SpaceX Super Heavy

The fuel tank on the Super Heavy is separated by a common bulkhead, similar to the ones used on the S-II and S-IVB stages on the Saturn V rocket. The oxygen tank has four chines attached. These protect the COPVs, CO2 tanks for fire suppression, as well as providing lift during flight.[4]

The booster's tanks were reported as holding 3,600 t (7,900,000 lb) of propellant, consisting of 2,800 t (6,200,000 lb) of liquid oxygen and 800 t (1,800,000 lb) of liquid methane.[lower-alpha 1] However, current booster prototypes can only hold 3,400 t (7,500,000 lb) of propellant.[5]

The engine section supports the 33 raptor engines during flight. The engines are arranged in three concentric rings.[6] The outer ring of 20 engines is of the "Raptor Boost" configuration with gimbal actuators removed to save weight and a modified injector with reduced throttle performance in exchange for greater thrust.[7] Raptor utilizes a full-flow staged combustion cycle, which has both Oxygen and Methane rich turbopumps.

Prior to 2014, only two full-flow staged-combustion rocket engine designs had advanced enough to undergo testing on test stands: the Soviet RD-270 project in the 1960s and the Aerojet Rocketdyne Integrated Powerhead Demonstrator in the mid-2000s.

At full power, all engines produce a collective 75.9 MN (17,100,000 lb_f) of thrust.[8] However, Raptor 3 is planned to bring thrust up to 90 MN (20,000,000 lb_f).[9]

The interstage is also equipped with four electrically actuated grid fins, each with a mass of 3 t (6,600 lb). Adjacent pairs of grid fins are only spaced sixty degrees apart instead of being orthogonal (as is the case on Falcon 9) to provide more authority in the pitch axis. Unlike Falcon 9, the grid fins do not retract and remain extended during ascent.[3] During unpowered flight in the vacuum of space, control authority is provided by cold gas thrusters fed with residual ullage gas.

The interstage also has protruding hardpoints, located between grid fins, allowing the booster to be lifted or caught by the launch tower.[10]

After the first Starship test flight, all boosters will now have an additional 2m tall vented interstage added, as well as a protective dome. Elon Musk has indicated this change may gain an additional 10% payload to orbit as a result.[11]

BN1 was the first Super-Heavy Booster prototype, a pathfinder that was not intended for flight tests.[30] Sections of the ~70 m (230 ft) tall test article were manufactured throughout the fall. Section stacking began in December 2020.[31] BN1 was fully stacked inside the High Bay on 18 March.[32] On 30 March 2021, BN1 was scrapped.

BN3 (Booster 3)[33] was used for ground tests. A cryogenic proof test was completed (13 July 2021).[34][35] Booster 3 completed stacking in the High Bay (29 June 2021),[36] and moved to the test pad without engines.[37] Three engines were subsequently added.[38]

A static fire test was conducted 19 July 2021.[20] BN3/Booster 3 was partially scrapped on 15 August 2021, while the LOX tank remained welded to the Test Stand.[21] The LOX tank was taken off the Test Stand on the 13th January 2022.[39]

Booster 4 first became visible on 3 July 2021. Musk ordered several hundred SpaceX employees at Hawthorne to relocate to Boca Chica to accelerate the development of SN20, BN4, and the Orbital Launch Platform[38] in an attempt to put the Starship system on the pad by 5 August 2021.[40] BN4 was fully stacked on 1 August, with a full complement of 29 engines[41] installed on 2 August 2021. Grid fins were added to support atmospheric reentry testing.

SN20 was stacked on top of Booster 4 on 6 August 2021 for a fitting test, making it the largest rocket ever.[42] Booster 4 was then returned to the High Bay for secondary wiring. On 9 September 2021, Booster 4 came again to the launch site on top of the Orbital Launch mount.[43]

B4 completed its first cryogenic proof test (17 December 2021),[44] and a pneumatic proof test (19 December 2021). It underwent another cryogenic proof test and a full-load cryogenic proof test. B4 and Ship 20 were then retired.[35]

Parts for B5 were observed as early as 19 July 2021.[24] Stacking for BN5 completed in November, although on 8 December 2021, B5 retired to stand alongside SN15 and SN16.

