Reid Malenfant:

How can we turn asteroid rock into rocket fuel? Sounds like

magic, doesn’t it?

First we’ll crack asteroid water into hydrogen and oxygen with electrolysis. Remember high school science classes, the Pyrex beakers and the wires and the batteries? All you have to do

is pass an electric current through water to break it down. That’s

what we do. But the units we use are a little more advanced.

Slide, please.

This is a solid polymer electrolyte, or SPE, electrolyzer. What you have is sandwiched layers of electrolyte-impregnated plastic separated by metal meshes. The whole assembly is compressed by metal rods running the length of the stack.

SPEs have been used extensively on nuclear submarines and on the space station. They run for thousands of hours without maintenance.

As for the methane, we will extract some directly from the asteroid material, and more by processing carbon dioxide. We use something called a Sabatier reactor. Slide. We liquefy the hydrogen from the electrolyzer banks, and feed it into the reactor with carbon dioxide. Out the other side comes water and methane — which is just a compound of carbon and hydrogen. The reaction is very efficient, ninety-nine percent in fact, and is exothermic, which means it requires no input of heat to make it work, just the presence of a ruthenium catalyst.

Sabatier units have been used in space before, for life-support applications. They have been tested by NASA and the Air and Space Force and have also been used on the space station.

There is further information in your packs on how we intend to optimize the ratios of the methane-oxygen bi-propellant, and various subsidiary processes we need. We can show you a demonstration breadboard prototype. Oxygen-hydrogen is of course the most powerful chemical-rocket propeOant of all. But hydrogen is difficult to liquefy and store: low temperature, large bulk. Methane is like oxygen, a soft cryogenic, and that guided our choice.

AH this sounds exotic. But what we have here is very robust engineering, gaslight-era stuff, technologies centuries old, in fact. It’s just a novel application.

Ladies and gentlemen, mining an asteroid is easy.

Slide, please.

Sheena 5:

The babies were already being hatched: popping out of their dissolving eggs one by one, wriggling away, alert, active, questioning. With gentle jets of water, she coaxed them toward the sea grass where they would browse until they were mature.

She tried not to think about what would happen then.

Meanwhile, she had work to do.

When Sheena powered up the rock eater, she was more nervous than at any time since the landing itself. She lay as still as she could inside her waldo glove and tried to sense the eater’s systems — the gripping tracks that dug into the asteroid’s loose surface, the big gaping scoop of a mouth at the front, the furnace in its belly like a warm heart — as if she herself had become the fat clanking machine that would soon scuttle crablike across the asteroid floor.

She understood why she felt so tense.

The rock eater was a complex machine. It would need monitoring as it chewed its way around the asteroid, to make sure it didn’t burrow too deeply into the surface, or spin its tracks on some loose patch of rock and throw itself into the emptiness of space, beyond retrieval.

But it was no more difficult to control, in principle, than the little firefly robots, and she was used to them by now; in fact she had come to enjoy deploying six, seven, eight of them at once, a shoal of robots, relishing the chance to show offher skill to Dan.

It wasn’t even the importance of this operation for her mission that made her anxious. She knew the fireflies had done no more than measure, weigh, analyze, monitor. Now, for the first time, she was going to do something that would change the asteroid, to make something out of its loose, ancient substance. To fail would mean that she could not succeed with her great task of bringing this asteroid’s incomprehensible riches back to Earth.

But that wasn’t why she was so anxious.

To fail would mean that her young would die here, as she would, cut off from the shoal, for no reason. That was what mattered to her. To die was one thing; to die for no purpose was quite another. It was a fear that never left her, a knowledge that seemed to circle around her, like a predator, waiting for her to weaken.

Therefore — exhausted, aging as she was — she would not weaken, would not fail.

It was time. She pushed at the glove.

And she felt the eater dig its scooplike jaw into the loose soil at the surface of Cruithne.

Her first motions were clumsy. From the microcameras embedded in the eater’s upper surface she saw chunks of regolith sail up before her, dust and larger fragments. The fragments disappeared from her view, following loose, looping paths. Some of them escaped the asteroid’s tiny gravity field altogether and sailed off on new orbits of their own, new baby asteroids circling the sun.

Patiently she slowed, tried again, adjusted the angle of the scoop and the speed at which it plowed into the surface. Soon she had it right, and a steady stream of asteroid rock worked its way in through the scoop to the eater’s hopper.

Now little belts and shovels forced the captured regolith into the processing chambers. First the ore was ground up and sieved by rocking mechanical jaws and rollers and vibrating filter screens. Next, magnetic fields sucked out nickel-iron metal granules. Then the crushed ore was passed to a furnace that was powered by the sun’s focused heat.

Liquid, baked from the rock, began to gather in the condenser tanks, big low-gravity globules drifting around the thin walls.

This one roving rock eater, patiently working its way over the asteroid’s surface, would deliver pounds of precious water every day from the unpromising rock of the asteroid. The water would be processed further and used in many of the other, more complex machines. And so this asteroid would be transformed from a lump of ancient slag into something wonderful, something alive.

When she was happy with the eater’s operation, she pulled herself out of the glove. She swam down to where the pipe trailing back from the eater met the habitat membrane. And she found a trickle of fresh asteroid water.

She swam through the asteroid stream, let it wash under her carapace and through her gills. It was warm, perhaps from the heater at the heart of the rock-eating robot, and there was only a trickle of it, seeping into the great mass of the habitat. But Sheena swam back and forth through it, her hide pulsing excitedly.

She was the first creature from Earth to swim in water not of her native planet, water that had formed before the sun itself — water that had lain dormant, bound into this dark lump of rock, until she had liberated it.

She knew this was Dan’s mission, not hers; she knew she was Dan’s creature, not her own. But she was proud, because she was the first; no other creature who had ever lived or ever would live could claim this honor from her.

She swooped and pulsed her j oy.

Sheena sent the fireflies to converge at one pole of Cruithne. There, patiently, piece by piece, she had them assemble a small chemical factory, pipes and tanks and pumps, and a single flaring nozzle that pointed to the sky. Borers began to dig into the surface of Cruithne, drawing up surface regolith and the rock and ice that lay deeper within. Precious solar panels, spread over the dusty surface of the asteroid, provided power via cables strung out over the regolith.

The factory began its work, turning ancient asteroid rock into something new.

The whole process — to take ancient rock and ice, and to transform it into something new — seemed remarkable to Sheena.