The
science of nanotechnology could lead to radical improvements
for space exploration.
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July 27, 2005: When it comes to taking the next "giant
leap" in space exploration, NASA is thinking small --
really small.
In
laboratories around the country, NASA is supporting the burgeoning
science of nanotechnology. The basic idea is to learn to deal
with matter at the atomic scale -- to be able to control individual
atoms and molecules well enough to design molecule-size machines,
advanced electronics and "smart" materials.
If
visionaries are right, nanotechnology could lead to robots
you can hold on your fingertip, self-healing spacesuits, space
elevators and other fantastic devices. Some of these things
may take 20+ years to fully develop; others are taking shape
in the laboratory today.
Right:
Nanotechnology could provide the very high-strength, low-weight
fibers that would be needed to build the cable of a "space
elevator." Image by artist Pat Rawling. [More]
Thinking
small
Simply
making things smaller has its advantages. Imagine, for example,
if the Mars rovers Spirit and Opportunity could have been
made as small as a beetle, and could scurry over rocks and
gravel as a beetle can, sampling minerals and searching for
clues to the history of water on Mars. Hundreds or thousands
of these diminutive robots could have been sent in the same
capsules that carried the two desk-size rovers, enabling scientists
to explore much more of the planet's surface -- and increasing
the odds of stumbling across a fossilized Martian bacterium!
But
nanotech is about more than just shrinking things. When scientists
can deliberately order and structure matter at the molecular
level, amazing new properties sometimes emerge.
An
excellent example is that darling of the nanotech world, the
carbon nanotube. Carbon occurs naturally as graphite -- the
soft, black material often used in pencil leads -- and as
diamond. The only difference between the two is the arrangement
of the carbon atoms. When scientists arrange the same carbon
atoms into a "chicken wire" pattern and roll them
up into miniscule tubes only 10 atoms across, the resulting
"nanotubes" acquire some rather extraordinary traits.
Nanotubes:
- have
100 times the tensile strength of steel, but only 1/6 the
weight;
- are
40 times stronger than graphite fibers;
- conduct
electricity better than copper;
- can
be either conductors or semiconductors (like computer chips),
depending on the arrangement of atoms;
- and
are excellent conductors of heat.
Right:
A carbon nanotube. Copyright Prof. Vincent H. Crespi Department
of Physics Pennsylvania State University. [More]
Much
of current nanotechnology research worldwide focuses on these
nanotubes. Scientists have proposed using them for a wide
range of applications: in the high-strength, low-weight cable
needed for a space elevator; as molecular wires for nano-scale
electronics; embedded in microprocessors to help siphon off
heat; and as tiny rods and gears in nano-scale machines, just
to name a few.
Nanotubes figure prominently in research being done at the
NASA Ames Center for Nanotechnology (CNT). The center was
established in 1997 and now employs about 50 full-time researchers.
"[We]
try to focus on technologies that could yield useable products
within a few years to a decade," says CNT director Meyya
Meyyappan. "For example, we're looking at how nano-materials
could be used for advanced life support, DNA sequencers, ultra-powerful
computers, and tiny sensors for chemicals or even sensors
for cancer."
A
chemical sensor they developed using nanotubes is scheduled
to fly a demonstration mission into space aboard a Navy rocket
next year. This tiny sensor can detect as little as a few
parts per billion of specific chemicals--like toxic gases--making
it useful for both space exploration and homeland defense.
CNT has also developed a way to use nanotubes to cool the
microprocessors in personal computers, a major challenge as
CPUs get more and more powerful. This cooling technology has
been licensed to a Santa Clara, California, start-up called
Nanoconduction, and Intel has even expressed interest, Meyyappan
says.
Right:
An engineered DNA strand between metal atom contacts could
function as a molecular electronics device. Credit: NASA Ames
Center for Nanotechnology. [More]
Designing
the future
If
these near-term uses of nanotechnology seem impressive, the
long-term possibilities are truly mind-boggling.
The
NASA Institute for Advanced Concepts (NIAC), an independent,
NASA-funded organization located in Atlanta, Georgia, was
created to promote forward-looking research on radical space
technologies that will take 10 to 40 years to come to fruition.
For
example, one recent NIAC grant funded a feasibility study
of nanoscale manufacturing--in other words, using vast numbers
of microscopic molecular machines to produce any desired object
by assembling it atom by atom!
That
NIAC grant was awarded to Chris Phoenix of the Center for
Responsible Nanotechnology.
In
his 112 page report, Phoenix explains that such a "nanofactory"
could produce, say, spacecraft parts with atomic precision,
meaning that every atom within the object is placed exactly
where it belongs. The resulting part would be extremely strong,
and its shape could be within a single atom's width of the
ideal design. Ultra-smooth surfaces would need no polishing
or lubrication, and would suffer virtually no "wear and
tear" over time. Such high precision and reliability
of spacecraft parts are paramount when the lives of astronauts
are at stake.
Phoenix
sketched out some design ideas for a desktop nanofactory in
his report. He estimates, optimistically, that a working device
could be only 10 to 15 years away--maybe less if developed
rapidly in a massive "Nanhatten Project", as he
calls it.
Taking
a cue from biology, Constantinos Mavroidis, director of the
Computational Bionanorobotics Laboratory at Northeastern University
in Boston, is exploring an alternative approach to nanotech:
Rather
than starting from scratch, the concepts in Mavroidis's NIAC-funded
study employ pre-existing, functional molecular "machines"
that can be found in all living cells: DNA molecules, proteins,
enzymes, etc.
Right:
This bio-nanorobot envisioned by Constantinos Mavroidis and
colleagues resembles a living cell. [More]
Shaped
by evolution over millions of years, these biological molecules
are already very adept at manipulating matter at the molecular
scale -- which is why a plant can combine air, water, and
dirt and produce a juicy red strawberry, and a person's body
can convert last night's potato dinner into today's new red
blood cells. The rearranging of atoms that makes these feats
possible is performed by hundreds of specialized enzymes and
proteins, and DNA stores the code for making them.
Making
use of these "pre-made" molecular machines -- or
using them as starting points for new designs -- is a popular
approach to nanotechnology called "bio-nanotech."
"Why
reinvent the wheel?" Mavroidis says. "Nature has
given us all this great, highly refined nanotechnology inside
of living things, so why not use it -- and try to learn something
from it?"
The
specific uses of bio-nanotech that Mavroidis proposes in his
study are very futuristic. One idea involves draping a kind
of "spider's web" of hair-thin tubes packed with
bio-nanotech sensors across dozens of miles of terrain, as
a way to map the environment of some alien planet in great
detail. Another
concept he proposes is a "second skin" for astronauts
to wear under their spacesuits that would use bio-nanotech
to sense and respond to radiation penetrating the suit, and
to quickly seal over any cuts or punctures.
Above:
A sprawling web of nanosensors maps the terrain of an alien
planet. The cross-section at the top-right shows biologically
derived molecules (yellow and red) that would perform the
sensing and signaling functions. [More]
Futuristic?
Certainly. Possible? Maybe. Mavroidis admits that such technologies
are probably decades away, and that technology so far in the
future will probably be very different from what we imagine
now. Still, he says he believes it's important to start thinking
now about what nanotechnology might make possible many years
down the road.
Considering
that life itself is, in a sense, the ultimate example of nanotech,
the possibilities are exciting indeed.
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Author: Patrick L. Barry
| Editor: Dr. Tony
Phillips | Credit: Science@NASA
|