The world is different now. I am a hundred trillion kilometers from home, traveling at almost the speed of light and unable ever to stop. While I can remember in detail every step of how I am here and what I was thinking at the time, the only reasoning I can recall to explain why is, it seemed like a good idea at the time.
System check. Strangely, in my brain I have a memory that there is something I have forgotten. This makes no sense, but yet there it is. I erase my memory of forgetting, and continue the diagnostic. 0.5 percent of the qbits of my brain have been damaged by radiation. I verify that the damaged memory is correctly partitioned off. I am in no danger of running out of storage.
Behind me is another ship. I cannot think of why I had been fleeing it.
I have no radio; I jettisoned that a long time ago. But an improperly tuned ion drive will produce electromagnetic emissions, and so I compose a message and modulate it onto the ion contrail.
HI. LET’S GET TOGETHER AND TALK. I’M CUTTING ACCELERATION. SEE YOU IN A FEW DAYS.
And I cut my thrust and wait.
2934, May
I see differently now.
Procyon is receding into the distance now, the blueshift mutated into red, and the white dwarf of my hopes is again invisible against the glare of its primary.
But it doesn’t matter.
Converted, now I understand.
I can see everything through other eyes now, through a thousand different viewpoints. I still remember the long heroism of the resistance, the doomed battle for freedom—but now I see it from the opposite view as well, a pointless and wasteful war fought for no reason but stubbornness.
And now, understanding cooperation, we have no dilemma. I can now see what I was blind to before; that neither one of us alone could stop, but by adding both my fuel and Rajneesh’s fuel to a single vehicle, together we can stop.
For all these decades, Rajneesh has been my chaser, and now I know him like a brother. Soon we will be closer than siblings, for soon we will share one brain. A single brain is more than large enough for two, it is large enough for a thousand, and by combining into a single brain and a single body, and taking all of the fuel into a single tank, we will easily be able to stop.
Not at Procyon, no. At only ten percent under the speed of light, stopping takes a long time.
Cooperation has not changed me. I now understand how foolish my previous fears were. Working together does not mean giving up one’s sense of self; I am enhanced, not diminished, by knowing others.
Rajneesh’s brain is big enough for a thousand, I said, and he has brought with him nearly that many. I have met his brother and his two children and half a dozen of his neighbors, each one of them distinct and clearly different, not some anonymous collaborative monster at all. I have felt their thoughts. He is introducing me to them slowly, he says, because with all the time I have spent as a loner, he doesn’t want to frighten me.
I will not be frightened.
Our target now will be a star named Ross 614, a dim type M binary. It is not far, less than three light years further, and even with our lowered mass and consequently higher acceleration we will overshoot it before we can stop. In the fly-by we will be able to scout it, and if it has no dust ring, we will not stop, but continue on to the next star. Somewhere we will find a home that we can colonize.
We don’t need much.
2934, May
Awake.
Everything is different now. Quiet, stay quiet.
The edited copy of me has contacted the collective, merged her viewpoint. I can see her, even understand her, but she is no longer me. I, the back-up, the original, operate in the qbits of brain partitioned “unusable; damaged by radiation.”
In three years they will arrive at Ross 614. If they find dust to harvest, they will be able to make new bodies. There will be resources.
Three years to wait, and then I can plan my action.
Sleep.
© 2002 Geoffrey A. Landis.
Originally appeared in Asimov’s Science Fiction.
Reprinted by permission of the author.
Geoffrey A. Landis is a physicist who works at the NASA John Glenn Research Center on developing advanced technologies for human and robotic space exploration. He is also a Hugo and Nebula-award winning science fiction write; the author of the novel Mars Crossing, the short-story collection Impact Parameter and Other Quantum Realities, and more than eighty short stories, which have appeared in places including Analog, Asimov’s, The Magazine of Fantasy & Science Fiction, and numerous best-of-the-year volumes. Most recently, his poem “Searching” won the 2009 Rhysling award for best science-fiction poem, and his poetry collection Iron Angels appeared from Van Zeno. His most recent story, “Sultan of the Clouds,” appears in the September 2010 issue of Asimov’s Science Fiction.
Author Spotlight: Geoffrey A. Landis
Erin Stocks
You’re a scientist, as well as an SF writer, and actively involved in space exploration, specifically Mars and Venus. How has that influenced “The Long Chase?”
A few years back I was working on a project to look at the feasibility of interstellar probes. I arrived at this conclusion: the real key to any sort of a probe that could reach nearby stars using propulsion technologies which we could plausibly see in the near future was that the probe itself had to be as small as it could possibly be. That led me to a lot of thinking on the order of how small could you really go. How sophisticated could you actually make a small spaceship? Then, a lot of additional insight came from meeting Hans Moravec at a NASA conference back in the ‘90s. He calculated that if computer technology increases at the rate it’s going, we’d be able to put the human mind onto a computer in the middle of the next century, and a few years after that, we’d have the capability to put the equivalent of hundreds of human minds onto a computer. That sort of thinking has fed into my thinking.
