Lift off! Taking to the skies with helium balloons.

DID YOU KNOW?

* Balloon pilots prefer to fly soon after dawn or just before sunset. That's because the winds tend to be calmest during those times of the day. The calmer the winds, the safer the conditions for navigating balloons.

* Balloonist John Ninomiya may fly solo, but he needs a team to help him pull off his helium-balloon stunts. Approximately 15 people help him inflate the balloons--a process that could take up to two hours. While in the air, Ninomiya keeps in touch with a ground crew via two-way radio. The crew follows Ninomiya flight path by car and picks him up at the landing spot.

* Ninomiya also flies cloudhoppers. Similar to cluster ballooning, it is a solo-piloted balloon flight. But instead of using helium balloons, the pilot wears a fuel tank and a harness strapped to a hot-air balloon.

CRITICAL THINKING:

* What are some safety precautions that a balloonist must take before lifting off, while in the air, and during landing?

CROSS-CURRICULAR CONNECTIONS:

HISTORY: Research to create a historic time line on how ballooning began and how it has changed over time.

RESOURCES

* For a fun way to learn about the atmosphere, check out NASA's Interactive Atmosphere Simulator: www.grc.nasa.gov/WWW/ K-12/airplane/atmosi.html

* Watch a short video clip of John Ninomiya hoisting a giant octopus balloon sculpture through the air at: www.tbayer.com/FlyingOctopus.html

* Read about the history of ballooning at www.pbs.org/wgbh/nova/balloons/science/history.html

How many helium balloons would it take to lift a person off the ground? John Ninomiya has performed this stunt about 40 times. And each time, he has been attached to enough balloons to fill five 8 meter (25 foot)-long trucks.

But don't start saving your allowance to buy balloons. Unlike you, Ninomiya is an expert balloonist. Before taking to the skies with helium balloons, he piloted hot-air balloons--an activity that requires a license from the Federal Aviation Administration (FAA). "It takes a lot of skill to pilot balloons," says Ninomiya. "I don't recommend anyone to try it without training."

FLIGHT CHECK

Ballooning requires physics know-how, says Ninomiya. Helium balloons float because the gas inside is seven times lighter than the air outside. Every cubic meter of helium in balloons gives enough buoyant force (upward force on an object immersed in air or liquid) to lift 1 kilogram (2.2 pounds) of matter.

For each flight, Ninomiya fills supersize balloons with approximately 227 cubic meters (8,000 cubic feet) of helium. That volume of gas is more than enough to lift his 82 kilogram (180 pound) body--but the extra balloons will come in handy when he starts navigating.

Ninomiya doesn't want to fly away uncontrollably. So he counters the balloon cluster's lifting force by wearing ballast. He straps on water-carrying bags filled with enough liquid to weigh down his body.

TAKE OFF

To ascend, Ninomiya releases some water. With less weight pulling on the balloons, buoyancy increases. To descend, he pops balloons to reduce the buoyant force. And when Ninomiya finds an altitude at which he wants to hover, he adjusts the balloon-to-ballast ratio until he's neutrally buoyant. "That means that I even out and can fly level," he explains.

Ninomiya usually soars approximately 1.2 kilometers (4,000 feet) above sea level. But once, he ascended to an altitude of 6.5 km (21,400 ft). The trip was breathtaking in many ways: The higher up in the atmosphere, the thinner this planet-surrounding gas layer becomes. With fewer air molecules, breathing becomes difficult. "I had to bring an oxygen tank," he says.

This over-the-top journey also meant possible encounters with jet planes. Ninomiya used a two-way radio to communicate with air-traffic controllers. He also wore a transponder, which transmitted his whereabouts to radar screens.

FLIGHT PATH

Besides flying up and down, Ninomiya also steers the balloon cluster in different directions. How? Because wind direction changes at different altitudes, "you want to fly to an altitude where the wind will take you in the direction that you want to go," he explains.

To gauge wind directions aloft, Ninomiya launches a party balloon before he lifts off. Then, he observes how it drifts. He also calls the FAA for a wind forecast. "They will say something like: At 3,000 feet, wind is coming from the east," says Ninomiya. An altitude meter helps him soar to the desired heights.

EARTH BOUND

When Ninomiya is ready to land, he searches for open areas, such as an empty field. But when he can't find an ideal spot, he looks for alternatives. "I've surprised people by showing up in their backyards," he says.

CHECK FOR UNDERSTANDING

DIRECTIONS: Fill in the blanks to complete the following:

1. Helium balloons float because the gas inside is--times--than the air outside.

2. Every--of helium in balloons gives enough--, or upward force on an object immersed in air or liquid, to lift one kilogram (--pounds) of matter.

3. To counter the helium balloons' lifting force, Ninomiya wears--, which consists of water-filled bags, to weigh down his body.

4. When Ninomiya finds an altitude at which he wants to hover, he adjusts the balloon-to-ballast ratio until he's--.

5. The higher up in the--, the thinner this planet-surrounding gas layer becomes. With fewer--, breathing becomes difficult.

ANSWERS

1. seven, lighter 2. cubic meter, buoyant force, 2.2 3. ballast 4. neutrally buoyant 5. atmosphere air molecules