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High
and Mighty
The
next killer app for DuPont's
super-strong Kevlar polymer may be
in outer space, as a
nanofiber for
next-generation rockets and space
shuttles.
by
Peter Galuszka
In
March 2003, a month after the space shuttle Columbia disintegrated over Texas,
killing seven astronauts aboard, a NASA official made a
telephone call to Arnie Frances, a
senior research associate at DuPont’s sprawling Spruance production facility
in Richmond.
The
Columbia had exploded on re-entry because a piece of insulating foam had broken
away during launch and damaged the Shuttle. Did chemical giant DuPont have
anything new in its fibers research pipeline that could help prevent future disasters?
“It
turned out we did have something very new on the drawing board,” says Frances.
DuPont’s Spruance has turned out steadily improved versions of Kevlar,
a bullet-stopping fiber that is five times stronger than steel, for four
decades. The latest developments involve using nanotechnology to make very tiny
slivers of Kevlar. In this new form, Kevlar could be inserted into cell walls of
foam insulation in ways that would make it stronger and hopefully more damage
resistant.
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A
few months after the initial phone call, DuPont and officials at NASA’s
Marshall Space Flight Center in Huntsville, Ala., signed an agreement to explore using Kevlar
“micro pulp” or “nano pulp” in what would be a dynamic new application.
It might be used as insulation in the next generation of launch vehicles – the
Ares I and V – that will take the replacement |
for the space shuttle into
orbit, to the moon and Mars, and perhaps beyond.
Although
it won’t be known for a year if Kevlar will be used commercially in this form,
early tests are promising, says Edmund Semmes, a NASA aerospace technologies
specialist at the Marshall Space Flight Center in Huntsville. The 2003 agreement
calls for DuPont and NASA to bear their
own costs of research until a final decision is made to proceed. “DuPont has been very good to us over the
years and we have especially close ties with Richmond,” Semmes says.
Such
ties are long-standing. NASA has used many DuPont products since it started its
space program in the 1950s. Space suits worn by astronauts use Nomex, a fire
retardant made at DuPont’s sprawling Spruance plant. And Kevlar, discovered in
1965 and made mostly at Spruance, has been used in various space applications
over the years, such as shielding against meteorites. The fiber's contribution
to body armor and shields for vehicles in war zones is so critical that in
September the firm announced a $500 million global expansion of Kevlar
production, including a $50 million addition in Richmond.
As
years have passed, DuPont has constantly refined Kevlar and introduced new
applications. One of the latest involves nanotechnology that uses Kevlar fibers
in an ultra light form, says Kathy Kowalski, director of global new business at
DuPont’s Advanced Fiber Systems in Richmond.
The
focus of current research is to see if Kevlar can help strengthen foam
insulation, shielding the second stage
of the two-stage Ares I rocket. Atop the rocket will be a six-person capsule
called the “Orion” that will be the space vehicle that will serve as the new
space shuttle. Like the existing shuttle, it will orbit the earth, perform
missions and dock with the International Space Station. Unlike the current space
shuttles, it won’t fly back to earth like an airplane but, like older
capsules, will parachute to Earth after re-entry in the atmosphere. The first
flight of Ares I is expected in 2009 and trips to the space station are expected
by 2014.
Breaking
free of Earth’s gravity is, of course, a major factor in putting the 25-ton
Orion payload into orbit. In the first stage of Ares I, solid-fuel propellants
will burn for two and a half minutes after blast-off until the vehicle reaches a
height of 38 miles and a speed nearly six times the speed of sound.
After
the first stage burns its fuel and falls away, the second stage takes over. Its
J2X engine, which evolved from Apollo-era programs of the early 1970s, will be
fueled by liquid hydrogen and oxygen. They will burn until the vehicle is 83
miles above Earth’s surface, enough to throw Orion into orbit. Liquid hydrogen
and oxygen must be kept at extremely low temperatures at this critical phase
of the launch. Liquid hydrogen, for example, must be stored at less than minus
423 degrees Fahrenheit or it starts to boil and evaporate. Liquid oxygen starts to do the
same at minus 238 degrees, Semmes says. If the fuel evaporates, then the Orion
capsule won’t be able to reach the desired orbit, with potentially disastrous
results.
That’s
where Kevlar might play a role. NASA and DuPont are experimenting with inserting
Kevlar into the foam on the cladding around the rocket’s second stage. The
substance’s strength and light weight in the new, micro form could serve two
important functions. It could ensure that the fuel stays cold enough. And it
could protect the cladding from falling away the way it did in the Columbia
disaster and shield against outside objects that might puncture the fuel cells.
NASA
and DuPont officials are careful not to draw too much of a comparison with the
Columbia situation. In that case, during the launch, a piece of foam insulation
about the size of a small briefcase broke from the main propellant tank. Parts
of it damaged the shuttle’s left wing and thermal protection system.
When the Columbia was returning to Cape Kennedy and was penetrating the
atmosphere over Texas on its landing approach, there wasn’t enough protection
against the intense heat. The shuttle broke apart in a spectacular explosion
that killed the crew.
“The
best way to say it,” notes Semmes, “is that if there was foam that had a
higher strength, it possibly could have prevented the Columbia
accident.”
One
safeguard being built into the Orion capsule is a better way of letting the
module containing the astronauts break away in an emergency. Upgrading foam to
higher strength levels is another, although Semmes notes that foam itself
“would not be capable of protecting the shuttle in re-entry.”
DuPont’s
Kowalski says that, at least initially, only small portions of the new Kevlar
material would be used if the Ares I cooperation proceeds. It will not involve any
major new production increases of Kevlar at the 3,000-worker Spruance plant.
However, the program announced Sept. 19 to increase Kevlar production worldwide
by 25 percent should bring some new jobs to the Richmond area. Spruance will get
a $50 million expansion to increase production of polymers used in Kevlar.
If
Kevlar is used in Ares I, it has a good chance of being deployed in the
much-bigger Ares V rockets, Semmes notes. Those larger launch vehicles will be
used to take new capsules to the moon, perhaps by 2020. There are also plans to
use Ares V for Martian missions. Since they are bigger, they could involve
greater use of Kevlar.
Adapting
to outer space applications is only one way in which the high-performance fiber
has evolved at Spruance. Kevlar is also used to create “storm rooms” in
homes in tornado- and hurricane-prone areas. In a weather emergency, families
can retreat to the rooms and be safe from projectiles hurled about by extremely
strong winds.
Kowalski
says that the Spruance expansion is part of a corporate-wide “megatrends”
study that examined potential new markets and products. Regarding Kevlar,
“certainly the war is critical,” she notes. “But we’re finding that
we’re growing in all categories.” Using it to get astronauts to Mars might
be just one of them.
-- October 2007
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