Airship Technology Speech

Tuesday, January 27, 2015

A presentation!

My character in our role playing game was ordered to make a public presentation about some of the technological advancements embodied in our Airship. Basically the Government wanted to share these advancements with the Civilian companies as a way to boost the Empire's commercial competitiveness.

Just for fun I decided to actually give the presentation as part of an ongoing series of Absinthe Cafes here in Calgary.

I presented it in character and in costume, and it was a lot of fun.

Lt Cmdr(E) Maxwell MacDonald-Smythe
Photo by Lewis King
The information presented here is based on my Practical Airship Design series.

Here is the text of my speech.

Keep your sightglass full, your firebox trimmed and your water iced.
A January evening in the latter years of the 19th century.

Madame and Mr Chairman, My Lord, Ladies and Gentlemen.
Good evening.

I have been asked, by the Experimental Airship Division of the Royal Navy, also known as the the EAD, to present some of the technical details of one of the marvels of our age!
It is the hope of Her Majesty's Government that by releasing this, hitherto classified, information to the British business and manufacturing community, that the further development of these exotic and ground breaking technologies will help to maintain our Empire's lead in global commercial and military affairs.

Many of you have probably seen or heard the reports concerning the latest experimental airship of Her Majesty's Navy. You may also have seen the speculation concerning many of the developments and mechanisms that she has on board.

I have the honour to have been, and continue to be, her Chief Engineer.

And, Ladies and Gentlemen, as much as I would like to confirm that she is powered by exotic Indian demons and lifted by some remarkable gaseous material never seen before, and even that she can fly in the vast reaches of space, I must assure you that everything we will discuss this evening is in fact the product of the investigations into Natural Philosophy conducted over many years by brilliant men and women just like yourselves.

Nothing of what I will be showing this evening is in the province of the Metaphysical realm.

Having, alas, thus ruined your excitement concerning the information I am about to present to you, I hope that you will find the real information just as intriguing.

And so, to begin…

Here is the object of our discussion this evening.

Her Majesty's Air Ship The Velvet Brush!

She is truly a marvelous vessel, the largest self mobile object ever built by human beings!
Her dimensions are enormous,
  • Her Length is 245 m or 800 ft, longer than the largest ocean liner.
  • The Diameter of her hull is 42 m or 137 ft
  • She contains a Gas Volume of 231,000 cubic meters or 8 million cubic ft
  • She weighs uninflated 150 tons
  • When in flight trim she can carry a cargo load of 28 tonnes
  • Her propulsion system can move her at a steady cruising speed of almost 120 km/hour or  65 knots, thus making her one of the fastest ships in the Airship Navy.
  • Her maximum speed is still classified as is her maximum altitude, however; I can say that she has maintained that 120km/h value at elevations in excess of 1800m or 6,000 ft above sea level on numerous occasions. Her operational pressure height is 1200m or 4,000 ft under normal load conditions.
  • Her maximum cruising range is currently unknown!
I will say that on her very first flight she flew non-stop from the Royal Navy Airdock in Esquimalt British Columbia across the breadth of British North America, and the North Atlantic, to Portsmouth a distance of some 9000 Km or 5500 miles. This trip was accomplished in the dead of winter no less.

Ladies and Gentleman the Velvet Brush is a truly amazing ship, and despite the controversies and scandals attending her construction, she will be a model for future large Aerial Vehicles.

So to the technological developments that allowed the Royal Navy to construct such a stupendous vessel.

There are three developments that I will discuss this evening.

The first is the intellectual development that permitted her to be designed,

The second concerns the key material used in her construction,

And the third is the novel form of her lift generating system.

Many of you I am sure are aware of the advances in mechanical computation that have attended the construction of the Lovelace-Babbage engines in use at Oxford and Cambridge. The Difference Engine, designed by Charles Babbage under contract to the Royal Navy to produce navigational tables, was completed in 1849. Babbage completed the design for his more advanced Analytical Engine but it had not been constructed by the time of his death in 1871.

However his associate Augusta Ada King, Countess of Lovelace, continued working on the design, again under contract to the Royal Navy and the new machine was produced and first began calculations in 1880. Along with the physical design of the machine, the countess was instrumental in composing the grammar for the lists of instructions that the machine uses. Her treatise on "Simulation of mechanical processes by computation", published when she was in her 60s in 1875, earned her a worthy place in the Royal Academy.

One of the first applications of the Lovelace-Babbage machine was the analysis of stress and strength in the metal components of ships hulls. It was also used in the computations to design the first Naval scouting Airships and the first Cunnard Passenger Airships that followed soon thereafter.

The design of such a magnificent vessel as the Velvet Brush would not be possible without the speed of computation, and the elegance of the Countess's Analytical Engine Grammar.

