Airships – for Simple and Sustainable Aviation



Part I:

The Problems of Traveling by Air

There is much worrying and discussion about air travel. The experienced problems are presently mostly related to terrorist threats and the delays/annoyances caused by the seemingly necessary security control. The argumentation in these seemingly endless discussions rarely try to come to the roots of the problem, but we will go for the roots now.

The experienced problems with the common passenger airplanes are due to:

In addition to the problems experienced by the passengers, there is the important problem of sustainability, pertaining mainly to CO2 emission and other pollutions. The proposed airship design will strongly decrease these emissions – particularly when using solar powered operation. Big airships may be regarded as opportunities for being able to employ big and powerful solar energy collectors.

These environmental issues are certainly very important, but there is widespread awareness and rational thinking about atmospheric emissions, so we will now mainly deal with aviation aspects for which illusions are prevalent: Does our craving for speed and power give us real speed? Or does it just give us hassles, time waste and dangers?

High speed airplanes don't save us much time, as much time is wasted on security control, technical problems, and on getting to and from those awkward airports. This is due to the fact that this technology implies a balancing on the edge. Many technical factors are critical: The integrity of the (explosion sensitive) airplane body, the air traffic control (of planes unable to slow down), the integrity of landing wheels and the surface they must roll on (so rapidly), the highly trained personnel (able to operate at the technical edge), and so on.

In contrast to this, we have the airship, lifted by gas buoyancy. It is less explosion sensitive than a plane, and can glide to and hover near a city center. We have now a race between the tortoise and the hare, where the hare, as we know too well, has a hazardous labyrinth to deal with.

It may be difficult for space age minds to think rationally about airships, but various suggestions for improvement will now be presented.

Huge investments and infrastructure changes will be needed for replacing the planes, but we needn't worry about that. Our alternative can start out as a funny cruise alternative, and then gradually, due to its flexibility and simplicity, transform itself from a recreational toy into a serious transport tool.

The main features of the following design are the abilities to:





Part II:

A Multi-mode Airship

Airships differ strongly in steerability: from the simple balloon which just drifts with the wind, to the more or less rigid dirigible which can be controlled in defiance of the wind. The multi-mode airship to be proposed here is adjustable in this respect: It can hover or cruise slowly, safely and quietly, and it can transform itself into a more compact and rigid ship, less influenced by the wind and capable of higher speeds.



The Design

This airship is essentially a paraglider with three balloons attached under its canopy. Hanging under it is a payload-carrying frame. This frame can hold one or more passenger cabins. Various kinds of modules can be attached in the payload frame. There will normally be a cockpit module fore and a battery module aft. The modules should be able to slide along the frame – for load balancing and pitch neutralization.


Airship, fully opened.
The canopy will normally be more closed fore and aft – perhaps down to the center of each balloon.
The top propellers are protected against the cable by the M-shaped cable catcher.



A passenger cabin is ready to be attached into the payload frame, between the cockpit and the battery module



The propellers are here positioned for hovering (or for pressing a too light airship down towards the ground)

Each end of the long payload frame has a propulsion unit with propellers in its ends, driven by electrical motors located in the middle of the freely rotatable propulsion unit body. The canopy may be covered with flexible solar cells (polymer or nanocrystal), connected to charge the battery module.

The straps under which the payload frame is hanging, can be wound up on reels inside the long side tubes of the frame, so that the airship can transform itself between being a paraglider/parachute (with the straps fully unwound) and a quite rigid airship, capable of higher speeds and less wind-sensitivity (with the straps tightened).

The fore and aft straps are ropes running through the fore and aft edges of the paraglider screen. If these ropes are tightened while in paraglider mode, the screen becomes like a parachute, decreasing the forward movement of the airship. If they are tightened while in rigid mode (with closed canopy) the airship gets a more aerodynamic shape.

Two (or all three) of the balloons should be filled with helium. This may give enough buoyancy for take-off when only the cockpit module is used, but when a passenger cabin is attached, the motors on the payload frame are needed for take-off. We are consequently talking about a hybrid airship. These are easier to control during windy take-off and landing than a pure (fully balloon-lifted) airship, and the payload needn't constantly be balanced against the gas buoyancy. A solid ground contact can be ensured if the motors are reversed, so that they push the payload down towards the ground.

The middle balloon might be filled with a combustible gas like methane – or perhaps hydrogen. This balloon will then serve as a fuel tank for the motor mounted on top of the airship. Methane has half the buoyancy of helium, but is more easily obtainable. Natural gas is essentially methane, but with also a little ethane and other heavier gases, so this will be cheap and practical.

The lightness of these fuel gases means the fuel will contribute to lifting rather than having to be wasted on lifting itself. Their rather low buoyancy has the advantage that the weight and buoyancy of the airship don't change much as the fuel is consumed. If a still more stable buoyancy is needed, ethane can be used as fuel. It is about 3 % heavier than air, so when ethane in the middle balloon has been burned up, the buoyancy of the airship has changed only 1 %.



