Space

STEPHEN BAXTER
SPACE
MANIFOLD 2

COPYRIGHT

HarperVoyager an imprint of HarperCollinsPublishers Ltd 1 London Bridge Street London SE1 9GF

www.harpervoyagerbooks.co.uk

First published in Great Britain by HarperVoyager 2000

Copyright © Stephen Baxter 2000

Cover image of Calabi-yau manifold © Laguna Design/Getty Images

Cover layout design © HarperCollinsPublishers Ltd 2015

Stephen Baxter asserts the moral right to be identified as the author of this work.

A catalogue copy of this book is available from the British Library.

This novel is entirely a work of fiction. The names, characters and incidents portrayed in it are the work of the author’s imagination. Any resemblance to actual persons, living or dead, events or localities is entirely coincidental.

All rights reserved under International and Pan-American Copyright Conventions. By payment of the required fees, you have been granted the non-exclusive, non-transferable right to access and read the text of this e-book on screen. No part of this text may be reproduced, transmitted, down-loaded, decompiled, reverse engineered, or stored in or introduced into any information storage and retrieval system, in any form or by any means, whether electronic or mechanical, now known or hereinafter invented, without the express written permission of HarperCollins.

Source ISBN: 9780008134471

Ebook Edition © November 2012 ISBN 9780007499793

Version: 2015-09-01

DEDICATION

To my nephew, Thomas Baxter andSimon Bradshaw and Eric Brown

EPIGRAPH

Innumerable suns exist; innumerable earths

revolve around these suns in a manner similar to

the way the seven planets revolve around our

sun. Living beings inhabit these worlds …

GIORDANO BRUNO (1548–1600)

If they existed, they would be here.

ENRICO FERMI (1901–1954)

CONTENTS

Cover

Title Page

Copyright

Dedication

Epigraph

Prologue

Part I: Foreigners

Chapter 1: Gaijin

Chapter 2: Baikonur

Chapter 3: Debates

Chapter 4: Ellis Island

Chapter 5: Saddle Point

Chapter 6: Transmission

Chapter 7: Reception

Part II: Travellers

Chapter 8: Ambassadors

Chapter 9: Fusion Summer

Chapter 10: Travels

Chapter 11: Anomalies

Chapter 12: Sister Planet

Chapter 13: The Roads of Empire

Chapter 14: Dreams of Ancestral Fish

Chapter 15: Colonists

Chapter 16: Icosahedral God

Chapter 17: Lessons

Part III: Trenchworks

Chapter 18: Moon Rain

Chapter 19: Dreams of Rock and Stillness

Chapter 20: The Tunnel in The Moon

Chapter 21: Homecoming

Chapter 22: Triton Dreamtime

Chapter 23: Cannonball

Part IV: Bad News From The Stars

Chapter 24: Kintu’s Children

Chapter 25: Wanpamba’s Tomb

Chapter 26: Kimera’s Breath

Chapter 27: The Face of Kintu

Chapter 28: People Came From Earth

Chapter 29: Bad News From The Stars

Chapter 30: Refuge

Chapter 31: End Game

Part V: The Children’s Crusade

Chapter 32: Savannah

Chapter 33: The Fermi Paradox

Chapter 34: The Children’s Crusade

Epilogue

Afterword

Keep Reading

Acknowledgements

About the Author

Also by Stephen Baxter

About the Publisher

PROLOGUE

My name is Reid Malenfant.

You know me. And you know I’m an incorrigible space cadet.

You know I’ve campaigned for, among other things, private mining expeditions to the asteroids. In fact, in the past I’ve tried to get you to pay for such things. I’ve bored you with that often enough already, right?

So tonight I want to be a little more personal. Tonight I want to talk about why I gave over my life to a single, consuming project.

It started with a simple question:

Where is everybody?

As a kid I used to lie at night out on the lawn, soaking up dew and looking at the stars, trying to feel the Earth turning under me. It felt wonderful to be alive – hell, to be ten years old, anyhow.

But I knew that the Earth was just a ball of rock, on the fringe of a nondescript galaxy.

As I lay there staring at the stars – the thousands I could pick out with my naked eyes, the billions that make up the great wash of our Galaxy, the uncounted trillions in the galaxies beyond – I just couldn’t believe, even then, that there was nobody out there looking back at me down here. Was it really possible that this was the only place where life had taken hold – that only here were there minds and eyes capable of looking out and wondering?

