A drift may consist of a single large
habitat, a cluster of
habitats, or a shell of habitats surrounding a large mobile
hotpoint.
As a result they are some
of the largest
structures that
Backgrounders
may construct, sometimes measuring several tens
of thousands of kilometers across.
Propulsion is
generally of very high efficiency with
deep-space
acceleration provided by
plasma
or
ion drive, deceleration and direction
changes via
magnetic
sail acting against the galactic magnetic field, and
sometimes even
fusion
drives when a particularly large or swift alteration
in
heading is required.
In
addition many
drifts will deploy large solar sails when passing near a star for the
purpose
of changing direction or velocity via gravity-assist maneuver and
light-pressure.
Regardless of the exact form or
structure of the drift
itself, the defining characteristic of such craft is their method of
travel. Drifts are
multi-generational
craft designed to operate almost exclusively in interstellar space,
only
occasionally passing near a star for the purpose of changing direction
or
harvesting resources.
The purpose of a drift is not to
reach a particular
destination but to provide its inhabitants with a permanent home that
is
independent of any single star (and perhaps more importantly from the
perspective of many Backgrounders, independent of the ruling hand of
the Sephirotic AIs).
Drifts
are similar to many worldships
in their method of
operation and velocity regime (0.01 to 0.03c). However
while a worldship may occasionally spend several
decades or
longer inside a solar system between voyages, drifts almost never come
closer
than several tens of AU to a star and never stay in the
vicinity of a star
system any longer than they absolutely have to.
The vast distance between individual drifts is a major contributory
factor in the disjointed nature of the Backgrounder culture.
Information, news and cultural influence is very slow to spread from
one drift to another, and the inhabitants of individual drifts
rarely meet.
