Space city.

Finally the International Space Station is almost ready for lift-off. Will it change your life?

A few years from now, when you peer up at the night sky, you'll see not only the moon or stars. You'll witness a diamond-bright, awesome new object--only this one is human-made. The size of a football stadium, orbiting Earth at 28,163 kilometers (17,500 miles) per hour, this super-structure will be the world's largest engineering project in peacetime history. What is it?

None other than the International Space Station (ISS)--a permanent space research laboratory created by thousands of workers in the U.S., Russia, and 14 other nations. When finished, the ISS will span 80 meters (262 ft) long and 109 m (356 ft) wide, with as much work and living space as the passenger cabins of two Boeing 747 jets. And it will cost $40 billion to construct. While many scientists are betting on "spin city" to impact both life in space and on Earth, others question the enormous cost in the name of science.

FLOATING LABS

Barring further delays, the first module of the long-awaited ISS will blast off before the end of this year. (With a minimum life expectancy of 10 years, it was originally scheduled to launch in 1997.) When fully completed around 2004, up to seven astronauts at a time will call the giant complex home, some living there for as long as 187 days. On board this "window to the universe," the ISS crew will perform a diverse array of experiments designed by scientists from around the world.

Some of the many scientific mysteries researchers hope to resolve in space: How do plants and animals behave in the absence of gravity? What are the long-term effects of living in space for humans, both physically and mentally? Can we grow better materials in space to produce better products on Earth?

Among other features, ISS labs will boast a spinning cylinder called a 3-D bioreactor, which grows cell cultures (specimens) like natural tissue to help scientists learn more about human diseases. Also aboard will be a 51-cm (20-in.) optical window to study atmospheric gases, coral-reef bleaching, hurricanes, and other natural Earth phenomena. As scientist Saunders Kramer puts it, "We'll find 10,000 things to do on the station that nobody's thought of or even imagined."

But before astronauts can strap lab equipment to the walls with Velcro (otherwise it would float away), the ISS must be put together piece by piece like giant Lego blocks--and it all must be done in space!

BUILDING BLOCKS

Because of its audacious size, the space station can't be assembled on Earth, former astronaut Rich Clifford explains. Measuring the length of a city block, the ISS would collapse under the weight of gravity--the force that pulls objects downward toward Earth. Instead, smaller modules will be built on Earth. Then U.S. space shuttles and Russian boosters will launch about 45 times over the next five years to deliver more than 500 tons of the ISS. Astronauts and robotic arms will work like hard-hats in space to patch the station together module by module.

The first module, a Russian-built power engine called Functional Cargo Block (FGB, from the Russian name), is scheduled to lift off this fail on a Russian rocket. The FGB carries almost 14 months' worth of fuel--enough to keep the station aloft, as other modules are added. One month later, space shuttle Endeavor is slated to carry Unity, the second module, and rendezvous with the FGB. Astronaut Nancy Curry may have the honor of controlling the shuttle's robotic arm and snatching the FGB from orbit to tow it close to Unity. "Then the arm will pull FGB and Unity together," Clifford explains. Astronauts Jerry Ross and Jim Newman will spacewalk to attach electrical, computer, and fluid wires outside the two modules. These connections will send power between the modules and allow water to circulate for drinking and cooling the air. It should take three spacewalks, each about six hours long, to complete the task.

SPEED CITY

Assembling a huge station in space is no child's play. Imagine building a jet plane while it's flying at 978 km/h (608 mph). The space-station modules will zoom at nearly 29 times that speed! Talk about a space race. How can spacewalkers Ross and Newman keep up? The trick is for them to move at the same speed as the modules!

This is where Newton's first law of motion comes into play. The law says an object will move at a constant speed in one direction until an external force stops or changes its direction. Say two cars speed side by side at 97 km/h (60 mph) down a freeway. As long as both cars maintain the exact same speed and direction, the relative velocity difference between the two is zero--relative to each other, the cars are standing still. So a person could open the doors between the cars and move from one to the other.

When Ross and Newman open the shuttle's door and step out, they'll travel at the same speed and direction as the modules. From their perspective, the modules will stay still--almost like working on a parked car.

Actually, the ISS is parked--in orbit around Earth. But as rockets and shuttles deliver new modules every few weeks, the ISS will expand from a single 20-ton module to its full size: a 520-ton space station. For the growing station, staying in orbit is risky business.

