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Bad News: Interstellar Travel May Remain in Science Fiction

The Daedalus star ship, proposed in the 1970s, would propel itself forward using controlled fusion explosions (Nick Stevens, www.starbase1.co.uk)

The Daedalus star ship, proposed in the 1970s, would propel itself forward using controlled fusion explosions (Nick Stevens, www.starbase1.co.uk)

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: Astroengine.com, be sure to check it out!

Comments on this entry are closed.

  • The Null Dragon August 20, 2008, 1:57 PM

    “Any sufficiently advanced technology is indistinguishable from magic” Arthur C. Clark.
    In my lifetime I have seen much “magic” and I am certain future generations will see it also

  • YOGIH August 20, 2008, 2:19 PM

    why wouldn’t we channel our energy towards other more important things, logical steps that have to be taken Before thinking of any manned trip to another planetary system: like building thoe giant mirrors/telescopes on the Moon or/and other natural satellites of Saturn, Jupiter and so on, to allw first to SEE those Earth sized exo-planets around other stars, and only then, based on the available resources and technologies to plan/talk about posibility to reach those far far away planets. Personally I believe that for humans anything slower than half of light speed will not worth the interest for manned missions. Probably if we could build an “army” of self replicating and self-sustainable super-intelligent robots and send them to explore the whole galaxy at once and send information to Earth… just a tought

  • ulgah August 20, 2008, 2:20 PM

    I watch with interest all the time and find it a waist of my time to argue with most of you, smart people, LOL. This is one of the most interesting and truthful, articles, according to my minimal knowledge, that I have seen in a long time. I have believed this for a long time, But trying to talk to all you dreamers, just frustrates me. I believe most of you are Ufologists. I sympathize with you dreamers, but realism must at some point be realized. I am not much of an articulate r, that’s why I am poor! But if you want to know what I think of this article, please check this post:

    Benduha Says:
    August 20th, 2008 at 8:25 am

    Since it’s highly unlikely we’ll ever be able to travel to other stars, it’s equally unlikely that aliens have ever been here, or ever will be here in the future.

    I’ve been saying this all along though. I just don’t think people realize the distances involved here. And we’re only talking the nearest star, but what about traveling beyond that?

    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.

  • BigJon August 20, 2008, 2:22 PM

    what a load, zero point energy, tesla come on people, traveling without moving, this is only one persons view, good luck! thats not my future.

  • Cynthia August 20, 2008, 2:39 PM

    @Benjamin Horrendous Says:
    “August 20th, 2008 at 8:10 am
    Nobody read Non Stop by brian Alldis?”

    Was that written before or after the old TV show Star Lost???

    For the world is hollow…and I have touched the sky!

  • Yael Dragwyla August 20, 2008, 11:18 PM

    I keep thinking of the head of the US patent office who, at the end of the 19th century, declared that “everything that can be invented, has been invented,” and wanted to lock up the patent office and call it a day. I think that’s what we’re seeing here — a sort of constitutional pessimism with which some people are afficted, that directs them to reject anything new and applications stemming from it before we even know it. There’s always the asteroid-turned-space-habitat sent outward bound at a constant velocity — or even a slightly accelarating one, powered by sunlight — stocked with a good cross-section of Earthly life, water, the whole monty. By initially aiming so that at its velocity (and any accelaration thereof) such that it will cross the path of some stellar system before, say, 100,000 years have elapsed, that may do the trick. I’m betting, however, that we come up with something *much* better than that within the next 50 years. In the last two hundred years we went from sailing ships, railroads, and cross-country travel via Conestoga Wagon to Earthly life’s first tentative steps off-planet, and technological progress is still accelarating exponentially. “Never say ‘never’ ” is still an excellent piece of wisdom.

  • Hunnter August 20, 2008, 5:31 PM

    Ulgah, you are obviously pretty clueless.
    Hell, you even admitted to have little knowledge, so anything you say is already null.

    Anyone who ever tries to say something is impossible is small-minded, period.
    The fact that these people said it is pretty damn insulting to science in every respect.
    Do they have some sort of time machine? Oh wait, that is probably impossible too, right?

