Commercially viable fusion energy may well be only 20 years away - but as yet, with unproven research, this could equally be 30 or 40 years away.

A growing number of organisations around the world are concluding from their recent research designs that fusion energy should be practical within the next 10-15 years.

Note that internal chills will absorb both heat capacity and heat of fusion energy.

After a few years the star consumes all its neon and the core ceases producing fusion energy and contracts.

This represents a fusion energy gain factor (or simply fusion gain) of three.