Construction on Biosphere 2, that would originally support the life of eight participants, commenced in 1987.
Since large internal supports were out of the question, architects employed a design of interconnected steel struts and air tight, steel framed, high performance glass.
But, because the structure was so tightly sealed, engineers needed to devise a method for dealing with the diurnal changes of the internal atmosphere. Their solution was a set of giant lung-like diaphragms that accommodated not only the increased air expansion during the hot daytime hours, but the contraction at night when the air cooled; thus preventing damage to the superstructure.
When completed in 1991, the structure enclosed 7 million cubic feet of space with the highest point looming over the rainforest at 91 feet, and occupied a little over three acres of Sonoran desert near Oracle, Arizona.
A four-inch thick, welded substructure of steel combined with a highly sophisticated system for recycling the air, water and nutrients sealed the ecosystem from all outside elements.
However, the one component overlooked at the time that perhaps contributed to the demise of the Biosphere 2 project, was the extraordinary amount of concrete used for building rock outcrops in the landscape.(to be continued . . . ) Next week’s episode: The inside story