A just released report from the National Academies, Preparing for the High Frontier: the role and training of NASA astronauts in the post-space shuttle era, describes the challenges that NASA faces in staffing its astronaut corps in the coming years. More important, however, is some new information buried in the report about the hazards of long term exposure to weightlessness.

For example, it seems a significant number of astronauts have come back from spending months at ISS with serious vision problems, caused by a newly discovered condition dubbed papilledema, the swelling of the optic disk.

7 of 15 crew members examined had papilledema post flight (short and long duration), with some lingering substantial effects on vision. [emphasis in original]

These astronauts were subsequently not qualified to fly on later space missions.

In addition, the report described how there have been 26 elbow or shoulder injuries in the last year, five of which required shoulder surgery. The report said that the shoulder injuries were “attributed to working in a spacesuit.” Unfortunately, the report does not provide any details about how those injuries occurred. Nor does it say whether it was the American or Russian spacesuits that caused the problem.

These health problems were in addition to the well known issue of bone density loss, caused by long term exposure to weightlessness. It appears that recovery from this bone loss takes longer than previously thought, as much as 3 years for a six month mission.

Finally, the issue of radiation was noted. It seems that there are actually fewer radiation safe days on ISS during solar minimum, despite the lack of sunspots, solar flares, and coronal mass ejections. Instead, the inactive sun during solar minimum allows more galactic cosmic rays to reach the space station in Earth orbit. The result: a larger radiation risk during solar minimum.

Since there is a strong chance the Sun is about to enter an extended period of no sunspots, the resulting increase in cosmic rays will thus make it even more difficult to make interplanetary travel safe for future explorers.

These health issues — along with other factors related to the end of the shuttle program — suggest that NASA might have serious trouble staffing the space station. According to the report,

The committee noted that the Astronaut Corps is already experiencing the strains of downsizing, and may have reached the minimum limit of the number of astronauts required to support current ISS commitments. The uncertainty imposed by the transition from shuttle to the ISS, such as the inability to predict attrition rates, makes it more difficult to predict how many members of the Astronaut Corps NASA will require. The committee concluded that the best way to navigate this transition was for the Astronaut Office to maintain its existing Astronaut Corps staffing model, but to increase its margin from the current 25 percent.

To me, however, this data emphasizes again how little we know about the effects of weightlessness and space on the human body, and how important it is to do long term medical research in space. If humans are going to someday travel to Mars or the asteroids, we need to first make that same journey in orbit around the Earth, in a space station, to find out in advance what medical problems those astronauts might face, before they go.