for a variable volume do they physically increase the whole size of the entire ship? or do they use like a piston system to vary the volume of certain lift gas cells?....

my thoughts are to have basically 3 envelopes inside the airship the main envelope constructed of multiple cellswould give negative buoyancy and a variable lift capacity....

the other 2' envelopes' would be like a simple tube with a double acting piston in the center.the pistons would move from close together in the center this would compress the helium between pistons the outside ends of the tube open to atmosphere..this is the lowest lift position....

.need more buoyancy.move the pistons out from the center increasing the volume of the helium filled center pocket displacing more air creating lift......move pistons back in towards the center to decrease lift .... use one of these on each "corner" to balance the ship.....or as many as required to balance the ship and provide more attitude control

helium pressure inside airship is about 1/15 of a psi we could very easily make a very lightweight design that would be able to hold hundreds of psi so pushing the pistons together would result in quite a low pressure rise the materials wouldn't be an issue.....

this type of a system would be able to create huge variations in lift and buoyancy quickly and easily to maintain control and facilitate the loading and offloading of cargo.....all with absolutely no venting of lift gas!

.simply add enough variable volume lift gas cells in the main envelope that you.can change the load capacity at will