The 'outward urge' was a factor in the Troon inheritance. Successive generations of Troons, looking up at the stars, heard the siren voices that called them out into Space. And, as the frontiers of Space receded, there was usually one Troon, if not more, out there, helping to push them back.
In an age in which what goes up need not necessarily come down, the likely adventures of the Conquistadors of Space are every bit as exciting as any world menaced by triffids.
