question:  Why were there no guards present in the ship?
context: "Beg pardon, thir," he said with his racial lisp, "thereth thome one to thee you in the main lounge." The Spacemen's was a sanctuary, a rest club where in-coming pilots and crewmen could relax before leaving for another voyage. The rule that no females could pass its portals was strictly enforced. There she stood before a frantically gesticulating desk clerk, leaning on her faded green umbrella. If Annabella C. Flowers wrote a novel, and the locale was the desert of Mars, she packed her carpet bag and hopped a liner for Craterville. If she cooked up a feud between two expeditions on Callisto, she went to Callisto. Before I realized it, I was following her through the lounge and out to the jetty front. A theater to the grizzled colonials on this side of the planet meant a shack on stilts over the muck, zilcon wood seats and dingy atobide lamps. It read: ONE NIGHT ONLY DOCTOR UNIVERSE AND HIS NINE GENIUSES THE QUESTION PROGRAM OF THE SYSTEM As we strode down the aisle a mangy-looking Venusian began to pound a tinpan piano in the pit. On the stage four Earthmen, two Martians, two Venusians, and one Mercurian sat on an upraised dais. On the right were nine visi sets, each with its new improved pantascope panel and switchboard. Before each set stood an Earthman operator. When it had subsided, the man continued: "As most of you are familiar with our program, it will be unnecessary to give any advance explanation. I will only say that on this stage are nine visi sets, each tuned to one of the nine planets. For every question missed, the sender will receive a check for one thousand planetoles . Questions from Mars, from Earth, from Saturn flowed in the visi sets. Isolated miners on Jupiter, dancers in swank Plutonian cafes strove to stump the experts. It was outside under the street marquee that a strange incident occurred. Kagors, of course, had an unpleasant history of persecution since the early colonization days of the Red Planet.
output:  The ship was self-operating to defend
options:  They had all been eliminated by the Green Flames  the metal envelope was the only guard  The ship was well hidden to not need guards  The ship was self-operating to defend