    It is entirely possible to travel to other stars.
    Build a spaceport.
    Harvest rocks in space for materials (google apophis, if someone captures that, it will be a “godsend” to space ports.)
    Build a large colony. (specifically, Damians idea was nice, simpler too)
    Add a cold fuel store. (maybe even collect some on the way out into the Oort cloud)
    Get some life stored on there. (whether living, or DNA storage)
    Send it on its merry way.

    While WE might be stuck here, our children could easily make it there in their lifetimes, if time and resources were commited to this.
    This is where it probably won’t happen, in our childs liftime that is, not “never evr happening ever, gt a live dreamers”.
    So please let the adults converse.

  • Thomas S. August 20, 2008, 5:50 PM

    There are some important points here, with regard to the scale of engineering or the massive amount of fuel required. But I think it’s hasty to say that it’s highly improbable humans will make it to another star system.

    It will be a long time from now before any sort of intersteller mission is possible, but humans are always finding ways to use more and more energy.

    I’m thinking of a relatively modest probe on a flyby at say, .1c. Sending humans there to set up camp is a whole other story and may be many more centuries down the road.

    Beamed propulsion looks promising, as it moves the propulsion problem onto a nice large place on the “ground” as opposed to the probe itself. I imagine it can be combined with other propulsion methods as well. The other near-future propulsion method I was thinking about that was likely being discussed in the article, was fusion propulsion. Specifically, using Helium-3.

    We’ll only ever end up embarking on such a mission if we have infrastructure in space already to assemble an interstellar probe. Hopefully space tourism will take off and increase the amount of stuff that goes on up there, maybe we’ll even start mining for He-3 to use on Earth and from then on, figure out ways to use it for propulsion.

    We may just work our way up to an interstellar mission in a few centuries or less. But if our presence in space is the same as it is today, I somehow doubt that.

  • dollhopf August 20, 2008, 11:32 PM

    “Unfortunately, the ion drive option would take a whopping 81,000 years to get to Proxima Centauri, our nearest star”

    speed of Voyager 1 = 3.6 Astronomical Units/year
    63,024 AU’s = 1 lightyear
    distance to Alpha Centauri = 4,34 ly’s
    time of travel -> 75.980 years

    Voyager 1 is not accelerated. So why then should an ion drive need “a whopping” 5000 years more?

    “at least 100 times the total energy output of the entire world would be required for the voyage”

    Upps … why that? Voyager 1 never needs that much energy to do the journey.

  • John August 21, 2008, 12:35 AM

    HELLO out there! Anybody home? So many of you are missing something quite important in this discussion…

    It is an UNDENIABLE FACT that there have been over 100,000 sightings of unknown craft in our atmosphere over the last 60 or 70 years. Many astronauts, civilian and military pilots, radar operators, policeman and reputable people have reported UFO’s in great detail. Please don’t tell me EVERY SINGLE ONE is a misidentified natural occurrence!

    If just ONE of these almost countless events is real, then there is little option but to conclude that inter stellar travel is not only possible but the evidence is clearly in front of our noses.

  • Markus Demetrius August 21, 2008, 12:53 AM

    We’ve only been in space 50 years – how close-minded of Ian O’Neill to make pessimistic predictions? Hell, our physicists readily admit that we only have a slight handle on 4% of matter/energy.

    Religion caused the dark ages. We would be 1000 years or so more advanced than we are now, and probably cruising the stars on vacation, if it weren’t for our propensity for feeble-mindedness and superstition. The Earth could be destroyed at any time, look at the violence in the cosmos. Religion is our enemy if we ever hope to escape this planet to ensure our survival as a species. Hell, you can’t even get elected to public office in most democratic countries unless you (at least say you) are religious and believe in ghosts, spirits, and demons…Oh My!

    So far, all we know about physics is from scientific experiments conducted within the gravity well of Sol. Also, it may well be that Sol’s heliosphere is shielding us from forces/energies that we haven’t even dreamed of. Spending our limited, and diminishing, research budgets on baby steps like a moon base or looking for microbes on Mars are the types of “WOW” missions thought up by religious types to hold us back – these missions are actually not very technologically challenging, thus will have few spinoff benefits and will eventually lead to calls of “folly”. We now have a space station, so what? Will soon have a moon base, so what?

