SN10

SN10 was the fifth fully stacked Starship prototype. It had been rolled out while SN9 still was at the pad, so for the first time, two Starships were at the launch site. On 03 March 2021 it was launched from pad A and after six minutes and 21 seconds it landed on the pad. However it exploded about 8 minutes later. Nevertheless, SN10's flight was a huge success and progress for the program, as much data had been collected and it was able to land vertically on the pad, something that SN8 and SN9 failed to do.

## Timeline

* **29 Jan 2021: Roll out to pad A**
* **31 Jan 2021: First vents (proof test)**
* 01 Feb 2021: First Raptor delivered
* 05 Feb 2021: Second Raptor (SN50) delivered and installed
* 06 Feb 2021: Third Raptor (SN39, removed from SN8) installed
* 07 Feb 2021: flap movement, FTS installed and removed again (fit check)
* **08 Feb 2021: First Cryo test (see below)**
* 10 Feb 2021: Flaps folded
* 11 Feb 2021: Closure cancelled
* 12 Feb 2021: Closure cancelled
* **19 Feb 2021: Venting**
* 20 Feb 2021: Work on engine section and near the hatch
* 21 Feb 2021: Aft fins inspected and tested
* 22 Feb 2021: FAA approval
* 22 Feb 2021: Scrubbed static fire attempt
* **23 Feb 2021: Static fire #1**
* 24 Feb 2021: One raptor removed, RSN51 installed
* **25 Feb 2021: Static fire #2**
* 27 Feb 2021: Upper flap testing
* **28 Feb 2021: Methane vent**
* 28 Feb 2021: FTS installed
* 28 Feb 2021: Evac notice for March 1, NOTMAR for March 1-5, launch delayed to NET Wednesday, March 3
* 01 March 2021: 02 March closure cancelled, TFRs from Wednesday-Friday
* **01 March 2021: RCS test at 02:31 am**
* 02 March 2021: Evac notice, closures
* **03 March 2021: Flight, landing and destruction**
* 04 March 2021: Wreckage inspected, cleanup began; leg pulled from the dunes
* 06 March 2021: Wreckage cleanup and scrapping
* 07 March 2021: Wreckage cleanup continued
* 08 March 2021: Wreckage cleanup continued, almost cleared
* 11 March 2021: Wreckage cleanup continued

## 8 February 2021 - Cryogenic proof test

Timeline according to LabPadre:

* 08:13 Road Closed
* 09:30 Pad cleared
* 11:56 Ground vent
* 12:00 SN10 vent
* 12:08 Low icy ring
* 13:15 Depress
* 13:16 Cars to pad
* 13:27 Pad cleard #2
* 13:48 Ice ring #2
* 13:59 Mid ice ring
* 14:37 Depress #2
* 15:32 Detank
* 15:50 Test completed
* 15:50 Road opened

## 22 February 2021 - Scrubbed static fire attempt

Timeline according to LabPadre:

* 10:52 Road closed
* 15:46 Pad cleared
* 15:59 Ground vent
* 16:57 Recondenser
* 17:15 Ground vent
* 17:16 Farm venting
* 17:45 Tank farm depress??
* 17:55 SN10 depress vents

## 23 February 2021 - Static Fire #1

Timeline according to LabPadre:

* 13:01 Road closed
* 15:13 Pad cleared
* 16:04 Recondenser (before ground vent!)
* 16:14 Ground vent
* 16:14 Farm venting
* 16:23 Skirt vent (LOX tanking)
* 16:29 Methane vent, Drone arriving
* More intervals of Methane vent, indicating a hold (Adrian Beil)
* 16:44 Tri-vent (Engine Chill), frost line appearing later
* 16:51 Siren
* 16:52 LOX Header tank vent and frost appearing
* 17:01 Header vent stopped
* 17:03 Static Fire, normal duration
* 17:03 Immediate depress vents, detank

The tri-vent had a very long duration compared to other static fires. Elon Musk posted a tweet on February 24 indicating that one engine turned out to be suspect, so SpaceX decided to swap it out. This resulted in further delay of the launch, as it was previously scheduled for Thursday.

