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Answering the question "What is your favorite SF propulsion concept?" recently on Quora.com reminded me of a science fiction story I read many many years ago.

I can’t recall the name of the writer. Nor the title of the story. It may have been called something like “Walking Home,” though that’s not the title, I don’t think.

Here's a synopsis: a ship is stranded out beyond Neptune, and it’s got this nifty tech, a machine used for moving cargo that can grab onto space. So the crew are trying to get back to Earth by using this device to anchor to a point in space and then everyone pushes the machine to the stern of the ship, where they let go of space, push the machine back to the bow, grab space again, and walk the machine back to the rear of the ship, wash rinse repeat, wash rinse repeat. The ship has become a generation ship with people walking home.

I hope someone can help resurrect the author’s name and the story’s title. I read this as a kid over 50 years ago (I think), and it really stirred my imagination. It had a Cordwainer Smith kind of brashness and originality to it, though the writer wasn’t Cordwainer Smith.

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This is "The Long Way Home" by Fred Saberhagen.

... Then the main group will start pulling against number one, as I saw them doing a little while ago, and their ship will begin to move toward Sol. Every day they go through this they move about thirty miles closer to home. "Honey, these people are walking home and pulling their ship with them. It must be a religion with them by now, or something very near it . . ." He put an arm around Laura.
"... how long would it take them?"
"Space is big," he said in a flat voice, as if quoting something he had been required to memorize.

After a few moments he continued. "I said just moving a little faster won't help them. Let's say they've traveled thirty miles a day for two thousand years. That's — somewhere near twenty-two million miles. Almost enough to get from Mars to Earth at their nearest approach.

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    That story has a huuuuge plothole that it tries to lampshade away, but fails: an object in motion tends to stay in motion. If they did the walk one time and then released all anchors, their ship would be moving at 6 miles per hour. Every walk after that should've added to their speed, and they should now be travelling at a considerable clip. (It's like poling a gondola: you don't stop the boat at the end of each stroke, for heaven's sake!) – Martha Feb 9 '18 at 6:29
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    @Martha - That's addressed. They don't want the passengers idle for hundreds of years. Also, each time they weigh anchor it's a static point in space. If they're already moving, the anchor would rip a hole in the side of their ship – Valorum Feb 9 '18 at 8:17
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    @Martha I thought the same. Although, since the device grabs onto space, as OP suggests, I guess that wouldn't work. If the device cancels/ignores inertia/momentum when enabled (like an "instant" anchor), the ship could probably only go as fast as the device can be physically moved. One would need to turn it on, run with it from one side of the ship to the other, and while running turn it off. This would propel the ship to, say 10-15Mph. Turning it on again would stop the ship dead in its tracks, wouldn't it? – r41n Feb 9 '18 at 8:31
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    @r41n of course, the whole concept of an anchor to space, is ridiculous, considering that this “static point in space” is actually moving with the entire solar system around the center of the galaxy, while the entire galaxy is moving through the space and so on. Plus, unless the ship is in an orbit around the sun, the sun’s gravity will already help the ship accelerating towards Earth (well, stopping when crossing Earth’s path will become the actual problem). Even if they are in an orbit, they wouldn’t be anymore after their first push towards the center of our solar system. – Holger Feb 9 '18 at 10:32
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    @Holger, indeed, it's still fun to think about such concepts though :) – r41n Feb 9 '18 at 10:46

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