Not sure if anyone else has said this first but, jets must use fuel*, fans do not have too. If you were using a small nuclear reactor it would make loads more sense in-atmosphere to use fans/rotars rather than jets because as long as the reactor can power the fans/rotars, it can provide lift. It makes sense for a longsword or pelican to use jets and rockets because they must fly at very high altitudes and even in space, fans do not do well in the upper atmosphere and not at all in space. A vehicle like this does not need to reach high altitudes--it probably couldn't. An aircraft using a small (one or two ton) nuclear reactor and fans could fly for months, maybe years, without refueling once.
Still, there is a possibility that these fan-like structures on top of the aircraft actually are intakes for a jet engine beneath their structure. It would be a little like one of these http://wings.avkids.com/Book/Propulsion/Images/trboprp.jpg except the air would have to be ducted under the structure, unless they have magically miniturized jet engine technology.
(*I suppose you could design a jet engine that used energetic emissions from the reactor to super heat air, thus providing the same function as fuel.
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