Galaxy's Edge Magazine: Issue 2: May 2013
Page 20
Typically in such regimes, one can still amass wealth, just by owning things. To avoid state controls and taxes, barter returns—presto, we’re back in the Middle Ages.
Money isn’t the object of people’s lives, it’s just how we keep score. Money measures economic matters. Without it, we can’t see what works and what doesn’t.
Few in sf ever go beyond this simple truth. Certainly Trek seems oblivious to it.
Granted, there are still too many future societies where one doesn’t even get to see how the plumbing works, let alone the economy. However odd the future will be, it surely won’t be a repeat; economics evolves. The leftish space operas of recent years have plenty of quantum computers and big, Doc Smith-style planet-smashing weaponry, but the hard bits of real economics they swerve around. Maybe because they haven’t any real answers, or aren’t interested. Opera isn’t realism.
Though New Wave sf had a leftist tinge, it had no real political/economic agenda. The common association of hard sf with libertarian ideas, on the other hand, may have sprung from a root world view. Science values the primacy of the individual mind, which can do an experiment (thought experiments, as with Einstein, or real ones) to check any prevailing theory.
This heroic model lies deep in Western culture. Individual truth and a respect for facts is the fulcrum of libertarian theory. Of course, anarchist societies (not socialist), as in Ursula LeGuin’s The Dispossessed, can depict the struggle of the lone physicist against the collective, received wisdom. But The Dispossessed’s logic is not about economics—it is a deeply felt story about a single man’s sacrifice and discovery. The social satires of Pohl and Kornbluth have more bite, and probably more useful truth for today. The Space Merchants by its title foretells much we may learn from.
I speak first of economics because it is something of a science, with its own Nobel Prize, and it influences the science of space—real space, not the sf operas—quite crucially. In the end, the accountants want to know who is going to pay for all this, and why.
What possible economic motive could a space-faring society have?
Mining the Sky
Motives answer needs.
Within a century we are going to start running out of two essentials: metals and energy. Within about 50 years most of our oil reserves will be gone—farewell, SUVs! The Middle East will cease to be a crucial tinderbox, simply because countries there will be poor and doomed. Most policy makers know this but seldom speak of it in public—half a century is unimaginably long for a politician.
I will deal with the vast problems of energy supply in my next column. Less well recognized is that many metal ore deposits in the crust of the earth will be mined out within a century. Of course, substitute materials can be and have been found. But some are crucial and to substitute something else changes the world for the worse.
My favorite example of this is oysters. In Dickens novels you can read of poor people forced to eat oysters, then a cheap, easily found, but somewhat lower-class food, while the rich ate beef Wellington. Now we gobble down McDonald’s burgers and oysters are a fancy appetizer. Sure, we’re well fed—but I prefer oysters, which as a boy I ate for breakfast in my fisherman family, little appreciating my luxury.
Technology can help us greatly in the uplifting of humanity—the great task confronting us. A century ago, aluminum was a rare metal more costly than silver; now we toss it away in soft drink cans—then recycle it. But inevitably the poor nations’ growing demand will overburden our demand on the Earth’s crust and we will surely run short of the simplest metals, even iron.
As it turns out, both metals and energy are available in space in quantities that we will desperately need.
We also need a clean environment. Mining for metals comes second to fossil fuel extraction in its environmental polluting impact. Coal slag is the #1 water pollutant in the U.S., with runoff from iron mines the second.
Detailed analysis shows that metals brought from the asteroids will be competitive with dwindling Earthly supplies. Better, by refining them in space, we prevent pollution, particularly of another scarce resource—water.
There is money to be made in that sky. An ordinary metal-rich asteroid a kilometer in diameter has high-quality nickel, cobalt, platinum and iron. The platinum-group metals alone would be worth $150 billion on Earth at present prices. Separating out these metals takes simple chemistry done every day in Earthly refineries, using carbon and oxygen compounds for the processing steps. Such an asteroid has plenty carbon and oxygen, so the refining could be done while we slowly tug it toward a very high Earth orbit—a task taking decades.
