Grantline had joined us in the control turret. "How far would you say, at a rough guess, that ship is from us now?"
"Thirty thousand miles; about that." Drac scanned his page of calculations. "Impossible to gauge with any exactness; they change their pace so often and I can't figure out how large the damn thing is."
"Say they've got a forty thousand velocity; added to our ten, that's fifty."
"And we're accelerating. In half an hour we'll be within range."
"But there's something wrong," I persisted.
For several minutes now I had been aware that the Cometara was acting strangely. A sluggish response to the controls, I thought, but when I called engine chief Franklin, he had not noticed it. Yet I was certain.
Grantline stared at me. "Something wrong?"
"Yes. Drac, try orienting us. I did it ten minutes ago." I shoved him at my equations, giving the angles with the Sun, Earth and Moon which we should now have. "There's our flight course as it ought to be. Measure how we're heading, actual position. If it's what it ought to be, with the plate-combinations I'm using, then I'm crazy."
"Oh, you're just naturally apprehensive," Grantline said.
But we were not where we should be. The Cometara was off her predetermined course. And then I realized the factor of error. There was a gravitational force here for which I was not allowing. The error was not within the Cometara; she was responding perfectly. But there was a force upon her, and not that of the Sun, Earth, Moon or the distant starfield. I had calculated all of these. It was something else. Some gravitational pull, so that we were not upon the course of flight we should have been on.