The Vulcan rocket leapt off its pad at 4:22 a.m. EST, lighting up the Florida coast before a problem inside one of its strap-on boosters turned a routine climb to orbit into a high-stakes anomaly. United Launch Alliance later described what happened as a “significant performance anomaly” in one of the solid rocket motors, even as the rest of the vehicle pressed ahead. The mission’s primary payload, a Geosynchronous Space Situational Awareness Program spacecraft bound for geosynchronous orbit, carried national security expectations that raised the pressure on Vulcan’s performance and will now shape how its early track record is judged.
Despite the scare, ULA and Space Systems Command say the classified objectives of the USSF-87 flight were met, with the payloads delivered directly to geosynchronous orbit. The failure inside a single booster has instantly become a key test of Vulcan’s perceived reliability, yet the nominal behavior of the booster core and Centaur upper stage suggests the rocket’s core architecture held up under stress rather than collapsing under its first major in-flight problem.
Mission Background and Launch Setup
The USSF-87 mission was framed by Space Systems Command as a national space security launch built around a primary Geosynchronous Space Situational Awareness Program payload headed to geosynchronous orbit. SSC described USSF-87 as a multi-manifest mission, meaning the GSSAP spacecraft shared the Vulcan ride with additional national security payloads that remain classified. The command emphasized that GSSAP’s job in geosynchronous orbit is to provide detailed awareness of objects in that high-altitude belt, a capability the military treats as central to monitoring potential threats and managing congestion around some of its most valuable satellites.
SSC’s official pre-launch statement placed the liftoff at Space Launch Complex 41, identifying SLC-41 at Cape Canaveral Space Force Station as the home for the mission. The Vulcan configuration for USSF-87 was labeled VC4S, pairing a Centaur upper stage with four strap-on solid rocket boosters. SSC highlighted that VC4S was tailored for direct injection to geosynchronous orbit, signaling that the rocket would not rely on long-duration orbit raising by the spacecraft and would instead shoulder the energy cost of the climb all the way to GEO itself.
The Anomaly Unfolds
According to the Primary ULA post-launch statement, Vulcan’s ascent began as planned at 4:22 a.m. EST, with all systems appearing nominal in the opening phase of flight. Soon after liftoff, however, ULA reported that “one of the four solid rocket motors” experienced what the company called a “significant performance anomaly.” The wording signaled that the problem was confined to one of the strap-on boosters rather than the main booster core or upper stage, and that it was serious enough to merit a public acknowledgement even on a classified mission.
ULA stressed in the same statement that the main booster and the Centaur upper stage both performed nominally despite the malfunctioning solid rocket motor. That claim is backed up by the outcome: the company said the rocket still delivered its payloads directly to GEO, which would have required Centaur to execute its planned burns with precision. While ULA has not yet released detailed telemetry plots, the company’s description of the flight profile implies that guidance and propulsion systems were able to compensate for the underperforming booster and keep the mission on its intended trajectory.
Technical Breakdown of the Failure
On the USSF-87 mission page, ULA identifies the strap-on boosters as GEM 63XL solid rocket motors that flank the core stage in the VC4S configuration. These GEM units are designed to provide a substantial share of Vulcan’s total thrust in the opening minutes of flight, effectively helping the rocket muscle off the pad and punch through the thick lower atmosphere. The mission page lists thrust levels for the GEM 63XLs and for the Centaur engines, illustrating how much of Vulcan’s initial acceleration depends on the solids doing their job in sync with the core.
By ULA’s own account, the “significant performance anomaly” affected only one of the four GEM 63XL motors, which means Vulcan suddenly had to climb with asymmetric thrust on one side of the vehicle. In a configuration where four solids are meant to share the load, the loss or degradation of one motor can force the guidance system and core engines to work harder to maintain control and trajectory. The same mission documentation notes that the rocket flew with a large payload fairing sized for national security satellites and that the Centaur V upper stage was responsible for the direct insertion to GEO, both of which became critical factors in salvaging the mission once the booster problem appeared.
