This blog covers the day to day progress of water rocket development by the Air Command Water Rockets team. It is also a facility for people to provide feedback and ask questions.

Sunday, May 27, 2007

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:

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

Saturday, May 26, 2007

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:

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.

Tuesday, May 22, 2007

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.


Tuesday, May 15, 2007

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:

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.)


Monday, May 14, 2007

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:


Friday, May 11, 2007

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.

Monday, May 07, 2007

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.

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


Tuesday, May 01, 2007

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.