Up to this time (2054), man had been barred from the planets by the lack of a fuel cheap enough to make trips across interplanetary space economically feasible. Long, economical orbits could be used; but these brought on psychological problems resulting from living in cramped quarters for long periods of time, and problems of carrying enough supplies for such long trips. In shorter orbits, the profits would be burned up in excessive fuel consumption. The most efficient fuel was monatomic hydrogen, which is highly unstable unless dissolved in a catalyst to keep it from exploding at ordinary temperatures. The catalyst and the process for making the fuel were both expensive. Moon colonies were maintained only because the moon was the best known source of germanium; and its vacuum was a valuable location for astronomical observatories and atomic research laboratories. The neutron pile applied to space travel would make an interplanetary civilization possible. The pile, releasing neutrons and ions at velocities approaching that of light, would make use of small amounts of inexpensive materials as fuels. It also had frightening potentialities for mass destruction. The ambassador of the South American Republic thought of the destructive possibilities as he rode the small monorail car toward the Government Center in Chicago, which was now the capital of the North American Union. The shore of Lake Michigan was studded with tall skyscrapers connected by streets with transparent coverings. At ground level, a system of conveyer walks ranging from the hundred mile per hour strips in the center to five mile per hour strips on the edges, whisked brightly clad people about their business. On the second level, monorail tracks carried the high speed freight and passenger traffic of the city. The ambassador's car pulled in at a second level siding near the loading platform for the Government Tower. As he stepped from his car, he was met by two secret service agents who escorted him to the office of the Secretary of State. The Secretary sat behind a large desk in a comfortably furnished office on the eightieth floor. Through the large window wall behind the Secretary, the scattered towers of the city were somewhat obscured by flying snow and the gloom of a December morning. The distinguished looking man behind the desk had served his country well during the past thirty years. He knew the problems faced by such nations as the South American Republic, the League of Islam, the Asian Commonwealth, the decadent subject nations of western Europe, and the tiny, constantly warring states that comprise what was left of the once mighty U.S.S.R. That morning he had sent a note refusing help to the Baltic Federation, which had accused the Arctic League of aggression. The North American Union had no desire to enter foreign wars that did not concern it. The Secretary rose and extended his hand.