Our “first draft” altitude control system worked well, but it had a number of problems… First off, it was awkward to use, second, it was larger and heavier than it really needed to be. Finally, it required a separate cutdown system. After the success of the first draft we wondered if we could do better. Last Autumn David, Ken and I started to work on the ACS v. II which was to combine the venting system and the cutdown mechanism all in one convenient and simple house package. David created the following video to illustrate the central concept:
When the animation starts the piston is in the “Closed & Locked” fully extended position towards the left hand side. The balloon nozzle is attached to the blue tube on the left. Although the balloon nozzle is not tied off, the helium cannot escape because the tube is blocked by the presence of the dark grey piston disk. When a release of helium is desired, the piston is drawn back towards the right by an actuator, to the “Open & Locked” position. In this position the grey piston disk (3) is to the right of the holes in the tube walls. Helium can flow from the balloon, through the hollow white part of the piston (5), and out though the holes in the piston and tube walls.
If we want to stop the flow of helium we need simply return the piston to the “Closed & Locked” position. Finally, if we want to release the balloon entirely (cutdown), we pull the piston back to the right all the way to the “Release” position. This removes the hollow white portion of the piston from contact with the blue tabs (4) which are then free to bend inwards (not shown in the animation). This allows the blue portion of the tube (1) to disengage with the white section (2) with a modest force. It is a very clever design!
The actuator, electronics, battery and control panel will be housed in a “sled” that slides in to an extension of the white tube on the right. In part III I’ll give an update on how this design is all coming together in the real world!