gravity screen n.

With all their advance in science, they had lost the secret of the space-ships, the gravity screen.

For twenty or thirty miles into the back-bone of the Andean mountains massive reinforced steel tubes were driven to withstand the terrific constant strain of the tubes as they sent forth a vast field of gravitation, retarding the motion of the planet. The huge gravity screens of the tubes fed on large vats of silicon dust which broke down atomically, releasing a powerful negative field of gravity.

Jovian crowds shrieked in terror, then laughed uproariously as they swung suspended in air above the Gravity Screens.

‘The turbos are heatin’. They won’t take any overload on deceleratin’.’ ‘Won’t have to. We’ll cut in the gravity screens in reverse.’

Gravity-screens, to take only one example, make it possible to use android robots of such size that they could exist only in a slight gravity.

‘They have antigravity! Isn’t that it?’ ‘Yes…. Of course, it couldn’t be a complete gravity screen by any means. But it seems to be a good long step toward it.’

But suppose the spaceship has a gravity screen plastered all over its hull and that, at a particular moment, the screen is activated. Now, with no gravitation to hold it down, it is cast off from the Earth like a clod of mud from a spinning fly-wheel.

‘I’ve rerouted the gravity subsystem to the negmass, but I can’t access the main bus without... shit!’ The deck buffeted violently as the timeship hit heavy turbulence. Through the headset, Franc heard Hoffman curse as he pitched sideways once more; true to his word, he had cut off the gravity screen.