Sami Majadla - Pedepelin

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Sami Majadla

ES 147Idea Translation Lab

November 16, 2009

The Future of Leisurely Aviation

Since the beginning of history, humankind has always wanted to fly. Many civilizations

and tribes have learned how to sail across the seas and trek across the continents, but none have

been able to master the skies until quite recently. The first serious attempt in Western history to

analyse flight was made by Aristotle around 350 BC. He maintained that an object, such as an

arrow, could continue to move through the air only as long as a force was applied to it, and that

once this force was withdrawn, the object would stop. (Dalton, 14) Since Aristotle couldnt

conceive of any way that one could apply a force on an arrow from a distance (gravity was a

discovery to be made much later by Sir Isaac Newton), he concluded that things that fly must be

powered by something physically connected to them. With birds, bats, and insects, its pretty

obvious that the source of this power the muscles that allow them to flap their wings. However,

with the arrow, Aristotle hypothesized that the air must be what allows arrows to fly.

Specifically, he argued [that an arrow] travelled through the air by being pushed along by the

air rushing in to fill the vacuum behind it. He presumed that the air sustained the flight of the

arrow rather than retarded it (Dalton, 14), and believed that objects wouldnt be able to fly in a

vacuum because there wouldnt be air to push it along. Of course today, rockets and satellites

prove that this notion is false, and people understand that air is a cause for friction, not

propulsion.


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Leonardo da Vinci was the first to challenge Aristotles idea of airs impact on flight

(Dalton, 15), and instead proposed correctly that there was such a thing as air resistance (Allen,

4). Leonardo also made numerous designs for flying machines, though they were all either

helicopters or ornithopters (flapping wing devices). None of them would have been able to fly,

however, because he didnt understand the fundamentals of aerodynamics (Allen, 4) , and

becauseat least for the ornithoptershumans dont have a physiology that would allow us to

either flap fast enough or be light enough to stay sustained in the air (Shevell, 2). It wasnt until

Sir Isaac Newton that anybody theorized that air was a fluid like water (albeit a gas, not a liquid).

He did quite a bit to further the field of fluid dynamics, essentially setting forth the path for

airplanes that used air resistance to fly to be built, but unfortunately for him, his work was

ignored by the flight industry for its first century of existence.

In 1782, the Montgolfier brothers were gazing at the sparks and smoke that rose in their

fireplace, and thought of the idea of using a flame to carry a balloon of sorts into the sky. A year

later, the first manned flight ever took place in Paris, when a hot air balloon created by said

brothers traveled 5 miles across the city. A week after that, the French physicist J.A.C. Charles

flew the very first hydrogen balloon, also in Paris (Anderson, 5). It was finally proven that it was

possible for humans to fly, and hot-air balloon and hydrogen or helium filled dirigibles became

new vehicles that mankind could use. Until the early 20th century, they remained as more or less

the sole form of aerial transportation. Even with the rise of popularity in airplanes, it wasnt until

the Hindenburg disaster in 1937 that airships lost their significance in the aerial world.

However, there was a reason that lighter-than-air craft (LTA) attracted people for so long

before airplanes were built: they are simple and easy to understand. Anybody whos ever floated

in a body of water or, at least in todays day and age, held a helium balloon in their hands can get


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Engine driven airship

Pedal powered airship


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The zeppelin that I would like to build, called a pedepelin (or a zepedalin) to make the

combination of the pedal and zeppelin systems clear, would first and foremost be a lot smaller

than the examples given above. This is mainly because material science has come a long way

over the past century, and the envelope and undercarriage of the pedepelin can be significantly

lighter than what somebody in the early 1900s would have been able to create. Also unlike the

zeppelins of more than a century ago, the pedepelin would also have the ability to control its

height using ballastsbags of air inside the envelope that can be inflated and deflated to increase

or decrease the overall weight of the craft. In my model of the aircraft, the mechanism that would

be used to both pump air in and out of these ballasts would be controlled by the same pedal that

controls the propulsion of the LTA as a whole. There would be a simple three-way gear system

that would allow for the pilot to switch control between either horizontal movement of the

vehicle, upward movement (releasing air from the ballasts), or downward movement (adding air

to the ballasts). On top of that, there would be a 21 gear system to control the actual work that

the pedal itself does, more or less identical to what bikes today use. Below is a mock-up of the

above description:


