An article appearing in the September 5, 2001 issue of
For the version on the Space.com web site, click
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by Erik Baard, Technology Correspondent
A material that might pass as Play-Doh for Magneto, the mutant master of magnetism in the Marvel Comics universe, may be critical to the success of future space missions in ways both mundane and exotic.
Magnetorheological (MR) materials are fluids that solidify into a pasty consistency in the presence of a magnetic field (as molecules assemble in somewhat stiff chains along field lines), and then re-liquify when that force is removed. One can also achieve a similar effect with electric fields. In either case, the fluids can do work that in the past involved intricate moving parts.
In its simplest form, an MR fluid can be filings suspended in corn oil, but more advanced materials are made from high-tech ceramics mixed with specialized synthetic polymer media. The newer forms use elastics to combat MR fluids? Achilles heel: settling and clumping.
The first stages of the technology were best known for providing resistance in exercise machines and to make advanced shock absorbers in cars. But the wonder goop has worked its way into space engineers? toolboxes to suppress vibrations during rocket launches, and, when mixed with abrasives, to precisely polish astronomical lenses and mirrors.
Future applications envisioned for interplanetary exploration include: dampening tremors on geologically active planets and moons, controlling the movement of remote-controlled suits, smoothing the bumps of space station docking, preventing the buckling of delicate solar arrays when a probe or satellite emerges from an eclipse, regulating oxygen flow within space stations, reducing stress caused by repositioning satellites, and creating molds that can be reconfigured to manufacture different machine parts in a pinch.
Back on Earth, you may see MR fluids popping up as Braille that can be scrolled and amended as easily as text on a monitor, as a stabilizing leg brace for the elderly or disabled, or as an injection to block blood flow to cancerous tumors.
Prosthetics, tremors and footwear
Because they are soft and respond to stimuli faster than human tissue, MR fluids and their cousins are being considered for virtual reality simulations called haptic interfaces, and there?s even been a U.S. patent granted for an MR "penile prosthetic."
One Russian proposal to make athletic footwear with MR fluids brings magical "flubber" to the mind of Ford Motors researcher John M. Ginder, who's developing infinitely practical shock absorbers with the stuff.
Henri Gaven, a professor of engineering at Duke University, is bullish on the possibility of shielding people and machines from tremors with MR fluids. That?s not just critical on Earth, but also on worlds like Venus and Jupiter?s moon Io. The materials involved in making an MR fluid can be relatively cheap, and more importantly for space missions, they spring into action with minimal energy consumption.
"The beauty of MR materials is that they can be used to regulate hundreds of Watts of mechanical power with just a few Watts of electrical power," Gaven wrote in an email interview with SPACE.com.
"For this reason, the energy balance is strongly in favor of MR materials, as opposed to other actuation methods, such as hydraulics, piezeo-materials, or magneto-strictive materials."
Borrowing astronauts' bodies
MR fluids could be a key component of landing gear that adapt "automatically and instantaneously to the local geo-technical conditions of the landing site," Gaven said.
The downside for space launches is that magnets can be heavy, costing more fuel to escape Earth?s gravity.
But as magnetic technologies improve, we might start to see virtual realty suits that allow experts to "borrow" astronauts? bodies, as they too wear special suits to perform highly specialized tasks, said Yoseph Bar-Cohen of NASA?s Jet Propulsion Laboratory.
Such telepresence is at the core of his Memica program. One surprising virtual reality application conceived of by Bar-Cohen?s research team is training doctors in deep space -- like the starship medical officers we?ve become accustomed to in science fiction who care for crews of hundreds, if not thousands of people coming in with illnesses and trauma on a daily basis.
But our first deep space explorers are likely to be sent out in small crews. A doctor?s skills could rust with disuse. Bar-Cohen would like to see doctors constantly training by operating on virtual patients. MR fluids could simulate the resistance of human flesh, he says, so a surgeon wearing a virtual reality suit will have not only the look, but also the feel of soft tissue under his or her scalpel.
Other astronauts also might wear the suits as a routine to provide the kind of full-body resistance needed to combat muscle atrophy in zero gravity, Bar-Cohen notes.
Shape-shifting speculative
One thing that the researchers agreed MR fluids wouldn?t develop into anytime soon is a shape-shifting material.
Ginder dismisses wild speculations in popular media about cars that can emerge from a wreck with a simple reset button.
"The difficulty is delivering a magnetic field to such a large structure and to shape it in such complex forms," he explains. "It?s the same problem Braille systems would face even on that smaller, simpler scale.
Gaven agrees.
"Morphing shapes using MR materials and magnetic fields ... is far-fetched, in my opinion," he says.
But breakthroughs in precise digital control of magnetic fields could spark an explosion in the emerging field.
"Whenever you say something is not possible," Bar-Cohen said, "someone will beat you at it."