United Launch Alliance's Vulcan Centaur rocket suffered a nozzle burn-through on one of its four solid rocket boosters during the February 12 USSF-87 national security launch, the second time in just four flights that the vehicle has experienced the same category of anomaly. The problem, visible in launch footage as an anomalous plume less than 30 seconds after liftoff, is raising hard questions about the reliability of America's newest heavy-lift rocket. Vulcan's role goes well beyond Starlink and national security satellites. It is slated to carry lunar cargo, deep-space infrastructure, and classified Space Force payloads critical to any sustained cislunar presence. A booster with a burn-through pattern in half its flights cannot be that rocket without a credible fix. AI-generated image ULA's Vulcan Centaur is designed to fly 16-18 missions per year, including national security and cislunar missions. Credit: AI-generated May 20 Update The Fix Is Moving Through Ground Test, Not Flight Clearance ULA now has one concrete recovery milestone after Vulcan's February USSF-87 booster anomaly. Northrop Grumman completed a static fire of a GEM 63XL solid rocket booster on April 15, and ULA told Spaceflight Now the test demonstrated nozzle design enhancements that were already in work, plus advanced propellant technology for future motors. The company said data from the test, combined with the flight investigation, will be used to validate analytical models and support Vulcan's return to flight. That does not mean Vulcan is cleared. ULA says the integrated government and contractor team is still reviewing technical data, imagery, and debris evidence from USSF-87. The February mission reached its planned geosynchronous orbit, but one booster produced asymmetric thrust before separation, forcing the BE-4 engines and avionics to compensate. The key question is no longer whether Vulcan can survive a booster nozzle problem. USSF-87 showed that it can. The harder question is whether ULA and Northrop can prove the same failure mode will not repeat on a national security or lunar payload. Apr. 15 GEM 63XL static fire completed 4 SRBs on the USSF-87 Vulcan configuration 38 Vulcan launches Amazon Leo has purchased Amazon May Be the Return to Flight Customer ULA's near-term Vulcan path is also shifting from government missions toward commercial cadence work. On May 14, ULA placed the first Vulcan booster into its new Vertical Integration Facility for Amazon missions at Cape Canaveral. The new lane lets ULA process Vulcan for Amazon Leo while the original integration facility continues supporting government and Atlas work. ULA said the hardware stack will support procedure, interface, and ground-system validation ahead of a wet dress rehearsal. Gary Wentz, ULA's vice president of government and commercial programs, told Spaceflight Now that the return-to-flight customer is more likely to be Amazon. That matters for cislunar planning because it separates technical recovery from mission assurance acceptance. A commercial Amazon flight could rebuild operational confidence, but Space Force payloads still need flightworthiness approval before Vulcan resumes its national security role. Lunar cargo customers will watch both tracks. A rocket can be available on paper and still be schedule-risky if the government customer base has not fully accepted the corrective action. Why This Changes the Cislunar Read The April test gives Vulcan a recovery path, but it also confirms that the SRB issue is now a program-level bottleneck. ULA is not just fixing a single flight. It is trying to prove a booster family used across Vulcan configurations can support high-cadence Amazon launches, national security missions, and future lunar delivery opportunities. The cislunar takeaway is simple: Vulcan remains one of the few U.S. heavy-lift alternatives to Falcon Heavy and Starship, but every month of SRB uncertainty makes the lunar logistics stack more dependent on SpaceX. The next useful signal will be the wet dress rehearsal for the Amazon Leo Vulcan stack, followed by any Space Force statement on flightworthiness. Until both happen, the successful static fire is progress, not closure. What Happened on USSF-87 At 4:22 a.m. EST on February 12, Vulcan lifted off from Launch Complex 41 at Cape Canaveral Space Force Station carrying the USSF-87 mission, a national security payload believed to include at least one Geosynchronous Space Situational Awareness Program (GSSAP) satellite for the U.S. Space Force. Within 30 seconds of liftoff, observers on the ground and cameras tracking the vehicle spotted an anomalous plume from one of the four Northrop Grumman-built GEM 63XL solid rocket boosters strapped to the rocket's first stage. The plume pattern was consistent with a nozzle burn-through, where hot combustion gases erode through the nozzle throat or exit cone of the solid motor. As the vehicle completed its pitch-over maneuver into the ascent trajectory, the rocket began rolling more noticeably than usual, a probable consequence of the asymmetric thrust produced by the damaged booster. Vulcan's flight computer compensated, the four SRBs jettisoned on schedule at T+1 minute 37 seconds, and the mission continued on a nominal trajectory. ULA Statement — February 12, 2026 "We had an observation early during flight on one of the four solid rocket motors, the team is currently reviewing the data. The booster, upper stage, and spacecraft continued to perform on a nominal trajectory." — United Launch Alliance ULA has not yet disclosed whether the payload was successfully delivered. GSSAP satellites operate in geosynchronous orbit and play a key role in tracking other satellites in that crowded belt. The mission was considered successful based on trajectory data, but the anomaly itself demands explanation regardless of outcome. The GEM 63XL nozzle throat is the critical failure point. A burn-through occurs when hot gases erode the nozzle material faster than predicted. Credit: AI-generated A Pattern, Not a Fluke What makes February 12 alarming is not the anomaly in isolation. It is the pattern. A near-identical nozzle burn-through was observed during Vulcan's second certification flight on October 4, 2024. That event prompted ULA and Northrop Grumman to conduct a thorough review, including a hot-fire ground test of the GEM 63XL motor in Utah. The U.S. Space Force reviewed the analysis and certified Vulcan for national security missions. ULA's third Vulcan flight in August 2025 went without incident, which ULA leadership cited publicly as validation that the issue was resolved. It was not resolved. USSF-87 on February 12 was Vulcan's fourth flight. The same failure mode reappeared in exactly the same phase of flight. Flight Date Mission SRB Anomaly Outcome VC1 (Cert 1) Jan 8, 2024 Peregrine lunar lander None detected Nominal ascent VC2 (Cert 2) Oct 4, 2024 Amazon Kuiper satellites Nozzle burn-through Nominal trajectory, payload delivered USSF-106 Aug 12, 2025 Space Force payload None detected Nominal ascent USSF-87 Feb 12, 2026 GSSAP satellites Nozzle burn-through Nominal trajectory, payload believed delivered Two burn-throughs in four flights is a 50 percent recurrence rate. For a vehicle that ULA intends to fly 16 to 18 times per year, that is an untenable number. The fact that both anomalies ended with nominal payload deliveries is fortunate, but it obscures the structural problem: a burn-through that goes further than observed in these two cases could compromise vehicle control and result in mission loss. What is a GEM 63XL Nozzle Burn-Through? • GEM 63XL: Graphite Epoxy Motor, 63-inch diameter, extra-long variant. Built by Northrop Grumman, also used on ULA's Atlas V rocket. • Burn-through mechanism: Hot combustion gases (around 3,300°C) gradually erode the carbon-phenolic or graphite nozzle material during the roughly 90-second burn. If erosion exceeds design margins, gases escape through the nozzle wa