The second-generation RocketMotorTwo engine is a variant of the earlier SNC basic design, but is fueled by polyamide plastic fuel, while continuing to use the same nitrous oxide oxidizer. The second-generation engine is now made in-house by Virgin Galactic rather than by SNC. By December 2012, 15 full-scale tests had been successfully conducted, and additional ground tests continued into March 2013. In June 2012, the Federal Aviation Administration (FAA) issued a rocket testing permit to Scaled Composites, allowing it to begin SS2 test flights powered by RocketMotorTwo; the first such powered flight took place on 29 April 2013. The engine produces 60,000 pounds-force (270 kN) of thrust.