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Date:  27th November 2010
Location: Doonside, NSW, Australia
Conditions:  Warm 29C, mostly clear skies 5-20km/h wind.
Team Members at Event: PK, Paul K and GK

It's been a fairly quiet month as we have had many non-rocket related commitments such as kids birthday parties, sports and school concerts. Though we have continued to develop the Polaron G2 nosecone and recovery system. We also launched a couple of rockets at the NSWRA launch this week, but it was more for fun than testing anything new.

Polaron G2 - Progress

Nosecone

We have continued to try to improve the nosecone making technique from the last update. The main problem was trying to remove the nosecone from the plug without having to need to split it along the length. In the second attempt I tried using some glad wrap on the plug, but I couldn't get all the wrinkles out, and as a result it turned out a bit lumpy, especially near the point. I tried three layers of the 85gsm cloth, but the end result was that it was probably too thin to take a bit of punishment. I had the same trouble getting the nosecone off the plug as before. I did try a bias cut on two of the layers though, and it seemed better to work with.

	The second attempt did not work out too well with glad wrap on the plug.  This one is going in the bin.
	For attempt #3 I used a silicone swimming cap ($7 from BigW) stretched over the plug and tied with a string.
	This time I used one layer of the 200gsm cloth and two more layers of the 85gsm cloth on top. This gave a very nice finish to the nosecone, and it was very easy lay over the swimming cap. Again the bias cut cloth seemed easier to conform to the shape.
	Because of how the cap stretches - thin at the point and thick near the base (~0.8mm), I was hoping that with the extra thickness around the base I would be able to stretch the cap more after the nosecone cured and hence reduce the lining diameter giving that important gap to separate. I trimmed the excess glass from around the base and then slowly worked my way around stretching the cap and you could see it separate between the nosecone and cap. This propagated almost 3/4 of the way from the base to the nose and was easy to do. Unfortunately when trimming the glass I nicked the cap in a couple of places so I ended up ripping holes in it. But that was enough to quite easily pull the nosecone off the plug. So here is one clean nosecone, and the finer weave on the outside should make this one easier to finish off the surface. I am tempted to stretch another cap over the outside when I lay it up which may give it a nice smooth finish, but air bubbles might be a problem.
	I also didn't use a black marker on the pattern this time which should stop it from bleeding through when painting.

Recovery System

The recovery technique we are using for G2 is similar to the in-line one we trialled earlier this year with several improvements and in larger scale. This first version is still a prototype so it is a little heavier than we'd like, but good enough for first flights.

How it works:

The parachute is simply packed and placed on top of the flat platform on the base. The nosecone has a spring loaded ejection plate inside it. When you put the nosecone on top of the parachute you compress the ejection plate and then lock down the nosecone on either side with latches.

The nosecone side of the latch is simply a rubber band made from an o-ring so it stretches less. The base latch pivots so that the loop is caught and held down.

click image to zoom in

When it's time to release the parachute, the base latch pivots back so that the loops on both sides slip off and the nosecone and parachute are free to fall/slide off. The springs ensure there is enough force to just separate them and the uneven airflow does the rest. The springs should be strong enough to overcome the air pressure on the nose. In the final full recovery system, there will be a separate drogue parachute mounted in the mid section of the rocket, and will be triggered by PK's MAD. This will cause the rocket to come down sideways (more drag) and so when it later comes to deploying the main, the airflow over the nosecone will be sideways and hence even easier to deploy the main parachute.

 

	Some of the components that make up the deployment mechanism. We didn't end up using the two clear rings in the photo as we changed the design. The fairing for the base is made from two layers of 200gsm fiberglass.
	We made a couple of inserts to go into the Coreflute to support the crank shaft.
	Servo motor with crank and latches. This way we release both latches at the same time.
	Ejection plate components are made from 5mm Corflute.
	The ejection plate locks into a slot inside the nosecone. This allows us to replace the ejection plate for different sized parachutes. We use conical springs which compress down well. (Looking into nosecone on the right)
	The base has a smooth top without any obstructions to allow the parachute to easily slide off in the air flow. There is a small lip around the outside which fits inside the inner edge of the nosecone. This keeps the nosecone from sliding around sideways when in the locked position.
	Looking into the base. The components are spread out around so that we can fit a part of the pressure chamber in the space in the middle.
	Nosecone, base with parachute on top and the ejection plate.
	Latch in the open position.
	Latch in the closed position.
	An O-ring is used as the rubber band to catch onto the latch.
	Overall nosecone and deployment mechanism.

Launch Day Report

Due to all the commitments we had during the week, we only packed the sustainer from the Acceleron V rocket and a few spare rocket components so that we could make one up on the spot should the rocket crash. The predictions were for high wind on the day, so we weren't sure what we should fly anyway. It turned out to be a nice day and the wind was fairly calm during the morning.

We flew the first flight at 125psi with 1.8L of water and foam. The flight was good with good recovery. The on-board video is shown in the highlights video below. Because the wind direction was towards the rocket eating trees I decided to take out the altimeter in case the rocket got snagged.

As the wind picked up a little for the second flight, I removed the camera again because of the danger of getting snagged in the tree. We also added an extra second to the deployment timer to help the rocket come down quicker. The flight was good again with a nice long foam trail.

For the last flight, I swapped out the bigger parachute for a smaller one with a hole, again to try to stop the rocket drifting too far. Again the flight was virtually identical to the previous flights and the rocket ended up landing fairly close to the trees.

We also flew Paul's Pod 2 2-stage rocket on a C6-0 and a C6-5. The rocket weather cocked into the wind and flew in a nice long arc. The stages separated well, but the delay seemed a bit long and when the parachute finally deployed it ended up ripping a fin off the rocket. We couldn't find the fin in the tall grass, but it should be fairly easy to repair.

We were happy the water rockets performed well and it's always nice to get them back in one piece.

We wanted to test fly the G2 nosecone but ran out of time during the week to prepare the test rocket, there is always next time. In the video below I have combined both the pyro rockets and water rockets flown by club members at the NSWRA launch at Doonside.

Day 98 - Highlights

Flight Details