Mode Shifting

When the airship is fully opened, it functions as a motorized paraglider. The balloons will keep the canopy raised, and the top motor will keep the ship up against the wind. This may be the preferred operating mode during slow cruising, at least when the wind is moderate. When higher speeds are needed, the airship can tighten its straps to become more rigid and aerodynamic. This tension will also press the fuel gas out to the top motor. The airship can also take off and land in the closed mode. This will be most practical if the wind is strong. Tight closing can also reduce the balloon volume somewhat – for buoyancy control.

The open mode will be good for emergency situations: Whenever the airship experiences a problem with staying airborne, it just loosens its straps to descend slowly like a parachute or (with also the fore and aft straps loosened) glide like a paraglider.


Airships – open and closed.
The rightmost one has also emptied its middle (fuel gas) balloon.

An additional possible mode is: hot air balloon mode – if the airship is equipped with a simple balloon for hot air. This can be stored in a box (with a burner and its fuel tank) lying upon the middle part of the payload frame. When it is to be inflated, hot air is first blown into it by a blower. When the hot air is able to hold up the top of the balloon, a simple fuel burner suffices for completing the inflation process and for keeping the airship airborne. As the fully opened airship already defines the volume to be occupied by the hot air balloon, this balloon can be a very simple one which merely expands to fill the volume between the straps and under the gas balloons (which should be elastic, or have a low initial pressure, to allow for some additional expansion caused by the heat from below). One or more horizontal straps between the two fore straps, and similarly between the two aft straps, may be used for giving fore and aft containment to the hot air balloon.



Propulsion and Steering

The airship has two different propulsion systems:

Biefelt-Brown effect propulsion may be feasible by applying high voltages to parts of the canopy.



Modularity

The balloons of an airship must be designed to:

Placing simple balloons under a paraglider canopy assigns these two tasks to two easily separable module types. Balloons are easily damaged and worn out, e.g. by chemical influences compromising the gas tightness of the light fabric, or by e.g. bullet holes. It is then advantageous to be able to exchange simple balloon modules which need little of the complex force distribution structures, and to be able to do this without performing complex surgery in a closed airship body. Some sort of Velcro-like patches may be enough for keeping the balloons in place under the paraglider.



Energy Storage

The simplest way to store electrical energy is to use a battery pack, which should be mounted as a module aft in the payload frame. Lithium-ion batteries have very high energy density, but are very expensive. Molten salt batteries (like Zebra batteries) gives almost the same energy density at a lower cost, but these batteries must be heated to about 300° C. This should not be a problem in a professional and planned operation. The battery heating may be done while lithium-ion batteries are used for the first part of the flight.

Another alternative is to store energy in flywheels. They are normally designed to be compact, but a large carbon-fiber flywheel (connected to a motor-generator) could be suspended inside a balloon, where it would be well shielded against disturbances.

Flywheels normally operate in a vacuum in order to minimize air drag losses. It might be practical to have a lightweight vacuum sphere in this well protected environment. But if the flywheel runs in helium, the drag will be far weaker than in air. And if the helium is heated by lost flywheel energy, it will become still lighter (provided its balloon can expand somewhat), so the energy isn't really lost.



Mooring

Mooring has traditionally been an awkward and labor demanding part of airship operation, but in airship harbors having horizontal mooring cables, mooring should be possible without any help from the ground. This operation would be more reliable if the mooring place has windscreens, such as vertical sails a little larger than an airship.

The straight top is an important feature of the airship which is prepared for easy and secure mooring, as this can align with a horizontal mooring cable. Another important feature is having freely rotating (electric) propulsion units on the ends of the payload frame. The top propellers may be used for pulling the ship up against the wind. If there is significant wind, it will be advantageous to have a mooring cable going along the wind direction.

The mooring cable above the airship will protect the ship against lightning in the critical phase when the ship is about to get ground contact. It will also discharge static electrical charges in a controlled manner. This is important if the ship uses inflammable gases.

The mooring operation is as follows:

If the payload frame now moves in under a tongue-shaped roof, this roof will act as a firewall which increases the safety when inflammable gases are used in balloons. (Gas flames go upwards, but burning balloon parts fall down.)

The near end of the mooring cable is then lowered until the cabins sit on the platform. The side edges of the roof will be near the straps under which the payload frame hangs, so these side edges should be able to hold the straps firmly – to keep the cabins in moored position.

(A simple but crude mooring method would be to let the airship move forwards/downwards into the space between two fences. Such a fence can be a wind screen or a cable fence with at least one horizontal cable. But both fences must be able to yield rapidly if the ship is blown forcefully to the side before it is properly between the fences.)

