Our place in space.

Kennedy Space Center, Cave Canaveral, Florida, January 1996 - A crew of astronauts prepares for a routine mission aboard space shuttle Endeavor. In the tense moments before liftoff, they will probably think back to a January 10 years ago when a "routine" spaceflight turned into a national disasaster. That's when space shuttle Challenger exploded just seconds after liftoff, killing all seven crew members.

Since then, astronauts have flown nearly 50 shuttle missions. But some people still wonder whether sending humans to space is worth the risk - or the cost. What do you think? Read on, then debate and decide.

THE RISKS

Human space exploration is risky, says John Charles, a NASA lifescientist. That's because space lacks many things humans need to survive, like oxygen to breathe. Temperature in Earth's orbit can rise to a blazing 121[degrees]C (250[degrees]F) in sunlight and drop to a bonechilling -45.5[degrees]C (-50[degrees]F) on the "night" side of Earth.

So spacecraft must be loaded with life support systems - equipment to control the temperature, protect astronauts from solar radiation, keep air circulating, and dispose of human waste. Space shuttles even have two or three models of each piece of equipment aboard. "The extra gear is a safety measure," says NASA's James Hartsfield. "If something breaks down, the crew can use the remaining equipment."

But all that equipment is very expensive - and heavy, says Alex Roland, a space historian at Duke University in North Carolina. That means human space missions cost a lot to launch. For example, the space shuttle "burns nearly two million kilograms of expensive fuel just to get into orbit," Hartsfield says.

ROBOTS RULE

Some people say the best way to avoid these costs - and the risks of sending humans into space - is to send robotic spacecraft (also called probes) to explore space instead.

With no need for life support systems, "robotic spacecraft are smaller and cheaper to launch than space shuttles," says Jim Doyle of the Jet Propulsion Laboratory in California.

Robotic probes can also endure the extremes of space, says Duke University's Alex Roland. For example, Galileo, a probe launched in 1989 to explore Jupiter, recently passed through temperatures that could instantly kill an astronaut - about -240[degrees]C (-400[degrees]F), Roland says. "And unlike humans," he adds, robots don't have to be fed and they don't get tired.

"Robots can also travel much longer and for greater distances than humans," Roland continues. And probes don't have to come back. Voyager, a space probe that blasted into orbit in 1977, still transmits radio signals from outside the solar system t, controllers on Earth.

In fact, robotic space probe, traveled to - and sent back from - every planet in our solar system, except Pluto. Astronauts have only made it as far as the Moon.

SNAP DECISIONS

Still, some people say robots could never replace humans in space. In addition to being able to respond quickly to emergencies, only humans can fully appreciate the wonders of space.

"Nothing can replace a pair of eyes, hands, or the human brain," says Thomas Billings of the Institute for Telerobotic Space Development in Oregon.

"Unlike robots," agrees David Brandt of the National Space Society in Washington, D.C., "humans don't have to wait for commands to take action." If something goes wrong on a mission, humans can make snap decisions and make repairs. Robots can't.

For example, an umbrellalike antenna on the spacecraft Galileo got stuck while opening in space in 1991. For almost two years, engineers sent messages to the probe in an attempt to free the antenna. But nothing worked. The result: Galileo will send back much less data than originally planned. Humans, on the other hand, recently repaired the blurry-eyed Hubble Space Telescope (see SW 11/2/90, p. 14).

BIG PLANS AHEAD

"One of the wonderful things about the human mind is its ability to wonder about the unknown and reach for it," says Brandt.

That's why NASA is going ahead with plans to build an international space station by the year 2002. On board, scientists will conduct experiments to study the physical effects of long-term stays in space.

Though programs like the space station are expensive, Brandt says, people would be much less supportive of space exploration (that is, they wouldn't want to pay for the research) if humans didn't blast off. The notion of people traveling to the "final frontier," he says, is what makes space exploration exciting.

What do you think? Should humans continue to travel into space? Read what some of your peers think (right). Then decide for yourself.

THE UPS AND DOWNS OF HUMAN SPACE EXPLORATION . . .

4/1261 First human in space, Soviet cosmonaut Yuri Gagarin

5/5/61 First Americian in space, Alan Shepard

5/25/61 President John F. Kennedy commits America to sending humans to Moon.

2/20/62 Astronaut John Glenn orbits Earth three times.

6/16/63 First female Soviet cosmonaut, Valentina Tereshkova, spends 71 hours in space.

3/16/66 Gemini 8 astronauts make emergency splashdown after 10 hours in space.

1/27/67 Apollo 1 astronauats killed in a fire during a ground test.

4/24/67 Soviet cosmonaut Vladimir Komarov dies while returning from space.

12/24/68 First humans orbit Moon (Apollo 8).

7/20/69 First humans land on Moon (Apollo 11). 4/14/70 Apollo 13 scraps moon landing after an onboard explosion.

5/14/73 Launch of skylab, America's first space station

7/15/75 Apollo links up with Soviet Soyuz spacecraft.

4/12/81 Launch of Columbia, first space shuttle

6/18/83 First female American astronaut, Sally Ride, orbits Earth in shuttle.

2/7/84 First untethered "space walk."

4/6/84 First satellite repaired in orbit by shuttle astronauts.

1/28/86 Space shuttle Challenger explodes killing crew of seven. 2/8/87 Soviet's Mir becomes first continuously inhabited space station.

9/29/88 First post-Challenger space shuttle flight

6/27/95 During America's 100th human space flight, space shuttle Atlantis docks with Russian Mir space station.

The Future? Proposed international space station may be base for future human space exploration.

SPACE GREATS:     HUMANS             vs.   ROBOTS

Longest stay      Cosmonaut Valery         Pioneer 10,
in space:         Polyakov spent           launched for a
                  439 days in space        Jupiter flyby in
                  aboard the space         1972, is still in
                  station Mir.             our solar system.

Greatest          Apollo astronauts        Pioneer 10 has
distance          traveled                 traveled about
traveled:         382,000km                10.1 billion km
                  (237,370 mi) to          (6.3 billion mi).
                  the Moon.

Places visited:   Moon (6 times            Moon (9 times);
                  from 1969-1972);         Mars (7 times);
                  thousands of orbits      Venus (6 times);
                  around Earth             Jupiter (4 times);
                                           Saturn (2 times);
                                           Uranus (2 times);
                                           the Sun, Mercury,
                                           Neptune, (once each)