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Non-Rigid RIBB Airship

The Safest, Simplest, Most affordable Lenticular (Airfoil shaped) architecture for Payloads up to 60 Metric Tons.

For smaller Airships with payloads up to 60MT, it doesn't make economic sense to design and manufacture Rigid-Architecture vessels. Their Lift/weight efficiency ratio are simply too low to take that design direction notwithstanding their poor performances in Robustness and Resilience.

As stated previously, a Non-Rigid architecture makes for a much cheaper project to design, to fabricate and to assemble requiring less resources (human, material, logistics, time & $) because in the end, the ship is much lighter and smaller and contains orders of magnitude less components.

Conventional Non-Rigid Airships are often composed of a single Ovoid-shaped Gas Cell as we have seen on a previous page. This form factor is paramount to keep both the circular sectional-shape and the longitudinal structural beam in equilibrium. 

On the minus side, it is more difficult to provide Gas-escape redundancy on a Non-Rigid Airship because of their inherent lack of compartmentalization capabilities. Each Gas Cell must contain a Ballonet and so segregating its entire Ovoid cavity into separate Cells would multiply its level of complexity. 

In addition, a single Ovoid Cell imposes great difficulties if we want to flatten it into a non-cylindrical Form factor and makes it even more difficult if you elongate the ship' span over its beam. All this can only be accomplished by designing multiple longitudinal Lobes using Catenary Curtains as dividers such as found on the Hybrids from Lockheed (Now AT2) and Airlander. You end up with deep creases where lobes meet which is beneficial in the case of Hybrid Airships that must produce aerodynamic lift.

ATHENA's RIBB design is a novel architecture for Aerostatic Non-Rigid Airships of Lenticular shape. This particular term might not be broadly used in the broader airship community but a quick web research will provide you with a slew of documentation and past, ongoing and envisioned projects. We were first introduced to this concept while working with Stelia on the defunct US-Canadian LTAA project in 2015-17. While we were responsible for the Structural architecture of the Airship, we finally came to the conclusion that the initial Semi-Rigid Architecture designed around an equatorial Lattice-Beam Ring was both inefficient and too costly.

Through exhaustive calculations and analysis, the RIBB Concept came to fruition solving all weight, cost and safety issues found on all other candidates.

The Idea was quite simple and elegant... replace the metal equatorial structure by a Toroidal Gas Cell that would provide Strength, Stiffness, Shape retention while eliminating mass and providing additional Lift.

Thanks to Catia V5 and ATHENA's parametric Airfoil modeling capabilities, the equatorial Gas RIBB could be modelled to follow any Longitudinal Airfoil Profile by constantly varying its cross-section over the entire contour of the Airship. And, since our Airfoil models are always linked directly to our Airfoil database, any RIBB Airship can take an infinite array of Airfoil Profiles.

Custom Aero Profile per LTAA Specs

Even though our Equatorial RIBB is Form-Stable in itself, it would pinch in the middle if any central load was to be equally supported from both of its halves. A central Cell therefore needs to be inserted in its central cavity.

Central Gas Cell

This Central Cell brings the added benefit of becoming locked into the Equatorial Cell's central cavity once the later is filled. It provides a smooth transversal aero profile unhindered by large creases that would hinder the de-icing and snow evacuation during winter operations.  This Larger Cell can be divided into mutually sealed compartments as well.

We need to keep in mind that any pressurized Gas Cell on Non-Rigid or Semi-Rigid Airships need to have its internal pressure balanced as the Ship travels up-and-down through varying atmospheric pressures. Ballonets thus need to be included in the build coupled with air pumps or Tensors to vary their internal volume. The more compartments we have, the more Air pumps we need but... the easier it gets to size them up to allow for the required airflow rate.

​Tensors in comparison don't care about rate... 

Suspended RIBB Ballonets
Central Cell Ballonets

To increase safety an additional notch... it's never too much!... our RIBB concept added Top & Bottom Fabric Covers to refrain the Central Cell from ever escaping the Equatorial Cell as well as to provide a separate Cargo attachment decoupled from the Gas Cell itself. As a bonus, It opened up an elegant mean of attaching bulky outer components as well.

Equatorial Cavity 

If you cut a transverse section anywhere around the ship's periphery, you will find a void, a cavity that runs all around the top and bottom where the Upper & Lower Covers tie up to the Equatorial Gas Cell. This cavity allows the possibility to wedge large pedestals to mount heavy (relatively) systems such as Fins and Pylons without requiring heavy and complex structures. It provides as well a continuous conduit to route EWIS and ECS ducts.

ATHENA's Aero RIBB Non-Rigid AirShip

For all types of Lenticular (Aero Shaped) Non-rigid Airships, such RIBB design as shown below allows the possibility of using an infinite array of aerodynamic profiles.

Equatorial RIBB

Shown above is the ensuing stable Gas filled Equatorial RIBB that can be further compartmentalized into Halves, Quadrants or Sectors.

Such type of Ballonets is very well suited to Single-Arm Tensors and would differ from the one shown above by having its curtain extend all the way to the Cell's bottom.

Equatorial RIBB Quadrants Ballonets
Total Gas Cells Architecture
Propeller Pylon mounting with bonded Lanyards

As you can appreciate, there are ways to make Non-Rigid Airships take a wealth of complex shapes without hindering there form stability, their simplicity over Rigid Ships and their safety. Yes you can have Longitudinal Multi-Lobes Ships such as we find with the AT2 and Airlander Hybrids where large creases provide Airflow corridors to increase aerodynamic Lift retention but these same creases hempen the evacuation of heavy ice and snow buildup on normal aerostatic Airships. With a bit of imagination and engineering rigor, we are making the demonstration here that it is possible to design novel Non-Rigid Airships that can fulfill the promises of safe and robust Lighter-Than-Air transportation.

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