Re: Slow planes was: Battle blimps

B Lin wrote:

> Another possibility is some type of "altitude bladder".  Since the
lift is generated by helium displacing an equivalent volume of air, if
you had a large center bladder that could be contracted or expanded as
needed, you could shift the amount of air displaced without having to
release gas.  You would just compress the helium in the bladder until it
was of high enough density to stop you from rising.