Visions, Ventures, Escape Velocities: A Collection of Space Futures

by Ed Finn

  It was true. Everything had changed. Logic was cheap now. Guidance was cheap. What had been a million dollars of guidance and AI in his youth was now cheap enough, small enough, energy-lean enough that you could stuff it into a child’s toy. You could make a lunar spacecraft in a package the size of a bread box, with more computing power than one of the data centers that had powered the first internet revolution.

  Cheap made for easy. A high school had landed a CubeShip smaller than a basketball on the Moon last year. They’d built it themselves in an engineering classroom, fitted it with a tiny ion engine, paid for a commercial launch and commercial in-orbit fueling at NERFS, and flown it slow and steady, beaming back video the whole way.

  The whole mission had cost $50,000.

  The space suit he wore cost a hundred times that. The rest of the gear that kept him alive cost a hundred times what his space suit did. Billions versus tens of thousands. Maybe he was dead weight.

  Maybe he really was useless.

  “You know why you’re really going,” Beth had said.

  He leaned back and smiled, tried not to show how discomfited he was. “Because we’re explorers, Beth. Because exploring the universe is what we do.”

  She snorted.

  He shook his head in mild exasperation. “Fine. Let me guess. You’re going to say … politics.” He couldn’t deny it played a role. The asteroid mission had been planned as uncrewed. Word was that Congress had privately demanded a face the public could see. And why shouldn’t they? Sending a person up there meant a hell of a lot more than any number of drones.

  Beth looked at him. “Worse, Ryan. It’s PR.”

  He’d raised an eyebrow.

  “PR,” she repeated. “A story. A narrative. PR in a world where robots build everything, where software drives the trucks that deliver what we want, where software diagnoses what’s wrong with you, and software guides the scalpel. PR to tell people they aren’t useless. To convince people they’re relevant again.”

  He gnawed on that one. “What’s wrong with that, Beth? With giving people some hope?”

  She frowned at him. “It’s a lie. That’s what’s wrong. It’s a fairy tale. Is that what you want to be? Just a pretty face for the cameras, to make people back here feel better about their lives?”

  God damn, she could cut when she wanted to.

  Beth shook her head at him. “Are you an astronaut, Ryan? Or an actor?”

  Ryan pursed his lips and turned away from NERFS to prepare for second stage separation, and the trip out to the asteroid.

  Water. Water was life. Water was fuel. Water was the key to exploring the solar system.

  Fuel up a rocket on Earth, at the bottom of a steep gravity well. Use whatever fuel you want: hydrazine, or pure liquid hydrogen and oxygen, like his ship used, or the aluminum compounds they still used in solid rocket boosters. Any fuel, it didn’t matter.

  That fuel made up almost all the weight of your spacecraft.

  Fire your engines, launch into space. Not even far into space—just to LEO—Low Earth Orbit. Most of what your engines were lifting was fuel. The ship he’d launched on weighed a hundred thousand kilos, empty. It weighed a million kilos filled up with fuel.

  All the energy you used getting into orbit—most of it was spent moving the fuel that provided that energy.

  What if you wanted to go farther? What if you wanted to reach the Moon, or an asteroid, or Mars, or even one of the outer planets?

  All that fuel had to be lifted too. For every kilo of fuel you needed to spend after you broke orbit, you’d need around ten kilos of additional fuel just to provide the energy to get it into orbit.

  It was a damn expensive way to fly.

  What if there was another way? A way to have fuel already waiting for you in space? Not fuel launched from the energy-sapping gravity well of Earth, but from a much friendlier place, with weaker gravity, that extracted a smaller tax as you escaped the curve it made in space-time.

  The Moon was where it started. There was ice at the Moon’s poles, in the shadows of craters that shielded it from the sun.

  Ice was liquid water. Astronauts could one day use that water to grow food. But more importantly, just now, water was potential fuel.

  Take water. Add electricity, generated by solar panels or a nuclear thermoelectric plant you’d launched into space. Use the electricity to split each water molecule into hydrogen and oxygen. For every two water molecules, you’d generate one molecule of O2, another two molecules of H2. Oxygen and hydrogen. An explosive combination. The very ingredients his engines ran on.

