Poseidon's Wake

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123

Fifty kilometres from the seas of Poseidon.

Forty-five.

Vasin deployed the undercarriage. They had descended on one side of the wheel, but now she vectored them sideways until they were almost hovering over the tread itself. What had been taxing now became doubly difficult because she did not want the Chibesa exhaust coming anywhere near the fabric of the wheel, for fear that it would cause an explosion or be interpreted as a hostile act.

These fears struck Goma as perfectly reasonable.

The thrust had to be feathered now, vectored out at sharp angles, and that in turn meant an increased load on the engine just to hover. Mposi by then had gone berserk with its own anxieties. Vasin cancelled all the alarms and got a small round of applause from her crew.

‘Probably for the best. I don’t think I want a second’s warning when things go completely wrong.’

‘You’re doing wonderfully, Gandhari,’ Goma said.

‘You sound like your uncle.’

Goma did not know what to say to that. But she was not displeased by it.

Now came the hard part, as if it had been plain sailing until now. They had to land, or at least hold station, while the rescue party was unloaded.

It would have been easy enough on the wheel’s summit, where the great curve approximated a level surface. Here, though, they were not even halfway to the top. At forty kilometres above the sea, the inclined tread of the wheel was thirty degrees away from a sheer surface. Only the grooves offered any possibility of a secure footing.

Vasin brought them in close, veered out, came in closer again — all the while making tiny adjustments to the landing gear. ‘No one move around much,’ she said. ‘And if you want to try not breathing for a bit, that would help.’

The moment of landing, when it came, was barely a kiss of contact. Mposi swayed, its gear taking up the load as the engine slowly throttled down to zero thrust. Through one set of windows, Goma saw only the near face of the wheel, almost close enough to touch if the window’s glass had not been in her way. She wondered how they had managed to land at all.

‘Unload as quickly as you can,’ Vasin said, not stirring from her command seat. ‘Use the secondary lock, not the primary, and take care on your way out. Watch when you bring out the winch gear — it’s heavy, and our balance may shift.’

They had begun putting on their spacesuits before the final approach to the wheel, so now there were only final preparations to be made. Eunice had left her suit behind on Travertine, so they were all using the same standard model carried aboard Mposi. She was less than happy about that, scowling at the life-support controls built into her sleeve and shaking her head in disgust.

‘What is this horse piss? You’re supposed to get better at making things, not worse.’

‘Shut up and put up with it, the way we have to put up with you,’ Ru said.

They locked on their helmets, checked comms and began unloading the equipment.

It was only when Goma was outside that she could see how skilfully Vasin had put down the lander. It had been a tricky bit of work, worthy of grudging admiration even from Eunice. Two of the four landing legs were planted into the groove, compressed to their minimum extension. The other two, stretched out as far as they would go, were braced against the steep side of the wheel between the groove they were in and the next one down. The landing feet on that side were angled to their limit, relying on friction to support them to the lander.

It looked precarious, which it was. Eunice said that she had seen some nastier landing configurations, but not since the days of chemical rockets. Vasin was even applying a constant torque of steering thrust from one of the lander’s auxillary motors, a cruciform-shaped module high up the side of the hull, near the out-jutting control bubble. Without that corrective thrust, there would be little to stop the lander toppling away from the vertical.

‘But I can’t keep bleeding that jet,’ Vasin said. ‘It’s not meant for sustained use, and it’s not fed from the Chibesa core. Once that tank’s empty, we’re in trouble. I’ll need to lift as soon as you’re independent.’

It took thirty minutes to get all the emergency supplies unloaded and organised — during which time Kanu’s party rose another five hundred metres. Goma was supremely conscious that each second counted against Kanu. Equally distressing was the fear that they would make some miscalculation or omission now, and really damn their hopes.