But if not, where are they? Why isn’t there evidence of extraterrestrial civilization all around us?

Consider this. Life on Earth got started just about as soon as it could – as soon as the rocks cooled and the oceans gathered. Of course it took a good long time to evolve us. Nevertheless we have to believe that what applies on Earth ought to apply on all the other worlds out there, like or unlike Earth; life ought to be popping up everywhere. And, as there are hundreds of billions of stars out there in the Galaxy, there are presumably hundreds of billions of opportunities for life to come swarming up out of the ponds – and even more in the other galaxies that crowd our universe.

Furthermore, life spread over Earth as fast and as far as it could. And already we’re starting to spread to other worlds. Again, this can’t be a unique trait of Earth life.

So, if life sprouts everywhere, and spreads as fast and as far as it can, how come nobody has come spreading all over us?

Of course the universe is a big place. There are huge spaces between the stars. But it’s not that big. Even crawling along with dinky ships that only reach a fraction of lightspeed – ships we could easily start building now – we could colonize the Galaxy in a few tens of millions of years. One hundred million, tops.

One hundred million years: it seems an immense time – after all, a hundred million years ago the dinosaurs ruled Earth. But the Galaxy is a hundred times older still. There has been time for Galactic colonization to have happened many times since the birth of the stars.

Remember, all it takes is for one race somewhere to have evolved the will and the means to colonize; and once the process has started it’s hard to see what could stop it.

But, as a kid on that lawn, I didn’t see them. I seemed to be surrounded by emptiness and silence.

Even we blare out on radio frequencies. Why, with our giant radio telescopes we could detect a civilization no more advanced than ours anywhere in the Galaxy. But we don’t.

More advanced civilizations ought to be much more noticeable. We could spot somebody building a shell around their star, or throwing in nuclear waste. We could probably see evidence of such things even in other galaxies. But we don’t. Those other galaxies, other reefs of stars, seem to be as barren as this one.

Maybe we’re just unlucky. Maybe we’re living at the wrong time. The Galaxy is an old place; maybe They have been, flourished, and gone already. But consider this: even if They are long gone, surely we should see Their mighty ruins, all around us. But we don’t even see that. The stars show no signs of engineering. The solar system appears to be primordial, in the sense that it shows no signs of the great projects we can already envisage, like terraforming the planets, or tinkering with the sun, and so on.

We can think of lots of rationalizations for this absence.

Maybe there is something that kills off every civilization like ours before we get too far – for example, maybe we all destroy ourselves in nuclear wars or eco collapse. Or maybe there is something more sinister, plagues of killer robots sliding silently between the stars, which for their own antique purposes kill off fledgling cultures.

Or maybe the answer is more benevolent. Maybe we’re in some kind of quarantine – or a zoo.

But none of these filtering mechanisms convinces me. You see, you have to believe that this magic suppression mechanism, whatever it is, works for every race in this huge Galaxy of ours. All it would take would be for one race to survive the wars, or evade the vacuum robots, or come sneaking through the quarantine to sell trinkets to the natives – or even just to start broadcasting some Eetie version of The Simpsons, anywhere in the Galaxy – and we’d surely see or hear them.

But we don’t.

This paradox was first stated clearly by a twentieth-century physicist called Enrico Fermi. It strikes me as a genuine mystery. The contradictions are basic: life seems capable of emerging everywhere; just one starfaring race could easily have covered the Galaxy by now; the whole thing seems inevitable – but it hasn’t happened.

Thinking about paradoxes is the way human understanding advances. I think the Fermi paradox is telling us something very profound about the universe, and our place in it. Or was.

Of course, everything is different now.

I
FOREIGNERS

AD 2020–2042

… And he felt as if he was drowning, struggling up from some thick, viscous fluid, up towards the light. He wanted to open his mouth, to scream – but he had no mouth – and no words. What would he scream?

I.

I am.

I am Reid Malenfant.

He could see the sail.

It was a gauzy sheet draped across the crowded stars of this place – where, Malenfant? why, the core of the Galaxy, he thought, wonder breaking through his agony – and within the sail, cupped, he could see the neutron star, an angry ball of red laced with eerie synchrotron blue, like a huge toy.

A star with a sail attached to it. Beautiful. Scary.

