the software still to be written.

We have now repaired J4III's body and fins, and are in the process of remounting components in the payload bay in order to protect them better during impact. J4III will now also sport the new shock absorbing nosecone to help provide even more protection should the parachute fail.

We have also made our first jacketed bottle that includes a Robinson coupling. We have pressure tested it to 100psi to check for leaks around the coupling, but will need to burst test it to see how much it can actually hold. If the burst tests are successful we would be aiming for launch pressures of around 180psi. While we believe the bottle burst pressure will be around 220psi+ the Robinson coupling is the biggest unknown.

If the weather holds up this weekend we will try to go back and do the foam and water comparison flights.
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Progress

This week we continued working on the stager mechanism. We finished enough of it to test it staging just in the back yard. We used only air at 20psi a couple of times and at 50psi once. Although it worked it was a little stiff to release and that is something we need to look at. We will probably try softer o-rings first. We still have a major design issue to resolve, but have some ideas. (More on this later)

The camera that wasn't behaving during the last launch day appears to be OK, and the cause looks like a poor battery contact. The contacts must have become more compressed inside the camera. We tried it with another battery that has taller solder blobs on the contacts and that worked fine, even when shaking the camera.

We also had a go at building the first prototype of the shock absorbing nosecone. It basically consists of the top 3/4 of a PET bottle which is filled with soft foam. The sides of the bottle have 8 longitudinal cuts all the way around that allow the bottle to easily split and slide over the existing nosecone. It is lightly taped over the top to enable the tape to separate easily on impact. During a crash the padded nosecone slides down and the foam compresses against the internal nosecone, but also the whole thing acts as an air piston to dampen the shock even more. The prototype weighs 35 grams so not a very significant weight penalty. For record flights, this can be removed and the existing nosecone underneath can just be used.

We have also been on the lookout for new launch sites around Sydney with great help from the local rocketry community. We looked at one location (George Kendall Reserve) that looks pretty good and is only about half hour from home.

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J4IIIb crash and foam flights

This weekend we were going to test performance differences between foam and water-only rockets, but after crashing the rocket on the third flight, we went back to just launching another one for fun. The altimeters are working well for us and I am happy with their performance.

The full update is here:

http://www.AirCommandRockets.com/day48.htm

This update includes a highlights video for the day.
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Polaron IV development & Hybrid Splice

Since the weather has not been favorable this week, we have been doing further development in the workshop. We are currently rebuilding the Polaron rocket and adding three external boosters. With a number of static tests earlier this year we noticed that Polaron was able to produce around 7 seconds of thrust when using foam and a 7mm nozzle. Because of the low peak thrust during take-off we are assiting the rocket with three boosters each with a 13mm nozzle.

We also tested a hybrid splice technique for joining bottles.

The full update including pictures are here:

http://www.AirCommandRockets.com/day47.htm

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Glue test results

The glue test results are now available here:

http://www.AirCommandRockets.com/day46.htm

We tested one splice that held at least 170 psi. This glue although not as nice to work with as PL is definitely a viable alternative if you can't get your hands on PL here in Australia. It has good bonding strength to PET.

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Glue Tests

This weekend we did some tests with the VISE polyurethane glue that Damo of Damo's Water Rockets found here locally in Australia. PL premium is not sold here and shipping costs can be quite high from the US. The VISE glue seems to have good adhesion properties to PET but its viscosity is much higher compared to PL which makes it more difficult to work with when splicing bottles.

We did tests to change the viscosity of the glue and also glued two splices. One with the regular vise glue and one with the thicker mixture. We will publish the findings in the next update of the main web page.

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Zero-G experiments

We had a chance to fly an experiment several times this weekend that we have wanted to do for quite a while. The purpose of the experiment was to demonstrate what forces act on internal components of a water rocket in flight. Gravity based parachute deployment systems appear to work on the ground, but are unreliable in flight.

The experiment shows what happens to a handfull of loose M&Ms inside the rocket during take-off and susequent zero-G (freefall) conditions. The M&Ms were inspired by Mike Melvill's handfull of M&Ms inside of SpaceShipOne.

The update includes lots of photos,videos and an explanation of the experiment.

It can be found here:

http://www.AirCommandRockets.com/day45.htm

The update also includes our first altimeter flights and some interesting results about foam.

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Development and repairs

We spent this weekend in the workshop repairing J4 II after its explosion last week. We basically replaced all the bottles with new ones, as some of them had been in use for 6 months or more. All the brass couplings were replaced with new Aluminium ones, reducing the rocket weight further.

We also taped all the inter-bottle rings to the rocket with a wide flexible tape, similar to electrical tape. This made the rocket much more solid.

We also reconfigured Hyperon III into a 3 bottle configuration as it will fly a long payload section when the weather clears up. Hopefully next weekend.

We also finally ordered a couple of altimeters last week, so I am hoping they will arrive this week. If they arrive in time, we should be able to fly them on the next launch opportunity.

