It may be theoretically possible for the Fed to manipulate interest rates so they remain low forever. So I ran another scenario with interest rates never rising above 3%. Everything else from the prior projection remains the same. This extends the tipping point until 2040.
I don't show all the detail here, but the deficit still never drops below $1 trillion per year. And the deficit first tops $2 trillion in 2028, after which things rapidly deteriorate. So interest paid is not the cause of the crisis. The crisis, to reiterate, is out-of-control Social Security, Medicare, and Medicaid costs.