h a l f b a k e r y
I think this would be a great thing to not do.
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Change the volume of a hydrogen or helium airship to
its altitude. Assuming the skin of the airship is made
flexible material, internally connect the front and the
end of the airship with ropes. Pull the ropes mechanically
change the volume of the airship. If a traditional
is used instead of an airship, the support ropes can be
bunched together at the top of the balloon. This can be
then pulled downward mechanically to change the
volume. Of course bottom of the balloon has to sealed
unlike a traditional balloon to prevent the gases from
escaping.The airship/balloon will not have
to carry ballast, use
thrust vectoring or guide ropes to take off or land.
For [Wagster]. Involves changing the temperature. [pocmloc, Jan 27 2010]
Existing art - PV Stabilized High altitude balloon
[MisterQED, Jan 27 2010]
Compressable baloon drawing
[kneeslider, Jan 27 2010]
Prior Halfbaked Art
Internal balloons are squeezed to increase density, reducing lift. Sound familiar? [goldbb, Jan 27 2010]
Apparently some Israeli thought of this seriously a few years ago [pashute, Mar 08 2010]
||Of course, use heat to change the density! I'm sure that hasn't been done before.
||I'll have to find the post, but I know I
suggested a solar powered pump to pump
excess hydrogen into a high pressure
storage tank during the day to allow the
envelope to survive solar heating cycles.
||I found the post, which covers compression with a pump. If you want to compress using the existing envelope, you will need a heavy envelope. (-)
||I should have clarified it a more. What I meant was-
physically reduce volume of the airship. Assuming the
skin is made from flexible material, internally connect
the front and the back end of the airship with ropes.
Pull the ropes mechanically to change the volume. No
pumps are necessary. (I am editing the post to
include this explanation)
||Maybe a balloon made of wire mesh memory metal with a plastic liner.
Although I must admit there is an appeal to the idea of sweaty shirtless sailors girding their turgid dirigible with thick and bristly jute ropes. Put your backs into it, men!
||[bungston] Somehow all of the adjectives in your second sentence seem to want to migrate to the left to modify the sailors.
||kneeslider -- you've left out an important requirement of the airship skin... not only must it be flexible, but it must also be inelastic.
||The only material that comes to mind is mylar. Based upon personal experience, I would expect a mylar balloon, when squeezed firmly, to pop, before it appreciably compresses the air within.
||I was thinking of composite material. In case of
the balloon, circumferential kevlar strings may be
implanted into the fabric (not sure of what kind)
to make it inelastic but still have the flexibility to
pull the top down. You have probably already
realized- the skin does not need to stretch or
compress for the process changing the shape, so
composites can be used to make the skin very
||Density ballasted airship is also a nice idea.
||[pashute] love the link, especially this excerpt:
||"Air from the atmosphere is compressed into the rigid shell of the aircraft to add weight. This is accomplished by using pneumatic motors driven by stored compressed air that powers air compressors."
||I'd suggest you pick up a copy of The Mad Scientists' Club by Bertrand Brinley. One of the seven short stories, The Great Gas Bag Race, involves a similar premise. The members of the eponymous club devise a helium-filled balloon which they can adjust with a compressor, which wins them the "Hot Air Balloon" race at the county fair.