Prerequisites:

Description:

    This technology consists mostly of picking the correct orbits (or solar wind pressure system) to build a shell completely around a star, blocking all of its light and using that light for productive purposes.  This is essentially the last-ditch method of achieving fusion power, as the sun is a fusion-powered device (it just isn't very portable).  Picking orbits to block the first 10% of the light coming from a star is easy.  The difficulty after that is to block an increasing fraction of the light without (a) collisions (which could potentially start a chain reaction, which would be VERY bad) or (b) having the light to your outermost satellites obstructed too often, reducing practical efficiency.
    Improvements in Dyson Sphere (dev) reduce the probability of catastrophic chain reaction and increase the tradeoff between more satellites and more inefficiency.  At some (finite) level of development, a full 100% Dyson sphere becomes phossible.
    Actually BUILDING a dyson sphere may well be the work of centuries for an entire species if self-replicant machines are not available.