Steam Rockets
Crucial in all this is the shipping cost, so attention focuses on how to move big masses through the deep sky.
Certainly not with chemical rockets, which have nearly outlived their role in deep space.
Liquid hydrogen and oxygen meet in the reaction chambers of our big rockets, expelling steam at about 4.1 km/sec speeds. That is the best chemical rockets can do, yet to get to low Earth orbit demands a velocity change of about 9 km/sec—over twice what the best rockets can provide without paying the price of hauling lots of added fuel to high altitude, before burning it. This means a 100-ton launch vehicle will deliver only about 8 tons to orbit—the rest goes to fuel and superstructure.
Moving around the inner solar system, which takes a total velocity change of 20 or 30 km/sec, is thus a very big deal. Current systems can throw only a few percent of their total mass from ground to Mars, for example. Big velocity changes (“delta-V” in NASAspeak) of large masses lies far beyond any chemical method. To get from Earth to the biggest asteroid, Ceres, takes a delta-V of 18.6 km/sec, which means the payload would comprise only half of one percent of the vehicle mass.
Using chemical rockets to carry people or cargo anywhere in deep space was like the Europeans discovering and exploring North America using birch bark canoes—theoretically possible, but after all, the Indians did not try it in reverse, for good reason.
For thirty years NASA ignored the technology that can answer these challenges. In the late 1960s both the US and the USSR developed and ran nuclear rockets for hundreds of hours. These achieved double the exhaust velocity of the best chemical rockets, in the 9 km/sec range. These rockets pump ultra-cold liquid hydrogen past an array of ceramic plates, all glowing hot from the decay of radioactive fuel embedded within. The plume does not carry significant radioactivity.
Those early programs were shut down by nuclear-limiting treaties, appropriate for the Cold War but now out of date. We will need that technology to venture further into space. NASA has gingerly begun building more of the nuclear-electrical generators they ran many missions with, including the Voyagers (still running after over a quarter of a century, and twice as far away as is Pluto) and the Viking landers on Mars. These are simple devices powered by the decay of two pounds of plutonium dioxide, yielding 250 watts of heat. Indeed, simply heating spacecraft in the chill of space is the everyday use for small radioactive pellets, which were embedded into every spacecraft headed outward from Earth orbit.
Even this tentative step back to the past seems to acutely embarrass NASA. They elaborately describe how safe the technologies are, because we live in a Chicken Little age, spooked by tiny risks.
Far bigger accidents have already happened. Four large nuclear reactors have fallen from orbit, none has caused any distribution of radioactive debris. In fact, a Soviet reactor plunged into the Canadian woods and emitted so little radioactivity we could never find it. Embedded in tough ceramic nuggets, the plutonium cannot be powdered and inhaled.
Beyond this return to our past capabilities, NASA is considering building a nuclear-driven ion rocket. This will yield exhaust velocities (jetting pure hydrogen) of 250 km/s—a great improvement. But the total thrust of these is small, suitable only for long missions and light payloads.
Using hydrogen as fuel maximizes exhaust velocity (for a given temperature, lighter molecules mov
e faster). And we can get hydrogen from water, wherever it can be found. We’ve discovered from our Mars orbiters that Mars has plenty of ice within meters of the surface. Comets, the Jovian ice moons—all are potential refueling stations.
But holding hydrogen at liquid temperatures demands heavy technology and careful handling. Water is easier to pump, but provides only a third the exhaust velocity. Many believe that ease of handling will drive our expansion into space to use not more exotic fuels, but plain old… water.
Living Off the Land
What could our space program be like right now, if we hadn’t shut down the nuclear program? The road not taken could already have led us to the planets.
The key to the solar system may well be nuclear rockets—nukes to friend and foe alike. The very idea of them had of course suffered decades of oblivion, from the early 1970s until the early days of the 21st century. Uranium and plutonium carry over ten thousand times as much energy per gram as do chemical rockets, such as liquid hydrogen burning liquid oxygen.
