Sunday, April 9, 2023

About That Centaur Engine Anomaly

Back on March 31st in one of my small story roundups, I relayed that ULA CEO Tory Bruno had Tweeted that the Vulcan's upper stage suffered "an anomaly" without specifically saying what happened.  In the last couple of days, some interesting things have surfaced.  Perhaps the most interesting is a photograph tweeted by Eric Berger, the space correspondent for Ars Technica, but this is his personal twitter account. This is said to be the "anomaly" but most of us would call that an explosion. Orange cloud to the left.

This picture and a little more information is used in a video from a YouTube channel that I look at a few times a week, Starbase Pink.  When I first ran across the channel, they had a different name (I think it was SpaceX Pink) and used a synthetic female voice.  When they changed to the current format, they dropped the synthesized voice, going to (I assume) the original channel owner.   

Berger originally says the photo shows the anomaly—a fireball of hydrogen igniting—to the left of Blue Origin's rocket engine test stand, but hydrogen is well-known for having a nearly invisible flame.  Flames of that orange-yellow color are associated with coming from organic chemical bonds with higher radiated heat than hydrogen gives. To me, the fact that the fireball is clearly visible looking toward the sun implies that isn't hydrogen, but I'll say it could be from burning something else that was in the vehicle.

Berger and Ars Technica, to their credit, published a more in-depth coverage of all that's known, and that contains things that don't make sense to me as stated.  

"A column of burning, clear hydrogen shot up into a mushroom cloud that dwarfed the test stand," one source said. "Their test article is definitely more than just 'damaged.'"


A Blue Origin source confirmed that a mushroom cloud formed from the anomaly. Afterward, United Launch Alliance asked Blue Origin to delete the explosive video footage from the company's computers, which Blue Origin agreed to do.

(Note: After publication of this article, when asked about the video deletion, Bruno tweeted that this "didn't happen." However, two sources told Ars that after the incident, United Launch Alliance asked Blue Origin to "secure" the video for its investigation. Blue Origin did so, but also removed the video from its own internal servers, reserving access only for a few officials at the company).

The whole story is a bit hard to process.  Upper stages called Centaur have been flying since the '60s, but this one is apparently a new version.  Which answers one of the first questions: why are they testing a Centaur -  unless something major has changed (bearing in mind that "because we feel like it" or "we do this on every other engine" are perfectly valid answers).  Bruno has recently said an upper stage called Centaur V would be able to operate for 40 percent longer in flight and has two-and-a-half times more energy than the Centaur upper stage ULA currently flies, but nobody referred to this engine by that name.  Is this a new Blue Origin engine other than the BE-4s powering the first stage of the Vulcan?  Exactly how big an impact is this for the first Vulcan Centaur mission?  Is it using an older, better known engine?

To this observer, it looks like the plans for two launches this year, including one that would lead to US Space Force certification, are either done for the year or hanging on by a thread.


  1. Won't happen - I think they miss their Russian engines. Or were there other changes?

    1. Most likely there ARE changes (why not?), resulting in design-build-test-analyze cycles. It's interesting that ULA is trying to cover something up, are they THAT worried about appearances??

  2. I would only note that the traditional Centaur stage has been pressure-stabilized, meaning that the propellant tanks have to be sufficiently pressurized to support the vehicle. The Mariner 6 spacecraft was on an Atlas-Centaur vehicle at the pad when "a faulty switch opened the main valves on the Atlas stage. This released the pressure which supported the Atlas structure, and as the booster deflated it began to crumple. Two ground crewman started pressurizing pumps, saving the structure from further collapse. The two ground crewman, who had acted at risk of the 12-story rocket collapsing on them, were awarded Exceptional Bravery Medals from NASA.
    The Mariner 6 spacecraft was removed, put on another Atlas/Centaur, and launched on schedule." - from