Archive for June, 2008

The competiton

Tuesday, June 10th, 2008

I am proud to say that the hard work me and my scouts have put in over the last few months paid off, as we took home the trophy for the water rocket competition. Overall the competition was a great success with 6 teams entering and lasting for just under 2 hours. All the scout groups who took part thoroughly enjoyed themselves and we are looking to repeat next year.

Despite winning the competition, I wasn’t happy with the performance from the rockets. Below is a brief summary of the launches.

Louie, the large 4 bottle rocket struggled to accelerate up to speed and when it did, it veered off to the right, into a tree. The second launch was more vertical but didn’t achieve near the height I was hoping for and the parachute failed to deploy, badly damaging the parachute module on impact. I believe the parachute failed to deploy in this instance due to the string holding the door getting tangled, although the impact shock it so much I can’t be sure. Louie was retired after this, as we needed to try and get a good air time record.

On post calculations after the competition, I believe the cause of Louie’s poor performance to be due to low launch pressure. Louie weighs around 600g and was filled with bout 1600-1800ml’s of water. When I put those numbers into a simulator, at 70 psi the rocket would have struggled to have got off the launcher. The first launch was done at 80 psi and second at 90 psi. Its quite clear to see that the first launch had only marginally more pressure than what was needed to lift the rocket a couple of feet.

Doing some more calculations, 120psi would have gone over 300ft and 130psi was starting to near 400ft. Before this I had given up on 4 bottle rockets thinking the size of the nozzle we use are two small. But on reflection if we can get enough pressure in them, I think they should perform very well.

Huey was used for the third air time record, its first flight ended in disaster as the rocket powered up to a record height and then proceeded to fall with no parachute. I think the parachute may have not opened due to the angle of the light sensors. When the last two circuits were made, they had longer wires on the light sensors meaning that they pressed against the inside wall of the bottle, making them point more vertically. With the low position of the sun in the sky at launch I think it may have caused the circuit to be unable to determine the orientation of the rocket. Anyway the parachute module was destroyed on impact.

The last two flights for Huey were for egg recovery’s. For the first flight I had managed to repair the parachute module from Louie and to my delight it worked, safely bringing the egg back to the ground. However as I pressed the reset button on the parachute module for the next launch, a wire came unsoldered, rendering the module useless. I launched again with no parachute but to no surprise the egg was destroyed. As a comical finish the rocket then got chewed up by a dog shortly after crash landing.

Dewey was the only rocket that consitantly performed. As the horizontal rocket it acheived the top 3 distances every time.

I hope to post some further anaylsis over the next few weeks after I have watched some of the video footage. As well as some videos and pictures and some ideas for what can be improved on for next year.

The final 3!!

Saturday, June 7th, 2008

After many months of research and hard work, Weston Greens final 3 rockets are complete.

From top to bottom, Huey is our egg mission rocket, hence the “Egg Transport Module” on top. Dewey will be used for the horizontal flight and as such does not require a parachute module. And last but by no means least, Louie the 6ft monster will be used for the height challenge.

Another picture of Louie standing in all his glory

Modified Launcher

Sunday, June 1st, 2008

After seeing how the standard launcher from Maplins was very wobbly with a 2 bottle rocket + Parachute module, I was doubtful that it would be able to hold the 4 bottle rocket at all.

I spent sometime this weekend adding some long pieces of wood to act as guide rails for the rockets. These should hold the rockets quite nicely even in fairly breezy conditions.

There are only guide rails on 3 sides, since I need to be able to still launch the rockets at a 45 degree angle in certain scenarios.

I also lengthened both the pressure hose and the trigger wire. I took the garden hose connector on the launcher apart and found that it was just a standard garden hose adapter with a long brass valve inserted into it. Using 2 more quick connect hose adapters and a piece of hose, I extended it by a couple of meters.

Below is a picture of the brass valve and hose connector.

And a picture of the hose going into the launcher