Even Superman might not clear this half-mile high skyscraper

Is the sky really the limit when it comes to building skyscrapers? In Chicago lately it seems so. Technically the Windy City has been the skyscaper capital of the world since 1974 when the 1,450-foot-high Sears Tower was built. The world's fourth (Standard Oil) and fifth (John Hancock Center) tallest buildings are also firm pillars of the downtown area. Currently the rumors are rife that Skidmore, Owings, and Merrill, which designed and built the Sears and Hancock, will move to up its own record by designing another office-apartment-hotel complex shooting up almost one-half mile from the ground - or more than 800 feet higher than the Sears Tower. Skidmore's official stance is ''no comment,'' but few here interpret that as a denial.

Most architects and engineers insist that technologically there are no limits on how high buildings can reach - at least in those cities where earthquakes and soft soil are not a problem. They say it is largely economic factors which have inhibited the move skyward.

There is the major challenge, for instance, of not only finding investors, but enough ready and waiting commercial or residential tenants to start the immediate payback process. And the broad base required by design generally means many lower level offices without access to windows and natural light.

''We architects and engineers would love to build higher - just blow in our ear and have lots of money,'' says John Buenz, an architect with Solomon, Cordwell, Buenz and Associates, a firm involved in the design of several of residential skyscrapers here. ''The problem is not just the raw cost of construction, but creating so much space that you can't lease it within the time frame dictated by your financial arrangements. The minute you start building, you have to start paying for it.''

But even in areas where the natural base for a building is strong, New Jersey structural engineer August Komandant suggests that there are human factors which will effectively keep heights limited. Among them, he says, is the difficulty of keeping the necessary wind sway at the top within acceptable limits, providing adequate fire protection, and of building elevators in stages which operate economically, speedily, and safely enough to serve tenants well.