Louis Crane has come up with an idea for an interstellar drive: black-hole powered spaceships, fueled by singularities made in robot-run solar power laser factories hovering just over the sun. It's fantastic science fiction, but unfortunately some seem to have forgotten the second word in that phrase.
The starship proposed might as well be called Enterprise. Imagination is incredibly important in all areas of science, driving us to discover and derive understandings beyond our own, but that's not an excuse to stick on a few equations and call it actual science. The Crane concoction is another unfortunate example of someone waving their hands over a bunch of real equations, shouting "in the future!" and claiming responsibility for actually doing work.
Which we wouldn't even mind, except the paper and its proponents trash other options to make keeping a black hole in the boot look more attractive. A New Scientist article rubbishes solar sails and antimatter by saying "these ambitious schemes have their shortcomings and it is doubtful they could really go the distance," and in the very next sentence puts forward dark matter and portable black holes instead. You know, practical options. Instead of solar sails (which have already been shown to work on some scale) or a fuel which by its very nature would be the most efficient fuel possible.
Crane says "antimatter is hugely inefficient to make in the first place, and it is dangerous stuff - if it touches your spacecraft, it blows it to kingdom come." He apparently has a different idea of 'dangerous' than we do, one that's entirely compatible with towing a million ton black hole along just behind your craft. His idea is to instead use a black hole as a battery, focusing an immense amount of energy into a single point using a spherical gamma-ray laser arrangement, (somehow) built in space and fueled by a two hundred and fifty kilometer solar array you've (somehow) built in space close to the sun. You then (somehow) move the black hole into the end of your spaceship, and let Hawking radiation escaping from the event horizon (somehow) drive your ship forward while (somehow) being held in place and (somehow) not slowing the whole thing to a crawl with its literally space-ripping mass.
You might think we're being unnecessarily critical. We're not. We love the idea, but you don't get to criticize other technologies for being impractical (he bashes the dark matter rocket too) while depending on imaginary futurenauts to invent fifteen new types of science for your plan. Every single step requires his descendants actually building everything (all covered under the armor of "this is only preliminary" in the introduction, of course) in order to render the few Hawking equations he uses relevant.
In claiming his own idea is more reasonable, he's demanding that all future science only invent imaginary technologies (and at one point he uses the phrase "army of robots" in what's allegedly a real scientific paper) which benefits his scheme - because what are the odds anyone will work on antimatter, the most efficient and interesting substance in existence - or dark matter, the most interesting one that might not be? Especially since his whole scheme is to use a black hole as a vast battery, when - in fantasy-future-land - antimatter is already the most efficient energy storage there is?
It's very simple: if you're going to your imagination in equations and upload it onto arxiv, that's awesome. We love that. But don't mock the work of others from a high horse that's a cyborg unicorn.