Wilson asked, "Is that nominal or is that placed on the minus side?"
"The spot is placed to give the maximum factor of safety."
"Good."
"Now, after considering the probable velocity of escape from Seventy-nine, which would be a lifeship leaving the mother vessel at a ninety-degree relative course at full lifeship speed, we find a vector combination of velocities and courses that diverge from the main course."
From the red knot another line went out at a small angle to the original course, thin and red.
"But because we have no way of knowing what the axial attitude of Seventy-nine was at the moment of escape, the volume of probability now becomes a cone."
The angled red line revolved about a green course line describing a thin cone, its base pointed toward the star, Castor. As the line revolved about the axis of the cone, it left a faint residue behind it, which became a thin, transparent cone.
Manning said, "Our field of operations lies within this cone."
Someone running the projector went to work. The scene expanded until the thin red cone filled the screen and seemed to project deep into the room, its apex almost at the eyes of the watchers. Then a polar pattern appeared across the cone near the apex, a circular grid marked off in thin white lines, each line numbered, each area or segment, marked with a letter.
Down the room where the cone was larger, another grid appeared similarly marked.