The bulkheads of the mighty battleship rocked with the song welling from five thousand throats. As the young, eager voices swelled into the chorus of "The Spaceman's Hymn," Vice-Admiral Jack Harrigan felt a lump grow in his own throat. Captain Mike O'Brien, short, muscular and definitely Irish, joined the admiral at the balcony hatch; together they looked down upon the huge ship's auditorium. "It's a long, long way to the Milky Way ..." the chorus rose, fell, faded and died. Harrigan nodded to O