I’ve started work on a new book about how rapidly we’re learning to integrate robotics with human beings. It won’t be too long before we have real-life cyborgs. One of the most surprising things I’ve learned in researching the book is the huge role the military plays in developing advanced prosthetics — which might be fitting because they also contribute to there being a need for advanced prosthetics. It’s amazing how World War II changed the way disability was perceived by the general public.
Another area in which the military has played a huge role is the development of air travel. Before we understood aerodynamics, the only options for flying were Lighter-than-Air (LTA) aircraft, which work on the principle of buoyancy: Some things float and others don’t.
Buoyancy: Why Stuff Floats
The principle was discovered by the famous scholar from Syracuse, Archimedes. (That’s Syracuse, Greece, not Syracuse New York.) The King he worked for (in those days, Kings hired philosophers, not PR people) had just gotten a new crown. He was suspicious that the crown-maker had perhaps cheated him and not made the crown from solid gold. He charged Archimedes with figuring out whether the crown was solid gold — except he wouldn’t let Archimedes do anything that might destroy the crown.
Archimedes was perplexed for some time. The story is that he decided to take a bath and when he saw in the tub, water sloshed over the sides and he realizes that the buoyant force of a submerged object was equal to the weight of the fluid it displaced. He was so excited that he ran naked down the streets of Syracuse shouting Eureka!
What exactly does that mean?
If you put your rubber duckie in the bath, part of it is submerged and part of it is above water. Gravity tries to pull the duck down and the buoyant force of the water pushes the duck back up. When the two are equal, the object floats.
The cool thing about this principle is that it doesn’t just work for water. Remember that every time we talk about aerodynamics, I remind you that air and water are both fluids and they behave very similarly. So the exact same principle that floats your rubber duckie is responsible for hot-air balloons and blimps.
You and I are dense. Physically, that is. The average density of a human being is 1.062 g/cm3, which means that if you took one cubic centimeter of yourself and weighed it, it would weight 1.062 g. (In British units, that’s about 66.3 lbs for every cubic foot of person). Just to give you an idea of the relative densities of other things, here are a couple representative substances.
People are mostly water, so it’s not surprising that we’re close in density to water. Our bones help make us a little denser, though. There is a wide variation in human densities, which includes things like the fact that men generally have a lower percentage of body fat than women.
So it is a scientific fact that men tend to be denser than women.
Since people are more dense than water, they should sink in water. But you can actually change your density a fair bit by doing something as simple as taking a big breath and holding it. Now you have air in your lungs. That air is much less dense than your body, so it decreases the overall density of your body and (depending on your lung capacity and your body fat) you could actually then be less dense than water and you’d float.
We’re dealing with airships here, so we don’t really care about water and such. What we need is a gas that is lighter than air. If we can combine a human’s weight with a large amount of a very light gas, then the net results is an object that is less dense than air — which means it will float.
A Sheep, A Duck and A Rooster Walk into a Hot-Air Balloon…
The first successful human-carrying flight technology was the hot-air balloon. When you heat a gas, its density decreases. Hot air is less dense than colder air. So if you attach yourself to a very large balloon full of hot air, then you can float. That’s what the Montgolfier brothers did in 1783 in Paris, France. The origin of the hot-air balloon was military: the problem of the day was how one could launch an assault on the seemingly impenetrable fortress of Gibraltar, which was impossible to approach from sea or land.
The Montgolfier brothers set out to design a hot-air balloon that might allow an attack from the sky. The first living creatures to test the balloon were a sheep, a duck and a rooster. This seems a random choice of animals, right?
Not really. The sheep was thought to have a similar physiology as humans. Although the rooster could fly, it normally wouldn’t fly at the altitudes the balloon would reach. the duck was used to flying at the heights the balloon would ascend to and he was the control animal. A few months later, the first free flight by humans was made, a physics/chemistry teacher and a military officer being the pilots.
Balloons were used in the American Civil war, first for map making, and then for directing fire from artillery on the ground using flag signals. Balloons were used extensively for observations in World War I, often defended by anti-aircraft guns. Note that the hot-air balloon also necessitated the development of the parachute.
