An early morning static fire at Celestial Space Corporation’s Brancaster Testing Range ended in a dramatic explosion on May 9, as an Acheron first stage prototype suffered a major failure just six seconds after ignition. Thick black smoke and fire poured from the test stand. This is a serious setback for the company’s next orbital launch vehicle.

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The event occurred on Test Stand A3, the facility’s heavy duty vertical test stand designed to support large stage firings. Liquid methane and liquid oxygen propellant loading began around 06:05 local time, with engine ignition at 06:40. The stage lit all seven engines as planned, similar to the previous full duration test, before abruptly failing in a fiery blast.

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“During Flight Demonstration testing with first stage article at BTR, the hardware experienced an anomaly,” said CEO Kwingo in a public post. “This is why we exercise every possible condition on the ground before flight. Investigation is underway. Acheron will fly when complete.”​​

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The test article had been lifted onto the test stand two days prior, and it seemed this was a significant milestone in the Acheron program. The failure appeared to originate from the engine bay area, as footage captured by cameras shows a large fire shooting from the base of the vehicle just moments before a visual and audible explosion.

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Venting systems activated immediately, likely a pressure relief to reduce the risk of total vehicle loss. However, unusually, fire was observed exiting the lower vent ports, implying further damage internally.

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By 07:10, propellant tanks empty and fire suppression teams had fully extinguished the flames. The damaged vehicle was removed from the test stand and returned to a hangar for assessment later that day.

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What Failed? And Why Now?

Another unanswered question concerns exactly what Acheron stage Celestial was testing, or what it was for. Was it a fully flight-like stage to be used for a future mission? Or was it more of a prototype stage used for development testing, which might be more susceptible to failure? Celestial Space would not comment on this. If the former, the explosion could be significant risk to Acheron's upcoming schedule. If the latter, failure might have been expected under aggressive testing.

 

With no official statement beyond Kwingo’s post, speculation is inevitable. Analysts note that Acheron’s seven engine configuration is a large change in complexity from Celestial’s older solid fuel design. Managing stability and much more complexities across such a system is substantial engineering challenge.

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The Acheron program is widely considered Celestial’s most ambitious effort to date. It is a partially reusable methane fueled launch system designed to serve both payload and human missions. But with a significant ground test failure, concerns are growing that the company may be straining its resources across too many simultaneous projects.

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“We don't know what exactly happened yet.” Kwingo added when asked for clarification. “But we’re reviewing everything. If anything, this shows why we test.”

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Time is running out for Celestial to complete the development of Acheron and fly two certification missions this year. This would allow the vehicle to begin flying government payloads, and would certify it for commercial flights. Celestial had hoped to fly its first mission in mid 2025, but now that goal seems fading.

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