杏吧原创

SOME space engineers design rockets. Others work on navigation controls, fuel
systems or how best to squeeze a satellite into the space shuttle鈥檚 cargo bay.
But NASA engineer Joe Kosmo has a more aesthetic occupation. It鈥檚 his job to
design spacesuits. After thirty years working on classics like the silver
Mercury suit and the ultra-accessorised shuttle outfit, Kosmo is planning his
next collection. And this time he鈥檚 thinking Red. Specifically, what will the
well-dressed astronaut be wearing on Mars?

鈥淢ars is one place that everybody always figured astronauts would visit,鈥�
Kosmo says. 鈥淚 think we thought we鈥檇 be there by now.鈥� Although NASA has not
committed itself to a crewed mission to the planet, there is unofficial talk of
a launch as early as 2020. Since it can take up to ten years for a spacesuit to
be 鈥渇light qualified鈥�, that means delivering a prototype suit by 2010. And while
the agency hasn鈥檛 yet begun to seriously fund any design projects, focusing
instead on erecting the International Space Station, it is quietly starting the
long and difficult process of selecting a spacesuit to go to Mars.

So what is NASA looking for? 鈥淢ars poses some particular problems that we
haven鈥檛 really had to address before,鈥� Kosmo says. Among them is how to live and
work for months, maybe years, on a planet whose atmospheric pressure is less
than a hundredth that on Earth, whose temperature varies wildly and whose
surface is roiled by abrasive winds that frequently exceed 150 kilometres an
hour. NASA believes it has the technology to build a suit that could sustain
life in such an environment, but not one that would survive the rigours of an
extended working visit鈥攖he only kind possible given the current logistics
of space travel. As a result, all sorts of designs are being considered, from
body-hugging leotards to robotic trousers鈥攅ven giant 鈥渉amster balls鈥�.

But whatever the final suit looks like, it鈥檚 likely to use the best bits of
spacesuits from the past. The earliest aerospace pressure suits were developed
in the early 1930s for pioneering aviators such as Wiley Post, who set a
high-altitude record of almost 15 kilometres in 1934. Post鈥檚 pressure
suit鈥攁 crude rubber balloon shaped rather like the Michelin Man鈥攚as
difficult to put on and even more difficult to move about in. The internal air
pressure made bending his arms or legs almost impossible. Still, it validated
the idea of wearing a pressurised body balloon.

The Mercury mission astronauts of the early 1960s wore something similar: a
modified military flight suit consisting of an inner layer of airtight rubbery
neoprene-coated fabric and an outer layer of aluminised nylon, which gave them
their famously futuristic silver look. These suits were intended only as a
backup if the capsules lost air pressure, which never happened. They couldn鈥檛 be
worn outside because they lacked protection against cosmic radiation and
micrometeoroids鈥� fast-moving, hole-punching bits of space debris. Despite
their simplicity, they remained uncomfortable and constraining. Subsequent
Gemini mission suits improved upon mobility, but new layers of specialised
fabric, added for warmth and strength, made them just as irksome to wear.

The next generation of suits was even more unwieldy, and with good reason:
they had to sustain their occupants on the surface of the Moon. The Apollo suits
were elaborate, custom-made for each astronaut with as many as 24 layers of
different materials, including Teflon, aluminised Mylar and neoprene. The suits
also had life-support backpacks that maintained internal air pressure and
provided pure oxygen for breathing. They also supplied water for cooling and
drinking, plus batteries to power communications and other equipment. Each suit
weighed about 80 kilograms on Earth. In the Moon鈥檚 lesser gravity (one-sixth
that of Earth), they weighed a more manageable 14 kilograms. Still, wearing one
was no day at the beach. 鈥淭he astronauts could barely move,鈥� says Hubert
Vykukal, a recently retired NASA engineer who helped design the suits. 鈥淩emember
those pictures of them skipping around on the lunar surface? That was because
they had such poor lower-torso mobility that bouncing was about the only way
they could get around.鈥�

