- The Washington Times - Wednesday, August 31, 2005

Neil Armstrong took “one small step for man, one giant leap for mankind” with the first moonwalk in 1969.

Scientists are still waiting for the “giant leap” in re-creating microgravity — the virtual absence of gravitational forces — here on Earth, or even in the skies above.

Since the 1960s, researchers made do with a plane playfully dubbed the “Vomit Comet,” the KC-135A, and similar models, which can reproduce weightlessness for brief spells. The plane and neutral buoyancy water tanks have been astronauts’ best bet to prepare for the surreal feeling of walking without force tugging at them.

In theory, microgravity can be achieved, albeit briefly, by dropping an object from a tall building. For longer periods, anywhere from 20 to 30 seconds, an airplane can fly in a parabolic arc repeatedly to create an environment in which Earth’s gravity is essentially neutralized.

“It makes an ideal laboratory,” says Bill Parke, a physics professor at George Washington University, even if the time limits are considerable.



Another way scientists give astronauts a sense of what they will experience in space is via underwater tank programs.

“It’s not really gravity-free, but they can pretend they’re acting as if they’re in outer space,” Mr. Parke says of the experience. “They’re floating free in water. They can have some sense of what it’s like [in space].”

He says astronauts sometimes practice repair procedures in such an environment.

Robert H. Gowdy, chairman of Virginia Commonwealth University’s physics department, says the buoyancy tanks may be imperfect but they do help astronauts adjust to space movement.

“They can figure out how their bodies will move. Everything is different in that situation. It’s no longer any up or down,” Mr. Gowdy says.

Astronauts working with these tanks have weights attached to their extremities until each reaches neutral buoyancy.

“You don’t sink or rise to the surface. The slow motion produces the body mechanics of being weightless,” says Mr. Gowdy, who adds that if an astronaut moves his or her body quickly, “the water resistance spoils the effect.”

The simulation may be effective, but it doesn’t truly mimic the real feeling of space.

“The internal organs are still feeling gravity,” he says.

It’s one thing for researchers to help astronauts get a feel for microgravity’s effect on movement, but it’s a far more complicated matter when dealing with said gravity’s impact on the body.

According to NASA, astronauts on missions lasting longer than a year can lose as much as 20 percent of their bone mass. That leaves them susceptible to fractures and the possibility of renal stone formation due to calcium mobilization from bone.

The pool of astronauts that have overcome this obstacle is a shallow one.

Dr. Jonathan B. Clark, a neurologist and flight surgeon with NASA, says only a handful of people have flown missions longer than 12 months.

Those who do must cope with a series of medical complications, some of which can be serious, says Dr. Clark, who also works as a space medicine liaison for the National Space Biomedical Research Institute in Houston.

Ten percent of astronauts experience lightheadedness when they return to Earth’s gravitational forces.

“All that fluid that was now in their upper extremities is falling down back into their legs,” he says, adding astronauts often wear a special suit that inflates tightly around the body to prevent, or at least slow, fluids from dropping quickly down the body.

Other changes are harder to alleviate.

The simple act of standing activates and engages a series of muscle groups to keep one upright. In microgravity, those muscles aren’t needed, one reason why astronauts suffer muscle loss due to neglect while in space.

“The muscles you use in day-to-day life, they’re not used and start to shrink in diameter,” he says. “The same goes for the heart. It doesn’t have that gravity to overcome [in pumping blood].”

Astronauts are instructed to work out as vigorously as feasible while in space, but that only slows the muscle loss. It doesn’t prevent it.

Astronauts who return home after spending extended time in space must go through the kind of physical therapy endured by anyone who required extended bed rest or was rendered motionless for a spell.

Dr. Clark adds that astronauts also must deal with the consequences of living in a small space as well as radiation from solar particle events on top of gravitational challenges.

Roger Launius, chair of the Smithsonian’s National Air and Space Museum’s history division, says it takes astronauts about four days to adjust to life back on Earth. A month later, if the proper precautions were followed regarding recovery, they should be back in full health.

“Space is an exceptionally hazardous environment, this place where we weren’t meant to be … not that we shouldn’t go there,” Mr. Launius says.

Mr. Launius says space may be gravity-free compared to Earth, but gravitational forces “exist everywhere in the universe.”

“There may be one narrow window where the gravity that pulls you in one direction is equal to the gravity pulling you in another,” says Mr. Launius, adding the moon’s gravitational tug is roughly one-sixth that of Earth’s.

Some of the research being conducted on matters of gravity and space could have ramifications back here on Earth.

Dr. J. Milburn Jessup, professor of surgery and oncology at Georgetown University, says researchers are examining why cell death sometimes occurs at a quicker rate in reduced gravity environments.

Cells naturally include a death mechanism as part of a normal process that prevents excessive numbers of cells, but this mechanism can be triggered by reduced gravity situations, says Dr. Jessup, who also is a special assistant for cancer diagnoses at the National Cancer Institute.

If Dr. Jessup and his peers can decode why these cells start to die, it could help them explain why otherwise healthy cells die in cancer patients.

“It is exploratory,” he says. “A number of people at NASA are not at all convinced it’s real. There’s a fair amount of information that indicates viral reactivation has been a problem in space flights.”

Mr. Gowdy says one way scientists can help astronauts thrive outside Earth’s atmosphere for extended periods is to re-create Earth’s gravitational pull in space via rotation. That can be accomplished by having two spaceships rotating around each other.

“It does add a whole lot of complexity,” he says. “Technically, it’s an easy solution. Engineering-wise, there’s a lot more to do.”

Unfortunately, plans to replace the “Vomit Comet” and buoyancy tanks aren’t even on the drawing board, he says.

“There isn’t a way to shield against gravity [on Earth],” he says.

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