"Worlds For Man - Sol"
(c) 2007, 2011 by Jordan S. Bassior
This is an overview of the colonization and economic potential of the Solar System. In general when I talk about "Near Term" possibilities I am referring to throroughly known engineering; "Middle Term" assumes the possibility of considerable engineering progress and some scientific progress; and "Long Term" of vast engineering progress and major scientific progress. Obviously, the longer the term, the greater the speculation involved.
I considered doing it in terms of the rough time frames, but realized that I have no good way to predict the speed of scientific and technological progress. If you believe the most fervent advocates of The Singularity, we might get to "Long Term" levels of progress by 2050 or so; otherwise, I would imagine it would take many centuries.
I'm doing the system from the inside out.
We normally don't think of the Sun when we think of space colonization, but it does contain some 99% of all the mass in the Solar System. Of course, it's hardly an inviting environment: at its surface the temperature is 5500 K, high enough to vaporize any substance we know how to make. This temperature climbs to 13.6 million degrees Kelvin in the core, enough to fuse hydrogen, which is exactly what happens, and what produces most of the Sun's energy (the rest being produced by gravitational pressure).
The Near Term exploitation of the Sun, therefore, centers not around colonization but around energy extraction. The vast majority of the Sun's energy, of course, is wasted from our point of view, because it is merely emitted into space without striking the Earth or any other worlds in our system. So the first thing we might do would be to intercept that energy and convert it into a usable form.
A solar panel in orbit at 1 AU (the Earth's orbital distance) from the Sun will receive 1.366 kilowatts per square meter of energy. If it were at orbit at 0.5 AU it would thus receive 1.866 kilowatts per square meter; at 0.25 AU almost 3.5 kilowatts per square meter, and so on (following the Inverse Square law for radiation).
Therefore, it follows that if we had a mature interplanetary transport capability, it would make sense to station our solar energy panels as close to the Sun as possible. There are, of course, tradeoffs: the closer the panel is placed to the Sun, the greater the drift imparted by radiation pressure and the more heat it must dissipate. These are both serious issues, as the former complicates the task of beaming power to the receiving-stations, and the latter risks loss of one's collectors.
Getting the energy back to the Earth or other inhabited places is in principle easy: one would connect the solar panels to a maser emitter, and beam the energy as microwaves to a receiver near where the energy was to be employed. The details of such systems have been long explored in both science and science fiction: basically, one uses the reflection from the transmission to keep the beam on track and safely shut the beam off should it wander off-target.
Such an endeavor, once begun, would be highly-profitable, making it a practical project for any civilization which has reached the point of routinely sending at least robotic devices to the vicinity of Mercury, the planet most logical as a source of mass for the project. Obviously, placing a crewed station on Mercury itself would be the easiest way to manage the mining operations. More on this in the next installment.
In the Middle Term, our engineering and our materials science might advance, enabling the solar panels to be placed closer and closer to the Sun. If we developed a really good energy absorption and retransmission system, this might work as a cooling device for a spacecraft, enabling manned exploration of the corona and unmanned exploration of the deep photosphere.
One exciting idea would be the remote manipulation of Solar substance by means of powerful electromagnetic fields. Such fields might be externally generated, or might be used as catalysts to reshape the exceedingly powerful electromagnetic fields which the Sun generates naturally. This might enable the direct mining of the Sun for matter (mostly hydrogen and helium, but truly vast quantities of both, and even the heavy elements become significant when you filter enough Solar matter). Another application might be the generation of extremely powerful energy beams ("Doc" Smith's "sunbeams"), for military or engineering purposes.
In the Long Term, we might develop materials science (possibly employing generated force fields, or exotic matters) to the point where we could maintain organized structures at the immense pressures and temperatures inside the Sun. This would enable actual colonization of the Sun itself, though probably not by organic life forms: such writers as Arthur C. Clarke, Stephen Baxter, and John C. Wright have imagined these sorts of operations. Among the purposes might be colonization (by greatly-modified or uploaded humans in the form of exotic-mater machines) or the formation and extraction of exotic forms of matter creatable only under the extreme conditions prevailing within a star. Another aim might be the direct management of the Solar power cycle, to a variety of possible ends.