After the Moon came the shuttle programme and a new set of problems, not
least that the astronauts had to work outside the craft in the near vacuum of
space. Shuttle suits are big, bulky and complicated鈥攔ather like a personal
spaceship鈥攁nd they are also heavy, weighing 135 kilograms each on Earth.
Of course, in the zero gravity of orbit this is largely irrelevant, and while
mobility is an issue, it is less important than on the Moon because shuttle
astronauts don鈥檛 have to walk. 鈥淢obility in space generally involves upper-torso
movement, being able to pull yourself from station to station,鈥� says Kosmo.
鈥淵our legs are just there for the ride.鈥�

It will be very different on Mars. First, there鈥檚 the problem of getting
there. The flight time will be around six months鈥攏early all of it spent in
low gravity. Weightlessness over a period of time like that wreaks havoc upon
the body. Muscles atrophy, bones demineralise and body mass plummets. 鈥淣obody
has the technology or science to eliminate the physical degradation of
zero-gravity conditions,鈥� says Vykukal. 鈥淭he Mir cosmonauts, who spent months in
space, had very rigorous exercise programmes to counteract physical decay and
they still came back in bad shape. They looked similar to somebody who had been
bedridden for a month.鈥�

Even if scientists and engineers can figure out how to get people to Mars in
relatively good health鈥攑ossibly by generating artificial gravity in the
spacecraft, combined with drugs and physical training鈥攖he astronauts will
still experience a sinking feeling when they arrive on the planet鈥檚 surface. A
70-kilogram person on Earth weighs just over 26 kilograms on Mars. That doesn鈥檛
sound like much, but it鈥檚 a weighty problem for engineers who must build a
spacesuit light enough for a weakened astronaut to wear comfortably for hours at
a time. 鈥淭he shuttle suits would weigh more than 100 pounds [45 kilograms] on
Mars, which is obviously way too heavy to lug around for very long,鈥� says
Kosmo.

More problematic than weight, however, may be what鈥檚 happening around the
astronauts. On Earth, atmospheric pressure at sea level is about 101
kilopascals, and this is essential to survival. It makes it possible to breathe,
and it keeps the fluid inside our bodies liquid and flowing. Expose someone to
very low pressures and unpleasant things start to happen. At an altitude of 19
kilometres鈥攖he threshold of space鈥攁ir pressure is so low that
nitrogen evaporates out of body tissues and the lungs fill with water vapour. A
human breathing ambient air at this altitude would black out in seconds and die
soon afterwards. 鈥淚 remember hearing a NASA astronaut talk about an experiment
in which he was exposed to a sudden, temporary loss of pressure,鈥� says Dave
Akin, a professor at the University of Maryland鈥檚 Space System Laboratory near
Washington DC. 鈥淗e said the first thing he thought was, 鈥淥h 鈥斺��!鈥�
Then he had this interesting feeling of saliva boiling on his tongue. Then he
passed out.鈥�

A visit to Mars would be like that experiment on a planetary scale. Though
half the diameter of Earth, Mars has just one-tenth its mass and three-eighths
its gravitational pull. As a result, the Martian atmosphere鈥攎ostly carbon
dioxide with dashes of nitrogen, oxygen, carbon monoxide, argon, neon, krypton
and xenon鈥攊s exceedingly thin. Atmospheric pressure is just 690 pascals,
so wearing a pressurised suit is an absolute must.

