There's one thing I never quite got about these speculations. When you consider a ship leaving a solar system and accelerating, and the speed gained turning the "ambient hydrogen" into deadly radiation, why does it always seem to assume that hydrogen atoms are just kind of hanging out at low velocities relative to the home solar system and only turn into a problem when the bald captain says "engage"?<p>Its a big universe, might the hydrogen atoms already be traveling at these deadly speeds relative to the ship once it leaves Sol? Might there be a "galactic current" so that the ship can go with the flow?<p>I know its just for fun but its still silly to think that anyone who could propel a canned ape at .8c wouldn't be able fend off a few rouge hydrogen atoms.
You know what else is an obstacle to relativistic spaceflight? Being able to do relativistic space flight.<p>Fun fact: people realized this a long time ago, and proposed different "shields" in front of the ship (it turns out that the most effective shape is a smoothed-out cone [of ice, say] -- see Asimov's Song of a Distant Earth).
Is this a reputable journal? It seems to be from the same publisher (<a href="https://en.wikipedia.org/wiki/SCIRP" rel="nofollow">https://en.wikipedia.org/wiki/SCIRP</a>) as <i>Advances in Pure Mathematics</i>, which recently accepted a paper written by a random text generator.
There's also the risk of hitting small dust particles, etc.<p>A quick back of the envelope calculation reveals that hitting a spec of dust that weighs just 1 ug (a millions of a gram) at 90% c produces ~36 mega joule.
Not a huge amount of energy (about the energy of burning 1kg of coal), but still.<p>Hitting a grain of sand (10mg) at 90% c produces ~360 giga joule (energy of a small lightning)
Why not use the speeding hydrogen in a nuclear reaction that fuels the ship, thereby killing 2 atoms with one stone?
See <a href="http://en.wikipedia.org/wiki/Bussard_ramjet" rel="nofollow">http://en.wikipedia.org/wiki/Bussard_ramjet</a>
That's okay, there's time to work on the shielding. 0.03 c is the most that can be feasibly achieved using top-end near future technology like dusty plasma fission fragment rockets.<p><a href="https://en.wikipedia.org/wiki/Fission-fragment_rocket" rel="nofollow">https://en.wikipedia.org/wiki/Fission-fragment_rocket</a>
I can't help thinking that statements like these are merely meant to bog us down. I've heard and read statements like 'Interstellar travel isn't possible.' or my favourite 'We've enough problems down here on Earth already so let's forget about the more visionary ones altogether.' since the eighties.<p>I mean, why does one become a scientist if one doesn't at least have some greater vision?<p>This kind of statement seems like conceding failure before even having tried.
I think once we are advanced enough to figure out how to propel anything that fast or able to pack the needed energy, this part might be easy to solve.<p>Remember per special relativity mass increases as we approach C.
Also I think there will be other physiological problems while accelerating to C. It would take like 34 days at 10g acceleration to get to C. I wonder how our bodies would handle 34 days at that kind of g limits. At 2g it will take like 173 days to reach C.<p>Lastly, we don't really have a good physical understanding of matter at near C speed limits. With mass increasing as we approach C, I don't know we can assume the same physical properties of any material in classical models.
I love this quote from the abstract:<p><pre><code> Diffuse interstellar H atoms are the ultimate cosmic space mines and
represent a formidable obstacle to interstellar travel.
</code></pre>
The paper[1] is an interesting read too, but of course there are other obstacles to relativistic spaceflight, such as reaching velocities capable of relativistic spaceflight.<p>[1] - <a href="http://www.scirp.org/journal/PaperDownload.aspx?paperID=23913&returnUrl=http%3a%2f%2fwww.scirp.org%2fJournal%2fHome.aspx%3fJournalID%3d69" rel="nofollow">http://www.scirp.org/journal/PaperDownload.aspx?paperID=2391...</a>
Reminds me of how the experts argued that the passengers would die of suffocation, if trains were to go faster than 50mph, back in the 19th century.<p>If we could figure out how to approach light speed, I'm sure we can also figure out how to shield people and electronics from harm.
I have always wondered what the probability of hitting a near-c object/dust particle/micrometeorite is between solar systems is within the galaxy. No doubt a near-c object (of any size) would end up trashing a spaceship, but whats the chances of it actually happening? Is it significant?
This has been speculated for some time, and one solution would be a Fusion Ramjet: <a href="http://en.wikipedia.org/wiki/Bussard_ramjet" rel="nofollow">http://en.wikipedia.org/wiki/Bussard_ramjet</a>