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Humanity needs to leave earth and travel to a new home planet. Given that the technology for fusion reactors is available, how fast could they realistically travel?

There are two scenarios I'm interested in:

  • Living humans in a spacecraft (in hibernation or on a generation ship)
  • No living humans, only cargo with DNA samples

The questions are:

  • How much acceleration would be survivable for a human?
  • How fast could an spacecraft go without compromising structural integrity?

It appears that nothing above 10% of the speed of light would be realistically doable.

a4android
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John
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  • While these are interesting questions, Worldbuilding really isn't the place for them. This particular forum focuses on building up of fictional worlds; your question is largely one of plot & technology. I'd suggest asking over in the Scifi & Fantasy forum for the story aspects and in the Physics forum for the more sciencey aspects of your question. – elemtilas Feb 24 '18 at 16:27
  • Speed is relative If you are at high speed relative to the asteroids (with spikes; the worst kind) you are moving thru, they might compromise your structural integrity. If you are at high speed relative to a distant star and you have nothing in your path, no problem. Excellent stats on humans and acceleration here: https://worldbuilding.stackexchange.com/questions/88002/can-a-human-survive-acceleration-from-0-km-h-to-310-km-h-and-then-back-down-to – Willk Feb 24 '18 at 17:24
  • You are asking two questions here, it seems. It is better to limit yourself to one question per question. Especially under hard science tag. Are you sure you even need hard science? Wouldn't science based suffice? – Mołot Feb 24 '18 at 17:58
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    @John - "How fast could an spacecraft go without compromising structural integrity?" Well, some accelerations are too strong for structural integrity, but as long as the acceleration is acceptable there is not speed limit. However, the faster the the speed the worse the encounters with grains of space dust or hydrogen molecules will be. At high enough speeds hitting one would be like exploding an atomic bomb on the ship. The top speed may be limited by the ship's protection against such encounters. – M. A. Golding Feb 24 '18 at 18:43
  • @M.A.Golding True any space debris would be lethal without proper protection. I'm not really familiar with the physics, but my guess would be that keeping the spaceship together under such massive acceleration is much harder then protecting against particle or atom size debris. Could the fictional spacecraft even go so fast that atoms would be become deadly without killing the crew? – John Feb 24 '18 at 22:42
  • @John, One g of acceleration is plenty to reach an appreciable fraction of the speed of light in under a year. Which is a good deal less then most interstellar trip times. And other considerations like hitting interstellar dust will likely constrain you to slower speeds. Also there are no near future fusion rockets that would allow anywhere near this. – Lex Feb 25 '18 at 02:59
  • @elemtilas Technology is an element of worldbuilding and there is nothing about a plot in the question. These factors make the question both valid and on-topic here. – a4android Feb 25 '18 at 03:17
  • @a4android Yes technology is an element of worldbuilding, but the questions do not relate to technology within the context of an alternate world. The actual questions relate to spaceship design parameters (acceleration & velocity). The background / scenario is plot & narrative centered: two basic story lines are given (humans on board the spaceship, DNA only on board) along with the clearly narrative focus (humans have to leave the Earth). – elemtilas Feb 25 '18 at 04:40
  • @elemtilas You raised technology, now you are contradicting yourself. The background may be a scenario, This is true of many questions. But the question concerns the design parameters for the related scenarios. Nothing about the question advances the story or its plot. You misread the question. – a4android Feb 26 '18 at 04:00
  • @a4android Perhaps... In any event, the long and the short of it is that questions asking about what forces the human body can survive and structural integrity of materials have nothing to do with worldbuilding, and have nothing to do with the specific in-world technological context. This is true of too many questions here in Worldbuilding. I'm simply suggesting that this forum is not the most appropriate for this particular question. – elemtilas Feb 26 '18 at 23:32

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