If you are interested in airship and balloon construction
in general, you might want to take a look at
XLTA.org.
The the discussion below focuses on the Personal Blimp
project.
A more complete description of the technology used
in this project can be found in a
conference paper
presented at
AIAA's 3rd Annual Aviation Technology, Integration, and Operations (ATIO) Technical Forum
in Denver in November of 2003.
One of the unique features of the Skyacht Personal Blimp
is the use of a foldable hull structure. (We liked the idea
so much that we've got for a
patent on it.)
The Personal Blimp hull
structure has three main components: 1) the fabric envelope,
2) a set of flexible ribs embedded within the fabric,
and 3) a tensioning line that runs along the central axis
of the hull.
The key trick to the hull is that it is a classic
"tension structure" wherein the ribs are under
compression and the fabric and tensioning line are under
opposing tension. Tensions structures have been
in wide use for centuries. Probably the most common example is
the folding umbrella.
What is new and different about the Personal Blimp hull design is the
ease with which one can create a lightweight, sturdy,
self-supporting (no fans required) airship envelope.
For instance, as part of our ongoing development work,
we have built a roughly 1/4 scale model
(25 feet long and 17 feet in diameter) that encloses
3,300 cubic feet (about the volume of a 2 car garage)
and weight a grand total of 21 pounds.
Pretty spiffy, eh?
Here's how it works --
The fabric of the envelope has several (let's say a dozen)
continuous, tubular sleeves sewn into it
running from nose to tail. The ribs (i.e. long, fairly flexible
sticks) are inserted into the sleeves. The ends of
the ribs are held together at each end (for instance by
rigid end cone structures or by the fabric itself.)
The tensioning line is then connected between the two ends
and the whole contraption is inflated by pulling on the
tensioning line. As the tensioning line is made shorter
the ribs are forced to bend or "bow" outward.
The envelope continues to expand until eventually the
fabric is pulled taut.
The end result (using ribs of uniform cross section) is
a an object roughly the shape of an American style football.
Abstractly, one can think of the Personal Blimp hull as a pair of gigantic
umbrellas pointing
in opposite directions with their ribs running continuously
and the handles of the umbrellas hooked together.
Different shapes can be designed by varying the composition
and/or cross section of ribs along
their length. For instance, making the ribs more flexible
towards the nose gives a blunter shape to the front of the ship.
Relatively stiffer ribs can also be used to get a longer, skinnier shape
than the one shown in the pictures below.
The structure provides excellent support for aerodynamic loads.
For details, please see our page on
wind tunnel testing.
