SN11

SN11 was the fourth fully assembled Starship prototype to undergo flight testing. It marked the final prototype of the initial four, as Elon Musk announced significant changes for SN15 and the cancellation of SN12-14.

Musk revealed that for future flights, they would utilize at least two engines for the entire descent and reignite the third engine if any issues arose. It was anticipated that SN10 would employ two engines for the descent, initially reigniting all three and then immediately shutting down one if all were functioning properly, in order to avoid the complications experienced by SN9. However, during SN10's flip back to horizontal and deceleration, all three engines were initially used but then two were shut off. Unfortunately, the last engine did not generate sufficient thrust, despite being commanded to produce more, resulting in a harsh impact. In response, Musk declared that "multiple fixes" were being worked on for future prototypes.

Shortly after reigniting the engines, SN11 encountered a problem that led to an imminent explosion (RUD). Consequently, the prototype was unable to sustain the rapid progress that SpaceX had successfully demonstrated with previous test flights. Nevertheless, setbacks had been anticipated during the early testing phase of an entirely new rocket design.

One of the primary objectives of these initial test flights was to gather data on the controlled descent using the flaps, which they undoubtedly achieved with all four prototypes.

## FAA

On 16 March 2021, Christian Davenport posted information 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.'"

## Timeline

* 03 Feb 2021: Nosecone welding continued
* 04 Feb 2021: Both nosecone sections welded togehter (fins already attached)
* 05 Feb 2021: Tank section moved from Mid Bay into Highbay (big area covered with heat shield tiles, no aft fins installed yet)
* 07 Feb 2021: Nosecone section moved to highbay and stacked on top of tank section
* 11 Feb 2021: SN11 removed from crane and then rotated in the high bay
* 11 Feb 2021: First aft flap installed
* 15 Feb 2021: Second aft fin awaiting to be installed
* 16 Feb 2021: Second aft fin installed
* 04 March 2021: Access stairs moved to pad B, Bluto/Tankzilla moved to launch pad and arrived at noon
* 05 March 2021: Preparations for roll out
* 06 March 2021: Bluto/Tankzilla moved next to pad B
* 07 March 2021: SN11 and BN1 changed places in high bay
* **08 March 2021: Roll out to pad B**, 3 raptors confirmed
* **09 March 2021: Ambient temp pressure testing**
* 10 March 2021: Aborted test
* **11 March 2021: Cryo proof test**
* **12 March 2021: Scrubbed static fire attempt**
* 13 March 2021: Work on aft section and other parts, access hatches opened
* 14 March 2021: Venting at 03:47:30 am
* 15 March 2021: FAA aproval
* **15 March 2021: Static fire #1, assumed abort after ignition**
* 20 March 2021: Flaps/fins tested
* 21 March 2021: RCS thrusters tested, FTS installed
* **22 March 2021: Static fire #2**
* **23 March 2021: Pressure test, vents**
* 24 March 2021: Raptor removed and moved to the build site at 5am for repairs
* 25 March 2021: Work on SN11 near access hatch
* 25 March 2021: RSN46 delivered and installed
* **25 March 2021: Single engine static fire**
* **26 March 2021: Scrubbed flight attempt**
* 26 March 2021: Monday said to be next flight attempt
* **29 March 2021: Scrubbed flight attempt**
* **30 March 2021: Flight and RUD**
* 31 March 2021: Wreckage inspected and clean up; raptors landed near SH, legs spotted damaging the roof of an ATV
* 03 Apr 2021: Wreckage cleanup continued
* 05 Apr 2021: Still alot of debris lying around
* 06 Apr 2021: Wreckage cleanup continued, suborbital pads seem cleared
* 11 Apr 2021: Debris still all over the place
* 12 Apr 2021: Debris still being cleand up
* 17 Apr 2021: Debris still lying around SoLS, later compacted into dumpster
* 18 Apr 2021: Debris field still not fully cleared
* 29 Apr 2021: Debris cleanup continued
* 11 May 2021: Cleanup continued
* 20 May 2021: Wreckage still not fully cleaned up
* 29 May 2021: Wreckage cleanup, some still lying around

## 08 March 2021 - Roll out

It was observed that the three raptors have allready been installed.

SN11 was inspected quite some time before turning into the road. Also, the process fo lowering and securing the Starship onto the pad took several hours. In contrast to the earlier prototype, a square cover could be observed on the nosecone barrel section. Some suggested it could be some sort of ballast or counter weight used for stacking that they didn't take off yet.

