© 1975-1979, 2008 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm

19.2.3  Planet Moving and Star Mining

We are still thinking small, unfortunately.* We have not yet mentioned a single engineering project that could not be successfully mounted by a Type I planetary culture, at least in theory. A Type II society living in the space surrounding its sun will be a proud, vigorous, expansive large-scale civilization. They will have magnificent dreams, and their technology will not lag far behind their ambition.

A stellar culture will have access to the entire mass and derivable energy from all the matter in its own solar system. From Table 19.1 we have already seen that this represents considerable potential for energetic economic development of interplanetary space. Theoretically, a stellar society has at least 10³⁰ kilograms and more than 10⁴³ joules to play around with.

How grand may be their monuments to civilization? As even terrestrial engineers are well aware, any construction project has two basic requirements: (1) Delivery of materials to the construction site, and (2) proper deployment of those materials once they have arrived. So what can Type II cultures do?

While the technology needed to move planets and stars around is absolutely huge when measured against the normal human scale, the energy requirements for such operations turn out to be well within reach of Type II civilizations. Table 19.3 below shows the energies necessary to move several different kinds of bodies. Values are given both for solar escape velocity (~10⁴ meter/sec) and for the minimum reasonable interstellar transport velocity (1%c).

Clearly, asteroid and planet-moving are no real problem. The interstellar transport of stars will give Type II societies some trouble, and it make take a Type III organization to perform the maneuver gracefully.

Darol Froman, Technical Associate Director of the Los Alamos Scientific Laboratory in New Mexico, has pointed out that the complete fusion combustion of all the deuterium in Earth's oceans would be insufficient to impart solar escape velocity to the planet.²⁸³¹ If the hotter-burning hydrogen fusion reactions are used, however, Earth's seas could be drained and used as fuel to propel our world to the stars.

Froman suggests that roughly a quarter of the fuel be used to escape from Sol, another quarter to enter the target stellar system many light-years away, and the remaining half for heat, lighting, and propulsion en route. The planetary fusion thrusters should be located at the South Pole, so that Earth's natural rotation can be used for guidance and directional stabilization. Science fiction writer Stanley Schmidt has done a creditable job in describing the local effects of terramotive operations.²⁸³²

How might gas giants be pushed around the solar system? We know Type II societies have the energy, but what kind of technology might be involved? In one of his science fiction tales of the distant future, Larry Niven describes how it might be possible to use what he calls a Fusion Pogo Rocket. A tremendous fusion motor hooked up to a reworked military laser cannon might turn the trick on our Uranus:

It's a double-walled tube, very strong under expansion shock. It floats vertical in the upper air. Vents at the bottom let in the air, which is hydrogen and methane and ammonia, hydrogen compounds, like the air that the sun burns. You fire laser cannon up along the axis, using a color hydrogen won‘t let through. You get a fusion explosion along the axis, and the explosion goes out and up. The whole mass blasts out the top, through the flared end. It has to have an exhaust velocity way higher than Uranus's escape velocity. The motor goes smashing down into deeper air. You see there's a kind of flared skirt at the bottom. The deep air builds up there at terrific pressure, stops the tube and blasts it back up. You fire it again... The atmosphere is fuel and shock absorber both -- and the planet is mostly atmosphere.²⁶³⁶

Stars, too, may be moved about, using a tuned Shklovskii Mining Graser (see below) at reduced power. This powerful gamma-ray laser could be aimed to strike a glancing blow at the target star on the side opposite the direction you want it to move. The sun will spew out star-stuff and begin to move off in the direction dictated by Newton's laws of motion. Scientists agree that this technique may work, because the same basic principle of propulsion has been observed to occur naturally with comets. These “dirty snowballs,“ swinging close to our Sol, are heated on the sunward side. Material boils off asymnietrically and jets out into space, deflecting the orbit by a kind of rocket effect.**

So delivery of the materials to the construction site is no problem for stellar cultures. What about deployment? Once a planet or star has been moved to where it is needed, how do we get the mass out?

One of the most popular techniques for taking planets apart is called centrifugal disruption. This requires the accelerated rotation of a planet up to the point at which it fractures under internal stresses. Slowly the world unravels, sloughing off outer layers like a successive molting. If the speed-up is continued long enough, the entire body will be disrupted into asteroid-sized chunks of mass.

Freeman Dyson has suggested that centrifugal disruption could be accomplished by laying a net of conductive windings around a planet along the lines of latitude, each strand carrying a current on the order of microamperes per square centimeter.¹⁴⁵⁰ These cables would give rise to a magnetic field. Orbiting electrical generators (which produce an opposing magnetic field) then trace out paths which produce a net torque on the body, causing it to spin faster. A continuous stream of generators must pass through the correct maneuvers to maintain the electromagnetic accelerative force, each unit converting its orbital momentum into planetary spin momentum. An alternative disruption technique is available to civilizations that have mastered fusion power -- simple tangential reaction thrust generated by sideways-firing equatorial fusion rockets would also spin up a world to destruction.²⁸³³

When the rotation rate of a planet the size of Earth has been brought up to about 100 minutes per revolution, says Dyson, “the equator is just ready to take off into space. From this point on, the process of disassembling the planet will proceed steadily as its angular momentum is increased.“ The total energy required to spin Earth up to the transition point is about 4 x 10³⁰ joules; for Jupiter, about 9 x 10³⁴ joules will be necessary. (After 97% of Jupiter's mass has been stripped away, we are left with a large terrestrial world that was once the core of the jovian -- a mass of from 5-10 Earth-masses. We may decide to cannibalize it for heavy metals, or it may be saved for reasons of aesthetics, nostalgia, or terraforming and habitation operations.)

