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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Acceleron IIIb flies!

We had a fantastic day of launching the big 2 stage rocket today. We flew it three times in total before we packed up. Both first and second stages behaved well and we got some great inflight video looking back from the sustainer.

The weather was great too with very little wind and mild temperatures.

I will post full details, photos and videos shortly.

(click image to enlarge)
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Acceleron IIIb details available

We have updated the main website with details of the Acceleron IIIb booster, the Tachyon II sustainer as well as the Flight computer used by the booster. The update also includes the burst test results.

The update can be found here:

http://www.AirCommandRockets.com/day40.htm

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Acceleron III rebuilt

Well its two weeks to the day, and we have finished reassembling Acceleron III. There are still little things to be done, but the bulk of the work in doing the rebuild has been done. We need to carry out pressure tests again (this time we will make sure the camera is rolling) and also a full system test during which we had the failure.

Details of the rebuild and the burst tests will be published soon on our website.


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2L Burst Tests

This week we tested the 2L bottles we use for the Acceleron III rocket. After the failure a couple of weeks back we wanted to see what these particular bottles can hold. We also did a test with a coupling as we suspect it was a bottle that failed near a coupling.

The burst pressures were at 165psi which is about what we found with other 2L bottles tested earlier. We also pressurised one to 130psi and held it there for 3 minutes. After three minutes we started increasing the pressure and it burst at around 150psi. Therefore we will drop the operational pressure of the rocket to 110psi until we start reinforcing the bottles.

We are now in the process of getting more bottles since 5 of them were tested to destruction and can't be used of course. We need about 8 more bottles which we should have this week.

We also completed the large parachute for the rocket yesterday. The parachute needs to be fairly big as the booster weighs around 2Kg dry.
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Rebuild commences

This weekend we spent a few hours on the rebuild of the Acceleron III booster. The booster is now completely disassembled. We can reuse three of the lowest bottles from the booster so that's good. They were new anyway and don't show signs of excessive stress. We made a new base-base coupling to replace the lost one. We replaced all the regular bottle caps used in some of the couplings with longer thread ones and put reinforcing rings on those. This was done for additional reliability, as we have had the smaller lids let go on previous occasions with other rockets. The pod is now also repaired.

One of the things that was quite apparent before the explosion was that the sustainer had quite a wobble to it when it was sitting in the staging mechanism. A number of fellow wrocketeers mentioned that the sustainer could snap off during take off, so we took their advice and started adding better support for the sustainer. This is now mostly complete, but we had to remove the fin assembly on Tachyon and will have to attach fins a different way.

We will also do a couple of burst tests on these particular 2L bottles we are using to see if the upper limit of these bottles is similar to other 2L bottles we have tested. One of the tests will include a coupling.
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Catastrophic Failure

Yesterday, we had a catastrophic failure of the Acceleron III booster while pressure testing the entire system. There was a pretty loud boom that echoed through the neighbourhood. Full details of the test and what happened will be posted along with pictures in the next couple of days.

Most of the components can be recovered and we have already started making repairs. Hopefully in two weeks we should be able to have it fully rebuilt again.

Before:

After:

Bits:

Acceleron III Pod and Flight Computer

This week we finished building V1.4 of the flight computer. It is specifically designed for the Acceleron III booster. The majority of the new flight software has also been written. A few minor changes will still be made to the code, but they are mostly cosmetic. The flight computer now detects the burn-out in the booster to trigger the staging mechanism a short time later. Then after a settable delay the parachute is deployed.

Acceleron III payload pod. (staging mechanism - upper left, long thin tube is the sustainer air supply, the pressure switch is the device with the spring, and the flight computer, actuators are attached to the yellow bulkheads. The parachute is located on the other side of the pod.)

We temporarily mounted the FC into the pod and tested to see how it fits and operates with the staging mechanism. We are quite happy with the overall design and operation. Although it is probably heavier than it needs to be, it is only the first prototype, so a little more weight is acceptable.

The pressure switch (Trevor's TDD) now has a microswitch and is connected by short cable to a connector. This way the unit can be removed from the booster segment for filling with water and then fitted again.

We also manufactured a second 5mm nozzle that has a better fit for the staging mechanism to reduce the amount of wobble the old one had.

We are now pretty much ready to commence full system tests.
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