Bad News: Interstellar Travel May Remain in Science Fiction

by Ian O'Neill on August 19, 2008

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The Daedalus star ship, proposed in the 1970s, would propel itself forward using controlled fusion explosions (Nick Stevens,

The Daedalus star ship, proposed in the 1970s, would propel itself forward using controlled fusion explosions (Nick Stevens,

Some sobering news from a recent rocket science conference: It is highly improbable that humans will ever explore beyond the Solar System. This downbeat opinion comes from the Joint Propulsion Conference in Hartford, Connecticut, where future space propulsion challenges were discussed and debated. It is widely acknowledged that any form of interstellar travel would require huge advances in technology, but it would seem that the advances required are in the realms of science fiction and are not feasible. Using current technology would take tens of thousands of years, and even advanced concepts could take hundreds. But above all else, there is the question of fuel: How could a trip to Proxima Centauri be achieved if we’d need 100 times more energy than the entire planet currently generates?

In a previous article on the Universe Today, I explored how long it would take to travel to the nearest star using the slowest mode of transportation (the ion driven 1998 Deep Space 1 mission) and the fastest mode of transportation (the solar gravitational accelerated 1976 Helios 2 mission) currently available. I also discussed the theoretical possibility of using nuclear pulse propulsion (a series of fusion bombs dropped behind an interplanetary spaceship to give thrust), much like the 1970′s Daedalus star ship concept (pictured top).

Unfortunately, the ion drive option would take a whopping 81,000 years to get to Proxima Centauri, our nearest star, and using the Sun for a gravitational assist would still take us at least 19,000 years to reach our destination. That is 2,700 to 600 generations, certainly a long-term commitment! To put these figures into perspective, 2,700 generations ago, homo sapiens had not developed the ability to communicate by speech; 600 generations ago the Neanderthals had only recently become extinct. The nuclear pulse propulsion option seems far better taking only 85 years to travel to our nearest star. Still, this is a very long trip (let’s hope they’d offer business class at least…).

Already there are huge challenges facing the notion of travelling to Proxima Centauri, but in a recent gathering of experts in the field of space propulsion, there are even more insurmountable obstacles to mankind’s spread beyond the Solar System. In response to the idea we might make the Proxima trek in a single lifetime, Paulo Lozano, an assistant professor of aeronautics and astronautics at MIT and conference deligate said, “In those cases, you are talking about a scale of engineering that you can’t even imagine.”

OK, so the speed simply isn’t there for a quick flight over 4.3 light years. But there is an even bigger problem than that. How would these interstellar spaceships be fuelled? According to Brice N. Cassenti, an associate professor with the Department of Engineering and Science at Rensselaer Polytechnic Institute, at least 100 times the total energy output of the entire world would be required for the voyage. “We just can’t extract the resources from the Earth,” Cassenti said during his conference presentation. “They just don’t exist. We would need to mine the outer planets.”

For mankind to extend its reach into the stars, we need to come up with a better plan. Even the most advanced forms of propulsion (even anti-matter engines) cannot make the gap seem any less massive. Suddenly the thought of a warp drive seems more attractive…

Original source: Wired


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Hello! My name is Ian O'Neill and I've been writing for the Universe Today since December 2007. I am a solar physics doctor, but my space interests are wide-ranging. Since becoming a science writer I have been drawn to the more extreme astrophysics concepts (like black hole dynamics), high energy physics (getting excited about the LHC!) and general space colonization efforts. I am also heavily involved with the Mars Homestead project (run by the Mars Foundation), an international organization to advance our settlement concepts on Mars. I also run my own space physics blog:, be sure to check it out!

Torbjörn Larsson, OM August 21, 2008 at 1:19 PM

Or as some here have done, simply showing that their power requirement criteria is wacky.

Oh yes, I was so in need of coffee – of course that was supposed to be “as some here has attempted”.

quantum_flux August 21, 2008 at 1:36 PM

Just don’t exceed 3 G’s for too long and don’t ever ramp it up past 16 G’s because people tend to get queezy and then faint from tunnel vision…. nah, 85 years with nuclear pulse propulsion isn’t that bad, so don’t be pessimistic. Similarly, antimatter goes even faster. Ultimately though, warping spacetime via light wave manipulation looks to be optimistic….

