NASA Taps ULA's Centaur 5 for SLS
NASA has officially selected ULA’s Centaur 5 as the new upper stage for the Space Launch System (SLS) rocket. The decision is a major development for deep-space avionics and will shape the control architectures for future Mars missions, impacting the market for high-assurance embedded systems.
This decision scraps the previously planned Exploration Upper Stage (EUS), a more powerful system designed by Boeing. The EUS was intended to debut on Artemis IV, featuring four RL10 engines to boost the SLS rocket's deep-space payload capacity to over 38 metric tons (84,000 lbs). The Centaur 5 is the existing, flight-proven upper stage for ULA's Vulcan rocket, which has already flown multiple times since January 2024. This move represents a trade-off, accepting the Centaur's lower lift capacity in exchange for faster availability and reduced risk, keeping later Artemis missions on schedule. A key driver for this choice is system heritage, which streamlines integration. The Centaur 5 shares critical avionics and software with the Interim Cryogenic Propulsion Stage (ICPS) used on the first Artemis flights. This includes the Inertial Navigation and Control Assembly, allowing it to interface with the core SLS rocket and Orion spacecraft without major redesigns. Opting for the Centaur 5 also leverages existing ground infrastructure. It is compatible with the current Mobile Launcher 1 at Kennedy Space Center, requiring only minor modifications. This avoids the need for the nearly complete and costly Mobile Launcher 2, which was specifically built for the now-canceled EUS. The sole-source contract requires ULA to deliver flight units for Artemis IV and Artemis V, plus a spare. The first Centaur 5 stage must be at Kennedy Space Center nine months before the Artemis IV launch, which is currently scheduled for no earlier than early 2028.
