≡ Menu

Icarus: Fusion and Secondary Technologies

Discovery News now offers fully ten articles on Project Icarus and its background, written by the Icarus team and assembled on the site by Ian O’Neill. I was startled to realize how the list had grown, but it reminds me to point periodically to this collection, because Icarus — the attempt to re-design the Project Daedalus starship study of the 1970s — is a work very much in progress. Icarus is a joint project of the Tau Zero Foundation and the British Interplanetary Society. The latest article on the team’s work is by physicist Andreas Tziolas, who in addition to being a frequent Centauri Dreams contributor is also secondary propulsion lead for the Icarus effort.

It’s no surprise that the biggest issue surrounding an interstellar probe is the propulsion system, which for Icarus means fusion, a method offering as much as a million times better performance than our current chemical rocket technologies, if we can ever figure out just how to harness it. The Icarus team chose fusion deliberately and with full knowledge that alternatives were out there. Fusion, after all, was the propulsion method of choice for the Daedalus designers, and a major part of the Icarus effort has been to take an existing design and look at it in today’s terms. Have a look at Using Fusion to Propel an Interstellar Probe for more on this design choice.

Breakthroughs vs Evolution

We’d all like to see the kind of sudden breakthrough that would in a single stroke put deep space in range, and perhaps one day something like this will happen. But the gap between what we can do with today’s technology and what we’d like to achieve with such a breakthrough is a daunting one, wide enough that it tends to shut down active research. What Icarus is all about is the idea that we need to do the research anyway, that a series of designs can get better over time, and that each time we run the new iteration, we learn more about where we need to go.

Tziolas’ latest contribution to the Icarus story is his take on secondary propulsion systems, technologies that would come into play both as the Icarus craft is built and when it arrives in its destination solar system. And as he notes, what is considered secondary for the Icarus mission is essentially what is primary for all contemporary space missions, a fact that highlights how far we have to go to mount a true interstellar effort. Solar sails, for example, might be the technology to use when a craft like Icarus deploys small probes to study its target system. And sails are one among a host of options that might help in spacecraft construction:

…solar sails may not be a good option for accelerating what would be a very massive Icarus to another star, but offer unique advantages for exploring the target solar system with probes. The advances in ion (NASA’s NEXT and NSTAR) and electromagnetic thrusters (VASIMR) in recent years seem to indicate a path towards some new and exciting propulsion technologies being developed. Some of these systems might be used on the Icarus interstellar spacecraft itself, and others may play supporting roles. For example, the technologies necessary for the spacecraft construction and fuel gathering stages of the mission.

We know where chemical rockets are at their most useful, and that is in scenarios demanding high thrust. Building massive and complex objects in space demands a much improved way of getting to low-Earth orbit, almost certainly a vehicle that can not only make frequent flights, but operate as a single-stage-to-orbit craft. Thus Tziolas’ interest in Skylon, an unpiloted craft from the British firm Reaction Engines Ltd. that is envisioned as operating in a fleet of vehicles equipped with air-breathing jet engines to assist them in reaching orbit in a single stage.

Image: The unpiloted Skylon is one possibility for getting frequent payloads to low-Earth orbit. Credit: Adrian Mann.

SpaceX’s plans for a Falcon Heavy, based on the company’s existing Falcon 9 booster but capable of launching 117,000 pounds into orbit (that’s twice the capacity of the Space Shuttle) point in the same direction. The original Daedalus design was for a craft weighing some 50,000 tons, almost all of which were comprised of the Helium-3 essential for its fusion engines. Before any interstellar craft can get built, we have to have the kind of space-based infrastructure that will allow us to move within the Solar System (Daedalus envisioned mining a gas giant’s atmosphere for fuel — Icarus has not yet made a decision on a fuel source). And the ability to launch heavy loads frequently is the biggest piece missing in the infrastructure puzzle.

Fusing Futuristic Ideas

The effort to design a craft that is well beyond our current capabilities leads us to re-examine and perhaps combine developing technologies. We’ve begun to fly solar sail demonstrator missions, and we have begun to consider whether the solar wind could drive a large magnetic sail, a device already known as a magsail. Beyond that, we have laboratory work suggesting that beamed propulsion using laser or charged particles for acceleration is possible. Tziolas wonders how we might draw from such technologies to assist a future interstellar probe:

Combining these two ideas may lead to an advanced space tug, responsible for pushing spacecraft equipped with magsails into their orbits. Perhaps the Icarus could serve as the beam generator which pushes its planetary explorer probes into place. Alternatively Icarus could use an extremely large magnetic sail to help decelerate, once within reach of the target star’s solar wind or magnetosphere.

Such musings offer a futuristic roadmap of ideas to examine as we ponder propulsion methods that are interstellar in implication and remain within the bounds of known physics. We need to push current technologies hard. Icarus project leader Richard Obousy made the case for fusion on Seth Shostak’s radio show recently, where he noted ‘To use rocket fuel to reach the stars in a time-frame consistent with a human lifetime is completely inconceivable.” It’s a good interview (starting at 41 minutes 35 seconds into the main show), one in which Seth probes Richard for details about the new paradigm Icarus will need to surmount chemical rocket limitations.


