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Author Topic: Realistic Space Travel  (Read 11229 times)

Virex

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Re: Realistic Space Travel
« Reply #30 on: February 26, 2009, 08:03:10 pm »

The easiest solution to the fuell problem is, of course, to not bring any fuell with you. There are 2 known ways to accelerate a space-craft without the use of an internall fuell source, and those are:
Solar sails and their derivatives (magnetic sails, fission sails). They use radiation pressure from a star to act as an propellant, giving them a low but constant thrust. Not needing to bring any fuell or generators for propulsion makes them significantly more efficient then chemical or nuclear propulsion.
The second option would be the use of a Ramscoop, which is essentialy a fusion generator that plucks it's fuel directly from space by using a huge electromagnetic or electrostatic field. In theory this ought to provide unlimited thrust, but it depends on the drag generated by the solar wind and the ion denisty of the area the ship travles through. It's worth looking into though.

A last option, which does use fuell but provides impressive acceleration is given by Project Orion, which uses the explosion of nuclear bombs to push a ship forward. A thermonuclear Orion can, in theory, reach speeds of 0.1c, which would make traveling to some of the closer stars possible within 3 or 4 generations. The reason it's more efficient then a nuclear rocket is that in this desing the area that comes into contact with the exhaust fumes much further away, meaning it won't evaporate even at much higher temperatures, which in turn enables a much higher speed due to faster exhaust fumes.
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mainiac

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Re: Realistic Space Travel
« Reply #31 on: February 26, 2009, 08:24:56 pm »

Light can't have zero mass and zero kinetic energy. Because it can apply pressure. Therefore it still is energy and posesses mass. While travelling at the speed of light no less.

That's because light has momentum.  The momentum is not derived from kinetic energy, it is derived from the light's frequency.

If you are an ignoramus about these terms, please stop making crude assumptions about them.  If you don't know what you are talking about, wouldn't it be safe to assume that your proposed contradictions arise from unfamiliarity, rather then there somehow being a glaring flaw in the law of physics that no one spotted by now?
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Ampersand

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Re: Realistic Space Travel
« Reply #32 on: February 26, 2009, 08:45:12 pm »

Another, purely theoretical option is directly altering the properties of space. If one could by some mechanism cause space-time to contract in front of a vessel, and expand behind the vessel, speeds relative to other objects could be in excess of C, while not actually surpassing C relative to space-time, which is what really matters.

Of course, that's all pretty unlikely.
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puke

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Re: Realistic Space Travel
« Reply #33 on: February 26, 2009, 10:02:19 pm »

Conversations like this are interesting.  I've read some good papers that describe the size of ships necessary and travel times required to cross interstellar distances with conventional engines.  and by conventional engine, i mean the rather non-conventional ability to convert mass to energy with 100% efficiency, and direct it with perfect focus.

such a thing, while out side our grasp right now, is within the realm of technology that our current scientific theory can UNDERSTAND.  and it requires reaction mass on a nigh PLANETARY scale, at least if you want to get anywhere reasonably quickly.

anything else basically requires "magic" tech, space folding or warping or hyperspace or whatever the hell.  and that stuff is so far in the realm of fantasy at the moment, that its only worth speculating on in a purely masturbatory sense.

sure it might come to be someday, but its in the realm of theoretical physics that we cant even produce evidence for yet.  pure theory, and by theory i mean MADE UP.

I do like that made up stuff, and cant stop reading about it.  but its not very realistic, at least not in our generation.
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Servant Corps

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Re: Realistic Space Travel
« Reply #34 on: February 26, 2009, 10:04:31 pm »

Remember the main reason why I suggested a rocket that will take 100,000 years to get to Solar System B?

Because we already can produce rockets that can take 100,000 years to get to Solar System B! It is possible to go to Solar System B! We just need to stay alive for 100,00 years. Therefore, it's realistic, and won't make people roll their eyes. I don't want people rolling their eyes when reading a Sci-Fi Story.
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puke

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Re: Realistic Space Travel
« Reply #35 on: February 26, 2009, 10:11:46 pm »

a smarter man than me, and career science fiction author, Charles Stross, rants against the likelyhood of space colonization here:

http://www.antipope.org/charlie/blog-static/2007/06/the_high_frontier_redux.html

I think he's largely full of shit, though I do enjoy his books.  even so, that blog entery is probably good reading for anyone whos posting in a thread like this.
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puke

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Re: Realistic Space Travel
« Reply #36 on: February 26, 2009, 10:15:53 pm »

Remember the main reason why I suggested a rocket that will take 100,000 years to get to Solar System B?