    We are a stubborn species. Once we believe something is possible and worth doing, it gets done. Unmanned missions which were designed to conduct experiments, position telescopes covering the spectrum, and return data from far outside our heliosphere would provide a host of problems to solve, true challenges, but not as difficult as reaching across interstellar distances. The solutions to these obstacles (which we would find) would provide new technologies which would revitalize the world economy. There would almost certainly be payoffs just from the “doing” of it, even if we learned nothing new scientifically once the instruments were in place out there.

    However, just possibly, we might find that we’ve been looking at the universe with blinders on.

    As a plus, we’d have push propulsion technology and developed the ability to place instruments far enough away to actually use the gravitational lensing of Sol as (possibly) the largest telescope ever conceived. Possibly, I say. My point is that we need actual challenges if our space program is to eventually pay for itself. We went to the moon forty years ago, and NASA wants to use a lot of “proven Apollo technology” to do it again. Boring…a money pit…been-there-done-that…the “daring vision” of an illiterate president.

    Our goal should be to pop outside our heliospere and take another long look around. Like Kennedy said about going to the moon back in the ’60’s, “do it not because its easy, but because it’s hard”.

    For the interstellar pessimists, there are many generation-ship possibilities. I doubt we’d notice the spinning (simulated gravity) in a large enough asteroid, and slowly boosting many huge asteroids in tandem would eliminate the resource-depletion, “obvious” breakdown (really?) problems described by naysayers.
    Future generations inside such ships will think of the ship as home and probably not even slow the ship upon reaching the target star, just send miners ahead to scavenge for new asteroids/resources and boost them up to speed (may take centuries to rendezvous, who cares?), advance parties/probes to determine if the planet is habitable , then send colonists to the planet as they shoot on by at relativistic speed, and continue on to more stars, slowly gaining speed over the centuries.

    O’Neill describes Proxima Centauri as a target. He hasn’t even the vision to realize that within decades (if not this one) we will have pinpointed Earth-like planets and will simply have to choose those most likely.

    DNA adaptation to weightlessness life inside comets would allow us to slowly expand throughout the galaxy, Oort cloud hitchiking. Such DNA modifications may not be that far off if we can keep the superstitious at bay. Who are they to say that we can’t tinker with the human genome? I for one would love to play “God” if it were to help preserve the species, and no religious moron has the right to impose their medeival “morals” on the rest of us and slow down our progress any more than they already have!

    We’re still new at it, and yet we’ve got many SLOW ideas of leaving this gravity well that are at least possibly feasible. With a little more emphasis on pure science research instead of bombs, we’ll have a lot more ideas sprouting forth, maybe even FASTER ideas, but the religious types do love their bombs. So, even though I’m optimistic that we CAN do it, I think superstition will hold us back far enough that our species won’t make it off this rock before it becomes uninhabitable.


  • Damian August 21, 2008, 3:25 AM

    Thank you all who considered my idea to be a interesting one. (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.

    A planet is a space ship. In fact a very good one. Our solar system is an even better one. We have a star as the engine, a series of planets as a steering mechanism, and enough abundant resources and fuel to take it anywhere we like in the universe. (just have to figure out how to steer it :)

    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.

    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.

    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.

    Thats the planet earth. A Spaceship with a Magnetosphere, and the essentials for biological life. Water and Heat.

    First step, Magnetosphere, also a focus of research for alternative propulsion.


    The Problem with planets created by nature is that we have no control over the mechanics of the molten core that generates a Magnetosphere. However if we were to build one, the possibilities of using the plasma as both a shield and a form of propulsion are reasonably viable.


    Id start with a Small asteroid first, but converting a moon into a spaceship would be the next logical step. Take Europa for instance, already has a molten core and abundant water. (so its believed to date)

    Control the gravity of a body with enough mass, and you have a spaceship.


  • andrew guthrie August 21, 2008, 5:07 AM

    If there are technological civilisations alsewhere in the galaxy then it is reasonable to suppose that at least one of them would have been able to develop to a level a few hundred to a couple of thousand years ahead of where we are now. It has taken us the blink of an eye to get from pre-electric power to our current level, and IF interstellar travel is possible at all we would surely discover the secret within those time scales or not at all. 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.

    In any case, if these journeys are to take a lifetime or even several generations, what sort of life would it be possible for anybody to have, entirely within the confines of a ship, notwithstanding there would be very little to do when you got there?

