NEW YORK, Nov. 26 (UPI) -- A lot of science and technology go into getting Kermit, Barney, Garfield and dozens of other huge balloons into the sky and creating the imaginative floats that weave their way along the Macy's Thanksgiving Day Parade route.
Experts told United Press International each of the 25 floats in this year's parade required months of technical ingenuity and scouring through research and development.
"We adapt from technology used all around the world. We're constantly looking for and working with new and different materials," said vice president of Macy's Parade Studio John Piper.
"For example, we have a new float this year, which is designed to be a mountain that you might see in the Grand Canyon area. This mountain, like many other floats we have, has a secondary form -- it looks as though a rhinoceros is sculpted out of the rock. And we'll have mountain climbers climbing up it and rappelling off it," Piper said. "The materials used to construct this have been developed for use by the studio over the last year -- a hard coat that sprays onto foam and hardens almost immediately, for a weatherproof and climbable shell."
Another monumental effort involves the more than three dozen balloons Macy's will fly, including 15 of its signature giant character balloons, about 60 feet long and 30 feet wide.
The gargantuan balloons first appeared in the parade in 1927 and included Felix the Cat. One long-departed tradition is the releasing of the balloons. They could float for days, with lucky finders claiming prizes.
Every balloon takes four to six months to complete, from the first sketch to when it is ready for flight, Piper explained. The balloons are not hot-air balloons, but are filled with 10,000 to 14,000 cubic feet of helium.
The largest balloon ever, Shamu the baby whale, used over 18,000 cubic feet. The smaller balloons, including the brand-new pumpkin, turkey and dachshund this year, take from 1,000 to 2,000 cubic feet of helium.
"I don't know of any other place in the world where there are helium-shaped balloons made on the size and scale of the Macy's parade," Piper said. "Our balloons are three-to-four-stories tall, and fly from 25 to 60 feet from the ground, so they can tower anywhere from five to 10 stories in the air."
Every giant balloon is multi-chambered.
"If you can visualize a brand-new Garfield balloon that will be in the parade this year, his body is one chamber, his head is another, each ear is a separate chamber, each leg is a separate chamber, each foot is a separate chamber, and the tail is separate," Piper said.
While multiple chambers allow the entire balloon to fly even if one leaks, and piecemeal design is easier from a construction angle, the physics also demand multiple chambers.
"There's a relationship between the properties of pressure and skin stress in each chamber that has to be accounted for," Piper said. "Skin stress is the stretching of the fabric the balloons are made of. Looking at the balloon the shape of a hand, with its fingers spread out, you want to make sure, when inflated, the fingers stick out into position and the skin is nice and firm."
All of the chambers have different skin stresses, Piper explained. "The property of skin stress is such that it depends on the diameter of the chamber. So a chamber that is large and round like Garfield's head will require less pressure to achieve the same skin stress as the fingers. Because of that, there need to be separate chambers, each carrying different pressures."
Piper, a hot-air balloon enthusiast himself, explained although hot-air balloons are sewn together from porous fabric, Macy's balloons must be totally sealed, with zero porosity. Urethane-coated or neoprene-coated fabrics are used, the same kind used to hold air in the inner tubes of tires. Everything is glued and heat-sealed, allowing no holes.
When inflated, the balloons also can experience a phenomenon called superheating.
"When the sun warms the outer skin of the balloon, it can cause the gas inside to expand," Piper explained. "So on all the giant character balloons, there are automatic pressure relief valves to let off some of the gas as needed due to expansion."
After new balloons are tested in outside inflations, all the air is vacuumed out of them to ensure the only gas they carry in the parade is helium. To inflate the balloons for Thanksgiving, six teams work simultaneously on Inflation Day, as Macy's calls the night before Thanksgiving.
Four trailer trucks filled with pressurized helium are required, each with four, 200-feet-long, special jumbo hoses that can snake anywhere around a block and not leak the lighter-than-air gas. The balloons are held in place with 50 tons of sandbags and giant nets covering some 10,000 square feet.
"It's a huge undertaking. We literally close off two entire city blocks," Piper said.
Tarps cover the ground to protect balloons from any abrasion from asphalt, potholes or any debris that might scuff the balloons. On average, it can take from 90 minutes to two hours to fill one large balloon.
To fly each giant balloon requires, on average, 50 handling lines and 60 or 70 handlers. Each also is assigned a pilot, two copilots, a captain and two co-captains that go through extensive training on balloon maneuvering and handler coordination.
Yachting rope is used, which possesses foot increments so handlers know the height of each balloon. A licensed meteorologist with a remote weather station is also on the site, to get real-time information on the meteorological conditions in and around New York.
As for the price of each float and balloon, Piper said: "The Macy's Thanksgiving Day parade is a gift not only to New York but to people watching around the nation and the world. And you never reveal the price of a gift."
Charles Choi covers research for UPI Science News. E-mail firstname.lastname@example.org