Read "The Martian Way" by Isaac Asimov online for free on Textopian. Full text with search, annotations, highlights, and AI-powered reading aids.
Ted Long wandered over the ridged surface of the ring fragment with his spirits as icy as the ground he walked on. It had all seemed perfectly logical back on Mars, but that was Mars. He had worked it out carefully in his mind in perfectly reasonable steps. He could still remember exactly how it went.
It didn't take a ton of water to move a ton of ship. It was not mass equals mass, but mass time! ! velocity equals mass times velocity. It didn't matter, in other words, whether you shot out a ton of water at a mile a second or a hundred pounds of water. at twenty miles a second. You got the same final velocity out of the ship.