Feasability of Interstellar Travel

Great Debates
1

This debate was inspired by the (somewhat hijacked) general questions thread on interstellar travel linked to below, and will probably include some spillover discussion from there. http://www.straightdope.com/ubb/Forum3/HTML/004981.html

Let me start off by saying that I’m somewhat tired at the moment and may not make any sense below, so I reserve the right to come back and rewrite this whole post.

It is my opinion that any sort of interstellar travel other than sending out automated probes is not practical in the somewhat near future (say 200 years).

Very fast jaunts to other stars are simply out of the question; the speed of light sets a rather absolute barrier, and practical limits further hinder such an undertaking. Longer trips require the ship to be a basically self-sustaining habitat, since you pretty much have to make a one-way trip to wherever you’re going.

Because of the astronomical (pun intended) expense in getting a ship to another star in a reasonable time, and the fact that an interstellar ship would have to be a relatively self-sustaining habitat, there’s not really much reason to send the ship to another star; you can put much lighter engines on the craft and use the technology to live off-planet in the solar system. You can get away from whoever you don’t like on Earth, you can gather resources from various bodies in the solar system, and you can get help for any problems you encounter much more easily.

The only real motive to send people to another star system is a raw desire to go where no man has gone before. While for a few people this is a strong motivator, for most people it’s not even particuarly interesting. Without widespread popular support, the sort of massive expenditure for manned expeditions to other stars (democratic countries go by majority vote, autocratic countries don’t tend to be very big on huge scientific expeditions) simply isn’t practical. And we’re not talking about something on the order of the NASA budget, were talking about spending a significant percentage of GNP here.

Obviously, at some point it will become cheap enough to casually send a ship/habitat to another star, but I don’t see how this point would come anytime soon, given the historical trends in how quickly available energy has increased.

I suspect that medical technology will be the answer for those who want to reach the stars. Being able to put people into some kind of stasis (cryogenics, for example) or massively extending the human lifespan will increase the effective or actual lifetime of our potential starfarers to the point that a 50 year trip doesn’t waste a significant fraction of their life.

(This message is rather brief and berift of explanations, but I figure letting people question me is easier than trying to cover all the bases.)

Kevin Allegood,

“At least one could get something through Trotsky’s skull.”

  • Joseph Michael Bay
2

Short of some truly magnificient breakthrough in physics, such as a “warp drive” that would eliminate distances between points in the universe by bending the space-time continuum, interstellar travel is a no go. If we could go to the nearest star as fast as we can go with our current technology, and disregarding carrying the fuel, it would take us 30,000 years to get to the nearest star. The distances between the stars is truly unimaginable. There’s a reason it’s called space: there is almost nothing there but space. As I’ve heard it (I think from Bill Nye the Science Guy- isn’t he the coolest) if the earth was a golfball placed on a high school track, Mars would be 100 yards away, and Pluto would be 15 laps around the track (each lap is 400, you do the math). The nearest star in our little scheme would be a full circufrence around the real earth- 26,000 miles! So I’d say it’ll be a while before we make any friends from other star systems.

It’s not how you pick your nose, it’s where you put the boogers

3

The hard cold numbers are not what most people want to talk about when it comes down to space travel. Look at us now. The number of people who have stood upon any body other than the earth has not gone up in the last half of the Space Age. The number of people involved in the Space Age as participants has stayed fairly constant, as well. Learning, and military experimentation are the driving forces behind most of our current space program. Putting people onto other planets is a very common dream. It is pretty much only a dream now.

The real cold hard facts are that it was always only a dream for the overwhelming majority of the people actually involved. Even among professional space travelers the majority have never been more than a few hundred miles from the Earth. Space travelers might rack up the miles pretty quickly, but the most seasoned space travelers in all of history have spent more time on the ground waiting for their chance to go, than the total of all their mission time. Space travel is a fleeting moment of realization for a lifetime of dedicated effort, and that is for the tiny elite among all human kind.

That picture holds for movement around the near location of Earth’s current location in it’s orbit. Move away from there and the picture gets really bleak, for the dreamers. It will take many billions of human/hours and many billions of dollars, and billions of tons of equipment and supplies to send one person to another star. Now its time for lift off, and one person gets to spend the rest of his life living the dream of all the billions who paid the price. How often do you think that is going to happen?

I don’t get to go. I know that. Pretty much no one alive now gets to go, if we all agree to spend ten percent of the effort of the entire race to send someone as soon as we possibly can. The facts don’t change by spending more money, either. You can quadruple the effort, and send two people, or send one person before I die, although he won’t be back while anyone I know is still alive. Can anyone remember the last multi-generation project we completed from scratch as a race? Building Cathedrals in the Middle Ages I think. We have not shown a strong penchant for delayed gratification as a society, during my lifetime.

