The official countdown clock at the Kennedy Space Center is ticking down to the end of an era.

Weather permitting, today's liftoff of the space shuttle Atlantis, scheduled for 11:26 a.m., will be the last space shuttle launch in history.

Two North Carolina research teams - from UNC-Chapel Hill and N.C. State University - will be on hand to watch. Each has experiments aboard Atlantis.

"It's incredibly exciting to be involved in a shuttle mission of any sort," said Caroline Smith, an NCSU researcher working on a plant growth experiment. "But in particular, to be involved in the last one is a real treat."

The plant project looks at how plants grow in extreme environments. Researchers from UNC-CH and NCSU's joint biomedical engineering program also have a study on board, looking at ways to slow bone loss.

After the final launch, some will mourn the shuttle program, remembering its successes. Directly or indirectly, the program enabled countless scientific advances in fields ranging from astronomy to biology. Historically, the shuttle program carried the first women and African-American astronauts into orbit.

Despite the shuttle program's successes, though, others will say good riddance.

"The shuttle was created to make transportation to low Earth orbit economical, safe and reliable," but it failed on every count, said Alex Roland, a former NASA historian and a professor emeritus at Duke University. "It never did the things necessary to make manned spaceflight practical."

Practical or not, the space shuttle will be missed by many Triangle researchers.

The two experiments due to launch today may be conducted in space, but researchers emphasize the relevance of the research for those of us who never leave Earth.

Halting bone loss

Bone loss, for instance, is a problem that matters to both astronauts and osteoporosis patients, said Ted Bateman, professor of biomedical engineering in the UNC/NCSU program and the leader of the study on Atlantis.

Astronauts' bones weaken when they travel in space, just like the bones of those suffering from osteoporosis. The difference is the amount of time it takes. An astronaut's bones can grow much weaker after spending just a few weeks in "microgravity" - the weightless environment of space. On Earth, similar changes take years.

"There are many things that microgravity does that models human aging, but in a very accelerated way," said Bateman.

By studying space travelers after short periods in a weightless environment - in this case, space-traveling mice after 12 days aboard Atlantis - Bateman's team hopes to learn how to prevent bone loss in osteoporosis patients.

Helping plants thrive

Similarly, the NCSU team studying plant growth thinks its work in space can help us understand the ways plants respond to extreme environments on Earth. Researchers led by Imara Perera, professor of plant biology at NCSU, are looking at how we can control plants' response to signals from extreme conditions. As many a gardener will tell you, plants don't grow very well in stressful conditions, whether that stress comes from the lack of gravity or a more mundane lack of water.

If we learn how to control a plant's response to stressful signals, though - like learning to calm down a frightened child - then we could one day design plants that thrive in tough places, Perera hopes.

"Even though the shuttle program is ending, the International Space Station is kind of just starting," she said.

Her team's experiment will be conducted aboard the space station, though it will be delivered by Atlantis. The end of the shuttle program will only make it harder to get materials there and back, Perera said.

Bateman also is optimistic. With a few modifications, his team's experiment could be conducted aboard the space station, he said. Plus, new commercial launch vehicles may soon be available to deliver experiments and supplies to astronauts on the station.

Relying on Russia

Because the space shuttle lacks an immediate successor, the end of the program will change U.S. human spaceflight. American astronauts will still travel to the International Space Station, but without a NASA launch vehicle, they'll have to hitch a ride aboard a Russian Soyuz spacecraft to get there.

In the long term, both teams of Triangle researchers think that human spaceflight will continue, and that eventually, we will go far farther than our current work in Earth's orbit.

Exploration, Bateman said, "is fundamental to what humans do and what (we) are."

helen.chappell@newsobserver.com or 919-829-8983