credit Virgin Galactic / caption: this is a screen grab from the video
It was not clear from the press release or the video whether the SpaceShip Two (SS2) rocket motor two testing involved a full scale engine or that one was fired for as long as SS2 needs it too but Virgin Galactic president Will Whitehorn has told Hyperbola that that is the case
“Full scale and there were three firings, still more to do in phase two but it has burned for a full SS2 profile,” Whitehorn told Hyperbola
So one assumes three rocket motors were used for this first phase and its three tests. Hyperbola hopes to bring further rocket motor testing details including whether SS2 prime contractor Scaled Composites and its motor development partner Sierra Nevada subsidiary Spacedev have resolved issues the SpaceShipOne motor had, such as its low- and high-frequency combustion instability
