On November 2nd 2000 the first crew arrived at the fledgling International Space Station. In doing so they began a 16-year human presence in Earth orbit which continues to this day. While this is a massive achievement for humanity, we shouldn’t be fooled into thinking that the many difficulties of long-term human space travel have been overcome. Space is an incredibly hostile environment and has a long list of detrimental effects on the body, ranging from the inconvenient to the potentially deadly.
This first of effect of space travel is hard to miss. Take a look at the photo on the left showing British astronaut Tim Peake in orbit on the International Space Station (ISS). Then compare it to the photo on the right showing him down on Earth just days earlier. Obviously, his face looks much rounder and more swollen on the left, and this isn’t unusual in astronauts.
Tim Peake on the International Space Station (left) and a few days earlier on Earth (right)
Image Credit: Wikimedia
When a human reaches orbit and feels microgravity (NASA’s technical term for weightlessness) for the first time, the fluids that fill their bodies change their distribution dramatically. These fluids, no longer held down by gravity, rush into the upper body causing facial swelling, bulging veins and congestion of the sinuses.
The effect of this change is like a bad head cold; it’s uncomfortable and messes with the astronaut’s senses of taste and smell. While no one loses sleep over an astronaut temporarily losing their sense of smell, the dulling of taste can provide a challenge to chefs preparing food to be eaten in orbit. To compensate, cooks make space food extra spicy, so astronauts don’t have to suffer bland food for their six month stays on the ISS.
Space sickness (or Space Adaptation Syndrome) is another side-effect of orbital travel that’s hard to ignore – for the astronauts at least. As their vestibular system (the fluids in their inner ear which tell them which way is up) struggles to adjust to a world where ‘up’ and ‘down’ don’t mean much, around 50% of astronauts experience nausea and disorientation.
The symptoms of space sickness don’t last too long though – after a couple of days in orbit the symptoms of space sickness subside as the vestibular system of the space traveller adjusts to its new surroundings. Unfortunately, for many astronauts (including Britain’s own Tim Peake) space sickness returns with a vengeance when they land back on Earth – their vestibular system has adapted to weightlessness so completely that the return of regular gravity is dizzying.
The weightlessness of Earth orbit also has some more serious effects on the human body. When an astronaut spends time in space, they begin to lose huge amounts of mass from their muscles and bones. The reason behind both is simple: use it or lose it.
When standing on Earth our legs and spines are constantly working to keep us upright. With no weight to support in orbit, the body starts to break down these bones, washing their vital calcium content away in the bloodstream. This leads to bone loss of up to 1% for every month spent in space.
Muscle loss in microgravity can be even more dramatic, with up to 20% loss from just one week in orbit – especially from the so-called ‘antigravity muscles’ of the legs and back which keep us upright here on Earth.
Needless to say, this is a huge problem for astronauts. Not only do they need their bones and muscles for strenuous activities in space, studies have shown that while muscle mass recovers relatively quickly back on Earth, bone density never completely returns to normal.
To try to combat this, the ISS is equipped with an artificial gravity treadmill, in which astronauts are pulled onto a running surface by straps. This not only gets their muscles working but puts their bones under compression, encouraging them to retain their precious calcium.
Astronaut Frank De Winne working out on the same artificial gravity treadmill where Tim Peake famously ran the London Marathon in space
Image Credit: Wikimedia
Another substantial problem for space travellers is the impact weightless has on their eyesight. 80% of astronauts are thought to suffer from Visual Impairment Intracranial Pressure syndrome, a condition caused by space travel which does huge damage to the eyes.
Brain scans of returning astronauts show eyes that have been compressed top-to-bottom, pushing the retina backwards into the brain. NASA scientists believe this is caused by the increased pressure in the skull when bodily fluids shift upwards in microgravity. As yet, this worrying syndrome remains unsolved and untreated.
Finally, not all problems in space emerge from the absence of gravity. Also missing in space is the protective layer of atmosphere that surrounds the Earth. Along with providing us air to breathe, our atmosphere also shields us from cosmic rays – dangerous radiation from beyond the solar system that pummels our planet day and night. During cosmic events called solar storms the Sun throws out radiation too, adding to the barrage of incoming rays.
Out in space, astronauts aren’t protected from any of this radiation; despite significant shielding on the walls of the ISS, projections have shown that astronauts living there could reach their lifetime safe limits for exposure in just 18 months. This is bad news for those planning missions to Mars, as even a brief trip to Mars would take over a year.
Scientists must find shielding methods that are both light enough to take to Mars and strong enough to keep astronauts safe, even during solar storms, or risk causing them serious health problems – mainly in the form of cancers – years down the line.
So there’s still a long way to go until long-term interplanetary trips are feasible for the fragile human body; space remains a dangerous and taxing environment for the people who travel there. Nonetheless, scientists across the world are working to change this, and we at pH7 wish them the best of luck.