The SLS rocket, which made its inaugural launch in November 2022, utilizes four RS-25 engines per launch, with 16 engines salvaged from retired Space Shuttles. However, as the available stock of RS-25 engines depletes (since all SLS engines are expendable), NASA plans to transition to the RS-25E engines being developed by Aerojet Rocketdyne. These newer engines are expected to be 30 percent cheaper and 11 percent more powerful. Additionally, the SLS employs solid rocket boosters provided by Northrop Grumman.
Unfortunately, the use of older technologies has not yielded the anticipated budgetary benefits for NASA. The audit report indicates that the cost overruns and delays are attributed to several interconnected factors, including the assumption that leveraging heritage technologies from the Space Shuttle and Constellation Programs would lead to significant cost and schedule savings compared to developing entirely new systems for the SLS. However, the complexity associated with developing, updating, and integrating new systems alongside existing heritage components has proven to be far more challenging than initially anticipated.
