Reconnaissance Office (NRO) to partner with the service on the RS-68 engine work, which is already in progress. The NRO plans to develop an upgraded RS-68A variant for a mission. From that variant, NASA would join with the Air Force to develop a common RS-68B version for use on both the Ares V and the Delta IV, featuring upgrades required by NASA for operability and changes planned by the Air Force for their Assured Access To Space program to improve robustness. Planned modifications to the current RS-68 are:
- Increased power level to 108 percent from the current 102 percent.
- Main injector changes to improve Isp to at least 414.2 seconds from the current 407.7.
- New bearing material to decrease stress corrosion susceptibility.
- Redesigned turbopump pump inlets to incorporate tip vortex suppression.
- Redesigned fuel turbopump second stage blisk to decrease susceptibility to cracks.
- Redesigned gas generator igniter that eliminates squib foreign object debns concern.
- Higher reliability oxidizer turbopump bearing chill sensor.
- Higher reliability hot gas sensdr.
- Redesigned oxidizer turbopump to reduce pre-start and operational helium usage.
- Modified engine start sequence/configuration to reduce free hydrogen on the pad during engine start.
- Redesigned ablative nozzle to accommodate the longer-duration Ares V mission profile.
The increased power level and main injector modifications are included in an engine upgrade program that PWR is implementing under a contract with United Launch Alliance for the RS-68A variant. Changes 3 through 8 are currently conducted under the Air Force Assured Access to Space Program. NASA will work with the Air Force to combine the AATS upgrades with changes 9-11 above, required for Ares V, to produce a common RS-68 B engine variant.