Spacecraft rotating to generate artificial gravity through "centrifugal force" are commonplace in science fiction but not in reality. Considering the problems in long missions (among others: bone loss, muscle loss, fluid redistribution, permanent visual impairment, feet disease, lowered immune defence, increased growth of dangerous microbes like ecoli, increased exposure of eyes and skin and lungs to freefloating microbes and dust), why isn't this method used?
Also, wouldn't artificial gravity (radial acceleration) simplify the design and increase the reliability of technical equipment which use moving parts, flows of fluids or gasses or need to distribute heat? Wouldn't eliminating microgravity eliminate the cause of all these severe and very diverse problems which today have no other working solution?
I understand that a large structure with moving parts as in 2001 is currently unfeasible, but how about a simple tether with the craft and a counterweight at the ends, like bolas? Does it interfere with communications or require the craft/tether to be much stronger?