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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Flight Computer V1.3

We have finished the V1.3 Flight computer code and also took some photos. The full details of the design is available here:

http://www.AirCommandRockets.com/flight_computer_V1_3.htm



While retaining the same functionality of V1.2, the new flight computer is lighter ( 37 g with battery), uses a single battery design and has a greater selectable range of delays ( 3 - 11 seconds in .25 second intervals.)

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Staging Mechanism Update

This weekend we spent a few hours in the workshop building the necessary components for the staging mechanism and upgrading the booster.

Some photos of the progress of the staging mechanism are available here:

http://www.AirCommandRockets.com/day35.htm


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Starting Multistage Work

Having flown the Acceleron I & II booster a total of 16 times now, we are happy with how it has been performing.

So last night we spent a couple of hours designing the staging mechanism for the booster. And I think we finally have a good plan. The release will be based on a Gardena release mechanism rather than a crushing sleve. The main reason is that with the gardena mechanism, you can release the rocket exactly when needed, rather than when the pressure drops inside the main booster as with a crushing sleve. Also all our existing nozzles will fit the sustainer. The other main reason is that we know that the Gardena mechanism can hold higher pressures up to at least 220+ psi. We want to be able to retain the design once we start reinforcing the bottles. Lastly the crushing sleeve method doesn't lend itself very well to the construction of CD nozzles, which we plan to revisit especially with the sustainer.

Full details of the design will be published once we build it and we know that it works.

Acceleron II has now been disassembled and will get a couple of upgrades:
1. Each booster segment will be extended by a further 2L capacity to help with the greater payload. This means that the total capacity of the booster will be close to 25L.
2. The dummy payload will be replaced by a new payload pod that will house the flight computer, camera, parachute and staging mechanism actuator. The staging mechanism will be mounted just above the pod. The pod will also be used to support the sustainer and protect the payload contents from the spray during separation.

The first sustainer will most likely be based on two 1.25L bottles joined together and will look similar to "OO", with the exception that it will also have a flight computer, camera and side deployment. Eventually when we buy an altimeter we will put that in there as well.

We are more likely to spend this weekend in the workshop rather than launching rockets as we are keen to see how it will go.
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Vertical racing

We had a go at simultaneous launches again this weekend. It was fun as usual, and we even tried foam in all three rockets at the same time.


Of the 12 launches all the rockets survived the day well so we were happy. The update contains photos and a highlights video as usual.

http://www.aircommandrockets.com/day34.htm

We are going to rebuild a couple of the rockets now so there should be something new to see in the next update.

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Progress continues

Because it was too windy to fly this weekend we decided to do more work in the workshop. We manufactured three more aluminium Robinson couplings for extending Acceleron II's capacity by another 6 liters.

We want to fly Acceleron II again before the upgrade, so it will be couple of weeks before it is done. We first need to drink lots of lemonade before that happens!

Otherwise progress is going well on the V1.3 flight computers, with two of them now being finished and tested. We are now creating two 90mm diameter payload/nosecone sections with the deployment system inside them. These are more aerodynamic then our previous ones.

One nosecone will go onto J4 II and the other one will be used for Acceleron II's yet to be named sustainer.
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Foam and CD Nozzle Thrust Data

We have finished processing the thrust data from a couple of weeks ago that compares Convergent-Divergent (CD) nozzles to straight trough nozzles. We did 12 tests in all comparing 7mm and 9mm CD nozzles to 7mm and 9mm straight through nozzles.

The update is here:

http://www.aircommandrockets.com/day32.htm

The tests were done in exactly the same fashion as the last set of static tests when comparing foam and water thrust.

The results were interesting, although not unexpected. The update also includes the data in a spreadsheet format if others want to use it for further analysis.
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Simultaneous Launches and foam flights

In order to get back into flying we decided to have a go at launching multiple rockets simultaneously. Other than being lots of fun, one of the biggest problems was knowing which rocket you should be watching and the other things like nosecones falling off.


We then also flew a number of flights using the Jet foaming technique and 7 mm nozzles. The slow take-offs are quite a contrast to fully open nozzles using only water.

The update is here: http://www.aircommandrockets.com/day33.htm
The update also includes pictures and a video of the day's highlights.

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CD Nozzle Tests

We tested two CD nozzles this weekend. There were 12 tests in all:

• 3 tests with 7 mm straight through nozzle
• 3 tests with 7 mm CD nozzle
• 3 tests with 9 mm straight through
• 3 tests with 9 mm CD nozzle

Since it takes a bit of work to translate the video frames (around 6000 in total) into a spreadsheet it will take some time to do that. Once we have the data in a usable format we will publish it again.


We went through almost a liter of bubble bath solution, but collected the water during the tests so it just didn't go onto the lawn.

We think this will be it with the static tests for a while, as we are keen to get back to real flying.
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Convergent Divergent Nozzles

In order to see if a water rocket can benefit from CD nozzles (de Laval nozzle) while using foam we have built a couple to hopefully test this weekend.


One is a 9mm nozzle (aluminium above) and the other a 7mm (black plastic). The divergent part is conical in shape and has a slope of 4 degrees from the centerline. This value was obtained by reviewing the video and seeing at what angle the spray emerges. The actual angle of the spray varies over time from quite wide to quite narrow near the end as the pressure drops.

The average angle was about 4.7 degrees during the middle of the burn. We chose a value of 4 degrees because our thinking was that if it was more than 4.7, there would be nothing touching the sides during the middle of the burn and hence ineffective. That is just a guess and not based on any scientific or mathematical calculations.

We just want to test to see if there is a noticeable effect when a CD nozzle is used with foam compared to a straight through nozzle. If there is a difference, further tests will be performed to see how the shape can be optimised.

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Thrust Data for Water-only and Foam rockets

Well it has taken a while but we finally managed to get some good thrust data for a water-only water rocket and compare it to a water rocket using foam generated by our Jet Foaming technique.

http://www.aircommandrockets.com/day31.htm

The update includes the thrust data curves for 6 firings in total (3 water and 3 foam), as well as an analysis of the results. There is a video that shows how we measure the thrust.


The write up is a bit lengthy but we wanted to make sure that as much data was available for others if they wanted to process the data further or use it in their designs.

Feedback is always welcome.
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