We headed for the Penrose Institute to perform the calculations. Mary McAndrew told us that she could not come, she had to pay some attention to “poor neglected Fazool.” But I was to let her know what we found.
“I know he’s surely dead,” she said to me as we left for Equatorport. “He was a wicked, obstinate, reckless man. But the two of us had some great times, and I was awful fond of Heinrich. Why, I was even faithful to him.”
It would have been unkind to ask for how long.
Mac and I headed for the Institute, and at first everything went according to plan. I delved into the old data bases and found the flight plan of the Fafner. Among the listed on-board equipment, tantalizingly, the manifest included the enigmatic item, “strong field modifier, prototype.”
I learned the exact second of the ship’s departure. I found its nominal destination, though that could change through subsequent course corrections or changes of mind. I obtained a complete list of subsequent engine firings, which even without the record sent back from the Fafner’s inertial navigation system would allow us to pinpoint the ship’s last known location. After all the engine firings, a certain stochastic element affected the Fafner’s movements depending on the vagaries of gravitational perturbation by small bodies and variations in solar wind. But natural body positions for anything substantial were in the data banks on an hour-by-hour basis, and the programs to compensate for their effects were routine.
The calculations took a while, even with McAndrew’s talent for instant shortcuts. Once we had answers we borrowed the synthetic aperture distributed observation system for a few days and surveyed the sky sector where the Fafner should be found.
Result: nothing. Not a sign. No Fafner, not in the region we had defined as most probable or in one ten times as big in all directions. The ship had disappeared.
I checked the calculations, redoing everything the long way. The Fafner was not a big ship, nothing to compare with a cargo carrier or even a large passenger vessel, but it was thirty meters long and almost fifteen across. Anything that size would stand out prominently on the observations made by the big scope, especially when you used a time exposure to sort out moving objects within the Solar System from the fixed celestial background. Comparison with known natural bodies ought to do the rest.
I found nothing wrong with McAndrew’s calculations. He checked my checking. That took two more days. Finally we were ready to admit defeat. By this time a dozen others at the Institute were taking an interest. McAndrew phrased the dilemma for all of us. “Objects just can’t disappear. Here are the possibilities: The Fafner might have totally disintegrated. It might have hidden away inside another object. Or it might be deliberately covered with nonreflective material at the wavelengths used by the Institute scopes.”
“Or stolen away by aliens,” I added. I was tired.
McAndrew nodded as though that was a serious possibility. “In any case,” he said, “we’ve gone as far as we can just sitting and looking.”
“The ship can’t be far away from where we calculated,” I said. I could see where the discussion was heading, and I knew that we faced a very tough job. “It’s in the Inner System, and near the plane of the ecliptic. In the Asteroid Belt, almost certainly.”
McAndrew nodded and looked gloomy. “Aye. Wouldn’t you just know it’d be that way?”
The others muttered vague expressions of sympathy.
To see why, imagine that you are asked to look for something small. Would you rather search a large volume or a small one?
The answer to that question depends where you are and what you are seeking. The region of the Solar System that includes the Sun, planets, moons, asteroids, and the odd collection of misfit bodies forming the Edgeworth-Kuiper Belt is a substantial volume; it is shaped like a flat pillbox, about thirty billion kilometers across and maybe forty million deep. Say, a billion billion cubic kilometers of volume altogether. But that’s infinitesimal compared with the space bounded by the inner edge of the Oort cloud. There, we are talking a spherical region with a radius of a twentieth of a light-year. The volume in cubic kilometers is a number with thirty-five zeroes, too many for me to be comfortable with. You can subtract the volume of the pillbox, and it makes no noticeable difference.
The odd thing, though, is that inside the pillbox it’s much harder to find something. And if you had to pick one place where the search is more difficult than any other, the Inner Belt of the asteroids is where you’d least like to be.
The key word is clutter. There are far too many natural bodies in orbit. The Asteroid Belt contains everything from substantial bodies like Ceres, seven hundred and fifty kilometers across, all the way down to house-sized boulders, pebbles, and grains of sand. One good rule of thumb is that for every object of a given size, there will be ten times as many one-third that size.
The data bases at the Institute keep dynamic track of every body of any size, down to ten meters across. The Fafner was much bigger than that, so it ought to have been picked up in our search. Recognize that it hadn’t been, and where does that leave you? You know there are countless millions of objects near where the missing ship ought to be, and you have no idea at all why your original search failed.
So we would fly out there and take a look for ourselves, and hope that our human brains could spot an anomaly able to fool the smartest computers in the Solar System.
How? I had no idea.
McAndrew did. “If it’s been blown apart to its component atoms,” he said, “we’ll never find it. But if it’s still in one piece, there’s a way that can’t fail.”
We were preparing to leave, and we were not using a ship with McAndrew’s balanced drive. Instead he had picked out an old touring pinnace with a one-gee acceleration limit. After my initial surprise I decided that I knew why (it would turn out later that I was wrong). McAndrew, it seemed to me, wanted time to think. He’d never admit it, but his pride was hurt. It was bad enough that somebody would come up with a basic idea that he had missed, in an area of theoretical physics where he had thought longer and harder than any person alive. That the somebody was his own father — the father who had run off and deserted him and his mother — was even worse.
As the Driscoll eased away from the institute, I compared travel times. Even the most minimal ship equipped with the balanced drive was capable of continuous forty-gee acceleration. With that performance, our destination would have been a mere seventeen hours, standing start to standing finish. On the other hand, at the leisurely half-gee best suited to the Driscoll’s engines, we faced a journey of close to a week.
All right for McAndrew, perhaps; he was sitting barefoot, staring vacantly at the cabin wall and cracking his finger and toe joints in a way that I always found infuriating. I knew from experience that he was likely to sit for days, eating his meals like a zombie and washing only at my insistence. Meanwhile, what was I supposed to do, here in a ship that flew itself?
I reviewed everything we had learned so far. Heinrich Grunewald’s paranoia had not ended when he left Mary McAndrew. The Fafner required a crew of three when it flew in cislunar space. Upon leaving that controlled region, Heinrich as soon as possible had the other two men ferried back to Earth station. He continued alone. His last recorded engine burn placed him in stable orbit in the middle of the Asteroid Belt. Any new engine burn would have been detected. None had been recorded. Any explosion in that location powerful enough to destroy a ship would have been seen. No instruments, on Earth or elsewhere, had seen such evidence.