With the Federal Aviation Administration and US Fish and Wildlife Service approving the final signoff and license and SpaceX saying the rocket is ready, Starship set sail from Starbase on its second test flight Saturday. Liftoff at the first attempt followed only a one day slip to fix an issue with Booster 9’s grid fin actuators.
During Starship’s first test flight, which took place on April 20, 2023, SpaceX experienced several issues that led to the loss of control and, ultimately, the loss of Booster 7 and Ship 24. For this second flight, SpaceX made several changes to the booster, ship, and the launch pad – resulting in numerous successful milestones.
Starship Flight Test One:
During the first flight, Booster 7 experienced fires in its engine compartment due to a build-up of methane, which was a result of propellant leaks in the aft section of the vehicle. These fires led to wire bundles melting and burning, leading to loss of control of most of the booster’s engines from the flight computer.
To mitigate the engine fires and loss of control of each vehicle, SpaceX upgraded the engine section purge system with larger supply tanks and more vents to allow the gasses to be vented out and away from the vehicle.
The second biggest upgraded system is the flight termination system on both vehicles, as SpaceX added larger explosive charges and relocated them to a more effective location for the termination of the flight.
An exciting change for this flight will be the introduction of hot staging. This is where the ship will ignite its engines and separate from the booster while some of its engines are still running. This will add some more payload capacity to the ship, and keep the separation system simpler.
Orbital Pad Changes
After the first flight test, the Orbital Launch Pad (OLP) had a massive crater dug into it while the engines ramped up to full power. Then, even more damage was done because at liftoff Booster 7 was only running with 30 engines at 90% throttle, which put its Thrust-to-weight ratio (TWR) at just above one. This resulted in a slower initial ascent and the stack taking longer to clear the pad than SpaceX predicted.
To prevent something like this from occurring again, SpaceX had been working on a water deluge system before the first flight. However, Elon indicated shortly after the first flight that this system wouldn’t have been ready in time for that first flight. After the first launch, SpaceX got to work quickly on repairing the damage, along with the preparations for redoing the entire foundation of the launch pad.
These launch pad upgrades started with reinforced concrete pilings in and around the pad. Once these were completed, SpaceX dug a couple of meters into the ground under the Orbital Launch Mount (OLM) and started to lay very large amounts of rebar for what would become the new foundation. After the foundation had been poured, SpaceX laid out the rebar for the pile cap on top and then welded embeds on the top, where the deluge plate would be welded to once installed.
After everything was installed and all the concrete was poured, SpaceX installed the water deluge flame deflector, significantly increasing the robustness of the launch pad.
The water pressure for this system is very high, which is expected to protect the steel plate itself from the Raptors’ exhaust. This will prevent the “rock tornado” that was seen during the last launch.
With these pad upgrades and SpaceX CEO Elon Musk saying that the launch sequence will be modified to reduce the engine ramp-up time from six seconds to three seconds, the pad is expected to survive with significantly less damage than after Starship’s first integrated test flight.
Flight Test Two
Ahead of launch, there has been no indication that SpaceX is changing the countdown other than the engine ramp-up time mentioned earlier. Also, the trajectory of this flight test was set to be the same as what the first test flight was supposed to be.
Unlike the maiden flight, Starship stuck to the plan, with a clean liftoff and all 33 Raptor 2s running without issue as the vehicle flew out of South Texas.
Hotstaging – debuting on this flight – also worked as planned, with Ship 25 firing up its six Raptors and moving away from the booster.
Booster 7, having completed its primary task, then attempted a boostback burn, before letting go during that attempted relight.
Farewell shot of Booster 9, which performed amazingly with all 33 engines smiling all the way up. Went out with a bang.
— Chris Bergin – NSF (@NASASpaceflight) November 18, 2023
Ship 25 got very close to orbital velocity before it too was destroyed by the Flight Termination System (FTS), although both losses of vehicle should not detract from the numerous successes achieved during this second flight.
For this launch, the hope was for the upgrades to Booster 9 to be effective, allowing the stack to reach stage separation without many issues. That was achieved.
The main goal of the first few test flights is to test the booster and work out potential issues with its design. Once this goal is achieved, SpaceX is expected begin testing reentry and booster recovery.
— Jack Beyer (@thejackbeyer) November 18, 2023
The launch pad appears to have survived well during this launch, a testament to the water deluge system and other improvements.
Flight Test Three and Beyond
The vehicles for the third flight are slated to be Ship 28 and Booster 10, both of which have several upgrades already over the current stack. After the third flight, it is expected that SpaceX will follow up with booster/ship pairings in sequential order. For example, Ship 29 would fly with Booster 11, Ship 30 would fly with Booster 12, etc. It is unclear, however, if this sequential order will be kept going forward as SpaceX could be planning for ground test vehicles at a later point.
To get approval for the third flight, SpaceX will still have to get a launch license modification, as Revision 1 of License No. VOL 23-129 for the second flight notes “For the Orbital Flight Test 2 mission only unless this license is modified to remove this term.” Additionally, if there is any sort of anomaly during this second flight, a mishap investigation will be required before another launch.
Ships 28 through 32 have many similarities, although as more upgrades are made to ships, some of the changes are being retrofitted to the older ships. Regarding boosters, Boosters 10 through 13 have decent changes between them as SpaceX continues to upgrade.