Free Tides of Light by Gregory Benford

saw a pattern in the snaking tunnels. The station’s many corridors and shafts did not center on the disk
     plain. Instead, they necked toward a point high above that, in the northern end of the tower.
    He sent orders to the teams to vector that way. Then he turned his attention back to Toby’s scanner feed. It provided the
     most complete views, which the
Argo’
s systems immediately integrated into the station 3D map.
    Toby was plunging down a hexagonal shaft. Besen flew ahead of him. They both moved adroitly in the zero gravity, maneuvering
     with experience born of daily drill on the
Argo
.
    Ahead was another squad, which had reached the nexus first. They were attaching inputs to a huge blank cube.
    —Mainmind,—came a comm signal.
    “Looks like.”
    —Wiring so can blow it, Cap’n.—
    “Yeasay.”
    Toby landed on the bulwark cube, boots thumping. Killeen watched leads attached, holes bored with quick darting laser punches.
    Mechs appeared nearby, obvious and awkward. They died in bursts of ruby phosphorescence. Killeen frowned. The mechs seemed
     unusually slow and stupid. Had they simply gotten unused to human combatants?
    A motion caught his eye. Indices showed a higher radia tion count….
even a slow defense can draw a swift, unthinking attacker into a trap
…
    “Exit now!” he sent to Toby. Relayed, the order provoked a hurried finish to the mining.
    “Leave the extra charges!” Killeen shouted.
    —But they’re primed,—Toby sent.—I gotta—
    “Even better. Go!”
    Something appeared at the far end of the shaft. It was big and moved quickly but Killeen’s warning had gotten the squads clear.
     The approaching shape did not have a good angle to shoot.
    The two squads raced away into an exit tunnel.
    “Blow those extra charges,” Killeen ordered.
    —But they’re just floating,—Toby answered.—Won’t hurt the mainmind.—
    “Do it!”
    The answering percussive punch came rattling through the electromagnetic spectrum. A strange, descending wail cut across the
     noise. Killeen frowned. The dwindling shriek was like the cry of a dying animal. Mechs never gave such a sound.
    The big thing must have been caught as it passed the mainmind. Killeen guessed that it was the controlling influence here.
     Only luck had let the squads escape. But there were still plenty of dangers.
    Toby’s relayed images showed them racing into a tunnel that led straight away from the mainmind.
    “No,” Killeen sent. “Take one that has turns. They’ll haveambushes on the fast routes. And the turns will block the blast.”
    In eerie stretched silence he watched the seconds tick on. The screen darted and swerved and lurched as Toby made maximum
     speed in the zero gravity. The boy could windmill his arms and get his feet into position for a land-and-repel with perfect
     timing. The screen whirled as Toby tumbled in the closed, narrow spaces. This swept twirling spotlights over the mad rush
     of mechtech that came streaming up from darkness and vanished just as quickly.
    At last they came to a long tunnel that showed starlight in a distant circle. Toby ram-accelerated toward it. The screen suddenly
     jerked.
    “The mainmind’s dead,” Killeen said. “That was an electromag-tag burst from it as it blew.”
    —Great!—Besen burst in.
    Killeen tensed. Toby tumbled soundlessly in the yawning blackness. Ghostly arms reached out nearby, blue and flickering, searching
     for something to scorch. Further, Killeen knew, there were other presences called Inductances and Resistors and Capacities
     which played mysterious but perhaps fatal roles in these electrodynamic corridors. He had learned to use them, but their deep
     essences eluded the practical programs he had studied.
    Toby veered. Three squads followed him in a quick dash for the opening.
    Then the screen showed only swirling stars and the harsh yellow-white of the disk plain.
    Toby spun and looked behind. From the tower opening came a crumpled form in a shiny