We've also been working on a new simple and compact electrical pressure switch which we hope to test in the next few days. The prototype only weighs 10 grams but it should be possible to reduce that down further. The purpose of the switch is to serve the same role as the TDD, but without the exposed external moving parts. We use a TDD to detect when the pressure drops inside the rocket (at burnout) to activate the staging mechanism.


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Flight computer V1.3.2 test flights

We had a chance to fly a couple of rockets this weekend. It was mostly about testing a new flight computer and doing some foam flights just for fun. We got some good onboard video as well.

http://home.people.net.au/~aircommand/day44.htm

... oh and got a good wakeup call on water rocket safety ...
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Hyperon Flights at Damo's space port

We had an excellent weekend launching rockets with Damien Hart from Damo's Water Rockets. It was good to finally meet him and his family in person. The weather was well behaved and so were the rockets. (Well mostly)

We took turns in launching rockets, and as a grand finale we combined Damo's booster with our sustainer for a two stage flight.

The full details of the flight day are available here:

http://www.AirCommandRockets.com/day43.htm

and Damo's great write up of the day is here.

We'll have to do that again.
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Deployment systems

This weekend I spent time making the deployment systems around the two new flight computers. These will be fitted to 90mm rockets. One of them will be fitted to J4II instead of the NOAA deployment system we have been using. The other will be a spare for one of the three rockets (Tachyon II, J4 II and Hyperon). The new flight computers are now using the CR123A lithium batteries.

I also spent time this weekend building and testing a circuit that is going to form the core of a data acquisition system for our rockets. It is again based on the PIC16F628A microcontroller we have been using for the flight computers, but this one will be dedicated for collecting in-flight data. The part of the circuit that I tested was the RS-232 communications between the PIC and my PC through RS232. This way we will able to download the collected data from the unit. Eventually this RS232 interface could also be connected to a telemetry stream back to a base station. Each of these data acquisition units will record one or two channels based on the sample frequency required. It is planned that any number of these small units will be able to be placed on the rocket to gather as many channels of data as required.

I am also hoping to use one of these acquisition modules in our static thrust measuring rig for when we test new rockets.

Hopefully on Sunday we will get to fly more rockets again.
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Quiet week

We've had a quiet week this week, with dad in Europe and I've been busy fixing gutters and do ing paving, there wasn't a lot of time for rockets this week.

I did pressure test the two untested spliced pairs of bottles up to 115psi, and they both held well. We are reluctant to push them too far so that we don't have to rebuild them.

I also pressure tested the Hyperon rocket again to 130psi. And again it held up well to the pressure. I had disassembled a part of it during the week and needed to make sure it still sealed well.

I have finally received the CR123A Lithium batteries I bought on eBay this week. At $1.38 including delivery is pretty inexpensive. I tested them with the new flight computers and they work well. I was surprised that they are relatively light for their size. Since I don't have a battery holder for them, nor could I find one at the local electronics store, I have resorted to simply taping the contacts on with electrical tape. I realise this is less than desirable, but it seems to be holding well, so we will go with it for now.

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Hyperon Standard Platform

We have updated the main site with our latest water rocket developments.
The update is available here:

http://www.AirCommandRockets.com/day42.htm

The update includes more details about a standardised rocket platform we are developing for doing a number of experiments.

A video is included that shows how we make our Robinson couplings.

Analysis and developments

This week we have been doing a bit of analysis of the Acceleron IIIb flights we captured on video. We noted a few things:

1. It looks as if the stage separation was taking place a little later than we would have liked. The booster was already slowing down when the release happened. This can be seen at the top of the flight path as the booster starts pitching over. Since the release sequence is initiated by the pressure switch, we will need to make the pressure switch activate at slightly higher pressure. We can adjust the tension on the spring of the TDD, or alternatively add slightly less water to that segment with the pressure switch. Less water means that the segment will stop producing thrust slightly sooner compared to the other two segments that are still accelerating the rocket.

2. We now have a better idea of the time it takes to get to apogee and hence can set the parachute deploy delay for the sustainer appropriately. The parachute deployed about 2.5 seconds after passing through apogee.

3. The parachute deploy delay for the booster will be shortened as even the minimum setting allowed by the software on the day wasn't quite enough.

4. After release the booster looks like it falls more like a back-gliding rocket. It actually saved us a whole lot of work after the first launch since the parachute deployed so late. This is actually a favourable feature because if the parachute fails the rocket should land at a lower rate than if it hit nose first.

We have also been continuing with the next iteration of the flight computer. We are trying to reduce its weight and foot print to make the whole deployment system smaller and lighter.



The new flight computer uses a more compact and lighter launch detect switch. It works in two dimensions allowing you to mount the PCB in different orientations. The deploy servo is directly mounted to the PCB and the battery is directly below the PCB giving a more compact design. The full details of the flight computer will be posted once it has been tested.







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2 Stage successful flights

The full details of the 2 stage rocket are now available here:

http://www.AirCommandRockets.com/day41.htm

There are lots of photos and a video as well showing the day's highlights. The in-flight video turned out quite well.

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