J.H. Fremlin and Anthony Michaelis have suggested that gas giants could be disassembled bit by bit.²⁹⁵⁵ Suborbital fusion satellites and nuclear ram-scoops could dip down into the jovian atmosphere, scoop up some hydrogen, fuse it into heavier elements, and use the resulting energy to propel the transmuted matter into a parking orbit near the construction site. The energy needed to move Jupiter's entire mass into an Earth parking orbit along a minimum energy transfer trajectory is about 10³⁶ joules.

Still a third possibility is Explosive Disruption. Theoretically, with enough energy under harness any planetary body can quite literally be blasted into rubble. While we don‘t know what kind of explosive device might be used (perhaps a 6-km-wide antimatter asteroid?), it is a simple matter to calculate how much energy would be required. The total energy to disrupt a world expIosively is on the order of its gravitational potential energy. This works out to about 2 x 10³² joules for Earth and 2 x 10³⁶ joules for Jupiter. Again, no problem at all for Type II cultures.

In a related manner, stars too may be disassembled. The energy required to blow a sun to bits by brute force explosive disruption is about 2 x 10⁴¹ joules, which would be quite a challenge for an enterprising stellar society. But this is not very elegant. The renowned Soviet astrophysicist Iosef S. Shklovskii has considered the possibility that an artificial supernova might be induced in a single star.²⁰ Shklovskii believes that a Type II civilization should have no difficulty constructing a gigantic gamma-ray laser (or “graser“) operating at a wavelength of 1 Angstrom and at power levels of at least 10¹⁵ watts. This Mining Graser (Figure 19.2) would have a forward aperture diameter of about 10 meters and could focus on a 10-km-wide spot at a star's surface from a safe distance of 10 light-years. (Unmanned automated devices can venture closer.) The Mining Graser will probably be “self-critical“ -- that is, an enormous nuclear reactor that emits most of its laser energy directly as coherent light.²⁸⁴)

Figure 19.2 The Shklovskii Mining Graser

BELOW: the graser beam is cranked up to maximum power and directed straight at the star. The remnants of the resulting supernovae might appear as the Crab Nebula does in this photograph.

According to an astrophysical theory proposed by British astronomer Geoffrey Burbidge, a concentrated gamma-ray flux should cause exceedingly high temperatures to arise in the outer layers of a star. If this temperature was hot enough, a spontaneous supernova might result. It is estimated that a flux of 10⁷ watts/m² may be sufficient to initiate a supernova explosion.²⁸³⁷

When this occurred, perhaps 0.1% of the star's mass would be converted directly into energy -- about 10⁴³ joules. In addition to the release of copious amounts of x-rays and other radiative energy that could be collected and stored, a significant fraction of the stellar mass will be propelled outward at speeds up to 1000 km/sec. This rich expanding gas cloud may be harvested by diligent interstellar mining engineers, using squadrons of robot drones equipped with giant electromagnetic ramscoops. Heavy elements generated by the explosion would be swept up, refined and milled by a flotilla of gargantuan factory sweepships in a "cage" of circular orbits surrounding the demolished star.

The Shklovskii Mining Graser can also be used to turn stars off. The beam strikes a glancing blow first on one side, then the other, and so forth. Star-stuff spews equally from either side, so the sun goes nowhere. Sweepships collect and store the unburned stellar hydrogen as it streams from the photo-sphere. Slowly the star is whittled down to size as the bulk of its mass is siphoned off and taken away. Finally, down to less than 1% of its original weight, the once-mighty celestial furnace flickers out. The hot jovian planet that remains may now be disassembled by the more conventional means discussed earlier.

* A sobering example of this appears in Isaac Asimov's Foundation Trilogy.²⁹⁴⁴ Trantor, the Imperial capitol of all the Galaxy, is described as a giant ecumenopolis, a “planetary city“ of gleaming metal covering 190 million km² (about the surface area of Mars) and extending nearly 2 km deep. There are 40 billion human bureaucratic inhabitants. This seems a rather impressive piece of architecture, especially since each person would have a generous 10⁷ m³ all to himself which is at least two orders of magnitude more room than most people have on Earth today. But the mass and energy requirements are far less impressive. If made of steel the total mass of the city of Trantor would come to about 10¹⁹ kg. Only a million average-sized asteroids need be captured for this purpose, and only about 10²⁶ joules would be required to transfer them to the site of construction -- say, Earth orbit. (This is the major energy cost of the project.) So mighty Trantor, pride of the Galactic Imperium and capitol world of the entire Milky Way, could be constructed with some difficulty by a mature Type I civilization or with ease by a Type II civilization.

** Galaxy-moving should be possible for Type III civilizations using a related technique. Synchronized application of the Graser to a few percent of the stars in a galaxy would cause billions of suns to move off in the preferred direction. The rest of the galaxy, bound to the moving stars by gravity, would slowly follow.

Last updated on 6 December 2008