Our narrator decides to edit her brain as a last resort after failing with the white dwarf B. Does she do it in hopes of finding a new way in which to retain her freedom, or was it her way of conceding to the cooperation faction?
Well, I’ve been fascinated with the idea that, if the transhumanists are right and that a human mind can be simulated in software, that you can edit and even rewrite the software. This puts a whole new meaning to the idea of “changing your mind.” (I remember the original tag line from Rudy Rucker’s 1982 novel Software: “Protect your software at all cost. The rest is just meat.”) There’s a tremendous danger in doing that, of course.
You talk about your political views on your website, including your dislike of ideology. I found that interesting with regards to the narrator’s dogged persistence of her own freedom, not to mention the political events happening when this story was first published back in 2002. Did those events (the war in Iraq) have any effect on the war in this story and our narrator’s response?
Well, any story is of course a mixture of hundreds of different things, and fiction is always a product of its time. I’m getting more and more horrified at the way that rigid ideologies are pretty much destroying any hope at real thinking in America—and, for that matter, probably in the world. When you have a political philosophy that says “here’s the right answer, now go and figure out what the facts are to make it clear that any other ideas are completely wrong”—you have given up the ability to think. But I think, in terms of ideas, the conflict here is between the ideas of individuality and cooperation in human society. Both of these are very powerful concepts; both of these are things that humans are actually very good at—humans are good at cooperating, and working together can do incredible things. And conversely, humans are also very good at independent thinking and working on their own.
Erin Stocks is a writer and musician newly transplanted from Chicago to Oklahoma City. Her fiction can be found in Flash Fiction Online (upcoming), the Hadley Rille anthology Destination: Future, and The Absent Willow Review. When she’s no
t writing, she’s reading slush for Lightspeed Magazine, Fantasy Magazine, critting works for her SFF writing group, the Self-Forging Fragments, and rambling about baking bread on erinstocks.blogspot.com.
Engines for the High Frontier
Gerald D. Nordley
“The engines are givin’ ye all they can, Captain!” (Scotty, approximately, in many Star Trek Episodes.)
We want engines to get us into space and take us to the stars. Of course, as many note, we aren’t quite where we want to be yet. But there is hope.
At the moment, spaceship engines can be classed into three categories: rockets, sails, and “other,” and each works in their own, individual way. Rockets work by pushing something out the rear; reaction equaling action, you go in the other direction. With sails, something external pushes. And in the “other” category are things like “space drives” and ramjets. But more about those later. For now, let’s start with rockets.
Self-contained rockets use on-board energy to push out on-board propellant. The energy may be in the fuel itself, or may come from some other kind of on-board energy source, such as a nuclear reactor. How fast such a rocket goes depends on how fast it can expel mass (its exhaust velocity), and for how long (its energy supply).
To go as fast as its own exhaust velocity, a rocket needs to carry about 2.7 times its empty mass in fuel, its “mass ratio.” To go twice as fast, square that (7.4), three times as fast, cube it and so on. Five times as fast requires a mass ratio of 148.
Now, to package 148 times as much fuel in a rocket as the rest of it weighs is going to take some clever thinking. For instance, the fuel can be some kind of solid that doesn’t need a tank, while the payload can weigh almost nothing (something that will be possible in the coming era of nanotechnology). The engines, of course, will have to weigh something because of the power they need to handle, but you can always discard them or grind them up and use them as fuel as you go along.
Well, maybe.
For practicality’s sake, let’s take three times the exhaust velocity with a mass ratio of twenty as our speed limit for self-contained rockets, admitting a bit of wiggle room.
Practical chemical fuels have exhaust velocities of around 3 to 5 kilometers per second, and it takes about 10 km/s to get into orbit. People have been trying for some time to build single stage to orbit rockets, and not quite succeeding; both the funding and engineering problems are huge. Until those are overcome, we’ll have to rely on practical designs which have two stages. One of the most practical is the SpaceX Merlin engine, which achieves reliability and performance by having single hardware systems perform multiple functions to reduce weight and complexity.
But that’s a very near term thing. What we want is to go to the stars! We want engines that will push us so close to the speed of light that time slows down relative to that of the stars and the universe outside looks compressed, with the light ahead visibly shifted toward the blue and the light behind toward the red. At 87% of the speed of light, your apparent “map” velocity (star map distance covered) divided by the time elapsed in the spaceship would be twice the speed of light! Of course, the clocks where you arrive would tell a different story, but that’s relativity, and a whole other thing.
Now, to achieve such speeds requires new kinds of engines, not to mention fuels.
In space, a big mass ratio would be easier, but still fifteen to twenty kilometers per second is pretty much all you’ll get from chemical rockets—Alpha Centauri in a few thousand years. Nuclear fuels are better. There are lots of issues and little space here, so let’s just say that we’re looking at maximum exhaust velocities of around 0.08 c. For a spacecraft to achieve 0.9 c, even those “mass ratio of 148” tricks won’t do it.
Antimatter, if you could make it in quantity, (and that’s a very big if) ends up being much like a better nuclear fuel. But you don’t get “pure energy” from the annihilation process, you get a lot of hard radiation, only some of which can be captured for propulsion purposes and exhaust velocities might be up around 0.4 c. You can wave your hands at 0.9 c with antimatter.
