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Dec 17, 2012 02:37
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| # ¿ Apr 24, 2024 07:54 |
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Improper Time (997) They were humanity’s first starships. Of course they had laser cannons. Pointing out that they’d only ever be used to ionize dust and slow each other down was just being a spoilsport. Strung on a line 30 light years long, the First 49 screamed through space at better than nine tenths the speed of light. Lasers ionized dust and neutral atoms, magnetic wedges diverted the debris. Slowest in front, fastest at the back, differences in launch time whittled away by velocity differentials, they were a slowly compressing Fibonacci thunderbolt 230 light years from home. Last was All Uphill From Here, the fastest macroscopic object in existence, hurtling through the dark at .97c. Raahi Moreno, her only crew. His ship would be last. Raahi would be First. 166 light years ahead, HIP 66639b and its nitrogen/oxygen atmosphere. Raahi would die before he got there. # It started two years ago. The lead unmanned probe, Ellie, calmly exited her expected velocity envelope over a week and a half and continued to slow. No rogue snowflake had bombarded her. She reported no measured change in incident radiation, no change in radiating surface geometry. Ambient gas density was lower than average. Everything just as expected, except for a slowly building, featherweight acceleration in exactly the wrong direction. “Well, not exactly the wrong direction.” Uphill said. “What’s that?” said Raahi, as he blinked up TacCom. “There’s a slight transverse component to the acceleration too, see?” The relevant figures swam in Raahi’s vision. The new vector, hugged by its confidence interval, stuck out at a 110 degree azimuth angle from ADN: Arbitrarily Designated North. Raahi smiled faintly and blinked TacCom away. He floated toward the front of the bridge. There was a red smudge he’d put above the circular screen there as soon as the acceleration started. He’d always know which way was up. He nudged the screen with his fingers and slowly spun himself upside down. In zero g this meant nothing. But now he was aligned with the smudge. So this bullshit, he thought, is pushing Ellie mostly straight at me, and a little… he held his left arm a little below vertical, that way. “I could adjust the vectors so you were always aligned to them you know,” Uphill said. “Sure. But this way I feel it. Besides, wouldn’t want to tax you.” “Very droll.” “So. This rules out thermal recoil or a leak: Ellie's spinning. She can’t be the source of a consistent off axis force,” said Raahi. “Yes. It also disqualifies magnetic misalignment of her wedge, or malfunction of her lasing arrays.” “Got any new ideas?” “Several million. The most probable, though, is something quite troubling.” # Confirmation waited another four weeks. Galileo, the second probe, was also slowing. The force it experienced was slightly different. “Got it. Both decelerate proportional to their mass and the inverse square of velocity. It’s Chandraskher friction, I’m almost sure,” Uphill said. Gravitational drag. Something was bumming a lot of little gravity assists off the probes. You didn't think of Luna slowing down after Apollo 13 got a slingshot back home, but it did. Shoot enough faulty service modules at it, let them all slingshot, and you’d notice eventually. “poo poo. So we’ll hit it too.” “Yes. In about seven years.” “And it’s what, dark matter?” “By definition. Interacts gravitationally, no interaction electromagnetically. Diffuse, like a gas. A slow moving cloud. It’s moving across our path. That’s where the transverse force comes from. Calculated density implies some interesting properties. We’ve made quite a discovery.” “And Sol will be loving thrilled in 230 years. How much will it slow us?” “That depends.” “No poo poo. You already ran the numbers. Tell me.” “We’ll lose perhaps four percent of our velocity.” The silence stretched. # At .97c, the journey had taken 236 years as far as Sol was concerned. But on Uphill, only 60 years had passed. Einstein’s gift, via Lorentz. A four percent drop in velocity over the remaining 166 light years would stretch 45 years in to 60. He could survive the extra time easily. His food supply could not. A star 396 light years away didn't come with slowdown infrastructure. If you wanted to go somewhere and stop you had to bring that delta-vee with you. Raahi hit upon a minor innovation in sending some of it ahead of him – as a string of probes that would each contribute to a growing solar powered deceleration laser array; the first probe helping slow the second, their combined array helping slow the third, and so on. Uphill carried plenty of array mass herself, to help a hypothetical next ship stop. The trick cut deceleration mass by a quarter, but it was a razor margin. Uphill couldn't afford to mass more than she did. The onboard ecology was efficient but not closed. The math was inarguable. # They argued. For two years they calmly discussed options while the cloud engulfed the First 18. “It’ll bleed the most stubborn velocity from us, that can’t be all bad.” “The probes ahead can afford to use a little reaction mass now, if it’s called for.” Uphill mapped the variations in the density profile as her sisters slowed. They had hit some of the thickest stuff first, that much was clear. Some lasers could reasonably be powered off, antimatter fuel put to better use. With 48 ships ahead it was likely that favorable wake conditions could be engineered. The instructions would take years to reach Ellie, there was no rush. # A year later they had a plan. “Let’s send it,” Raahi said. “We probably won’t make it,” said Uphill. “You’ll make it just fine you drat computer.” “You know what I mean.” “But you don’t!” Raahi said, laughing. “You’re just a Chinese Room! No concept of meaning or self at all.” “You’re right. There, are you happy now?” Uphill's indignation was inflected perfectly. “Yeah. Punch it,” Raahi said. He spun himself to orient with the red mark and waited.
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Dec 22, 2012 20:56
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