After a fine meal of tacos, Milo was unsure what to do. Rather than keep playing without Belinda, he paid for a room at the inn next to where he'd just eaten and logged out of the game. He sent a message to Butch about visiting Belinda the next day and then put some time into solving a puzzle that had been bothering him.
His small tunnel scouts had been doing their job, mapping out the dimensions of the obstruction under Section E. From just the preliminary data; it was quite large. What he had thought was a thick plate of metal was actually a rectangular solid. So far, the tunnelers had found a solid surface on all four sides going down 150 feet. The only discontinuity in those surfaces was the support pillars of Section E at each corner and a horizontal structure that jutted out from one side. This structure was made of normal building materials and thirty feet on a side. A tunneler had followed and mapped it for a hundred feet before returning to mapping the main surface.
Milo was more curious than ever. It couldn't be solid. There was no reason to make a solid block of ultra-hard material. So what was in it? And if it was some sort of storage facility, bunker, or manufacturing facility, then the extension was certainly a supply line. Most probably a maglev supply train or similar transport system. Building such a facility under a Habitat wasn't a coincidence. The alignment to Section E was too perfect. He had some other theories, but first, he needed to test the material the walls were constructed of and investigate the extension. He sent commands to all the tunnelers, large and small, to clear certain areas. And then he went to get dressed for exploring.
He'd been wearing his graphene exo-suit for days at a time, correcting flaws and learning how to move in something that enhanced his strength. The results had pleased him, and he'd worked out equipment to use with the suit. A solid helmet with an opaque smoked-glass faceplate replaced the soft mesh hood and face covering. It locked to the neckpiece of his suit, giving him full protection and a heads-up display from his systems. He'd stolen many of the ideas mentioned in the original Starship Troopers book by Robert Heinlein to control his sensors and work with his systems. Tongue, jaw, and neck combinations acted like a keyboard. A detachable backpack contained air and water for extended use in areas where the air might be bad.
He had rebuilt his claws after testing and much research into materials. Additional 'exo-muscle' in hands, feet, and tail made up for his lack of mass. The claw tips were tungsten reinforced with lonsdaleite, a hex-based carbon form 58% stronger than diamond. It wasn't easy to work with, and the replicators had gone through several tries before Milo was happy with the outcome. Alta-Viator wasn't around in this world to give him sharp claws, so Milo made his own.
Down in the sub-basement where the large tunnel started, he had a small cargo mover ready. The vehicle was meant for moving in service tunnels and was only 30" wide. Milo loaded tools and scanners and drove it into the tunnels that slowly sloped down to where the excavators had hit the blockage. After an hour, he emerged into a modest cave dug out by the machines. The air was bad here, filled with exhaust fumes and rock dust. He was glad to have a full air system in the suit. Examining the material, he saw a dull grey metal with low luster. An attempt to scratch it with a diamond-tipped drill resulted in a broken drill bit. The claws of his suit couldn't touch it. They were made of the hardest material available to him, and they couldn't leave a mark on substance. He was getting more and more excited as he tried several other tests.
Forcing himself to breathe slower, he tested the material with X-Ray Fluorescence. The analyzer came up with no information other than 100% of the X-ray beam had failed to penetrate the material and excite its atoms. The angle didn't matter; all of the beam was dispersed. That was the final clue Milo needed. Someone had built a huge installation of some sort using Collapsium and hid it beneath a Habitat. The material was horrific to make. It was technically a metal, but the distance between individual nuclei was much shorter than normal, resulting in an ultra-dense material. A one-inch plate of collapsium was equivalent to ten feet of steel.
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There were many drawbacks to using it. First was the weight. At over a hundred times the density of normal steel, it was useless for anything other than a fixed location. Several corporations had dreamed of constructing tanks and missiles with the material, but it wasn't feasible. Why buy a collapsium armored tank that is too heavy for most roads and too slow to maneuver? Especially when it costs a thousand times more than a standard tank! Secondly, making collapsium took the use of a microscopic black hole to generate the stress needed to collapse the molecular structure. The black hole required the power of a fusion reactor. Each molecule of collapsium was created in a flux state and could be moved magnetically to where it bonded with a larger amount of the material. The building beneath Section E had taken years to construct fully, and Milo had zero doubts that it had contained a fusion reactor at some point. You simply couldn't transport the amount of collapsium in use here.
Which gave hints as to what this was.
The main uses of collapsium were for armored bunkers beneath government capitols and nerve centers. The largest in the world was part of NORAD, under Cheyenne Mountain, in Colorado, USA. The chance of using nuclear weapons was small, but governments and militaries prepared for extremes. The second major use was in fusion and fission reactors. Milo pondered his next moves. Someone had tried to hide something under the habitat. They might be upset at him finding out. Of course, that was only if he got caught. He briefly considered consulting Wally but decided that was a bad idea. It was too high a probability that Wally had something in his kernel that would be triggered by someone like Milo breaking into something important that was probably a government installation. Milo had no intention of leaving something like this alone. It was underneath his home, and he considered it fair game.
The next step was moving down through the narrower tunnels that led to the extension that jutted out from the collapsium walls. The small tunnelers had been busy making sure those tunnels would accommodate him. It took him two hours to carefully move down to that level, testing for possible cave-ins and leaving lines to help him climb back out quickly. The insanity of crawling through tight tunnels recently bored in the rock, hundreds of feet underground, didn't even occur to him. He was having too much fun.
Finally, he was standing on top of what was certainly a supply tunnel. The construction was standard reinforced concrete block, two feet thick. He was surprised to pick up no magnetic fields in operation nearby, which he would have if this were a maglev tunnel. Normally, getting inside such a tunnel would be difficult. Luckily, he had machinery for that. After another hour, his tunneler had made a two-foot diameter opening in the tunnel. Milo had been listening with audio sensors the whole time, picking up nothing and shutting the machine down every minute to hear. When it hit a hollow area, it pulled back, and Milo looked inside to find a dark tunnel extending in each direction. His first guess had been right; he saw the metal rings at two-foot intervals of a magnetic levitation transport system but completely unpowered. Someone had turned it off long ago, based on the dust on the rings. Milo waited a half hour and looked in each direction using a probe as far as he could. Nothing happened.
The next step was to send in a drone. The little robot fired up its three small propellers and moved into the tunnel, sending its visuals back to Milo. He sent it away from the installation first. It moved along steadily until it came to a blockage. Something had collapsed the tunnel in this direction. That was something to investigate later. He sent the drone in the other direction. The tunnel was the same and ended in a set of collapsium-coated doors sealing the tunnel. To the side was a small walkway that led to a more human-sized door. Milo was through the tunnel and jogging that way a moment later.