  With that H2 and O2, you could refuel the craft that had landed on the Moon. You could give it enough fuel to launch itself and to carry yet more water up, into orbit, where spacecraft from Earth could use it. And because the Moon’s gravity was just a tenth as strong as Earth’s, launching one kilo of fuel only required burning one kilo of fuel, unlike the ten kilos you’d have to burn to launch that same amount of fuel from Earth.

  Win.

  Now go a step further. There are other ways to get energy in space. You can use solar panels or radioisotopes. What you really need in fuel isn’t the energy content. It’s the reaction mass. For every action there’s an equal and opposite reaction, after all. To accelerate your ship forward, you have to push something out of your engines in the opposite direction. You can push a lot of mass out at a slow velocity. Or you can push a tiny amount of mass out at an incredible velocity. Both provide the same push. One of them, of course, expends a lot more mass to accelerate your ship than the other. All things being equal, you want whatever you’re pushing out the back of your ship to be hurled out at the highest velocity possible.

  Enter the ion engine. Take that water you’ve brought up from the Moon. Don’t split it into hydrogen and oxygen—the thrust you get when you burn the hydrogen is slow thrust, expelling lots of mass to move you forward. Instead, take those water molecules and ionize them. Strip off electrons so the molecules have a positive charge. Then use an electric field to accelerate them out the back of your ship at incredible velocities, one molecule at a time.

  The thrust is weak. It’s limited by the electricity your ship can provide, which isn’t all that much. You can’t accelerate out of a gravity well. You can’t accelerate fast no matter what.

  But it’s oh-so-efficient. Bit by bit, you can build up speed. And you can get where you’re going on a tiny fraction of the fuel required by a chemical rocket.

  That is, a robot can. An uncrewed mission, living off electrons, has all the time in the world to make a journey. And if in that long journey we lose one or two, so what? Robots are cheap now. Send more.

  You? Flesh and blood? A longer trip means more supplies. It means more radiation. It means more complex life-support systems, running for longer times, accumulating the risk of malfunction.

  Humans have to go quickly, or not at all. And quick means wasteful chemical engines. Quick means lots of fuel. Heavy, expensive fuel, pushing all the extra mass needed to keep you alive, and fed, and watered.

  Asteroids have water too.

  From his tether on the surface, Ryan watched the giant mirror unfurl above him, its microns-thick skin unfolding, bit by bit, as slender, rigid carbon struts stretched them into shape.

  A giant curved section of a sphere, hundreds of meters across, the mirror was much larger than the asteroid that gave it purpose. The mirror’s vast array would focus light on the plastic-wrapped bundle of asteroid material floating a hundred meters or so off the surface of the rock (placed there by robots, of course).

  The asteroid contained relatively tiny amounts of water and organic compounds. But apply heat—in the form of concentrated sunlight—and you could liberate that water and those organics. The volatiles would bubble out of the asteroid material, trapping themselves in the plastic envelope that surrounded them.

  You’d have fuel. Fuel that was farther from Earth in distance, but closer in energy. Fuel on the surface of an ast
eroid where gravity was less than 1% of that on Earth, where landing was computationally difficult but energetically cheap, where launching the fuel was even cheaper than on the Moon, nearly doubling the yield of water you produced.

  In space, water was far more precious than gold. And they were going to mine it from these rocks, heat it out of them, demonstrate that future colonists could live off that water, and ship it back to NERFS in Earth orbit to use as fuel for future missions, that could reach yet more asteroids, liberating more fuel, building that roadway into space for humans to follow.

  A voice spoke inside his helmet, synthesized, neutral. “Mirror unfurl successful.” The same message appeared on his visor. MIRROR UNFURL SUCCESSFUL.

  Ryan repeated the words out loud for posterity. “Mirror unfurl successful.”

  He smiled wryly. This was theatre. And he supposed he was okay with it. The mission didn’t need him to give commands. But if that helped inspire some kid back on Earth, well, there were worse things to do with your life.

