When my youngest child developed an interest in astronomy, his grandmother feared he might some day become an astronaut. As it turned out, he never had any intention of venturing into space, but his grandmother was right to worry. Being an astronaut comes with serious occupational hazards.
So far, 18 of the 430 humans who have flown in space have died in flight, 14 on two shuttle missions and four on two Soyuz flights, yielding a fatality rate of just over 4%. And these figures do not include the 11 people who lost their lives during training for space flights. So yes, it’s a dangerous business, but there are other risks too.
The human body is adapted for living on Earth, and conditions during spaceflight are very different. While a spacesuit and the spacecraft itself help protect the astronaut from radiation, extreme temperatures, lack of oxygen and the vacuum of space, many other hazards remain. One of these involves the effects of microgravity or weightlessness. With humans now spending 6 months to a year on the International Space Station (ISS), this is becoming an increasing concern. While astronauts may feel on top of the world, effortlessly lifting heavy objects in space, their superpowers vanish on return to Earth. At a May 16th press conference, three days after touchdown, astronaut Chris Hadfield, had this to say: “Right after I landed, I could feel the weight of my lips and tongue and I had to change how I was talking. I hadn’t realized that I learned to talk with a weightless tongue.”
Here on Earth our bodies have evolved to respond to the pull of gravity, to sense which side is “up” and which is “down.” In space these signals are absent. A temporary, though unpleasant effect of microgravity, experienced by about 45% of space travelers during flight, is space sickness. Related to motion sickness, it occurs as the vestibular system of the inner ear attempts to adapt to weightlessness, causing nausea, vomiting, vertigo, headaches and other symptoms. This rarely lasts more than three days.
Other effects of microgravity, such as loss of bone and muscle mass, are of more concern. In addition, humans consist mostly of fluids that, under the influence of microgravity, are redistributed towards the upper half of the body. This can cause balance disorders, loss of taste and smell, and vision problems from changes in eyeball pressure. In microgravity the cardiovascular system slows down and aerobic capacity is reduced.
To help prevent some of these adverse effects, the International Space Station is equipped with a stationary bicycle, two treadmills and the aRED (advanced Resistive Exercise Device). These facilitate weight-bearing and weightlifting exercises that add muscle but unfortunately do nothing to help bone density. To address this latter issue, astronauts exposed to long periods of weightlessness on the ISS wear pants with elastic bands attached between the waist and the cuffs to compress the leg bones. In addition, their health is closely monitored from Earth, and they are subjected to extensive medical tests on their return.
A major concern for space travel is exposure to the damaging effects of radiation. High levels can cause cancer and damage the immune system. There is also a higher than normal incidence of cataracts amongst astronauts. Here on Earth we are protected from high levels of radiation from space by our atmosphere and by the magnetosphere, the magnetic field that surrounds our planet. Astronauts on the International Space Station are partially protected by Earth’s magnetic field which deflects the solar wind around Earth and the ISS, but their annual radiation exposure is still about 10 times that experienced on Earth. In addition, solar flares are powerful enough to penetrate the magnetosphere and can pose a serious danger to the crew. Future interplanetary missions, well beyond Earth’s protective magnetosphere, would expose the crew to potentially lethal levels of radiation, and for much longer periods of time. A sobering thought for those contemplating a trip to Mars.
This month, join the Springfield Stars Club on Tuesday, September 24th at 7:30pm at the Springfield Science Museum for a slide show and account of the club’s recent private tour of Harvard University’s Collection of Historical Scientific Instruments. The meeting will also include a report back on the summer’s star parties – Stellafane, The Conjunction, Arunah Hill Days and stargazing at the Wilco Music and Arts Festival held at Mass MoCA. Refreshments will be served, and the public is welcome free of charge.
Copyright © Amanda Jermyn