[quote=@CowboyCommando]
A bit off topic, but I Remember an novel where black holes the size of pea drops were used in an engine used to approach near light speeds by producing an endless supply of anit-matter with it. Though there were safe self destruct mechanisms that destroyed the black holes before the grew large enough if the ship was critical.
[/quote]That seems to be "hard" sci-fi on par with Tau Zero so I wouldn't draw any conclusions from it.
Well, you can use neutron stars and black holes to make antimatter by gravitational shear effect but the relation is hilariously disproportionate. Think of stellar masses of a blackhole/neutron-star making kilograms of it per year (IIRC). Not to mention rather than the black hole growing you'd need to prevent it to get too light. Speaking of which the biggest issue is that black holes have hilariously high mass if you don't have handwavium/magitech to keep them stable by artificial means. Another point why only my colony ships have it.
Don't wish to bore you here so just in conclusion blackhole engines in real theory are nowhere as amazing as it might seem.