Parts for B7 were first spotted on 29 September 2021. B7 was placed on the orbital launch mount on 31 March 2022. After completing a cryogenic proof test on 4 April 2022, it was placed onto the new booster test stand on 8 April 2022. B7 completed another cryogenic test on 14 April 2022, but the downcomer suffered a failure and ruptured. On 18 April 2022, B7 returned to the production site for repairs. On 5 May 2022, B7 was again placed on the orbital launch mount. B7 then completed two cryogenic tests on 9 and 11 May 2022. It was then returned back to the production site and entered the new Mega Bay (also known as Wide Bay or High Bay 2), for repairs and additional equipment, upgraded grid fins and engines, and two more 'chines' or 'strakes' (triangular structures placed on the aft section to aid in aerodynamic control).[45] B7 went through more testing (11 July 2022) where it experienced an anomaly during an attempted 33 engine spin prime test and a detonation occurred underneath the engines.[46] The booster then rolled back to the Mega Bay.[47] B7 was transported back to the orbital launch pad with 20 outer Raptor engines (August 4 to August 5, 2022)[48] and completed its first single engine static fire test (August 9, 2022). B7 completed a 20-second static fire (August 11, 2022), the longest static fire on a Starship prototype to date.[49] Following a successful set of tests, it returned to the production site to receive the remaining 13 engines.[50] B7 was lifted back onto the launch mount using the chopsticks catching and lifting system (23 August 2022).[51] It underwent further testing including its 13 inner engines (26 August 2022). B7 completed a multi-engine static fire (31 August 2022).[52] This was followed by multiple spin prime tests,[53][54][55] and a seven-engine static fire on 19 September 2022.[55] B7 again returned to the Mega Bay on 21 September 2022.[56] After upgrades it was again lifted on the launch pad (8 October 2022).[57] Ship 24 was then stacked on top B7 (12 October 2022)[58] and was removed after completing multiple cryogenic load tests.[59][60][61] B7 then completed a spin prime test of multiple engines, (12 November 2022)[62] and afterwards a 14 engine static fire test, (14 November 2022)[63] and finally an 11 engine static fire in an autogenous pressurization test (29 November 2022).[64] On December 9, 2022, B7 rolled back to the Mega Bay[65] for further shielding. In January 2023, Booster 7 was rolled back to the launch site where it was stacked with Ship 24 on the OLM for partial and full Wet Dress Rehearsals (Jan 23[66]) before Ship 24 was destacked and sent to the Rocket Garden for final TPS work. On February 9, 2023, Booster 7 attempted a 10 second duration 33-engine static fire where 31 of the 33 engines successfully fired for the full duration. One of its engines was disabled just prior to testing, and one engine shutdown prematurely. On April 20, 2023, it was intentionally destroyed in the SpaceX Starship Integrated Flight Test after spinning out of control. [67]

The first part of the booster, the engine thrust puck, was spotted on October 5, 2021. Other parts for B8 were observed on February 3, 2022.[68] The booster was fully stacked on July 8, 2022.[69] It travelled to the launch site on 19 September 2022.[70] Booster 8 was scrapped soon after in favor of Booster 9, Booster 8's HPU's were placed on Booster 7 along with other parts.

The engine thrust puck of the booster was first spotted on October 24, 2021. The vehicle finished stacking in late 2022, and was moved to the OLS cryo station on December 15, 2022. Two cryogenic proof tests were conducted on December 21, 2022, and December 29, 2022, both of which were successful. The booster was rolled back to the Mega Bay on January 10, 2023. Among many other upgrades, Booster 9 is the first to feature an electric Thrust Vector Control (often abbreviated to ETVC) gimbaling system of the raptor engines. This system replaces the hydraulics HPU's that were used until Booster 8. Booster 9 is currently slated to fly with Ship 25 on the second Integrated Flight Test. On July 20, Booster 9 was rolled out to the launch site. Later, in the night of July 20 to July 21, it was lifted onto the Orbital Launch Mount in preparation for its testing campaign.[71] On July 23 Booster 9 performed a cryogenic prof test on the orbital launch mount.[72] This was followed by a Spin Prime on August 4, 2023. On August 6, 2023, Booster 9 fired 29 engines for 2.7 seconds, instead of the planned 33 engines for 5 seconds. It was then moved off of the Orbital Launch Mount, and rolled back to the Mega Bay, where it's hot staging extension was added on August 16, 2023.[73] B9 was moved back onto the Orbital Launch Mount on August 22, 2023, and underwent another spin prime test the next day.[74] On August 25, 2023, Booster 9 underwent a static fire of all 33 engines, lasting around 6 seconds. Two engines shut off early during the test.[75][76] On September 5, 2023, S25 was lifted onto B9 for the first time. On September 14, 2023, S25 was removed from B9, followed one week later by the Vented Interstage. On September 26, 2023, the Vented Interstage was lifted onto B9, only to be removed on October 9, 2023. It was lifted back onto B9 on October 16, 2023, along with S25.[77] S25 was removed on October 17, 2023, and then lifted back onto B9 on October 20, 2023. On October 22, 2023, B9 underwent two partial cryogenic tests, while S25 was not tested. This was followed by a deluge test, also on October 22, 2023.[78] On October 24, B9 and S25 completed a WDR[79], which was followed by another deluge test on the same day.[80]