  • Sheets August 21, 2008, 6:12 AM

    Uh huh. And 250 years ago people were convinced a steam engine would never go faster than a horse. Now we consider dropping atomic bombs behind spaceships. What a horrible attitude from that conference. All those smart people in the same room, but not an optimist to be found? Ok – let’s give up on that bunch. How about for the next conference don’t invite a single one of those attendees back. After all, there’s nothing left to talk about. Bring in new people.

  • R2K August 21, 2008, 7:14 AM

    Fenring says:

    “suffer at the cruel hand of theory of special relativity (time dilation: you get there quickly only to find out that everywhere else hundreds of years have already passed).”

    That is actually a good thing. If we could go that fast (which is even harder than the things we are discussing now), time dilation would be an ideal form of time travel. If you can accelerate at 1 g constantly, you can travel across the universe because time dilation would greatly reduce the time that you see. The fastest particles can travel cross the universe in months local time.

    Also, who ever said the trip would be anything but one way? Going to a star then coming back is far harder than simply going there.

  • Astrofreak August 21, 2008, 7:30 AM

    Hmmm, looks like no one is close to getting a patent on their warp drive engine! Hard to believe, a story on this website that is actually realistic for once.

  • Hunnter August 21, 2008, 8:18 AM

    I always thought the same R2K, it would be pretty good to travel that way.
    Plus, who knows, by the time you arrive, there could well be some dude waiting there with some wine. 😉

    Also, on the FTL topic and looking into the stars is looking back in time, people wonder if that could cause problems.
    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. (in theory at least)

    Hopefully LHC will provide some more answers.
    (come onnn Graviton! )

  • Gabriel August 21, 2008, 8:45 AM

    “No need for derogatory and unsubstantiated implications”

    The site administration will decide what is or is not needed i believe and you are not a part of it.

  • Greg August 21, 2008, 10:08 AM

    I think this shows a surprising lack of imagination on the part of the scientists at the conference. To a rocket scientist of course it seems impossible to reach alpha centauri using chemical rockets considering the cost of bringing your own fuel. A few simple ideas however could radically alter the equation. Ram scoop engines that burn fuel found along the way is one. Solar sails which could also be remotely powered by lasers at a considerable distance would be another. Power generation could be greatly enhanced to power such lasers if we really wanted to do it. A combination of approaches, especially using ultra light anti-matter fuel could also be employed.

  • Aodhhan August 21, 2008, 12:18 PM

    Knowing how, and being able to do something are 2 very different things.
    I know, if I can disassociate all the atoms in my body, move them independently a few feet, with a minor wind draft and have them know how to re-assemble back together within 4 minutes… I can pass through a wall and live.
    Impossible?Maybe not. Improbable?.. yes.

    If a caterpillar had a machine gun, a bird wouldn’t try to eat it.

    No matter what source you use (coal, gas, anti-matter, the crystal of bang-bang) the amount of energy required is still the same, and this amount is ENORMOUS!
    You are talking about not only releasing, but controlling all this energy. The energy of every home, business, automobile, plane, gas pump, communication equipment, conventional munitions, water pump, currently generating power plants, solar and wind power.. not to mention each and every little tactical and strategic nuclear weapon, etc etc etc. at once!

    The spacecraft will require a powerplant and source which runs constantly for decades; at best years. Anti-Matter engines would require 60 BILLION TONS of fuel (Hydrogen.. can you imagine 60 billion tons of hydrogen?) at minimum and take 40 years. This is just the power plant alone.
    Every day in space you need breathing air, water and food; of course something to do (you just going to sit in a chair?). Think of the amount of room/weight food and water alone take up, let alone fuel. Need spare parts for everything, probably at least 3-10 for anything which is a moving part… yeah, that doesn’t take up space. Anti-matter engines require huge magnets and an even more elaborate cooling system.
    Oh yeah, you’ll probably need at least 2 or 3 mini nuclear plants for internal power. Can’t count on one making it. More weight and parts.

    So lets say we made it, we are crusing at 0.8 speed of light… man that is fast.. and all those objects, asteroids, ice rocks, even little bitty dust particles out there going 40,000+ mph, zip zapping through the cosmos. Don’t hit one!

    This is just a tiny bit of the engineering to deal with. I can go on.

    Those darn scientists. They have no imagination!