And the bad news is that the sociology part is the good news. We could do it, by extending every part of our existing technology to the foreseeable extent that we now believe it will reach. But we can’t get our one volunteer back. We can’t get his, and his astronaut wife’s descendents back either. Cause we can’t be sure that they will have a healthy child, or that the child will have “the right stuff” to be an astronaut, or even survive conception, birth, and growing to adulthood in space travel conditions. The ship that will support enough people and habitat to make survival of a social unit of more than a dozen people is a bigger pipe dream than Warp Drive.

The generation ship, built in space requires a space program large enough to lift the components, and personnel to the construction site, keep them alive, and productive, and then collect the fuel and reaction mass for the trip. All this has to be done at a cost to Earth equivalent to an Apollo Project for every element of the process. That means one Apollo Project for the design, one for the station habitat, one for the shipbuilding facility, one for the propulsion system of the ship, one for the habitat of the ship, one for the equipment for the education, of the offspring of the travelers, one for the astronomic observation to decide on a destination, one for the engineering needs of the visitors who may return, and the whole thing has to be done before we even decide who will go.

Now that we have this small town in orbit, ready to roll, take the numbers for the weight of a town, and crunch the numbers for the fuel and reaction mass needs for the trip. Turns out perfectly efficient rockets are waaaaaay to inefficient for this trip. The light sail to move a town is a bit larger than what you are used to hearing described in sci-fi stories. Want to take a spare? Your Bussard Ram Jet hasn’t been perfected, and you have to bet now if you want to design for it, or not. If you are wrong, you have a very expensive small bed and breakfast in orbit for your efforts. If this trip is more than a fly by, you have to have something planned to stop you at the other end. If you were wrong about the availability of anything at all at the other end, everyone dies.

By the way, the folks on the other end of this trip are not volunteers. I find the ethics of their responsibility to us tenuous. I figure they owe no one anything, and can sell the whole ship to the Galactic Overlord, for a small asteroid habitat in his empire, if they want. Meanwhile back on Earth we get to spend the hundred years after they don’t come back wondering just what that fact means. Because we certainly cannot communicate with them, or even hear from them. They can’t even hear from us, unless you want to add the weight of the Ariciabo instrument to the payload.

I love science fiction. The best thing about it is that you can just say that you are using a hyperspace field generator, and the next thing you know, you are chasing asteroid pirates around the Swarm, in orbit around Proxima. You can’t build the ship until you know how big the generator is, and how much room you need to hold those pirates prisoner.

<P ALIGN=“CENTER”>Tris</P>

On two occasions I have been asked [by members of Parliament], ‘Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?’ I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.
– Charles Babbage,(1792-1871)

4

BigDaddyD wrote:

cough Orion cough DS1 cough

The truth, as always, is more complicated than that.

5

Triskadecamus writes:

And so?

We are all of us on a one-way journey through life. None of us is going to be retrieved, and none of us is ending this journey alive.

Many men (and not a few women, either) have shown in the past that they were willing to risk their lives, yea, even with the certainly that they would lose them, for causes that they thought were significant. Many have shown a willingness to spend long periods, even up to their entire life expectancies, in isolation from their fellow humans.

If we say that, in the industrial portion of the world (assuming of the sake of discussion that the first interstellar explorer is not coming from Rwanda) this mindset is extinct, then I would assert that interstellar travel would be the least significant consequence of that extinction.

(I also believe that Triskadecamus is completely wrong is his assessment of the technologies involved and needed, but that’s an argument that I am not making now.)

It is often said that “anything is possible”. In fact, very few things are possible, and most of them have already happened.

6

To summarize my thoughts from the thread Riboflavin mentions:

With refinements of existing technology a fifty year trip to Alpha Centauri is possible. (Orion coupled by double slingshot around Jupiter and Sun.)

As little as a fourteen year one-way trip is possible with a few likely achievable scientific advances in the near future (Laser powered Solar sail.) The investment needed to make the latter feasible is so horrendous that it’s not likely to be done anytime soon.

Is that fair Riboflavin?

That being said I agree that it probably won’t happen within the next 100 years or so.
The infrastucture needs to be built so that mankind has a significant presence in space throughout a good chunk of our solar system, before such a project could be undertaken.

Right now we still launch to space with Boosters developed during the Eisenhower era.

Space unfortunately, is not a priority in our society. This is a shame. Exploration launched Spain into an economic golden era after the voyage of Colubus.

Often wrong… NEVER in doubt

7

Okay, everyone, let’s start by debunking Einstein…

Interstellar travel is possible, if people are willing to spend a few generations in transit, and never see the Earth again.