So in the end, advanced rockets may well be steam rockets, all the way from the launch pad to Pluto. Chemical boosters can get a nuke rocket into orbit, where it turns on. Whether with liquid hydrogen married to liquid oxygen, or with water passing by slabs of hot plutonium, they all flash into plumes of steam.
Real space commerce demands high energy efficiency. Realization of this returned to NASA in 2002, with the hesitant first steps of its nuclear Project Prometheus (bureaucracy loves resplendent names).
The first rush of heavy Mars exploration will probably prove the essential principle: refuel at the destination. Live off the land. Don’t haul reaction mass with you. Nuclear rockets are far easier to refuel because they need only water—easy to pump, and easy to find, if you pick the right destination. Nearly all the inner solar system is dry as a bone, or drier. If ordinary sidewalk concrete were on the moon, it would be mined for its water, because everything around it would be far drier.
Mars is another story. It bears out the general rule that the lighter elements were blown outward by the radiation pressure of the early, hot sun, soon after its birth. This dried the worlds forming nearby, and wettened those further out—principally the gas giants, whose thick atmospheres churn with ices and gases. Mars has recently proved to be wet beneath its ultraviolet-blasted surface. Without much atmosphere, its crust has been sucked dry by the near-vacuum. Beneath the crust are thick slabs of ice, and at the poles lie snow and even glaciers. So explorers there could readily refuel by melting the buried ice and pumping it into their tanks.
The moons of Jupiter and the other gas giants are similar gas stations, though they orbit far down into the gravitational well of those massive worlds, requiring big delta-V to reach. Pluto, though, is a surprisingly easy mission destination. Small, deeply cold, with a large ice moon like a younger twin, it is far away but reachable with a smaller delta-V.
Of course, there are more sophisticated ways to use water. One could run electricity through it and break off the oxygen, saving it to breathe, and then chill the hydrogen into liquid fuel. That would be the most efficient fuel of all for a nuclear rocket.
But the equipment to keep hydrogen liquefied is bulky and prone to error—imagine the problems of pumps that have to operate in deep space at 200 degrees below zero, over periods of years. An easier method would be to use that hydrogen to combine with the Martian atmosphere, which is mostly CO2, carbon dioxide. Together they make oxygen and methane, CH4, both easy to store. Burning them together in a nozzle gives a fairly high-efficiency chemical rocket. A utility reactor on Mars could provide the substantial power needed for this.
Still, that would demand an infrastructure at both ends of the route. Genuine exploration—say, a mission to explore the deep oceans of Jupiter’s moon Europa—would need to carry a large nuclear reactor for propulsion and power, gathering its reaction mass from the icy worlds.
NASA is studying an expedition to Europa using a nuclear-driven ion rocket, which would carry its own fuel. It will have to fire steadily for seven years to get to Europa, land and begin sending out rovers. Testing the reliability of such a long-lived propulsion scheme demands decades of work, effectively putting off the mission until the 2020s.
Far better would be a true nuclear fission rocket throwing hot gas out the back. If it could melt surface ice on Europa and tank up with water, it could then fly samples back to us.
The true use of a big nuclear reactor opens far more ambitious missions. The real job of studying that deep ocean is boring through the ice layer, which is quite possibly miles thick, and maybe even hundreds of miles. No conceivable drill could do it. But simple hot water could, if piped down and kept running, slowly opening a bore hole. Hot water has been tried in Antarctica and it works.
To test for life on Europa would demand that we send a deep-sea-style submarine into those dark, chilly waters. To power it we could play out a thick, tough power cord, just as do the undersea robot explorers that now nose about in the hulks of the Titanic and the Bismarck—power cord tens of kilometers long. Only nuclear can provide such vast powers in space.
Dreadnoughts of Space
Space is big. Moving asteroids and other large masses demands scale. This leads to a future using big nukes.
The payload would be a pod sitting atop a big fuel tank, loaded probably with ordinary water, which in turn would feed into the reactor. Of course, for manned flights the parts have to line up that way, because the water in the tank shields the crew from the reactor and from the plasma plume in the magnetic nozzle. To even see the plume, and diagnose it, they will need a rearview mirror floating out to the side. The whole stack will run most of its trajectory in zero-G, when the rocket is off and the reactor provides onboard power.