  “Proceed with mirror alignment,” he said out loud.

  Up above, tiny gusts of thrust maneuvered the expanded mirror, rotating it slightly, to focus the sun’s rays on the bundle of asteroid material they were using as a test.

  Status messages from the test began to appear on Abrams’s visor. Alignment data. The angle grew closer and closer … then a lock! The sun’s reflected rays were focused on the bundle, magnified thousands of times as the convex mirror concentrated the collected sunlight that hit its entire span onto an area just a meter across.

  Temperature sensors inside the bundle came alive. Heat was reaching the interior, warming it, slowly, slowly.

  Abrams almost held his breath. “Come on,” he muttered to himself. “Come on!” He waited, waited, waited, as the temperature rose.

  Then: pay dirt! A moisture sensor chirped. Water was emerging! An organic sensor next!

  OVERPRESSURE ALERT

  Ryan’s suit flashed the message in red. He barely registered it before something slammed into his side, spinning him around, sending him flying.

  SUIT INTEGRITY COMPROMISED

  The tether. The world spun fast and hard, asteroid, black sky, asteroid, black sky, asteroid slightly further, black sky. His tether had to catch!

  ANCHOR LOST

  He felt a jolt of raw panic.

  SUIT INTEGRITY COMPROMISED

  He was still spinning, the asteroid surface just a few meters away now. He lunged with his arms, thrusting his legs back to counterbalance. Suit integrity could wait. He had to reestablish contact with the rock!

  One suited finger brushed asteroid surface.

  Then nothing.

  Shit!

  “Emergency! Emergency!” he screamed.

  Calm down. Take a breath. Get your head back. Think your way out of it. Issue one: suit damage.

  Abrams reached into a thigh pouch, pulled a suit patch kit free, with its oversized roll of vacuum-ready tape.

  The suit showed him exactly where it had been ripped: a wide swath across the right side of his hip, where his attachment point to the tether had been ripped loose.

  Jesus Christ. Something popped out of the bundle. Fast and hot. A few inches over, and …

  No time to think about that. Self-repair layers had already constricted at the site of the leak, pulling the inner and outer linings of the suit together, trying to plug the hole, but not quite succeeding.

  Ryan ripped long sheets of tape free of the suit patch kit, applied them crisscross over the tear, overlaying one over another, working quickly.

  The world spun around him, stars wheeling, again and again. He was nauseous from it. Nauseous from watching the asteroid drift further and further away.

  Focus! Rip the tape strips free. Apply. Apply. The leak slowed, finally, slowed almost to nothing.

  Emergency gas reserves repressurized the suit. A hiss emerged at the site of the leak, as higher pressure tried to force itself through. Ryan applied more sealing tape, until at last the status lights went green.

  Damn, the asteroid was so far now. And he was spinning so fast.

  Can’t get sick. Can’t get sick.

  He had to slow his spin. His eyes found the roll of tape in his hand.

  Reaction mass. Every action requires an equal and opposite reaction.

  Was he really going to throw his suit patch kit away?

  He ripped two more strips off, attached just their ends to his forearm, to keep them in reserve. Then he cocked his hand back, clutching the roll of tape, and waited. He had to time this just right.

  His spin came around again. The asteroid, at least a hundred meters now, and rotating away, away.

  Time the throw right, and he could stop his spin, and at the same time, propel himself back towards the rock.

  Spin … spin … spin … Throw!

  He hurled the tape as hard as he possibly could in the suit, at the very moment when he thought the asteroid was directly behind him.

  His spin slowed. It didn’t stop.

  Shit.

  The asteroid came around again.

  Ryan waited, made another slow turn.

  And there it was again. A little further. He’d slowed his escape velocity, but hadn’t canceled it. He was still drifting out into interplanetary space.

  Double shit.

  “Stay cool, Abrams,” he said aloud.

  The ship! He could launch the ship, it if was still in one piece. Put it under manual control, maneuver it to pick him up.

  The launch protocol took 30 minutes. Abrams checked his air.