Because we already can produce rockets that can take 100,000 years to get to Solar System B! It is possible to go to Solar System B! We just need to stay alive for 100,00 years. Therefore, it's realistic, and won't make people roll their eyes. I don't want people rolling their eyes when reading a Sci-Fi Story.

yeah, but the entirety of human civilization hasnt lasted that long!  i mean, your number is half the age of the oldest human FOSSIL, and over TEN TIMES the age of the oldest human writing!  come on now, i can roll my eyes at that, cant i?
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JoshuaFH

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Re: Realistic Space Travel
« Reply #37 on: February 26, 2009, 10:30:40 pm »

I don't think that the argument of "If something isn't already very old, chances are it won't last a long time anyway" is very valid.
« Last Edit: February 26, 2009, 10:36:33 pm by chaoticjosh »
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Psyco Jelly

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Re: Realistic Space Travel
« Reply #38 on: February 26, 2009, 10:34:19 pm »

Light can't have zero mass and zero kinetic energy. Because it can apply pressure. Therefore it still is energy and posesses mass. While travelling at the speed of light no less.

That's because light has momentum.  The momentum is not derived from kinetic energy, it is derived from the light's frequency.

If you are an ignoramus about these terms, please stop making crude assumptions about them.  If you don't know what you are talking about, wouldn't it be safe to assume that your proposed contradictions arise from unfamiliarity, rather then there somehow being a glaring flaw in the law of physics that no one spotted by now?

You're both kind of right. Light as a field would have no mass, but the individual photons do. Remember that light can be observed as either a particle or a wave.
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mainiac

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Re: Realistic Space Travel
« Reply #39 on: February 26, 2009, 10:40:30 pm »

You're both kind of right. Light as a field would have no mass, but the individual photons do. Remember that light can be observed as either a particle or a wave.

I have never heard of individual photons having a mass.  Got any links?
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puke

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Re: Realistic Space Travel
« Reply #40 on: February 26, 2009, 11:24:29 pm »

I don't think that the argument of "If something isn't already very old, chances are it won't last a long time anyway" is very valid.

I think the idea of waiting for a single spaceflight over a period of time that is over 10x longer than the earliest writings of our species, and closer to 200x longer than what most people would call "civilization" is perposterous enough to warrant the rolling of eyes.

especially given that we advance technology at a parabolic rate, and the last 200 years alone brought more progress than the last 200,000 combined.  its pretty unlikely that anything recognizeable as the human animal will exist that long -- and if the decendants of our culture are still around, speculation on what they might be like would more properly belong in a transhumanist / singularity kind of discussion.

if we could somehow construct a self-sustaining and self-repairing ship to last that long, the humans it caried in suspended animation would be starting a new human race without contact to their parent civilization, which would have probalby long since either transcended somehow, or gone extinct.
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Servant Corps

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Re: Realistic Space Travel
« Reply #41 on: February 27, 2009, 12:14:54 am »

Quote
I think the idea of waiting for a single spaceflight over a period of time that is over 10x longer than the earliest writings of our species, and closer to 200x longer than what most people would call "civilization" is perposterous enough to warrant the rolling of eyes.

In my defense, this does violate common sense. The violation of common sense seems less of a concern to me than the violation of the laws of physics. Violation of common sense can be explained away by humans being stupid. Violations of the laws of phsyics cannot be as easily explained.
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Psyco Jelly

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Re: Realistic Space Travel
« Reply #42 on: February 27, 2009, 12:27:55 am »

The "regular" mass of a photon is 0, then later on states the relativistic mass of a photon is 1.110−52 kg.

The wikipedia article sort of contradicts itself. Dammit! I should know this! I'm taking a particle physics course!
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mainiac

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Re: Realistic Space Travel
« Reply #43 on: February 27, 2009, 12:57:56 am »

You are taking a course in the subject and referring to wikipedia?  I would so totally mock you if I didn't constantly do the exact same thing.  I really hope I outgrow the habit before getting a real world job.
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Ancient Babylonian god of RAEG
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Il Palazzo

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Re: Realistic Space Travel
« Reply #44 on: February 27, 2009, 01:20:11 am »

The "regular" mass of a photon is 0, then later on states the relativistic mass of a photon is 1.110−52 kg.

The wikipedia article sort of contradicts itself. Dammit! I should know this! I'm taking a particle physics course!
this is somewhat blurred in my mind, as It's been a while since I took my physics course, but as far as I remember:
Photon's mass at rest is 0. Of course, photon cannot be at rest, but it gives you a clue that it can go at the speed of light at all(since it's rest-mass won't grow to infinity this way).
Relativistic mass of photon is derived from it's momentum, which as mainiac mentioned is related to photon's frequency. So it's like: mc=p and p=hf/c(h-planck's constant; f-frequency) - so m=hf/c2.
Or something like that. You people who actually study this stuff can correct me.
Quote from: Psyco Jelly
Light as a field would have no mass
I'm probably just being obnoxious here, but light is not an EM field, it's said field's oscillations.

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Nothing can be created and already posess a speed by virtue of existing.
I think that it's just your unbased assumption. After all, why not?

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Why exactly does acceleration become difficult?
You know, I've been thinking about it, and it shames me to admit, that I'm at loss as to why it is supposed to be so. After all, the thing that first comes to mind is the relativistic mass increase, that would need more and more force to accelerate it by the same factor. Yet, the mass increase is associated with the frame of reference that is moving, i.e. from the point of view of the ship, it's the planets that are moving. So it's the planets that should gain mass, not the spaceship, no? Somebody help me here.
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