Wednesday, November 4, 2009

Device Like 'Star Trek' Replicator Might Fly on Space Station

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

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."