An interstellar mission to test astrophysical black holes

Black holes are the sources of the strongest gravitational fields that can be found today in the Universe and are ideal laboratories for testing Einstein's theory of General Relativity in the strong field regime. In this letter, I show that the possibility of an interstellar mission to send small spacecrafts to the nearest black hole, although very speculative and extremely challenging, is not completely unrealistic. Certainly we do not have the necessary technology today, but it may be available in the next 20-30 years. The mission may last 80-100 years, but we would be able to obtain very valuable information about black holes and General Relativity that could be unlikely obtained in other ways.