## 25 February 2021 - Static Fire #2

Timeline according to LabPadre:

* 12:27 Road closed
* 14:05 Pad cleared
* 14:24 Ground vent
* 16:09 Recondenser
* 16:24 Farm/condenser venting increase
* 16:33 Skirt vent
* 16:34 Methane vent
* 16:45 Tri-vent (Engine chill)
* 16:47 Siren
* 16:51 nosecone vent, no condensation
* 16:54 condensation from forward flaps, condensation/frost appearing on nosecone
* 16:57 Static fire
* 16:59 Depress vent, detank
* 17:34 More depress

After the strange countdown sequence on February 23, this sequence was much more close to the ones experienced on SN9 and before.

## 03 March 2021 - Flight

### Official SpaceX information

On Wednesday, March 3, Starship serial number (SN10) successfully completed SpaceX’s third high-altitude flight test of a Starship prototype from our site in Cameron County, Texas.

Similar to the high-altitude flight tests of Starship SN8 and SN9, SN10 was powered through ascent by three Raptor engines, each shutting down in sequence prior to the vehicle reaching apogee – approximately 10 km in altitude. SN10 performed a propellant transition to the internal header tanks, which hold landing propellant, before reorienting itself for reentry and a controlled aerodynamic descent.

The Starship prototype descended under active aerodynamic control, accomplished by independent movement of two forward and two aft flaps on the vehicle. All four flaps were actuated by an onboard flight computer to control Starship’s attitude during flight and enabled a precise landing at the intended location. SN10’s Raptor engines reignited as the vehicle performed the landing flip maneuver immediately before successfully touching down on the landing pad!

As if the flight test was not exciting enough, SN10 experienced a rapid unscheduled disassembly shortly after landing. All in all a great day for the Starship teams – these test flights are all about improving our understanding and development of a fully reusable transportation system designed to carry both crew and cargo on long-duration interplanetary flights, and help humanity return to the Moon, and travel to Mars and beyond.

Congratulations to the entire Starship and SpaceX teams on the flight test![1]

### Elon Musk Twitter statements

Elon Musk confirmed on twitter that touchdown was too hard, because the single raptor engine showed low thrust despite being commanded higher. It has been unclear as for what caused this, SpaceX never have seen this before. Musk added that next time they would use at least two engines all the way to the ground and restart engine 3 if engine 1 or 2 have issues.[2] This statement leaves it somewhat unclear wheter all three engines would initially be reignited and one immediately shut down if all are good, as Musk suggested after the SN9 flight, something they obviously didn't do with SN10 as they used all three engines to do the flip and then shut down two engines.

As for the leg deployment, Musk stated that they "got squashed hard" as the touchdown was way past leg loads.[3]

Later, Elon Musk explained, why they think the engine was low on thrust: "SN10 engine was low on thrust due (probably) to partial helium ingestion from fuel header tank. Impact of 10m/s crushed legs & part of skirt. Multiple fixes in work for SN11." This helium pressurization was supposedly added to the CH4 header tank after the pressure problems of SN8. Musk acknowledged this: "Fair point. If autogenous pressurization had been used, CH4 bubbles would most likely have reverted to liquid. Helium in header was used to prevent ullage collapse from slosh, which happened in prior flight. My fault for approving. Sounded good at the time." On the question, whether baffles will be used to prevent slosh, Musk answered: "There were baffles, but one may have acted like a straw to suck bubbles in from above liquid/gas level. Something similar happened on an early Falcon 1 flight, resulting in unexpectedly high liquid oxygen residuals at main engine cutoff."

Asked again on the landing leg design, Musk posted, although not clear if serious: "Might just catch the ship with the launch tower, same as booster". Everyday Astronaut (Tim Dodd) asked, if they just could use a net instead of propulsivly landing. But this wouldn't be a gamechanger according to Musk: "Yeah, we talked about that internally. Could just have it land on a big net or bouncy castle. Lacks dignity, but would work. But, optimized landing propellant is only ~5% of dry mass, so it’s not a gamechanger."