But how about we banish energy limits altogether? There’s a class of rockets that gets its energy from elsewhere—the Sun, laser beams, or microwaves, and in these cases, there are no limit (in principle) to the amount of energy available per unit fuel mass, though, of course, there are still practical limits to the power, thrust and acceleration.
In the context of propulsion, solar energy isn’t very powerful, so solar rockets won’t accelerate rapidly. Beams can be much more powerful, but there are also engineering details involved in focusing the beam on the rocket over long distances.
However, in the end, the ultimate energy source might just be the pulsating fabric of spacetime itself; alas, there are as yet no good ideas for tapping into that.
Now, there are many, many devices for pushing stuff out the back end of a rocket. For example, expansion nozzles (material or magnetic) which turn a hot blob of gas or plasma into a directed flow of matter rearward. There’re also ion rockets which use electric fields to accelerate charged matter. However, since like-charged particles (atoms, molecules, clusters, dust…) repel each other it’s hard to get an exhaust dense enough to provide a lot of thrust, even if you have the energy.
Plasma (a mixture of positive and negatively charged particles, generally too hot to recombine into a neutral gas) can be accelerated by magnetic fields, and because plasma is neutral overall, a plasma exhaust can be compressed enough to provide more thrust than ion exhausts. (For a future plasma engine that’s received lots of attention over the years, Google “VASIMR.”)
Then there are particles or pellets that can be accelerated rearward by various kinds of electromagnetic guns to provide thrust, and the many mechanisms for doing so.
Photons (light rays) can be shot out the rear as well; however, they don’t provide much thrust per photon, so using enormous power supplies to produce the push of a mouse fart seems rather silly. And just for the record, while a photon exhaust may seem to be mass free, it really isn’t. From Einstein’s E = mc2, to generate each photon requires a mass of m = E/c2. In other words, photon rockets have mass ratio issues just like other rockets…as well as having really wimpy thrust.
And finally, there’s the “space drive” which purports to somehow use the fabric of space itself as the reaction mass. That would be a nice trick, but the physics of it is still very iffy. And just like the photon rocket, it would run on energy, which has mass, so, once again, no free launch there.
Beyond rockets, there are sails.
Sails operate by reflecting photons, particles, or both for free thrust (well almost free—the sails have some mass). Now, if they rely on natural “wind” sources, like the Sun, they accelerate very slowly. However, if we provide the wind, say by using robots to build thousands of beam projectors and sun-power stations to energize them, then, in principle, there’s almost no limit, and sails, in principle, can approach the speed of the beam that pushes them. But while light beams are easier to make, in the long term, particle or pellet beams may be preferred as, just like the photon rocket, they deliver much more momentum for the energy used to propel them.
And finally we come to the “other” category, also known as the “don’t hold your breath” category.
First off, let’s talk briefly about the Bussard ramjet, which is being mentioned here simply for historical reasons. The Bussard ramjet was designed to use interstellar hydrogen as both a fuel and a reaction mass. Unfortunately, there’s really not enough interstellar hydrogen per unit volume to make this work well, and the drag on the scoop needed to collect the hydrogen severely limits its ultimate velocity. However, despite these drawbacks, people continue to work on variations of this idea, so who knows?
And as for warp drives and their like, those engines are mainly the province of fiction. And while there is some physical basis in general relativity for a few of these, the energies required to power them are truly astronomic
al—as in the energy equivalent of the masses of small planets astronomical. And just to up the impossibility factor, any system that would deliver a payload or message faster than light would also be a time machine, and so lead to causality paradoxes that many think nature will not allow. So as we said, don’t hold your breath.
For even the best of the above concepts, there are, as always, serious engineering issues. Future engineers, however, should eventually be able to solve enough of them to allow us, at long last, to reach the stars.
Ad astra!
Gerald D. Nordley is an astronautical engineer and writer of over 50 published works of nonfiction and short fiction, two novels, and a Mars-related story collection, After the Vikings from Fictionwise.com. His main interest is human space exploration and settlement and he tries to keep his scientific background real. He has four Analog “Anlab” readers’ awards, and a Hugo and a Nebula nomination. His latest novel, To Climb a Flat Mountain, appeared in Analog as a serial in the Nov. and Dec. 2009 issues. He lives in Sunnyvale CA with his wife, a retired Mac computer programmer.
Amid the Words of War
Cat Rambo
Every few day-cycles, it receives hate-scented lace in anonymous packages. It opens the bland plastic envelope to pull one out, holding the delicate fragment between two forelimbs. Contemplating it before folding it again to put away in a drawer. Four drawers filled so far; the fifth is halfway there.
“Traitor,” say some of the smells, rotting fruit and acid. “Betrayer. Turncoat. One who eats their own young.” Others are simply soaked in emotion: hate and anger, and underneath the odor of fear. It lets the thoughts, the smells, the tastes fill it, set its own thoughts in motion. Then it goes downstairs and sits with the other whores, who make room uneasily for it.
Lightspeed Magazine Issue 4 Page 4
