There is no "interest" on the social security funds which the Federal govt moved to general spending. Because that money is not "invested".
The national highway system is paid through fuel taxes, which is equivalent to the kind of direct link between taxation and spending that you worship with social security but forget so conveniently.Discretionary funding does more than you understand. NASA falls under that, so does the national high way system. Those two things have more than paid off in economic benefits than their cost. I want efficient gov not ideological knee jerk hate for gov and slashing just to slash.
NASA has not "paid off" in economic benefits more than its cost at all. All the supposed "spin offs" of NASA are propaganda.