STS-132 crew members, from left, Bristih-born, U.S. astronaut Piers Sellers, mission specialist Stephen Bowen, pilot Dominic Antonelli, commander Ken Ham, and mission specialists Garrett Reisman and Michael Good, pose for a photo after the space shuttle Atlantis landed on Kennedy Space Center's runway 33 Wednesday, May 26, 2010, in Cape Canaveral, Fla. (AP Photo/Joe Skipper, Pool)
Life as an astronaut involves risks. But who knew those risks come even from wearing space suit gloves?
A new study found that fingernail injury is a common problem with astronaut gloves, and that spaceflyers with larger hands are more likely to be hurt by their gloves.
Astronaut gloves are designed to protect the hand from the vacuum of space and to resist puncturing from bits of debris that might impact while an astronaut is working on a spacewalk. Glove design has had to sacrifice some flexibility for strength.
The injuries most often result from tight gloves that cut off blood flow to the fingertips, the study found. But sustained pressure at the fingertips can cause fingernails to break or, in extreme cases, detach from their nailbeds or fall off entirely.
"It's pretty challenging to design gloves and the space suit to keep someone alive in the extreme environment of space," said study co-author Dava Newman, a professor of astronautics at MIT.
"It shows you there's still room for improvement in future designs," she told SPACE.com.
The study looked at data from 232 NASA astronauts, and found that 22 of them (about 10 percent) incurred "fingernail trauma" while wearing space suit gloves.
The results will be detailed in the October issue of the journal Aviation, Space, and Environmental Medicine.
The researchers analyzed 22 different measurements of the hand, such as hand circumference and finger-to-hand size ratio. They found a significant correlation between hand circumference and injury rates.
In particular, male astronauts with a hand circumference larger than 9 inches (23 cm) have a 19.6 percent probability of fingernail injury, while crewmembers with hands smaller than that have only a 5.6 percent chance of injury, the study found.
The larger the hand, the more restrictive the gloves seem to be. In particular, the current gloves offer very limited movement in the hand's metacarpal joint, which allows the hand to bend the fingers over the palm.
"The gloves are preventing the natural movement," Newman said. "It does suggest for advanced glove design, we really want to pay more attention to that metacarpal joint. We really want to give the hand as much flexibility as you can get."