The Burt Rutan SpaceShip One looks very light weight,
so I would assume it has some modest glide performance...albeit
likely at a higher speed than what we are used to.

Bet if it ran into mountain wave on the way back down
from space, it could climb in the wave. That would
meet the definition of glider then.

The SS1s drawback for a soaring performance is high Wing Loading and very
low aspec-ratio wings.
This means high stall speed and high sink rates, both non-conducive to
significant soaring performances.

The average sink rate according to their public data is 2500ft/min, and
stall speed with one person on board and no fuel was 70kts.