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Project Icarus: Contemplating Starship Design

Andreas Tziolas, current leader of Project Icarus, gave a lengthy interview recently to The Atlantic’s Ross Andersen, who writes about starship design in Project Icarus: Laying the Plans for Interstellar Travel. Icarus encounters continuing controversy over its name, despite the fact that the Icarus team has gone to some lengths to explain the choice. Tziolas notes the nod to Project Daedalus leader Alan Bond, who once referred to “the sons of Daedalus, perhaps an Icarus, that will have to come through and make this a much more feasible design.”

I like that sense of continuity — after all, Icarus is the follow-on to the British Interplanetary Society’s Project Daedalus of the 1970s, the first serious attempt to engineer a starship. I also appreciate the Icarus’ team’s imaginative re-casting of the Icarus myth, which imagines a chastened Icarus washed up on a desert island planning to forge wings out of new materials so he can make the attempt again. But what I always fall back on is this quote from Sir Arthur Eddington which, since I haven’t run it for two years, seems ready for a repeat appearance:

In ancient days two aviators procured to themselves wings. Daedalus flew safely through the middle air and was duly honoured on his landing. Icarus soared upwards to the sun till the wax melted which bound his wings and his flight ended in fiasco. The classical authorities tell us, of course, that he was only “doing a stunt”; but I prefer to think of him as the man who brought to light a serious constructional defect in the flying-machines of his day. So, too, in science. Cautious Daedalus will apply his theories where he feels confident they will safely go; but by his excess of caution their hidden weaknesses remain undiscovered. Icarus will strain his theories to the breaking-point till the weak joints gape. For the mere adventure? Perhaps partly, this is human nature. But if he is destined not yet to reach the sun and solve finally the riddle of its construction, we may at least hope to learn from his journey some hints to build a better machine.

I love the bit about straining theories to the breaking point, and also ‘hints to build a better machine.’ Anyway, those unfamiliar with the Icarus project can use the search engine here to find a surfeit of prior articles, or check the Icarus Interstellar site for still more. You’ll also get the basics from the Andersen interview, which goes into numerous issues, not least of which is propulsion. Tziolas notes that Project Icarus has focused on fusion, although ‘the flavor of fusion is still up for debate.’ Seen as an extension of the Daedalus design, fusion is a natural choice here, because what Icarus is attempting to do is to re-examine what Daedalus did in light of more modern developments. But the He3 demanded by Daedalus is a problem because it would involve a vast operation to harvest the He3 from a gas giant’s atmosphere.

Image: Icarus project leader Andreas Tziolas. Credit: Icarus Interstellar.

As the team studies fusion alternatives, other options persist. Beamed propulsion strikes me as a solid contender if you’re in the business of starship design in a world where sustained fusion has yet to be demonstrated in the laboratory, much less in the tremendously demanding environment of a spacecraft. We’ve already had solar sails deployed, the Japanese IKAROS being the pathfinder, and laboratory work has likewise demonstrated that beamed propulsion via microwave or laser can drive a sail. But beam divergence is a problem, which is why Robert Forward envisioned giant lenses in the outer system demanding a robust space manufacturing capability. So the dismaying truth is that at present, both the fusion and beamed sail options look to be not only beyond our engineering, but well beyond the wildest dreams of our budgets.

Where we are clearly making the most progress in interstellar terms is in the choice of a destination. Obviously, we lack a current target, but within the next two decades it is well within our capabilities to launch the kind of ‘planet-finder’ spacecraft that can not only home in on an Earth analogue around another star but also study its atmosphere. It would be all to the good if we found that blue and green world we’re hoping for orbiting a nearby system like Centauri B, but we’re going to be learning very soon (depending on what gets budgeted for and when) which nearby stars have planets that might be suitable targets. Icarus is not just looking for any old rock — the goal is to design a craft that could reach a world that could be habitable for humans.

Image: One vision of the Icarus craft, by the superb space artist Adrian Mann.