A top thick disk would spin to create centrifugal gravity, so the crew could choose what fractional G they would wish to live in. Perhaps forty meters in diameter, looking like an angel food cake, it would spin lazily around. The outer walls would be meter-thick and filled with water for radiation shielding. Nobody could eyeball the outside except through electronic feeds.
Plausible early designs envision a ship a hundred meters long, riding a blue-white flare that stretches back ten kilometers before fraying into steamy streamers. Plasma fumes and blares along the exhaust length, ions and electrons finding each other at last and reuniting into atoms, spitting out a harsh glare. This blue pencil points dead astern, so bright that, leaving Earth orbit, it could be seen from the ground by naked eye.
Ordinary fission nuclear power plants are quite good at generating electrical power but they are starved for the neutrons that slam into nuclei and break them down. That is why power reactors are regulated by pulling carbon rods in and out of the “pile” of fissionable elements—the carbon can absorb neutrons, cooling the whole ensemble and preventing overheating.
The next big revolution in nukes would then come with the invention of practical thermonuclear fusion machines.
Fusion slams light nuclei like hydrogen or helium together, also yielding energy, as in the hydrogen bomb. Unlike fission, fusion is rich in hot particles but has trouble making much energy.
Most spaceflight engineers have paid little attention to fusion, believing—as the skeptics have said for half a century—that controlled fusion power plants lie twenty years ahead, and always will. Fusion has to hold hot plasma in magnetic bottles, because ordinary materials cannot take the punishment. The most successful bottle is a magnetic doughnut, most prominently the Russian-inspired Tokamak.
To make it into a rocket, let the doughnut collapse. Fusion rockets are the opposite of fusion electric power plants—they work by letting confinement fail. Ions fly out. Repeat, by building the doughnut and starting the reaction again.
The rocket engine core is this come-and-go doughnut, holding the plasma, then letting it escape down a magnetic gullet that shapes the plasma into a jet out the back. Rather than straining to confine the fusing, burning plasma,
as our so-far-unsuccessful power plant designs do, a rocket could just relax the magnetic bottle.
So these fusion nukes are a wholly different sort of vehicle. They can promise far higher exhaust velocities than the fission nukes.
Leaving high Earth orbit, such ships will not ignite their fusion drives until they are well outside the Van Allen belts, the magnetic zones where particles are trapped—or otherwise the spray of plasma would short out innumerable communications and scientific satellites ringing the Earth. (This actually happened in 1962, when the USA project Starfish Prime set off a hydrogen bomb in the Van Allen belts. People have trouble believing anybody ever did this, but those were different days, indeed. The ions and electrons built up charge on our communications satellites, most of which belonged to the Department of Defense, and electrically shorted them out. Presto, billions of dollars lost in surveillance satellites gone dead within the first hour. A colossal embarrassment, never repeated.)
The Long Prospect
So will we have a space operatic future? If that means huge spacecraft driven by spectacular engines, maybe so. Interstellar flight lies beyond the technologically foreseeable, alas.
But the rest of the space opera agenda depends on your political prognostications. Will Iain Banks’s anarchist/socialist empire arise from remorseless economic forces? Or perhaps Robert Heinlein’s libertarian frontier?
Currently we’re “developing” space mostly with tax dollars that go into hugely inefficient projects like the International Space Station, which does very little research. We now pay the Russians to deliver our crews and Elon Musk’s SpaceX to deliver freight. What we need is Ad Astra, Contra Bureaucratica. The private opening of space will drive forward now, as low-orbit tourism and the first efforts to carry out repair and resource gathering like asteroid mining, at much greater distances. Still, this is a mere toe in the ocean.
Humanity’s current dilemma is exploding populations amid, and versus, environmental decay and dwindling resources. Of course we’ve dodged most of the bullets, thanks to the engineers and scientists. But we cannot count on them forever to solve our social problems.