Starship Flight 2: One year later
Today it’s November 18th, 2024, and we’re hopefully just a day and a half away from seeing Starship Flight 6. But today is also a special anniversary because it marks exactly 1 year since Starship Flight 2. The Starship program has come a long way, so let’s go back in time to explore in detail Starship Flight 2 and what’s come from it.
Vehicles
Booster 9
History and testing
October 24th, 2021: the first part of Booster 9, a thrust puck for 13 engines, is delivered.
July 16th, 2022: stacking began, starting with the Booster’s CH4 section.
September 28th, 2022: with the stacking of the last LOX section, stacking of Booster 9 was completed.
December 15th, 2022: Booster 9 rolls out to the Orbital Launch Site cryo station.
December 21st, 2022: Cryo test 1 of both tanks to verify their structural integrity.
December 29th, 2022: Cryo test 2 of both tanks to verify their structural integrity. Both of these cryo tests occurred at the Launch Site since the Massey’s outpost wasn’t ready yet for cryo tests. Also, both tanks were partially filled in both tests.
January 10th, 2023: Booster 9 is rolled back to the Production Site for engine installation.
July 20th, 2023: Booster 9 is moved to the Launch Site after sitting in the Rocket Garden for 2 days.
July 23rd, 2023: Cryo test 3: this test was also conducted on the OLM, and it was a full cryo test. Both tanks were completely filled.
August 4th, 2023: Spin Prime 1 of Booster 9’s Raptor engines. The number of Raptors tested is unknown; however, SpaceX declared the test a success.
August 6th, 2023: Static Fire 1: this was the first static fire using the Water Deluge System. It lasted just 2.74 seconds instead of the planned 5, and 4 engines shut down prematurely.
August 8th, 2023: Booster 9 was rolled back to the Production Site, and 8 days later, on August 16th, the Hot Staging Ring was installed for the first time on a Booster.
August 22nd, 2023: following the HSR’s installation, Booster 9 rolls to the Launch Site for its last time.
August 23rd, 2023: Spin Prime 2
August 25th, 2025: Static fire 2: this static fire successfully lasted full duration, but 2 engines shut down prematurely and did not run full duration.
September 5th, 2023: Ship 25 is stacked atop Booster 9; this will start more than 2 months of inspections and integration tests where the HSR will be continuously removed and installed again.
October 24th, 2023: Wet Dress Rehearsal: both stacked vehicles for Flight 2 undergo a successful WDR.
Upgrades
Booster 9 featured several important upgrades relative to Boosters 7 and 8; the biggest visible change of all was, of course, the new Hot Staging Ring: this piece of hardware is a ring 9-m wide, 1.8-m high, and weighs 9 tons. The HSR was first integrated on Booster 9 after SpaceX decided to implement the technique of hot staging, which requires igniting the Ship’s engines while it’s still attached to the Booster. In order to do this, the Booster needs to have something to allow the hot exhaust gases to protect the forward dome of the Booster, and this is the purpose of the Hot Staging Ring, which is a vented removable interstage. A steel blast surface was also built and installed inside the HSR to protect the forward dome during hot staging. Another major change is the switch from hydraulic to electric TVC (Thrust Vector Control, which allows the 13 central engines to steer the Booster in different directions) by removing the hydraulic units and installing a black box per gimbaling engine on the thrust dome. Another upgrade to the thrust dome is the installation of the large methane pipe for the gimbaling engines. Also, many reinforcements were added to the engines and engine bay to prevent catastrophic failure. The chines have also seen hardware added under them and Starlink dishes on their top, and due to the addition of hardware inside (such as batteries), they’re not anymore the same lengths, but it varies; Booster 9 is also the first to receive the revised version of the thrust puck, which reduces weight by implementing better steel milling techniques. Many vents were changed or added, such as: 4 new vents for the CH4 tank, while the rest were revised, larger cowbell vents for the LOX tank, and 18 new pressure vents at the base of the Booster to allow exit of hazardous gases from the engine bay. More changes were made regarding the autogenous pressurization system, CH4 tank access hatch, and BQD. The last major change are additional plates on the Booster’s grid fins to provide better structural strength and robustness, possibly in view of the new hot staging maneuver.
Booster 9 with its Hot Staging Ring integrated on top. Credit: SpaceX
Ship 25
History and testing
February 14th, 2022: first parts spotted.
April 2022: stacking begins.
October 2022: stacking complete.
October 28th, 2022: Ship 25 conducts an ambient pressure test.
November 1st, 2022: Cryo test 1 of both tanks.
November 2nd, 2022: Cryo test 2 of both tanks.
November 7th, 2022: Cryo test 3 of the LOX tank.
May 5th, 2023: Cryo test 4 of both tanks, its first cryo at Massey’s.
June 21st, 2023: Spin Prime 1
June 26th, 2023: Static fire 1 of all 6 engines, lasting about 4.5 seconds.
September 5th, 2023: Ship 25 is stacked atop Booster 9; this will start more than 2 months of inspections and integration tests where the HSR will be continuously removed and installed again.