Why that criterion? Survival of the species is a serious interstellar motivation. Tziolas asks whether, if humanity becomes capable of going to the stars and chooses not to, it wouldn’t deserve a Darwin Award, the kind of achievement that marks its recipient as doomed. But motivations cover a wide range. I’ve written about the human urge to explore on many occasions, and Tziolas talks about pushing back technological boundaries as another prime driver. Hard problems, in other words, drive us to push the envelope in terms of solutions:

In order to achieve interstellar flight, you would have to develop very clean and renewable energy technologies, because for the crew, the ecosystem that you launch with is the ecosystem you’re going to have for at least a hundred years. With our current projections, we can’t get this kind of journey under a hundred years. So in developing the technologies that enable interstellar flight, you could serendipitously develop the technologies that could help clean up the earth, and power it with cheap energy. If you look toward the year 2100, and assume that the 100 Year Starship Study has been prolific, and that Project Icarus has been prolific, at a minimum we’d have break-even fusion, which would give us abundant clean energy for millennia. No more fossil fuels.

And let’s not forget ongoing miniaturization, also a prime player in any starship technology:

We’d also have developed nanotechnology to the point where any type of technology that you have right now, anything technology-based, will be able to function the same way it does now, but it won’t have any kind of footprint, it will only be a square centimeter in size. Some people have characterized that as “nano-magic,” because everything around you will appear magical. You wouldn’t be able to see the structures doing it, but there would be light coming out of the walls, screens that are suspended that you can move around any surface, sensors everywhere — everything would be extremely efficient.

This is a lively and informative interview, one that circles back to the need to drive a shift in cultural attitudes as a necessary part of any long-haul effort. Some of this is simply practical — the creative souls who volunteered their engineering and scientific skills on Daedalus are retiring and some have already passed away. A new design requires a new generation of interstellar engineers, one recruited from that subset of the population that continues to take the long view of history, acknowledging that without the early and incremental steps, a great result cannot occur.


Comments on this entry are closed.

  • Rob Henry March 4, 2012, 2:24

    To me, one of the most counterintuitive personal discoveries, is that virtually nothing on Earth works robustly because of a great original design, but because it has been painfully perfected through a process of trail and error. Space really is a much easier environment that Earth’s ceaseless variations, so when there is extensive experience in space manufacture, the problem of malfunctioning equipment, should drop so abruptly, that many here may wonder why they were ever so worried about it in the first place.

  • Eniac March 5, 2012, 2:27

    @Tom Lemon

    Yet you blithely talk about hundreds of years, as it if will just magically happen.

    I do not think I did. I did not say it was easy. All I said is if Voyager can last as long as it did, it seems that 10 times that is not as completely out of reach as you make it sound.

    “Unless you can provide a reference, I will relegate it to the nonsense category with your other claims.”

    Sorry, but you’ve got it backwards. The burden of proof isn’t on me to prove anything. The burden of proof is on *you* to provide references to back up *your* claims.

    Please do not quote me out of context. My remark was about this:

    Law of Ecosystems…the size of the self-contained ecosystem increases with the square of the time it must remain self-contained

    I could not find reference to such law, and it does not make sense to me. All I am asking is a reference of some sort. I am still waiting.

    I have really not made any claims. If you look back, you will see that I have simply dared to raise doubts about yours, and have professed ignorance on the issue, only going as far as mentioning I had heard it said otherwise.

    I would also like to respectfully note that your argumentation to me appears long on polemics, short on facts or logic, and full of brash overstatements.

  • Eniac March 5, 2012, 2:54

    Nick, I must admit I do not follow your “running the numbers”. There are just too many casual orders of magnitude in them. I took the time to calculate how much space a billion trillion parts of an average volume of 1 cubic centimeter would take. It turns out the Earth would be covered in them about 1 m high. Including the oceans.

    In any case, we are not trying to move the entire economy of Earth, we are just trying to package an industrial seed. The difference is like that between a tree and a nut, or a mushroom and a spore.

    It is an extra-hard problem, make no mistake about it. But I think it is solvable, and this is the time to try. There is great promise in automation and in flexible fabrication, two very new approaches that attack the problem on two very complementary fronts. I think there are great advances to be made in the next few decades.

    If you haven’t yet, take a look at Freitas’ work (http://www.molecularassembler.com/KSRM.htm). It is, I think, quite inspirational.

  • Eniac March 5, 2012, 5:27

    I bring up issues like “vacuum welding”, “diffusion of volatiles into vacuum” and I hear nobody offering to discuss them realistically.

    Neither vacuum welding nor diffusion of volatiles have kept our space probes from flying for decades. Vacuum welding is rare, and it is easily avoided by choosing the right combination of metals in contact points. You say “Gases and fluids diffuse out of the system”, but don’t they do the same thing on Earth? That’s why we have container walls, and those do not magically become more permeable just because there is a vacuum outside. In the worst case, an extra few microns of impermeable material should deal with an extra bar of pressure just fine.

