Four months from fiery explosion to return to flight. SpaceX announced the quick turnaround in an update on their website this morning. For four months, officials from across the aerospace industry have worked together to investigate what caused the “anomaly.” Investigators looked at thousands of pieces of data to piece together what caused a Falcon 9 rocket to explode (technically a fast fire).

According to SpaceX, “there was just 93 milliseconds from the first sign of anomalous data to the loss of the second stage, followed by the loss of the vehicle.” The good news (if there is any in a situation like this) is the failure happened while the rocket was still on the ground. Investigators were able to sift through multiple ground-based video angles and gather physical debris from the incident.

The final results of the investigation point the finger at a failure of a pressure vessel (COPV) inside the second stage liquid oxygen (LOX) tank. Investigators believe the failure was likely because of the accumulation of oxygen between the vessel’s aluminum liner and carbon overwrap in a buckle in the liner.

While the buckles didn’t burst the vessel on their own, investigators say the accumulation of super chilled LOX collected in pools under the overwrap. Once pressurized, the oxygen becomes trapped. “Breaking fibers or friction can ignite the oxygen in the overwrap, causing the COPV to fail.” Add in the frigid temperatures of the helium and the conditions were there for solid oxygen to form, which makes the possibility of oxygen becoming trapped and igniting even higher.

The investigation team identified several different scenarios for the COPV to fail. Each possible scenario is the result of accumulated LOX or SOX in buckles under the overwrap. SpaceX is taking action to address all these scenarios.

In the short term, that means changing the COPV configuration to handle warmer temperature helium to be loaded. SpaceX will also use a previous flight proven configuration for loading helium. Long term, SpaceX engineers will change the design of the COPVs to get rid of the buckle problem altogether. It fixes the potential problem and will lead to faster loading operations according to the company.

SpaceX reaches back to the sky

With the investigation wrapped up, SpaceX announced it is targeting a return to flight on January 8. A Falcon 9 rocket will launch from Vandenberg’s Space Launch Complex 4E. Onboard will be the first of 10 Iridium NEXT satellites.

Iridium is partnering with SpaceX for seven launches. Each one deploying ten Iridium NEXT satellites at a time. A total of 81 satellites are being built. 66 will be operational at any given point.

Like with most satellite constellations, Iridium is preparing for the occasional satellite hiccup. 15 spares will be available. 6 in-orbit and 9 more on the ground. The satellites in orbit will be able to be activated and repositioned whenever they are needed.

In a statement last month, Iridium remains confident in SpaceX’s abilities. “We’re excited to launch the first batch of our new satellite constellation. We have remained confident in SpaceX’s ability as a launch partner throughout the Falcon 9 investigation,” said Matt Desch, chief executive officer at Iridium. “We are grateful for their transparency and hard work to plan for their return to flight. We are looking forward to the inaugural launch of Iridium NEXT, and what will begin a new chapter in our history.”

Every satellite launch is huge, but Sunday is pivotal for SpaceX. A smooth launch Sunday will help restore any shaken confidence from the explosion four months ago. And it will put the company on a path to tackling its backlog of missions. You can check out all of SpaceX’s future missions here. The missions are listed in alphabetical order, not by date. We’ll see how Sunday’s launch goes and how the four-month delay affects the launches of the other missions.

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