# Nuclear power question

**URL:** <https://boards.straightdope.com/t/nuclear-power-question/537948>\
**Category:** Factual Questions\
**Created:** [May 1, 2010, 6:04am UTC](https://boards.straightdope.com/t/nuclear-power-question/537948 "2010-05-01T06:04:40Z")\
**Posts on this page:** 1\
**Page:** 2

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**Author:** ![enigmatic](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@enigmatic](https://boards.straightdope.com/u/enigmatic)\
**Post date:** [May 3, 2010, 8:05pm UTC](https://boards.straightdope.com/t/nuclear-power-question/537948/21 "2010-05-03T20:05:29Z")

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> [@](#):
>
> Anti-matter? This is probably your one obvious reason, but space isn’t that empty. Interplanetary space has a density of 5-10 protons per cc from the solar wind. Never mind grazing a planet’s exosphere or a comet’s tail. That doesn’t sound a lot, but you’re going to be travelling very fast and going to hit an awful lot of them and their annihilation will be very energetic. It would swiftly be eroded by the solar wind and micrometeorites.

Partly, the obvious problem was figuring out a plausible design that could use collisions occurring primarily on the _front_ of the craft for propulsion. I was certainly assuming a much lower background matter density (I was thinking a similar number per square meter or so rather than cc, and probably guesstimating less energy loss with each collision, I haven’t done any actual math :p). This is all much less of a problem for how I was actually intending to use the basic idea in the story, the idea of using it in a remotely plausible, hard sci-fi ish space probe was a separate one.

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