The Super Heavy Booster is the first stage of the Starship system. Its primary function is to accelerate and elevate the Ship (second stage) to a higher altitude for more efficient orbital insertion. After completing this ascent, the booster returns to the launch site, where it is captured by the chopsticks and returned to the launch mount. Theoretically, it could be quickly re-used by stacking it with a Starship, launching again, and repeating the process. Currently, the booster is still taken back to the production site for servicing before its next flight, which has not yet occurred.
Versions[]
There are several booster versions: Block 0 never flew, Block 1 flew on Integrated Flight Tests 1 through 8 and is as of February 2025 the version in use, and Block 2 and Block 2 are future upgrades. Some changes in Block 2 & 3 include a new hot stage for Hot Staging, tank stretching and Raptor 3 engines. Elon Musk in a presentation said they will make the Starship a lot longer, so it carries more payload in the future.
Super Heavy Booster "Block 0" (Version 0)[]
Before the Block 1 boosters, there were some boosters with a different engine layout. This includes Booster 4, which had only 29 engines: 1 center engine, 8 inner ring engines (for a total 9 gimballed engines), and an outer ring of 20 engines. They had Raptor 1 engines. These boosters never flew; after delays of the first launch due to regulations, SpaceX chose to fly a newer booster for the first flight test, Booster 7 (Block 1).
Super Heavy Booster Block 1 (Version 1)[]
See also: Ship/Versions
Block 1 boosters are as of February 2025 the currently used boosters. The were used on IFT 1 to 8, and on IFT 7 and IFT 8 together with a Block 2 ship. They have 33 engines, 3 center engines, 10 inner ring engines (both gimballed) and 20 outer ring engines. Thus, an additional 4 engines were added from Block 0. They have Raptor 2 engines.
Stage separation was initially planned as a tilting maneuver of the stack using the booster engines, where booster and ship would separate by themselves. Apparently there were issues with this, and instead hot staging was chosen. A hot staging ring was build for the second flight test (IFT-2), which attaches to the top of the booster. Stage separation via hot staging at the 2. flight test (Booster 9 and Ship 25) was then successful.
Super Heavy Booster Block 2 (Version 2)[]
The Block 2 (or Block 2) Super Heavy booster will feature significant changes compared to Block 1 (or V1). One change is that the hot staging ring will now be directly integrated into the vehicle, instead of being an add-on ring as in Block 1. There will be a significant redesign of the grid fins used to guide the vehicle during descent, which will now be spaced 90 degrees apart, rather than the current 60 degrees apart. Additionally, the engine type will switch to Raptor 3, which removes the need for secondary engine shielding, further reducing mass and increasing payload to orbit. There may be as many as 35 engines on the Block 2 Super Heavy booster. The engines will be arranged in a similar pattern to Block 1, but with 5 engines in the center, as opposed to 3. Additional changes are also expected, but as of December 2024, no confirmed hardware for Block 2 Super Heavy boosters have been spotted yet, although it has been speculated that a unusual long and narrow tank piece, which rolled out of Starfactory in late 2024 may be the header tank of a Block 2 Super Heavy booster, and a significantly redesigned booster aft section has been spotted in the Starfactory in addition, which may be the aft section of a Block 2 booster, although this is not confirmed.[1] This suggests that the Block 2 Super Heavy booster may use larger header tank, which may be used for the boostback burn in addition to the landing burn, which should mitigate fuel sloshing problems observed during early flight tests.
Label on a ring stand in Starfactory. c Starship Gazer
On 24 February 2024, a label was spotted inside Starfactory on a ring stand for a "18.1 FWD Ring Flange". The Booster 18.1 (B18.1) test tank will likely be the first test article for Block 2 boosters indicating that development for the new version has started. This also indicates, that B18 could be the first Block 2 booster.[2]
Super Heavy Booster Block 3 (Version 3)[]
The block 3 will be very similar to the block 2, with the only differences being that it will be a lot taller, and it might feature a different raptor model, and maybe more engines.
