Spoiler: the focal point is 3.5x the distance to Voyager 1.
if to use existing nuclear reactor tech and already existing, as tested by NASA (and drives Starlink satellites), ionic drive - about 3500 ISP - that focal point would take about 10 years to reach. I hope that SpaceX flights to Mars will, after the probably first chemical ones, be done using ionic drive with solar as it is just faster, thus getting tech developed and with adding nuclear for beyond Mars - so in 10-20 years we'll have the stuff flying. (note that "small" reactors - 100MW - we have for submarines, and with MS, ORCL, GOOG, AMZN getting into nuclear we'll have such small reactors productized into normal commercial use which will simplify space use too as commercial use require higher reliability/etc. compare to military)
They're hesitant to put nuclear reactors in a rocket though, in case it goes wrong.
that will pass. With Starship you can deliver reactor into orbit in a "safe box" such that if anything happens with the rocket during launch and acceleration the box with the reactor will fall without breaking apart. Such box can be made in self-stabilizing shape similar to Dragon capsule so that it will slow down in atmosphere. One can imagine 10 cm thick tungsten and steel walls, etc. for the "box" to not break on fall/reentry or in the rocket explosion. And you don't need it for the whole reactor, only for the nuclear fuel.