During take-off, the sequence of cable grabbing events is reversed: First the cable leads the ship outwards, and then the aft cable grabber goes forwards and loosens its grip, so that the ship turns against the wind and can fly away in a well-controlled manner.

As airships need no runways, the airports can be so compact that they can be near a city center. For a coastal city, airships could approach along cables running from a tower out in the sea. The entire airport could be on a platform or a float outside the coast. The airport and the approach cable could also be shielded between tall buildings, small mountains, or wind screens.



Operation

The multi-mode airship can start with simple balloon flight operation – with passengers who just want to go up and look around. An extra balcony module in the payload frame (or upon the roof of the cabin) will now be valuable.

The electric propulsion of the payload frame motors will now prove important: Conventional noisy motors will destroy the whole soaring experience.

The next operation will be cruises to (and at) specific destinations – when steerability is found reliable, and a destination service infrastructure is established. Only simple mooring facilities will be needed by the airship itself, in addition to gas delivery and a power grid connection for recharging the batteries.

If this operation is found reliable, regular passenger transport can commence. This will compete with trains and conventional airplanes. A suitable operation area will be: across the North sea, across the Baltic sea, and similar areas unsuitable for trains. The competitor will now be the airplane. The airship will be more like a train with respect to bomb sensitivity – particularly if separate luggage modules are mounted in the payload frame. Much security control time can then be saved, particularly if passengers can remain seated in cabins transported by a beamway from and to city centers.

The airship can give the passengers more space (in lightweight cabins) than planes can, so it can have decent sleeping quarters. This means the airship may be preferred for quite long night flights.

Sustainable tourism implies changing attitude towards travelling. The prevalent businesslike practice of jumping to a remote place should be discarded, and be replaced by accepting that travelling implies being on the way. Travellers from northern Europe should find it natural that if they intend to visit south Asia, they will start and end the vacation with spending at least one day in the Mediterranean area.

Operation economy should be ensured when polluting and CO2-emitting aviation is appropriately taxed.



Long Distances

An airship could join an air train for long-distance flights. The locomotive would be a turboprop plane flying non-stop between e.g. England and the US east coast. It reels out aft a carbon cable, 1-2 kilometers long, to which airships can attach themselves when the air loc slows down to perhaps 100 km/h over England. After an airship has grabbed the cable, it can move forwards towards the preceding one, so such a train could get a moderate air resistance. The train will then increase the speed to perhaps 6-700 km/h, suitable for an overnight journey with berths/sleeperettes. In the New York area, the airships will detach in the reversed order, and some of them may continue to Boston or Washington DC. Other airships will then attach for the eastbound flight – or for going to the west coast. Daytime long-distance flights may be more suitable for cargo. Before an airship joins the train, it may visit a transit platform where passengers may go over to the airship for the right destination. Personnel who do on board custom/passport/security controls may be exchanged there. They can get decent space for their work on an airship. Such operations will be quite simple with airships, as they have VTOL capability.


Two airships (solar cell covered) have attached themselves to the cable of an air train.
The rightmost one has now pulled its rear cable grabber all the way back, so it is fully stabilized.

The first airship attaching will probably be for fueling and crew exchange. The air loc flight will probably become quite computer controlled. Air locs with abundant energy can easily give some of it to the airships. The cable could transmit electric power both ways, but the simplest way to get power from the air loc would be to simply use the electric propulsion motors as generators and their propellers as windmills. If the airships have much energy (in sunlight), they can contribute to the propulsion by running their propulsion frame propellers.

The air loc should be able to fly at 100-700 km/h, so a variable wing may be required. A small drone with stabilizing fins or wings should be attached to the other end of the cable. It will have a variable pitch propeller, and this should have three operating modes:

The air loc could be pulling a shield which can be opened and closed like a flower. It is closed like a bud for take-off and landing. For normal flight, it is opened to be a shield in front of the first airship – to relieve it of the speed wind pressure.

An alternative to the air train is the air caravan: An airship goes in the front, equipped with a reinforced front plate, and it carries the cable assembly instead of a passenger cabin. The caravan will be mainly for daytime operation, as all the airships must use their propulsion systems.



Biefelt-Brown Propulsion

Such long trains are well suited for electric field propulsion based on the Biefelt-Brown effect. This could be done in two ways:

The air loc with the positive electrode should be at least 100 meters ahead of the first airship, or the first airship in a caravan should have a positively charged shield. (Intermediate airships may be given intermediate voltages, but in the non-linear manner required for the Biefelt-Brown effect: strongest gradient behind at the negative pole.) Either of these two would enable the train, with its field and ionized air, to behave as a large streamlined entity which would protect each airship against the strong speed wind. (This design sketch doesn't take side in the electrogravity vs. ion wind schism.)