Technical Specs[]
According to SpaceX, the V1 Super Heavy Booster has a gross liftoff mass of over 3000 tons.[3] It uses liquid methane and oxygen as its propellant. While Booster 1 had its LOX tank on top of the CH4 tank, subsequent prototypes adapted to the layout of the Ship (upper stage), with the LOX tank at the bottom. Specs as of March 2024:[4]
| HEIGHT | 71 m / 232 ft |
| DIAMETER | 9 m / 29.5 ft |
| PROPELLANT CAPACITY | 3,400 t / 7.5 Mlb |
| THRUST | 7,590 tf / 16.7 Mlbf |
A rendering of a booster with landing legs.
The booster was designed to have landing legs, as the entire rocket is to be reusable. However, Elon Musk later announced that the booster will be "caught" by the launch tower's chopsticks, using the grid fins to take the load. However, it is now confirmed that the chopsticks "grab" the booster by dedicated load-bearing points. Testing for this procedures was started in June 2024 on OLIT-1 with Booster 14.1 (B14.1), and there have already been two successful booster catches in IFT5 and IFT7.
Elon Musk shared an animation of this process:[5]
Animation by SpaceX (27 June 2024)[6]
Old specs[]
| Height | 69 m | 230 ft |
| Diameter | 9 m | 30 ft |
| Propellant Capacity | 3400 t | 6.8 Mlb |
| Thrust | 7590 tf | 17 Mlbf |
Prototypes[]
| Vehicle | Stacking Commenced | Stacking Completed | First Cryo Proof | Flights | Remarks |
|---|---|---|---|---|---|
| Booster 7 (B7) | December 21, 2021 | March 10, 2022 | April 4, 2022 | April 20, 2023 (FLT-1) | Booster flight terminated by FTS prior to stage seperation |
| Booster 8 (B8) | March 12, 2022 | July 8, 2022 | None | None | Scrapped |
| Booster 9 (B9) | December 21, 2022 | November 18, 2023 (FLT-2) | Booster RUD due to progressive engine failures during boostback | ||
| Booster 10 (B10) | October 13 202 | March 22, 2023 | July 18, 2023 | March 14, 2024 (FLT-3) | Booster telemetry lost during landing attempt |
| Booster 11 (B11) | March 19, 2023 | June 3, 2023 | October 13, 2023 | June 6, 2024 (FLT-4) | Booster softly splashed down on target - some parts recovered |
| Booster 12 (B12) | June 3, 2023 | August 28, 2023 | January 10, 2024 | October 13, 2024 (FLT-5) | Booster caught, currently in the Rocket Garden |
| Booster 13 (B13) | September 5, 2023 | February 3, 2024 | April 26, 2024 | November 19, 2024 (FLT-6) | Booster catch aborted, controlled splash down near Starbase |
| Booster 14 (B14) | February 15, 2024 | April 26, 2024 | October 4, 2024 | January 16, 2025 (FLT-7) | Booster caught |
| Booster 15 (B15) | June 4, 2024 | September 22, 2024 | December 17, 2024 | March 6, 2025 (FLT-8) | Booster caught |
| Booster 16 (B16) | October 16, 2024 | December 26, 2024 | February 28, 2025 | ||
| Booster 17 (B17) | January 4, 2025 | March 4/5, 2025 |
Additionally list of Booster Prototypes:
- BN1
- BN2
- BN2.1 (test tank)
- BN3
- Booster 4 (B4)
- Booster 5 (B5)
- Booster 6 (B6)
- B7
- B7.1 (test tank)
Engines[]
The Booster's engine layout has had several changes. While B4 had a 29 engine layout with version 1 Raptors, Booster 7 was the first booster to be equipped with 33 engines, all of which are Raptor 2 engines. Booster 9's engines were upgraded, the first ones using electric TVC (thrust vector control) instead of hydraulics.
Video of a gimballing test on B4:[7]
References[]
- ↑ https://www.youtube.com/watch?v=HiVa2-MCYWA
- ↑ https://x.com/StarshipGazer/status/1894241866259771570
- ↑ https://www.spacex.com/vehicles/starship/
- ↑ https://www.spacex.com/vehicles/starship/
- ↑ https://twitter.com/elonmusk/status/1484012192915677184
- ↑ https://twitter.com/SpaceX/status/1806444825979543725
- ↑ https://twitter.com/elonmusk/status/1472052839316963329