  Eighteen minutes left. Triple shit.

  “Begin ALM launch sequence,” he said aloud, anyway. Open space rotated into view, the asteroid behind him now. He’d find a way. He’d take shortcuts. He could do this.

  He spun slowly around, frantically reviewing his memories of the launch protocol, searching for ways to short-circuit the launch checks via remote control.

  What the hell?

  A CALTROP was floating towards him—torn free from the surface by whatever had ripped him loose, no doubt.

  It floated closer, then rotated out of sight as he spun around. He felt the soft press of its impact as it hit him in the back. And the damn thing adhered, he was sure of it. He could feel its manipulators attaching and detaching, feel it crawling on him. Jesus. He did not want that thing deploying a sample drill.

  “CALTROP remote control interface,” he ordered.

  Dots appeared in his situational view, dozens of dots, a long line of them. What the—

  As he spun around, his eyes went wild. It was a messy line of CALTROPs, all headed his way, gaining on him.

  Shit! Every one of them would pass momentum on to him when they hit him, pushing him further away from the asteroid. How the hell was he going to avoid them?

  He felt a surge of pressure on his back, momentary and then gone.

  Equal and opposite reaction. Propel a lot of reaction mass slowly. Or a little, quickly. The damn things were trying to thrust him back to the asteroid.

  The next one made contact on the undamaged hem of his suit. It crawled around until it was above one kidney, at the small of his back, slightly off to the side.

  As the asteroid moved into view, the CALTROP’s legs surged out from underneath it, sending it hurtling out into space, far faster than it had been moving when it made contact.

  One by one they docked with him, making contact softly, at a few meters per second. They’d crawl into position, then hurl themselves outward far faster than they’d met him.

  His spin slowed, then ended.

  The asteroid stopped receding. Then it started growing in his vision again, coming closer. His ship started growing. The damned CALTROPs had actually put him back on course. His air ticked down, and he forced himself to breathe slowly, calmly.

  There were two minutes of air left when he reached the airlock and let himself into the safety of the ALM.

  “I was a liability,” he told
Beth Wu, months later, after his emergency return to Earth. “You lost a lot of bots rescuing me.”

  She arched an eyebrow at him. “Actually, we learned things. That emergency protocol worked. And we need redundant tethers, at least.” She smiled then. “You were useful.”

  Ryan sighed. “You don’t have to do that, Beth. I didn’t accomplish anything up there. You wasted infrastructure and money on me.”

  Beth shook her head. “Ryan—you matter. Those bots don’t. You still don’t get it. Space is for us. Those bots? They’re just tools. And they did what they were supposed to do. They made space just a little bit safer for the people that matter.” She smiled, then. “Like you.”

  Toward Asteroid Exploration

  by Roland Lehoucq

  Asteroids are fascinating small worlds. Like fossils they are a kind of time machine, providing us with glimpses of the earliest days of our solar system. The evolution of life on our planet is linked with asteroids: impacts on the primordial Earth may have delivered water and other volatiles and, maybe, the basic molecules for life. But asteroids’ impact on our world is not solely limited to the past—or to the emergence of life. Though the probability of such collisions is low, any significant impact poses a threat to our civilization. In order to effectively prepare for or counter a potential asteroid strike and minimize the loss of life, we must be able to detect such celestial threats and accurately predict their flight path. The design of efficient mitigation strategies will require asteroid detection through ground- and space-based surveys as well as knowledge of their physical properties. But asteroids offer potential as well as peril: the proximity of some of them to Earth may allow future astronauts or robotic probes to harvest their water, volatiles, and mineral resources. Future large-scale commercial activities in space will require the use of raw materials obtained from in-space sources rather than from Earth, to circumvent the high cost of Earth launch. Developing a system through which we can access asteroids either to deflect them or to extract their materials in an efficient way aids humanity in both avoiding a global disaster and initiating space industrialization. Moreover, crewed exploration of asteroids will serve as a testing ground for our efforts to send humans to Mars, the ultimate goal being to make space more accessible to humankind.