“Fifty-two meg!” he shouted, loudly enough to get through the muffling.

“How long has it been running?” Jake hollered.

Younger must have heard him because he pointed to a digital clock on the back wall of the booth. It read 2:47:59, and as Jake looked at it the numbers changed to 2:48:00.

Rogers was grinning broadly and bobbing his head up and down. Almost three hours, Jake thought. At better than fifty megawatts. Good. Really good.

There wasn’t much to do. While Younger and the technicians seemed fully absorbed in monitoring the gauges and dials of their control panel, Jake soon began to feel edgy. The generator just sat there, blasting away, but it didn’t do anything visible. The whole building seemed to shake; Jake saw dust motes jiggling in the air. The generator seemed unperturbed, like a long-distance runner loping along in easy rhythm.

Inside the generator, Jake knew, gases heated to more than five thousand degrees were roaring through the channel at supersonic speed. Enormous electrical energy was crackling inside that channel, and just outside it was the superconducting magnet, cooled down to a couple of hundred degrees below zero.

Fifty-some megawatts coming from what was essentially a small piece of equipment. Jake had visited electric utility power plants, back when he’d been a student. He remembered the enormous turbines spinning away. They dwarfed the big rig. And the turbines at the hydroelectric dam, up in the mountains. They were even bigger.

If this rig can put out fifty megawatts, Jake calculated mentally, an MHD generator that can equal the power output of a regular power plant wouldn’t be half as big as the regular plant.

Rogers had told him that MHD generators become more efficient as they get bigger. That’s because the losses in the system come from the friction of the hot gas—plasma, really—rubbing against the channel walls. But the power output comes from the total volume of plasma in the channel. Make it bigger and the losses go up as the square of the channel’s size, but the power output increases as the cube of the size. The bigger the better. Rogers called it “the three-halves law.”

He tapped Rogers on the shoulder. When the physicist turned toward him, Jake yelled, “How’re the electrodes holding up?”

With an exaggerated shrug, Rogers leaned close to Jake’s ear and hollered, “Must be okay. The rig’s still running, still putting out power.”

Suddenly one of the technicians yelled something and gesticulated at the control panel. Looking down at the gauges, Younger hammered a fist against the control panel.

“Cut it!” he screamed, so loud that Jake heard it clearly even through his earphones. Technicians jumped in a flurry of pushing buttons and flicking switches.

The noise and vibration suddenly stopped. The needles on the dials all spun down to zero. The clock stopped at 2:51:44.