Put it all together, and what have you got?

The answer is a somewhat shabby looking near space balloon payload. It is all working brilliantly though! You can see in the pictures below how the parachute bay folds open and how there is a string that wraps around the soda bottle to a 2 prong hook to hold the hatch closed during the ascent. There's a servo motor inside that pulls the hook closed during ascent and pushes the hook out when the set altitude is crossed twice (once going up primes the circuit and then on the way down the servo pushes the hook out letting the parachute hatch be opened by the force of wind).

Parachute bay open, cameras in the green section

GPS antenna on the left, pressure sensor where the coiled wires are in the middle

2 prong hook holding parachute bay closed by the string

Cellular antenna from EAD-LTD.com

Last weekend I also did a test inflation and tethered flight of the payload I had completed at the time. During that inflation I used a nitrogen regulator on a 130 cubic foot helium tank. In-between the regulator and the balloon was just a section of air hose, which worked alright to inflate. The problem with that setup is that I had no idea how much weight the balloon was lifting. I had to use my hand to keep the balloon sealed to the air hose, so we just filled the balloon until the tank was empty. I've seen on a few websites that 1 extra pound of weight is enough to give the balloon a 1000 ft/minute ascent rate. Sure, I could just inflate the balloon all the way and let it rocket up until it bursts, but the less helium I put in the higher it will go (it has to be able to lift the payload of course and it has to make it through the cold tropopause without getting too brittle). With all that in mind I created a new end for the filling hose that weighs just under 1 pound. The filling end fits snugly in the balloon opening and with the help of a hose clamp it will add exactly one pound of weight to my payload. Now I just hang my payload from the red lever on the filling end, fill up the balloon until it starts to lift the payload off the ground, tie everything off, and let it go.

Regulator, hose, and filling end

The filling end is a 3/4" brass plumbing shutoff valve, and a 3/4" to 1/2" adapter to connect to the hose. On the balloon end of the shutoff valve I have added some automotive gasket material and silicone to make the end round instead of the hex bolt shape. It's very difficult to get a good seal on the balloon with the hex shape.

Looks like this time I was early on my deadline! Tomorrow I'm going to do lots of testing and then put the finishing touches on the payload. It will look a lot nicer once I get the space blanket wrapped around it. It's kinda like a classic car without the chrome bumpers right now. See you next time space cowboys!