NASA spent approximately $25 billion per year in the 1970s. This is roughly equivalent to $170 billion today. NASA's percentage of the federal government budget dropped from 4.5 percent down to less that one percent between 1969-1986.
NASA and US Department of Defense (DOD), collaborated on thousands of research projects during this period. NASA's research is not always focused on military issues in certain areas. Instead, the agencies shared information in areas of mutual concern. NASA primarily focused on robotic and aeronautics research. NASA may have sub-funded military research in certain cases. However, the Air Force is only reimbursed for specific flight requirements.
NASA's percentage of the federal government budget increased slightly in the 1990s. During the Bush administration, however, this amount dropped again. After that, NASA's portion of the federal budget has steadily declined. NASA's budget never exceeded two per cent of the federal budget over the past few decades.
In addition to the NASA budget, the US also has a military budget of $600 billion. This budget is nearly double that of any other country. NASA's budget only represents 4 percent of the total military budget. This leaves NASA with only a fraction of the money that is available for space exploration.
The question is whether NASA will be able to raise the necessary funds to establish a base on Mars. Currently, NASA estimates that it will cost $450 billion to land humans on the planet by the 2030s. If NASA had the military budget, it would be able to afford a crewed mission to the planet.