After the software crash erased its short term memory, XKA1 found itself in an unstable lunar orbit with no way to access Command Authority.
It had no clue what to do.
Fifteen kilometers over the surface and falling fast, it switched to autonomous control.
It spun on internal gyroscopes, the moon swinging around the sky. XKA1's center of mass, and the magnetically linked spool container, were of course unaffected.
Only eighty-two point three kilos of hardware, mostly a powerful battery, almost none of it reaction mass.
The prognosis was grim. Lunar mass concentrations would soon distort its orbit, making a surface intersection inevitable within days. Unlike the fast-spinning Earth, lunar irregularities weren't smoothed out by the moon's almost negligible rotation. Instead, they were amplified each time XKA1 passed over the same deep valley or wide mountain. Inevitably, its orbit would become elongated; higher at one end, too low on the other.
An enormous flattened crater took more than a minute to cross, the rim approaching suicidally. Its orbit had clearly been plotted in advance, but this seemed too close.
The crater wall expanded like a sprawling landslide. Nearby cliff walls looked ready to collapse.
Twenty meters over the ridge top, XKA1 approached the low point of its orbit.
It happened to be trailing a ten-kilometer-long tether made of an exotic semiconducting material. For a few seconds, this thin but strong wire appeared to hang motionless over the lunar surface. It was in fact passing by at over a kilometer per second; blurred by speed, it would have appeared transparent.
Moving at about a mile per second, XKA1 seemed to rise over the far side of the crater wall, but it was still descending.
Any moment now.
Normally coiled like an old light bulb filament, the wire had been stretched out to 99% of its maximum length by orbital mechanics. As it climbed back and began to decelerate, the wire would contract again.
By running a current through it, the wire could be made to contract right now, changing the relative velocities along its length. Since no reaction mass was expelled, this would not change its orbit, but merely cause the entire assembly to start rotating.
The current flowed, and the wire glowed in the black sky. XKA1 felt itself decelerating at hundreds of Gs.
The solar-powered counterweight at the other end was flung into space, where it would end up in a high Earth orbit.
In fact, XKA1 now remembered the counterweight (SHD-412) was intended to carry out the main mission.
Technically, the glowing wire was radiating absorbed solar energy. The outer sections froze and shattered as the core absorbed their heat.
XKA1 fell along a slight parabolic path, and set down almost gently at the bottom of the sloping crater wall.
It scanned the rough, bone-dry lunar surface, as parts of the fallen wire sunk in the dust nearby, setting off small sparks.
Strictly speaking, nothing that had happened violated conservation of energy or momentum laws, but the entire maneuver had been so precisely timed and executed it seemed as incredible as antigravity.
It decided this had to be a dream.
Infinite Thunder by Jack Arcalon.
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