Second SLS Mission May Not be Manned As Initially Planned

Space News (5/21, Leone, Subscription Publication, 481) reports that according to Virginia Barnes, Space Launch System (SLS) program manager at Boeing Space Exploration, Boeing and NASA are close to a deal for developing a new Exploration Upper Stage for the SLS when it launches on its second mission in 2021. The new upper stage would allow the rocket to carry heavier payloads that with the Interim Cryogenic Propulsion Stage the SLS will initially use.