SN9

SN9, or Serial Number 9 "Eileen", was the second fully stacked starship prototype which has made a suborbital flight. After a perfect flight to the apogee of 10 km on 2 February 2021, it was destroyed upon landing as one Raptor engine failed to reignite. SN9 is often referred to as "Eileen". This name was given to the Starship after it tilted in the High Bay. (As in "I Lean")

## Timeline

* **02 Feb 2021: Launch and RUD**
* 03 Feb 2021: Wreckage inspection and cleanup began
* 06 Feb 2021: Wreckage cleanup
* 10 Feb 2021: Repair work began on pad after RUD
* 11 Feb 2021: Wreckage cleanup
* 14 Feb 2021: Wreckage cleanup
* 17 Feb 2021: Wreckage cleanup

* 19 Feb 2021: FAA closed the investigation of the mishap
* 19 Feb 2021: Final parts removed

## Flight Outcome and Analysis

SN9 reproduced the good outcome of the SN8 flight, making a good flight up to apogee, belly flop and flip maneuver. However, the landing attempt again failed. While SN8 had a header tank underpreassure issue, SN9 didn't manage to reignite one of the two engines needed for landing. As a result of this, SN9 flipped but wasn't able to turn back to upright position and also didn't decrease enough velocity, crashing into the landing pad and exploding.

The crash caused repair for the landing pad to be required again.

Furthermore, Elon Musk mentioned, that for future tests all three engines would be relit for the flip maneuver and the one with the least lever arm would shut down if all 3 are good. It would be risky to ignite all 3 engines and throttle them down, as they could flame out. If one engine doesn't respond as expected, the other two will be able to make the landing.

## FAA investigation

After a major problems between SpaceX and the FAA (Federal Aviation Administration) due to a license violation with SN8, SpaceX implemented corrective actions that were incorporated into the launch of SN9 in order to get FAA approval. Nevertheless, the FAA opened a new investigation into the "landing mishap" of SN9 on the day of the launch:

"The FAA's top priority in regulating commercial space transportation is ensuring that operations are safe, even if there is an anomaly. The FAA will oversee the investigation of today's landing mishap involving SpaceX Starship SN9 prototype in Boca Chica, Texas. Although this was an uncrewed test flight, the investigation will identify the root cause of today's mishap and possible opportunities to further enhance safety as the program develops."

According to Jackie Wattles on twitter, the FAA closed the SN9 investigation on February 19:

"The FAA closed the investigation of the Feb. 2 SpaceX Starship SN9 prototype mishap today, clearing the way for the SN10 test flight pending FAA approval of license updates. The FAA provided oversight of the SN9 mishap investigation conducted by SpaceX. The SN9 vehicle failed within the bounds of the FAA safety analysis. Its unsuccessful landing and explosion did not endanger the public or property." Wattles concludes that the SN9 investigation has been a fairly routine investigation unlike the investigation into the SN8 launch license violation.

## Where to find additional information

1. ↑ https://twitter.com/elonmusk/status/1357426784279609344
2. ↑ https://twitter.com/thesheetztweetz/status/1356763309802979328
3. ↑ https://twitter.com/thesheetztweetz/status/1356761131721912320
4. ↑ https://twitter.com/jackiewattles/status/1362888684987539457