FUSION HYPOTHESES 2
The key to helium 3/ deuterium fusion is stronger containment fields generated by more powerful magnets, higher temperatures generated perhaps by lasers, and longer plasma confinement times.  Longer plasma confinement times also depend on stronger magnetic fields from magnets made of metal wrapped with superconducting wires. Hi temperature 77 deg. K YBCO wire consisting of a LN2 filled tube wrapped with a ribbon of YBCO without copper electromagnetic shielding or more recent 135 K superconductors that can carry heavy currents are the materials to use.  They don't need as much cryogenic refrigeration power as niobium-tin and liquid helium.  If high energy lasers heat the plasma instead of neutral particals (deutrons) there might be less turbulence in the plasma.  TOKAMAKS have reached "break even" and the ITER is predicted to produce more power than it consumes.  Linear fusion reactor research is no longer on going but these reactors might still have a future if leakage from the ends can be controlled by large "baseball" mirrors fitted into each other in a matrioshka arrangement.  Deutron beams or lasers and photon pressure might also prevent the plasma from leaking.

Helium 3/deuterium fusion will not release large floods of neutrons as will deuterium/tritium fusion.  The high energy neutrons from DT fusion can knock atoms out of their crystalline lattice and if they are absorbed by nuclei they can activate those atoms and cause them to become radioactive.  The neutrons can also cause superconducting materials to transmute into other elements that are not superconducting.  Knocking atoms out of their crystalline lattice can damage materials and make superconductors ineffective also.  Helium3/deuterium fusion does produce a small numbler of neutrtons from D-D side reactions but this is minimal compared to
D-T fusion.  Thus, it is likely that D-T fusion will not be a commercial success but he3-D fusion will be and this will motivate Moon mining.  Due to the lower neutron flux of he3-D fusion, expensive he3 "burning" reactors will outlast D-T reactors and return profits on investment from the sale of electricity. 
Once the he3-D plasma is heated and fusion of a fraction of the he3-D ions begins, they will release alpha particles and protons that will be contained by the magnetic fields unlike the high energy neutrons of D-T fusion that escape and impart their energy to the lithium jacket.  These a-particles and protons will collide with he3 and D ions and impart their energy gained by fusion into the non-fusing he3 and D ions and heat them up so that they will have enough energy to overcome positive electrical repulsion by other nuclei and they will fuse, releasing more hi energy a-particles and protons.  The plasma will self heat without introducing any more energy into it by deutron beams, lasers or RF heating and fusion will erupt like a chain reaction.  As long as the magnetic confinement field is intense enough to contain the plasma. 

The plasma could get so hot that it expands and escapes from the "magnetic bottle" and plasma density drops, fusion power falls off, and more energy has to be pumped into the plasma with deutron beams or lasers to get it up and going again. So the reactor could operate in a "pulsed mode."  The plasma will escape when it gets to energetic to remain contained and be directed thru positively charged hi voltage channels to MHD generators and boilers or in the case of a space drive it will be allowed to exhaust away for propulsion by reaction.

Linear reactors on Earth will use nickel-steel magnetic cores wrapped in HTS wire.  They will need heavy vacuum pumps and sealed jackets.  They will need heavy cryogenic cooling machines.  In space, vacuum is free and sealed jackets are not needed although foil solar radiation shielding might be desirable.  Foil shielded space radiators protected from the Sun will be exposed to the 10 K temperature of outer space so cooling will be practical for the superconducting coils in space.  The metal cores of magnets for space drives could be made of beryllium.  This metal has the highest stiffness to weight ratio of any metal so it will not deform due to intense magnetic field caused mechanical stresses.  It will magnetize like the aluminum in a junkyard crane electromagnet only when the current is flowing.  Beryllium is as strong as mild steel and as light as magnesium.

Perhaps huge laser crystals 60 feet long could be grown in microgravity or in the low gravity of the Moon for lasers to energize fusion reactor plasmas.  These could be flown down in the Space Shuttle cargo bay.  If any of this is possible it would be wise to keep the Shuttle flying.  Whether or not these solid state laser crystals could be used as defensive systems in unknown to this author.
Spacecraft for transporting laser rod from lunar surface to LLO.