    Each of these issues, by themselves, is quite capable of killing off any interstellar probe project you care to name. Each of them is a engineering problem that could easily push your projects off the charts of viability

    If those were the most serious problems in starship design we should count ourselves very lucky and look forward to a ride this decade.

    (it’s that exponential factor again, sorry).

    Sorry, I do not follow. Which exponential is that?

    You seem to be referring to some fearsome exponential that makes 100 year systems impossible when 10 year systems are easy. I know of one time exponential, but it is not so fearsome: Exponential decay. The exponential in this case is decreasing, so it would actually be in our favor. Most decay happens in the first time period, decay will then quickly (exponentially) taper off in succeeding time periods. No, this is certainly not what you mean.

    The worst effects I can think of are linear in time, for example corrosion by atomic oxygen (which BTW is a real problem with real spacecraft, but does not exist in deep space). You leave something out twice as long, and it will have lost twice the material. Ten times as long, ten times the material. So you add in the beginning as much as will be taken off (a few microns per year, would be my guess). Or you add protection, such as gold foil.

    No exponential here. So what is this mysterious exponential? Surely you can point it out to us. With the little information you have given us, I am stumped.

    Radiation? The solar wind is so incredibly thin that it cannot make a dent in materials in a very long time. Cosmic rays are even much thinner. The worst is atomic oxygen, but that exists only in the top 800 or so km around Earth. What cosmic rays can do is every once in a while flip one of millions of bits the wrong way, which could crash your computer. If you hadn’t hardened it, that is, and added error detection and correction. Both of which are quite routine and not much of an engineering challenge.

    I am with you in that it is important to mind the difficult problems. But building the less difficult among them up into fictitious unscalable mountains is not helpful, especially if it does not come with solid reasoning.

  • david lewis March 5, 2012, 13:04

    Voyager was launched in 1977, that is around 35 years. It is expected to last (remain operational) until its power supply runs out in 2025. Which is 48 years. I fail to see why anyone would expect a system that lasts 100 years to be impossible. We already created a system that can last 1/2 of that time.

    Space is a very different environment from the ones that we have spent the last few thousand years learning how to build in. That takes some practice and learning to overcome. However, the advantages are also staggering. No wear and tear on items from temperature change, from a very corrosive atmosphere, from moisture, …. No needing to replace items every few years or repair them.

    If space was such an harsh environment that parts needed to be replaced every ten years then communication satellites with life times of 20 years would be impossible. Yet such satellites do exist. It’s fuel that limits their life span, not wear and tear on any of the parts.

  • Tom Lemon March 5, 2012, 14:56

    Well if my comments have seen combative, I apologize. The key issue here is that many people are harboring a belief that is simply not true:

    “Space really is a much easier environment that Earth’s ceaseless variations”

    This is a misconception and one that needs to be overturned if any interstellar folks are going to make real progress. Space is *not* easier. It might appear that way to casual view, because people on Earth tend to take for granted the incredible protections that Earth’s gravity well and atmophere afford us. Once we leave those protections, the universe is very hostile indeed to complex systems, biological or mechanical.

    Again, vacuum welding, radiation, diffusion are just a few of your many enemies, and they are implacable and unstoppable. Multiply those by a multi-decade trip in a closed environment, and this creates a challenge that might very well be unsolvable (size and weight of craft climb exponentially, until no society of any size could realistically consider them.)

    Another common misconception is that “there is always a solution.” In fact, history is littered with engineering impossibiilities, problems to which there are no viable solutions.

    Don’t be negative, but be realistic.

  • Tom Lemon March 5, 2012, 15:37


    It’s not a question of “whether” there are exponential factors. The question is, “how many additive exponential factors”.

    Just as a start:

    1. You are going from a 20 year trip with a very simple system (such as Voyager) to a 70-100 year trip. Even solid-state electronics don’t last that long. Survivability drops close to zero…unless you build a much more complex system. Boom. 10X the complexity right there.

    2. You changing from “Less than 1 percent the speed of light” to “10% the speed of light”. Damage from dust increases exponentially. Survivability again drops to zero, unless much bigger shields. Oops…another exponent.