### Flight summary and analysis

Using different sources (LabPadre, NSF, SpaceX, Scott Manley)

After a first abort at T-00:00.1 due to a slightly conservative high thrust limit (Elon Musk), SpaceX decided to try again. After recycling, SN10 took off three hours later by igniting its 3 raptor engines, after a short hold at T-01:00. SN10 followed a similar flight profile as SN9, with an apogee of around 10km, while SN8 went up to 12km. SN9 and SN10 translated more horizontally than SN8.[4] At T+02:15 the first engine shut down, as no more this amount of thrust was needed in order to reach apogee. It was to be noted that one engine, the one that later shut down, had orange exhaust, indicating it running fuel rich.[5] At T+03:13, roughly 8km altitude, this engine cut off, leaving SN10 to ascend with one remaining engine. Confusingly, Insprucker mentioned switching to the header tank for this engine, although header tanks are only used for landing. It is yet unclear, what was meant by that.

SN10, now not gaining much height anymore and more or less hovering, used its remaining engine at T+04:20 to start the flip to horizontal. The raptor then immediately shut down and the flaps and flings were used to control the maneuver. SN10s descent was very stable and used its aero-covers to guide itself. At T+05:47, the tri-vent started, indicating engine-chill for raptor ignition. At T+05:59 to 06:00, all three engines were reignited successively in order to translate into vertical position and to decelerate quickly. This is a change to the flight of SN9 which reignited only two engines, but one had a failure. So it was decided to reignite all three in order to have more redundancy. As with SN8 and SN9, SN10 translated more than just vertical, reaching a tilt of 10-20 degrees. At T+06:07 two engines shut down. This is somewhat contradictory to what Elon Musk intended to do: "It was foolish of us not to start 3 engines & immediately shut down 1, as 2 are needed to land"[6]. The second engine cut off seemed to blow out much methane, and a fire could be observed, coming from the plumbing in the skirt.

SN10 used the remaining engine to correct the tilt. However, it overcorrected slightly and was not able to correct back, which resulted in a slight lean upon landing. At T+06:12, the landing legs deployed, however only three of them locked in place, while the other three bounced around.[7] In the last few seconds, SN15 didn't decelerate anymore, moving at about 15 mph, and with only three legs working, this might have resulted in the bounce to be observed upon landing at T+06:21, as they weren't able to absorb the impact energy. Additionally, later it could be seen that there was no space left between the pad and the skirt. This could also have lead to the lean. Musk later confirmed that the landing was was way too hard for the legs due to low thrust on the engine.

After landing, the fire could still be seen and the water deluge system tried to bring the situation under control. However, around 10 minutes after touch down, SN10 exploded. It was observed that the explosion came from the oxigen tank. Scott Manley assumed that there was a pressure issue in the LOX tank, leading to a rupture near the thrust puck. The tank split and the pressure made SN10 shoot into the air. The whole incident also caused a failure of the common dome between the LOX and methane tank, leading to the explosion as the two came in contact. As the blast was assymetrical, Sn10 flipped over again.

Although SN10 was destroyed after landing, it demonstrated the progress of the program. It showed that Starship is capable of manoeuvre itself back to the landing pad and making a vertical landing. However, it also showed that the landing legs still need clear improvement.

### Timeline

Timeline according to several sources:

