This little blog series is based on a talk I gave on August
18, 2012, at Pi-Con in Enfield, Connecticut. About a dozen people showed up, which was
very gratifying, and I think all of us had a good time.

Airships are the signature technology of steampunk and alternate-history
stories. If you look up in the sky and see an airship (that doesn't say
"GOODYEAR" on the side), you may have slipped into another reality.

Now, I happen to be a fan of steampunk and alternate
histories in general, but I'm also an airship buff. Which means I sometimes get
frantic when stories get them wrong. (Actually I get frantic when stories get
anything wrong. I spend a lot of time being frantic.)

Flying isn't easy, at least for humans. Flying machines have
to do three things. They need lift, they need propulsion, and they need
control. Without lift it's not a flying machine, just a car. Without propulsion
it just sits there, and without control it's an unguided missile.

Lift is the most obvious, and the one which got the most
attention. If nothing is countering the pull of gravity, you're stuck on the
ground. There are two ways to generate lift: thrust and buoyancy. With thrust,
you generate a push down that counters the pull of gravity. Rockets do it by
sheer brute force, but airplanes and helicopters use a more elegant method
based on the Bernoulli Effect, in which forward motion creates a difference in
pressure between the top and bottom of the wing (or rotor), which generates
lift. If you prefer, you can think of this as "suction" rather than
thrust.

The second problem is propulsion. Inventors tried all sorts
of methods: flapping wings, sails, oars, and hand-cranked propellors.
Ultimately the solution had to wait for the development of motors light enough
to go aboard flying machines.

The final problem is control, which turned out to be a lot
harder than anybody realized. Airships were still grappling with control issues
as late as the 1930s, and airplanes simply weren't possible at all until the
Wright Brothers figured out that you can't steer an airplane the way you steer
a boat.

Buoyant flight came first. The Montgolfier Brothers managed
it in 1783 by taking advantage of the difference in density between hot and
cold air to create the hot-air balloon. The discovery of lighter-than-air gases
like hydrogen, methane, and helium led to the "gas balloons" which
were the dominant form of flying machine during the 19th century.

Balloons have been unjustly neglected in steampunk. They
were the apex of aerospace technology for nearly a century. Even as late as
1895, when H.G. Wells was writing The Time Machine, he used the balloon as an
example of a machine which could travel in three dimensions.

Balloons solved the lift problem, but they ignored both
propulsion and control. If you go up in a balloon, you're going wherever the
wind decides to take you. You can land if it turns out you're going the wrong
way, but that's about your only recourse.

This limited the applications of balloons. They couldn't
carry passengers because nobody wanted to buy a ticket to travel in a random
direction. Their military applications were important: tethered observation
balloons became a key technology. It's worth remembering that some of the first
fighter planes in World War I were deployed as "balloon busters" to
shoot down enemy observation balloons. Even today unmanned aerostats have a
role in military reconnaissance.

I've always been disappointed by how few steampunk writers
have made use of balloons in fiction. When Jules Verne wrote his first "Voyage
Extraordinare" in 1863, it was Five Weeks in a Balloon, about an aerial
expedition across Africa.

If you want daring action sequences, consider the use of
balloons to carry messages and refugees out of Paris during the Franco-Prussian
War of 1871 — lifting off in the dark of night, flying at the mercy of the
winds over enemy lines with the whole Prussian Army taking pot-shots, and
trying to reach friendly territory before the lifting gas leaks away. That
really happened. Parisians must have felt like they were living in a Verne
novel.

Even today balloons still test the limits of human flight: just two months ago Felix Baumgartner set a world record for parachute jumping, leaping out of a balloon. Steampunk needs more balloons.

Next time: the first powered airships!