They ' ll never see it coming <| sep |> Solar ? If you aren ' t going far , that ' s great . Say between Earth and Mars , get past Mars and it starts to not be worth it . Juno has 24 square meters of PV panels to generate a pitiful 165170 w out at Jupiter . BeamedNogo . The Moon is 3 light seconds away . Shine a laser at the moon , by the time the light reaches the moon it has gone from that tiny dot leaving the diode to a circle of light roughly 250 miles across . You ' ll have similar spread from any other part of the radio spectrum . Low output reactors and patience ? Pretty much it . If you wanted to do send probes as messages in a botle to other stars that were nothing more than hey we exist back where this thing came from you could slap some golden records on a tube that contains a power supply and the drive and send it off on its merry way . Depending on how long your power source lasts you might get up to a decent speed , still it would be thousands or hundreds of thousands of years until they made it to their destination and went screaming by until eventually being captured or smashing into something .