As usual, the SpaceX South Texas Launch Facility near the village of Boca Chica is the focus of attention. Almost two months ago, the facility’s crews began work on the first true Super Heavy prototype, the launch phase of SpaceX’s Starship. After six weeks of assembly, SpaceX rolled the Super Heavy Booster 3 (B3) out of the “High Bay” (where it was assembled) and installed it on the launch pad.
The assembly process began on May 15th, supported by the new bridge crane (which was added to the High Bay back in March) and was completed on Thursday July 1st. The B3 was then pulled out and loaded onto the company’s Self-Propelled Modular Transporter (SPMT) and transported via Highway 4 to the launch facility, where it was reloaded onto test ramp A by another crane.
Once ready to run commercial missions, Starship and Super Heavy will be the world’s first fully reusable launch system. As the booster element (also known as the first stage) of the system, the Super Heavy is approximately 65 meters (215 ft) high and is equipped with 32 Raptor engines. That record number of engines (more than any rocket in history) will enable the Super Heavy to produce 72 meganewtons (MN) or 16 million pounds / thrust (lbf).
This is more than double the thrust generated by the first stage of the Saturn V booster that NASA used to send the Apollo astronauts to the moon – 35.1 MN, or 7.89 million lbf. In combination with the Starship – the orbital vehicle element that relies on 6 Raptors engines – the launch system can send 100 tons (110 US tons) into Low Earth Orbit (LEO).
According to a statement by Musk via Twitter, the B3 prototype will be used for soil tests, similar to the soil tests carried out with the Starship (SN) prototypes. This sets it apart from Booster 1 (BN1), the first Super Heavy prototype to complete stacking in the High Bay, which Musk said was and will be a “manufacturing pathfinder” designed to validate the process by which they were built therefore scrapped afterwards.
B3 is the next step in this process and is intended to validate the structural design of the booster through soil tests. Musk indicated that SpaceX will conduct the first flight test with Booster 4 and expect “a particularly rapid development in” [the] first ~ 10 boosters and ~ 30 ships. ”This suggests SpaceX will maintain its rapid prototyping approach, which incorporates design changes between iterations.
The first one to fly is Booster 4. Booster 3 is used for ground tests. We’re changing a lot of the design from 3 to 4. Booster 3 was very difficult to build. Expect particularly rapid development in the first ~ 10 boosters and the first ~ 30 ships.
– Elon Musk (@elonmusk) June 30, 2021
In the same message, Musk tweeted that the B3 was “very difficult to build”. All in all, the assembly process consisted of stacking and welding 36 steel rings with three tank domes and dozens of other key components. Fortunately, the ground crews have developed considerable expertise as the booster element is made up of many of the same parts as the Starship and the assembly process relies heavily on the same production equipment.
The booster element is also simpler than the Starship prototypes in many ways in that it does not require a heat shield, has simpler electronics and piping, simpler fins (not included with the B3), and two main tanks to keep the liquid supply going Absorb methane (CH4) and liquid oxygen (LOX) fuel. The Starship, on the other hand, needs two additional collection tanks in addition to its main tanks and has to switch to the collection tanks when landing.
During flight tests, the booster prototypes only have to start and then sink where they are from the. According to Musk, these prototypes (B4 and later) will be equipped with grid fins to control their descent, and the booster will reignite some of its engines to make a soft landing. To date, all high-altitude flight tests with the Starship prototypes have included the “belly-flop” maneuver, starting with the lateral rotation of the prototype after reaching the apogee.
It would then use its aerodynamic flaps to slow its descent and reignite a Raptor engine or two to realign itself before landing. This complicated maneuver caused the first four prototypes (SN8, SN9, SN10 and SN11) to explode before, during or shortly after landing. The most recent test with the SN15 prototype was a complete success, validating the critical systems and maneuvers it performed.
Image Credit: SpaceX
In any case, since the B3 is now on the test platform, the tests can begin (possibly this week). Similar to the Starship development process, this will likely begin with cryogenic pressure testing, which involves filling the fuel tanks with nitrogen to ensure they can withstand being filled with cryogenic methane and oxygen. This can be followed by engine integration and static fire tests.
These tests will pave the way for B4, which is currently under assembly and will be integrated into the SN20 Starship prototype and prepared for orbital testing. These will then be relocated to the OLS, which was also built in the Boca Chica launch facility in recent weeks. From here, the full-stack Starship and Super Heavy take off on their first orbital test flight – which could take place this year.
In the meantime, be sure to check out the rollout of B3 on the test pad courtesy of NASA Spaceflight:
Further reading: Teslarati, NASA Spaceflight
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