KCØJHQ's Balloon

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Flight technical notes:

EOSS 55 was a flight test of a KC0JHQ-built 0.35 mil thick polyethylene floater balloon.

The balloon is of the simple 'pillow' design (made from two rectangular panels, sealed on four edges. The non-inflated dimensions of the bag are 12' wide x 50' tall. The inflated diameter is 7.5'. The approximate fully inflated volume is 2100 cubic feet. I have added a filling duct, like on the commercially available plastic balloons. This will add 0.6 lbs to the weight of the balloon, to a total of 2.6 lbs.

Mark Caviezel, KCØJHQ

Filling the balloon will be accomplished via a helium diffuser at the end of a garden hose. I'd like to use approximately 95% of a single T-bottle of helium to fill the bag (the last 200 psi always takes forever to drain). This will give us 18 lbs buoyancy on a total vehicle mass of 12.5 lbs (neglecting mass of helium). This equates to 44% free lift. In a poly floater, there is no penalty for an aggressive amount of free lift, indeed a faster ascent rate will benefit the flight plan with the prevailing winds occurring now. The clutch will be installed 28' down from the top of the balloon.

With a total flight compliment of 9.8 lbs, the balloon should ascend to about 61k feet and float. With the winds over Colorado as they are at this time of year, that should just get us over the fast moving winds lower down.

One technical objective of the flight is to evaluate the balloon's behavior approaching and at float altitude. Unlike latex balloons, the polyethylene floater is able to vent its excess buoyancy gas after it reaches full inflation.

The nominal flight plan is to issue the cut down command once the balloon reaches a distance of 50 miles from the launch site. It is hoped that the balloon can attain float altitude for at least 5-15 minutes, but recovery is paramount, so a commanded cut down at the 50 miles radius is the game plan. There will also be a two hour timer (timer activated by lanyard pull immediately before launch) as a secondary cut down system.

About 23' of uninflated balloon will be “downstream” from the clutch. The two hour timer will be attached to the bottom of the balloon, and the EOSS parachute will be attached immediately below it. The KC0JHQ payload (about 1.7 lbs) will be attached to the fill tube. The 'JHQ payload will be configured for APRS packets on request, and DFing tone on request.

After cut down, the EOSS flight string makes a nominal descent on parachute, its CW beacon being the 'fox' for the 'foxhunt'.

The 'JHQ payload will act as a 'tipper' to invert the balloon, which will then vent it's helium and descend. I (along with Karl N7MXO and a back seater) will track the balloon with APRS packets. There is no prize for hunting down the balloon, but if anyone has APRS tracking capability and wants to help, just let us know. Indeed, given the reliability of logging all the packets in a mobile environment, I would love it if any N. Colorado area hams could set up their fixed based packet station to log all the KC0JHQ-11 packets coming down. (contact me at kmcaviezel@yahoo.com if you can help with this) The exact descent rate of the 'JHQ payload (descending with balloon streamer, no parachute) is not known, but expected to be modest.

Technical risk: note, this is a test flight. Some previous testing with similar balloons has shown promise, but also some leakage. This balloon was made with different methods that should greatly reduce the leakage. However, if this balloon does have an appreciable leak rate, it will ascend at an ever slowing rate, then start to slowly descend. This will put the balloon into high speed jet stream winds for a greater exposure than with a nominal ascent. Regardless, cut down command will be sent at 50 miles radius from the launch site. I'd love to have 0-5 mph winds max for filling the balloon, but I estimate that winds as high as 10 mph at the launch site MAY BE acceptable. It is possible that higher winds or gusts may destroy the balloon before launch. To save the planned fox hunting event, a latex balloon should be brought as a back up.