An experimental SpaceX rocket engine has exploded in Texas

A Merlin rocket engine exploded Sunday at SpaceX's test facilities in Central Texas. According to the company, no one was injured during the mishap, which damaged two bays in a Merlin engine test stand at the MacGregor facility.

"All safety protocols were followed during the time of this incident," said a company spokesman, John Taylor. "We are now conducting a thorough and fully transparent investigation of the root cause. SpaceX is committed to our current manifest, and we do not expect this to have any impact on our launch cadence.”

SpaceX feels confident in its launch manifest—the company plans to launch three or four more missions in 2017—because the Merlin engine lost Sunday is being developed for the Block 5 version of its Falcon 9 rocket. All of its launches this year (and during the first several months of 2018) are scheduled to fly on the Block 4 variant of the rocket, which uses an earlier Merlin engine.

The company has three engine test stands at MacGregor: one for Merlin engines, one for the newer, more powerful Raptor engine, and another stand for upper-stage engines. The Merlin test stand has two bays, and while one bay may require as much as four weeks to repair, the other bay should be ready for use within a couple of days. This will allow the company to continue "acceptance" testing for its Block 4 Merlin engines, the penultimate test before a rocket is assembled, shipped to the launch site, and the entire booster undergoes a static fire test on the launch pad.

Sunday's explosion, which was first reported by The Washington Post, occurred before the engine was lit, a source told Ars. It happened during a procedure known as LOX drop, in which liquid oxygen is added to the engine to determine if there are any leaks. At that point, something caused the fluids within the rocket engine to ignite. Testing of the Block 5 Merlin engine will be suspended until the cause of that ignition is found and fixed.

SpaceX has a lot riding on its Block 5 variant of the rocket, which the company's founder, Elon Musk, has said will improve the rocket's performance and optimize its reusability and capability for rapid turnaround. This version of the rocket will also be used for commercial crew flights, which will carry astronauts to the International Space Station for NASA. The company has not announced a target date for the maiden flight of the Block 5 rocket, but it is expected in 2018. It is not yet clear how much Sunday's engine explosion will delay that debut, if at all.