Pentagon Frustrated by ULA’s Vulcan Rocket Delays

Backdrop: Written Testimony by Major General Purdy

In a May 14 hearing before the House Armed Services Committee’s Subcommittee on Strategic Forces, Major General Stephen G. Purdy, Acting Assistant Secretary of the Air Force for Space Acquisition and Integration, delivered stark written testimony on the performance of United Launch Alliance’s (ULA) new Vulcan Centaur rocket.

“The ULA Vulcan program has performed unsatisfactorily this past year,” Purdy wrote. He added that major technical issues have delayed four national security missions, even after certification of the initial variant on March 25, 2025.

Delays and Their Root Causes

Originally planned to begin flying national security payloads in 2020, Vulcan has been repeatedly pushed back. Key drivers of the delay include:

• BE-4 Engine Bottlenecks: Built by Blue Origin, the methane-oxygen BE-4 engines each produce 160,000 lbf of thrust. ULA initially targeted six engine assemblies per month but has averaged only two to three, due to turbopump vibration tuning and cavitation concerns in the LOX feed system.
• Composite Tank Qualification: The new BE-4 LOX tank uses a filament-wound carbon composite structure. Non-destructive evaluation (NDE) revealed unexpected matrix porosity that required rework of weld parameters and additional ultrasonic inspection steps.
• Solid Rocket Booster (SRB) Anomalies: Vulcan’s 63-inch-diameter GEM 63XL SRBs, adapted from Atlas V heritage, experienced case joint slippage under thermal cycling. ULA implemented reinforced steel bands and new insulation blankets to stabilize the joints.

Technical Deep Dive: BE-4, Centaur V, and SRBs

BE-4 Engines: The LE 9 architecture uses a single-shaft, oxygen-rich preburner. Engineers have worked through high-frequency pressure oscillations by adding acoustic liners in the combustion chamber and adjusting injector plate orifices.

Centaur V Upper Stage: Upgraded from RL10C-2 to the RL10C-3 variant, Centaur V provides a 22:1 thrust-to-weight ratio and a new composite interstage. Welded thin-wall stainless steel tanks are equipped with Helium pressure regulators to minimize boil-off during coast phases.

GEM 63XL SRBs: Each booster delivers 440,000 lbf of thrust at sea level. New case liners and higher-temperature propellant formulations increased burn consistency but required redesigned thrust vector control (TVC) actuators to handle greater side loads.

Industry Impact and Competitive Landscape

SpaceX’s Falcon 9 and Falcon Heavy have become the default for many national security launches. In April 2025, the Department of Defense awarded SpaceX the majority of the next tranche of launch contracts, reversing ULA’s two-decade dominance.

• SpaceX won approximately 60% of upcoming missions, citing a demonstrated launch cadence of 12–15 flights per year.
• New entrants such as ABL Space Systems (RS1) and Relativity Space (TERRAFORMER) are vying for small-to-medium payloads, though they have yet to secure major national security missions.

Risk Mitigation and Program Management Reforms

To rebuild confidence, ULA and the Space Systems Command (SSC) are collaborating on “risk reduction plans” that include:

1. Model-Based Systems Engineering (MBSE): Digital twins for structural margins, fluid dynamics, and thermal profiles to predict anomalies before hardware build.
2. Augmented Production Lines: Automated laser-welding stations for composite tanks and real-time engine health monitoring using edge-AI analytics.
3. Government Oversight: Federally Funded Research and Development Center (FFRDC) experts embedded on the factory floor to approve each engine and stage test.

Outlook: USSF-106 and Beyond

Vulcan’s first national security mission, USSF-106, is slated for a no-earlier-than July 2025 launch from Cape Canaveral. A Flight Readiness Review (FRR) in late June will evaluate:

• Propellant load and pressurization sequences
• Stage separation and fairing deployment timings
• Telemetry integrity across all vehicle subsystems

Expert Perspectives

“Engine production ramp-up was overly optimistic,” says Dr. Jamie Morin, Senior Fellow at the RAND Corporation. “The supply chain for the specialized composite materials and ultra-high precision turbomachinery has longer lead times than ULA accounted for.”

As NASA prepares for Artemis lunar missions and commercial operators seek reliable heavy-lift vehicles, consistent Vulcan performance will be critical to ULA’s future role in both civil and defense space sectors.

Additional Analysis: Program Funding and Budgetary Outlook

The FY2026 defense budget request allocates $2.2 billion to sustain Vulcan development and engine procurement. Congress may impose milestone-based funding releases to ensure accountability and on-schedule delivery.

Additional Analysis: Supply Chain Resilience

Global shortages of carbon fiber and superalloys prompted ULA to diversify vendors, adding Canadian and European suppliers. The company is also exploring in-house additive manufacturing for engine components to reduce dependency on external foundries.

Additional Analysis: Strategic Implications

A reliable domestic launch provider is vital for national security autonomy. Continued delays could force the Space Force to further widen its supplier base, potentially accelerating procurement of emerging competitors or foreign partners.