AT CAD Team/AT airship
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[edit] Usefulness as AT design
First off is the purpose of the airship; it is to be used primarily as a vehicle for travellers (ie around the world travellers, and those that at the moments use campers (hence the name "AeroCamper" in the wikiversity/blog article ) The vehicle is particularly useful since air is a medium with low drag, and the LTA-way of flying of airships and the energy scavenging make this vehicle extremely cost-effective, particularly over longer distances. Giving that airships can also travel over any terrain (water, dense vegetation/forests, bumpy or rocky terrain, ...) it can also be very useful for people living in hard to reach areas (ie rainforests, ...); at the moment helicopters and sometimes bush aircraft are often used, but these are very expensive. I think that airships can make good alternatives to aircraft but it depends a little on where one's focus lies; ie a blimp will always be less fast but the energy needed to propell the craft is far less and none of the energy used will cost anything (due to the solar panels, pedals, ...) Also, the idea is that it becomes a privately owned aircraft, thus unlike most airplanes. It however assumes though that we can reduce the initial costs far enough.
[edit] Construction
I did some basic estimates for the weight of the gondola, which I guess would be around 450kg empty, and 875 kg full. Its capacity would be 2x 90kg passengers, 90 kg of ballast, and 90kg of cargo. I estimated that the envelope would weigh 250 kg at the most, meaning around 1000M³ of hydrogen would be required.
The shell of the airship is not a self-supporting floor. Instead, a "catwalk" is present which is self-supporting, and a rail system has been added for safety (prevents anyone walking the catwalk of falling off and touching the shell) The persons occupying the airship are hooked unto the rail system by means of a climbing harness. The whole idea of this is that by not having sel-supporting floors, the gondola shell can be made very light and cheap, functioning only as a protection against the weather.
[edit] Attachment of gondola
See http://www.skytamer.com/2.6.3/Blimp%20layout%201600.jpg
[edit] Embarking/disembarking the airship
Passengers would embark by winched in from the bottom (using a climbing harness, see the image on the right)
The winch would be powered by a seperate electric engine. The engine would be commanded remotely (perhaps by RFID), so loading can be done even if there is no one in the airship to engage the winch.
In general, the winching system can be based on the AT Interstate Traveller, and the steering can be similar to a combination of the AT e-velomobile and the proposed ship control stand (see AT CAD Team main page). The steering is thus done by hand, but it would be useful to also include a blocking of the steer to allow it to attain a same plotted coarse, atleast for a while.
The left/right winch is placed seperatly from the respectively left and right rails. Rather than moving the entire winch over the rails, a carabiner is used on the person's harness to lock unto a simple movable ring on the rail, or unto the winch if the person wishes to disembark. The winch/rails are imperative to the design as it allows the storage of supplies (instead of storage cabinets), the loading/unloading of personnel, and the mooring of the airship.
[edit] Lift
The main lift would come from the LTA gas (hydrogen) in of the airship's envelope. The airship has an envelope that contains so much LTA-gas that the airship continuously wishes to ascend. 2 electric motors (of 1-2 HP) continuously prevent the ascend by propelling air upwards. The aircraft thus remains airborne all the time, at some 10m above the ground.
It should be noted though that the amount of LTA-gas should nonetheless not be too great neither. This so that less effort is required from the propellers to keep the aircraft at the 10m above the ground.
The airship can easily ascend by reducing the power output of the engines. This is very much needed aswell as the vegetation layer can reach upto 35 meters above the ground.
Note that the envelope is generally at optimal lift capacity at 85%; the remaining 15% is empty to allow somewhat greater filling when the weight of the airship is greater for some reason (ie more cargo aboard, ...).
[edit] Propulsion
The propulsion too happens by means of the two (1-2 HP) electric engines. The engines are placed inside the airship (on the drawing, "engine" thus refers only to the propeller). The engine is on the inside to prevent having too much weight on the (rotatable) propeller shafts.
The electric engines are powered by means of a electrochemical battery, which is recharged by PV (or LSC) solar panels, pedaling, and perhaps a wind turbine function. The latter would be possible if the airship has been moored by means of the 2 winches. Then, the engines can work in reverse and harness the wind energy.
