According to Thomas Kuhn, normal science is research based upon past scientific achievements of a certain type, those that constitute what he calls “paradigms.”
That is to say, achievements that are “sufficiently unprecedented to attract and enduring group of adherents away from competing models of scientific activity.
Simultaneously…sufficiently open ended to leave all sorts of problems for the redefined group of practitioners to resolve.”
-Thomas Kuhn, The Structure of Scientific Revolutions (Paraphrased here by Jean-Pierre Dupuy)