Explanations of the title:<p>SLS == "The Space Launch System (SLS) is an American Space Shuttle-derived heavy expendable launch vehicle being designed by NASA":<p><a href="https://en.wikipedia.org/wiki/Space_Launch_System" rel="nofollow">https://en.wikipedia.org/wiki/Space_Launch_System</a><p>"engineers who criticize" == legendary Chris Kraft, NASA's first manned spaceflight director, 2013 here:<p><a href="http://www.houstonchronicle.com/news/nation-world/space/article/Sunday-conversation-NASA-veteran-Chris-Kraft-4778332.php" rel="nofollow">http://www.houstonchronicle.com/news/nation-world/space/arti...</a>