As our country’s partisan roistering continues its crescendo, the adventurous Ars Nova is presenting a space-travel yarn, set 300 years from now, that speaks to the autocratic tendencies of the current regime in Washington, D.C. Rags Parkland Sings the Songs of the Future, subtitled A Science-Fiction Folk-Concert Musical, features 15 numbers in a variety of styles composed by Andrew R. Butler.