    3. From “well understood and charted local conditions” to “very poorly charted conditions in deep space.”

    4. Etc.

    So yes, exponential upon exponential.

    I understand that it’s not fun to think about all this, but if you want to have any validity at all, it must be done.

  • Eniac March 5, 2012, 22:05

    @Tom Lemon

    1. You are going from a 20 year trip with a very simple system (such as Voyager) to a 70-100 year trip. Even solid-state electronics don’t last that long. Survivability drops close to zero…unless you build a much more complex system. Boom. 10X the complexity right there.

    I fail to see the logic that leads to the factor of 10. Furthermore, I do not see an exponential here.

    2. You changing from “Less than 1 percent the speed of light” to “10% the speed of light”. Damage from dust increases exponentially. Survivability again drops to zero, unless much bigger shields. Oops…another exponent.

    The energy of a dust grain goes up with the square of velocity, and their impact rate linearly. Thus: third power, not exponential.

    You are right, though, that this one is a problem for high velocities, and it has been hotly discussed in these pages on many an occasion. Not blithely ignored, as you would have it.

    3. From “well understood and charted local conditions” to “very poorly charted conditions in deep space.”

    I fail to see how this even quantifies, much less to something exponential. I am beginning to suspect innumeracy here….

    4. Etc.

    So yes, exponential upon exponential.

    So no, I am counting zero out of three. This does not bode well for number 4, the “Etc.”, statistically speaking.

    I understand that it’s not fun to think about all this, but if you want to have any validity at all, it must be done.

    Actually, it is fun, to a degree….

  • david lewis March 6, 2012, 0:49

    The key issue here is that many people are harboring a belief that is simply not true:

    Precisely. If the factors you have mentioned were so overwhelming impossible to overcome then modern society would be vastly different.

    ie. If vacuum welding is going to destroy anything we launch into space then how come voyager has lasted 35 years and is expected to last another 12-13 and only stop operating because of power failure. Not because of any of the problems you have mentioned.

    Reality check: Voyager exists!
    1. Vacuum welding hasn’t destroyed it.
    2. Radiation hasn’t destroyed it.
    3. Diffusion hasn’t destroyed it.

    There are serious problems with building any long lasting probe but the ones you are mentioning are the easiest to overcome. Why keep pointing them out? Eniac has already pointed out that they are not the insurmountable problems you have made them out to be. We have a case study in voyager that systems in space can last at least 1/3 of a century. A system that is expected to last 1/2 of a century. A system built with materials and knowledge of 30+ years ago.

    Reality has dictated that those three issues are not as insurmountable as you claim them to be.

  • Rob Henry March 6, 2012, 18:03

    I believe that I know the reason that Tom Lemon and Eniac can’t comprehend each other. If so the answer is in a story that a keen mountain climber once told me.

    For a long time Everest remained unclimbed, and the main reason was that the atmosphere is so thin at its peak that climbers and their equipment manufactures could seldom gain much working knowledge in this environment. Now, from the perspective of design or engineering (I believe Eniac’s approach), you may have expected its ascendancy would have awaited a suitable knowledge and equipment base, but for the explorer (Tom Lemon) not so. He wants to go now, and where the former sees inadequacy, the latter sees that everything that is needed is currently available. The first ascents of Everest were achieved with a siege technique where an expedition would start with hundreds of climbers and Sherpa’s carrying the obscenely inappropriate equipment that was available at the time. The numbers would then fall off exponentially with height until the task was completed of placing one or two climbers at the top.

    I hope that helps.

  • Eniac March 7, 2012, 0:25

    @Rob, nice story. It’s just, ahem, I would have expected it to include at least one character that says it cannot be done, as this is pretty much what Tom Lemon has been saying :-)

  • Tom Lemon March 7, 2012, 12:52

    Every time you bring up Voyager, that simply confirms for me that you don’t get it.

    Voyager is an extremely simple system, compared to what you are proposing. Simple systems are robust, by definition.

    An “Icarus” style starship would be several orders of magnitude more complex, as described by this article. That additional complexity adds fragility to the system. Added fragilty X added distance (not decades, but hundreds of years) X added speed = a total different problem.

    Again, there are laws of complex systems. People who study complex systems, know how to apply those laws. You folks need to learn.


