Von Neumann’s War

There were two laser projectors on Monte Sano Mountain, one right by the observatory and another by the Forestry Department lookout tower. Both were powered by nine very large General Electric diesel generators. The combined output of the generators was over seventy megawatts per hour and the vast majority of it was pumped through a massive array of liquid cooled laser diodes.

The laser systems themselves were mostly large laser diode arrays made of semiconductor material mixtures of indium gallium arsenide and phosphate. The individual diode laser measured only a millimeter thick, a few tens of millimeters long, and a few microns wide. Millions of the tiny devices were stacked side by side to create a massive laser array with an optical output in the megawatts of photon energy. The photons were of a wavelength of about 1.3 microns and were therefore infrared and invisible to the naked eye.

Laser power is limited by atmosphere. While there were various ways of reducing the effect, the Redstone group hadn’t had the time to try for finesse. Thus it was a matter of letting the probes get close before the projectors opened fire. The lasers went off when the probes were less than five miles away.

The lasers began to “paint” the sky, tracking back and forth across the entire zone that the probes occupied, moving much faster than the eye could follow. This created “lines” of fire that dithered across the front of the cloud, zooming up and down and up and down across the entire front. The pointing and tracking system for the array steering maintained a centroid lock on the cloud and randomly dithered within the bounds of the cloud. Pinpoint shots could be made to within accuracies of a few centimeters at that range but the beam was a half meter wide by then due to diffraction and there were plenty of targets to shoot at anyway. So accuracy was not a problem.

The powerful lasers tracked back and forth, pumping megawatts of coherent light into the mass of probes.

And the entire front of the cloud of probes began to… fog.

“What the hell is that?” Shane asked. “It looks like a smoke screen. Are they doing that to cut down on the lasers?”

“No, but it’s having that effect,” Roger replied. “That, my friend, is gaseous metal. The lasers are burning the probes apart, but they’re releasing clouds of metal gas in the process. That’s going to be a very unhealthy place to be after this is all done.”

He zoomed in on the cloud and managed to catch a view of a bot just as the laser, which was quite invisible to the eye, cut across it. The laser caught the bot on the edge of one “wing” and sliced upwards. The beam wasn’t powerful enough to cut all the way through but the effect was to cause the bot to begin spiraling downward. Another bot caught it after it had fallen no more than a hundred feet, and along with some others began tearing it apart. But even as Roger watched, the remorseless laser plowed through that group, cutting the four clustered bots apart and causing the whole group to begin spiraling towards the ground.

“It’s slowin’ ’em down, though,” Alan said, looking at Plasma Two, which was carrying lidar data. “Damn if it isn’t slowing them down.”

“But they’re spreading out, too,” Roger pointed out, zooming back the lidar data. The cloud was spreading upward and to the north and south. He wasn’t sure if it was thought out or simply a result of crowding. It was apparent, though, on the remote vids that the laser operators had noticed the spread and had spread their own beams as well. However…

“They’re getting through, now,” Shane said, shaking his head. “The lasers can’t cover that much sky and still keep them back.”

Remorselessly, the mindless bots were advancing through the laser fire. They could barely make headway, but they were forcing their way forward and fanning out the sides and over the defenses. The latter two were the most important and dangerous, through. The bots to the side and top were able to use those between them and the laser projectors as screens and were continuing on towards Huntsville.

The video from Monte Sano Mountain had gotten… dark. The projectors now had probes on every side and had spread their fire to deal with it. That meant less fire per square meter but despite that there was only so close the probes could get. As they closed, the space between the laser “lines” became smaller and smaller. More of the power was being pushed into a smaller and smaller space, creating a dome of probes trying, now coherently, to get at the projectors and the projectors tearing them apart.