Monday, April 4, 2011

First launch of the year! (pt. 2)

Conditions for the first METRA launch of the year were warm and clear, but windy. The wind did not fall below 10 mph at any time, and often gusted dangerously close to 20. As a result, I flew four rockets with motor combinations that would not result in excessive altitude. First to go was the 38mm Thunderbolt from Giant Leap. This flew on a CTI G106 skidmark to a very modest altitude. Recovery was hot and heavy with an 18 inch chute. But this seems like too little under most circumstances, because the massively over-built rocket had some minor epoxy fractures as a result. Only J flights should come down on so small a chute.

For this flight, the payload was a small "spy camera." This camera has been sitting around for about a year, waiting to get used for the first time. It flew with a 2 GB flash card, and recorded the entire flight! It is exciting to finally have onboard footage from a flight. The video quality is quite good, but there is too much spin. Other rockets may perform better, as will a higher altitude flight. The video will be posted to youtube soon, but as previously noted, it is too large to upload to youtube right away without editing first. Most free online software is lousy or has watermarks. But it will be up soon, and posted here.

During this flight, ejection was rather late and the nosecone struck the airframe hard enough to crack in half. The nosecone fell near the rocket and was recovered, but can not be used again:



Here you can see my father who has always supported me in this hobby. He is an invaluable partner in rocketry crime; before launching with legit clubs, we sometimes had to find fields to "borrow." Obviously I no longer condone such activity. But more than once we had to make strategic retreats if a field got too hot or search deep into the woods to recover "giant" estes kits like the Super Nova Payloader. In the 10th grade, my father also took me on a trip to launch rockets in Nevada at Black Rock. This was an incredible experience.

Next I decided to launch my most complex flight of the day, a Viper IV with 4 D12-3 motors. Even with previous clustering experience, including several miraculous flights with D12 motors and composite motors mixed (how did that ever work?), I have had some bad luck with this viper. Last time, only two motors lit. The rocket recovered properly, but just barely. This time, I carefully set up the ignition system to be sure that all connections were perfect. Here is the setup:

(Don't cut the red wire... or the blue one!)

The rocket was placed on the pad, and launched with a serious heads up warning. Everything seemed to work well. The rocket flew to a pretty low apogee in the graceful arc of a black powder flight. The wind conditions were quite high at this time and the rocket flew over the stream and trees behind the flight line. But on ejection, the wind carried it back across, and actually resulted in a very close recovery just to the left of the LCO table:

After a very easy recovery, the only thing left to do was check and see how many motors lit up. It was almost certainly going to be at least three, simply because the performance was too good for just an E24. And here you can see the actual results; all four motors did burn. This is comparable to an F48-3.


The next flight used the first of the F240 motors. This motor burns out incredibly quickly, in less than 1/4th of a second! The Wildman Draco is a suitable kit for such thrust. The flight was fast, but not exceptionally so. The thrust duration was quick and powerful, but the overall impulse was just an F. So the rocket didn't go all that high. Perhaps this needs to fly in a smaller kit to really show off the power. Either way, it was a good flight going up. Going down, on the other hand, resulted in the same kind of recovery failure as last time; a stuck 'chute and semi-ballistic recovery. The lawndart results can be seen here:

It is a good thing that this field has about the best possible recovery conditions; incredibly soft sod and soil as far as the eye can see. Even at a high impact speed, and with a 6 inch core sample (see below), there was no damage to the rocket. It looks as if something is getting caught inside the rocket and preventing a good ejection. More work will be needed to figure out exactly what is going on. More BP may be the answer. Eject or blow it up trying, as the old saying goes.


Pulling the rocket out of the ground was not hard, but getting the packed soil and 'chute combo out of the rocket required about 100 lbs of force. (Standing on the nosecone and pulling as hard as possible.)

For the final flight, the little Art Applewhite Hourglass kit flew on an F12J. As always a fun and interesting experience.

Overall this was a great launch and a great start to the new year of rocketry. With some cleaning, sanding, and organizing, everything will be ready for next time. The youtube video footage will be posted as soon as possible.

1 comment:

Arjan said...

Looks like you had fun.
Sucks that some crashed themselves into the ground.