The First Time Machine

Torbjörn Larsson, OM August 21, 2008 at 1:42 PM

Third, the theories of using dimensional warp drives or FTL drives are simply theories that do not relate to the physics of our world as we currently understand it.

There is every reason to believe every such proposal is a dud. For example, Scott Aaronson in his papers and lectures gives the basis for assembling the following anthropic argument against:

We observe ourselves to live in a physically interesting world (say, with the ability to have dust and so planets and life). The reason it is interesting is that P ≠ NP (or we and the universe could solve all NP problems simply, so no string landscape et cetera). The reason that P ≠ NP implies we can’t have closed timelike curves, CTC (or time would be equivalent to space as computational resource, and we could solve all NP complete, i.e. finite solution space, problems using finite time over and over). This would explain both why we observe that time has negative signature (i.e. is unidirectional) and why there aren’t any observed CTC.

@ Benduha, ulgah:

It’s clear, at least to me, that we are indeed stuck here to this solar system, and anyone who thinks otherwise is in denial.

You keep saying that. But as your only basis is an argument from incredulity fallacy, it seems to us others that the denial is on your side. The post presents a real argument, isn’t that enough for the time being? Perhaps it is correct, perhaps not – but at least it is testable.

Yael Dragwyla August 21, 2008 at 9:29 PM

Damian –
Great post, *but*.
“(Making a spaceship out of an Asteroid) In the absence of (verifiable) proof of advanced technological species capable of Faster then Light travel. And in accordance with our (Emerging) understanding of the laws of nature. (as pertaining to the universe we inhabit) Its my thought that the best possible spaceship we could build would be one modeled on nature. In that I mean the planets and moons within our solar system’s gravity well.”

Depends on what you mean by “modeled on nature.” If *anything* can be done, it’s natural, a rather trivial tautology. On the other hand, lots of our accomplishments, such as, e.g., the internal combustion engine, use phenomena found in nature and put them together in ways found nowhere else but among us. Once upon a time it was believed that if people went faster than 40-50 miles per hour, they’d be killed by it. Now we know better — the problem is *accelaration*, not velocity. Plus, FTL and similar potential phenomena may in fact be possible, but we haven’t yet run across examples of them.

“A planet is a space ship. In fact a very good one.” A tailored asteroid or small moon could be an even better one — you could tuck millions of people into it and still have plenty of space left over for wildlands, farms, etc. And it has far less inertia to overcome.

“I, like anyone else am excited about the idea of FTL travel, but I do have to wonder if such a concept is really possible. Notwithstanding our lack of understanding about the nature of the universe and physics, it strikes me that any attempt at such a technology has to work outside the fundamental laws governing the universe.”

See comment above, at top.

“Lets put it this way, if such things were possible, then nature (by accident or design) would have presented an example. I also hope for a astounding breakthrough that (might) at some point in the future make this possible. However the future is not yet written.”

See comment, above, concerning going faster than 40-50 mph. Those who believed we couldn’t go any faster than that had never seen a cheetah in action, apparently. So far, anyway, the rule seems to be: if you can imagine it, it can be accomplished. It may take quite a while to realize it, but that doesn’t mean it’s not possible. And while we’re at it, consider quantum connectedness, a real phenomenon that “violates” the speed of light. Physicist Michio Kaku is on record as saying that eventually we’ll be using all those “weird” phenomena — quantum connectedness, etc. — to accomplish FTL, etc.

“IF, as a species we wanted to travel in space now, it will take a long time. If its going to take a long time then we need spaceships modeled on the best examples nature can provide.”

You’re a fortune-teller? You are using precognition to come up with that? If so, precognition is real — and maybe we can harness it to get where we want to go.

