748 days in space
At 748 days, Sergei Krikalev, the commander of the International Space Station, has set a new record for cumulative days in space. Aside from his new record, Krikalev has done some pretty impressive things before this most recent achievement as well.
Krikalev, who was born in Leningrad, Russia, in 1958, won the top national prize for daredevil aerobatic flying in 1986 and later received numerous international honours, including “Hero of Russia”, for his spaceflights. He flew twice to the Russian space station Mir – once staying on for back-to-back six-month tours when one of the subsequent two flights to Mir was cancelled.
He also flew on the first joint US-Russian space shuttle mission in 1994, the first mission to assemble the International Space Station in 1998 and was a member of the first crew to live onboard the ISS in 2000.
Widely considered the best, Krikalev apparently has no fear. Not of bone loss, radiation exposure, being alone, or anything else. Or if these things worry him, he doesn’t let anyone know. Some would argue that for doing the incredible things that he’s done, the stories he could tell are worth the risk. God knows, that’s how I would feel if the loneliness didn’t kill me. After all, who wouldn’t want to go into space? I’m not so sure I’d want to spend two years there, though, especially if I had a family waiting for me back on Earth.
But when Krikalev finally does come home, he will have something to worry about: his physical condition. Radiation exposure in space can alter DNA, creating oncogenes, or cancer precursors. When DNA is damaged by radiation, it is repaired, except that when it is repaired, it can be fixed incorrectly: during repair, the strands are stuck back together and smoothed out, and no comparison to the original strand is made, which can lead to incorrect DNA sequences. (This incorrect repair is also the reason that people can get skin cancer when their skin cells are damaged by UV light.)
Cancer risks aside, cosmonauts and astronauts also sometimes have difficulty adjusting to social life on Earth again. Thus far, Krikalev has been remarkably resilient to the depression-like symptoms that often take hold of space travelers after the initial euphoria and excitement of being in space wear off, so this probably won’t be much of a problem for him, given that he’s done a one-year stint in space before this mission. Not that frequency of occurrence makes social adjustment any easier, of course.
Perhaps the biggest, most immediate health concern is over the density of his bones. Even with methods in place to reduce bone density loss, astronauts and cosmonauts lose an average of 1.5% of their bone density for every month they are in space, and he’s been there for almost 25 months, and it will be 27 months by the time he finally comes back home. The average post-menopausal woman loses about 1.5% of her bone density per year. So in theory if he were a post-menopausal woman, Krikalev will have lost the equivalent of 27 years of bone density when he comes back to Earth. Growing bone-mass back can be achieved, but it is a long process, and it is unknown how the quality of bone mass compares to that which was lost. Recall that bone marrow turns into fat as people age, and Krikalev has done quite a bit of aging in the last 2 years. I wonder if astronauts and/or cosmonauts take any osteoporosis drugs like Fosamax or Actonel? Hrm. I wonder who I could ask that would know…
Update: Bisphononates like risedronate and alendronate have been studied in bedrest studies (physiological equivalents to extended space travel), but not used in space missions.
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Just a correction: His record is for cumulative days in space, not consecutive. He’s only been up there since mid-April.
Comment by Mike — August 16, 2005 @ 4:13 pm
Oh, nuts.
Comment by Rian — August 16, 2005 @ 4:45 pm
[...] A month ago to the day, I wrote about Sergei Krikalev’s record-setting time in space: 748 days. I also mentioned that it was at possible detriment to his health: being in a “zero G” environment takes its toll on the body in numerous way. Chief among them is bone density and muscle loss. The body doesn’t need the excess bone and muscle tissue to support itself in space so it gets rid of it to be more efficient. Obviously this poses some problems when you return to Earth and are unable to stand up or otherwise function normally, so astronauts on long space missions exercise to minimize the impact to their health. [...]
Pingback by polyscience.org » The Space Cycle — September 16, 2005 @ 10:11 pm