I sold my soul to Satan for a dollar. I got it in the mail.

8

Suppose we go to another star system. And when we get there we find: Nothing.

There is no evidence that all stars, or even a majority of stars posses planetary systems.

And if our target star does have planets, what if they’re just balls of rock like Mercury, or gas giants like Jupiter? It’ll be no mean feat to say, “The hell with this place. Let’s go someplace else.”

The people that think we can jockey around the galaxy at will have no concept of distance or energy.

We live in a universe governed by physical laws, not by the dreams of men.

That’s why I take UFO reports with a ton of salt. They may be out there, but Extra-Terrestials are constrained by the same laws.

When the pin is pulled, Mr.Grenade is no longer our friend.

9

While it is true that Spain reaped great benefits from Columbus’ expeditions, the likelihood of finding anything useful and being able to bring it back is quite low. To get us to go to the moon, we needed a space race with the Russians to motivate us. We have no such motivation to even send a man to Mars and back, let alone Alpha Centuri.

It’s not how you pick your nose, it’s where you put the boogers

10

None of the methods presented to further our expansion wiil be used. I’m afraid that you couldn’t find a single congressman who would fund a project that wouldn’t produce results during his or her term. They vote for things they can claim credit for.
Before you turn to private enterprise, look at the current state of Wall Street. Companies are slitting their own throats for the immediate satisfaction of the share holders, and turn a blind eye towards the long term vision needed for such a venture.
Larry Niven presented a couple essays on long-term space travel in the collection All The Myriad Ways.

11

Scylla wrote:

Yeah, but the Spaniards didn’t have to carry their own air with them.

One of the standard UNIX fortune file entries reads: “Men will often change their opinions, but they will seldom change their convictions about them.”

Changing my level of conviction about my opinions was probably the most painful step I took on the road to Skepticism[TM].

The truth, as always, is more complicated than that.

12

And you’d be surprised how many of them there are. I actually know people - reasonably intelligent, college educated people - who think the Hubble takes better pictures of “nebulas and galaxies” because it flies around the universe and gets up real close to them.

Anyway, as others have mentioned, going to other stars is so hard that for now we might as well consider it impossible. Going to places like Mars for more than a short trip is also very hard, but perhaps worth thinking about over the next few centuries.

While there are huge technological, social, and political barriers that are preventing us from doing that currently, I believe that ultimately, it’s critical that humanity establish a sustained colony elsewhere. I’m looking at it like this: we don’t currently know how common or rare technological civilizations might be. We’re the only example we know of, and currently, all our eggs are in one Earth-sized basket. A single extinction event, whether external or internal of origin, is sufficient to kill us off, and we know that extinction events happen from time to time. (Thankfully, not too often!)

I can easily envision a universe where intelligent life is “relatively” common, but I can also envision one where intelligence is an evolutionary dead end, and civilizations like ours tend to kill themselves off in short order. We’ve only had civilization for a few thousand years - basically no time at all. Regardless, if we make it a goal to insure that there is a sustainable chunk of humanity living off-world, this gives us a sort of primitive insurance policy against a number of possible unpleasant ends to our race. And if life like us is rare, it would be a real shame if we died off without having done our best to prevent it.

–
peas on earth

13

bantmof, I agree wholeheartedly with most of your post. Particularly the part about establishing a colony on Mars. But we should do it NOW, not in a few centuries. There is no huge technological barrier – we can do it with our current technology. There very well may be social and political barriers, but these too can and should be overcome immediately.

I recommend a very good book on the subject titled “The Case For Mars” by Robert Zubrin.

14

Yeah, I’d like to see us start ASAP too, Hardcore. I think we need to do it in a way that’s acheivable, such as working initially on reducing cost-to-orbit instead of bankrupting ourselves with today’s ultra expensive launchers. We pay some lip service to this issue now, and devote a token amount of money to it, but if I had to place my bets on where to start, that’s what I’d pick. Once we can get cost-to-orbit down by a factor of, say, 100, or even 1000, it’ll make it worlds easier for us to get large amounts of stuff to Mars. (We could probably go to Mars with Apollo-era tech, but only in the sense that we went to the moon - land, hit some golf balls, and come home. I’d really like to see something longer term).

I’m not too optimistic though. During the Apollo days, I used to believe that I’d see mankind at least set foot on Mars in my lifetime. But this is currently looking most unlikely indeed. :frowning:

–
peas on earth

15

Tell me about it… Reducing cost-to-orbit would have a tremendous impact on the space program and literally jumpstart space exploration by the private sector. The older I get, the more important this topic becomes to me.

Maybe our grandchildren will walk on Mars.

16

Tracer:

Yes, my signature is a reminder Abot being too sure of one’s self… So what?

