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A comment on Seven earth-sized planets discovered circling a star 39 light years from Earth. Parent comment

Re:Seven earth-sized planets discovered circling a star 39 l... by tim333 on Wednesday February 22, 2017 @01:55PM (#13708111)
Though that kind of performance is probably not going to come about from improvements to chemical rockets but moving to fusion. There are some promising developments on fusion reactors (see Breakthrough in Nuclear Fusion? - Prof. Dennis Whyte https://www.youtube.com/watch?v=KkpqA8yG9T4)

Guess something like that with the 100 million C gas doing the propulsion maybe?

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Re:Seven earth-sized planets discovered circling a star 39 l... by sbierwagen on Wednesday February 22, 2017 @05:46PM (#13709982)
Running a direct output fusion rocket in the atmosphere would be tough-- all the reactors we know how to build, or can vaguely guess how to build, run at small fractions of one atmospheric pressure.

If you have fusion engines, you would just be doing all the construction in orbit anyway, rather than boosting stuff from the surface of the orbit.

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Re:Seven earth-sized planets discovered circling a star 39 l... by kristopolous on Wednesday February 22, 2017 @04:53PM (#13709537)
There may have to be some clever system where you don't take a lot of fuel with you.

Imagine a type of particle accumulator and aggregator - call it cosmic flypaper. If you're going say 100 km/s, things seemingly insignificant and rare you may be able to collect a lot of pretty quickly.

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Re:Seven earth-sized planets discovered circling a star 39 l... by Arizhel on Wednesday February 22, 2017 @05:08PM (#13709669)
It sounds like you're talking about the Bussard Ramjet. It collects interstellar hydrogen gas for use in fusion engines. The problem is that it's unlikely there's enough hydrogen floating around for it to really work.
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Re:Seven earth-sized planets discovered circling a star 39 l... by bubersson on Thursday February 23, 2017 @02:34AM (#13712305)
Are there places that would have high concentrations of floating hydrogen? You would just need to "fly" through those.
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Re:Seven earth-sized planets discovered circling a star 39 l... by dragonwriter on Thursday February 23, 2017 @11:13AM (#13715039)
> Are there places that would have high concentrations of floating hydrogen?

IIRC, a Bussard Ramjet is at least potentially viable at the typical density in the galaxy, but unfortunately for any use by humans to get away from our solar system, or local region of space (to a distance, IIRC, on the order of 1000 light years in any direction) is a pocket of relatively low density.

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Re:Seven earth-sized planets discovered circling a star 39 l... by Arizhel on Thursday February 23, 2017 @11:06AM (#13714957)
Sure: stars. I don't think flying through those would work out well.

There's also nebulae. But that's only going to be useful when you're actually in a nebula, which isn't most of the time.

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