More About Kothmann

More About Kothmann

Lifting Gas Bags

The Construction of the large gas bag is simplified by using two separate envelopes rather than a conglomerate of laminations. The helium containing Inner envelope uses established "thin film" technology and reinforced seaming methods providing a lightweight bag. Certain manufactured thin films are able to contain the small molecular gasses (helium) at relatively high pressures with insignificant loss. This thin film gas bag is arranged inside of a very strong outer fabric hull, which can contain the relatively high tensile forces developed by the pressure variances within the lifting gas envelope. Also inside the fabric hull is the traditional diaphragm more commonly called a ballonet which can be purged with air to create the pressures required for variable displacement.

A recently developed fiber reinforced material is incorporated in the outer fabric envelope of the airship and will contain the inner thin film gasbag in a fixed volume. The outer component of the envelope will absorb the pressures required to attain displacement variance and controlled vertical flight while maintaining a rigid shape even under partial inflation by lifting gas.

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Lift Control Systems

The aircraft's primary vertical flight control system is provided by the inflatable air bag, but the diaphragm is not necessarily located within the gas bag and can be placed between the gas bag and the platform created at the level of the Tension Ring. The separation of the air bag and the gas bag will facilitate simple maintenance and replacement of either bag. Automatically controlled portal dampers will direct the intake and discharge of air ballast as it generated by electric turbine fans which are located on the equipment deck. Therefore, thrust from the engines is not required for charging the diaphragm with ambient air. The turbine ram air fans allow precision altitude control without the need for acceleration or while hovering on station.

Secondary vertical flight control is provided by a lifting-gas (helium) management and conservation system. Lifting gas can be compressed and stored into the Compression ring by a compressor located on the equipment deck above the crew compartment. The compressor will compress the lifting gas. The compression ring not only acts in structural compression, it is also the compressed gas receiver. By compressing the lifting gas into the compression ring together with simultaneously pressurizing in the diaphragm air bag, allows vertical flight control over a wide range of temperatures and altitudes and also compensates for the cargo and passengers which can then be safely off-loaded. The aircraft can, therefore, land and take off anywhere that space and the Law will allow.

The Kothmann's simplified construction becomes rigid by its own weight. All load forces are transferred to the Compression Ring and "halo" accumulator that gives the airship its distinctive lenticular shape. The greater the force on the fabric, the greater the force on the compression ring, however, the interior lifting gasbag will not experience surface stress (tension) along any seam or surface. The shape becomes rigid-by-gravity when the air ship is even partially inflated with lifting gas and does not need higher than ambient pressure to become rigid and will operate normally at less than optimal lifting gas volume. When the aircraft is inflated with the lifting gas, the structural fabric hull will evenly transfer both, the lifting gas forces as well as the dead load and payload forces of the aircraft to the compression ring in a similar manner as spokes on a bicycle wheel. Traditional Airships experience a "dimpling" if the lifting gas pressure is less than ambient while underway, unless the Nose is heavily reinforced in order to hold the cone shape. The outer structural envelope or hull of the Kothmann is a fixed volume and determines the maximum expansion limits of the thin film lifting-gas bag and also the shape of the aircraft, and if the volume will not fluctuate due to an increase in pressure, then atmospheric displacement is controlled.


Pressures due to temperature variances will not affect the capability of the Kothmann airship, which will maintain level altitude flight throughout the daily temperature cycles, via the lifting gas management systems. As we all know, the volume of the lifting gas will increase in direct proportion to the temperature. The Kothmann airship can control these volume changes by either controlling the air ballast and/or by storing or discharging lifting gas from the compression ring.

Although the weight of the compression ring pipe is of major concern to any Airship designer, it is not only essential to the shape, its value as a receiver for the lifting gas more than offsets the loss of lift due to its weight. The lifting gas control system will allow the crew to preset the equipment to automatically maintain a desired pressure in the lifting gas envelope in addition to, allowing the pilot to compress enough lifting gas into the storage compression ring for long term parking. The gas receiver compression ring will also "dry" the lifting gas and will be equipped with auto blow down valves to discharge condensate water, which becomes accumulated through the compression cycles.

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Optional Lift Control System

A third or Tertiary means of displacement is designed but not yet implemented. this system will be forthcomming at a later date.

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Hold Down System

One of the most important features of the Kothmann is the ability to "stick", like a suction cup, to any relatively smooth paved surface. Immediate off loading of passengers and cargo is facilitated by sticking the airship to any paved surface similar to the way a suction cup or child's play dart will stick to smooth surfaces. The bottom of the crew compartment is designed so that a small amount of space exists between the ground and the crew compartment floor deck. When the aircraft lightly touches a hard surface, the pilot engages the electric suction fan which will evacuate the small volume of air that is captured between the ground and the 12 foot diameter crew compartment floor, allowing the suction fan to create a negative pressure compartment.

