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Researchers discuss how to keep astronauts
safe and healthy during long trips through the solar system.
by Karen Miller
Travelling can be tough on the body.
Think about driving all the way from, say, Washington to Wisconsin,
or London to Scotland. By the time you ease yourself from behind
the wheel, your back hurts, your eyes ache, your hands are cramped.
And the farther you go, the more your body suffers. If you fly to
France or Australia, you're hit by radiation. If you visit the space
station, you lose gravity.
Now imagine you're heading for Mars:
low gravity, radiation exposure, a six month trip spanning millions
of kilometres. Without some kind of "counter-measures" to protect
you, your muscles will shrivel, your bones could weaken, your genes
might be damaged and confused. When you arrive, you might find it
hard to even get out of your spaceship without stumbling and hurting
yourself.
Even subtler changes are beginning to be discovered. Here on
Earth, we have no trouble sensing the position of our limbs: if
you decide to lift your arm, you know where it is, and how much
farther you need to move it to get it where you want it to be. But
in space, this "proprioceptive" ability doesn't seem to work as
well. And there may be other problems: slower wound healing and
immune system weaknesses, for example.
Right now, the chief countermeasure
recommended by space doctors is simply exercise. Astronauts on the
International Space Station work out for about two hours a day,
using treadmills, exercise bikes, and an IRED - a device specially
developed to allow astronauts to do resistive or strength training.
Medications, too, may help with some problems: biphosphonates, for
example, used on Earth to slow the rate of bone loss in osteoporosis
patients may prove useful for astronauts, too.
These countermeasures seem to work
well enough for short stints in space. For long-term exploration,
an entirely different approach might work better: artificial gravity.
"It's very compelling as a solution,"
says Williams.
In
theory, providing artificial gravity is easy. Ordinary laboratory
centrifuges do it all the time. When they spin, their contents are
pressed outward away from the axis of rotation. It's a force that
feels like gravity.
Supernovas,
like the one that created this
nebula are potent sources of galactic cosmic rays.
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Rotating an entire space ship, however,
can be both costly and complex. That's why researchers at the NASA
Ames Research Centre have been developing a small, human-powered
centrifuge. It's essentially an exercise track, in which an astronaut
pedals a bike up and around a 360 degree circle.
By pedalling the bike around the track, explains
Williams, you turn yourself into a human centrifuge. "Depending
on the speed at which you're going, and the size of track, you'll
experience a pseudo-force ... a gravity substitute."
This kind of human-powered device would provide
an intermittent exposure to artificial gravity. Researchers must
still figure out how much of this pseudo-gravity is needed to keep
astronauts fit. Furthermore, the force created by such a device
would feel stronger at the astronauts' feet than at their heads!
But it might be enough like home to counteract the effects of zero-g.
Bicycles won't solve everything, though, because
weightlessness is only one problem.
Radiation is another. Right now, the countermeasure
for radiation is limiting astronaut exposure - which means limiting
the amount of time they're allowed to be in space. But on a long-term
mission of exploration, the astronauts will have to be in space
for months on end, and, importantly, the type of radiation in deep
space is more damaging than the kind in low earth orbit.
An exploration class spaceship will have to include
shielding that can absorb cosmic rays.
The best material to block high-energy radiation
is hydrogen, explains Frank Cucinotta, astronaut
radiation health officer and manager for Space Radiation Health
Research at the Johnson Space Centre". But you can't make a shield
out of pure hydrogen, so we look for materials than have a high
hydrogen content, like polyethylene, a common plastic, which
is 1 carbon and 2 hydrogen's." Water, he says, with one oxygen and
two hydrogen's., would be almost as good, but it's awfully heavy
and expensive to launch.
To completely block radiation, hydrogen-rich shields
would need to be a couple of meters thick - impractical, because
of the weight and volume. But, oddly, 30 to 35 percent of the radiation
can be blocked by shields just five to seven centimetres thick.
That, suggests Cucinotta, might be the most efficient choice.
Astronauts would still need to cope with the 70
percent of the radiation that's getting through the shields. So
Cucinotta and his colleagues are looking at other solutions, like
medication.
NASA-funded scientists are crafting microscopic vessels that
can venture into the human body and repair problems–one
cell at a time.