Payload Delivery and Mission Outcome
Despite the booster trouble, ULA’s post-flight statement says the Vulcan rocket “successfully” delivered its payloads directly to GEO. That outcome indicates that the Centaur upper stage had sufficient performance margin to compensate for whatever shortfall the misbehaving solid rocket motor created during first-stage ascent. The direct-to-GEO profile is demanding, so arriving on target strongly suggests that the anomaly did not prevent the vehicle from meeting the essential orbital requirements laid out before launch.
SSC’s pre-flight description of USSF-87 as a national space security mission with GSSAP as the primary payload reinforces how sensitive the stakes were for this launch. In its official release, SSC framed GSSAP as part of a broader effort to strengthen space domain awareness in geosynchronous orbit, where many high-value defense and communications satellites operate. The classified nature of the additional payloads means few technical details are available, but both SSC and ULA have treated the mission as a success in terms of getting those assets into their intended orbital neighborhood.
ULA’s Response and Expert Context
In the Primary ULA statement, company vice president Gary Wentz directly acknowledged the problem and said engineers had identified a “significant performance anomaly” in one of the solid rocket motors. Wentz emphasized that the team had isolated the issue to that single motor and that the booster and Centaur systems operated normally throughout the rest of the ascent. His comments signaled that ULA views the anomaly as a hardware or manufacturing issue inside the SRB rather than a systemic flaw in Vulcan’s core design.
From a broader industry perspective, having the first major in-flight problem occur in an auxiliary element such as a strap-on booster is far less damaging to a rocket’s reputation than a failure in the main booster or upper stage. ULA’s mission page portrays Vulcan as the company’s future workhorse for national security launches, with the VC4S configuration and Centaur upper stage tailored for direct geosynchronous insertions for the Space Force. By highlighting that the core systems performed as designed on USSF-87, even under asymmetric thrust, ULA is effectively arguing that Vulcan’s fundamental architecture remains sound.
What It Means for Space Launch Reliability
Because ULA reports that the booster and Centaur behaved nominally, the USSF-87 anomaly may end up being treated as a correctable defect in a single GEM 63XL rather than a black mark on Vulcan’s overall reliability. The company’s own framing in the post-launch release leans heavily on the fact that the payloads reached GEO, which is the ultimate measure most national security customers care about. For the Space Force, a rocket that can absorb a partial failure in a strap-on motor and still hit its orbit offers a kind of demonstrated resilience that pure paper reliability statistics cannot match.
At the same time, any anomaly on a classified mission raises questions that are harder to answer publicly, because much of the detailed data and risk analysis will remain behind closed doors. SSC’s national security framing for GSSAP and the other USSF-87 payloads means that launch reliability is not just a commercial concern, but a factor in how the United States maintains awareness and deterrence in orbit. Until ULA publishes more information about what went wrong inside the solid rocket motor, outside observers will have to rely on the company’s assurance that the problem was contained and that the rest of Vulcan’s systems did their job.
Looking Ahead
Based on ULA’s standard approach to launch anomalies, the company is expected to conduct a detailed investigation into the GEM 63XL motor that misbehaved on USSF-87, although specific steps have not yet been spelled out publicly. The mission page for USSF-87 describes Vulcan as configured for national security work with the VC4S setup, and any investigation will likely focus on whether the anomaly reflects a one-off issue with that particular motor or a broader concern in the SRB production line. The fact that ULA has already isolated the problem to “one of the four solid rocket motors” gives engineers a clear starting point for that work.
For Vulcan’s longer-term trajectory, the key question is how quickly ULA and Space Systems Command are satisfied with the findings and any corrective actions. The same mission documentation that lays out the technical details of the VC4S configuration also positions Vulcan as a central player in future national security launches to GEO. If ULA can show that the anomaly was limited, understood and fixed, the USSF-87 flight may ultimately be remembered less as a failure and more as a stress test that Vulcan passed by keeping its primary mission intact even when one of its boosters did not.
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*This article was researched with the help of AI, with human editors creating the final content.
