Mathematician Louis Crane, who was a co-author of a 2009 study on the feasibility of using black holes' Hawking radiation as power source for starships, has suggested a new usage for the hypothetical technology. In his most recent study Crane offered to start tracking objects that look like starships operating on this technology, so far inaccessible to humanity, but which could be used by aliens.
Such ships will look like small spots that are hotter than any other natural objects and emit huge amounts of particles and gamma rays as a by-product of the black hole's operation. Crane added that the gamma radiation cone will appear red-shifted during the first half of such a starship's voyage and blue-shifted during the second half as the ship turns around to begin deceleration.
The 2009 paper written by Crane and Shawn Westmoreland suggested that a black hole with a 2.8-attometer radius will have a lifespan of about a century and can produce 15 petawatts of power, thus being suitable for powering the ship and accelerating it close to the speed of light. The problem with such a singularity drive is to efficiently direct the Hawking radiation emitted by the black hole. One of the ideas is to bombard a parabolic reflector with the radiation to propel the ship forward.
However, the authors of the research admit that at the moment humanity doesn't possess the materials and technology needed to build such a vessel. Another difficulty is that quantum gravity effects produced by black holes remain poorly studied and they can either make the creation of the drive much easier or make it close to impossible.