When I attended this conference two years ago

a lot of presenters talked about how

airships could be a more efficient alternative to many air transport applications where airplanes

are used for at the moment.

But I didn't see anybody present any calculations.

And then when I went to the Airship Association's international conference last year

there

was a presenter who claimed that his relatively small airship design would emit two and a

half times less carbon on a per passenger kilometer basis than an aeroplane.

And that seemed unlikely to me.

And so I thought it is time that somebody shows some numbers and shows their work.

So that's why I'm standing here now.

So I'd like to very briefly give a review of the prior work on this topic.

So interest in performance comparisons of the airship and the aeroplane sort of occurred

in three phases.

And the first one was in the 1920s.

And this was spurred by the R34's successful Atlantic crossing from Scotland to New York

carrying 31 passengers

two pigeons

and one kitten.

And that sort of triggered a debate of whether the airship or the aeroplane would in the

future be used for transatlantic travel.

And the aeronautical scholars of the time overwhelmingly supported the airship.

And some of them were particularly confident with their predictions, as you can see from

this quote.

The second phase occurred in the 1970s

and this was fueled by the oil crisis

which caused

people to investigate more efficient forms of transportation

including the airship potentially.

And there was one author in particular who derived an expression for the drag to weight

ratio of an airship, which is proportional to the square of the speed of the airship

and anti-proportional to its length.

So if we want to have a very efficient airship

it needs to go slowly and it needs to be very large.

And then more recently

climate change has caused a resurgence of interest in airships.

And there's one reference in particular I'd like to mention, which is this book, Sustainable

Energy Without the Hot Air, by the late Professor David McKay.

And this is one of my favorite books

and I can unreservedly recommend it to you.

In this book

there's an expression for the energy used by an airship per unit distance

as a function of the propulsion system efficiency eta

the frontal area reference drag coefficient

CD

the speed again

and the length.

And McKay then substitutes numbers in this equation

and he arrives at the assay number