ABL Space Systems has suffered a setback in its space launch ambitions, losing its second RS1 rocket after a fire broke out during a static-fire test. The company detailed the incident on August 26, which occurred on July 19 at the Pacific Space Complex – Alaska on Kodiak Island, during the final stages of preparation for the rocket's second launch.
The company ignited the E2 engines in the RS1’s first stage, but aborted the test after just half a second due to a low pressure reading in one engine. ABL attributed this to a faulty pressure sensor. While the engines shut down, a fire erupted under the base of the vehicle, fueled by leaking fuel from two engines. The fire was initially contained, but the water and inert gas systems proved ineffective in extinguishing it. The company began offloading the kerosene and liquid oxygen propellants from the vehicle.
The launch pad lacked its own water supply, forcing ABL to rely on mobile tanks that ran out of water 11 and a half minutes after the fire started. This resulted in the fire spreading and disabling the pad systems, hindering detanking efforts and eventually cutting off telemetry from the rocket.
"At T+ 23:24, the fire exceeded the thermal capability of the structure and RS1 buckled to the pad,” ABL stated. This led to extensive damage to the electrical and plumbing connections on the launch mount, though the mount’s structure and other ground support equipment remained intact.
An investigation into the fuel leaks revealed significant erosion in the two engines’ propellant injectors and liners. ABL identified this as a sign of combustion instability failure. “Our current leading theory is that differences in the Block 2 Stage 1 propellant feed system led to a higher energy startup than on the test stand, triggering an instability in 2 of 11 engines,” it stated.
ABL clarified that despite over 300 tests of the E2 engine, this phenomenon had only been observed once previously, which was attributed to a different issue. The company acknowledged limited experience with this specific configuration and launched a series of tests at its Mojave Air and Space Port test site in California to verify the cause and explore other potential factors.
ABL has not yet provided a timeline for completing the investigation or for its next launch attempt. Ground support equipment is being returned to Long Beach, California, for repairs while production of the next RS1 rocket is underway.
This incident comes just over 18 months after ABL's first launch of the RS1. The rocket lost power 10 seconds after liftoff and crashed at the launch pad. The company subsequently attributed the failure to a fire in the rocket's engine compartment caused by a design flaw in the launch mount, which was subsequently redesigned. The rocket lost in the July fire was a Block 2 version of the RS1, boasting 20% higher thrust, 20% more propellant, and two additional engines in the first stage.