At current trajectory, interest costs will exceed 50% of all tax revenue within 30 years. See footnote 5:

https://media4.manhattan-institute.org/wp-content/uploads/a-...

The author took the CBO's budget projections and adjusted them for "false sunsets", i.e. the tax cuts that were supposed to expire before they were extended, and the fake spending cuts written into the law that will never happen, i.e. the FRA.