SpaceX rolled out the next generation of Starship to Masseys for testing, but during a routine ambient-pressure test, the Liquid Oxygen Tank ruptured. This leaves SpaceX with no Block 3 Boosters to test with after just finishing stacking Booster 18, 16 days ago.
Booster 18 suffered an anomaly during gas system pressure testing that we were conducting in advance of structural proof testing. No propellant was on the vehicle, and engines were not yet installed. The teams need time to investigate before we are confident of the cause. No one…
— SpaceX (@SpaceX) November 21, 2025
Booster 18
Booster 18 rolled out to Masseys on Nov 20, 2025, and was set to complete its cryogenic proof test campaign ahead of Flight 12. However, during an ambient-pressure test in the early morning hours of Nov 21, the Liquid Oxygen (LOX) tank on Booster 18 ruptured, leaving a massive hole.
During this test, only nitrogen and oxygen gas are used to pressureize the tanks and COPVs (Composite Overwrapped Pressure Vessels).
Based on photos of the damage, it appears that a COPV at the bottom of one of the larger chines might have exploded during the pressure test.
This appears to have triggered a chain reaction that spread up the chine, ultimately blowing up the rest of the COPVs in that chine. This led to a significant rupture in the LOX tank, and remarkably, Booster 18 did not tip over immediately.
Booster 18 with a hole in its LOX tank after an anomaly during a pressure test (Credit: Ceaser G for NSF)
Currently, the Booster is being held up by the new, larger Liquid Methane (LCH4) transfer tube, and it is unknown how SpaceX will safe this vehicle so that crews can return to Masseys. SpaceX either needs to find a way to collapse the booster safely and then clean up the scraps, or use the LR11000 crane at Masseys to stabilize it and scrap it.
If this were a COPV, it would not be the first time SpaceX has lost a vehicle to one. Just five months ago, SpaceX lost Ship 36 to a COPV explosion during a six-engine static fire attempt on June 18, 2025. That is the reason why Masseys is still being rebuilt today. This could also have been a weld failure in the tank wall, but until we hear more directly from SpaceX, it is only speculation at this point what caused the rupture.
Booster 18 at Masseys Before the Anomaly (Credit: Ceaser G for NSF)
Impact and Ship 39
As for what this means for the program, SpaceX currently has zero completed flight boosters and will have to switch gears to Booster 19. Currently, Booster 19 hasn’t even started its stacking process in Mega Bay 1, and even if it were to start today, barring any investigation and modification time, the booster wouldn’t be ready for cryogenic proof testing until at least the end of January.
This is certainly not the start to the Block 3 era that SpaceX would’ve wanted, but it’s a good thing this happened during proof testing at Masseys and not during a 33-engine static fire attempt on Pad 2. As for what was to be its other half, Ship 39 is now stacked in Mega Bay 2 and will be outfitted after finishing stacking on Nov 15, 2025. It will be a bit before this vehicle can head out to Masseys for testing, as the Ship Cryo Thrust Stand is currently in use by S39.1.
S39.1 in the Starfactory before rolling to Mega Bay 2 (Credit: Gage (Rough Riders Show for NSF)
S39.1 is the Block 3 ship aft test article that will be used to verify the changes to the ship aft section. But Ship 39 won’t be needed for a while as Booster 19 hasn’t even started stacking yet. This test tank will join B18.1 and B18.3 booster test tanks already at Masseys. These two test tanks have already completed 17 combined cryogenic proof tests.
Another consequence of this failure is that SpaceX no longer has a booster to commission Pad 2. This is a big deal, as all the tank farm equipment must be tested during vehicle loading to verify that it works correctly. SpaceX could try to modify B18.1 to fit inside the launch mount for testing, or teams could try to salvage the aft section of Booster 18 and stick some small tanks on it.
If crews don’t figure out a way to test the new pad in the interim, SpaceX will have to wait until Booster 19 is ready to be placed on the launch mount, which could be a couple of months down the road.
This anomaly comes on the heels of a pair of successful flight tests after four straight failures with Block 2 of Starship. Of course, this will push Flight 12 out indefinitely until SpaceX finds and solves the problem and builds another booster to replace Booster 18.
Featured Image: Booster 18 with a rupture in its LOX tank after an anomaly during proof testing (Credit Ceaser for NSF)
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