Superpressure balloon valve / was Re: [GPSL] K5NOT-11 WSPR Balloon Failure

Hank Riley

Looking at the cross section dimensioned drawing and the photograph, it's pretty certain the tetroon was filled through an internally threaded port. After removing the fill tube from the port, the calibrated pressure release valve was threaded into the same port using the  narrow, OD-threaded valve nipple, thus sealing the balloon.

This method allows for a casual (not requiring precision to reach a given equilibrium altitude) and "overfilled" (compared to a valveless flight) inflation of the tetroon.
The overfilling would of course result in a faster ascent.

So the equilibrium height would be determined by the valve release setting, not by a precisely measured amount of fill (as measured by gas volume delivered, or indirectly by the value of free lift produced at the launch site).

On Saturday, July 18, 2020, 11:44:33 PM EDT, James Ewen  wrote:

Is this valve to be used for filling, or venting?

It sounds like the intent was to allow for over fill for rapid ascent, and then release pressure at altitude.