On Friday, Virgin Galactic’s SpaceShipTwo will fly in space for the second time, taking off from Mojave, California after days of weather delay. Their launch time is set for 8 a.m. PST.

Unlike most spaceflights that fire rockets from the ground, SpaceShipTwo is carried on the back of a plane named WhiteKnightTwo before being released to propel itself into the upper atmosphere. It’s a suborbital flight, meaning it does not reach orbit, and attains weightlessness for only a few minutes duri