Pressure switch testing

I've posted the results of the pressure switch tests here:

http://www.AirCommandRockets.com/day84.htm



The switch seems to be working well so now it's onto finishing the rest of the spliced pairs and getting Acceleron V re-assembled.

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Acceleron V pressure switch

This weekend dad and I worked on the Acceleron V pressure switch. On Acceleron's last flight it did not look like the pressure switch(TDD2) worked properly, and the pressure switch(TDD) we were using before on the earlier Accelerons had been somewhat leaky.

The pressure switch is used by the primary flight computer to initiate the staging of the second stage when the booster stops producing thrust.

So we set out to try to make a more reliable one. (I think this is our 5th attempt at a simple and reliable pressure switch). In the photo below is the prototype. The hose clamps are only temporary for the first pressure tests. Also the cut off bottle neck at the end of the switch is only temporary to support the clamp.

We pressure tested the activation pressure and it was around 30 psi. That means that the switch will activate when pressure falls below 30 psi. This is a good value because the flight computer can delay the staging a little bit until the pressure is around zero.

We ran several low pressure cycles to test how well it activates. And the results were always repeatable. We are now gluing it together properly, removing the hose clamps, and when the glue has dried, we will test the switch to full operational pressure to make sure it can still hold up at the higher pressures.

I would also like to set up one of the booster segments on the thrust stand and simulate a launch with the correct amount of water and pressure. The segment will be fitted with the pressure switch so that we can see when the switch activates in relation to the thrust curve. This should allow us to then calibrate the small staging delay for the primary flight computer.

Once the pressure switch is fully tested, I'll do a full write up of how it works on the main website, but it is simple enough for most people to build.

Acceleron V has also been completely stripped down so we can start replacing the bottles with the new spliced pairs.

Deployment Mechanism development

We have also been working on a new deployment mechanism that uses in-line parachute deployment. The main criteria for this is to reduce the weight. Currently the standard nosecone and side-deployment mechanism we are using on a 90mm bottle weighs around 138 grams without the parachute, but it does include all the mechanical hardware, electronics and battery.

The new nosecone and deployment mechanism currently weigh 37 grams (including a servo motor) with the electronics and battery still to be added. The new electronics (FC V1.7) and battery will add about 20 more grams, so all together the entire nosecone should be around 60grams. The design also allows for potentially large parachutes and is also around 30% shorter than our existing designs.

When we've had a chance to test fly it a number of times, I'll again post full details.
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Day 83 Update

I've posted the flight day report from Doonside on our main website here:

http://www.AirCommandRockets.com/day83.htm

It includes a highlights video and photos from the day as well.

I've also updated the flight day report with findings from last night when I was pulling the rockets apart to give them a clean. (see the Update section) It turns out we had some heat distortion issues that we didn't know about on the day. The Polaron VII rocket also flew with a missing o-ring in one of the Tornado couplings!

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Flight testing new splices

Well it's been quite a while since the last update, but rocket development has been continuing although a little slower due to the holiday season coming up. Today we went out to Doonside to test launch the new spliced pairs to see how they behave under flight and landing conditions, as well as sitting in the sun for a while.

The rocket used all 4 spliced pairs previously tested to 140 psi. The rocket was launched a couple of times at 130psi, and the splices held out well without any significant issues. 5 more of these will now be made and fitted to Acceleron V.

I am doing a write up of the whole day along with a few other foam and flour flights we did on the day. I'll post photos and a highlights video in the next few days.

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