As part of the technology transfer program of her Majesty's Government, two new Lovelace Babbage machines, of the latest design, will be available for public use starting later in the year. One will be in London the other in Liverpool.

Now, as to the construction of the Velvet Brush herself.

The structure of an airship must be both strong and lightweight. Conventional commercial and military airships have been mostly constructed using frames made of laminated wood. And as you are no doubt aware, most commercial vessels still are.

In 1846 Pierre Berthier discovered that aluminum could be extracted from Bauxite ore.

At the time Aluminum was worth more, per oz, than gold!

The commercial development of the Hall-Héroult electrolytic process in 1888 made this metal available cheap enough that it could be used in structures like those used in Airship frames.

Work done at the EAD has resulted in a new metal known as Duralumin, which is an alloy of aluminum with approximately 4% copper, 0.75% magnesium, and 1% manganese. This alloy is as light as aluminum but much stronger. It can be cast, drawn and forged into complex shapes, and when heat treated has many of the qualities of steel.

I have here a sample of Duralumin that you can look at. Duralumin revolutionized the design of large airships and was a closely held military secret as it allowed the Royal Navy Airships to have longer ranges and better performance than our competitors. The older formulas for Duralumin will be available as part of the technology transfer.

The enormous size of the Velvet Brush is only possible because of the strength and light weight of her Duralumin girders and hull structures.

And finally we come to perhaps the most interesting component of this marvel of the age!

The Velvet Brush does not use hydrogen as her lift gas. Instead she uses low pressure steam!

The first manned, lighter than air flight was accomplished by the Montgolfier Brothers in France on November of 1783 in a balloon lifted by heated air. Only a few days later in December 1783, professor Jacques Charles launched his manned hydrogen balloon. Hydrogen being the lightest gas known has been the lift gas of choice for airships ever since.

In addition to hydrogen, other gases have been used, including methane or swamp gas, and water gas, but these gasses do not have the lift capacity of hydrogen. They do however share the major problem of hydrogen and that is they are explosive when mixed with air! They are also poisonous.

Steam of course, is not flammable, and non toxic!

As far as the specific lift of the gas, that is the amount of weight that a unit volume of gas can support at standard temperature and pressure, Steam is about half that of hydrogen, essentially the same as swamp gas.

The specific lift of hydrogen is 11.15 N/m3 or 71 lbf/1000 cu ft.
Steam at the same conditions of temperature and pressure can lift 6.13 N/m3 or 39 lbf/1000 cu ft.

By comparison heated air can only lift 2.98 N/m3 or 18 lbf/1000 cu ft.

Not being flammable is of obvious value for a military airship! But there must be some other benefits to using steam to make up for the 50% reduction in gross lift!

The primary benefit is the ease of control of the buoyancy of the airship.

Airships fly by maintaining a careful balance of weight and lift. In a conventional airship this balance is maintained by the use of ballast, which can be dropped to lighten the ship, and the venting  of lift gas, to allow the vessel to descend. Both of these actions are permanent changes to the airship and since the volumes are limited they are the limiting factor in flight duration, more so than fuel capacity for the engines.

Steam, unique amongst all the other lift gasses, can be produced on board the airship.

However; steam readily condenses to liquid water if the temperature drops below the boiling point.

This is both an advantage and a disadvantage for our airship. While the ship will continuously be loosing lift gas to condensation with time, she can collect the condensation and through the re-application of heat turn it back into steam!

Thus a careful balance between rate of steam production and condensation allows us to adjust the buoyancy as required without venting or dropping ballast.

The volume of an airship increases as the cube of her dimensions which means that vessel twice the linear size will have 8 times the volume!  The rate of condensation however is only proportional to the surface area of the lift bags which increases as the square of the dimensions. This means that the larger the ship the lower the relative rate of condensation. The enormous volume of the Velvet Brush contains the steam equivalent of 144 metric tons of water but only requires a few tons of liquid water to balance the losses in flight.

The heat source used to generate all this steam in the Velvet Brush is still a classified military secret. However; conventional boilers can be used as long as they are very efficient and light weight. This is not as onerous a requirement as might be expected, since the steam is at atmospheric pressure.

Madame and Mr Chairman, My Lord, Ladies and Gentlemen
These are only three of the many technological developments that are embodied in the Her Majesty's Airship the Velvet Brush. It is hoped that by releasing this information to the Empire's design and manufacturing community that we will continue to lead the World in transport capabilities and that, with your assistance, our Naval vessels will maintain the Pax Britannica on the sea and in the air.

Thank you for your patience.

God Save the Queen!

I would be happy to answer a few questions if there is time.


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