Monday, April 18, 2011

KJ6KUV-11 flight and successful recovery!

KJ6KUV-11 was launched yesterday from Ojai, California at 0820 PDT and successfully recovered 84 minutes later near Oak Park, 53.6 Km to the south-east! Check Kyle's blog for details, but I think all the efforts can be summarized with one single picture:


During the whole flight, the balloon was able to steadily report its position via APRS and the trajectory could be followed at Between 12-16 Km altitude, the balloon caught the jet stream and sped up quite a lot as you can tell by the more spread-out points on the map!

kj6kuv-11 trajectory

The tracker was a Trackuino board with a Venus 634FLPx GPS and a Radiometrix HX1 300 mW radio transmitter. We were not sure the HX1 was going to deliver enough power to reach any digipeater from that high up. Well, sure it did... At its peak altitude (20 Km), the signal could be heard from Phoenix, Arizona, which is... 597 Km away!

kj6kuv-11 hx1 range

We were also not sure the Venus 634FLPx would report its position above 18 Km high, since many manufacturers seem to get the CoCom limits all wrong. But then again, the above picture proves how the GPS worked perfectly at 20036 meters.

Here are some flight stats I gathered with WBALTRAK. This is a plot of altitude versus time:

kj6kuv-11 altitude vs time

The ascent rate was smooth and constant at about 500 meters/minute. After the balloon popped, the payload fell at a vertiginous 1000 meters/min and steadily slowed down as the air density allowed the parachute to deploy. The payload landed smoothly at 294 meters/min:

kj6kuv-11 vertical rates

The speed was about 38 Km/h average and it reached peaks of 100 Km/h (about 60 mph) while the balloon was caught by the jet stream:

kj6kuv-11 speed

This was a lot of fun to track :)



  1. Cooool!!!!
    Radio horizon is more than theoretical limit with the effect of atmosphere - for 20036 m altitude is 4.12*sqrt(20036)=583 km!!

  2. We got it back! Go little Trackuino!

  3. Amazing work Javi !
    I use your code for a atmega644p based board !
    I finally have finished with electronics and now Im heading for the payload build..
    Check my blog: