XCOR Aerospace said Sept. 2 it had reached several significant milestones in its Lynx 5K18 rocket engine test program.

The Mojave, Calif.-based company built the liquid oxygen and kerosene-fueled engine to power the piloted Lynx suborbital spacecraft it is developing for space tourism and scientific research missions.

XCOR Chief Executive Jeff Greason said the engine has demonstrated the ability to be stopped and restarted using a spark-torch ignition system. “The basic cooling design has also been completed and the engine is able to run continuously at thermal equilibrium,” he said in a statement. “With those milestones reached, the 5K18 test program is now moving forward into a second phase of tuning and optimization, in which we will also greatly increase our cumulative run time.”