Starship 4/20

This article is about the full stack only. For the individual prototypes, see SN20 and B4.

## Starship 4/20

### Status

Retired | Ship and Booster in Rocket Garden

## Starship development

### See also

S20 and B4, Starship 9/25

Starship 4/20 is the first fully stacked Starship prototype, consisting of booster 4 (B4) as the first stage and ship 20 (S20) as the second (upper) stage. The first time the rocket has been fully stacked was on August 6, 2021. On February 09-10, 2022, the two prototypes were stacked for a second time ahead of Elon Musk's Starship presentation. This time, the chopsticks were used for lifting ship 20, while booster 4 was lifted by the LR11000X crane.

## History

On February 3rd, Elon Musk announced the long awaited starship update for which he assured there will be a full stack of booster 4 and ship 20. This comes six month after a first fit check of the two prototypes on the orbital launch mount on August 6th, 2021, six month of major upgrades both to the vehicles and the launch site ("Stage 0"). While they used the Liebherr LR11350 crane back then, SpaceX was now expected to test the newly built infrastructure of the orbital launch site for stacking.

The "chopsticks", intended not only for stacking, but also for catching boosters and possibly ships, have been tested in the past month using water bags to simulate the mass of Starship. For stacking booster 4 onto the orbital launch mount however, SpaceX used its own LR11000 crane. This operation was conducted smoothly on February 6th.

The stacking of ship 20, for which the chopsticks had to be used as no crane was tall enough, was delayed a few days due to bad weather conditions. Preparations finally started on February 8th. Bumpers on the QD arm were removed, lifting pins were installed on the chopsticks, S20 got disconnected from the pressurisation system of the transport stand and moved into the arms of the chopsticks. In the following morning, the pad was cleared for some proof testing of ship 20. After that, the whole launch site was closed ahead of stacking operations. After midnight, ship 20 was finally stacked onto booster 4, marking the second time SpaceX has assembled the whole rocket and the first time making use of the launch site infrastructure.

## Timeline

* 04 Aug 2021: B4 lifted onto OLM by LR11350 in a very careful manoeuvre
* **06 Aug 2021: SN20/S20 stacked onto B4 by LR11350, fully assembled rocket for the first time ever**
* 06 Aug 2021: SN20/S20 removed from B4 by LR11350 after first fit check for final construction, touch-down at 9:45 am
* 07 Aug 2021: B4 reattached to LR11350
* 10 Aug 2021: B4 removed from OLM at 7:45 am by LR11350; detached from crane/load spreader at 3:06 pm
* 06 Feb 2022: B4 Lifted onto OLM by LR11000X [not chopsticks as suspected]
* **08-10 Feb 2022: S20 stacked onto B4 for second full stack ahead of Elon Musk's Starship Presentation; lifted by chopsticks for the first time**
* 11 Feb 2022: Cryo proof test

## 08-10 February 2022 - Stacking

### Background and Stacking

On February 3rd, Elon Musk announced the long-awaited starship update for which he assured there would be a full stack of booster 4 and ship 20. This comes six months after a first fit check of the two prototypes on the orbital launch mount on August 6th, 2021, six month of major upgrades both to the vehicles and the launch site ("Stage 0"). While they used the Liebherr LR11350 crane back then, SpaceX was now expected to test the newly built infrastructure of the orbital launch site for stacking.

The "chopsticks", intended not only for stacking, but also for catching boosters and possibly ships, have been tested in the past month using water bags to simulate the mass of Starship. For stacking booster 4 onto the orbital launch mount however, SpaceX used its own LR11000 crane. This operation was conducted smoothly on February 6th.

The stacking of ship 20, for which the chopsticks had to be used as no crane was tall enough, was delayed a few days due to bad weather conditions. Preparations finally started on February 8th. Bumpers on the QD arm were removed, lifting pins were installed on the chopsticks, S20 got disconnected from the pressurisation system of the transport stand and moved into the arms of the chopsticks. In the following morning, the pad was cleared for some proof testing of ship 20. After that, the whole launch site was closed ahead of stacking operations. After midnight, ship 20 was finally stacked onto booster 4, marking the second time SpaceX has assembled the whole rocket and the first time making use of the launch site infrastructure.

