Space explorers have yet to get their hands on the replicator of
"Star Trek" to create anything they might require. But NASA has
developed a technology that could enable lunar colonists to carry out on-site
manufacturing on the moon, or allow future astronauts to create critical spare
parts during the long trip to Mars.
The method, called electron beam freeform fabrication (EBF3), uses an
electron beam to melt metals and build objects layer by layer. Such an approach
already promises to cut manufacturing costs for the aerospace industry, and
could pioneer development of new materials. It has also thrilled astronauts on the
International
Space Station by dangling the possibility of designing new tools or objects,
researchers said.
"They get up there, and all they have is time and
imagination," said Karen Taminger, the materials research engineer heading
the project at NASA's Langley Research Center in Virginia.
Taminger's project has undergone microgravity tests aboard NASA's
"vomit comet" aircraft. Now she hopes to get EBF3 scheduled for
launch to the International Space Station, so that space trials can commence.
Shaping metals at will
EBF3 requires a few crucial components: power for its electron beam, a
vacuum environment, and a source of metals. While Star Trek's replicator
could work without a supply of subatomic particles, reality is a different story.
"It'd be nice if we could build something from nothing, but it
doesn't work that way," Taminger told SPACE.com.
For EBF3, metal wires continually feed into the tip of an electron beam.
The beam melts the wires and applies them carefully on top of a rotating plate
to build an object up slowly, layer by layer.
A few similar technologies exist, but EBF3 has several advantages.
First, its electron beam requires far less power than comparable devices and
produces less radiation compared to more powerful beams. Its dual wire feeders also
allow scientists to create mixes of new materials that vary in strength or
other properties within the same solid piece.
"We can change the composition on the fly," Taminger
explained. "You can add alloys of different chemistries and then adjust
the speed that you feed the wires, and that would change the chemistry of the
parts we build."
The flexibility of the manufacturing could also embed fiber optic cables
inside a solid piece of metal, either for use in communication or for
monitoring stresses within the manufactured part.
Major aerospace manufacturers have already begun running thousands of
strength tests with the EBF3 device to see whether it can produce certified
parts for engines and airframes, researchers said. They foresee cost savings of
up to $1,000 per pound of manufactured parts, compared to the usual forging and
machining methods that require a 6,000-pound block of titanium to produce a
300-pound part.
Testing in microgravity
Early "vomit comet" tests on NASA's C-9 aircraft showed that
EBF3 could work well in a zero-g environment. Taminger and her team managed to
build a number of parts that looked exactly the same as parts built on Earth,
down to the microstructure scale.
Some researchers had predicted that the method would fail to produce
anything but "ball bearings," or liquid metallic spheres in zero-g.
But the wire feeders successfully deposited the metal layers onto the rotating
plate as usual, except for the occasional misaligned wire that would create a
growing sphere on its end.
"We learned a lot more when things went wrong," Taminger said.
"When things go wrong in zero-gravity, you just don't have as much
experience to guess what would happen."
The effects of zero-g often comically exaggerated any mistakes, and
allowed the team to improve the overall process for Earth manufacturing as
well. They even ran a few experimental tests going from zero-g to two gees as
the C-9 aircraft would pull out of its steep dive.
The big next step for EBF3 involves going to the space station. Taminger
has already gotten the device down to a "suitcase style experiment"
that fits within a volume of less than eight cubic feet, but still needs
funding and a possible slot aboard one of the remaining space shuttle missions.
The device could also go up on a contracted NASA flight with the Russian Soyuz
rockets, or even a private launch.
Going to the space station means that EBF3 can take advantage of the
vacuum environment in space, and sit on an outside rack -- perhaps the
"back porch" of Japan's Kibo
space lab.
Spare parts for Mars
Beyond low-Earth orbit, such new manufacturing technology could enable
space colonists to use local metal resources mined from
the moon, Mars or in the asteroid belt.
Past simulations have also shown that spaceships would require many
spare parts for the long journey to Mars, because different parts failed during
each simulation. But the total weight of parts that failed during each run was
roughly the same, which suggests a Mars mission could simply take along metal
feedstock and an EBF3 device.
"If we've got a broken part, we can even repurpose that into
feedstock, or can we mine new material," Taminger said. "The short
term solution is that you bring along the material you need, but you don't need
to bring the parts that you need."
The EBF3 device probably won't churn out spare parts immediately, if it
reaches the space station. But astronauts who have seen the device in action
have expressed excitement over the idea of making their own tools, 21st century
pioneer style.
"They can build a shovel, or a clamp or a widget, or whatever they
might come up with," Taminger said. "They're not just stuck with the
toolbox they brought along."
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