Rough timeline:

* Initial road closure: 9am-11.30am
* 09:03 Started rolling
* 13:13 Turned into launch site
* 15:10 SN11 lifted, later legs have been deployed and tested
* 17:11 Final lift to pad B

## 09 March 2021 - Ambient Testing

Timeline according to LabPadre Stream:

* 16:36 Car at hard checkpoint
* 17:33 Road closed
* 18:03 Pad clear
* 19:23 SN11 venting: Ambient test
	+ LOX vent
	+ CH4 vent
	+ both vents
	+ LOX header tank vent
* 20:15 Detank
* 20:15 Road opened

## 10 March 2021 - Aborted Testing

Rather high winds this day.

Timeline according to LabPadre Stream:

* 13:52 Road closed
* 14:44 Pad clear
* 15:17 Some Venting at the tank farm
* 16:33 Cars at pad
* 16:43 Ground vent
* 17:05 Man lift went up
* 17:37 Road opened

## 11 March 2021 - Cryo Testing

Timeline according to LabPadre Stream and NSF:

* 13:28 Road closed
* 15:44 Pad clear
* 17:55 Ground vent
* 18:05 SN11 vent, LN2 loading began
* 18:08 Frost, ice ring; continous venting
* 18:22 LOX tank frost ring appearing, frost continuosly increasing
* 19:31 Raptor Chill, later frost disappear
* 20:06 RCS Tests
* 20:11 CH4 frost ring appearing, LOX frost/condensation [?] slowly disappearing
* 20:56 Detank with big doule vent
* 21:04 Road opened

## 12 March 2021 - Scrubbed Static Fire attempt

Timeline according to LabPadre Stream:

* 07:52 Road closed
* 13:16 Road opened

According to NSF author Chris Bergin, this attempt was scrubbed due to GSE issues.

## 15 March 2021 - Static Fire #1 (abort after ignition)

Timeline according to LabPadre and NSF stream:

* 06:20 Road closed
* 09:50 Pad cleared
* 09:52 Ground vent
* 11:51 (11:46?) Recondenser
* 11:52 Farm vent
* 12:02 SN11 vent (methane)
* 12:02? Skirt vent
* 12:14:42 Engine chill (tri-vent)
* 12:26:35? Preburner or scrubbed sf attempt as raptors only fired very short [?]
* 12:28 Depress
* 13:48 Road opened

## 22 March 2021 - Static Fire #2

Timeline according to LabPadre and NSF:

* 06:21 Road closed
* 07:16 Pad cleared
* 08:02 Ground vent
* 08:14 Recondenser
* 08:23 Farm vent
* 08:30 Methane vent
* 08:32 Skirt vent started
* 08:42 Other, bigger methane vent
* 08:44 Vent from aft
* 08:44:35 Tri vent (NSF time, Nerdle time +7-8 seconds)
* 08:54 Nosecone vent, LOX header tank frost
* 08:56:30 Static Fire (some 2 seconds) [Nerdle time: 08:56:13 small pause, 08:56:38 SF], no usual pulse observed
* 08:57:42 Depress vent
* 09:11 Some skirt vent
* 09:23 Depress vents
* 09:46 Satellite up
* 10:38 Road opened

## 23 March 2021 - Pressure test

Timeline according to LabPadre:

* 11:40 Beach closed, road block up
* 11:51 Road closed
* 12:15 GSE testing
* 12:30 SN11 vent

## 25 March 2021 - Static Fire #3 (single engine)

Timeline of the early morning single engine static fire in order to test the replaced raptor:

* 06:47 Road closed
* 07:00 Pad cleared
* 07:20 Ground vent
* 07:25 Recondenser
* 07:37 Farm vent
* 07:44 SN11 venting
* 07:49 Engine chill (single), side vents only a few minutes after
* 08:00 Siren
* 08:09:14 Static fire (full duration, probably single engine)
* 08:10:18 Depress vents
* 08:25 Header tank frost
* 08:42-46 Detank vents (Methane, LOX, LOX header)
* 08:47 GSE vent plume
* 08:51 Top flaps folded
* 09:48 Cars to pad

