Fire Fueled by Leaking Engines Destroys ABL Space Systems Rocket

WASHINGTON — ABL Space Systems Inc. said it lost its second RS-1 rocket after a static test launch when a fire broke out under the vehicle fueled by leaking fuel that platform systems could not extinguish.

On August 26, the company released details about the July 19 incident that resulted in the loss of the vehicle during one of the final tests before the vehicle’s second launch at Pacific Space Launch Complex – Alaska on Kodiak Island.

in statementABL Space Systems said it ignited the E2 engines on the first stage of the RS-1 rocket in the test, but abort the test after just half a second due to a low pressure reading in one of the engines, which the company said was caused by a faulty pressure sensor.

The engines stopped working, but then a fire broke out under the vehicle’s base, due to fuel leaking from two engines. The fire was contained but could not be extinguished using water or inert gas systems, and the company began emptying the vehicle of kerosene and liquid fuel.

The launch pad the company uses in Kodiak does not have its own water source, instead using mobile tanks that ran out of water 11 and a half minutes after ignition. This caused the fire to spread and “a gradual loss of platform systems,” the company said, including the inability to continue draining the tank from the rocket and eventually telemetry from the rocket.

“At 23:24, the fire exceeded the thermal capacity of the structure and RS1 leaned over the platform,” the company said. This damaged “the majority” of the electrical and plumbing connections on the launch cradle, although the launch cradle structure itself and other ground support equipment remained intact.

An investigation into the two engines that caused the fuel leak that led to the fire showed “significant wear” of the fuel injectors and their liners, which the company said was a sign of failure linked to combustion instability. “Our current leading theory is that differences in the fuel feeding system on the Block 2 first stage resulted in increased operating power compared to the test stand, resulting in instability in two of the 11 engines,” the company said.

ABL added that in more than 300 tests of the E2 engine, it had only observed this phenomenon once, attributing it to a different problem. The company added, however, that it had little experience with this particular configuration and that it had begun a series of tests at its Mojave Air and Space Port test site in California to see if this explanation was correct and to look for other possible causes.

The company did not provide a timeline for completing that work or attempting another launch. ABL said it will return ground support equipment to Long Beach, California, for repairs while the next RS1 rocket “is in production.”

The fire occurred more than 18 months after ABL’s first launch of the RS1 rocket. The vehicle lost power 10 seconds after liftoff and crashed on the launch pad. The company later concluded that the launcher’s design contributed to a fire in the rocket’s motor compartment that led to the loss of power, and redesigned the launcher.

The vehicle destroyed in the July fire was a modified version of the RS1 Series 2. This version had 20 percent more thrust, 20 percent more fuel, and added two engines to the original nine-engine first stage.

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