Not all that sci-fi.
After all, successful tests have been conducted (though rather smaller in scale) on the theme of lightsails etc. So, science: yup, it's science. The method has been demonstrated to work. Fiction: it used to be fiction, but isn't any longer. They're putting it into practice.
I love it when a plan comes together... and my Kudos go to the likes of Asimov, Heinlein, Hildebrandt, Clarke, L.N. Smith, et infinite al for having seen the possibilities decades before we could do it.