Triumph surged. I won, he thought. I resolved the koan, the great conundrum of the cosmos; Nemoto would be pleased. And now, together, we’re fixing an unsatisfactory universe. Hell of a thing.

… But if you see all this, Malenfant, then what are you?

He looked down at himself.

Tried to.

A sense of body, briefly. Spread-eagled against the sail’s gauzy netting. Clinging by fingers and toes, monkey digits, here at the centre of the Galaxy. A metaphor, of course, an illusion to comfort his poor human mind.

Welcome to reality.

The pain! Oh, God, the pain.

Terror flooded over him. And anger.

And, through it, he remembered the Moon, where it began …

Chapter 1
GAIJIN

A passenger in the HOPE-3 tug, Reid Malenfant descended towards the Moon.

The Farside base, called Edo, was a cluster of concrete components – habitation modules, power plants, stores, manufacturing facilities – half-buried in the cratered plain. Comms masts sprouted like angular flowers. The tug pad was just a splash of scorched Moon-dust concrete, a couple of kilometres further out. Around the station itself, the regolith was scarred by tractor traffic.

Robots were everywhere, rolling, digging, lifting; Edo was growing like a colony of bacilli in nutrient.

A hi-no-maru, a Japanese sun flag, was fixed to a pole at the centre of Edo.

‘You are welcome to my home,’ Nemoto said.

She met him in the pad’s airlock, a large, roomy chamber blown into the regolith. Her face was broad, pale, her eyes black; her hair was elaborately shaved, showing the shape of her skull. She smiled, apparently habitually. She could have been no more than half Malenfant’s age, perhaps thirty.

Nemoto helped Malenfant don the suit he’d been fitted with during the flight from Earth. The suit was a brilliant orange. It clung to him comfortably, the joints easy and loose, although the sewn-in plates of tungsten armour were heavy.

‘It’s a hell of a development from the old EMUs I wore when I was flying Shuttle,’ he said, trying to make conversation.

Nemoto listened politely, after the manner of young people, to his fragments of reminiscence from a vanished age. She told him the suit had been manufactured on the Moon, and was made largely of spider silk. ‘I will take you to the factory. A chamber in the lunar soil, full of immense spinnerets. A nightmare vision! …’

Malenfant felt disoriented, restless.

He was here to deliver a lecture, on colonizing the Galaxy, to senior executives of Nishizaki Heavy Industries. But here he was being met off the tug by Nemoto, the junior researcher who’d invited him out to the Moon, just a kid. He hoped he wasn’t making some kind of fool of himself.

Reid Malenfant used to be an astronaut. He’d flown the last Shuttle mission – STS-194, on Discovery – when, ten years ago, the space transportation system had reached the end of its design life, and the International Space Station had finally been abandoned, incomplete. No American had flown into space since – save as the guest of the Japanese, or the Europeans, or the Chinese.

In this year 2020, Malenfant was sixty years old and feeling a lot older – increasingly stranded, a refugee in this strange new century, his dignity woefully fragile.

Well, he thought, whatever the dubious politics, whatever the threat to his dignity, he was here. It had been the dream of his long life to walk on another world. Even if it was as the guest of a Japanese.

And even if he was too damn old to enjoy it.

They stepped through a transit tunnel and directly into a small tractor, a lozenge of tinted glass. The tractor rolled away from the tug pad. The wheels were large and open, and absorbed the unevenness of the mare; Malenfant felt as if he were riding across the Moon in a soap bubble.

Every surface in the cabin was coated with fine, grey Moon dust. He could smell the dust; the scent was, as he knew it would be, like wood ash, or gunpowder.

Beyond the window, the Mare Ingenii – the Sea of Longing – stretched to the curved horizon, pebble-strewn. It was late in the lunar afternoon, and the sunlight was low, flat, the shadows of the surface rubble long and sharp. The lighting was a rich tan when he looked away from the sun, a more subtle grey elsewhere. Earth was hidden beneath the horizon, of course, but Malenfant could see a comsat crawl across the black sky.

He longed to step through the glass, to touch that ancient soil.

Nemoto locked in the autopilot and went to a little galley area. She emerged with green tea, rice crackers and dried ika cuttlefish. Malenfant wasn’t hungry, but he accepted the food. Such items as the fish were genuine luxuries here, he knew; Nemoto was trying to honour him.