If the battery fails, a person (or even two), or the PV panels alone can generate enough power to still keep the airship flying at a same altitude.
Regarding the pedaling system: a lever arm to increase the efficiency can be added (see http://www.appropedia.org/File:Lever_arms_for_bicycle_cranksets.png )
[edit] Control
The ship control stand is the main control organ for the airship. It contains no joystick (only pedals). See AT_ship_control_stand
Finally, there is the idea of a guidance cable for use in the city (ie between high rise buildings). It is similar to the "chien de mer", which is a curved carbon foil under the water’s surface, linked to the balloon’s car by a long cable whose length can be adjusted (from 20m to 50 m) and which acts as a centreboard. Like the chien de mer, this "chien du chemin" assists the crew in controlling the flight path, but does so more directly. Rather than using a center board, the line is connected to a remote controlled trolly, which tows the airship (this idea was based on the Trampe, see http://www.trampe.no/english/ ) The idea is that the system is particularly useful for "parking" the airship near a city without fear of collision to buildings. Also, it may be possible to use the trolly to automatically direct the airship to a specific location with the city (ie building, ...). This as the destination may be chosen with a transmitter inside the airship, hereby automatically instructing the trolly to go to the desired location.
[edit] Battery management system, ballast and water source
Regarding the battery management system (= system for keeping the batteries at a good temperature): a waterbox totally encloses the battery. The waterbox can't be cooled itself (nor heated) but will serve to eliminate temperature fluctuations. The waterbox also serves as a watersource for the passengers, and as ballast (40kg can be released)
[edit] Heating
Although the engines are electrical, there is still atleast 30% of the energy converted to heat, so we can use this to heat up the airship. The engines are inside the shell of the propeller pods, and a hollow tube around the axle can then transfer the heat of these to inside the gondola as needed. This is done by means of 2 electrically controlled valves; one at the top of the hollow pipe, and another on the inside of the airship.
[edit] Safety
In certain situations (ie repair, storms, ...) the craft can land, but it will require the emptying of the gas, preferably by a pipe that stores the gas in a underground tank temporarily. As for keeping the airship out of the wind when it is not used, there are also other options. First, there's the option of simply storing it in a large hanger, while still in the air (hanger needs to be atleast 20m high). As a alternative, I also noted the anchoring cables, these can be placed when there is no hanger available, and when there is not much wind. The anchoring cables lower and are attached to either a metal ring fixed to concrete feet, or they are attached to any natural objects fixed to the soil (ie trees, ...).
A main safety is available in the form of the "emergency lift" procedure (see image 3 of my article), this provides additional lift in case the airship goes down unexpectidly by rotating the propellers downwards. This provides additional escape time. There are also additional safeties, ie first of all the escaping by means of the winch, and also an inflatable "bag" (see Prototype this, episode 9 (http://en.wikipedia.org/wiki/Prototype_This! , http://www.grandideastudio.com/portfolio/pt-extras/ which can be used on the whole gondola. An extra safety is also present in the form of a emergency release valve; the latter allows the emergency release of a certain amount of air per turn. This is useful if the propellers malfunction and provide too much emergency lift, if too much hydrogen was tanked, ...
[edit] Maintenance and in-flight repair
This can be done by means of the outside rail. Ie in case there is a leak in the balloon, or if the straps are coming loose the hatch drawn/rail are the only things that can allow repair (ie the ceiling can be climbed from here). Again, landing also isn't possible with the airship, so repair can never be done on the ground.
[edit] Refueling stations
The refueling stations supply electricity and hydrogen gas at 50m altitude. Hydrogen gas can be made on the spot in the fuel station by electrolysis of water. It would be possible to place the hydrogen generator in the airship instead (especially since a potable water tank of ie 40L should allready be on board), but given that this generator increases the weight of the airship, the hydrogen generator is instead placed at the station. In addition, the refueling station may also be equipped with height sensors to ensure that the airship leaves the station with minimal continuous lift, so that as little as possible energy needs to be used by the propellers to keep the airship down.
