Astronauts Leave Earth at Their Peril
Human bodies can survive in space for awhile.
The damage adds up over time.
To the great relief of the newly-formed NASA in the 1960s, the first manned spaceflights were successful, and astronauts like Alan Shepard and John Glenn returned to the ground with no apparent ill effects. The moon landings saw astronauts do well for days at a time away from the home planet; the Apollo 17 mission, celebrating its 50th anniversary this December, lasted 12.5 days. During the International Space Station era, astronauts have survived extended stays for up to a year in low earth orbit.
It takes human space travelers a few days to become re-accustomed to Earth gravity, but they soon recover and eagerly await their next flight. Before thinking that Star Trek is coming true in our time, trekkies had better consider these findings about risks to astronauts in the long term.
Aluminium alloy could boost spacecraft radiation shielding 100-fold (New Scientist, 20 Oct 2022). First, some good news. Shielding a spacecraft from radiation for long-term flights to the moon, Mars or beyond has long been a concern. A new aluminum alloy appears to do a much better job than previous materials, which could help in spacecraft design or in construction of a lunar base. Now, some bad news:
While they didn’t test how well the material would block radiation for astronauts, structural features indicate that it might be better than currently used materials, he says.
While the material may hold up for longer, it may not be suitable to protect humans during long-term missions. One problem noted earlier is that high-energy cosmic rays impacting atoms in materials tend to spray showers of secondary particles that can enter cells and cause mutations. The only effective shield against those rays would be impractical: meter-thick walls filled with gas. See 23 June 2016, 6 Jan 2013, and 23 Sept 2006 for radiation risks to astronauts traveling beyond Earth orbit. And even with effective shielding, astronauts become at risk of bone loss and muscle atrophy the longer they live in weightless conditions.
Astronauts’ blood shows signs of DNA mutations due to spaceflight (Space.com, 5 Sept 2022). Elizabeth Howell reported, “The researchers stored astronaut blood for 20 years to see how short space shuttle flights affected spaceflyer health.” Blood was collected from 14 astronauts on Space Shuttle missions between 1988 and 2001. Examination of the frozen blood samples revealed mutation counts higher than normal, even accounting for the astronauts’ ages, but not high enough for concern.
The somatic mutations seen in the genes was less than two percent, however. Those individuals who breach that threshold face more risk in developing cardiovascular disease and some forms of cancer, the statement said.
“The presence of these mutations does not necessarily mean that the astronauts will develop cardiovascular disease or cancer, but there is the risk that, over time, this could happen through ongoing and prolonged exposure to the extreme environment of deep space,” Goukassian added.
Those flights averaged 12 days in length. The article does not speak of longer flights, but it seems reasonable to conclude that the longer the exposure to the “extreme environment” of space, the more the mutation counts rise. Those flights were also in near earth orbit, where some protection from the magnetic field exists. The farther away from Earth, the more the exposure to high-energy particles from the solar wind and from cosmic rays.
Can we live long and prosper in space? The astronaut health dilemma (Space.com, 20 Sept 2022). Space medical scientists are considering building a database of health effects on humans during prolonged missions, reported Leonard David. There are about 120 retired astronauts still alive, and some ill effects from space travel may not appear till decades later.
This is particularly true for those “chronic/degenerative” risks, such as malignancies secondary to radiation exposure, which may take decades to reach full expression.
Bottom line: given that the total number of humans who have flown in space is just over 500, and that a growing proportion of International Space Station (ISS) crews are indeed international, it is essential to start capturing medical data from those space travelers.
Effects of moon dust on the 12 astronauts who went to the lunar surface would also be good to study, the article says. Medical scientists made the case for an international database on health effects of space flight in the journal Acta Astronautica.
Our bodies are matched to the Earth’s surface environment. The trouble is, our minds are designed for grand flights of imagination. In the mind’s eye, we can fly throughout the universe, land on any planet, and walk and breathe the air. We can imagine things that do not exist, and ask, why not? Dreams can lead to technologies that can fulfill the dreams, if only partially. But dreamers, like astronauts, must come back to Earth and face reality. Captain Kirk and Mr Spock’s adventures did not happen in outer space. They were filmed on a back lot in Burbank, California, in Earth gravity and an oxygen-rich atmosphere.