Comments on this entry are closed.

  • Peter April 26, 2011, 10:49

    Perhaps someone can explain how reaction engines intends to reach orbital escape velocity for SSTO using chemical based rockets.

  • Alex Tolley April 26, 2011, 12:07

    Even if interstellar travel by fusion rocket remains unlikely, the engines would be very useful for flight within the solar system, especially if the thrust was high. If we aim for the stars, but achieve the planets, that would be a very worthwhile result.

    Has anyone looked at the numbers behind the Daedalus/Icarus fusion engines for interplanetary travel?

  • Alex Tolley April 26, 2011, 17:47

    @Peter REL has a design for a mixed mode engine that uses atmospheric air for flight during the early ascent phase, then switches to rocket mode for the final acceleration to orbit. This is sufficient to get a SSTO vehicle. The engine is, of course, the centerpiece, and much depends on whether it gets enough funding to prove the concept and if it does, whether the performance is sufficient for the task.

  • Dave Moore April 26, 2011, 19:33

    Peter, it is best if you go to their website. They have a comprehensive explanation of their craft there.

    Incidentally, Reactions Engines is about to start testing their compound gas turbine/rocket engine, and they have just received a positive report from both NASA and the ESA, which should enable them to attract enough funding to build and flight test a full scale engine.

    If all goes well, the hope to have their first flight in 2018, but that would assume a plentiful supply of capital and no unforeseen problems. If the ESA throws its weight behind the project, I could see them flying by the end of this decade as technologically speaking the design is fairly conservative with the exception of the engines.

  • Rob Henry April 26, 2011, 21:40

    Alex Tolley, I feel the comparative lack of interest in far future modes of travel within the solar system, stems from how poorly publicized the wonders of our own system have been. Io, Europa, and Titan are such incredible worlds to supplement the more Earth-like planets of Mars and Venus, that I wonder how many parsecs you would have to travel to find a system as interesting as ours would be without Earth.

    We might be reaching for the stars, but it would be great if in trying we just got Sol.

  • Adam April 26, 2011, 23:17

    Hi Alex

    I have played around with the figures for using a “Daedalus” Second Stage engine to transfer propellant from Uranus in this “Icarus” blog-entry…

    Starflight on the Cheap: Part II

    …which would be a good reason to develop at least that part of an interstellar capable vehicle. Higher-thrusts and lower fusion fuel consumption rates would require adding a diluent to the fuel pellets, which isn’t an onerous modification.

    But using its regular exhaust velocity (9,210 km/s) a Daedalus 2nd Stage could fly from Uranus to Earth, one-way, in five weeks for a fuel fraction of just ~11%. Assuming 500 tonnes of payload, then that’s just ~121 tonnes of fuel needed and pulse rate of once every ~72 seconds (cf. 250 Hz at top thrust.) More leisurely out-bound time-tables and no payload would allow much lower fuel expenses for empty “D-Freighters” to be sent out to pick-up fuel as required.

    So fusion propulsion, Daedalus-style, certainly does have a lot of potential uses in the Solar System.

  • Kenneth Harmon April 26, 2011, 23:45

    Dear Richard Obousy and the Project Icarus Team,

    While it makes perfect sense given todays knowledge to focus on Fusion Power as the best early option to send a probe to another star system, and especially Alpha Centauri if that indeed becomes the designated target, there are two other ideas you may want to consider as you explore mission design options and trades for Icarus. First, how might major advances in Teleportation Technology by ~2075 potentially impact Icarus? While Teleporting Biological Systems without killing them may be Centuries off, it is now generally believed by those working in the field that within the next 50-75 years if not sooner we will have the ability to teleport very large and complex objects over vast distances once the actual departure and arrival Teleporation Gates are created. It seems that merging Icarus and its mission with Teleportaton Technology especially of large objects would yield many benefits.

    The second idea to consider is what may turn out to be some Revolutionary work being done by Massimo Villata at the Observatory of Turn in Italy. Villata has collected some preliminary data that indicates that Anti-matter Gravity could explain Universe Expansion. In essence, Villata believes that he has found evidence that there is “repulsive Gravity between Matter and Anti-matter and that our current predicted theories about the interaction between Matter and Anti-matter may be wrong. For Icarus the importance of Villat’s research is that Negative Energy may exist and it could be created for use in propulsion. Simply Google Villata+Anti-matter Gravity for additional details.

