Boeing Upper Stage Will Power First Two SLS Launches

It all seems a little too familiar.  Nearly 50 years after NASA used the RL-10 engine to power the second stage of the Saturn 1 launch vehicle while work was proceeding in developing the J-2, NASA is apparently once again turning to the venerable engine for the upper stage of the first two flights of the SLS. This time it is work on the derivative J-2X which is being slow walked.  In case you haven’t been paying attention to the complete plan, the original version of the SLS scheduled for the first two flights will feature exactly none of the major propulsion components which will  supposedly be used in the later versions.