An anonymous reader writes: We often decry the state of funding to NASA. Its limited scope has kept us from returning to the moon for over four decades, maintained only a minimal presence in low-Earth orbit, and failed to develop a capable asteroid defense system. But why is funding such a problem? Jason Callahan, who has worked on several of NASA's annual budgets, says it's not just NASA's small percentage of the federal budget that keeps those projects on the back burner, but also competition for funding between different parts of NASA as well. "[NASA's activities include] space science, including aeronautics research (the first A in NASA), technology development, education, center and agency management, construction, maintenance, and the entire human spaceflight program. The total space science budget has rarely exceeded $5 billion, and has averaged just over half that amount. Remember that space science is more than just planetary: astrophysics, heliophysics, and Earth science are all funded in this number. Despite this, space science accounts for an average of 17 percent of NASA's total budget, though it has significant fluctuations. In the 1980s, space science was a mere 11½ percent of NASA's budget, but in the 2000s, it made up 27 percent."