The Senate Appropriations Committee (SAC) is working toward providing the Air Force RD-180 relief in the form of additional national security waivers, Sen. Richard Shelby (R-Ala.) said Thursday.Lawmakers are working on their omnibus spending bill for the remainder of fiscal year 2016. The current continuing resolution (CR) expires in December. Shelby is on the Senate Appropriations defense subcommittee.United Launch Alliance (ULA) did not respond to the Air Force’s request for proposals for the service’s first competed launch in years: a…