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(Photo: Andrew E.)

(Photo: Andrew E.)

Date:  27th February 2010
Location: Doonside, NSW, Australia
Conditions:  Warm (30C) with mostly clear skies and 10+km/h wind.
Team Members at Event: PK, GK and John K .

This week's update is a bit of a mixed bag of different things we've been working on since the last update. We did test flights a dual deployment mechanism, test flew the MD-80 clone camera and continued work on the Acceleron booster.

Dual Deploy Mechanism

A dual deploy mechanism is designed to open a small drogue parachute near apogee and allow the rocket to fall in a controlled manner but at moderate speed. As the rocket approaches the ground the main parachute is opened to slow the rocket down for a gentle landing. This is done to minimize rocket drift in windy conditions.

This dual deploy mechanism is a combination of our side deployment and in-line deployment mechanisms. It was actually dwrule from Washington Water Rockets who last month suggested this arrangement so thanks for that.:) For the first flight tests we simply mounted the mechanism from the earlier tests on top of an existing side deploy mechanism. In its final form the in-line servo will be integrated in the side deploy corriflute frame. This will shorten the the whole mechanism by about 1 inch and save a little bit of weight. The prototype dual deploy mechanism weighed in at 162 grams or around 25 grams heavier than the side deployment alone. The additional drogue parachute weighs 13 grams.

The flight computer we are using to control the timing was designed with dual deploy in mind, but this was the first time we had actually flown it in that configuration.

Here is a Tomy timer based dual deployment mechanism Todd from HHWRSA made a couple of years ago: http://www.youtube.com/watch?v=X1hieyNtEMA&feature=related

Launch Day Report

• We arrived at Doonside at around 9am. The conditions were almost ideal except with wind blowing around 10km/h with occasional higher gusts. We had a couple of things we wanted to test this weekend. One was the dual deploy mechanism and flight testing the MD-80 clone camera. (see below)
• The first flight of the day was Axion II with the dual deploy mechanism. The deploy timing was set conservatively since we didn't know how exactly the rocket would behave under the drogue parachute. In case the drogue didn't open, the main was timed to open still before a ballistic return to Earth. The drogue was timed to deploy 4.2 seconds after launch and the main was set to open 12 seconds after launch.
• We tied both parachutes around the center of gravity of the rocket to help it come down sideways for increased drag and in case only one of the parachutes opened. In later configurations we may try tying the drogue all the way down near the nozzle. This would then allow the rocket to come down nose first a little faster and allow the main chute maximum clearance when it is ejected.
• We didn't attach the camera on the first flight in case we would have to perform shovel recovery on the rocket.
• Thankfully both parachutes opened when they were supposed to and the rocket landed well. It landed pretty close to the trees though. From video the actual fully inflated parachute times were 5.2s for the drogue and 13.4s for the main.
• We left the parachute timing the same for the second flight which was almost identical except we mounted the MD-80 clone camera in the side of the rocket. The parachutes again behaved themselves but because the wind had picked up at that stage the rocket drifted down range a bit. The main chute timing could have easily been extended another 5 seconds for lower opening. The view from the camera was nice and clear and due to the low spin rate the video was quite stable. The drogue timing was 5.6s and the main was at 13.7s.
• Due to the higher wind conditions we added the guide rail extensions to the launcher.
• For the third flight we wanted to fly a foam rocket which meant swapping out the bottom fin section on the rocket. This fin section has a Robinson coupling in the bottle which allows us to use Jet foaming. This particular bottle with attached fins was made back in August 2008 and has seen perhaps a dozen launches since. As we approached 120psi, the base of the bottle failed around the Robinson coupling resulting in a nice CATO. The rest of the rocket with the attached Robinson coupling now acting as a nozzle flew off, but without fins it pitched over and landed on its side safely in the grass. The rocket landed before the drogue parachute had a chance to open.
• Other than the blown up bottle, everything else remained undamaged. One of the launcher guide rails was slightly bent from the explosion, but can be easily bent back. The on-board camera also captured the action.
• We screwed on another fin section and the rocket was ready for it's fourth flight. The last flight was flown at 125psi. The dual deploy mechanism worked well again and the rocket landed without issues.
• We had one issue with the MD-80 clone camera though. When we downloaded the video from the explosion, it said the file was corrupt, but VLC Media player fixed it and we were able to see the entire movie. We always download the video after each flight just in case the rocket is damaged or lost. When we flew the last flight, I noticed that the camera only had the two original files on it, there was no third flight. This looked like a malfunction, or perhaps I didn't press the record button properly. It wasn't until I got home and was downloading the videos again from the camera that I noticed that the second file contained the last flight. Because the second file was corrupt the camera simply recorded over the previous flight. Luckily I had the original second flight on the laptop that we downloaded on site after the explosion, so we were able to recover all three videos. I am not sure why the AVI file was corrupt, perhaps it just wasn't closed off properly although all the video was there. The explosion may have had something to do with it, but I'm not really sure. So just in case, back up your videos after each flight!

I think we will add the dual-deploy mechanism to our box of spare parts that we bring with us. We can attach it to rockets when there are higher wind conditions at the launch site.

Here is a highlights video of the dual deploy mechanism in action:

Otherwise it was a great day for rockets both pyro and water. There were quite a few new faces at Doonside and quite a few larger pyro rockets too. Here is a pyro highlights video from the day:

Acceleron V build progress

Since the last update, Acceleron V has been progressing well. It is now mostly assembled with a few more minor things to do. We did pressure tests on the new nozzle seals, and decided to make them a little wider so dad machined up a new seal cutter. We also cut the new seals out of harder rubber so they would not distort so much when the bottles were tightened.

We pressure tested the staging mechanism and discovered a minor leak in the Gardena release head. It looked like there were a couple of scratches in the o-ring seat where the sustainer nozzle sits. This was a fairly minor leak but we decided to replace the Gardena quick connector. We still need to pressure test it this week.

The focus now is on getting the sustainer finished. The sustainer is being made from all new spliced bottles. The fin-can is now finished so hopefully we'll be able to pressure test the whole rocket soon.

After the failure of the bottle in the Robinson coupling this weekend we had a discussion in the car on the way home, and dad suggested that instead of the Robinson coupling we could put an insert into a tornado coupling to give us the same size jet of water to create foam. Since Acceleron's sustainer uses Jet foaming, we may replace the Robinson coupling with this insert to try to reduce the chances of another bottle base failing. Over the years we've had quite a few bottles fail this way. If it works it would also eliminate a metal component from the pressure chamber.

On Sunday he machined up the insert for our tornado couplings that has a converging section at the top end and a straight section in the bottom for the water jet. We will do a couple of static tests of this arrangement to see how well it works. We made an 8mm hole in the insert which the same as our Robinson couplings since we know the performance envelope of a hole that size. We may also try the insert upside down with the divergent section pointing down. The theory there goes that as the water/air comes down from the upper bottle some of it will be deflected towards the sides of the bottle helping to reduce the blow through effect and also assist in preventing the water and foam from sticking to the sides. The static tests will also be done this week.

MD-80 Camera Clone

All details about the MD-80 clone have been moved to a new separate page.

Flight Details