### Stacking timeline

08 February

* 07:04 bumpers on ship QD arm removed by LR11000X
* New starship lifting pins installed on chopsticks
* 12:15 S20 disconnected from presurization system (stand QD)
* 15:00 Stabilization claws holding onto B4
* 17:42 S20 slightly moved away from cryo mount
* 20:13 Chopsticks arms opened slightly, S20 SPMT raised for transport
* 20:14-20:36 S20 moved towards chopstics and into position between chopsticks
* 21:38 Chopsticks moved upwards to the lifting points of S20

09 February

* 03:51 Pad announcment: "We are 15 minutes from clearing the orbital pad for ship proof"
* 05:08 Intermittent RC (Starship Gazer remained on beach site)
* Venting noised, from SoLS and from OLS tank farm
* 06:43? Road opened
* 09:15 Lift up to top of booster
* 9:32 Sheriff closing beach and area; Stargazer has to leave
* 9:35 Work on QD clamps (retracted from booster), with welding/cutting; as well as on ship QD
* 10:31 PA: "Attention orbital pad: 30 minutes till pad clear, 30 minutes till pad clear" (Road block not active!)
* 10:36 Road closure? Somewhere on hwy 4 (further down the road than usual)
* 10:45 PA "Attention orbital pad: 15 minutes till pad clear, 15 minutes till pad clear"
* 10:48 Lift down from the top of booster
* 10:54:55 PA: "Attention orbital pad: Pad clear in 5 minutes, pad clear in 5 minutes"
* 10:57 SpaceX car to pad
* 11:05 Sheriff cars to pad
* 11:05 One satellite dish went down
* 11:07 PA "Attention orbital pad: The orbital pad has ????"
* 11:54 Delivery to launch site, turned back
* 12:12 Still a lot of activity around the pad; pad itself might be clear
* 13:00 LN2/LOX delivery
* 13:01 Left chopstick arm slighly opened (from road)
* 13:04 Sheriff cars left entrance
* 13:06 Cars and many people entered pad; box trucks arrived (possibly to set up presentation); Elon Musk as well?
* 13:08 Chopsticks moved down
* 13:14 People on QD arm
* 13:15 Beach opened
* 14:55 sheriff cars to beach
* 14:57 Beach cleared (Ocean cam, SpaceX IMAX cam operator)
* 14:59 PA: "Attention on the pad: Please clear the area directly under the chopsticks; chopsticks ??? will occur in roughly 30 [seconds/mins]"
* 15:02 Lift from B4 top lowered
* 15:10? Left chopstick arm slightly closed again
* 15:12 Sheriff closed road again (a bit above pad entrance)
* 15:15 Right arm closed a bit
* 15:20 Right arm opened slightly
* 15:27 Crew left QD arm
* 15:30 SpaceX police car arrived pad
* 15:31 PA: "Attention orbital pad: We will be stepping into a software deploy, there will be venting from booster, there will be venting from booster!"
* 15:35 Crews back at ship QD arm
* 16:00 **OLM scaffolding has been removed**
* 16:12 OLM cleared
* 16:25-29 QD stabilization arms retracted
* 16:38 PA "Attention orbital pad: **Pressing up booster 4**, pressing up booster 4"
* 16:40 Ship QD arm claws moved into storage position, fully retracted
* 16:42 Lift again at top of B4
* 16:47 Lift moved down again
* 18:18 Elon Musk on pad
* 18:56-57 Chopsticks rose, drone flying
* 18:59-19:00 Chopsticks began to close (spotlight pointed on stabilization extension pins)
* 19:03 Closed slightly more
* 20:40-43 Ship QD arm retracted
* 20:55 Pad cleared?
* **21:22:22 S20 slightly lifted (a few centimeters)**
* 21:32:28 Right stabilization pin moving in quite fast
* 21:38:30 Moved in
* 21:40:19 Moved in more; then moved down to lock in
* 22:00-05? Left stabilization pin moved in as well
* **22:06:23-43 S20 lifted a few feet to clear the transport stand**
* **22:27:30 S20 final lift started; drone accompanied**
* 22:38:31 Lift paused
* 22:43 Lift continued
* 22:44:52 Reached top
* 23:02:45 Swing started / translating S20 over towards B4; stopped and started again
* 23:07:28 Swing continued
* 23:20 S20 arrived over B4, swing stopped
* 23:21-23:50 QD armd swung towards stack
* 23:24:50 Stabilisation claws starded to extend; continued at 27:52
* 23:36 Claws attached to booster, B4 slightly moved during it
* 23:40 S20 very slowly lowering to B4; at some point an interna light has been turned on

