The ACES Stage Concept: Higher Performance, New Capabilities, at Lower Recurring Cost

The Advanced Common Evolved Stage (ACES) concept combines the best features of Atlas and Delta upper stages. We will discuss how ACES leverages and improves upon the stainless steel common bulkhead structure of Centaur which already results in a world-best mass fraction for an H2/O2 stage. ACES incorporates the Integrated Vehicle Fluids (IVF) H2/02 system to eliminate main vehicle batteries, all hydrazine, and most helium bottles, which can all limit mission duration and number of starts. Coupling additional low boiloff technologies with IVF, ACES becomes extensible for week long missions beyond LEO. We will discuss the ability add kits for rendezvous and docking, propellant transfer, and even to convert the stage into an efficient lunar lander. Though the promise of higher performance upper stages and greater extensibility is not new, we now see the potential of realizing these capabilities in a stage that cost no more than the smaller Centaur stage it replaces, which becomes a game changer.