Eltab
Lord of the Hidden Layer
One option would be to use it to break down matter on the asteroid, turn it into pico-printer-gel manufacturers, and then use those in turn to break down more of it, in an exponential replication loop. Once the whole thing is turned into printers, they then turn each other into propulsion units and fly themselves away.
The last third of 2010. It makes a good plotline.
But the author wants Our Heroine to be in peril at the climax, not watching safely from a short distance.
Maybe her suit gets infected with the 'make motors' nanite-virus, too? Or would that distract from the big picture?