Rock, sand and silt

In addition, the Martian atmosphere is extremely dusty. Despite new
revelations that liquid water may have flowed there in the recent geological
past, the planet鈥檚 surface is almost entirely an arid desert of rock, sand and
silt. And the silt isn鈥檛 so much on the Martian surface as above it, swirling
throughout the atmosphere in constant, powerful storms that can last for weeks.
For spacesuit designers, all that airborne dirt conjures up the twin terrors of
abrasion and clogging. 鈥淢oon dust was pretty abrasive,鈥� says Kosmo. 鈥淚t was
sharp, glassy, basaltic and it really thrashed the Apollo suits, even after just
a few uses. Mars dust is more clay-like, earthy. It鈥檚 not as sharp, but it鈥檚
finer and would probably cause more wear on bearings and linkages.鈥�

And as if all that wasn鈥檛 enough to contend with, there鈥檚 also the issue of
climate. Equatorial temperatures on Mars are a comparatively balmy 10 to 16掳C
during the day but plunge to 鈭�100掳C or lower at night. Staying
snug and cosy is especially tricky because the temperature gradient can be steep
and sharply defined, says Dava Newman, an aeronautics researcher at the
Massachusetts Institute of Technology who is working on the health problems
posed by Mars exploration. 鈥淚t can be 20 degrees colder at the head than it is
at the knees,鈥� she says. 鈥淭hat obviously makes it more challenging to design a
heated spacesuit that鈥檚 completely comfortable.鈥�

As yet there is no one suit that can meet all of the challenges astronauts
will face on the Red Planet. 鈥淲e know how to make a suit you could live in on
Mars, but not one that can be effectively manipulated to do jobs there,鈥� says
Phil West, a spokesman for NASA. 鈥淪uch a suit would have to have extremely
flexible joints and mix-and-match parts for easy replacement. It would be
relatively lightweight, maybe 30 to 40 pounds [14-18 kilograms], but extremely
reliable because it would be used for dozens of missions. That suit doesn鈥檛
别虫颈蝉迟.鈥�

But it may be possible to put together an outfit from NASA鈥檚 existing
wardrobe. Kosmo says that the right technologies and materials exist and that
it鈥檚 just a matter of thinking exactly how the suit would be used and what its
occupant will be doing. 鈥淭he first astronauts on Mars are going to behave like
geologists,鈥� he says. 鈥淭hey鈥檒l be looking for evidence of life, of water.
They鈥檒l be poking around, getting down on their hands and knees to look at rocks
or drill for samples. They鈥檙e going to need a really robust suit.鈥� Rather than
operate inside a bulky pressure suit, as in the Apollo missions, Kosmo envisions
Martian astronauts wearing a stripped-down model and relying upon robotic
assistants to carry life support supplies and exploratory equipment. 鈥淎stronauts
on Mars may work outside for a few hours then go inside a habitat to switch
packs or recharge their equipment,鈥� he says. 鈥淥r maybe robotic rovers will do
most of the initial surveying and rudimentary work, while astronauts are
acclimating themselves to Mars. Then humans will go do the science.鈥�

Newman calls this the 鈥渓ittle red wagon鈥� scenario, after a toy that millions
of American children use to haul their possessions around after them. A simple,
light suit would provide basic life support and protection from hazards like
radiation and sharp objects, but everything else鈥攖ools for exploring,
additional power and supplies鈥攚ould be pulled along in a wagon, or perhaps
driven as a kind of exploratory buggy.

The best candidate for a lightweight design, Newman says, is a mechanical
counter-pressure suit that physically squeezes the body to protect it against
depressurisation. This concept was conceived in the 1970s but failed to
materialise due to a lack of suitably stretchy materials. Newman says that the
right materials are either available now or will be soon, and that it鈥檚 time to
revive the concept.

A skin-tight suit would eliminate the need for complicated joints, which are
vulnerable to dust contamination, she says. Flexibility would come from the
astronaut鈥檚 own wrists, elbows, knees and ankles. The suit itself would also
contain electronic circuitry to warm or cool different parts of the body.
Impregnated wiring would expand or contract within specialised fabrics to aid
mobility or boost an astronaut鈥檚 strength. Newman鈥檚 lab at MIT is developing an
elbow joint that incorporates shape memory alloys, sometimes called muscle
wires, to provide assistance to the astronauts once on Mars. These could be
modified on the journey to turn the joint into a kind of mini-elbow gym.

