"but if we devalued it ...to say 50% of its value .that gives you 2 dollars value for one dollar."
doesn't make sense. Internally, devaluation (I am assuming you are referring to exchange rate devaluation) makes no difference as a $1 is still a $1. It does NOT change the amount of debt that the existing borrowers still have to pay. Yes, it does mean less to the foreigners who lent you the money as they will get back less after converting into their curriencies.
Yes, devaluation will make imports dearer and our exporters cheaper and hopefully we as a country will sell more and over time reduce our debts proportionately as our nation will grow.
On the other hand, if what you mean is our government saying to us that the $1 coin is now worth 50 cents for internal purchasing power purposes, then that is a different story.
The example you gave re Zimbabwe is a devaluation caused by inflation (or supplying falling far behind demand), a different type of devaluation you mentioned in your first post.
