was cheapest (by far), but that it was also the most technologically sound and least risky. (See attached summary of that document from NSF's niwax.)

SLS is here and will soon (hopefully!) be flying. Without it there is no current NASA lunar program. Be happy that SpaceX's new pic.twitter.com/AVQ0wTnSeF

— Sylvia Keeps (@BeastsInJars) April 19, 2021