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The big question comes in regards to the exact material that a machine of this sort would

be built from. While the gas that has been used in dirigible envelopes has been exclusively

helium for a while, I dont think that it would be such a bad idea to look into using hydrogen.

Zeppelins like the Hindenburg flew for thousands upon thousands of miles just fine without any

issues, so hydrogen will definitely be able to keep an airship afloat. The fact that its flammable

is the only reason not to use it, and in the pedepelin, this may not be such a big deal. Unlike the

Hindenburg and other large zeppelins, the pedepelin doesnt have engines, nor anything of any

kind that could potentially cause a spark that would blow the whole thing up. In fact, the only

moving parts that would be near the envelope itself (where the hydrogen is stored) would be the

pumps for the ballasts, which would be several layers of fabric removed from the helium. Some


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things that might cause a fire would be lightning, which wont ever be a problem because it

would be impossible to fly an LTA like this in a storm in the first place, missiles and other

weaponry, which again, I dont think will be a real problem, or sparks rising from a forest fire,

which I feel should be easy enough to avoid. In fact, the biggest fear of a fire would be a pilot

flying the airship who is smoking a cigarette and somehow manages to get said cigarette caught

in the gear mechanism while pumping the ballasts, which would end up taking said cigarette up

near the envelope, possibly burning through some of the fabric if the pilot stopped pedaling when

it got there, which would then cause the entire envelope to explode. As such, we can simply

make smoking and flying a pedepelin mutually exclusive activities.

The envelope itself would have to be made from polyvinyl fluoride (PVF)an incredibly

strong, weather and chemical resistant fabric that burns very slowy. It is what is currently used at

least in part for many airship envelopes, along with various parts of numerous planes and several

spacecrafts. There would be several hooks around the sides of the envelope in order to suspend

the seating and the pedaling system, along with the pilot, from the actual airship.

Quantities and price breakdown

Hydrogen weighs about 0.0857 kg/cubic meter. As such, when it is in an envelope

suspended in air, it will have a general buoyancy of about 1.1399 kg/cubic meter, since airs

weight can be averaged to about 1.2256 kg/cubic meter. Tedlar, one of the leading brands of

PVF fabric in the world, weighs about 2 kg/meter squared when it is a mil thick.

Say, for example, we wanted to create a perfectly round envelope rather than the cigar

shaped ones that are more maneuverable (this is simply to make calculations easier). We could


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give it a radius of 6m, which when filled with hydrogen would give us an upward lift of almost

1031.5 kg. The surface area, however, is 452.4 meters squared, which gives us a total weight of

around 904.5 kg. Therefore, an envelope of this size would be able to lift up to 127kg on top of

the envelope, which would be more than enough for a human being (for whom the average

weight is somewhere around the 70 or 75 kg mark), a seat, a pedal, a propeller, nylon fabric for

ballasts, and a light aluminum framework.

Of course less space could be used if other fabrics were used in tandem to make the

envelope lighter, or if a thinner layer were to be used. I havent done enough research yet on

light materials that can be woven into an envelope that can contain gases like hydrogen or

helium, and that would be one of the most important next steps that I could take. In the amounts

described above, the PVF would cost a total of around $85,000, and that would be by far the

biggest cost of the pedepelin. To add a structure to the envelope to get it into a desirable

aerodynamic shape and to add the hydrogen we need, a pedaling system, ballasts, airpumps, and

a propeller would probably raise the total price of the system to be just above $100,000 (mainly

because wed need more PVF to get a sleeker shape). Of course this price can go up or down

depending on whether or not the quality of the fabric that is discussed here is up to par or not. It

also wouldnt be too expensive to replace this system with an actual engine (at least for the

propeller).