The immediate task was to set up the tether and the grapple. The grapple was a thousand kilograms of heavy-duty engineering designed to bear the load of a spacecraft under adverse thrust. It would certainly not fail on them, which was one consolation, but it took two of them to move it, and even in its retracted configuration it only just squeezed through the secondary lock. It looked like a mechanical starfish, two metres across with five independent arms, each of which ended in a complex multifunctional gripping appendage. They wedged the grapple into the back of the groove, cleared to a safe distance, then ordered it to lock itself into place. The arms pushed out with explosive speed, the tips adapting to the sensed surface to provide the maximum locking force. Since the inner walls of the groove were smooth, there was nothing for the grapple to hook on to. But it was also designed to couple with the smooth hulls of other spacecraft, using high-friction pads. Its appendages angled to bring their pads into optimum contact. They slipped a little initially, then held. The three humans approached the grapple again and hooked on the tether. Using the power winch, they tested the grapple up to five thousand and sixty newtons of instantaneous force, at which point it slipped and then regripped. Five tonnes — not much.

They would never strain it that severely, though, because the tether was going to run over the lip of the groove, which would function as a bearing surface. From Mposi’s repair inventory they found a piece of spare hull cladding which had approximately the right profile to slip under the tether at that point of contact. They fixed it into place with vacuum epoxy, trusting that the bond would hold against the alien material of the wheel, and that the tether would not cut through it.

They buckled what they could onto the utility belts of their suits, but the emergency oxygen and power supplies were too bulky for that. These items were packed into a zip-up bag which they would lower down ahead of them, strung out like a plumb-bob on a few metres of standard safety line. They used the same line to tie themselves together, again with a safety margin of a few metres.

Eunice would lead, Goma second, Ru third. Ru was the only one coupled to the tether itself and she had direct control of the power winch, which was connected to the front of her belt by a sturdy clasp. The winch did not look like much to Goma, just a squat yellow cylinder with some hazard stripes and a few simple operating controls chunky enough to be worked with spacesuit gloves. It was hard to believe that most of the fifty kilometres of the tether were still spooled up in the winch’s casing. But then the tether itself was almost invisibly fine, and Vasin had warned them that it could easily slice open their suits if they touched it under tension.

Or worse.

Still, doing it this way rather than spooling out from the grapple at least meant there was no moving contact between the tether and the corner piece. Eunice would be their lookout as they approached and traversed each successive groove on their way down. And to stand a chance of helping the others, they would need to be moving quickly.

Eunice was the first over the lip, with the supply bag dangling under her. She braced her legs against the nearly sheer side and signalled for Goma to join her. Ru spooled out the line, no more than tens of centimetres at a time, until all three of them were over the lip and their weight was borne by the tether. It was easy for Goma — she was coupled to Ru by a stretch of line obviously thick enough to bear her weight. But Ru was barely able to see the tether.

‘I’m near the top of the next groove down,’ Eunice said. ‘Start lowering us. I’ll kick off and rejoin the surface under the groove. You’ll have to do the same. Once we get into a rhythm, we should be able to make good speed.’

It took them a while to get the rhythm of it. They were strung out far enough that Eunice and Ru were both passing grooves while Goma was descending the flat section between them. If they did not time their kicks correctly, there was a risk of Goma being torn from the wall just in time to swing back into the mouth of a groove. At low speeds, little harm could come to her. But to be of use to Kanu’s party, they would need to reach them in under ten hours, and that meant an average descent speed of five kilometres an hour. That was fine in spurts, not even a brisk stroll, but they could not allow themselves to fall behind. Every error counted, and if they had to go faster to make up time, any resulting accident could have serious consequences.

Thirty or forty minutes into the descent, though, they settled into a pattern. The tether was reeling out smoothly, the grapple holding. Goma stopped concentrating and just allowed her muscles to find the right pace, trusting in the women above and below her. The grooves passed one after another, punctuated by the icily smooth and pristine material between then. The angle of the tread was steepening towards vertical with every metre they descended, but it would be a long while before that became obvious to Goma’s senses. The wheel’s rotation brought Kanu’s party higher with each second, but that same rotation was also working to push Goma’s team higher as well. They could not afford to stop until they had closed the gap to Kanu, and to do so in a useful time they needed to outpace the wheel’s counter-rotation.