But hot-air balloons posed a lot of problems. They were difficult to steer and highly subject to gusts of wind. They were not able to move quickly, which made them sitting ducks for enemies. They caught on fire. They couldn’t carry much weight.
In 1895, the German Count Ferdinand von Zeppelin got a patent for a new type of a craft with a rigid frame that contained several separate gasbags inside. It was like putting a couple hot-air balloons inside a cage, which gave you more flexibility and more lifting power, so a larger payload could be used. This is a schematic for what the frame of one of these rigid airships might looks like.
Note that the shape of the airship incorporated our growing knowledge about aerodynamics. Zeppelin also made some modifications in terms of the lift mechanism. Heating air poses a lot of problems (like fire), so Zeppelin considered low-density gases might be used instead. There were a couple obvious contenders.
He settled on the least dense gas we’ve got: Hydrogen. Somewhere around 400,000 cubic feet of hydrogen were necessary for lifting his 420 foot-long airship. The front had two 15-horsepower engines for steering and power and space for a crew. The first successful flight was in 1908. He planned a 24-our flight, but had to stop because of weather. While on the ground, the storm tore the airship away from its tie-downs and it caught on fire and was destroyed. But there was enough public interest that people sent donations to re-build the ship.
The zeppelins were used in World War I to drop artillery shells (with not a great amount of success, but they freaked out of the Allies big time). While the Zeppelins were never the military weapon the Germans hoped, they had enough of an impact that the Treaty of Versailles prohibited the German military from having any dirigibles.
That didn’t keep them from pursuing airships as a means of transportation and recreation. They gained interest and popularity until the Hindenburg crashed in 1937. The problems with hydrogen, of course, is that it is highly flammable. While there had been plenty of accidents in the past, now there were cameras around to capture the horror of a dirigible larger than a football field going up in flames.
Goodyear’s Role in Aviation
Zeppelins belong to a class called rigid airships because they have an internal structure. That structure, however, adds weight and increases the overall density.
A non-rigid airship is usually called a blimp. The difference is that the non-rigid airship has no internal structure for the outer envelope of fabric. Below is a picture from 2005, when one of Goodyear’s blimps had an accident. When you take the helium out, it’s pretty much a deflated balloon. (Incidentally, no one uses Hydrogen anymore.)
The U.S. military experimented with airships during World War I. They designed their own blimp, called the DN-1 and it was pretty much a disaster because no one involved apparently knew much about blimps. They dug in, went to Europe to see what our Allies were doing, came back and actually put some thought into it, then commissioned bids from U.S. Manufacturers in 1917.
In 1916, Goodyear bought land near Akron to build a plant that could produce aircraft and eventually evolved a company called the Goodyear Aircraft Corporation. They worked with Goodrich and other companies to fulfill wartime needs, ultimately making 9 blimp envelopes using their expertise in materials that were strong and airtight.
After the war ended, Goodyear continued to make airships. Most of the industry was focused on airships for transportation. They were even used for transAtlantic crossing, offering similar amenities to the large boats that usually made the voyages.
The Goodyear Blimp
But Goodyear realizes something else: A blimp was a great means of advertising. They launched their first airship, the Pilgrim, in 1925 and has maintained a fleet ever since. Each blimp class is named GZ- and a number. The GZ stands for Goodyear-Zeppelin, which is a holdover from when they collaborated with the German company to build the blimps. From 1928 to 1987, all the blimps were named after winners of the America’s Cup yacht race, maintaining the analogy between water ships and airships. After 1987, they started getting public input with contests and voting and such.
A blimps works pretty much like a submarine in the air.
The envelope (the outer skin) holds the helium. There are bladders inside the envelope called ballonets that can be filled with air. Just as you taking a breath decreases your density, pulling air into the blimp increases its density. It’s exactly like ballast on a submarine. There are two (one front and one back) so that the pilot can change the attitude of the blimp by making the front or the back heavier.
The gondola can hold up to 6 passengers and 2 pilots. It’s suspended from the envelope through a system of curtains and supports that spreads the gondola’s weight out over the envelope. It has functioning rudders, plus propellers on the gondola that allow the pilots to maneuver. The top speed of a Goodyear blimp is about 50 mph.
