#InterstellarTravel101 #Cloaking101

With that said, let’s begin #Cloaking101

On Mars they don’t use cloaking, so when you look up you see the Frigates coming in and out of the Martian Atmosphere outside the domes.

It’s important you all understand the basics of Cloaking Technology if we are to keeping you ahead of the curve.

(Phys.org)—Typically when two magnets are brought close together, they either attract or repel each other due to interactions between their magnetic fields. In a new study, researchers have designed a 3D magnetic invisibility cloak, inside of which they placed a magnetic object, and showed that the cloaked magnet is no longer affected by nearby magnetic fields. It appears as if the cloaked magnet has become demagnetized, but in reality the magnet is simply hidden.

The researchers, led by Yungui Ma at Zhejiang University in Hangzhou, China, have published a paper titled "Three-dimensional magnetic cloak working from d.c. to 250 kHz" in a recent issue of Nature Communications. Like other invisibility cloaks, the new cloak is made of metamaterials (man-made materials with repeating patterns) and works by manipulating electromagnetic waves in unusual ways.

To achieve the cloaking effect, the researchers used a new type of invisibility cloak called a bilayer cloak, first demonstrated in 2012 by Alvaro Sanchez and colleagues at the Autonomous University of Barcelona. The cloak has a spherical structure consisting of two shells: a superconducting inner shell (made of single-crystal YBCO) and a ferromagnetic outer shell (made of a nickel zinc composite).

The bilayer cloak consists of an inner superconducting shell and an outer ferromagnetic shell, whose opposite effects on an external magnetic field completely cancel each other out to shield a cloaked magnetic object (yellow) from the external magnetic field. Credit: Zhu, et al. ©2015 Nature Communications

Basis: Experimental realization of a magnetic cloak
A recent article in Science presents the successful experimental realization of a dual-layer cylindric cloak for magnetic fields [8]. Such a device creates a field-free region inside and no interferences outside a cylindrical volume, which is exactly the field configuration we want to achieve. This section summarizes the basis of this experiment and its results.

Fig. 2 (top) illustrates the basic idea: A ferromagnetic cylinder placed in a magnetic field (A) pulls in fields lines and reduces the flux inside the cylinder while distorting the field homogeneity. On the other hand, a superconducting cylinder (B) creates a field-free region inside the cylinder by pushing out the magnetic field lines and distorts the field homogeneity around the cylinder in the opposite way. For ideally homogeneous magnetic fields, the combination of a superconducting inner cylinder with a ferromagnetic outer cylinder of the right radius, thickness, and permeability (C) creates a field-free region inside and no interferences outside the cylinders.

Based on Maxwell’s equations, the permeability and radii of the ferromagnetic layer have to relate according to:

to achieve this perfect cloak. R1 and R2 are the inner and outer radius of the ferromagnetic layer and µ2 is the magnetic permeability of this layer. The superconducting layer does not need to have a specific thickness.
The cloak described in [8] is 12 mm long and has an inner diameter of 12.5 mm and an outer diameter of 17.5 mm. It consists of multiple layers of Fe18Cr9Ni alloy sheets for the outer (ferromagnetic) layer and a high temperature superconductor (ReBCO) on the inside. Both materials are commonly available, which allows for the construction of such a device at relatively low cost end effort.
Fig. 2 (bottom) shows the result of measuring the magnetic flux along a line 3 mm above the cloak in a homogeneous magnetic field of 40 mT. The presence of the cloak practically has no effect on the field homogeneity outside, which confirms the viability of this magnetic cloak design [8].

Physicists have already unveiled invisibility cloaks that can hide objects from light, sound, seismic and even water waves. Now researchers report a cloak that can hide objects from static magnetic fields. This 'antimagnet' could have medical applications, but might also subvert airport security.


The cloak's interior is lined with turns of tape made from a high-temperature superconductor. Superconductors repel magnetic fields, so any magnetic field enclosed within a superconductor would be undetectable from outside. But the superconductor itself would still perturb an external magnetic field, so the researchers coated its external side with an ordinary ferromagnet — the material that kitchen fridge magnets are made of. The superconductor tries to repel external field lines, whereas the ferromagnet tries to draw them in — together, the two layers cancel each other out.