10 February

* 00:44 S20 and B4 stacked [exact time not clear]
* Stabilisation pins have retracted at some point
* 01:31 Road opened
* 02:09-23 Ship QD extended towards S20 with own power
* 02:00 cont: New entrance hut delivered and installed

Video of the stacking by Elon Musk:

## 11 February 2022 - Cryo proof test

* 07:13 or earlier: Road closed
* 11:37 Pad cleared
* 11:45 or earlier: Minor venting from between GSE2 and GSE7
* 11:52 Right satellite dish lowered
* 11:53 Venting from between GSE2 and GSE7 increased a bit
* 14:10 Venting noises from unknown source over the next hour
* 15:42 Satellite dish raised
* 15:59 Road opened
* 16:17 Vertical LN2 tank near bunker started to vent

CH4 heat exchangers frosty, as well as LOX and partly CH4 tanks on Ship.

## 14 February 2022 - Destacking

Timeline according to LabPadre (not independently veryfied):

* 08:40 QD arm detached from S20 and B4
* 10:27 Road closed
* 10:52 Pad cleared
* 11:11 S20 has begun lifting off of B4
* 11:37 QD arm retracted
* 12:00 S20 swung clear of B4
* 12:44 S20 touched down on transport stand
* 14:01 Road opened
* 14:15 QD arm moved back into position
* 20:09 S20 detached from chopsticks

Video by Elon Musk:

## 15 March 2022 - Lift & Full stack

On March 15, 2022, Ship 20 was lifted onto B4 for the third time. For the second time, this operation was done by the chopsticks in a much faster process than previously. Timeline according to LabPadre discord:

* 12:34 Road closed
* 18:14 S20 disconnected from transport stand pressurization unit, Ship QD arm swung out of the way
* 18:25 Road closed again?
* 18:42 Chopstick stabilizer pins latched onto S20
* 19:11 Chopsticks started to lift S20
* 20:07 S20 stacked on B4 for the third time
* 21:39 Ship QD plate attached to S20
* 22:10 Road opened

## 16 March 2022 - Starship 4/20 Cryo test

On March 16, 2022, SpaceX conducted a cryo proof test with liquid nitrogen on the full stack. It was the first time the ship QD was active with cryogenics. B4 tanks frosted up partially and S20 tanks got condensation. Timeline according to LabPadre discord:

* 13:55 Road closed
* 16:50 Pad cleared
* 17:03 Tank farm venting
* 18:50 OLM and OLIT vents
* 19:23 B4 cryo fill started
* 19:30 B4 frost on CH4 tank started to form
* 20:03 S20 venting (cryo fill)
* 20:24 S20 cryo started
* 20:32 Frost formed on S20 LOX tank
* 21:00 Frost has formed on all 4 main tanks of the full stack
* 21:05 Detank started as frost started to decrease
* 21:44 Large B4 depress vent
* 21:52 Pad opened
* 22:51 Road opened

## 18 March 2022 - Starship 4/20 Propellant load test

On 18 March 2022, a propellant load test was conducted on the full stack for the first time. Unlike a cryo proof test, where only LN2 is used, here the tanks got filled with propellant (CH4/LOX) (according to a SpaceX tweet, however no overpressure notice was issued, so this usually would indicate only LN2/LOX load). The booster 4 LOX and CH4 tanks got frosty, followed by S20 tanks, but only partially. A drone observed the test. Timeline according to LabPadre discord:

* 15:16 Road closed
* 16:03 Pad cleared
* 16:18 OLS tank farm venting
* 17:34 B4 cryo load
* 17:56 Frost formed on B4 LOX and CH4 tanks
* 18:05 S20 cryo load
* 19:19 B4 depress vents
* 20:00 Road opened

## 19 March 2022: - S20 destacked

On 19 March 2022, Ship 20 was destacked by the chopsicks. It was the first operation of the chopsticks during which the road remained open. Timeline according to LabPadre discord:

* 17:35 Ship QD disconected
* 18:40 Ship QD arm retracted
* 20:31 Lifted off B4 by chopsticks
* 22:19 Touched down on transport stand

## References

1. ↑ https://twitter.com/elonmusk/status/1491639263686844418
2. ↑ https://twitter.com/elonmusk/status/1493310083014475778
3. ↑ https://twitter.com/SpaceX/status/1504919503041228802