A tetroon is a tetrahedral shaped balloon. It is normally based on an equilateral 4 sided pyramid.
This is my 2nd attempt at a speadsheet to do some of the design work for a tetroon. The volume that you nominate in the spreadsheet is for a regular, flat sided tetrahedron. In reality, when inflated and under pressure the actual volume will be 3 -6% larger than that of the flat sided design.
It is completely unproven! Use it at your peril!!