Never, ever say “never.” :-)

Yael Dragwyla August 21, 2008 at 9:44 PM

One other thing that should be mentioned: Earthly life doesn’t have eternity on our world for its remaining existence. Above all, *we* don’t have an endless future here to play with. If interstellar travel really *is* impossible, Earthly life — including us — is irretrievably messed up (there’s a better, more succinct term for that, but I don’t want to use it in police company), with no place to go and no way to get there — eventually the Sun will expand and fry all life that is still on Earth. In the meantime, catastrophic global warming, perhaps strenuous to turn our planet into something like Venus, is more likely than ever, because our day-star gets hotter all the time, adding to the potential for such a catastrophe — a quarter of a billion years ago, as near as state-of-the-art climate science can make out (see, e.g., Peter Ward’s brilliant UNDER A GREEN SKY: Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us About Our Future (, for a discussion of the PermoTriassic mass extinction event and its relevance to us now), catastrophic global warming almost exterminated all complex life on Earth, and a hotter Sun can only add to that horrific possibility. So if we can’t find our way to the stars, somehow, some way, you can kiss Earthly life — including Homo sapiens — goodbye.

Hunnter August 21, 2008 at 3:04 PM

Aodhhan, the engines don’t always need to be online.
Once the ship is at speed X, they can be shut off and scanners can check for location every few weeks to make sure it isn’t going off track.
And not only that, they (whatever agency embarks on this) could use solar energy to constantly send a beam towards the ship, cutting down on a bit of the fuel requirements.

Also, remember that weight doesn’t mean anything in space.
There is no way anyone would ever attempt to build a ship on Earth if it contains colonies and whatever. (unless it is assembled over a very long time and put together similar to ISS)
The only way would be if it never had any life on board outside of DNA samples which could be grown near its destination. (but still, the area will be small, and the nearest star, as far as i know, has no planets capable of life as we know it)
Plus, this is much safer in terms of psychology, nobody to go insane, and of course, Gs experienced too. (none as well)

Markus Demetrius August 21, 2008 at 4:24 PM

Anybody read ‘Learning the World’ by Ken Macleod? It’s about us, in the future, colonizing the galaxy, no ftl drives. Some good science has come out of SF, mainly because of “outside the box” thinking.

Tyler Durden August 21, 2008 at 5:27 PM

“Hence the lack of visitors to what must seem to be a quite interesting planet implies to me either that we are alone in our galaxy or that travel is impossible.”


Not really. Earth may seem an uninhabitable wasteland to intelligent species of a different evolution, and thus no point in visiting it.

We wouldn’t send a ship to a system with no habitable planets. We’d observe that system with telescopes, but never go there.

“Although, almost all theories of FTL travel would reverse the arrow of time, right?
So, essentially, as you travel out to a star in the sky, you are going back in time.
And to balance it all out, you’d arrive at the same point in time as you could see in the sky.”


Interestingly enough, if you were to travel 40 light years at FTL speeds that got you there in ten hours, you could turn around and with a powerful enough telescope you could look and see the surface of the Earth 40 yrs ago (minus ten hours).

Imagine the archaeological benefits.

You couldn’t “time travel” though – if you returned to earth it would just be August 21,2008 launch time + 20 hrs.

Tyler Durden August 21, 2008 at 5:29 PM

Basically to clarify you aren’t reversing time’s arrow. Time remains the same locally, always. You’re simply travelling faster than light travels, which means the light that hits your telescope took 40 yrs longer to get to the spot you’re at than your ship did.

Wormholes on the other hand * could * be used for time travel, if they exist or could be created, and are traversable.

Hunnter August 21, 2008 at 6:10 PM

Oh wait, nevermind, i was actually meaning that with wormholes.

Although, even if they existed, i still don’t think they could be of much use.
You are still going into a blackhole in the end.
The “tunnel” could be filled with massive amounts of radiation for one.
And of course, gravity could potentially still reach into it (can’t really see how it wouldn’t to be honest)

You’d maybe be able to send electromagnetic waves, if the tunnel was a perfect “cylinder”, just send it through the center.
Although, even that might not work.

