NASA's budget for 2014 was $17.647 billion, which is approx 0.5% of US federal government spending [1].
Total ESA budget for 2015 was €4.28 billion (US$5.51 billion) [2].
Everyone else (including Russia) spends not very much at all.
[0] https://en.wikipedia.org/wiki/List_of_countries_by_military_...
[1] http://usich.gov/resources/uploads/asset_library/FY2015_Budg...
Homelessness is certainly an important problem, but is it more important than (for example) tackling antibiotic resistance ($450 million budget in FY2014 [1])? For any deserving issue/problem it is possible to play this game all day, as illustrated by the Fallacy of relative privation [2].
[1] https://www.whitehouse.gov/sites/default/files/microsites/os...
[2] https://en.wikipedia.org/wiki/Fallacy_of_relative_privation