Short answer: What I think you want to do is not really possible.
Breaking it down:
1. Something like 15886.5 cubic feet of helium is required to lift
1000 pounds.
2. A cubic foot of helium will lift about 28.2 grams. Hence the
formula to calculate the answer to 1 is:
(n cubic feet)(28.2 grams/cubic feet)(1/448 pounds/gram) = n *
.06294 pounds
So plug in however many cubic feet you have, times .06294 and you
should get a close approximation of how many pounds you can lift.
Alternatively,
(n pounds)(448/1 grams/pound)(1/28.2 cubic feet/gram) = n *
15.886524 cubic feet
So plug in 1000 and you see the answer is about 15,886.
These are approximations; you should use probably construct a balloon
of 15,900-16,000 cubic feet capacity for safety purposes, plus
whatever is necessary to cover the additional weight of the empty
balloon and the cabin you plan to rig for it. For smaller latex
balloons you need to take into account backpressure from the increased
density of the gas inside, but really large balloons (as we shall see)
are made of thin plastic sheets, and are inflated from a limp state so
they have no backpressure.
3. Heating the helium will make it even lighter in comparison to air,
and hence it would rise more. In essence, you would be creating more
empty space in the helium, or in other words, making the same weight
of helium take up more space, so it would rise even more in relation
to the heavier air. However, it is not really necessary, it would just
cause the vehicle to move faster or require less helium (it should not
be fully inflated if you plan to heat it.) Heating is not advised, in
any case, because of the unnecessary inherent increase in danger.
4. There are many different fabrics you can make the envelope out of.
This site, giving a history of ballooning, describes several materials
used in the process of creating balloon technology, including paper
and cloth or silk, and in 1935 the National Geographic Society's
"Explorer" took two men in a pressurized aluminum sphere to 22
kilometers high using a balloon made of rubberized cotton.
But modern balloons use very thin, very light, clear polyethylene
plastic; as described here:
"The Space Launch 1 rocket was fired at 60,000 feet from a large
high-altitude helium balloon made of clear polyethylene plastic over
100 feet long, but thinner than a sandwich bag (only 0.35 mils thick).
At its design altitude of about 130,000 feet, the balloon, which has a
volumetric capacity of 141,000 cubic-feet, would have expanded to 65
feet in diameter."
http://www.asi.org/adb/06/09/03/02/107/halo-success.html
and here:
"The balloon is made of a very thin, clear colorless plastic film,
similar to that used by dry cleaners. Each layer is only .8 mil --
about half the thickness of a human hair! At the top of the balloon,
there are four layers of this poly film, tapering down to one layer on
the bottom.
But the strength of the balloon comes from its construction in pieces
or "gores" -- some 178 of them. Between each gore is a weight load
tape that holds the weight of the payload."
http://www.remax.com/sports/ballooning/faq.html
But as you can see from the detail provided in the second description,
material is not the only important thing to construction of a balloon
envelope. If you are really ambitions, you can construct gores
yourself out of polyethylene sheeting, sold for flood protection, or
drop cloths for protecting surfaces from airborne particles or paint,
at your local hardware store. Online, you can purchase at:
http://www.homedepot.com
(I can't post a direct link, but search for polyethylene and enter
your zip number to browse through their products, particularly the
sections "Paint/Drop Cloths-Tarps/Utility Tarps" and "Paint/Drop
Cloths-Tarps/Plastic Sheeting").
Construction of the gores is described here:
http://www.sciencebyjones.com/hot_air_balloon.htm
And pictures are shown here:
http://www.eaztep.fsnet.co.uk/balloon%20upload/ulthm2.htm
Be aware of the FAA regulations, though, in flying any type of
aircraft:
http://www.chem.hawaii.edu/uham/part101.html
5. Building and filling your own balloon is unfortunately not really
plausible, beyond at the very most bearing the load of a single
person. You can find information on getting the latex balloons here,
under the section "Sources for Latex Balloons":
http://www.chem.hawaii.edu/uham/lift.html
The following section describes sources for helium, but notes that it
is dangerous to deal with and expensive in large quantities. You can
also find tables that take into account various pressure changes from
the atmosphere, the altitude, and the like, going up to a 24-ft
diameter balloon with a volume of 204,976 liters lifting 463.79, as a
maximum.
For the thin poly plastic balloons, you will need to have them
professionally made; you can find envelopes for sale at perhaps
prohibitingly expensive prices at the following locations:
Various gas balloons 'classifieds':
http://www.sydcom.net/users/micki/gas.htm
http://www.flynh3.com/8172J.htm
(if anything I would think the $4000 model with a lift of 698 lbs is
around what you'd be looking for, or else the $3000 envelope-only with
a capacity of 30,800 cubic feet.)
Linstrand Balloons:
website: http://www.lindstrand.co.uk/gas_balloons.htm
dealer locations: http://www.lindstrand.co.uk/world_dealers.htm
You may also want to check out this page, "The Differences Between Gas
Balloons and Hot Air Balloons":
http://www.aibf.org/gasrace/differences.htm
6. It does not seem feasible to self-construct personal helium-based
aircraft at this time, based on the reasons described above.
OTHER INFORMATION
This site provides an excellent description of the principles behind a
helium (or otherwise lighter-than-air) ballon:
http://www.howstuffworks.com/helium2.htm
You can find a good deal more information about gas ballooning in
general here:
http://www.aibf.org/gasrace/gasballooning.htm
And an directory listing:
http://www.thirtythousandfeet.com/airships.htm
Finally, a rather interesting antedote I discovered along the way
about a man who decided it'd be a good idea to travel at the speed of
sound without anything but a jumpsuit and a parachute, jumping from a
balloon that would have achieved a record height in and of itself:
http://darwin.codefab.com/pipermail/random/2001-March/000659.html
Search Strategy:
://www.google.com/search?q=helium+weighs
://www.google.com/search?q=%22helium+balloon%22+%22balloon+made+of%22
://www.google.com/search?q=heating+helium+envelope
://www.google.com/search?q=%22purchase+polyurethane%22
://www.google.com/search?q=polyeythelene
Thank you for your excellent and interesting question, and sorry to
bludgeon (but hopefully not shatter) your dream. Hope this helps you
on your quest. |