Grid fins and corrugation on Booster 10’s forward 13 sections (right, foreground), March 12, 2023

Not much is known about boosters 10 and 11, except that they also use booster 9's ETVC, as well as elliptical domes.[81] B10 was fully stacked in March 2023.[82] In June 2023, B11 was fully stacked, and B12 began assembly.[83] On July 19, 2023, B10 underwent a cryogenic proof test. It was later moved to the rocket garden, and was then moved to the Mega Bay. However, on September 10, 2023, B10 was moved back to Masseys on a Thrust Simulator Stand. A croygenic test was performed 3 days later.[84] As of September 13, 2023, it is unknown whether the Thrust Simulator was used during the test. It was moved back to the Mega Bay on September 20, 2023, presumably for engine and interstage installation. On October 12, 2023, B11 was moved to the Masseys test site on a Thrust Simulator Stand, where it was cryo tested two days later. It was then tested on October 18, 2023.

Test Tank 1 (TT1) was a subscale test tank consisting of two forward bulkheads connected by a small barrel section. TT1 was used to test new materials and construction methods. On 10 January 2020, TT1 was filled with water and tested to failure as part of an ambient temperature test, reaching a pressure of 7.1 bar (103 psi).[86]

Test Tank 2 (TT2) was another subscale test tank similar to TT1. On 27 January 2020, TT2 underwent an ambient temperature pressure test where it reached a pressure of 7.5 bar (109 psi) before a leak occurred.[93] Two days later, it underwent a cryogenic proof test to destruction, bursting at 8.5 bar (123 psi).[94][88]

GSE 4.1 was first spotted in August 2021, and was the first ground support equipment (GSE) test tank built, made from parts of GSE 4. It underwent a cryogenic proof test (August 23) before it was rolled to Sanchez site.[95] It was rolled back to the launch site in November 2021 and underwent an apparent cryogenic proof test to failure (January 18), where it burst at an unknown pressure.

EDOME is a test tank created to test flatter domes, possibly used on future Starship prototypes. It was moved to the launch site in July 2022, and back to the production site the next month, and never received testing. It was later moved from the production site to the new Masseys site on 22 September 2022, which conducts non-flight hardware testing. On 30 September 2022, it burst during a cryogenic pressure test to failure. After repairs, it was tested to destruction in late October 2022.

BN2.1 was rolled out on 3 June 2021[90] for cryogenic tests (8 June)[96] and (17 June).[97]

B2.1 (not BN2.1) survived three cryogenic tests on 1, 2, and 3 December 2021.[98][99]

B6.1 was originally intended to be the third super heavy intended for flight, but was repurposed as a test tank. In May 2023, it was used to test the modified FTS system, after the FTS on B7 and S24 failed to destroy the vehicle.

B7.1 was first cryogenically proof tested on 28 June 2022,[100] and tested again on 19 July 2022.[101] During a suspected pressurize to failure test two days later, it received minor damage.[102] After repairs, it underwent a fourth cryogenic proof test (27 July), a fifth (1 September), and a sixth five days later. It then rolled back to the production site (16 September). B7.1 left the production site (22 September) to head to the new Masseys site.

Hot Stage Load Head (HSLH) is a test article designed for verify the structural integrity of the interstage of Super Heavy Boosters 9+. It was transported to the Massey's test site on July 30, 2023, before being loaded onto the Can Crusher testing device. As of August 29, 2023, it is believed to have completed testing. In mid October 2023, it was moved back to the production site, presumably for scrapping.