* Elon Musk tweeted
* 07:06 Man lift going up
* 07:25 Road block installed
* 08:00 Village cleared
* 08:23 First weather balloon up
* 08:43 Man lift coming down, probably FTS activated
* 09:00 TFR activated
* 09:10 Pad cleared
* 09:16 RCS thrusters testing
* 09:20 Some grass vent (no countdown indication)
* 09:22 Flap testing
* 09:32 Cars left the road block
* Some clouds moved in, unclear whether they affected countdown; some minor farm (LOX) venting from time to time
* 10:22 Second weather balloon up
* 10:44 Satellites moved down, weather improved a bit
* 10:49 Flaps extended again, some flap testing
* 11:48 Recondenser, car passed sentinel cam (a LabPadre camera), Ground vent some seconds later
* 11:52 Some cars left at sentinel cam
* 11:52 Tank farm activity
* 12:21 Cars headed to pad; people at the tank farm
* Stuck ground vent valve according to Michael Sheetz: "SpaceX is still looking to launch Starship SN10 today but had a ground vent valve stuck open when propellant load was about to start, sources tell CNBC."[8]
* 13:06 Cars left pad again; recondenser still venting sporadically
* 13:19 Ground farm venting taking up again, as well as ground vent
* 13:31 Propellant loading, skirt vent (difficult to spot this day)
* 13:48 Small methane vent
* SpaceX is currently targeting Starship SN10 liftoff at about 3:14 p.m. ET, sources tell CNBC. [Michael Sheetz]
* 14:02 Tri-Vent, Engine Chill
* 14:04 Condensation
* 14:10 Aft flap vent
* 14:14 Ignition of all three [?] engines, auto-abort at -00:00.1, rapid depress, safing the vehicle, evaluating next attempt opportunity
* 14:32 John Innsprucker telling that they could do a reattempt in around 2 hours
* 14:39 Elon tweeted; abort due to slightly conservative high thrust limit
* 16:22 Recondenser, Ground vent
* 16:23 Tank farm venting
* 16:33 Skirt vent, propellent loading
* SpaceX is targeting 6:13pm ET for today's last launch attempt, per sources. [Joey Roulette]
* 16:48 Methane vent
* 17:02 Tri-vent, engine chill
* Hold at t-00:10 for a few seconds
* 17:14:*37* Lift off
* 17:20:55 Landing, bounced upon landing; Fire under skirt
* 17:31 RUD, explosion after a fire upon landing
* 17:36 Satellites up
* "It was there and now it's gone" (Tim Dodd)

Flight timeline according to SpaceX stream:

* -05:24 Stream started
* -01:00 Short hold
* -00:00.9 Ignition
* -00:00 Lift off
* +01:08 Venting started
* +02:15 Engine shut down #1
* One engine violet, other orange???
* +03:13 Engine shut down #2; "switch to header tank for one engine"
* +04:20 Flip to horizontal
* +05:47 Tri-vent started (engine chill)
* +05:59 First engine reignited
* +06:00 Other two engines reignited
* +06:07 Two engines shut down
* +06:21 Touch down
* +06:29 Countdown hold

### FAA

Statement from the FAA, according to Christian Davenport:

> The FAA says it "will oversee the SpaceX investigation" of the "Starship SN10 prototype mishap... All debris appears to have landed within the designated hazard area and the company reports no injuries or public property damage."[9] The FAA will approve "any corrective actions SpaceX must take before return to flight is authorized." The probe would "validate that the safety systems performed as designed and that the analysis of public risk was accurate. It also will determine the root cause of the mishap."[10] These tend to go somewhat quickly, so I'd be surprised if there was an impact to the SN11 schedule.[11]
>
>

He later added, that "the FAA found 'no public safety concerns in the preliminary SN10 mishap report that would preclude further launches.' As a result, the FAA 'approved the license modifications for SN11 and authorized its flight.'"

## References

1. ↑ https://twitter.com/elonmusk/status/1364473175279620096
2. ↑ https://www.spacex.com/vehicles/starship/index.html
3. ↑ https://twitter.com/elonmusk/status/1368016384458858500
4. ↑ https://twitter.com/elonmusk/status/1368048822534868997
5. ↑ https://twitter.com/elonmusk/status/1369379914139451406
6. ↑ https://twitter.com/elonmusk/status/1369382210894237705
7. ↑ https://twitter.com/elonmusk/status/1369438991943151620
8. ↑ https://twitter.com/elonmusk/status/1369458403248988160
9. ↑ https://twitter.com/elonmusk/status/1369489056350883840
10. ↑ https://twitter.com/wapodavenport/status/1371807622609920003