As Commodore Theodore Wilson eyed the infrawave detector presentation
on the dome of the detector ship, he groaned. The presentation of
targets was stronger now. At the apex of the dome was the lifeship, its
response waxing and waning, but always strong enough to stay visible
even at its lowest ebb.
Some forty or fifty degrees down the hemisphere was the stronger
response of the enemy warcraft, hanging motionless in the dome. The
group of spacecraft that had come with it were dispersed in some
complicated pattern. Most of these were lost in the tricky shift of
the spurious lighting of the dome. Others had disappeared completely
because they were out of range.
"Pilot!" cried Wilson. "Can't we pour on more power?"
The pilot rapped his levers with the heel of his hand and shook his
head slowly. "Sorry, sir. We've been at the top of the military
emergency range all along." Occasionally he looked back over his
shoulder at the motionless enemy response in the dome.
No man in the detector room needed a fancy ranging detector and a
computer to know the worst. The infrawave would not range, but it was
good enough for this. The inefficient detector and knowledge of one of
the simpler facts of navigation told the whole unhappy story.
When the angular position of a distant object remains constant to the
observer in a moving vehicle, they are on collision course. And so
long as that observed angle does not change, they will remain on that
collision course, right up to the bump. Distance, or angle of attack
does not contribute or detract. The fact remains.
The object may be stationary, or the observer may be stationary and
the object moving, or both may be moving, but so long as that angle
remains constant, they will collide. One may be curving and the other
in acceleration or deceleration, but if the observed angle does not
change, it's still collision.
In fact, there are only a couple of exceptions to this. One is when the
subject object is astern and moving dead away _from_ a collision, or
what might have been one before either ship moved onto the course. The
other is when a circle is cut with the object at dead center. Make it a
spiral and you have your course of danger.
Put it in space, or on the sea, or in the air, or across the land, and
the same holds true.
So the fact that the enemy warcraft hung at some forty or fifty degrees
and did not change its position meant that the detector ship and the
enemy warcraft were going to meet! And undoubtedly at the point where
the lifeship would be in the middle because the enemy was obviously
heading for that spot. When they hit, the enemy warcraft would come
through the detector dome exactly where its response now registered.
"Can't we stretch something?" demanded Wilson.