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How difficult is interstellar travel?

I can only imagine a few reasons to go:

i) To see what's out there (which is pretty noble, and I fully support the quest for knowledge, but will VCs?)

ii) To escape a dying sun (by which time we may have other sci-fi tech like pushing planets around, etc.)

iii) For some reason it suddenly becomes much easier and we'd be fools not to go!
 
...to begin settling the galaxy before it's all taken by other advanced civilizations... come on any Civ player knows it!! Don't let those aliens REX you into a corner!
 
I've always wondered about the technology in "The Event Horizon." Are the ideas for interstellar travel expressed even theoretically possible (the idea of folding space so that your current position and your destination co-exist in the same place at the same time)? As I understood it, the idea bypassed the problems with faster than light travel, but does physics allow for space to be "folded" (assuming some technology is discovered to generate the gravity or other force that does the folding)? Furthermore, if it does, could the folding of space actually be used for travel in theory? or is there some other massive problem that folding space would create that would make travel impossible? Thanks for entertaining my curiosity.
 
tracer said:
Because there aren't any space aliens in our OWN solar system to have sex with.
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Just don't leave the ship while wearing a red shirt, or you'll be among the first to die. A blue shirt is better, you can be cool and still have those green-skinned babes all over you. A gold shirt is best, but they seem to attract aggressive males and rip too easily.

(Yeah, you can learn a lot about the universe from watching old Star Trek re-runs.)
 
Meadmaker said:
In my musings, I've often wondered if mankind could ever possibly really make it to the stars. I've occasionally seen speculations about it, involving Bussard Ramjets, or spaceships powered by atomic bombs, or whatever.

However, there is one basic point that has eluded me, because I don't know how to do the math.

How long would it take to get there? For example, to Alpha Centauri.

Let's suppose that, somehow, you managed to find a fuel that could sustain a 1g acceleration for a spaceship, going halfway to Alpha Centauri, 4.3 light years away, then decelerate at 1 g until you stopped at the star. A quick few punches on the calculator shows that, using Newton's laws of motion, it would take right about four years, with your average speed being right about the speed of light. (Assuming I didn't mispunch the buttons. I only did the calculation once.)

Unfortunately, the problem is that the peak speed is about twice the speed of light, and Mr. Einstein says that's a no-no.

How long would it really take? For the travellers? For the Earth based observers? I did a bit of googling trying to find a site that discussed the question, but I couldn't find one. Anyone know how to work out the relativistic effects? Or know of a web site that discusses the answer?
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To answer your title question, it is unbelievably difficult to do interstellar travel, no matter if it is slow or fast, using current technology.

To answer your question on the time it would take a ship capable of constant 1g acceleration to travel 4.3 lightyears and then come to a stop, it would take about 1 year to reach 90% of lightspeed, about 3 years of cruising, and about a year to stop. In total, somewhere around 6 years in total.
 
gorillapaws said:
I've always wondered about the technology in "The Event Horizon." Are the ideas for interstellar travel expressed even theoretically possible (the idea of folding space so that your current position and your destination co-exist in the same place at the same time)? As I understood it, the idea bypassed the problems with faster than light travel, but does physics allow for space to be "folded" (assuming some technology is discovered to generate the gravity or other force that does the folding)? Furthermore, if it does, could the folding of space actually be used for travel in theory? or is there some other massive problem that folding space would create that would make travel impossible? Thanks for entertaining my curiosity.
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A good reference is Stephen Hawking's "The Universe In A Nutshell"... so far, every loophole seems to have been closed. Disappointing, but intriguing just the same.

I need to study a bit of relativity... I have it in my head that FTL travel may be impossible, because regardless of what "shortcut" or "wormhole" or whatever way of bypassing relativistic constraints, simply arriving before the time it took for light to get there, opens the door to a violation of causality. Is that correct?
 
gorillapaws said:
I've always wondered about the technology in "The Event Horizon." Are the ideas for interstellar travel expressed even theoretically possible (the idea of folding space so that your current position and your destination co-exist in the same place at the same time)? As I understood it, the idea bypassed the problems with faster than light travel, but does physics allow for space to be "folded" (assuming some technology is discovered to generate the gravity or other force that does the folding)? Furthermore, if it does, could the folding of space actually be used for travel in theory? or is there some other massive problem that folding space would create that would make travel impossible? Thanks for entertaining my curiosity.
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I only know what I've read in articles and such, but from what I've seen it is "theoretical" in the broadest sense of the word. However, it would need so much energy as to likely be impractical no matter how much energy the human race could ever produce -- unless, of course, we find some new physics that allows us around that.

