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 iron 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.
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| A motorcycle shock absorber works by stimulating a MR fluid chamber to
harden or soften instantly to counteract vibration and bumps. Click to enlarge. Credit: CSA Engineering.
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| Particles float freely in fluid until exposed to a magnetic field. They then form stiff chains along magnetic force lines, giving the once liquid material a consistency like paste or hard wax. Click to enlarge.
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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."
Next page: Simulating flesh resistance
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