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Superconductivity might be very helpful in establishing electromagnetic launch systems on Luna. It is a complex topic about which there is much misinformation spread around. To properly understand superconductivity, one should first understand the usual cases of conductivity in such a way that superconductivity is a natural outcome of this understanding.

We begin with the proper understanding of the electron. In the double-slit experiment, results for electron diffraction can be explained by considering that the electron does not have a defined size, merely a measured cross section for any defined interaction with other particles. Cross section is usually measured in barns. The electron is diffuse enough, when not bound to an atom, molecule or crystal, to go through both slits at once, as a stream of water goes through the many holes of a sieve and comes out as a stream of water on the other side. The two slits combined merely act to deflect the electron by randomly variable amounts in turn determined by variations in initial conditions less than the Heisenberg uncertainty amount. The double slits just act like pachinko pins. A large enough number of electrons through the dual slits or pachinko balls through the set of pins will be distributed statistically according to probability. Playing pachinko could help in understanding an aspect of elementary particles.

When the electron is bound to an atom, molecule or crystal, it is always in one orbital or another. The orbitals are more restricted in space than free electrons. They are associated each with its characteristic frequency. They are most easily defined by the amount of energy lost by the electron when it becomes bound. And they have interesting characteristics in metals and other crystals that result in electrical conductivity and in certain conditions superconductivity.

Conduction orbitals are of particular interest. In sodium, silver and copper (for example) the outermost electron in each atom is loosely bound. When such an atom joins a crystal of like atoms the loosely bound outer electron becomes bound to the crystal in a conduction orbital instead of being bound to an individual atom. Electrons can move from one orbital to another only by quantum exchanges of energy and momentum. In sodium, for instance, any of the two 1s electrons, the two 2s electrons or the six 2p electrons could jump up to the conduction orbital energy level and start moving around if they first recieved the quantum of energy necessary to make the change. However photons or latice vibrations with that amount of energy are usually not available and the ten localized sodium electrons remain bound to the sodium nucleus and do not move about the crystal. If a 2p electron did absorb a quantum of energy from a photon to jump to a conduction orbital, it would leave behind a hole which would be filled by any passing conduction orbital electron. The electron droping into the 2p orbital would give off the same quantum of energy as a photon as was required to make a hole there in the first place. The process of giving off a quantum as a photon is always available whereas the process of absorbing a quantum is available only when a photon or latice vibration of that energy is present.

Once the sodium atoms have joined a crystal, electrons no longer populate the 3s orbitals, one to a sodium atom, because the conduction orbitals are of lower energy. In order to become localized a conduction electron would need to absorb a quantum to become a 3s electron. It would then just give off that quantum again while absorbing a little momentum from the latice or another conduction electron and become a conduction electron again. There are exactly ten electrons per sodium atom in a crystal that fill localized orbitals and leaving these orbitals is a big quantum jump. There are many conduction orbitals and there is always a vacant conduction orbital a small quantum jump away from any occupied conduction orbital. So by trading small amounts of energy and momentum with the crystal latice or with other conduction electrons an electron is always able to move from one conduction orbital to another. This situation contributes to the electrical and thermal conduction of the crystal and it contributes to electrical resistance.

The situation with Yittrium, Lanthanum, and Bismuth is not so straight forward. These elements have partially filled lower energy orbitals. In ceramic crystals in which atoms become ionized the odd partially filled sets of orbitals sometimes give rise to a conduction orbital at lower energy than the ordinary conduction orbitals, but so constrained that there is no nearby empty conduction orbital that conduction electrons can jump to using the quanta of energy available in a low temperature crystal. That means electrons in this energy level must continue to conduct with the same momentum that they had when the crystal formed. They can not get enough energy to rise to a nonconduction orbital or an orbital with different momentum. The electrons can not all leave the left side of the crystal and pile up on the right side so electrostatic forces require that half of them conduct electricity to the left and half conduct electricity to the right for zero net conduction. The condition is again changed by man who forms a ring and sets more conduction electrons going one way than another. Once the pattern is set the electrons still do not have the energy to change it. They will keep on conducting electricity in a circle forever or until the temperature allows them to get enough energy to change.

In a superconductor based upon Yittrium in a ceramic crystal a conducting electron cannot change it velocity because a different velocity would be associated with a different freqency for the conduction electron orbital, and it must have a frequency to keep the nodes of the conduction orbital in the same spatial relationship with Yittrium ions. The condution orbital can accept only quantum changes in velocity and, since the Yittrium ions are spaced so far apart, the needed quantum for a change in velocity is more than the energy available in the cold crystal.