David Brin: Tank Farm Dynamo

“We believe,” Susan said, “that need will be greatest in the future. And we plan to be here, with the key to a treasure chest, when the time comes.”

“Dreams of glory.” Bahnz sneered. “I know all about them. Tell me about lunar mines and space colonies and other fairy tales, Dr. Sorbanes. And I’ll tell you about Low Earth Orbit, now filled with garbage and bombs and little cameras from half a hundred bickering, hungry little nuclear powers, all blaming each other for a world economy in a thirty-year skid!

“Have you any idea what would happen if even one of these arrogant little ‘spacefaring nations’ decided to ignite a small enhanced radiation device in that cloud of communications satellites overhead? You know as well as I how dependent we are on orbital datalinks. And you know the only way to defend those links is to put our satellites inside big Faraday cages.”

Bahnz struck the nearby aluminum wall. “ This is what your country needs, Dr. Sorbanes. This tank and others like it! And the propellants for upper-stage launches. And we need this station , for the momentum transfer you now almost give away to anyone who wants it!”

Susan was gearing up for a major rebuttal. I hurried to interrupt. “People, please! Let’s try to relax, if only for a little while. Colonel Bahnz, you seem to like Slingshot. That’s your third helping.”

Bahnz had plucked another bottle from a passing steward. “Why not?” He shrugged. “It costs a hundred bucks a pint on Earth. It’s damn fine beer.”

“Dr. Ishido is our brewmaster.”

Bahnz lifted the bottle and bowed his head in silent tribute to Don. An aficionado of beer need say no more; Ishido nodded at the colonel’s compliment.

“Director Rutter,” Bahnz said as he turned to me, “Dr. Woke and I will be leaving within two hours. I have held Pacifica to please you, but our business here is done. If you have anything more to say, you can speak through your Foundation’s Washington office.”

Bahnz was obviously the type that got straight to the point, especially when he had had a bit to drink. He showed no trace of that irreverent streak I had known in the officers and officials of the early nineties. Those fellows had been almost like co-conspirators, helping nurture the Farm along in a time of tight budgets and dubious senators.

“Two hours, Colonel? Yes. That should be enough time. Just remind Pacifica ’s crew to check their inertial tracking units before drop-off. There may be a few acceleration anomalies.”

Bahnz snorted. “So? You plan to fire up your famous aluminum engines to impress us? Big deal. Go ahead and use up your reserve water, Rutter. You’ve got enough oxidizer to run them for maybe two months; then you’ll start flinging mass away to keep orbit.”

Ishido started to rise. At a sharp look from me he subsided.

“Why, Colonel,” I said smoothly. “You sound down-right happy over our predicament.”

The crewcut officer slapped the oak table. “Damned straight! Let’s lay it out, Rutter. I think you’re a bunch of unpatriotic dreamers who’d do anything rather than serve your country. July’s court judgment was the last straw.

“We’re going to live up to the contract, all right. You’ll get your tanks, and enough water to keep from making martyrs of you. But you’ll start spending more mass to stay in orbit than you take in. You profits will disappear. Then see how fast your investors force you out as director!

“Pretty soon, Rutter, you’ll be buying Slingshot at a hundred clams a pint!” Bahnz emptied the squeeze bottle with a flourish.

I shrugged and turned back to my meal. The second worst thing you could do to a man like Bahnz was to ignore him. I intended to do the very worst thing within an hour and a half.

The face on the screen was flushed and angry. In the dimness of Arnold Deck Control Room, I could tell the man was upset.

“What the hell do you think you’re doing, Rutter?”

I had made Pacifica wait for fifteen minutes while the control crew made a show of looking for me, then appeared, to look back at Bahnz with an expression of beatific innocence.

“What seems to be the problem, Colonel?”

“You know damned well what the problem is!” the man shouted. “Colombo Station is under acceleration!”

“So? I told you over dinner to have your crew check their inertial units. You knew that meant we would be maneuvering.”

“But you’re thrusting at two microgees ! Your aluminum engines can’t push five thousand tons that hard!”

I shrugged.

“And anyway, we can’t find your thrust exhaust! We look for a rocket trail, and find nothing but a slight electron cloud spreading from A Deck!”

“Nu?” I shrugged again. “Colonel, you force me to conclude that we are not using our aluminum engines. It is curious, no?”

Bahnz looked as if he wanted some nails to chew—threepenny, at least. Behind him I could see the crew of Pacifica , crouched over their instruments in order to stay out of his way.

“Rutter, I don’t know what you’re up to, but we can see from here that your entire solar cell array has been turned sunward. You have no use for that kind of power! Are you going to tell me what’s going on? Or do I come back up there and make myself insufferable until you do?”

My respect for Bahnz rose two notches. He might be an SOB, but he knew how to get his way. “Oh, there won’t be any need for that.” I laughed.

“You see, Colonel, we need all that solar power to drive our new motor.”

“Motor? What motor?”

“The motor that’s enabling us to raise our orbit without spending a bit of mass—no oxygen, not even a shred of aluminum. It’s the motor that’s going to make it possible for us to pull a profit next year, Colonel, even under the terms of the present contract.”

Bahnz stared at me. “A motor ?”

“The biggest motor there is, my dear fellow. It’s called the Earth.”

He blinked, his mind obviously struggling to figure out what I meant.

“Have a good trip, Colonel,” I said. “And any time you’re in the neighborhood, do stop by for a Slingshot.”

“Rutter!”

I turned away and launched myself toward the window at the far end of the control room.

“RUTTER!”

The voice faded behind me as I drifted up to the crystal port. Outside, the big, ugly tanks lay like roc eggs in a row, waiting to be hatched. I could almost envision it. They’d someday transform themselves into great birds of space. And our grandchildren would ride their offspring to the stars.

Bright silvery cables seemed to stretch all the way to the huge blue globe overhead. And I know, now, that they did indeed anchor us to the Earth… an Earth that does not end at a surface of mountain and plain and water, nor with the ocean of air, but continues outward in strong fingers of force, caressing her children still.

Right now those tethers were carrying over a hundred amps of current from B Deck to A. There, electrons were sprayed out into space by an array of small, sharp cathodes.

We could have used the forward process to extract energy from our orbital momentum. I had told Emily Testa earlier today that that would solve nothing. Our problem was to increase our momentum.

Current in a wire, passing through a magnetic field… You could run a dynamo that way, or a motor . With more solar power than we’ll ever need, we can shove the current through the cables against the electromotive force, feeding energy to the Earth, and to our orbit.

A solar-powered motor, turning once per orbit, our Tank Farm rises without shedding an ounce of precious mass.