"Folding space" is certainly a mainstay of Science-fiction explanations for traveling "faster than light" -- although, not always as a means of going from point-to-point instantaneously. For example, "warp drive" such as in Star Trek is effectively "folding space".
 
gnome said:
A good reference is Stephen Hawking's "The Universe In A Nutshell"... so far, every loophole seems to have been closed. Disappointing, but intriguing just the same.

I need to study a bit of relativity... I have it in my head that FTL travel may be impossible, because regardless of what "shortcut" or "wormhole" or whatever way of bypassing relativistic constraints, simply arriving before the time it took for light to get there, opens the door to a violation of causality. Is that correct?
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Yep, because if you can do that, you can arrive back at your starting point before you left.
 
Schneibster said:
Yep, because if you can do that, you can arrive back at your starting point before you left.
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Here's a question:

What makes causality so sacrosanct?

The first order answer would have to be something to the effect of: without an assumption of the inviolability of causality, nothing would make sense! However, in terms of physical quantities, is entropy a stand-in for causality?
 
Soapy Sam said:
Mind you, if robots are good enough to do that, why send people at all, even in vitro?
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Of course, it's possible that the robots will be the ones who decide to go. By the time we have the propulsion systems, we'll probably have the AI. Or, should I say, "they" will have the AI.


I think an automated probe will be sent someday, and I think if an inhabitable planet is found, there will be strong pressure to send people, and plenty of volunteers to go.

This won't be for hundreds of years. It's hard to project from today's economy to one of the future. Likewise for social systems.

As for cost, I would gladly pay taxes comparable to what I pay for current NASA missions to Mars in order to support an interstellar mission. So, if it takes 100 years to build the ship, that's 100 years of taxpayers. The more difficult part is not getting approval, it's keeping approval for large periods of time.

Of course, with today's technology and economy, there's not much point. We couldn't build the ship in 100 years, or 1000 years.

I think people would be willing to be part of a truly grand expedition, even if they, themselves, were not participants. Even if they know they wouldn't live to see the conclusion. Expanding through the galaxy, however slowly, would have a powerful appeal. If you could build a ship that would be habitable for generations, and a propulsion method to reach the destination, people would go.
 
Meadmaker said:
As for cost, I would gladly pay taxes comparable to what I pay for current NASA missions to Mars in order to support an interstellar mission.
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So... essentially nothing?

NASA doesn't have a lot of money earmarked for Mars missions right now. Even those components of the new constellation of spacecraft NASA is developing ,that could be incorporated into future plans for a Mars mission, have more immediate, pressing and local goals.
 
Jimbo07 said:
So... essentially nothing?

NASA doesn't have a lot of money earmarked for Mars missions right now. Even those components of the new constellation of spacecraft NASA is developing ,that could be incorporated into future plans for a Mars mission, have more immediate, pressing and local goals.
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Phoenix launches August 3, and Spirit and Opportunity are still at work.

I think there are two orbiters active right now, too, but I wouldn't swear to that.
 
DRBUZZ0 said:
You also have to consider which star you want to go to Alpha Centauri, Proxima Centauri or Sirrius, then that might be something that could be done (it would take a hell of a long time and is not feisable at the current time).

But the question is why? Is there really anything that interesting about the stars closest to our solar system? It doesn't seem like they would have any interesting planets or that much could be gained in knowledge that can't be seen by telescope or radio telescope.

So lets say you are able to somehow produce enough thrust to move faster than any probe has before. Perhaps even an antimatter engine. You go out and spend decades or centuries heading to a system that isn't that interesting?

Really if you want to travel between the stars you need some sort of "warp drive" or other type of mechanism like that, which is beyond any foreseeable technology as things stand now.

