The first SLS/Orion launch, EM-1, has been delayed until 2018 due to
late delivery of the ESA-produced Service Module for Orion. Now it
looks like the SLS rocket itself will be the source of an even bigger
launch delay.

A welding problem with the new, high-tech welding process used for the
SLS core stage apparently has a problem that will delay launch of the
vehicle until at least 2019, if not into 2020.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw