Work progressed with maddening slowness. And meanwhile the Hellik Olav fell outward and outward, on an orbit which would not bend back again until it was three Astronomical Units from the sun. And the ship was out of communication. And the radar, still functional but losing efficiency all the time, registered an ever thicker concentration of meteorites. And the ‘tween-decks radiation count mounted, slowly but persistently.
«I vote we go home,» said Helledahl. Sweat glistened on his forehead, where he sat in his tiny bunk cubicle without touching the mattress.
«Second the motion,» said Bull at once. «Any further discussion? I move the vote. All in favor, say, Ja. All opposed, shut up.»
«This is no time for jokes, Herr Bull,» said Captain Langnes.
«I quite agree, sir. And this trip is more than a joke, it’s a farce. Let’s turn back!»
«Because of an encrustation on the hull?»
Surprisingly, gentle Torvald Winge supported the skipper with almost as sharp a tone. «Nothing serious has yet happened,» he said. «We have now shielded the drive tubes so that the barnacle growth can’t advance to them. As for our communications apparatus, we have spare parts in ample supply and can easily repair it once we’re out of this fantastic zone. Barnacles can be scraped off the radar arms, as well as the vision parts. What kind of cowards will our people take us for, if we give up at the first little difficulty?»
«Live ones,» said Helledahl.
«You see,» Bull added, «we’re not in such bad shape now, but what’ll happen if this continues? Just extrapolate the radiation. I did. We’ll be dead men on the return orbit.»
«You assume the count will rise to a dangerous level,» said Winge. «I doubt that. Time enough to turn back, if it seems we have no other hope. But what you don’t appreciate, Erik, is the very real, unextrapolated danger of such a course.»
«Also, we seem to be on the track of an answer to the mystery—the whole purpose of this expedition,» said Langnes. «Given a little more data, we should find out what happened to all the previous ships.»
«Including the Chinese?» asked Bull.
Silence descended. They sat in mid-air, reviewing a situation which familiarity did nothing to beautify.
Observations from the Martian moons had indicated the Asteroid Belt was much fuller than astronomers had believed. Of course, it was still a rather hard vacuum… but one through which sand, gravel, and boulders went flying with indecent speed and frequency. Unmanned craft were sent in by several nations. Their telemetering instruments confirmed the great density of cosmic debris, which increased as they swung further in toward the central zone. But then they quit sending. They were never heard from again. Manned ships stationed near the computed orbits of the robot vessels, where these emerged from the danger area, detected objects with radar, panted to match velocities, and saw nothing but common or garden variety meteorites.
Finally the Chinese People’s Republic sent three craft with volunteer crews, toward the Belt. One ship went off course and landed in the Pacific Ocean near San Francisco. After its personnel explained the unique methods by which they had been persuaded to volunteer, they were allowed to stay. The scientists got good technical jobs, the captain started a restaurant, and the political commissar went on the lecture circuit.
But the other two ships continued as per instructions.
Their transmission stopped at about the same distance as the robot radios had, and they were never seen again either.
After that, the big nations decided there was no need for haste in such expensive undertakings. But Norway had just outfitted her own spaceship, and all true Norwegians are crazy. The Hellik Olav went out.
Winge stirred. «I believe I can tell you what happened to the Chinese,» he said.
«Sure,» said Bull. «They stayed on orbit till it was too late. Then the radiation got them.»
«No. They saw themselves in our own situation, panicked, and started back.»
«So?»
«The meteorites got them.»
«Excuse me,» said Langnes, obviously meaning it the other way around. «You know better than that, Professor Winge. The hazard isn’t that great. Even at the highest possible density of material, the probability of impact with anything of considerable mass is so low—»
«I am not talking about that, captain,» said the astronomer. «Let me repeat the facts ab initio, to keep everything systematic, even if you know most of them already.
«Modern opinion holds that the asteroids, and probably most meteorites throughout the Solar System, really are the remnants of a disintegrated world. I am inclined to suspect that a sudden phase change in its core caused the initial explosion—this can happen at a certain planetary mass and then Jupiter’s attraction gradually broke up the larger pieces. Prior to close-range study, it was never believed the asteroidean planet could have been large enough for this to happen. But today we know it must have been roughly as big as Earth. The total mass was not detectable at a distance, prior to space flight, because so much of it consists of small dark particles. These, I believe, were formed when the larger chunks broke up into lesser ones which abraded and shattered each other in collisions, before gravitational forces spread them too widely apart.»
«What has this to do with the mess we’re in?» asked Bull.
Winge looked startled. «Why… that is—» He blushed. «Nothing, I suppose.» To cover his embarrassment, he began talking rapidly, repeating the obvious at even greater length:
«We accelerated from Earth, and a long way beyond, thus throwing ourselves into an eccentric path with a semi-major axis of two Astronomical Units. But this is still an ellipse, and as we entered the danger zone, our velocity gained more and more of a component parallel to the planetary orbits. At our aphelion, which will be in the very heart of the Asteroid Belt, we will be moving substantially with the average meteorite. Relative velocity will be very small, or zero. Hence collisions will be rare, and mild when they do occur. Then we’ll be pulled back sunward. By the time we start accelerating under power toward Earth, we will again be traveling at a large angle to the natural orbits. But by that time, also, we will be back out of the danger zone.
«Suppose, however, we decided to turn back at this instant. We would first have to decelerate, spending fuel to kill an outward velocity which the sun would otherwise have killed for us. Then we must accelerate inward. We can just barely afford the fuel. There will be little left for maneuvers. And… we’ll be cutting almost perpendicularly across the asteroidal orbits. Their full density and velocity will be directed almost broadside to us.
«Oh, we still needn’t worry about being struck by a large object. The probability of that is quite low. But what we will get is the fifteen kilometer-per-second sandblast of the uncountable small particles. I have been computing the results of my investigations so far, and arrive at a figure for the density of this cosmic sand which is, well, simply appalling. Far more than was hitherto suspected. I don’t believe our hull can stand such a prolonged scouring, meteor bumpers or no.»
«Are you certain?» gulped Helledahl.
«Of course not,» said Winge testily. «What is certain, out here? I believe it highly probably, though. And the fact that the Chinese never came back would seem to lend credence to my hypothesis.»
The barnacles had advanced astoundingly since Bull last looked at them. Soon the entire ship would be covered, except for a few crucial places toilfully kept clean.
He braced his armored self against the reactive push of his cutting torch. It was about the only way to get a full-grown barnacle loose. The things melded themselves with the hull. The flame drowned the sardonic stars in his vision but illuminated the growths.