The motion of the tea, as she poured it in the one-sixth gravity, was complex, interesting.

‘I am honoured you have accepted my invitation to travel here, to Edo,’ Nemoto said. ‘You will of course tour the town, as you wish. There is even a Makudonarudo here. A McDonald’s. You may enjoy a bifubaaga! … soya, of course.’

He put down his plate and tried to meet her direct gaze. ‘Tell me why I’ve been brought out here. I don’t see how my work, on long-term space utilization, can be of real interest to your employers.’

She eyed him. ‘You do have a lecture to deliver, I am afraid. But – no, your work is not of primary concern to Nishizaki.’

‘Then I don’t understand.’

‘It is I who invited you, I who arranged the funding. You ask why. I wished to meet you. I am a researcher, like you.’

‘Hardly a researcher,’ he said. ‘I call myself a consultant, nowadays. I am not attached to a university.’

‘Nor I. Nishizaki Heavy Industries pay my wages; my research must be focused on serving corporate objectives.’ She eyed him, and took some more fish. ‘I am salariman. A good company worker, yes? But I am, at heart, a scientist. And I have made some observations which I am unable to reconcile with the accepted paradigm. I searched for recent scientific publications concerning the subject area of my – hypothesis. I found only yours.

‘My subject is infrared astronomy. At our research station, away from Edo, the company maintains radiometers, photometers, photopolarimeters, cameras. I work at a range of wavelengths, from twenty to a hundred microns. Of course a space-borne platform is to be preferred: the activities of humankind are thickening the Moon’s atmosphere with each passing day, blocking the invisible light I collect. But the lunar site is cheap to maintain, and is adequate for the company’s purposes. We are considering the future exploitation of the asteroids, you see. Infrared astronomy is a powerful tool in the study of those distant rocks. With it we can deduce a great deal about surface textures, compositions, internal heat, rotation characteristics –’

‘Tell me about your paradigm-busting hypothesis.’

‘Yes.’ She sipped her green tea. She said calmly, ‘I believe I have observational evidence of the activity of extraterrestrial intelligences in the solar system.’

The silence stretched between them, electric. Her words were shocking, quite unexpected.

But now he saw why she’d brought him here.

Since his retirement from NASA, Malenfant had avoided following his colleagues into the usual ex-astronaut gravy ponds, lucrative aerospace executive posts and junior political positions. Instead, he’d thrown his weight behind research into what he regarded as long-term thinking: SETI, using gravitational lensing to hunt for planets and Eetie signals, advanced propulsion systems, schemes for colonizing the planets, terraforming, interstellar travel, exploration of the venerable Fermi paradox.

All the stuff that Emma had so disapproved of. You’re wasting your time, Malenfant. Where’s the money to be made out of gravitational lensing? …

But his wife was long gone, of course. Struck down by cancer: the result of a random cosmic accident, a heavy particle that had come whizzing out of an ancient supernova and flown across the universe to damage her just so … It could have been him; it could have been neither of them; it could have happened a few years later, when cancer had been reduced to a manageable disease. But it hadn’t worked out like that, and Malenfant, burnt out, already grounded, had been left alone.

So he had thrown himself into his obsessions. What else was there to do?

Well, Emma had been right, and wrong. He was making a minor living on the lecture circuit. But few serious people were listening, just as she had predicted. He attracted more knee-jerk criticism than praise or thoughtful response; in the last few years, he’d become regarded as not much more than a reliable talk-show crank.

But now, this.

He tried to figure how to deal with this, what to say. Nemoto wasn’t like the Japanese he had known before, on Earth, with their detailed observance of reigi – the proper manner.

She studied him, evidently amused. ‘You are surprised. Startled. You think, perhaps, I am not quite sane to voice such speculations. You are trapped on the Moon with a mad Japanese woman. The American nightmare!’

He shook his head. ‘It’s not that.’

‘But you must see that my speculations are not so far removed from your own published work. Like myself, you are cautious. Nobody listens. And when you do find an audience, they do not take you seriously.’

‘I wouldn’t be so blunt about it.’

‘Your nation has turned inward,’ Nemoto said. ‘Shrunk back.’

‘Maybe. We just have different priorities now.’ In the US, flights into space had become a hobby of old men and women, dreams of an age of sublimated warfare which had left behind only images of charmingly antique rocket craft, endlessly copied around the data nets. Nothing to do with now.

