CAPE CANAVERAL, Fla. -- U.S. astronaut Joe Acaba will return to Earth on Sunday after four months in weightlessness while flight medical officers launch a six-week effort to help him readjust to living in normal gravity.
Acaba is scheduled to depart the International Space Station at 7:11 p.m. EDT Sunday.
Strapped into a Russian Soyuz spacecraft, Acaba and two cosmonaut colleagues are supposed to start a supersonic atmospheric re-entry at 9:57 p.m. The three space explorers will hit the upper fringes of the atmosphere at an altitude of about 400,000 feet, and then they'll begin feeling the first tugs of gravity after 125 days in space.
Landing is scheduled for 10:53 p.m. in a remote desert in north-central Kazakhstan.
Acaba and Russian cosmonauts Gennady Padalka and Sergei Revin might feel weak, woozy and clumsy. They could have difficulty concentrating. They could be nauseous. They could have trouble walking a straight line.
All three are in for lengthy physical rehabilitation programs.
"The goal is to get their strength and all their function back to their preflight baseline," said NASA flight medical officer Steve Gilmore. "And in 45 days, with folks working hard, typically we get people to where they were before they launched."
Data from decades of long-duration human spaceflight show space explorers who live and work in weightlessness go through physically difficult returns to normal gravity.
Muscles have atrophied in a weightless environment where astronauts and cosmonauts can float and fly like Superman. Bone loss is significant. Lung function is lost. The immune system is weakened. The heart suddenly has to work a lot harder to pump blood. The inner ear is affected and balance is difficult if not unachievable.
"During re-adaptation to Earth gravity, three physiological systems are significantly compromised," NASA astronaut and physician Michael Barratt wrote in Principals of Clinical Medicine for Space Flight with co-editor Sam Pool, chief of the Medical Sciences Division at NASA's Johnson Space Center in Houston.
The musculoskeletal, neurovestibular and cardiovascular systems are so decimated that a return to normal gravity produces "serious functional and performance limitations for returning deconditioned crewmembers."
So Russian recovery forces augmented by NASA flight surgeons will flock to the landing site north of Arkalyk, Kazakhstan.
Whether the spacecraft is right side up or on its side, specialists will extract Acaba and his cosmonaut colleagues from the Soyuz one at a time, and then carry them to seats that have been set up nearby.
Sometimes the returning space explorers are given floral bouquets. And satellite telephones so they can call loved ones back home.
Their next stop will be an inflatable medical tent, where flight surgeons will start post-flight medical tests that document the condition of the astronauts and cosmonauts just after landing.
An hour later, Acaba, Padalka and Revin will head off from the landing site and soon thereafter, part ways. The two cosmonauts will be flown to Moscow, and Acaba will take a 20-hour flight back to Houston, with a couple of stops along the way.
The stops will allow Acaba to stretch his legs, and, after four months of sponge baths, perhaps take a shower.
Flight surgeon Gilmore said that's not as big a deal as advertised.
Many returning astronauts "have commented that you just don't miss it as much as you might think," Gilmore said, "which I find a little hard to believe."