john smith <jsmith@[EMAIL PROTECTED]
> wrote:
> Jim, thanks for the followup postings.
> I am courious as to how Dan plans to control ascent/descent?
> Is there going to be a ballonette inside the envelope?
Ballonette's aren't actually used to control buoyancy; they are used to
allow for lifting gas expansion as an air****p rises. As an air****p rises
the atmospheric pressure drops of course, so either the lifting gas has to
be vented (if the lifting gas container can't change volume), or the
container has to expand in volume to maintain equal pressure with the
atmosphere, or the container has to be strong enough to hold the large
pressure differential. That last is needlessly difficult. So since most
air****ps now use relatively expensive helium, venting is out of the
question, so ballonettes are used. When using hot air, venting is a
simpler
solution and not as costly.
Ascent and descent are almost certainly going to be controlled in the same
manner that hot air balloons use: by increasing the bouyancy by applying
more hot air (or dropping ballast) to ascend and venting of hot air to
descend (or allowing natural cooling to take its toll). Fortunately hot
air
is much cheaper than helium.
If you are interested in more details, I suggest you review the paper they
presented at an AIAA forum:
http://www.personalblimp.com/misc/atio2003.pdf
Their patent, 6,793,180, can be examined at the U.S. patent office online:
http://www.uspto.gov/patft/index.html
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