It's worth nothing though, that if you could get very near to the speed of light, if you somehow had enough energy, then you could easily travel between stars or across the galaxy even. In your time perspective, the trip would be reasonably short, but during that time the earth may have already been destroyed by the dying sun, as to outsiders it would seem much longer in time.
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Had a question in freshman Physics about reaching the center of the galaxy in a human lifetime. As I recall, it is possible (I used an even more conservative rate of acceleration), but would take so much time from the Earth frame that it would be a useless undertaking.
 
Meadmaker said:
Phoenix launches August 3, and Spirit and Opportunity are still at work.
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Sweet Jinkies! I've been following Phoenix, too! I guess I meant to say 'manned' missions. I also assumed we were talking about manned missions to the stars.

I think there are two orbiters active right now, too, but I wouldn't swear to that.
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You're probably referring to Mars Reconnaissance Orbiter and (U.S.) Mars Global Surveyor? MGS is not in operation anymore. The ESA also has Mars Express in orbit.
 
Jimbo07 said:
Sweet Jinkies! I've been following Phoenix, too! I guess I meant to say 'manned' missions. I also assumed we were talking about manned missions to the stars.
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Yeah, no manned mission to Mars, and I'm not actually certain that's a bad thing. I like the concept, but perhaps it shouldn't be a priority just yet.

As for manned interstellar travel, what I was saying is that I would be willing to contribute taxes to such a mission, even if it meant sending a "generation ship", if it could be given a reasonable chance of success.

For the moment, that's not even a possibility. And that "moment" will last for a very long time, presumably more than my lifetime. I'm not sure it will ever happen. I think an unmanned mission will happen someday. A manned mission (really more of a migration than a mission) would happen if someone could come up with a way to do it, but I don't know if anyone ever will.

Thinking about whether a "generation ship" is possible, and whether it could be manned by reasonable people. Consider what is really being offered to the crew of such a ship. First, the "crew" would have to be at least several hundred. Second, the "ship" wouldn't be something like our current spaceships or airplanes. In terms of comfort, it would be at least like an ocean liner. So what do the people on it get? They get the chance to be founders of a new race. Those few hundred people will head out to a new planet, knowing that if they are successful, their names will be known for all time to their billions of descendants.

That's a pretty powerful motivation.
 
Founders of a new race only if its a colonization mission. This might require terraforming or at least a carefull evaluation of the target to see if its colonization is really viable.
 
DRBUZZ0 said:
But the question is why? Is there really anything that interesting about the stars closest to our solar system? It doesn't seem like they would have any interesting planets or that much could be gained in knowledge that can't be seen by telescope or radio telescope.
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It will be worth any investment when we can put an a self sustaining human population in other star systems. The earth and the sun are finite. Conservation efforts can only do so much. Eventually we have to consider this planet and star disposable. To say nothing of big rocks, or solar calamity.

While there may be no immediate urgency, ultimately we have to load up the truck and move to Beverly.
 
I highly recommend 'Centauri Dreams' by Paul Gister, 'Interstellar Travel and Multi-Generational Spceships' by Charles Sheffield and others, 'A Vision of Future Space Transportation' by Tim McElyea and 'The Starflight Handbook' by Eugene Mallove and Gregory Matloff.

The latest idea for interstellar travel I could find is M2P2, Mini-Magnetospheric Plasma Propulsion. A spacecraft creates an electromagnetic field around itself and inflates it with plasma (ionised helium) to create a magnetic bubble that both provides an immense area that acts as a sail which can be pushed with solar wind or a battery of solar-powered lasers and helps protect it from radiation and cosmic rays. M2P2 is reckoned to be able to achieve 20% lightspeed and could reach Alpha Centuri in 22 years.

A deuterium/helium-3 pulse fusion reaction drive could reach 10% lightspeed, and Stephen Hawking recently spoke of using antimatter drives to reach near lightspeed. At 90% lightspeed to travel 10 lightyears distance (most of the way to Epsilon Eridani, a 'nearby' sunlike star) would take 11 earthyears but the dilation of 2.3 means only 5 years will pass for the astronauts, which is as good as travelling at twice lightspeed, by their journey time. Wish I had been born 100 years later!
 
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