Read Online Cold as Ice by Charles Sheffield - Free Book Online Page B
Authors: Charles Sheffield
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rising through the atmosphere on the smoky column of its Moby drive. In twenty minutes it would pass through the colorless layers of ammonium hydrosulfate to reach the base of blue-white ammonia clouds. Fifteen minutes more and the Von Neumann would be at full thrust, striving upward to break the great planet's gravitational bonds.
The other two were quietly harvesting. Monstrous intake venturis, hundreds of meters across, sucked Jupiter's atmosphere into their broad, beetle-shaped interiors. Hydrogen was vented at the rear, except for the tiny amount needed to supply the Moby fusion drive. Traces of sulfur, nitrogen, phosphorus, and metals were separated and hoarded, awaiting the time when enough of those raw materials had been collected. Then the Von Neumann would create an exact copy of itself, and release it.
Helium, a quarter of the mass of the Jovian atmosphere, remained to be processed. Most of it, like the dross of a mining operation, was of no interest. The precious nugget was the isotope helium-3, ten thousand times as rare as helium-4. The Von Neumanns painstakingly separated the two components, vented the common isotope and stored the lighter molecules in liquid form. When a hundred tons had been collected, the storage tanks would be full and the Von Neumann ready to begin its long ascent to planetary escape.
But that triumphant exit was not the event that Wilsa had come to witness. Anomalous signals had been arriving at Hebe Station, orbiting Jupiter half a million kilometers above the highest cloud layers. Tristan Morgan had pinpointed the signals as deriving from one of the Von Neumanns now ahead of the Leda. As the submersible closed on the beetle-backed collection vehicle, Wilsa could see the source of the problem. Intense heat—presumably a lightning bolt—had fused and deformed one set of intake Venturis and storage tanks. The Von Neumann rode lopsided, a pale exhaust of escaping hydrogen hissing out of its base.
Wilsa steered the Leda to within a hundred meters and matched their paths. The Von Neumann was descending at a rate of about a kilometer a minute. She focused the imaging systems on the crippled side.
"Pretty bad." Tristan Morgan was inspecting the damage. "In fact, worse than I thought. With that loss of hydrogen, we could fly as far as the upper edge of the atmosphere, replacing as we went. But it would never make escape velocity."
"What can we do?"
"Not a thing. Unless it reaches orbit, there's no way to perform repairs. We have to write this one off."
Wilsa stared out at the doomed machine. Suddenly it seemed to be alive and suffering, despite Tristan's assurance that it was of very restricted function and intelligence. "You mean we just leave it here crippled, and it floats around forever?"
"That won't happen. It will keep sinking down to greater pressures and temperatures. Look at the depth gauge. You're at one-three-two-seven now. By the time the Von Neumann reaches six or seven thousand kilometers, the temperature will be up over two thousand Celsius. It will melt and disperse, and its elements will go back into the planetary pool."
His voice was casual, but Wilsa could not help contemplating a more personal vision. How did he know that the temperature would keep rising, and know that the Von Neumann had no feelings? Suppose that it was self-aware. And suppose that it was doomed to remain functioning and to drop forever, through increasingly dense layers.
She told herself that it could not be forever. Seventeen thousand kilometers down, according to Tristan Morgan, Jupiter had pressures of three million Earth atmospheres, and hydrogen changed from a gaseous to a metallic form. No matter what happened at higher altitudes, the Von Neumann could not survive that transition.
Music began again inside Wilsa's head, grave and cadenced. A C-minor dirge. Pavane for a dead Von Neumann. It built for a full ten minutes, until it was interrupted by Tristan Morgan's thin, far-off
The other two were quietly harvesting. Monstrous intake venturis, hundreds of meters across, sucked Jupiter's atmosphere into their broad, beetle-shaped interiors. Hydrogen was vented at the rear, except for the tiny amount needed to supply the Moby fusion drive. Traces of sulfur, nitrogen, phosphorus, and metals were separated and hoarded, awaiting the time when enough of those raw materials had been collected. Then the Von Neumann would create an exact copy of itself, and release it.
Helium, a quarter of the mass of the Jovian atmosphere, remained to be processed. Most of it, like the dross of a mining operation, was of no interest. The precious nugget was the isotope helium-3, ten thousand times as rare as helium-4. The Von Neumanns painstakingly separated the two components, vented the common isotope and stored the lighter molecules in liquid form. When a hundred tons had been collected, the storage tanks would be full and the Von Neumann ready to begin its long ascent to planetary escape.
But that triumphant exit was not the event that Wilsa had come to witness. Anomalous signals had been arriving at Hebe Station, orbiting Jupiter half a million kilometers above the highest cloud layers. Tristan Morgan had pinpointed the signals as deriving from one of the Von Neumanns now ahead of the Leda. As the submersible closed on the beetle-backed collection vehicle, Wilsa could see the source of the problem. Intense heat—presumably a lightning bolt—had fused and deformed one set of intake Venturis and storage tanks. The Von Neumann rode lopsided, a pale exhaust of escaping hydrogen hissing out of its base.
Wilsa steered the Leda to within a hundred meters and matched their paths. The Von Neumann was descending at a rate of about a kilometer a minute. She focused the imaging systems on the crippled side.
"Pretty bad." Tristan Morgan was inspecting the damage. "In fact, worse than I thought. With that loss of hydrogen, we could fly as far as the upper edge of the atmosphere, replacing as we went. But it would never make escape velocity."
"What can we do?"
"Not a thing. Unless it reaches orbit, there's no way to perform repairs. We have to write this one off."
Wilsa stared out at the doomed machine. Suddenly it seemed to be alive and suffering, despite Tristan's assurance that it was of very restricted function and intelligence. "You mean we just leave it here crippled, and it floats around forever?"
"That won't happen. It will keep sinking down to greater pressures and temperatures. Look at the depth gauge. You're at one-three-two-seven now. By the time the Von Neumann reaches six or seven thousand kilometers, the temperature will be up over two thousand Celsius. It will melt and disperse, and its elements will go back into the planetary pool."
His voice was casual, but Wilsa could not help contemplating a more personal vision. How did he know that the temperature would keep rising, and know that the Von Neumann had no feelings? Suppose that it was self-aware. And suppose that it was doomed to remain functioning and to drop forever, through increasingly dense layers.
She told herself that it could not be forever. Seventeen thousand kilometers down, according to Tristan Morgan, Jupiter had pressures of three million Earth atmospheres, and hydrogen changed from a gaseous to a metallic form. No matter what happened at higher altitudes, the Von Neumann could not survive that transition.
Music began again inside Wilsa's head, grave and cadenced. A C-minor dirge. Pavane for a dead Von Neumann. It built for a full ten minutes, until it was interrupted by Tristan Morgan's thin, far-off
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