A flange gasket around the bottom the airship seals the evacuated space to the surface. This immediate suction will create a minimum hold down pressure of over 8,000 pounds with a turbine fan that weighs only 24 pounds and can evacuate to pressures up to 40" of water column. The fan can be powered by both the primary electrical system and the auxiliary generator. The Kothmann aircraft can land, refuel, off load and reload cargo, and then take off by releasing the evacuated air space

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Propulsion is provided by any conventional motor-driven propeller located in the rigid duct. This rigid framed tube also is a key structural element of the aircraft. Propulsion can also be provided by any conventional engine either water cooled or air cooled. I have chosen to employ an all aluminum water cooled engine producing approximately 400HP. My choice for the power plant was mostly governed by cost and a desire to maximize the horse power to cost ratio. Optimum horsepower of the airship that is currently under construction is approximately 800 HP in a two engine "in-line" configuration.

The skin of the fan duct is constructed of perforated surface which is acoustically tuned to reduce prop and engine noise. The fan duct will act like a large muffler reducing prop noise and the Kothmann will be virtually silent under full power. The ruder and lifting planes are located in the rear of the fan duct. An Important feature is that the location of the equipment and engine(s) allows maintenance and repair while in flight.

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Control Systems

Controlled flight for the aircraft is achieved by locating conventional control surfaces at the outlet of the propulsion duct. Horizontal flight control is provided by the rudder, vertical flight control is provided by a plurality of lifting-planes. The rudder will rotate the craft in either horizontal direction for 360 degrees. The control surfaces are simple and mimic historic low speed aircraft designs where the thrust of the propulsion engines has direct influence. Unlike traditional airships that must have airspeed in order for the control surfaces to have an influence.

The primary vertical flight control surface is the rear horizontal lifting-plane. The Kothmann will tend to pitch up as airspeed increases which can be utilized to quickly attain altitude. The rear horizontal control surface is designed to counter act the natural aerodynamic lift along the leading edge of the shape. This control surface is designed to allow the pilot to preset the angle of Incident based on the airspeed of the airship which compensates for the anticipated undesirable lift. The primary horizontal control surface will provide overall pitch control.

The Kothmann can reverse direction in flight with minimal influence from the rudder. Once the airship is set in rotation around the vertical axis it will continue to rotate until an opposite rudder is applied.

The amalgamation of the control surfaces will also yield a distinct maneuver when the ship abruptly cuts thrust after attaining airspeed. The bow will immediately turn up inducing the ship to act similar to a drag chute and the ship will come to a slow airspeed instantly as it gently returns to the pendulum position. The pilot can therefore approach a landing site at full throttle and still land on a dime.

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The Air Frame

The rigid component of the airship is a 2 level design with the crew compartment under the equipment deck. The crew compartment is spacious featuring surrounding windows for a 360 degree view. The equipment deck above contains the propulsion engine as well as all the other equipment such as turbine fans and auxiliary generators as desired, The perimeter of the equipment deck is formed by a radial trusses defining the deck enclosure. Angular structural members are attached to the radial truss to form the 50' diameter of the diaphragm deck.

The Airship is simple to assemble in the field from a minimum of 6 pre-manufactured assemblies including the lifting gas source. These are; (1) the fabric hull, (2) the lifting gas bag, (3) the air diaphragm bag, (4) the radial triangular frames, and (5) the rigid frame assembly comprising of the crew compartment, and (6) the equipment deck, the radial truss, and the propulsion tube. The last frame assembly also includes the propulsion unit and all other equipment such as the generator, fuel tanks, pumps, fans and controls. The airship can be field assembled and deployed by a small crew in approximately 40 man hours, or it can be disassembled and transported to remote locations.

The outer perimeter of the "diaphragm" deck is formed by a tension ring, to which the load tapes of the outer hull structural fabric are connected. This deck supports the downward forces created by the pressure variance within the lifting gas envelope and also serves to structurally stiffen the frame. Angular structural members radiate outward from the radial truss which act in compression to support the dead load of the aircraft in the parked (heavier than air) condition, and act in tension when the craft is lighter than air.

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Stacking for Heavy Lift

The Heavy Lift capability is accomplished by linking as many airships as necessary. Each airship contributes its maximum lift potential. The 120 foot version will contribute in excess of 9,000 pounds per airship. Larger Airship amalgamations are feasible.

The Lower airship does not experience any more stress on the frame than the top airship. The cumulative lifting force is transferred to the center cable and each airship is simply adding a portion of the lift. Forward motion and speed is multiplied by the power of each airship that is attached in the chain. While linking or delivering, the Train is maintained vertical, even in gusty wind.

Linking an Airship "Train" is a relatively simple maneuver for even inexperienced pilots. A hatch in the crew compartment floor allows direct physical and visual contact with the attachment device of another airship. The airships need not detach from each other in order to deliver a payload and can simply return to the loading zone, still assembled, for anther load. No additional ballast such as water is needed for the Heavy Lift Train to accomplish the mission. Each airship can "pressure up" to decrease atmospheric displacement so that when the payload touches earth, detachment is immediate and the assembly may proceed to another load or disperse independently.

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