MILAN — The loss of a solid rocket booster nozzle on the second flight of the Vulcan Centaur spacecraft had very little impact on the launch itself, but the impact of the incident on the vehicle’s certification by the Space Force remains uncertain.
At Cert-2’s launch on October 4, the nozzle of one of two SRBs attached to Vulcan’s core stage exploded about 35 seconds after liftoff. The incident, which United Launch Alliance called “Observation,” appeared to have a temporary effect on the vehicle, but it continued its ascent, with the timing of subsequent events falling behind the published schedule by up to 20 seconds.
Speaking at the International Astronautical Congress on October 14, Los Angeles Federation CEO Tore Bruno said the accident caused only a small loss in performance. “The net effect of that was less than 2% of the total booster boost,” he said, while the engine continued to fire but at reduced efficiency due to the lack of a nozzle.
He added that the nozzle did not affect the engine itself or endanger the entire car. “We didn’t have as much momentum as we would like.”
The core stage compensated for the loss of performance from the SRBs, including steering from the BE-4 engines to compensate for asymmetric thrust between the SRBs. “This was less than the core stage’s liquid propellant reserves,” he said. “Vulcan is a monster.”
This was demonstrated in the final performance of the vehicle and the accuracy of its orbital injection. Engineers are still analyzing data from the flight and comparing it to previous ULA launches, “but I’m pretty sure this is our most precise injection yet,” Bruno said.
The cause of the nozzle exit is still under investigation, he said, noting that nothing like this has been seen in the 35 launches of the GEM 63 engines and several of the larger GEM 36XL engines used on the Vulcan.
Any changes to the nozzle should be straightforward on the 35 GEM 63XL engines stored for future Vulcan launches, since the nozzle section is bolted on, he said. “I’m quite confident, having encountered this kind of anomaly more than once in my career, that we will get to the bottom of this very quickly and move forward.”
“We still have a very successful mission, perhaps one of the most successful missions we have done,” he concluded.
What is less certain is how this anomaly will affect plans to certify Vulcan Centaur by the US Space Force. The Cert-2 mission was the second of two Vulcan launches needed to obtain certification for national security launches. Prior to Cert-2, ULA had hoped to achieve this certification in time to conduct the first two launches before the end of the year.
Bruno declined to speculate on any changes in the timeline for obtaining certification when asked about them after his presentation. He said that process is in the hands of the Space Force, which has not commented publicly on a timeline for certification.
“This will be something we work on together with our customer at Space Force,” his staff along with ULA teams review data from the launch, he said. “I hope this helps them do their part in getting certified.”
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