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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MySpace Upgrades

It appears that MySpace is doing some upgrades at the moment, so a number of the videos on our site are not available during this upgrade. Check again later, if there was something you wanted to see.
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Tachyon test flights

We had a sucessful weekend flying the Tachyon sustainer. We wanted to test it as a single stage first to make sure it will perform as expected when it is boosted by Acceleron III.


The full details of the flights can be found here:

http://www.AirCommandRockets.com/day38.htm

A video is included in the update that shows the highlights of the day.

We are now just finishing the Acceleron flight computer (V1.4) and should be ready to do some end to end testing of Acceleron III systems fairly soon. Once all the tests have been successfully completed, the two stage rocket should be ready to fly.
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Bad weather

We didn't get a chance to test the sustainer this weekend as it literally rained non-stop the whole weekend, as well as strong winds on Saturday with gusts up to 80km/h. This is the second weekend we haven't been able to launch. :(

We stayed indoors and continued the development. We made good progress with the Acceleron III pod, mounting the servos in it and connecting the staging mechanism to the servo. We did a dry test to see if the servo had enough strength to release the Gardena staging mechanism and it looked good. We also fitted a micro-switch to the TDD so now the flight computer will be able to know when burnout has happened.

We now only really need to finish building the flight computer and making the parachute and the rocket will be ready to go. We will still need to do a few full system tests with staging and parachute deployment before the actual launch.

We also tested the spliced bottle we glued a few weeks back. We pressurised it up to 100psi and it held well. We didn't want to burst test it as there is no guarantee that the next splice will be as strong. We will test these splices to perhaps 20% above operating pressure without destructive testing.

We will make up a number of these spliced pairs (as opposed to sliced pears) and then make our first rocket out of them.

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Tachyon sustainer and staging mechanism testing

We have updated our website with the latest progress update. There is a video showing the details of the Tachyon parachute deployment mechanism as well as a test of the staging mechanism under pressure.

Update is available here:

http://www.AirCommandRockets/day37.htm

We have also added a site index to the website to make it a little easier to find things.
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Tachyon completed

We have finished building the Tachyon sustainer this week, and pressure tested it up to 130 psi.


We wanted to fly it during this long weekend, but due to the heavy storms here in Sydney we were unable to. We had wind gusts of up to 100km/h, huge seas with up to 15m (40 foot) waves and drenching rain. Our local park had quite a bit of standing water on it, so it was unsuitable for launching as well. We will fly it at the next opportunity.

Meanwhile we have been continuing with the staging mechanism on Acceleron III, and plan to continue with it tomorrow.
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Tachyon Sustainer Development

This week we concentrated on the Tachyon sustainer. We need to have it built so we can see how it mates to the booster and add the necessary supports. We had our first attempt at gluing the fins directly to the bottle, but found out that PL Premium does not stick to the plastic the fins were made out of. (The glue held great to the PET bottle.) So we connected the fins in a more conventional mechanical manner. The new fin arrangement is removable and does not require to be glued or taped to the bottle.


We also completed the deploy mechanism utilising V1.3.1 of the flight computer. (V1.3.1 includes a software upgrade to drive RC servo motors directly and bypasses the DC motor driver part of the circuit). We are trying a hinged door mechanism for the parachute bay to see how well it works. We wanted to get a more streamlined recovery system compared to the Polaron III rocket. The computer/servo and parachute bay are removable from the rocket skin for easier servicing.

We really need to only manufacture one more aluminium coupling for the inter bottle connection, and then the sustainer should be complete.

We hope to test fly it this weekend to test the deployment system and dynamic stability.
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Multi-stage Details, Acceleron III assembled

We have updated our main site with some development photos showing the Acceleron III booster with the sustainer on top. The details may be found here:

http://www.AirCommandRockets.com/day36.htm


There is still lots more work and testing to be done, but finally we have an idea of the overall dimensions.
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Our First Splicing tests

We had our first go at splicing yesterday. We used the symetrical splicing method first to see how well it will work. We used PL Premium glue kindly donated by Team Parental Advisory.

The symmetrical splicing method is described here:
http://www.geocities.com/wrgarage/const.htm



We need to leave it for a few days to dry and then we will pressure test it. The collar was made by heat shrinking a section of a larger bottle over another cold water filled bottle. It was a little warped, but should be okay. Doing it this way gives you a really tight fit over the bottles to be spliced.

We will probably make up sections like this and then join them neck to neck so that the number of splices is minimised. The 22mm throat is big enough that any choking effects are negligible within the rocket. The sections being screwed together also means you can replace a section should it burst or get damaged.
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development progress

This last week has been a bit quiet on the development side of things due to other commitments, parties and the like. With those things out of the way, development will again continue this week.

I also received the 10 new micro-servos I've been waiting for for a couple of weeks. I built a small test circuit from a 555 timer to check them out and they seem pretty good and look like they will do the job. I have yet to measure the current consumption so that we can choose our batteries in case we need more power. Having the servos on hand now means we can complete the deployment systems for a number of rockets. We will also need to update the flight computer software to generate the appropriate pulse train to drive them.

This week we also plan on having a go at doing some splicing of bottles, so we can do some more burst tests.

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