|Mars, with one of the Aldrin Cyclers approaching|
The Black Desert is a romantic term, coined by the expatriate artist on Mars and used in literary works by the same. The term itself comes from the closest translation of the Native Martian term for space in general. In human lingo, it specifically refers to the asteroid colonies that are not orbiting either Terra or Mars. It does not cover those planets, nor does the term cover the colonies and outposts of the Dyson Federation that exist around Venus and Mercury.
At the core of the Black Desert are the Cyclers. The Aldrin Cyclers are the oldest, cheapest, and most reliable way to travel from Terra to Mars. Thanks to the Oberth Effect, the costs of maintaining the Cycler's orbit is so low that it is subsumed into the costs of the life-support for the travelers on the Cyclers during the six-month trip between worlds. That's what makes this type of travel so attractive; the Cyclers are going to go to Mars no matter what, so getting to the Red Planet is simply a matter of hitching a ride.
But what is a Cycler, exactly? Theoretically, it could be any type of spacecraft. Buzz himself currently favors using space stations, and I'm sure that's where Cyclers will start. Sometime in the 22nd Century, entire asteroids began to be moved into the Aldrin Orbits and permanent outposts set up in space. The reasons for this are economical; technological advances made such a massive undertaking more cost-effective than worrying about maintaining conventional spacecraft.
This may sound far-fetched, but the advent of stable fusion reactors makes this kind of statement possible. With what is for all intents and purposes unlimited power, magnetic sails like Robert Zubrin proposed, were used to move the giga-ton mountains of rock and ice into stable orbits. Two orbits were established, running in opposite directions, so that service between the two worlds could be accomplished more efficiently. One can, by switching cyclers, make a round trip from Terra to Mars in one year, with no expended fuel.
There are only two available orbits for this kind of cycle. Politics being what they are, once one major power established a colony on the Cyclers they all had to, for military and scientific competition. In the space of about half a million miles there are over a dozen asteroids and iceteroids on each orbit.
These expensive hunks of rock were mined all the way to their new homes, of course, and the continuing mining operations off-set the initial investment needed get the massive things in place. In reality, it wasn't enough; the mining bubble burst in the mid-2200s as the Destiny Foundation went bankrupt. By then, enough people lived off Terra and on Mars that the cyclers continued to be occupied, with twenty permanent habitats between Mars and Earth.
These aren't the only oases in The Black Desert. The interesting thing about the Aldrin Cyclers is that their orbits alter slightly (watch the simulator here), moving around the ecliptic by about 51 degrees per orbit. This means that when the cycler's orbits reach their farthest points, which are in the Main Belt, they do so at seven different locations, passing through each in a seventeen and a half year long cycle. This means that each one of these locations gets visited by the Cyclers once every 30 months. It was only natural to alter the orbits of some of the more useful residants of the Main Belt to coincide with these locations and thus seven Main Belt Nodes were added to The Black Desert in a few decades.
The advent of IPVs during the Great War made manned spacecraft once again the fastest way to travel. Never the less, with nearly fifty colonies on the cycler route, the Black Desert has been and remains a large and important part of space and life in the twenty-third century.