Even at 407 km (220 nautical miles) above the planet, the station is still tugged at by Earth's gravity, although with much less force. So the ISS is in constant (danger of plunging back to Earth. To keep the station aloft, the space shuttle will help boost it to its proper altitude, Clifford explains. About every other flight, the shuttle will carry additional fuel to nudge the station back to its orbit 407 km above Earth.

LITTLE GRAVITY

Staying in orbit is essential for the ISS. After all, its purpose is to be a research lab in which scientists can conduct experiments in microgravity, or near-zero gravity conditions. On the space station, gravitational force equals only one-millionth of that on Earth. A pencil dropped on Earth would fall 1.8 m (6 ft) in 0.5 seconds. On the station, it would take 10 minutes!

In microgravity, plant roots don't push down and leaves don't reach up; crystals grow bigger and become more symmetrical; flames lose their pointy shape and form balls of fire; and human bones and muscles deteriorate. "Part of the scientific research is aimed toward understanding the physiological effects of long-term exposure to space," Clifford explains. At least one experiment, which could benefit aging humans on Earth, will try to determine how to combat bone loss in space.

One of NASA's future goals is to send space explorers to Mars. "That's a fairly long trip," Clifford says. "We want to have the capability of bringing them back in good shape." Building the space station is the first leap.

THINK ABOUT IT

Experts estimate the total cost of the ISS at more than $40 billion, which would provide food and nutrition assistance for all needy Americans for one year. Is the ISS worth it? What do you think?

RELATED ARTICLE: Space Outposts

The idea of living in space is not new. Here's a brief history of the space station --from its earliest conception to the present:

1869

American Edward Everett Hale publishes a short story, "The Brick Moon," about a manned, brick satellite high above Earth. This is the earliest known idea of a space station.

1923

Romanian Hermann Oberth coins the term "space station," which he describes as a starting point for flights to the moon and Mars.

1928

In his German book The problem of Space Travel, Hermann Noordung outlines a realistic plan for a space station and publishes the first blueprint.

1950s

Rocket engineer Wernher von Braun describes a wheel-shaped space station orbiting 1,730 km (1,075 mi) above Earth. As the wheel rotates, it creates artificial gravity so astronauts don't suffer from prolonged weightlessness.

1971

The Soviet Union launches Salyut 1, the first space station in history. Three cosmonauts inhabit the station for 23 days. Unfortunately, soon after leaving salyut, the cosmonaut's space vessel develops a leak and all three die.

1973

Skylab, the first U.S. space station, reaches orbit. The station houses three teams of astronauts. It falls from orbit in 1979 and crashes in the Indian Ocean.

1983

President Ronald Reagan approves the construction of a new space station to prove the U.S.'s superiority in space.

1986

The Soviets launch Mir, the first space station designed to maintain a permanent human presence in space (see sidebar below) Except for two short periods in 1986 and 1989, cosmonauts live aboard Mir continuously.

1993

President Bill Clinton request a redesign of the U.S. space station and invites Russia, Japan, and other nations to join in developing the new International Space Station.

1998

The first module of the International Space Station is set to launch in November--one year behind schedule.

RELATED ARTICLE: MIR mishaps

"A disaster waiting to happen" is how NASA's former astronaut-safety chief, Col. L. Blaine Hammond Jr., describes the ailing Russian space station Mir. The "comet of errors" has looped around Earth for almost 12 years--seven years longer than its expected life in space. So the aging station's "glitches" should come as no surprise.

But the glitches border on life-threatening catastrophes. Last year alone, Mir was riddled by nearly 20 mishaps--among them a fire that smoked-up the entire vessel, oxygen-generator failures that left the crew with a two-month breathening supply, and a collision with a 7-ton cargo ship that damaged a solar panel and punctured a module.

So can any lessons be learned from Mir? Yes, say many NASA scientist: Astronauts have gained enormous experience spacewalking, transferring equipment and supplies between spacecraft, and dealing with constant emergencies.

Best of all, perhaps, is that Russian and American astronauts have learned to work together in space. Mir's astronaut-exchange program with the U.S. marks the first phase in the development of the International Space Station. Now, common skills will come in handy when the ISS's first occupants move into the new station some time next year. Then the Russian Space Agency will put an end to Mir's misery and bury it with a fiery dive into the Pacific Ocean.