The Lamp Budget

The cabin rejected their survival plan for the third time.

A red line crawled across the wall screen and stopped under the same word as before.

Energy.

Maya put both palms on the metal table. The table was bolted to the floor, and so were the chairs, and so was the tiny sleeping shelf, because the training cabin had been built by people who did not trust anything to stay where it belonged.

"We cut the window heater," she said.

Soren looked at his paper sheet, which the cabin cameras had already called obsolete twice. "We cut the cup printer. We cut the entertainment wall. We cut the floor warmer. We have power left. Twelve watts spare. It says so."

The quartermaster leaned in through the hatch with a crate hooked under one arm. She wore three inventory bands on her wrist, all chiming softly at different speeds.

"You are trying to make the cabin too clever," she said. "Emergency pods are not clever. They keep air moving, water clean, and bodies warm. Try again with fewer luxuries."

"Questions are not luxuries," Maya said.

The quartermaster smiled as if Maya had made a joke in a language she almost understood. "Questions do not go on the power board. Pumps do."

She pushed away down the corridor, one boot tapping the handrail, already counting something else.

The hatch clicked shut.

The cabin was part of the public deck of Waystation Lark, where everything had a label because visitors liked labels. The air tasted faintly green from the algae tanks below. Through the round window, Earth slid past in blue and white pieces, too large to fit in one look.

Soren read the rejection aloud. "Electrical budget acceptable. Thermal budget acceptable. Water budget acceptable. Metabolic energy deficit."

Maya stopped moving.

"Say the last part again."

"Metabolic energy deficit."

"Not battery," she said.

Soren's pencil hovered. "Body battery."

They had been treating the cabin like a machine with two passengers added at the end, the way adults spoke about cargo. But the wall screen did not show cargo. It showed two small human outlines, each with arrows for oxygen going in, carbon dioxide going out, heat spreading, water leaving, water returning.

Maya dragged the food drawer open. Inside were silver meal tiles, each stamped with a number of kilocalories and a flavor that sounded better than it could possibly be. Tomato Comet. Lunar Peach. Soup, Plain.

"We packed enough," Soren said.

"For muscles?"

"For bodies."

"Which part of bodies?"

He looked at her. Then he looked at the human outlines.

The cabin lights hummed overhead. Not loudly. Just enough that silence had edges.

Soren turned to a different page. "At rest, a person is around one hundred watts. More or less. Food becomes heat and work."

"We are resting."

"Mostly."

Maya began removing items from the manifest with quick taps. Spare socks. Foldable game net. Third towel. The red line did not move.

"It is not those," she said.

Soren pressed the help button beside metabolic budget. The cabin did not summon an adult. It unfolded a transparent diagram from the wall, a ghost of a human body rotating slowly in the air.

Most of it glowed dimly.

The head glowed bright.

Maya leaned closer. "That is rude."

Soren read the small label at the base. "Brain, approximately two percent of body mass. Approximately twenty percent of resting energy use. About twenty watts."

The ghost body turned, and the bright head turned with it.

Twenty watts was not much on the station power board. It was a reading lamp. A small old-fashioned bulb. A dim amber thing in a room full of clean white panels.

But in the body diagram, the little bright place took one fifth of everything.

Maya touched her forehead with two fingers, as if checking for heat.

"We are carrying bulbs," she said.

"Wet bulbs," Soren said.

"Hungry bulbs."

He smiled, then stopped smiling because the wall screen was still red.

The training problem was supposed to be simple. Two crew. One small cabin. Forty eight hours waiting for rescue after a supply craft missed its dock. Enough battery, enough filters, enough water, enough food.

They had enough food by the adult checklist. They did not have enough for the way the cabin counted them.

Soren pulled one meal tile from the drawer and held it under the scanner. "This is two hundred kilocalories. A kilocalorie per hour is about one point something watts. So a brain for a day is around four hundred or five hundred kilocalories."

"Each?"

"Each."

Maya stared at the drawer.

The flavors sat there in neat silver rows. Tomato Comet. Lunar Peach. Soup, Plain. Not snacks. Not prizes. Not comfort. Firewood.

"The quartermaster counted meals like boxes," Maya said. "The cabin counts them like power."

Soren nodded, already sorting. "If we bring the denser emergency paste instead of the regular tiles, we gain energy without much mass."

Maya wrinkled her nose. Emergency paste was gray and famous. It came in strips and tasted, according to station rumor, like someone had described bread to a sponge.

"Do it," she said.

They swapped the food. The red line shrank but did not vanish.

Soren frowned. "Still short."

Maya looked around the cabin. The table. The shelf. The panel. The little display where the simulation showed them both awake for the whole emergency.

"Why are we awake?" she asked.

"Because it is a training exercise."

"No. In the manifest. Why are we awake all the time?"

Soren tapped the schedule. Two crew awake, forty eight hours.

"That is wrong," he said.

They did not make a heroic plan. They made an ordinary one. Sleep in turns. Check the filters. Wake to eat, drink, inspect seals, send beacon pulses, then sleep again. The brain would not turn off. The cabin's own note said that. Sleeping brains still used energy. But the rest of the body eased down a little, and the schedule stopped pretending that panic was a life-support system.

The line turned yellow.

Maya lifted one more regular meal tile from the drawer and replaced it with paste.

The line turned green.

For a moment the cabin made no sound except air through the vent.

Then the wall screen changed.

Approved.

The quartermaster opened the hatch just in time to see it.

"There," she said. "Less luxury."

"More brain," Maya said.

The quartermaster blinked.

Soren pointed to the floating body diagram, still glowing bright at the head. "Your food list was right for mass, but short for metabolic energy. The brain is a twenty-watt load. It is not on the electrical board because it is not plugged into the wall."

The quartermaster set her crate down slowly. One inventory band kept chiming until she silenced it with her thumb.

"Twenty watts," she said.

"About," Soren said.

"Per person. All the time."

"Even when nobody is being useful," Maya said.

The quartermaster looked at her, really looked this time, not as cargo, not as a visitor passing through her tidy lists.

"Especially then, maybe," she said. "That is when people notice the leak behind the panel. Or the wrong star in the window."

Maya did not answer. She had already turned back to the wall.

Beside the approved manifest, a small socket had opened under a label.

Brain power comparison. Twenty-watt lamp. Station supplied. Not powered by crew.

A clear bulb sat in a padded cup below it, old and round, with a thin curled filament inside. It looked too delicate for orbit.

Soren picked it up with both hands. "They included the comparison."

"They hid it until we earned it," Maya said.

"That is annoying."

"Yes."

He screwed the bulb into the socket. The filament warmed orange, dim beside the cabin lights, almost nothing.

Then Maya reached to the control strip and lowered the ceiling panels.

The small bulb became a sun for the table.

Their faces appeared in the round window, faint over the black beyond the glass. Two heads, two dark reflections, and between them the little lamp burning with the same amount of power each of their brains was using to stare at it.

Soren's pencil rested untouched on the table.

Maya clipped a second twenty-watt bulb into the empty socket. Soren slid the cabin lights down until only the two small bulbs glowed, side by side, in the round window's black reflection.