I’ve always thought of Goodyear as a tire company and never knew how the blimp came to be associated with it. But Goodyear had a thriving Air/Aerospace business for many years. In 1963, Goodyear Aircraft Corporation became Goodyear Aerospace corporation and did contract work, playing a major role in the first wave of space exploration. Goodyear produced the tires used on the moon vehicles and the flotation devices used for space capsules that landed in the water. They expanded into missile parts, radar and guidance systems, but in 1987, Goodyear sold the company to Loral Space & Communications.
When is a Blimp Not a Blimp?
When it’s the next generation blimp.
Goodyear — like NASCAR — has gone through a number of generations in their designs. The GZ-20 series of blimps was introduced in 1969, in part to carry the electronic screens that allow the blimps to advertise at night. This generation included the Spirit of Goodyear, which was retired after the 2014 Daytona 500 race. If you are in Cleveland, you can see its gondola in the Crawford Auto-Aviation museum there.
The GZ-22 class (don’t ask me what happened to GZ-21) was developed in 1987 as a proof of concept to the US Department of Defense that airships might still be militarily viable. There was only one made: the Spirit of Akron. In 1999, it crashed into trees in Ohio due to a mechanical failure and was lost. No one was injured.
The Next-Gen Goodyear Blimp debuted in 2014. Called Wingfoot One, the new blimp is technically not a blimp. Goodyear has moved to a new design called a semi-rigid. A semi-rigid airship has a keel (or truss) supporting the length of the main envelope. The shape is still supported by the gas, but you can think of it as putting a backbone into the blimp.
Semi-rigid airships existed for a long time, but the invention of low-density but super-strong materials has made them viable again. They are lighter than rigid airships, can be mostly deflated for storage or moving, and can carry greater loads than a blimp. The gondola and engines are integrally attached to the framework, which allows for better distribution of the load (and higher loads).
The airships are made by the German company Zeppelin Luftschifftechnik GmbH, which calls itself the successor to the original Zeppelin company. (If you check out their website, they note that Zeppelin rides make really great Christmas gifts! Of course, they don’t fly from November until early March, so keep that in mind. Oh. And they’re Germany. And I know exactly what I’m asking Santa for this year because they’ll let you tour the factory where they build them, too.)
The LZ-series ships use a carbon-fiber composite materials for the frame. If you look back up to my density chart, you’ll see that carbon fiber composites are much less dense than any metal. I’m showing the frame below. Compare it to the drawing for the rigid airship. This one has a lot fewer tubes.
There are a lot of benefits to the new design. It’s faster (77 mph vs. 50 mph) and it’s more maneuverable. They have a higher payload: up to 12 people (1900 lbs). There are three engines, each 200 hp. It’s got a range of 560 miles and can fly up to 8,530 feet high. It’s also extremely low vibration, which is important for covering sports events (shaky cameras driver producers nuts). But it’s also useful for environmental monitoring research and may facilitate some types of scientific research that previously couldn’t be done as easily or in as controlled a manner.
You won’t really see much of a difference on the outside. The blimp on the left is actually a blimp. The one on the right is Wingfoot One, the first semi-rigid airship — although the concepts of “The Goodyear Blimp” is so familiar to us that the Goodyear people are going to keep calling it a blimp.
The one thing you can’t see from the photos is that the new airship is significantly larger. The old version was 192 feet long, while the new one is 246 feet long.
Wingfoot One is already in service and headquartered in Pompano Beach, Florida. Wingfoot Two was unveiled in April 2016. At it’s height, Goodyear operated eight blimps, but now they have three. And within the next few years, none of Goodyear’s “blimps” will actually be “blimps”. They’ll be semi-rigid airships. But they’ll still be floating over races, giving us great overhead pictures.
Incidentally, the Wingfoot name comes from the Goodyear logo, but is also named after Wingfoot Lake in Ohio, the oldest airship facility and one of the oldest active aircraft bases in the world. There are two other bases: Pompano Beach, Florida and Carson, California, where Wingfoot Two will head in 2017.