She said, ‘Then why do you continue, to argue, to talk, to expose yourself to ridicule?’

‘Because –’ Because if nobody thinks it, it definitely won’t happen.

She was smiling at him; she seemed to understand. She said, ‘The kokuminsei, the spirit of your people, is asleep. But in you, and perhaps others, curiosity burns strong. I think we two should defy the spirit of our age.’

‘Why have you brought me here?’

‘I am seeking to resolve a koan,’ she said. ‘A conundrum that defies logical analysis.’ Her face lost its habitual smile, for the first time since they’d met. ‘I need a fresh look – a perspective from a big thinker – someone like you. And –’

‘Yes?’

‘I am afraid, I think,’ she said. ‘Afraid for the future of the species.’

The tractor worked its way across the Moon, following a broad, churned-up path. Nemoto offered him more food.

The tractor drew up at an airlock at the outskirts of Edo. A big NASDA symbol was painted on the lock: NASDA for Japan’s National Space Development Agency. With the minimum of fuss, Nemoto led Malenfant through the airlock and into Edo, into a colony on the Moon.

Here, at its periphery, Edo was functional. The walls were bare, of fused, glassy regolith. Ducts and cables were stapled to the roof. People wore plain, disposable paper coveralls. There was an air of bustle, of heavy industry.

Nemoto led him through Edo, a gentle guided tour. ‘Of course the station is a great achievement,’ she said. ‘No less than ninety-five flights of our old H-2 rockets were required to ferry accommodation modules and power plants here. We build beneath the regolith, for shelter from solar radiation. We bake oxygen from the rocks, and mine water from the polar permafrost …’

At the centre of the complex, Edo was a genuine town. There were public places: bars, restaurants where the people could buy rice, soup, fried vegetables, sushi, sake. There was even a tiny park, with shrubs and bamboo grass; a spindly lunar-born child played there with his parents.

Nemoto smiled at Malenfant’s reaction. ‘At the heart of Edo, ten metres beneath lunar regolith, there are cherry trees. Our children study beneath their branches. You may stay long enough to see ichi-buzaki, the first state of blossoming.’

Malenfant saw no other Westerners. Most of the Japanese nodded politely. Many must have known Nemoto – Edo supported only a few hundred inhabitants – but none engaged her in conversation. His impression of Nemoto as a loner, rather eccentric, was reinforced.

As they passed one group he heard a man whisper, ‘Wah! – gaijin-kusai.’

Gaijin-kusai. The smell of foreigner. There was laughter.

Malenfant spent the night in what passed for a ryokan, an inn. His apartment was tiny, a single room. But, despite the bleak austerity of the fused-regolith walls, the room was decorated Japanese style. The floor was tatami – rice straw matting – polished and worn with use. A tokonoma, an alcove carved into the rock, contained an elaborate data net interface unit; but the owners had followed tradition and had hung a scroll painting there – of a dragonfly on a blade of grass – and some flowers, in an ikebana display. The flowers looked real.

There was a display of cherry blossom, fixed to the wall under clear plastic. The contrast of the pale living pink with the grey Moon rock was the most beautiful thing he had ever seen.

In this tiny room he was immersed in noise: the low, deep rumblings of the artificial lungs of the colony, of machines ploughing outward through the regolith. It was like being in the belly of a huge vessel, a submarine. Malenfant thought wistfully of his own study: bright Iowa sunlight, his desk, his equipment.

Edo kept Tokyo time, so Malenfant, here on the Moon, suffered jet lag. He slept badly.

Rows of faces.

‘… How are we to populate the Galaxy? It’s actually all a question of economics.’ Over Malenfant’s head a virtual image projected in the air of the little theatre, its light glimmering from the folded wooden walls.

Malenfant stared around at the rows of Japanese faces, like coins shining in this rich brown dark. They seemed remote, unreal. Many of these people were NASDA administrators; as far as he could tell there was nobody from Nishizaki senior management here, nominally his sponsors for the trip.

The virtual was a simple schematic of stars, randomly scattered. One star blinked, representing the sun.

Malenfant said, ‘We will launch unmanned probes.’ Ships, little dots of light, spread out from the toy sun. ‘We might use ion rockets, solar sails, gravity assists – whatever. The first wave will be slow, no faster than we can afford. It doesn’t matter. Not in the long term.

