They need GDP to grow faster than debt in order to avert a Malthusian event.
If debt/GDP gets too high then the cost of servicing your debt can accelerate faster than your ability to service it and ultimately outrun you.
This is how South American currencies collapse.
So the Fed actually needs high inflation in order to bring down debt/GDP ratio because GDP inflates with inflation, whereas debt does not.
They probably want 5-10% inflation, not so hot to trigger capital flight but hot enough to inflate away some debt.
Not sure they will touch rates. They will use esoteric tools now that they have the patient sedated and the thorax open.