This is a record of the days we launched rockets and the
events that took place.
 

Well finally the weather cleared up and we were able to get a few launches in this weekend. We were going to be testing water vs foam flights using the altimeters, but one thing lead to another and we just ended up launching them for fun. Here are the details of the flight day.

Events

• As we arrived at the launch site we discovered that there was a plague of flies. With the warm weather we have been having lately they must have all emerged at the same time. After 5 minutes of spending more time swatting them away than setting up the launcher, dad jumped in the car and went home to pick up insect repellent. It's good to live within 2 minutes of the launch site. As I sprayed myself head to toe with repellent I began to wonder if I should take fly-induced drag into account in the rocket calculations.
• Although the first flight pitched over a bit after take off it came down well under parachute. Max altitude reached was 89m. We were only flying the rockets on relatively low pressure to keep them within the park. We also set the parachute deploy delay to half a second later than normal to minimise drift on the way down.
  
  The only damage was when the nosecone hit the ground and the servo motor popped off its mount. We tried to fix it, but one of the screws stripped the thread where it was attached and so we decided to simply swap the entire payload section we brought as a backup. This payload also had an altimeter already mounted and the weight of the entire section was identical to the one we replaced.
  
  The nosecone also head a removable camera mounted in it, so it weighed a little more and had a bit more drag but we were going to fly it anyway. We wanted to at least get some footage with foam, and then remove the camera for the next flight and fly a foam comparison mission with an identical setup to the first water-only flight.
• After the rocket landed everything looked fine, but we discovered that the camera did not record anything. I was pretty sure it was recording when we launched, so I wasn't too sure what had happened.
• We launched it again with the camera and altimeter. This time the rocket took off at quite a bit of an angle and headed straight for the river. The parachute failed to open and the rocket heavily crashed through some trees and on the other side of the river. It took us a few minutes to find it.
  
  The flight computer was totally obliterated mostly by the battery that was located just underneath it. The altimeter was hanging out the side and the camera had completely detached and was lying a few meters away. We checked the camera and although it turned on, we saw that nothing was recorded again. Arrrgh! I tried doing a record test and half way through a recording the camera just shut itself off. I am not sure yet if the camera is damaged or perhaps the battery might be low. Although we did replace the batteries recently. We will have to do a few more tests.
  
  The altimeter survived, and despite having its power cut on impact still managed to record almost the entire flight with the exception of the last few samples. A couple of the connector pins were bent on it, but that's all. The servo motor was also destroyed as the gears are locked together and you can no longer turn the arm. One of the fins was also destroyed, and we only found the base part of it.
• We do not know why the parachute failed to deploy. It is just one of those things I guess.
• We then launched the Graviton rocket a couple of times since J4IIIb could now easily fit in the car's glove compartment. We didn't have a gravity experiment in the payload but instead just flew it with foam for the kids. Both flights went well without incident. We taped the other video camera to the side of the rocket and ended up with a semi decent video although the rocket had a bit of a spin to it.

Water rocket foam flights with altimeter

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

What's next?

We are now going to seriously look at a new nosecone design. We have been designing the payload section as lightweight as possible and with the view that all landings would be gentle. Figuring if we had a hard landing there wasn't much we could do anyway, and we would just rebuild the broken ones. We are now going to change things quite a bit and allow the nosecone to come down hard without destroying anything valuable. With padding and crumple zones it should be able to protect the rest of the payload better. It should be relatively simple to then replace just the outer skin.

The flight computer is also going to get an upgrade and will be integrated with the altimeter. Currently I have my hands full before a launch in setting up the flight computer to the right time, arming, zeroing the altimeter, starting the recording, turning on and starting the onboard video camera and finally video taping the whole launch from a distance. A lot of this happens just before pressurising and the camera start happens after pressurising so there is always a danger the rocket could go bang on the launch pad, when starting it..

If we can get the camera open and gain access to the switch contacts, I will try to get the flight computer to switch the camera to the right mode and start recording, automatically.

I would like to start the entire process remotely with an infrared remote control, so that no one needs to be near the rocket after it is pressurised. Everything on board the rocket will be automated. Although this might take a bit of time to set up, it will be essential once we start using higher pressures in our rockets.

Once the nosecone is redesigned we will get back to comparing the water and foam flights.

Recording Flights

We are now using a standardised form for recording all flights. We used to just write down the details as they happened, but sometimes forgot to include everything. The form also allows us to record the info quickly and consistently. Although it might seem like overkill for the hobby, we find it very useful to go back and refer to previous flights when we are trying to analyze performance or when something goes wrong.

We also capture weather data from the internet for the closest weather station to get the environmental data over the course of the launch day.

Flight Details