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Listen to this story via streaming audio, a downloadable file, or get help. Sept. 16, 2002: "What I'm really looking for," you say to the salesman, "is a car that goes at least 10,000 miles between fill-ups, repairs itself automatically, cruises at 500 mph, and weighs only a few hundred pounds." As he stands there wide-eyed, you add, "Oh yeah, and I can only spend about a quarter of what these other cars cost." Above: A next-generation minivan? Advanced materials will be essential for making dramatically improved spacecraft possible. [more] A request like this is sure to get you laughed off the new-car
lot. But in many ways, this dream car is a metaphor for the space
vehicles we'll need to expand our exploration of the solar system
in the decades to come. These new spacecraft will need to be
faster, lighter, cheaper, more reliable, more durable, and more
versatile, all at the same time.
Such a revolution is happening right now. Three of the fastest-growing sciences of our day--biotech, nanotech, and information technology--are converging to give scientists unprecedented control of matter on the molecular scale. Emerging from this intellectual gold-rush is a new class of materials with astounding properties that sound more at home in a science fiction novel than on the laboratory workbench. Imagine, for example, a substance with 100 times the strength of steel, yet only 1/6 the weight; materials that instantly heal themselves when punctured; surfaces that can "feel" the forces pressing on them; wires and electronics as tiny as molecules; structural materials that also generate and store electricity; and liquids that can instantly switch to solid and back again at will. All of these materials exist today ... and more are on the way. With such mind-boggling materials at hand, building the better spacecraft starts to look not so far fetched after all. Weight equals
money Right: This fully-loaded Saturn V moon rocket weighed 6.2 million pounds. It was heavy and expensive to launch. [more] The challenge is to trim weight while increasing safety,
reliability, and functionality. Just leaving parts out won't
do. Nanotubes were only discovered in 1991, but already the intense
interest in the scientific community has advanced our ability
to create and use nanotubes tremendously. Only 2 to 3 years ago,
the longest nanotubes that had been made were about 1000 nanometers
long (1 micron). Today, scientists are able to grow tubes as
long as 200 million nanometers (20 cm). Bushnell notes that there
are at least 56 labs around the world working to mass produce
these tiny tubes. Beyond merely being strong, nanotubes will likely be important
for another part of the spacecraft weight-loss plan: materials
that can serve more than just one function. Spacecraft skins Humans can feel even the slightest pinprick anywhere on their bodies. It's an amazing bit of self-monitoring--possible because your skin contains millions of microscopic nerve endings as well as nerves to carry those signals to your brain. Likewise, materials that make up critical systems in a spaceship
could be embedded with nanometer-scale sensors that constantly
monitor the materials' condition. If some part is starting to
fail--that is, it "feels bad"--these sensors could
alert the central computer before tragedy strikes. Above: This piezoelectric material, developed at
NASA's Langley Research Center (LaRC), can "feel" deformations
such as bending or surface pressure, producing a small voltage
in response that can act as a signal for a central computer.
Image courtesy NASA's Morphing Project at LaRC. Right: A solar flare blasts energetic radiation into space. [more] Scientists are still searching for a good solution. The trick is to provide adequate shielding without adding lots of extra weight to the spacecraft. Some lightweight radiation-shielding materials are currently being tested in an experiment called MISSE onboard the International Space Station. But these alone won't be enough. The real bad guy is Galactic Cosmic Radiation (GCR) produced
in distant supernova explosions. It consists, in part, of very
heavy positive ions--such as iron nuclei--zipping along at great
speed. The combination of high mass and high speed makes these
little atomic "cannon balls" very destructive. When
they pierce through the cells in people's bodies, they can smash
apart DNA, leading to illness and even cancer. Ironically, light elements like hydrogen and helium are the best defense against these GCR brutes, because collisions with them produce little secondary radiation. Some people have suggested surrounding the living quarters of the ship with a tank of liquid hydrogen. According to Bushnell, a layer of liquid hydrogen 50 to 100 cm thick would provide adequate shielding. But the tank and the cryogenic system is likely to be heavy and awkward. Here again, nanotubes might be useful. A lattice of carbon nanotubes can store hydrogen at high densities, and without the need for extreme cold. So if our spacecraft of the future already uses nanotubes as an ultra-lightweight structural material, could those tubes also be loaded up with hydrogen to serve as radiation shielding? Scientists are looking into the possibility. Above: When high-energy cosmic rays crash into
astronauts' DNA, it can cause damage leading to cancers or other
radiation-induced illnesses. Images courtesy NASA's Office
of Biological and Physical Research. Camping out in
the cosmos "We can't take most of the materials with us for a long-term shelter because of the weight consideration. So one thing we're working on is how to make radiation-shielding materials from the elements that we find there," says Sheila Thibeault, a scientist at LaRC who specializes in radiation shielding. Right: Astronauts setting up camp on Mars will need protection from space radiation. Image credit: Frassanito and Associates, Inc. One possible solution is "Mars bricks." Thibeault
explains: "Astronauts could produce radiation-resistant
bricks from materials available locally on Mars, and use them
to build shelters." They might, for example, combine the
sand-like "regolith" that covers the Martian surface
with a polymer made on-site from carbon dioxide and water, both
abundant on the red planet. Zapping this mixture with microwaves
creates plastic-looking bricks that double as good radiation
shielding. The folks back
home Left: Crafted from smart materials, tomorrow's airplanes
could have self-bending wings that operate without flaps--thus
reducing drag and lowering fuel costs. [more] |
Credits & Contacts Author: Patrick L. Barry Responsible NASA official: John M. Horack |
Production Editor: Dr.
Tony Phillips Curator: Bryan Walls Media Relations: Steve Roy |
The Science and Technology Directorate at NASA's Marshall Space Flight Center sponsors the Science@NASA web sites. The mission of Science@NASA is to help the public understand how exciting NASA research is and to help NASA scientists fulfill their outreach responsibilities. |
Web Links |
Buck Rogers, Watch Out! -- Science@NASA article: NASA researchers are studying insects and birds, and using "smart" materials with uncanny properties to develop new and mindboggling aircraft designs. Samples of the Future -- Science@NASA article: The advanced space ships of tomorrow will be crafted from far-out materials with extraordinary resistance to the harsh environment of space. The Materials International Space Station Experiment (MISSE) aims to find out which materials work best. Right: Backdropped by the rising Sun, MISSE juts into space outside the International Space Station. [more] Digging in and taking cover -- Science@NASA article: Lunar and Martian dirt could provide radiation shielding for crews on future missions. See also "Making Mars Bricks" Center for Nanotechnology (CNT) -- at NASA's Ames Research Center Needs of future missions -- listing of technologies needed for future space exploration and some possible solutions, from the CNT Nanotube Links: Nanotubes & Buckyballs (Nanotechnology Now); Carbon nanotubes (Penn State University); Johnson Space Center Nanotube Project (NASA) Research in molecular electronics: a nano-scale transistor from IBM; a simple logic gate made from nanowires; a customizable nanotube for wires or structures from Purdue University Space Weather on Mars -- Science@NASA article: Future human explorers of Mars can leave their umbrellas back on Earth, but perhaps they shouldn't forget their Geiger counters! A NASA experiment en route to the Red Planet aims to find out |
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