But he would get there eventually, even if he did nothing about it. The balloon overhead was merely acting as an efficient parachute. It was poviding no lift, nor could it do so, while the gas inside and out was the same.

With its characteristic and rather disconcerting crack the fusion reactor started up, pouring torrents of heat into the envelope overhead. Within five minutes, the rate of fall had become zero; within six, the ship had started to level. According to the radar altimeter, it had levelled out at about two hundred and sixty-seven miles above the surface, or whatever passed for surface on Jupiter.

Only one kind of balloon will work in an atmosphere of hydrogen, which was the lightest of all gases and that is a hot-hydrogen balloon. As long as the fusion reacter kept ticking over, Falcon could remain aloft, drifting across a world that could hold a hundred Pacifics. After travelling over three hunndred million miles, Kon-Tiki had at last begun to justify her name. She was an aerial raft, adrift upon the currents of the Jovian atmosphere.

Though a whole new world was lying around him, it was more than an hour before Falcon could examine the view. First he had to check all the capsule’s systems and test its response to the controls. He had to learn how much extra heat was necessary to produce a desired rate of ascent, and how much gas he must vent in order to descend. Above all, there was the question of stability. He must adjust the length of the cables attaching his capsule to the huge, pear-shaped balloon, to damp out vibrations and get the smoothest possible ride. Thus far, he was lucky; at this level, the wind was steady, and the Doppler reading on the invisible surface gave him a ground speed of two hundred and seventeen and a half miles an hour. For Jupiter, that was modest, winds of up to a thousand had been observed.