When the alarm signalled the first whiff of the atmosphere of the next planet on his route, Herl Hofner stopped chinning by his strapping six-foot self and left the little gym. Slipping into the swivel chair at the desk he clipped the pile of loose papers into an empty niche at the side of the desk, spun the chair around to the instrument panel of the Krylla . Dialing with his left hand, he swept the bank for incoming signals while his right hand adjusted the microphone frequencies. "Class M-for