Each flight log entry usually represents a launch or test day, and describes the events that took place.
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We had another excellent launch day with the NSW Rocketry Association (NSWRA) this weekend. When I woke at 5:30am I heard a really strong wind was blowing. The wind speed certainly put us out of our launch criteria. However, we finished packing and headed out to the site hoping the breeze would die down by the time launches started.

Launch Day Events

• When we arrived the breeze was still blowing pretty hard, so we set up the new launcher and waited. The pyro rocket guys had to angle their launch rods quite a way into the wind as well. We watched a few launches as the breeze started easing off a little. We finally decided to launch around 9am. Photos of the pyro rockets will be available here.
• First launch of the boosted Polaron IV rocket went well. We launched the rocket at only a conservative pressure of 110psi (7.6 bar). The rocket took off vertically and the boosters all separated simultaneously. The main stage continued to power vertically, although it looked like a gust of wind caught the rocket and pitched it over. This caused it to gain less altitude than expected on review of the altimeter data. The maximum altitude reached was 104 m (341'). This was a little disappointing but we knew that the rocket did not fly the optimum flight path.
• We were really happy with how the onboard video turned out. We didn't see any of the compression artifacts or stuttering as we did last time. Because it was a bright sunny day the video quality was excellent.
  
  The video showed us that the parachute deployed right around apogee, but the altimeter data again showed that it took the parachute about 1 second to fully open. I set the flight computer deploy delay to a full second longer than what the simulator predicted because with the use of foam you get that more protracted thrust phase. It turned out to be about the right timing.
• The rocket landed softly in the grass, but was only a couple of meters from hanging up in a tree.
• By the second launch, the wind died down more and the flight was a lot better. All the rocket parameters were the same as the first launch. The boosters again separated simultaneously and the rocket went up vertically again. It fish-tailed a little which was probably caused by the wind still, but did not pitch over as much as last time. This time it went to 144m (473'). We believe the rocket will go over 500' on a less windy day with the same setup and pressures.
• The parachute again opened right at apogee. You can hear the deploy servo activate, and see the parachute come out in the on-board video. Again the on-board footage turned out excellent. The video still had the lagging sound problem, but we fixed it in our video editor.
• The rocket landed on soft grass well downrange.
• Our last rocket for the day was the newly repaired Hyperon. It flew relatively well and was buffeted by the wind as well. The parachute opened at apogee and came down nice and gentle.
• We were really happy to walk away on the day without the need to do any repairs.

 I am including the video on both YouTube and MySpace as sometimes one or the other are unavailable.

(If the video does not play, try the latest Flash player from Macromedia)

Video and Image Analysis

We reviewed a lot of the video from various angles and frame by frame to try to understand how the main stage and boosters behave in flight.

• All three boosters entered their air pulse phase within ~80milliseconds of each other. This did not appear to cause the rocket to pitch in any one direction. It does look like the boosters may have been slightly misaligned and caused the rocket to roll. It was even more evident as the last booster dropped off.
• One of the boosters could be seen striking the fin as it separated, but no damage was done, and did not affect the trajectory.
• The fish-tailing was likely to have been caused by the gusty conditions, and this would have washed quite a bit speed off the rocket. (Hence the large discrepancy between flight 1 and 2 in terms of altitude)

The following is a pyro rocket highlights video from the day shot from our camera.

What's Next?

These flights were really only prototype flights to see how well the concept works. There are many things that can be optimised and will be carried out over the next weeks and months. One of the biggest issues is the weight. Polaron IV on these flights weighed in at a hefty 928grams empty! We are going to attempt to shave at least 200 grams from this.

We will increase the pressures to at least 120psi for the main stage and 130-140psi for the boosters. The launcher allows us to supply different pressures to the main stage and boosters.

In the longer term, the boosters will increase in both capacity and length. The main stage will also be increased in length and volume. We want to try the narrower Hyperon rocket with this arrangement as well.

Next Update

In the next update we will present the full details of the launcher, the Polaron IV rocket and booster separation arrangement. The update will also include a video of the first launcher tests using the dummy main stage.

Flight Details