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Date:  10th April 2011 8:15am - 11:30am
Location: Doonside, NSW, Australia
Conditions:  Windy 20km/h with gusts to 30km/h later int he day. Temp ~26C
Team Members at Event: PK, Paul K, John K and GK

Polaron G2b

During the last couple of weeks we concentrated on getting the G2 ready for flight again. We replaced the in-line deployment mechanism with a side deploy that has worked well for us. We also added an independent backup parachute mechanism in the first gap between bottles. The backup uses the Servo Timer II and a MAD to detect when the rocket tips over at apogee. This was done so that if something went wrong again and the rocket flew lower than expected then the backup would fire when the rocket tipped over.

We also added the altimeter and camera to the payload bay. All the electronics are also powered by a couple of the little LiPo batteries. All up including the 32 gram parachute and complete payload bay, only weighs 150 grams.

Both the main and backup parachute ejection plates are based on the same principle we trialled with the Servo Timer II tests two weeks ago.

The nosecone is also new and made of thinner and lighter fiberglass compared to the in-line deployment mechanism from the previous version.

We also opted for only 3 spliced quads on this flight, in case something went wrong again.

Launch Day Report

It was just one of those days where things just don't quite go your way. We had the Polaron G2 ready on the launch pad and fully pressurised, armed, and mere seconds from lift off when BOOM! The top spliced quad failed sending out bits in all directions. This was our first quad failure at this pressure, though the  pressure chamber had been hydro tested to 270psi a week before. We can only speculate why it failed, perhaps a weakness in one of the spliced bottles, or perhaps the result of higher temperatures due to air compression weakening the PET bottle? The rocket was filled quite quickly so this is a likely cause.

The damage was quite extensive, and certainly one of the more expensive failures. The video camera was smashed to bits even cracked some of the ICs on the board. We didn't have the protective sleeve on the camera which probably would have at least kept all the bits together. This way they were all scattered in the tall grass. We didn't find the little SD card. There wouldn't have been much on it anyway as the camera was facing out. The altimeter went flying which we managed to find in the end, the wires were ripped off, and the USB connector was bent, but after straightening it out I was able to connect it up to the PC and thankfully it still worked. There was no useful data on it as power was severed while it was still on the ground.

The MAD and servo timer 2 in the payload bay also appear to have survived with a couple of bent pins. The servo motor was also intact. . The LiPo batteries are gone as we only found the contacts pulled out of the batteries.

The nosecone deployment mechanism survived with only a little damage to the fiberglass body which is easily repairable.

The launcher was quite badly damaged from the failure and bent the guide rails beyond repair. All the aluminium tubing will have to be replaced. We are currently looking to see what improvements we can make on the launcher since we need to rebuild some of it.

Since the guide rails were damaged, we only flew the Axion IIc rocket off the launch tube to test the ST II on a larger rocket and at higher G-loads. The timer worked well, and the rocket landed without incident. We decided against launching it a second time as the wind at this stage was gusting to 30km/h. The wind managed to flip our gazebo over our cars at the same time. Note to self: secure the gazebo better next time!

Earlier in the day we also launched Paul's 2-stage pyro rocket on a couple of C motors and it flew well and both stages virtually landed back near the pads.

Though it's always disappointing to lose a rocket on the pad without even flying it, it's just a part of the water rocket development process. From incidents like these, we always learn something new, and making a replacement is always easier as the design work has been done.

The rocket is now well into it's repairs and we look forward to having another attempt at launching it soon. A new MD80 clone camera has been ordered, and with the strength of the Australian dollar, it only cost $11.50 delivered.

Here is a highlights video from the launch day:

Day 103 - Highlights

Flight Details