## 26 March 2021 - Scrubbed flight attempt

### Timeline

* Early morning: Access hatch closed
* 03:44 Flap tests
* Later: RCS tests
* Static fire: see below
* 10:10 Mary told to evacuate by noon
* 10:28 Lifts going up under SN11
* Water poured on dirt around landing pad
* 11:21 Lifts going down
* 13:10 Lifts going up, possibly to activate FTS
* 14:22 Lift 1 going down
* 14:35 RC cancelled
* 14:48 Lift 2 going down

### Official SpaceX information

As early as Friday, March 26, the SpaceX team will attempt a high-altitude flight test of Starship serial number 11 (SN11) – our fourth high-altitude flight test of a Starship prototype from Starbase in Texas. Similar to previous high-altitude flight tests of Starship, SN11 will be powered through ascent by three Raptor engines, each shutting down in sequence prior to the vehicle reaching apogee – approximately **10 km** in altitude. **SN11 will perform 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 will descend under active aerodynamic control, accomplished by independent movement of two forward and two aft flaps on the vehicle. All four flaps are actuated by an onboard flight computer to control Starship’s attitude during flight and enable precise landing at the intended location. SN11’s Raptor engines will then reignite as the vehicle attempts a landing flip maneuver immediately before touching down on the landing pad adjacent to the launch mount.

A controlled aerodynamic descent with body flaps and vertical landing capability, combined with in-space refilling, are critical to landing Starship at destinations across the solar system where prepared surfaces or runways do not exist, and returning to Earth. This capability will enable 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.

There will be a live feed of the flight test available here that will start a few minutes prior to liftoff. Given the dynamic schedule of development testing, stay tuned to our social media channels for updates as we move toward SpaceX’s fourth high-altitude flight test of Starship!

### Outcome and analysis

Possibly scrubbed due to hazy weather. There could also have been technical issues (FTS?). According to musk, additional checkouts were needed as they do their best to land and fully recover. They will probably try again on Monday.

## 29 March 2021 - Scrubbed flight attempt

### Timeline

* before 07:00 fwd flaps unchained
* 10:17? Road closed
* 10:15 - 10:20 Flaps moved and extended
* 10:32 - 10:38 Flaps tested
* 10:33 Musk tweet: "FAA inspector unable to reach Starbase in time for launch today. Postponed to no earlier than tomorrow."
* 11:02 Road opened

### FAA

Michael Baylor asked a statement from the FAA:

"On March 12, the FAA revised the SpaceX Starship license to require an FAA safety inspector to be present at the Boca Chica site for every flight. This is the result of FAA's continuing oversight of SpaxeX to ensure compliance with federal regulations to protect public safety, including issues arising form the SN8 launch in December 2020. SpaceX mus provide adequate notice of its launch schedule to allow for a FAA safety inspector to trave to Boca Chica."

The issue according to Christian Davenport: (also reported by Joey Roulette)

"Here’s how the Starship/FAA-inspector thing went down, according to a person familiar: The inspector was in Boca last week, waiting for SpaceX to fly. It didn't, and he was told SpaceX would not fly Monday (today) or possibly all of this week bc it couldn’t get road closures. So he went home to Fla. On Sunday, SpaceX was able to get road closures and they emailed the inspector to come back. But he didn’t see the email. Finally SpaceX got through to officials on the phone late Sunday night, but by then it was too late to get someone there by today. In an attempt to be more efficient, the FAA has been waiting for SpaceX to complete a static fire, before sending the inspector so that he isn’t just waiting around. But it’s a fast-moving test program, and they’re swapping out engines and making changes on the fly. And so the FAA put in its statement that SpaceX “must provide adequate notice of its launch schedule.”

He also added: "The good news is the FAA inspector was scheduled to arrive in Boca Chica this evening. So SpaceX Starship SN11 should be good to go tomorrow."[1]

## 30 March 2021 - Flight

### Timeline

Difficult to tell due to much fog:

* Tracking to a potential 8am liftoff (Elon Musk)
* According to Mary: RC and evacuation both scheduled for 7am
* 06:19? Road closed
* 06:25 Pad clear in 5min according to SPadre
* 07:05 Pad clear (LabPadre)
* 07:13 Ground vent/Tank farm venting (supposed by NSF)
* 07:22 Recondenser (LP)
* 07:23 Farm vent (LP)
* 07:37 Vents seen as fog began to clear
* 07:40 Possibly tri-vent seen (NSF)
* SpaceX stream slated for 07:50
* 07:45 Engine chil, tri-vent (LP)
* 07:50 Huge vents heard
* 07:52 Possibly on hold as SpaceX stream not yet live
* 07:54 SpaceX stream started
* 07:56:30 T-4:00 according to SpaceX stream
* 07:58:30 T-1:54
* Lift off at around 08:00:05 (LP)
* 08:06:12 RUD according to LabPadre Launch Pad cam
* 09:27 Truck back to pad

