Use of External Tanks in "Red Mars"

Maya floated near the window wall of this bubble dome, looking back at the ship curiously. It had been constructed using space-shuttle external-fuel tanks; around the turn of the century NASA and Glavkosmos had begun attaching small booster rockets to the tanks and pushing them all the way into orbit. Scores of tanks had been launched this way, then tugged to work sites and put to use -- with them they had built two big space stations, an L5 station, a lunar orbit station, the first manned Mars vehicle, and scores of unmanned freighters sent to Mars. So by the time the two agencies agreed to build the Ares, the use of the tanks had become routinized, with standard coupling units, interiors, propulsion systems and so forth; and construction of the big ship had taken less than two years.

It looked like something made from a children's toy set, in which cylinders were attached at their ends to create more complex shapes -- in this case, eight hexagons of connected cylinders, which they called toruses, lined up and speared down the middle by a central hub shaft, made of a cluster of five lines of cylinders. The toruses were connected to the hub shaft by thin crawl spokes, and the resulting object looked somewhat like a piece of agricultural machinery, say the arm of a harvester combine, or a mobile sprinkler unit. Or like eight knobby doughnuts, Maya thought, toothpicked to a stick. Just the sort of thing a child would appreciate.

The eight toruses had been made from American tanks, and the five bundled lengths of the central shaft were Russian. Both kinds of tanks were about fifty meters long and ten meters in diameter. Maya floated aimlessly down the tanks of the hub shaft; it took her a long time, but she was in no hurry. She dropped down into Torus G. There were rooms of all shapes and sizes, right up to the largest, which occupied entire tanks. The floor in one of these she passed through was set just below the halfway mark, so its interior resembled a long Quonset hut. But the majority of the tanks had been divided up into smaller rooms. She had heard there were over five hundred of them in all, making for a total interior space roughly the equivalent of a large city hotel.