Molecular August 21, 2008 at 10:54 PM

Let’s talk about babies here for a moment. When a child is born they only know what they see around them. They see colors, they feel warmth and cold, they know hunger and know when they are full.

A child, observing the world that surrounds them, begins to understand his or her place through constant observation. Over a period of time, what never made any kind of sense, gradually begins to make sense, and so the child begins maneuver it’s way through a world that was, at first, a total mystery.

While scientists spend so much time observing the Universe, like the child, they see the black holes, the quasars, the flashes from GRBs, etc., all the mysteries that are contained within, and because they are so young in technological terms, can’t yet grasp that some of what they study, may in fact, be the work of highly advanced civilizations.

So, as babies of this great planet Earth, we can’t yet even begin to understand the prospects of the adult minds that govern the Universe.

Something to think about. :)

dollhopf August 21, 2008 at 11:01 PM

Here is another recipe for lightweight space colonization:

Buy some high quality human eggs and sperm from a sperm bank. Put them into a mobile cooler. Send them with a standard space vehicle in direction of the star of your choice. At arrival let the trip computer touch down the vehicle on a promising planet or moon in sunlight and with water ice nearby. Then activate the resource collector units.

Now switch on the medic robot to defrost and stir up the basic human modules. Put it all into the breeding reactor. Meanwhile boot up the nurse robot and the training equipment to teach the “result” how to send SMS about what’s up from time to time.

Damian August 22, 2008 at 1:45 AM

hmmmmmmmm(Worm Holes) anyone?

Derek August 22, 2008 at 11:31 AM

Of course it’s just speculation right now, but I can think of a way that might put that “highly improbable” claim into question:

If nanotechnology delivers on its promise over the next 2-3 decades, then we should be able to create a tiny package (perhaps microscopic) that consists of replicators and blueprints for a radio-based communications receiver.

The tiny package could be sent to a planet outside of our solar system for relatively little cost, and probably take a few decades or so to arrive.

Once there, the replicators could reproduce using the available soil and air. When they had sufficient numbers, they could switch to become assemblers, which would use the blueprints to assemble the communications receiver.

Back on Earth, we would use disassemblers to disassemble a group of humans to essentially turn everything they are into digital media (if that’s even necessary, considering robots should exceed human capacity in all areas around that time, and their minds should already be digital).

We would then beam that information (at the speed of light) to the receiving station on the exoplanet, where the assemblers would reconstruct human (or robot) bodies for the disassembled travelers.

The assemblers could also have a whole comfortable town already waiting for the travelers’ arrival. Perhaps even terraforming, if necessary.

Thus…relatively little cost to send a small package too a planet at high speed to assemble a receiving station for “teleported” Terrans, at no risk to human life.

Sagarika August 22, 2008 at 5:58 AM

How about the dark matter be used for the purpose….lol

Ken Kachur August 22, 2008 at 7:32 AM

A wise old man(104 years young) told me prior to his death he witnessed it all from horses for transportation to witnessing the first man on the moon. With this being said I don’t believe as a very inquisitive race we will be destined to remaining on this planet earth. We will in time reach out to the stars. I was just born 100 years too soon.

Alex August 22, 2008 at 9:40 AM

Although an interesting article, I have one problem with it: it only focuses on currently available propulsion systems. What about an Alcubierre drive? Just because we can’t build one now, doesn’t mean that we can’t build one 50 years or 100 years from now. With the current state of propulsion systems I agree with this article because if we could make it to Proxima Centauri, I imagine that we already would. However, with the rate of technology advancing faster and faster, I have no doubt that we will find a way to travel to other stars.

dollhopf August 22, 2008 at 8:03 PM

Markus Demetrius Says:

“Religion caused the dark ages. We would be 1000 years or so more advanced than we are now … probably cruising the stars”

I don’t think so. Theories of Modernization achieved a different insight in what “Dark Ages” are caused by. There is also evidence that religion supports and contributs to something that we call progress. You just need a little bit of good will and creativity to investigate this by yourself and thus saving me an amount of time to do it for you. Have you ever read the passage in Hemingway’s “For Whom the Bell Tolls” in which the “revolutionary” horde kills the priest with their scythes? “Dark Ages” are a more complex subject than to blame only one factor. I don’t want to play down the bad implications of religion. I just want you to realize also the advantageous aspects.