Safety and Security

The airship will hopefully be as explosion resistant as a train or beamway, so that it will not be more interesting for terrorists than any other meeting place – particularly if luggage is placed in a separate container module. This will reduce the security control delays to a minimum. Customs and passport control could be done on the airship, as this will be roomier than a plane, and may even have a separate office module for such controls. Undesired passengers/luggage can be removed during a transit platform visit.

A balloon will be easy (and tempting) to shoot a hole through, but it may be designed to be made self-repairing: The inside of its fabric could be covered with a low-density sticky plastic foam which will be caused to form a patch by out-streaming gases in a hole. If one of the three balloons is destroyed, the VTOL propulsion units may be able to give a not too hard landing – and/or the airship will open up to go into parachute or paraglider mode.

It may be feasible to make carbon fiber armored balloons bullet-proof, because the fabric needn't be very strong. This is because of its unique ability to yield rapidly to a sudden local impact, as a light gas behind the fabric will only weakly resist the sudden acceleration.

The use of fuel gas is likely to be restricted to cargo flights, but it might be found usable for passenger flights: A fire in a fuel gas balloon will occur some distance above passenger cabin – particularly when the airship is in an open mode. The strength of the canopy should be based on carbon fibers, which are able to withstand high temperatures, so the airship may still be able to function in parachute or paraglider mode during and after a gas fire. If not, cabins should bail out in their own parachutes. Cabins should be designed to stay afloat if they land in the sea, either by having thick and light floor and lower walls, or by having self-inflating floaters.

In contrast to the conventional all in one airship design, the present design separates the passengers from the balloons, so that both sabotage and cargo explosion damage will be a smaller threat to the ship.

An airship should be boardable from anti-terrorist helicopters, and is not easily crashed, so it would not be suitable for hijacking.

VTOL operation is normally a precarious balancing act, but will be a simple and safe operation for an airship, which will always be kept upright by its balloons.



Police Operations

Helicopters are useful for various police operations, but due to their complexity and risky operations, only the large police departments in metropolitan areas can have helicopters. This was demonstrated during the terrorist attack in Norway on July 22. 2011. The police in Oslo had a helicopter, but no staff able to use it due to the summer vacation. Criminals will of cause notice this and strike in the periods of weakness. The solution will be to use airships instead of helicopters, because airships can be running in passenger transport, particularly across the sea stretches of northern and southern Europe. Through a cooperation between the police and airship companies, an airship can be requested for police action while the special police unit is preparing for action.

Shooting down a helium-filled airship is a slow process, and may be really difficult to do with light weapons from the ground if the airship fires guided missiles from a high altitude.

An airship is an asymmetrical weapon, as it is impractical to have and to use airships for crimes, e.g. as a getaway vehicle, even if the criminals intend to switch to a car.



Needed during Volcanic Activity

During the eruption of the Icelandic volcano Eyjafjallajökull in the spring of 2010, the air traffic over most of western Europe was halted for days – because the jet motors of the planes couldn't deal with the airborne ashes.

The airship's electric motors will be able to withstand large amounts of such particles. Besides, the “raincoat” of this ship will give protection against quite warm and heavy particle falls.

This may seem rather unimportant now, but when the supervolcano under Yellowstone explodes (– any year now), much heavier ash falls will persist worldwide for years, and such alternative air transport will really be needed.



Buoyancy Calculations

The balloons shown in the illustrations have the following volumes:

Total volume: 60 000 m3. If the middle balloon is filled with a fuel gas, total volume is reduced to 39 300 m3 when 90 % of this gas (20 700 m3) has been burnt up.


Gas
Property \

Air

Hydrogen
H2

Helium
He

Methane
CH4

Natural gas

Ethane
C2H6

Molecular weight (average)

29

2

4

16

17-18

30

Buoyancy (mol. weight)

0

27

25

13

11-12

-1

Buoyancy, kg/m3

0

1.205

1.116

.580

.5

-.045

Buoyancy in tons*
for 60 000 m3
for 39 300 m3



69
44


67


54.6
42.6


53
42.4


40.3
41.2

Combustion energy
for 1 m3


25.5 MJ


36 MJ

39 MJ

70 MJ

Combustion energy
for 20 700 m3


528 GJ
147 MWh


740 GJ
206 MWh

807 GJ
224 MWh

1448 GJ
402 MWh

*: with helium in the side balloons, which will then contribute with lifting 41.3 tons

Energy data source: Wikipedia articles for the gases, plus this Wikipedia article.


If maximum buoyancy is needed (and safety is less important, or helium is not available), hydrogen is used in all three balloons. Buoyancy: 72.3 tons.

If the buoyancy should be kept unchanged while fuel gas is burned, a mix of 7 % methane and 93 % ethane could be used. Buoyancy: 41.3 tons.


Olav Næss, November 2007 - August 2011