The last time Carl Walz strapped in for a ride home on the space shuttle, he was sitting next to a recumbent Shannon Lucid, ready to assist if she suffered any immediate ill-effects upon return from her 188-day spaceflight.
This week, it will be Walz in the reclined position on the shuttle Endeavour's middeck, along with space station astronauts Dan Bursch and Yuri Onufrienko, as they make landfall after surpassing Lucid's record-long flight on Mir by at least seven days.
Shuttle launch delays extended both Lucid's 1996 flight and the current crew's stint aboard the International Space Station past NASA's optimal four-and-a-half-month-long mission. The protocol for recovery, however, remains the same -- take it slowly.
Benefiting from Lucid's and six other American astronauts' stays aboard the Russian space station Mir, Walz and Bursch will begin a carefully supervised re-adaptation program immediately upon their return to the Johnson Space Center in Houston.
Beginning with a week or so of stretching and massage, the astronauts will then gradually begin more rigorous exercise programs, said NASA flight surgeon Terry Taddeo, including daily walks and short periods of jogging. Within a few weeks, Walz and Bursch may begin short workouts with free weights or Nautilus equipment in the gym to help rebuild their muscles.
Lucid, the third American to serve on Mir, had no such formal re-adaptation program. A healthy 53-year-old when she made her record-long flight, Lucid's only real bad spell, however, came when the transport vehicle she and her crewmates climbed into after landing started to roll.
"I walked in and sat down and the vehicle started to move," recalled Lucid in an interview with United Press International. "I remember thinking, 'Oh my goodness -- this is different.'"
Lucid said, "I get motion sick in cars and I thought, 'This is just like driving around the mountains in Arkansas.'"
After she slept off her dizziness and nausea, Lucid flew back to Houston the next day and spent a quiet weekend with her children and husband -- going to the bookstore, attending church services and picking up around the house.
She said she had a bit of a nasty reminder of her long stay in space when she went to pick up the newspaper and absent-mindedly walked barefoot on dried pine needles. After six months in microgravity, her weight-free feet had lost all their calluses, becoming as soft and as tender as baby's skin.
"I ran across those pine needles and I thought, 'Oh my goodness, I'm gonna die,'" Lucid said. "It took a while for the calluses to build back up."
Lucid attributes her swift recovery to a disciplined exercise program she followed aboard Mir, a protocol that has become mandatory for station crewmembers. She worked out on her own initiative in part to try to avoid the sore muscles and difficult re-adaptation she endured upon return in 1993 from a 14-day shuttle research mission that was too busy for exercise.
"When I came back from (the 1993 shuttle mission) my legs hurt and I thought that when I came back from the Mir flight, that my muscles would be sore as well ... But I never had any muscle aches," Lucid recalled. "It was a very pleasant surprise."
Lucid, a biochemist who is now NASA's chief scientist, cautions that astronauts' re-adaptation to Earth's gravity is an individual process -- Walz and Bursch may have very different experiences than she did.
In addition to neurological and vestibular, or balance, changes, living for extended periods of time in microgravity affects how much blood the body holds and how efficiently the heart works, as well as bone and muscle mass, said Taddeo.
In time, the body seems to recover fully from most space-induced afflictions. One of the few potentially irreversible effects of space life, however, is radiation exposure. While the Earth's magnetic field offers some protection from cosmic rays and other celestial radiation, living outside the planet's atmosphere raises astronauts' exposure to potentially dangerous high-energy beams.
Lucid, for example, who flew during a relatively quiescent time in the sun's solar cycle, received the radiation dose equivalent of eight chest X-rays a day for every day she was in space.
"That's a fair amount of radiation," she told UPI.
NASA flight rules cap astronauts' lifetime exposure to radiation at the level that would trigger a one percent increase in the chance of developing cancer -- a figure that varies depending on a person's age, gender and prior exposure record. For a 45-year-old man, however, that limit would be about 18 months cumulative time in space during a benign solar cycle period. During a more active period of time, however, with many solar flares and storms, the overall limit for a 45-year-old man decreases to about nine months in orbit, NASA flight surgeon Frank Cucinotta said.
Walz, who has made three previous shuttle missions, will become the U.S. astronaut with the most time spent in space -- 229 days -- if the shuttle lands as planned on Tuesday. Walz's commander Onufrienko is among the 20 cosmonauts, however, who have topped that U.S. benchmark by at least 100 days.