“We” (others did that for you – you only need to take care for the persistance of it) established societies that are based on and organized with Rationality. I do believe that personal moral rotting is a basis for the corruption of a society and that corruption leads to decay and that decay is a form of “dark age”. I also belief that one or the other form of personal religiosity is a medicine which heals rotting.

Markus Demetrius August 23, 2008 at 12:11 AM

dollhopf – I totally agree with all that you’ve said, just one question – how does any of it disprove the fact that religion has held us
back thru the ages?

Archeological digs show that the temple preists, of many cultures, have always had the highest level of local technology, most always used in ways to trick the locals to think that they had “powers”. This has been going on for thousands of years, and the only challenge to the priests has been knowledge, and thus the banning of knowledge. Why was Latin the official language of the Catholic Church for so long? Because most locals had no idea what “God” wanted, but the priests could fake it. Galileo and Copernicus’ persecutions come to mind only because they’re (relatively) recent. Earlier, religion had a lot stronger hold on everyone! Believe or die was the rule for thousands of years, and you delude yourself to think that religion hasn’t held back the technological development of our species by many thousands of years. There is no greater EVIL than religion. Period. You can dress it up with lot’s of feel-good, but that’ll never change its true nature…Evil.

Damian August 23, 2008 at 1:07 AM

In my post I mention that we should use nature as a Model for our spaceship designs

Yael Dragwyla Says:
August 21st, 2008 at 9:29 pm
>Depends on what you mean by “modeled on >nature.” If *anything* can be done, it’s natural, a >rather trivial tautology.

My wording is a intended as an axiom. To define something as natural is somewhat trivial I agree.

So I would like to define is just a little more.

I think, we should build spaceships that are an anagram of a planet. This is a design that is obviously working well. (life on earth has survived so far) .

IF we intend for humans to travel in space, then our spaceships will need to support biological life over long periods. The best (observed) model that we have is our own biosphere. Building Metal boxes as living spaces for humans is the wrong direction. (physiologically and physiologically)

Perhaps Bubbles of water would work well as a spaceship.? Certainly provide a huge degree of protection against the solar weather. A fusion reactor as a core, Habitable spaces built on top of the core. The water can be rich in Algal nutrients for oxygen and food. Even as sources of chemical fuels to provide propulsion.

My idea is a bit left of center, and its probably as much pie in the sky as FTL travel. However, even for exploring our own solar system. The idea of creating a (slow moving) Bioshere in space capable of supporting human communities that is modeled on our own planet makes sense. (at least to me)

As I mentioned previously, the three essentials are heat, water and a Magnetosphere. Without these elements any travel into space is probably better carried out by autonomous or remote means.

Little Planets? :) I’m not a scientist, just a person with a vivid imagination. But I do think we are going about this the wrong way. Because it costs so much energy to escape our gravity well, we want our spaceships to have as little mass as possible. I think this is wrong. Our spaceships need to have (a large) mass. Enough mass in fact to have their own gravity.

But then here is the Pie in the Sky part, which is using gravity as a means of propulsion.Shaping the magnetoshere to use as a solar sail is one idea. Being able to shape the eleactrical currents that interact with the solar medium is another.

>You’re a fortune-teller? You are using >precognition to come up with that? If so, >precognition is real — and maybe we can >harness it to get where we want to go.

Not quite sure what you mean, I’m certainly no seer, or mystic. Skeptic would be more like it.
One thing that does fascinate me is the idea that by observing and trying to understand the universe we are changing it. (insert obligatory schrodinger’s box comment)

However this insight from particle physics is as hypothetical as a unified theory for everything. (in my opinion)

Understanding gravity is the key if we want to travel in space. (LHC is our great hope) This certainly is an interesting time to be alive.

BTW, A thank you to Ian O’Neill, i have been visiting and reading this site for a while now. Great work.


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