‘The probes will be self-replicating: Von Neumann machines, essentially. Universal constructors. Humans may follow, by such means as generation starships. However it would be cheaper for the probes to manufacture humans in situ, using cell synthesis and artificial womb technology.’ He glanced over the audience. ‘You wish to know if we can build such devices. Not yet. Although your own Kashiwazaki Electric has a partial prototype.’

At that there was a stir of interest, self-satisfied.

As his virtual light-show continued to evolve, telling its own story, he glanced up at the walls around him, at the glimmer of highlights from wood. This was a remarkable place. It was the largest structure in Edo, serving as community centre and town hall and showpiece, the size of a ten-storey building.

But it was actually a tree, a variety of oak. The oaks were capable of growing to two hundred metres under the Moon’s gentle gravity, but this one had been bred for width, and was full of intersecting hollowed-out chambers. The walls of this room were of smooth polished wood, broken only subtly by technology – lights, air vents, virtual display gear – and the canned air here was fresh and moist and alive.

In contrast to the older parts of Edo – all those clunky tunnels – this was the future of the Moon, the Japanese were implicitly saying. The living Moon. What the hell was an American doing here on the Moon, lecturing these patient Japanese about colonizing space? The Japanese were doing it, patiently and incrementally working.

But – yes, incrementally: that was the key word. Even these lunar colonists couldn’t see beyond their current projects, the next few years, their own lifetimes. They couldn’t see where this could all lead. To Malenfant, that ultimate destination was everything.

And, perhaps, Nemoto and her strange science would provide the first route map.

The little probe-images had reached their destination stars.

‘Here is the heart of the strategy,’ he said. ‘A target system, we assume, is uninhabited. We can therefore program for massive and destructive exploitation of the system’s resources, without restraint, by the probe. Such resources are useless for any other purpose, and are therefore economically free to us. And so we colonize, and build.’

More probes erupted from each of the first wave of target stars, at greatly increased speeds. The probes reached new targets; and again, more probes were spawned, and fired onwards. The volume covered by the probes grew rapidly; it was like watching the expansion of gas into a vacuum.

He said, ‘Once started, the process is self-directing, self-financing. It would take, we think, ten to a hundred million years for the colonization of the Galaxy to be completed in this manner. But we must invest merely in the cost of the initial generation of probes. Thus the cost of colonizing the Galaxy will be less, in real terms, than that of our Apollo program of fifty years ago.’

His probes were now spreading out along the Galaxy’s spiral arms, along lanes rich with stars. His Japanese audience watched politely.

But as he delivered his polished words he thought of Nemoto and her tantalizing hints of otherness – of a mystery which might render all his scripted invective obsolete – and he faltered.

Trying to focus, feeling impatient, he closed with his cosmic-destiny speech. ‘… This may be a watershed in the history of the cosmos. Think about it. We know how to do this. If we make the right decisions now, life may spread beyond Earth and Moon, far beyond the solar system, a wave of green transforming the Galaxy. We must not fail …’ And so on.

Well, they applauded him kindly enough. But there were few questions.

He got out, feeling foolish.

The next day Nemoto said she would take him to the surface, to see her infrared spectroscopy results at first hand.

They walked through the base to a tractor airlock, and suited up once more. The infrared station was an hour’s ride from Edo.

A kilometre out from Edo itself, the tractor passed one of the largest structures Malenfant had yet seen. It was a cylinder perhaps a hundred and fifty metres long, ten wide. It looked like a half-buried nuclear submarine. The lunar surface here was scarred by huge gullies, evidently the result of strip-mining. Around the central cylinder there was a cluster of what looked like furnaces, enclosed by semi-transparent domes.

‘Our fusion plant,’ Nemoto said. ‘Edo is powered by the fusion of deuterium, the hydrogen isotope, with helium-3.’

Malenfant glared out with morbid interest. Here, as in most technological arenas, the Japanese were way out ahead of Americans. Twenty per cent of the US’s power now came from the fusion of two hydrogen isotopes, deuterium and tritium. But hydrogen fusion processes, even with such relatively low-yield fuel, had turned out to be unstable and expensive: high-energy neutrons smashed through reactor walls, making them brittle and radioactive. The Japanese helium-3 fusion process, by contrast, produced charged protons, which could be kept away from reactor walls with magnetic fields.