The war had almost drained our combined resources of energy: even though we were closer to the Sun, the solar power simply couldn't be collected without materials to build solar collectors. With every last scrap of metal engaged in the war effort, or otherwise up in space somewhere, it was impossible to get anything done on the surface.
The black hole changed that. It was spotted a few years ago, slowly drifting across the plane of the solar system; it was only seen at all because it crossed the path of Venus, and the planet changed shape for a few hours. In their haste to focus attacks on Earth, the invaders missed the shift in the appearance of Venus, and we got there first.
With so much detritus up in high orbit, and so many people based on the Atlantic tower platform, it didn't take long for an old warship module to be staffed out with a skeleton crew, and pushed off in the direction of the black hole. The crew ended up being us, the second-shift engineering staff of the Nagios. The warship was a decrepit 301 with no gun batteries to speak of, but it did have one thing in its favour: the experimental coil we were dispatched to try out.
I took on the role of pilot, simply because I'd done some strong gravity training back at the Academy. Jackson was our chief engineer, and Fuller had the day off, so he got roped in too. Three of us, and a crazy theory, to try to change the war.
The theory was simple, when compared to others in the field of quantum relativity. A black hole has a gravitational field, which radiates out in lines, much like a magnetic field. Black holes also spin, which mean the lines of gravitational field are moving all the time. Vassilev theorised that a superconducting coil placed around the hole, near the Schwarzschild radius, would cut through the field lines and generate an electrogravitic field in the coil. It was impossible to even attempt a confirmation of the theory at the time, since there were no black holes, and no superconductive material to spare.
With the war, the situation was different. Even our old and broken 301 had a few miles of ceramic-wire running to the weapons systems, which could carry incredible amounts of charge. Measurements of the black hole mass put it at around one thousandth of the sun's mass, which left the hole's Schwarzschild radius at 30 metres: there would be plenty of wire for the coil. Getting the coil into place, that was my job as ship's pilot.
As we came up towards Venus, I called down from the pilot's chair, into the pit. "Jackson, get the ceramic down the back; let's give this hole a good run."
It's not easy to steer a course around any strong gravity source, as we'd all found out when the Weichinger carrier came too close to an enemy neutron barrage: it had been torn clean in half by the tidal forces. A black hole was more predictable, but much scarier at the same time. At least with a neutron barrage, it was possible to come out the other side.
I'd done this kind of thing in simulators before, with a whole term of spaceflight at the Academy focussed on getting around when strong gravity was in the area. One thing you never expect is that the outside universe gets smaller. We were close enough to the hole now, that I could barely see the Earth as a small point in what seemed like the far distance, and stars were beginning to show trails as we moved.
The 301 wasn't a highly manouverable warship at the height of its career, over thirty years ago: it was often referred to as the Bucket Class by the current cadets of the Academy. Moving around near a black hole was another adventure, with the constant tug to the left as I wound the ship anti-clockwise around the point.
"For what it's worth," Fuller called up from the cargo hold, "we're nearly out of gas for the manouvering thrusters."
"We're low on everything," I said in reply. "No worries, I'm nearly done here."
The hole was at least uniform, so it was pretty short work to get the coil deployed in four loops around its equator. Jackson came up the ladder to the viewscreen, while Fuller stayed down in the hold to get the coil's ends into a power meter. Based on the shape of the black hole, and how stationary I could keep the ship against it, we were looking at maybe three hundred gigawatts: not bad for a proof of concept.
Fuller fired up the meter, and there was silence for a few seconds. "Er. Jackson, Irvine? You'll want to see this."
"I'm holding the ship straight," I answered. "Do I need to come down there to see what the meter says?"
"Well, it's off the scale, and the scale goes up to a terawatt."
Jackson looked down into the pit with a slightly incredulous look. "Nah, that can't be right. Lemme get down there, I'll check the wire."
Even superconducting ceramic heats up when enough charge flows through it. Jackson put his hand against the coil, and drew it back quickly. "That's, er, warm. You might want to get someone else out here, Irvine; we might have more than we bargained for here."
That's how it started, of course. Eventually, we had wires criss-crossing that hole and pulling out around ten terawatts: more than enough to feed a new generation of powered weapons. Thanks to the hole, we fought the invaders off, and Earth managed to claw its way out into the light.
A few years after the war ended, Stan Vassilev was awarded the Peace Prize, which he found suitably ironic. It was his opinion that we'd bled our new power source dry, and it would soon evaporate; a month later, the hole vanished, and the 10TW of power went with it.
I still don't know where it came from, and why it showed up to help Earth when it did. Religion's outlawed by the military, so I can't be a religious man, but I do wonder sometimes. Even as an engineer, it strikes me as odd that Earth was dealt such a massive stroke of luck: someone out there's looking after our interests.