Junius Harleman, chief of the National Aeronautics and Space Administration, wants to prolong the life of NASA just long enough for him to have time to get the directorship of a more viable agency so he accepts the proposal for a low budget gyrogravitics project which, against all expectation, does open up the Solar System for colonization. In Robert Heinlein's Future History, the "Man who sold the Moon," DD Harriman, is an entrepreneur who invests his money, time and energy into getting mankind onto the Moon and into space.
So Harriman gets mankind out into the Solar System by his personal efforts whereas Harleman gets mankind out there by accident and the similarity between their names cannot be a coincidence. The joke continues as the gyrogravitics team is assembled:
sceptical specialists welcoming the opportunity to use expensive equipment for basic research;
"...graduate students desperate for thesis material..." (p. 30);
engineers unable to hold down better jobs.
And yet: "Harleman felt rather proud when he had finished rounding up that crew. It hadn't been easy..."! (p. 30)