Super Heavy B7

Super Heavy is the first stage of the SpaceX Starship super heavy-lift launch vehicle, which it composes in combination with the Starship second-stage. As of 2023, Super Heavy prototypes are being flight tested. In April 2023, Super Heavy flew for the first time on the first orbital launch attempt of the Starship rocket.

Manufacturing

According to Eric Berger of ''Ars Technica'', the manufacturing process starts with rolls of steel, which are unrolled, cut, and welded along the cut edge to create a cylinder of 9 m (30 ft) in diameter, 1.82 m (6 ft) in height, and 4 mm (0.16 in) thick, and around 1,600 kg (4,000 lb) in mass. These cylinders, are stacked and welded along their edges to form the outer layer of the rocket. Inside, the methane and oxygen tanks are separated by robot-made domes. Before final assembly, grid fins are added to the interstage, and the chines are added after stacking of the propellant tanks.

Design

The first-stage Super Heavy booster is tall, wide, and is composed of four general sections: the engine section, the fuel tank, the oxygen tank, and the interstage. Elon Musk has stated that the final design will have a dry mass between and , with the tanks weighing and the interstage .

Tanks

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 various COPVs on board, as well as providing lift during flight.

The booster's tanks were reported as holding of propellant, consisting of of liquid oxygen and of liquid methane. However, current booster prototypes can only hold of propellant.

Engines

The engine section supports the 33 raptor engines during flight. The engines are arranged in three concentric rings. 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. 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 of thrust.

Interstage

The interstage is also equipped with four electrically actuated grid fins, each with a mass of . 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. During unpowered flight in vacuum, control authority is provided by cold gas thrusters fed with residual ullage gas.

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

In boosters after Booster 7, the top of the interstage will have some form of protection, as well as vents, to allow for hot staging

Mission Profile

About one hour and thirty-nine minutes before flight, the super heavy booster begins propellant load. At the T- 16:40 mark, engine chill begins on the booster. This is to protect the engine's turbopumps from thermal shock. At eight seconds before flight, the thirty-three engines startup-sequence begins.

After liftoff, the engines burn for 169 seconds, at which point 30 of its engines shut off, leaving only three center ones running at 50% thrust. Then, the ship ignites its engines while still attached to the booster and separates. The boostback burn lasts for 55 seconds. About eight minutes to flight, the engines reignite, and the booster is caught by a pair of mechanical arms.

Development

Boosters do not have an engine skirt. Without engines, boosters are about 3 meters shorter.

BN1

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

BN3/B3

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

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

B4

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 in an attempt to put the Starship system on the pad by 5 August 2021. BN4 was fully stacked on 1 August, with a full complement of 29 engines 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. 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.

B4 completed its first cryogenic proof test (17 December 2021), 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.

B5

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

B7

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). 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. The booster then rolled back to the Mega Bay. B7 was transported back to the orbital launch pad with 20 outer Raptor engines (August 4 to August 5, 2022) 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. Following a successful set of tests, it returned to the production site to receive the remaining 13 engines. B7 was lifted back onto the launch mount using the chopsticks catching and lifting system (23 August 2022). It underwent further testing including its 13 inner engines (26 August 2022). B7 completed a multi-engine static fire (31 August 2022). This was followed by multiple spin prime tests, and a seven-engine static fire on 19 September 2022. B7 again returned to the Mega Bay on 21 September 2022. After upgrades it was again lifted on the launch pad (8 October 2022). Ship 24 was then stacked on top B7 (12 October 2022) and was removed after completing multiple cryogenic load tests. B7 then completed a spin prime test of multiple engines, (12 November 2022) and afterwards a 14 engine static fire test, (14 November 2022) and finally an 11 engine static fire in an autogenous pressurization test (29 November 2022). As of 9 December 2022, B7 has rolled back to the Mega Bay presumably for further shielding. Soon Booster 7 was rolled back to the launch site in January 2023 where it was stacked with Ship 24 on the OLM for partial and full Wet Dress Rehearsals (Jan 23) 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 flight after spinning out of control.

B8

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. The booster was fully stacked on July 8, 2022. It travelled to the launch site on 19 September 2022. 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.

B9

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 megabay 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.

B10 and subsequent

Not much is known about boosters 10 and 11, except that they also use boster 9's ETVC. B10 was fully stacked in March 2023. In June 2023, B11 was fully stacked, and B12 began assembly. On July 19, 2023, B10 underwent a cryogenic proof test.

Test tanks

General test tanks

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 .

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 before a leak occurred. Two days later, it underwent a cryogenic proof test to destruction, bursting at .

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.

Super Heavy-based test tanks

BN2.1 was rolled out on 3 June 2021 for cryogenic tests (8 June) and (17 June).

B2.1 (not BN2.1) survived three cryogenic tests on 1, 2, and 3 December.

B6.1 was originally intended to be the third super heavy intended for flight, but was repurposed as a test tank. On May

B7.1 was first cryogenically proof tested on 28 June 2022, and tested again on 19 July 2022. During a suspected pressurize to failure test two days later, it received minor damage. 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.

Ground support equipment-based test tanks

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 (23 August) before it was rolled to Sanchez site. It was rolled back to the launch site in November 2021 and underwent an apparent cryogenic proof test to failure (18 January), where it burst at an unknown pressure.

See also

* List of Falcon 9 first-stage boosters
* Starship HLS, lunar variant of the Starship spacecraft
* SpaceX Starbase, launch site of Super Heavy
* Starlink, large satellite constellation by SpaceX

References

{{SpaceX

SpaceX launch vehicles
VTVL rockets
Proposed reusable launch systems
Reusable spaceflight technology
Reusable launch systems
Rocket stages
SpaceX Starship
SpaceX related lists