"United Launch Alliance First RS-68A Hot-Fire Engine Test a Success" (Press release). United Launch Alliance, su ulalaunch.com, 25 settembre 2008. URL consultato il 30 settembre 2008.
«Currently, the RS-68 engine can deliver more than 660,000 pounds of sea level thrust and the upgraded RS-68A will increase this to more than 700,000 pounds. The RS-68A also improves on the specific impulse, or fuel efficiency, of the RS-68.»