It has plenty of power
Source: spaceref
Given the weight and length of the aircraft nobody will be surprised to know that it needs plenty of power. It has taken on six engines used in current Boeing 747s to get it flying. When it makes that first flight it will move into space, release the rocket, before circling around to make a re-entry. Although it won’t be the world’s first aircraft in space it will be the biggest and give the space industry a new, regular, working carrier.