October 24th, 2023: Wet Dress Rehearsal: both stacked vehicles for Flight 2 undergo a successful WDR.
Upgrades
While the Ship received fewer upgrades than the Booster, there were some changes nonetheless. 2 methane tank vents were repositioned, and additional pressure control hardware was either repositioned or deleted (such as 1 baffle slot on the methane tank). There were some minor changes on the Thermal Protection System, especially around the hinges of the flaps and on the flaps themselves. The structure of Ship 25 received some changes regarding the payload bay door, stiffeners, stringers, and access hatch. Given the new Hot Staging maneuver, the Ship’s engines received additional protection and shielding. The last major change was done to the Flight Termination System, since an additional box of explosives was added, some were replaced, and bigger explosives were added. All these changes may just be a part of the many changes done to the Ship (like the Booster), but they provide an overall idea of what areas SpaceX focused on these vehicles.
Additional ground updates
The vehicles are not the only ones that received upgrades for Flight 2, but even the launch site received many upgrades. After Flight 1 created a crater and incredible damage to the launch site, many ground infrastructure, such as plumbing, vertical and horizontal tanks, tower, and OLM, received additional reinforcements. The biggest change to prevent all this, at least in part, was the Water Deluge System (WDS), which spewed out about 500.000 liters of water starting 10 seconds before launch to prevent damages and suppress the sound. It turned out to be very successful, and Flight 2 was the first launch in which it was used.
Booster 9 and Ship 25 stacked together 2 months before launch. Credit: Jack Beyer
Launch and outcome
Starship during ascent, with all 33 Raptor engines lit. Credit: John Kraus
Starship during hot staging. Credit: SpaceX
The launch license was received on November 15th, and SpaceX targeted their first launch attempt for November 17th; however, a problem with the grid fins actuator system was discovered the day prior to launch, and so it was postponed 24 hours later, with a 20-minute window opening at 07:00 am CDT. Overnight, Ship 25 was destacked as well as the HSR, and workers changed 3 out of the 4 motors of the grid fins. When the work was completed, the HSR and Ship 25 were stacked, and preparations for the launch were underway. On launch day, fueling started at T-1h37m for Booster and T-1h17m for Ship. The countdown went pretty smoothly, and launch was delayed by just 2 minutes by the T-40s hold. But when it started ticking again, it did not stop. At T-10s, the WDS started spewing out water, and then, surprisingly to many, all 33 Raptor engines ignited at launch! This was the first time, including static fires, that all 33 Raptor engines were ignited for more than a few seconds. In fact, all of them worked seemingly flawlessly until it was time for stage separation: during ascent, the Ship was visibly losing many tiles from its heatshield, but everything else seemed to work. The full stack didn’t lose control during ascent like in Flight 1 and went always higher. Then, the Hot Staging maneuver took place: first, at T+02:44, all but the 3 central Raptor engines were shut down; at T+02:48, the Ship ignited all its Raptor engines for the first time and separated 2 seconds later from the Booster, completing the first-ever hot staging maneuver for this rocket! After stage separation, the Ship continued to go on while the Booster flipped back to initiate the 13-engine boostback burn. However, initially, just 12 engines ignited and many were lost over the next few seconds; the Booster had only 6 working Raptor engines when they were shut down at T+03:19 ahead of FTS destruction 2 seconds later, at 90 km and 3818 km/h. The Ship, however, went on to its trajectory perfectly and became the first Starship to reach space! However, at T+08:03 the engines were shut down by the onboard flight computers, and the Ship was destroyed by FTS a few seconds later, at 149 km and 24.124 km/h. A few months later, SpaceX confirmed the most likely cause for the Booster RUD (Rapid Unscheduled Disassembly) was “filter blockage where liquid oxygen is supplied to the engines, leading to a loss of inlet pressure in engine oxidizer turbopumps that eventually resulted in one engine failing in a way that resulted in loss of the vehicle.” As for the Ship, SpaceX declared more liquid oxygen was loaded onto the Ship to simulate a payload, and that had to be vented prior to reentry. During this planned liquid oxygen venting, a leak in the aft section of the Ship caused a fire that led to the loss of communications between the vehicle’s flight computer, so the engines were shut down and the FTS activated, detecting a mission rule violation. So even if this flight lasted just a few minutes, it was a test, and it ended up validating the WDS and pad upgrades and providing SpaceX with invaluable data on Starship. Many milestones were reached: the first-ever full ascent burn for all of the Booster’s engines, the first hot-staging separation of Starship, and the first Starship to reach space. Corrective actions were taken ahead of Starship Flight 3, which happened on March 14th, 2024, reaching a lot of new milestones thanks to the data gathered during this. The second flight test of Starship was an incredible test that pushed Starship to its limits, allowing SpaceX to continue to rapidly develop it.
References
A Major Improvement: What Changed on Starship 25 & Booster 9?
Starship flight test 2 - Wikipedia