While doubtless we won’t be flitting around the galaxy anytime soon, Mars is well within reach.

The Mars Direct program would land a team on Mars for a 1.5 year stay in 2007 if it can get funding. The cost is about that of an aircraft carrier or so.

Unlike the Lunar program when Kennedy made his “we will go to the moon” speech, there are no technological hurdles to be crossed to do this. We have the technology now.

If the next elected President were to get behind this program he may very well see it to fruition in his second term.

“Mars Direct” would create a more or less permanent mars base. The benefits to doing this are self-evident over the long term.

Yes, unlike the Spaniards before us, we will have to carry our own Oxygen for the trip. This will be a lot easier for us to do than it was for the Spaniards to carry fresh fruit and water on their voyages.

Often wrong… NEVER in doubt

17

Alright… I’m going to break this posting frenzy of mine into several posts for readability; this one is general stuff, the second will be on ‘mars colony’ posts, the third to my arch-nemisis Scylla:

BigDaddyD,

If you’re disregarding carrying the fuel, simple chemical rockets (like those in the space shuttle) could make the trip in less than 10 years, although the fuel requirements for this stunt would be significantly larger than the mass of the observable universe. Various other technologies available today could make the trip to Alpha Centauri in far less than your 30,000 years figure, even considering fuel requirements.

Tris,

How common of a dream is it, really? Most people would think that putting someone on another planet is pretty neat, but don’t think of it as any sort of real goal.

I disagree there; a generational ship is something that will probably be within our capabilities within centuries, while a warp drive is pretty much impossible (things like the Alcuberrie warp drive require things like negative matter, and have weird problems like not being able to stop or start). You mention building a generation ship by lifting all of the components from Earth, which I would agree is a pipe dream, but if you have orbital habitats you can build such a ship moving matter around in orbit and you’ve already got the technology for the living sections (since you’ve got orbital habitats). It’s not anythint we’ll be slapping together next week, but it’s far from impossible.

Surgoshan,

Actually, you’ll have to start by debunking Newton. The limits on being able to get anywhere quickly come more from the huge amounts of energy required to get up to a high speed and not from being unable to go faster than c.

Ahh, but note that I titled the thread PRACTICAL rather than POSSIBLE. What would motivate a large group of people to spend the effort to send a manned mission even to AC, much less a mission to a farther star or even a colonization mission?

Wally M7,

While I agree with most of what you said, I think that by the time interstellar travel is possible we will have mastered the technology for living in artificial orbiting habitats. If you’ve got the technology to build sustainable orbital environments (which you pretty much need to get to another star in the first place), you don’t need any Earthlike habitable planets. Of course, you do still need some gas giants and some rocks, so you’ll want to send an unmanned probe first, and spend one or more generations waiting to hear back from it before setting out.

Kevin Allegood,

“At least one could get something through Trotsky’s skull.”

  • Joseph Michael Bay
18

Where’s my part?
God forbid we might be in agreement about something.

Often wrong… NEVER in doubt

19

One light year is 5,865,696,000,000 miles. Alpha Centuri is what, 4.3 light years away? Or roughly 24 trillion miles. So even at a million miles an hour it would take 2700 years to get there. Ok, not quite 30,000, but it’d take awhile to get up to speed. I’m not sure what our rockets can do, but if someone wants to show some numbers, I’d be glad to see them. And by current technology, I mean stuff we actually use today, i.e. rockets/gravitational slingshots.

As far as getting to Mars, I think it is a wonderful idea, and I always thought it would have happened by now. Returning to the moon and setting up a base there is an important step in our conquest of the solar system. Unfortuneately, there is no political pressure to do so, and unless Bill Gates wants to fund it, it will likely be the politicians who control the funding. Such a shame. :frowning:

It’s not how you pick your nose, it’s where you put the boogers

20

Time for fun with Mars!
Bantmof,

Ahh, but ultimately is not the same thing as anytime soon. The fact that something would be good a long way down the road doesn’t mean that there’s any reason to do it now.

Hardcore,

Exactly why should we do it NOW? A lot of what I’d call ‘space advocates’ insist that we need to undertake huge long-term projects NOW, but there don’t really seem to be any reasons for them. This, IMO, actually hurts any potential space program, since it gives someone ‘on the fence’ the impression that the only reason to go into space is because someone else really likes the idea.

Scylla,

No they’re not. What, exactly, are the benefits to creating a Mars base, especially a ‘more or less’ permanent one (which doesn’t sound self-sustaining)? The only reason for these projects seems to be ‘because I’d like to’. With the sheer cost of these projects, ‘it would be nice to have’ really doesn’t cut it.

Kevin Allegood,

“At least one could get something through Trotsky’s skull.”

  • Joseph Michael Bay