Lightweight fabrics

Other researchers are pushing ahead with their own ideas. Delaware-based
company ILC Dover, a long-time manufacturer of NASA space clothing (its postal
address is One Moonwalker Road), has spent five years funding and developing a
prototype suit for Mars. The so-called I-suit is designed to operate at a lower
internal pressure than shuttle suits, making it quicker to put on because
pressurisation doesn鈥檛 take as long, and easier to move about in because there
is less resistance to bending or moving limbs. The suit also employs advanced
composite fibres that are lighter and stronger than most materials used today,
reducing the need for bulky, armour-like materials such as fibreglass and
Kevlar.

鈥淲e鈥檝e still got to make the suit weigh less,鈥� says ILC Dover official Joe
Spampinato. 鈥淎nd there are issues like dust protection,鈥� which he says might be
best resolved by using overalls that could be discarded after each foray
outdoors. But much else about the suit remains tentative and proprietary and the
company won鈥檛 describe it in great detail.

The I-suit is one of three that NASA is testing at the Johnson Space Center
in Houston, Texas, and at field locations in Arizona. The others are the H-1, a
hybrid made from existing NASA components, and the all-fabric D-suit designed by
the David Clark Company of Worcester, Massachusetts. This is based on the
company鈥檚 Advanced Crew Escape Suit, the orange costume that shuttle astronauts
wear for launch and re-entry, and is designed to be as light and mobile as
possible.

None of these suits, however, is close to a final version. 鈥淭hey are
technology prototypes,鈥� Kosmo says. 鈥淲e鈥檙e testing them for mobility, strength
and so on. It鈥檚 the beginning of a technology selection process that can last
years. We鈥檒l see what works best in each suit, then combine those features in
the next test series.鈥�

The three suits under investigation represent variations on the traditional
spacesuit. They鈥檙e not so much new ideas as revivals of existing styles. But
some researchers say the Mars suit should be cut from new cloth鈥攊f cloth
is even used. 鈥淓verybody is used to spacesuits looking big and clunky, but we
need to be much more creative,鈥� says Newman. 鈥淚 don鈥檛 think we should constrain
ourselves into thinking a Mars suit has to look anything like the Apollo or
shuttle suits.鈥�

Newman says there are a number of possibilities, from counter-pressure suits
to robotic walkers, as in Wallace and Gromit鈥檚 The Wrong Trousers. Then
there鈥檚 the 鈥減od concept鈥�, also known as man-in-a-can. 鈥淭his is where you live
inside the spacesuit,鈥� she says. 鈥淧erhaps it鈥檚 spherical for rolling
locomotion鈥攊magine a giant, transparent ball like those used by pet
hamsters鈥攐r it has wheels itself.鈥�

Kosmo thinks these ideas have their merits, but are unlikely to feature in
the first crewed mission. 鈥淚 think there are some really interesting ideas out
there,鈥� he says. 鈥淎 counter-pressure suit may ultimately be the way to go, but
nobody so far has proved it can work. With a counter-pressure suit, you鈥檝e got
to maintain constant, uniform pressure across the body. There can be no voids
where the suit doesn鈥檛 make contact, or body fluids start to pool there.
Something like a robotic walker would be really cool, but every idea comes with
its own set of problems. How do you build it? What would it weigh? What would it
cost? When you鈥檙e building a spacesuit, you have to ask what will it be used for
and what will it solve.鈥�

So, like an expensive Savile Row suit, some things about the first Martian
suit will echo the classic cuts of Mercury and Apollo. For one thing, it will
stay white, a colour that best reflects light and heat, and it will come with a
helmet and gloves. But in other respects it will be new. Robert Zubrin,
president of The Mars Society, thinks the first Mars suit will be modelled as
closely as possible on the clothes we wear on Earth. It will be pressurised, but
at the lowest safe level. It will be light, easy to wear and easier to maintain.
Above all, it will be comfy鈥攁 sentiment Newman shares. 鈥淚f you could get
up in the morning in your Martian habitat and dress in a spacesuit that is as
comfortable as the daily clothing we currently wear, that would be ideal,鈥� she
says.