While this may seem like a lot of money, it is quite cheap in comparison to other options

out there. The next cheapest non-hot-air based airship is already above $2,000,000, and the

closest comparable airship in terms of price is the Skyacht, a hot-air blimp that will be selling for

around $150,000 in the near future (personalblimp.com). While hot-air blimps have the benefit

of being able to use much lighter materials since air leakage isnt something they have to worry


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about as much, the envelopes themselves need to be much larger, since hot air isnt anywhere

near as light as hydrogen or helium are. Of course as a result of hot-air blimp envelopes being

open, they can be completely deflated and rolled up when not in use, allowing for a much easier

transport of the blimp from place to place. At the same time, however, once unfurled and flying

through the air, hot air blimps cant maneuver quite as well as rigid zeppelins can.

Project Future

While building and flying a pedepelin as described above is much cheaper than what is

readily available today, it isnt quite as cheap and definitely not as small as I was hoping a flying

bicycle of sorts would be. As such, there were other designs that I considered. These designs fell

mostly into two different categories. The first was one where the envelope was designed to be

able to lift just below total weight of the aircraft, and other supplementary systems would be

used to keep the machine as a whole afloat. There were two different hybrid airships that

combined zeppelin and helicopter technologies that I thought of. They are both relatively similar

to two different designs that are in existence. One is the Piasecki PA-97, which crashed after

several months of testing due to a structural failure, and the other is the SkyHook JHL-40, which

is currently in development as a collaboration between SkyHook International and. Both are

pictured below:


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Piasecki PA-97

SkyHook JHL-40

Both of my helicopter/airship hybrids are drawn below. For propulsion, they would either

be linked with an extra vertical propeller like the pedepelin design, or the horizontal rotors would

have the ability to tilt in different directions to allow for horizontal movement.


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Another design that is fundamentally similar to the above two is one that combines

ornithopter and airship technologies to create more farfetched aircraft like the one below. Since

almost the entirety of the lift (like the other hybrids I drew above) would be achieved by the

envelope, it shouldnt be too hard to be able to achieve flight with large wings made of feathers

(or another decent material) and a strong spring system. It would also be cool to design and paint

the whole system to look like a bird so that the pilot would essentially be flying in a giant

feathered creature.


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Just to be clear, in all the of the aforementioned systems, when not pedaling to keep either the

wings or the copter blades in motion (depending on what the model is), the airship would begin

to descend.

The second category of flying machines that I thought might be worth pursuing is one

that is a bit simpler than the above examples. Its a design where one, to put it simply, attaches a

significant amount of helium balloons and a propeller to an object such as a bike (ala the Pixar

movie Up). This seems like it would be technically much less challenging than building a true

airship, and it would be a lot cheaper to produce as well. Getting down would simply involve

either shooting some balloons with a pellet gun or cutting their attachment from the frame of the

bike. Similar things have been done numerous times with furniture (such as lawn chairs) or

harnesses. In fact, it is a common enough practice that it has earned itself a titlecluster

ballooning. Why not try the same thing with a bike? Whether its feasible or not, it certainly

would be really fun to be able to fly for cheap. What the research that Ive done so far for this

project has taught me, however, is that I need to do quite a bit more before I can claim to have a

design that is worth pursuing further.


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Works Cited

Allen, John E.Aerodynamics the science of air in motion. London: Granada, 1982. Print.

Anderson, John David.Introduction to flight. New York: McGraw-Hill, 1985. Print.

Dalton, Stephen. The Miracle of Flight. London: Merrell, 2006. Print.

Personal Blimp Frequently Asked Questions. Skyacht Aircraft, 2008. Web. 17 Nov. 2009.

.

Shevell, Richard Shepherd. Fundamentals of flight. Englewood Cliffs, N.J: Prentice-Hall, 1983. Print.

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Sami Majadla - Pedepelin