  In this paper we explore the effectiveness of an artificial
mini-magnetosphere as a potential radiation shelter for long term human space
missions. Our study includes the differences that the plasma environment makes
to the efficiency of the shielding from the high energy charged particle
component of solar and cosmic rays, which radically alters the power
requirements. The incoming electrostatic charges are shielded by fields
supported by the self captured environmental plasma of the solar wind,
potentially augmented with additional density. The artificial magnetic field
generated on board acts as the means of confinement and control. Evidence for
similar behaviour of electromagnetic fields and ionised particles in
interplanetary space can be gained by the example of the enhanced shielding
effectiveness of naturally occurring "mini-magnetospheres" on the moon. The
shielding effect of surface magnetic fields of the order of ~100s nanoTesla is
sufficient to provide effective shielding from solar proton bombardment that
culminate in visible discolouration of the lunar regolith known as "lunar
swirls". Supporting evidence comes from theory, laboratory experiments and
computer simulations that have been obtained on this topic. The result of this
work is, hopefully, to provide the tools for a more realistic estimation of the
resources versus effectiveness and risk that spacecraft engineers need to work
with in designing radiation protection for long-duration human space missions.