### Timeline according to SpaceX stream

* T-02:00 Propellant loading completed (LOX, LCH4)
* T-01:00
* T-00:42 Retracting quick disconnect
* T-00:00.8 Ignition
* T+00:00.0 Lift off
* T+00:31 CH4 tank and downcomer view
* T+00:41 1km altitude
* T+01:53 4km altitude
* T+02:11 Engine shutdown #1
* T+03:xx Past 8km, continue to climb
* T+03:1x Engine shutdown #2
* T+03:56 10km altitude
* T+04:1x Engine shutdown #3
* T+04:51 View of horizontal descend. 6km altitude
* T+05:13 Engine chill
* T+05:33 2km altitude
* T+05:44 1km altitude
* T+05:48 Engine #1 ignition
* T+05:49 Camera freeze, RUD!!, timer stopped
* Sound of destuction
* "Looks like we've had another exciting test of Starship number 11. A reminder again, this is a test series to gather data on entry of the Starship vehicle at subsonic speeds as it comes back to the landing zone. It does appear though that another exciting test as we say..."

### Elon Musk statements

Elon Musk released the following statements after the flight:

"A high production rate solves many ills"[2], they will be able to move on with SN15 rather soon, so the RUD isn't this bad

"At least the crater is in the right place!"[3], indicating that SN11 landed on the landing pad, which is the best possible place for a RUD as it is protected by earth walls.

"Looks like engine 2 had issues on ascent & didn’t reach operating chamber pressure during landing burn, but, in theory, it wasn’t needed. Something significant happened shortly after landing burn start. Should know what it was once we can examine the bits later today."[4] As there is redundancy with the landing burn (they only need 2 out of 3 engines), one engine problem shouldn't be any problem. So there evidently was another additional problem.

"SN15 rolls to launch pad in a few days. It has hundreds of design improvements across structures, avionics/software & engine. Hopefully, one of those improvements covers this problem. If not, then retrofit will add a few more days."[5] This would be faster than many expected as SN15 was still not finally stacke at this time, unlike with previous test flights, where the next prototype was already ready.

"Ascent phase, transition to horizontal & control during free fall were good. A (relatively) small CH4 leak led to fire on engine 2 & fried part of avionics, causing hard start attempting landing burn in CH4 turbopump. This is getting fixed 6 ways to Sunday."

### Analysis

The flight itself went as expected, although not much was seen as most ground camera views were ostructed by fog. However, engine two had problems already upon ascend and didn’t reach operating chamber pressure during landing burn (see above). As Starship only needs two engines to reignite for landing, this should not pose any difficulties.

From the SpaceX stream, the reignition of engine #1 was confirmed, however it remained unclear whether any other engine tried to relight as the count stopped one second after. The explosion must have occured shortly after that. The only source for further analysis was the debree field which was, compared to the other prototypes, very large. Based on RGV flyover pictures, several pieces were identified: The nosecone remained largely in one piece. Near Starhopper, the three raptor engines were spotted closely together, indicating that they might have landed together. The debree field was mostly scattered to the north, mostly small pieces spread out over a large are, so the whole tank section seems to have exploded, possibly from inside. If there would have been a problem with the engines themselves, the oxigen bulkhead would have failed, leaving the tank largly intakt until it would have landed, which in turns wouldn't lead to such a large debree field (see SN1 and SN10). Some also suggested that the FTS has been triggered, something insider information denies.

One very light part of insulation material has been found in populated area. Likely it came off at apogee.

## References

1. ↑ https://twitter.com/wapodavenport/status/1371807622609920003
2. ↑ https://www.youtube.com/watch?v=CVUCn\_oTQOk
3. ↑ https://www.nasaspaceflight.com/2021/03/starship-sn11-spacex-orbital-flight-summer/#more-76751
4. ↑ https://www.spacex.com/vehicles/starship/index.html
5. ↑ https://twitter.com/elonmusk/status/1375545176324734978
6. ↑ https://twitter.com/elonmusk/status/1376558233624666120
7. ↑ https://twitter.com/elonmusk/status/1379022709737275393
8. ↑ https://www.youtube.com/watch?v=MoEv0dkWlvA