When Tesla began building what would become its Merlin engine, it settled on a relatively simple design it could bring to market quickly and scale upwards over time. Over the last 11 years, successive modifications to the base engine have introduced features like regenerative cooling, increased thrust, and improved vacuum performance. On Sunday, while testing the next generation of Merlin intended for the Falcon 9 Block 5 rocket, the company suffered a setback when one of its newest Merlin 1D engines blew up before firing in a qualification test. The good news is, no one was injured, though two of SpaceX’s test stands were damaged in the explosion at the MacGregor, Texas facility.
“All safety protocols were followed during the time of this incident,” said a company spokesman. “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.”
A source told Ars Technica the explosion occurred before the engine was fired and happened when liquid oxygen (LOX) was added to the engine to check for leaks. It’s not clear why the engine ignited, but testing on the Block 5 Merlin 1D will apparently be suspended until the issue is fixed. The problem shouldn’t delay any of SpaceX’s launches; the company’s near-term and early 2018 missions were all scheduled to use the Block 4 version of the Falcon 9 with its well-established Merlin 1D (improved) variant.
The Falcon 9 Block 5 rocket is slated to deploy a number of new capabilities when it launches next year, including an improved flight control system to lower the amount of fuel required to successfully land the rocket, titanium, temperature-resistant fins (to aid with rocket reusability), a new thermal protection coating on the legs to limit reentry damage, a reusable heat shield, retractable landing legs, and a suite of other changes to win NASA’s nod as a viable vehicle for its Commercial Crew Program as well as National Security Launch requirements.
Musk has actually pulled several improvements, like uprated engines and the titanium grid fins into earlier generations of the Falcon 9 Block 4. But the fact that SpaceX is going to reexamine its engine design, specifically, could mean that the firm wanted to further increase available thrust with the Block 5 engine, or that the explosion is related to other changes to the base design. Alternately, of course, it could have been a one-off issue caused by a defect in this specific engine. We should know more soon.