WHAT ARE SUPERCONDUCTORS?

Superconductors conduct electricity with little to no resistance. They carry large electric currents with less power loss and generate strong magnetic forces.

WHY AREN’T SUPERCONDUCTORS USED MORE?

Superconductors need to be cooled to extremely low temperatures. The first superconductors called Low Temperature Superconductors (LTS) need to be cooled to 4°K close to the temperature of outer space. This means cooling with liquid helium (He). Sadly liquid He is expensive because it is hard to work with something so cold.  He is also becoming scarce because it has to be mined from solid minerals (He gas is so light it just floats away). Superconductors already use 30-40% of the world’s He production.

The cost and difficulty of liquid He limits LTS use to special applications such as medical Magnetic Resonance Imaging (MRI).

It is widely recognized that Space is cold (3°K) enough with available sunshields for superconductivity (=20°K). But Superconductors in Space @ Ambient Temperature has yet to be tried because no application was important enough for space deployment. So far superconductor use in space has been for small scale instrumentation or infrared telescopy where permanent magnets or readily available cyrocooled solutions were used.

WHAT IS A HIGH TEMPERATURE SUPERCONDUCTOR (HTS)?

HTS were discovered in 1986. They raised expectations for wider superconductor use because HTS can be cooled by liquid nitrogen (N) at 77°K. Liquid N is a cheap, readily available by product used in doctor offices, beauty salons, and restaurants. But HTS is still not used much because they are brittle single ceramic crystals that break easily. Once broken superconductivity stops.

OUR BREAKTHROUGHS ADDRESS THESE CHALLENGES

1) We strengthen HTS using long continuous reinforcement fibers. This should lead to the long awaited, practical use of liquid N cooled HTS in both existing and new applications.

2) Our LAU CoilgunTM uses superconductors in space for Boost-Phase Missile Interception which should lead to the eventual obsolescence of strategic nuclear missiles.

3) We have invented applications for magnetic induction and plasma deflection for hypersonic vehicles, aircraft, spacecraft docking and space debris collection.

REINFORCING HIGH TEMPERATURE SUPERCONDUCTORS

A time honored way to strengthen materials is internal fiber reinforcement or ¨straw in bricks¨.

But reinforcement is difficult because HTS is made by first melting component powders at ≈ 1200°C, then cooling under oxygen. Reinforcing material placed inside oxidizes at high temperatures, forming impurities which interupt crystal growth and form secondary seeding sites. These weaken HTS crystal strength and hurt performance. HTS strenghtening has so far been limited to external reinforcement such as Packing in Tubes, Deposition on Substrates, or Stainless Steel Encasing.

A SOLUTION:

REINFORCE HTS WITH LONG CONTINUOUS SILICON CARBIDE (SiC) FIBER

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RESULT: 40% gain in strengh with just three 100 μm thick SiC fibers in a 25mm diameter sample.

Silicon in SiC fibers reacts at high temperatures with O2 creating a layer of inert SiO2 preventing further oxidation. This is similar to how chromium (Cr) makes steel stainless.

The LAU CoilgunTM in Boost-phase Missile Interception should be a critical Killer Application for using Superconductors in Space @ ambient temperatures

One might ask ¨why haven’t superconductors been used in space before?¨ There are two reasons:

1) TEMPERATURE: space is cold at ≈ 3°K but this is not cold enough for widely used superconductors on earth which need liquid He cooling (≈ 4°K). Cooling costs are also raised by the need for radiant heat shielding in space. For instrumentation, this typically makes superconductors impractical compared to proven permanent magnets. For example the Alpha Magnetic Spectrometer (AMS-02) installed outside the ISS in 2011 planned to use niobium-titanium superconductors circa 2005 cooled to 1.8 K. But a permanent magnet used in an earlier prototype AMS-01 ended up being used instead.

OUR SOLUTION: WE HAVE IDENTIFIED SUPERCONDUCTORS WHICH SHOULD WORK IN SPACE WITHOUT ACTIVE COOLING

2) APPLICATIONS: Past ideas did not justify the cost of a trial in space. Some modern superconductors can operate at temperatures as high as 40°K and have been digitally modelled for space by NASA and the European Space Agency. These models focused on generating magnetic fields in space which could actively shield astronauts from charged particle cosmic ray radiation. Plans were made to deploy superconductors in space for tests. But these did not materialise because the structures projected would be too large to stop the rare, extremely heavy charged ions (up to a gold atom nucleus) which were of concern for astronauts. Superconductor magnetism can protect satellites which are susceptible to much lighter and more frequent protons and alpha particles. But current commercial belief is that the passive, non-magnetic shielding used now is sufficient. This should change when the next Carrington Event sized Coronal Mass Ejection hits earth.