The screen was filled, as he spoke, with diagrams of the Scavengers on the route to Mars; little, grinning caricatures of ships, reaching out wiry, tenuous arms that groped for the tumbling, empty shells, seizing and snaking them in, branding them MARS PROPERTY in glowing letters, then scaling them down to Phobos.

Then it was Hilder again. “They tell us eventually they will return it all to us. Eventually! Once they are a going concern! We don’t know when that will be. A century from now? A thousand years? A million? ‘Eventually.’ Let’s take them at their word. Someday they will give us back all our metals. Someday they will grow their own food, use their own power, live their own lives.

“But one thing they can never return. Not in a hundred million years. Water!

“Mars has only a trickle of water because it is too small. Venus has no water at all because it is too hot. The Moon has none because it is too hot and too small. So Earth must supply not only drinking water and washing water for the Spacers, water to run their industries, water for the hydroponic factories they claim to be setting up—but even water to throw away by the millions of tons.

“What is the propulsive force that spaceships use? What is it they throw out behind so that they can accelerate forward? Once it was the gases generated from explosives. That was very expensive. Then the proton micropile was invented—a cheap power source that could heat up any liquid until it was a gas under tremendous pressure. What is the cheapest and most plentiful liquid available? Why, water, of course.

“Each spaceship leaves Earth carrying nearly a million tons—not pounds, tons—of water, for the sole purpose of driving it into space so that it may speed up or slow down.