It’s been nearly six months since Blue Origin’s 23rd suborbital launch experienced an anomaly, and the company has finally released the results of its investigation. The good news is the escape function worked great! But there was definitely a nozzle problem.

The September flight, NS-23, was carrying a number of science payloads and no space tourists (let alone billionaires), so fortunately there was never anyone in danger. The anomaly occurred in the first ascent stage, triggering the abort process. The capsule separated from the propulsion module and deployed its parachutes, while the rocket fell to the ground.

Unfortunately this meant that the investigators had to reassemble the rocket to figure out what happened:

Forensic evaluation of the recovered nozzle fragments also showed clear evidence of thermal damage and hot streaks resulting from increased operating temperatures. The fatigue location on the flight nozzle is aligned with a persistent hot streak identified during the investigation.

The nozzle is the cone-shaped bit at the end of the rocket that contains and shapes the thrust. Naturally it has to be extremely heat-tolerant, but even a rocket nozzle has its limits. According to the Blue Origin investigators, “changes made to the engine’s boundary layer cooling system” led to higher temperatures and produced a persistent hot streak on this nozzle, eventually causing the thrust coming from that engine to differ from the rest. That mismatch triggered the escape system.

A piece of the engine nozzle identified by the team. Image Credits: Blue Origin

I’ve asked Blue Origin for more information, specifically how long that design change (and the resultant hot streaks) were in use, and will update this post if I hear back from them.

Returning to flight after an anomaly is a complicated process, but Blue Origin has been staying ready by applying for rolling launch window permissions with the FCC, and today this investigation report (in full detail, not the short version) has been submitted to the Federal Aviation Authority. That’s the agency that ultimately decides when the company can fly again, but the timeline for evaluating the report is up to them.

The company, for its part, merely said it expects to fly again “soon” — and the payloads that had their trip interrupted in September will be the first to go up.