    A more accurate story would be this:

    “For years, tinkerers have been trying to build perpetual motion machines. Physicists and engineers are constantly trying to get those tinkerers to look at the physical laws that prevent such machines, but the tinkerers never want to deal with such things….they are busy having fun inventing imaginary machines and ignoring physical limits. Real physical, thermodynamic liimits are no fun. There will always be perpetual motion nuts, and they will always be ignored by qualified engineers, because they are a waste of time.”

    You folks are the equivalent of the perpetual motion tinkerers. Perhaps you think of yourself as Everest explorers…well most perpetual motion tinkerers think of themselves as Everest explorers too, but let me clue you in, they aren’t anything of the kind.

    Finally I’ll repeat my first comment. It may be that interstellar travel is possible. I’ll keep thinking about it. I’m sure other qualified engineers will work on it. But the way it’s being approached here — ignoring the real issues — ain’t gonna do the job.

    Good luck!

  • Eniac March 7, 2012, 17:35

    Again, there are laws of complex systems. People who study complex systems, know how to apply those laws. You folks need to learn.

    Please teach us, oh wise sage, or are we not worthy?

  • david lewis March 7, 2012, 19:28

    Every time you bring up Voyager, that simply confirms for me that you don’t get it.

    So vacuum welding will only happen if a machine has x complexity? Or radiation will only affect a machine if it has x complexity? Or some mythological beast in the far reaches of space will swallow the machine whole only if it has x complexity.

    A more accurate story would be this:

    For years cartographers placed messages like ‘here be dragons’ on areas of maps that were unexplored. Or warned of falling over the edge. Of course there were no such monsters and no such edges.

    Or those wise sages who stated that heavier than air flying machines were impossible. Or stated that those same machines could never exceed the speed of sound.

    To compare an interstellar probe to a perpetual motion machine is ridiculous.

    As for complex systems being fragile. C0mplex systems can be very robust when designed for certain events. Fragile when dealing with inputs they are not designed to handle. You really think that a probe can’t be hardened against radiation or vacuum welding. Just saying complex systems are fragile is ridiculous. It shows you have little understanding of complex systems yourself. The human body is a complex system. It can be robust and continue operating even after the loss of a limb, or even multiple limbs. It can be fragile, remove even a milligram of vital tissue and it can lead to death. Just saying something is impossible because it would be complex is ridiculous. Saying something is fragile because it is complex is misleading.

  • Eniac March 7, 2012, 23:15

    Law of Ecosystems…the size of the self-contained ecosystem increases with the square of the time it must remain self-contained

    I could not find reference to such law, and it does not make sense to me. All I am asking is a reference of some sort. I am still waiting.

    Still waiting …. It would be the least you could to to educate the unenlightened.

  • Allan June 25, 2012, 13:02

    If we really want to travel to the stars we need to dump the “Theory of Relativity” nonsense, it doesn’t fit with what we know about quantum physics or dynamics without extreme “patches” that are very unlikely. We need to go back to Newtonian Physics, which with a couple of additions fits everything perfectly.

    There are now a few alternatives to the Theory of Relativity. Personally I like Newton as his theories allow all sorts of possibilities.

  • Hinkster October 23, 2012, 10:37

    Why not ditch the advanced propulsion desires, and go with a more simple “generation ship” approach? My main point here would be two things; a) if we know that slower spacecraft speeds (less than FTL) and great interstellar distances will require more than the productive years of a human lifetime, say 50 to 150 years trip time one way, why not build a spacecraft that would support families dedicated to the concept of the “for the greater good of the human race”, we are traveling to the target location and returning home back to earth. This would also be based on two assumptions that 1) we know we have a viable target planet, and 2) if over the course of the generation ship departure, Earth develops a FTL drive, we just stop by and pick them up.
    b) The budget required to build a ship that could support several families on a community type scale for such a project as this would be far less than the cost and research of attempting to build a FTL craft or even a craft capable of near FTL speeds. Which would be far more realistic in the terms of our abilities to create.

  • Santiago October 26, 2012, 16:49

    For instance this planet will die but, can we do or even want to do anything about it?

  • Santiago October 26, 2012, 16:54

    “As humans we are the Open the don’t open box type of creatures, curiosity is a part of us some stronger then others, we must be able to take hold of it and drive it forward.” (Albert Eisenstein) I fully support this idea of man’s complicated curiosity to fly into the unknown but there are problems, that i do not deny we can and will overcome them just why not today?