After completing 11 flights and numerous tests, the booster test stand that was converted into a launch mount has reached the end of its operational life. Pad 1 played a crucial role in advancing the Starship program during its early years and is now transitioning into preparations for the next phase of operations.
Construction of Pad 1 began around July 2020, starting with the foundation work for the six legs of the launch mount. These legs were installed and poured, and the structure remained in place for several months. By January 2021, crews started building the fluids bunker and the concrete pad designed for the original vertical tanks.
Just before the completion of the suborbital hops with SN15, SpaceX began constructing the launch tower. After the hops were finished, the landing pad was converted into a construction zone where the chopsticks and the ship’s quick disconnect arm (SQD) were built.
Initially, SpaceX planned to have two vertical Liquid Nitrogen (LN2) tanks, three vertical Liquid Oxygen (LOX) tanks, and two vertical Liquid Methane (LCH4) tanks. However, during certification, the LCH4 tanks failed to meet Texas state fire code requirements. As a result, SpaceX switched to horizontal tanks instead. The final setup for early testing and flights included seven horizontal methane tanks, two medium tanks, and five small tanks. A sixth small tank was placed in the tank farm but was never connected.
The launch mount itself was constructed at the production site, then transported to the launch site and installed on the legs on July 31, 2021. Just six days later, SpaceX quickly moved Booster 4 and Ship 20 to the pad shortly after their construction was completed. On August 6, 2021, the first-ever Starship stack was visible next to a tower that lacked chopsticks, the SQD arm, and had an incomplete tank farm.
This initial stack was achieved using the Liebherr LR 11350 crane, which was also used to assemble the launch tower. However, this first stack was primarily a photo opportunity. The next stack did not occur until February 10, 2022, when the chopsticks were used. This stack served as a test for the chopsticks and was the backdrop for SpaceX CEO Elon Musk’s Starship Update in February 2022. The first full-stack testing happened during the third and final stack of Booster 4 and Ship 20, which included two cryogenic proof tests on March 16 and 18, 2022.
Regarding pumps and subcoolers, early testing and launches used three LOX pumps and four subcoolers, while the methane side had three pumps and two subcoolers. The first cryogenic test on Pad 1(A) took place on December 17, 2021, with Booster 4, followed by two more tests in the following days. Unfortunately, these tests damaged Booster 4’s internal plumbing and Raptor engines due to foreign object debris entering the booster’s tanks, eliminating any chance of engine testing on Booster 4.
The first engine testing on Pad 1 did not occur until July 11, 2022, with Booster 7. This test became known as the “spin boom” after SpaceX attempted a spin prime with all 33 engines. The ignition of oxygen and methane gas beneath the mount caused a detonation, but fortunately, it did not result in the booster exploding.
Following this incident, SpaceX installed breakaway hoses from the engines to a manifold to divert LOX engine chill away from the launch mount. These hoses remained in use throughout the pad’s operational life.
The first static fire on Pad 1 happened on August 9, 2022, with a single-engine test from Booster 7. This led up to a 31-engine static fire on February 9, 2023, after two engines failed to ignite during a 33-engine attempt. A full-duration 10-second static fire with all 33 engines was not achieved until August 25, 2023, with Booster 9.
The first stack of actual flight vehicles occurred on October 11, 2022, with Booster 7 and Ship 24. After several more stacks and tests, a Wet Dress Rehearsal was completed on January 23, 2023. The stack then launched on April 20, 2023. Initially, engineers hoped the concrete-only foundation would suffice for a single launch. However, the Raptor engines on Booster 7 destroyed the concrete foundation and superheated the groundwater beneath, causing a volcanic-like eruption at the base of Pad 1.
During static fire testing, SpaceX realized that the concrete foundation alone was insufficient to protect the launch pad. Therefore, before Flight 1, crews began installing a steel water plate, which has been used on every flight and static fire since then.
This steel plate is water-cooled and sprays high-pressure water to counteract the intense heat and force of the Raptor engines’ exhaust. This system reduces sound and dust while protecting the launch pad.
Before Flight 2, SpaceX modified the SQD arm to accommodate the increased height caused by the hotstage ring. The arm was moved up by 1.82 meters. This was the second time the SQD arm was adjusted, the first being when the SQD plate on the ship was moved up between Ship 20 and Ship 24.
After the successful Flight 2, SpaceX added nine horizontal LN2 and LOX tanks and expanded the number of pumps and subcoolers at the launch pad. Two additional LOX pumps and four more subcoolers were added, along with one more methane pump and two more subcoolers. These upgrades reduced the propellant loading time from 1 hour and 30 minutes to 50 minutes.
Following Flight 3 and before Flight 4, the new horizontal LOX and LN2 tanks were fully integrated into the tank farm, and the vertical tanks began to be dismantled.
After Flight 4, crews started modifying the tower and chopsticks to prepare for booster catch operations. This involved reinforcing the arms and adding larger gusset plates to the top of the tower to increase its strength. The vertical tanks were completely removed as they were no longer needed.
Flight 5 marked a significant milestone for the Starship program. SpaceX successfully recovered a Super Heavy Booster, and the launch pad infrastructure functioned perfectly, allowing the team to catch Booster 12. The catch arms later caught Boosters 14 and 15, and the launch pad supported the reflights of both boosters on subsequent missions.
The configuration of Pad 1 remained largely unchanged from Flight 5 through Flight 11. There were two occasions when SpaceX placed a ship on the pad for static fire tests because Ship 36 had caused damage to the launch mount. The two ships used for these tests were Ship 37 and Ship 38. SpaceX made modifications to the pad to minimize disruptions to flight operations.
The fastest turnaround time for Pad 1 was 37 days between Flight 5 and Flight 6. Over its lifetime, Pad 1 conducted 28 cryogenic proof and tanking tests, 15 spin primes, 34 static fires, six wet dress rehearsals, four aborted launch attempts, and 11 full-stack flight tests.
Throughout its operation, the chopsticks performed over 100 lifts. These lifts included mounting and demounting boosters from the pad, as well as stacking and destacking ships.
The quickest stack in Pad 1’s history was the second-to-last stack of Flight 2 with Ship 25. From leaving the transport stand to being placed on Booster 9, the process took just 33 minutes.
After all the testing and challenges, SpaceX will retire this pad and begin converting it to the new design. The lessons learned from Pad 1 have been invaluable and made this transition possible. Pad 1’s service and contributions to the Starship program are deeply appreciated.