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Antioxidants like vitamins C and A
can help by sopping up radiation-produced particles before they
can do any harm. NASA scientists are also looking for ways to help
the body after the damage has been done. One, for example,
may have found a way to instruct a damaged, abnormal cell to destroy
itself. Another researcher is exploring the cell cycle: as a cell
divides, it pauses occasionally, to check its genes for any kind
of damage and to repair errors. With pharmaceuticals that lengthen
this part of the cycle, researchers believe they can give the cell
more of a chance to fix its own problems.
Even if we could prevent the damage
caused by radiation and weightlessness, that would still be only
part of what's needed to explore Mars and beyond. "The other element,"
says Dave Williams, "is the diagnosis and treatment of disease."
Because, as healthy and fit as astronauts are, the possibility exists
that some medical problem could arise during long missions. Astronauts
will need to treat any such illness or accident by themselves, using
only the tools they've carried with them.
This means developing technologies
that are as smart and as capable as possible. It means developing
expert systems that can work effectively regardless of the training
of the people who are operating them. (A doctor would be a key part
of any long-term mission, of course, but what if the doctor got
sick or disabled? Other members of the crew would have to help.)
Millions of miles from the nearest
hospital, space doctors will need advanced medical technology: miniaturized
devices to perform minimally invasive surgeries; robot helpers with
super-steady hands; smart medical systems that can diagnose, and
perhaps even treat, illnesses; and telemedicine capabilities that
will allow the ship's chief medical officer to consult with experts
back on Earth.
In fact, many of these devices are
already being developed on Earth.
Accidents
happen. In this painting by space artist Pat Rawlings, an astronaut has fallen
and fractured his right femur. Responding to this situation
on a "medivac" hopper, two other lunar base crew members
employ a portable CAT-scan device, a holographic display,
and helmet-mounted heads-up displays to determine the severity
of the injury.
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External defibrillators
are a good example, says Jim Logan, manager for the Medical Informatics
and Health Care Systems Office at the Johnson Space CentreThese
devices, which use electrical shocks to restart a patient's heart,
are good examples of a smart medical system. "The expertise," says
Logan, "is all local, resident in the machine." The device itself
can decide whether it's been hooked up correctly, whether the patient
needs to be defibrillated, and if it decides that the answer is
yes, it just goes ahead and provides the treatment. That kind of
capability, which contains all its expertise in a tiny, lightweight,
easy-to-use package, is a key part of what's needed to provide clinical
care on a long-term exploration mission
Robotically assisted surgery might
also play a role. In space, minimally invasive surgery will be important.
You don't want to make large incisions: wounds may be slower to
heal and fluids like blood harder to control. By using robots, which
can make steadier, more even movements that a human hand, surgeons
can make smaller, finer incisions than they could on their own.
Telemedicine will be a another key
tool, and that too is already being explored. "We have at JSC a
teledermatology clinic based on the principles of space flight medicine,"
says Williams. "If you come into the clinic with a skin rash, we
take a high-resolution digital image of the rash and send it to
an expert over the Internet. The dermatologist gives a diagnosis,
and recommends treatment." The patient doesn't need to be seen in
person. For all the doctor knows, they could be on Mars.
Possible technologies abound. Consider
a device that could produce medicines from stored substrates - only
when the medicines were needed. Long term exploration missions are
likely to exceed the life of many pharmaceuticals, explains Logan.
But if you could produce pharmaceuticals as you needed them, he
says, then shelf life might be much less problematic.
more
This prototype
Robot Assisted Microsurgery device was developed by roboticists
at JPL and Microdexterity Systems, Inc.
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This so-far hypothetical device would
solve another problem, too. "Say someone invented a new antibiotic
after you had already left Earth. You can't upload [pills], but
you can upload software. So if you had the capability of
manufacturing your medications on the fly, you could simply upload
the structure of the new drug, and make it right there."
The technologies needed for long term
exploration of the solar system are the same that are needed to
provide quality medical care to an isolated rural community or to
treat soldiers in the field. Many of these capabilities already
exist, at least in some early form. But researchers want to make
them smaller, lighter, more power-efficient, smarter, and more effective.
"Our goal," says Williams, "is to extend
the distance that humans can go in space, and to increase the time
that they can stay there." Space is a tremendous driver for the
development of new technologies, he believes. "And the technologies
that we develop to move beyond low earth orbit are truly going to
change the way we practice medicine here on Earth."
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