  • henk April 27, 2011, 13:12

    Kenneth Harmon

    yes but the chance that Villata is wrong is a lot higher than the chance that he is right

  • Peter April 27, 2011, 17:20

    [blockquote]Peter REL has a design for a mixed mode engine that uses atmospheric air for flight during the early ascent phase, then switches to rocket mode for the final acceleration to orbit. This is sufficient to get a SSTO vehicle. [/blockquote]

    Based on my understanding conventional chemical rockets using things like liquid hydrogen or liquid oxygen tend to max out in theory and practice at around Mach 10 -15… Orbital escape velocity for genuine SSTO is Mach 26-27 or approximately 17,500 mph. That’s why NASA gave up on SSTO, because they knew they would have to go nuclear and nukes in the upper atmosphere- even for peaceful scientific purposes- were taboo.

  • mike April 27, 2011, 22:52

    the time frame of our civilization doesnt lend itself to such a grand scheme.
    no fusion power reactors on earth. using oil and massive failures of fission reactors do not bode well. constant wars without end. the concentration of wealth into a tiny elite. these and other social issues have to be worked out along with the technical details. how can we justify such an expenditure to the people of haiti or new orleans? the u.s government doesnt want to fund social security but spends vast amounts on air conditioning in afghanistan. karl wolfe says, “everything is everything”. what we need is a hollywood blockbuster movie. sell the rights to fund the research. reality tv anyone?

  • Eniac April 28, 2011, 19:29


    Teleportation and Anti-gravity are exactly the sort of thing Icarus excludes from the outset, very wisely. None of it has any basis in reality, theoretically or practically. It is called fringe science for a reason.

    Sure, one of these might unexpectedly turn out to be real some day. But, even in this case, we won’t know ahead of time which and when, so it does not really make any sense to make plans on it, does it?

  • Kenneth Harmon April 28, 2011, 22:52


    I can understand your comment about anti-gravity since this appears to be very much theoretical. This is not the case with Teleportation. Teleportation of individual particles has already been demonstrated in the Lab. Next will be Teleportation of Molecules by the 2020’s, which is a very conservative projection . After that many respected and conservative Scientists in the field believe that once reliable Quantum Computing is developed by 2050 or earlier then scaling up to the Teleportation of large and complex objects will only take a couple of additional decades. Teleporting Biological Systems and not killing them in the process is a much more complex and difficult undertaking, and may takes many Centuries to become even theoretically feasible.

    If we stick to teleportation of large and complex objects as the nearer terms goal then many respected Scientists who are familiar with the research, even if they are skeptical of the near term applications, will tell you that this type of Teleportation capability will be developed and routine by the 2090’s at the very latest if not decades before.

    From what I understand Icarus is targeting the 22nd Century as the earliest possible date so Teleporation of large and complex objects should be available long before then. Star Trek type Teleportation is definitely “fringe Science”. More limited Teleportation to include large and complex objects is a respected field with respected research where significant progress is being made—today.

    If Icarus was targeted on flying by the 2070’s then I could see your point since Teleportation Technology of the type that would be useful probably will not be ready, However, given the comparative rates of curent progress for Advanced Fusion Propulsion and Teleportation it is likely that Teleportation Technology to include large and complex objects will be available long before the projected Icarus propulsion system is demonstrated. This is why we may want to think about how the two modalities could be blended together so that an Interstellar Probe Mission might be conducted in the 21st Century.

    The best thing to do is to Google some of the current work being done on Teleportation. You will be surprised by the progress currently being made. I am not quite ready to say the Teleportation of large and complex objectsd during the 21st Century will be a “slam dunk”, but it is highly probable barring some sort of Global wide catastrophe.

    Finally, you may indeed argue that in the future complexity will eventually slow-down the rate of progress on developing Teleportation Technology, but right now it appears that until we reach “the knee in the cuve” with Teleporting Biological System progress will be steady and accelerating.

  • Richard Obousy April 29, 2011, 13:33


    Thanks for your suggestions to the Project Icarus team.

    Let me point out that Project Icarus is the successor to Project Daedalus, performed in the 1970’s. Since Daedalus was fusion based, the decision to pursue fusion propulsion technology was made early on, in part to ensure continuity with Daedalus. In addition, fusion is one of the more credible candidates of choice for interstellar propulsion, in terms of Technology Readiness Levels.

    Our Project Program Document, which can be downloaded from our website http://www.icarusinterstellar.org, outlines a series of design philosophies that the team has agreed to adopt. Our design philosophy 3 states “The designer shall remain well informed with current scientific and technological developments which may impact the Icarus design and mission.” Thus, any breakthroughs in macroscopic quantum teleportation would be considered relevant by the team, but we’ve not seen any breakthroughs that justify us changing our research direction at this stage.

    Our design philosophy 4 states “Extrapolations of current technology is to be of a linear type only and limited to a few decades hence.” As has been already mentioned in other posts, anti-gravity is speculative, and macroscopic quantum teleportation is not something that can be extrapolated to a few decades hence.

    While we would both welcome and embrace any other research teams pursuing different approaches to solving the many issues associated with interstellar propulsion, we’ve selected the fusion route, and will stick with this until the project’s completion in 2014, barring any significant shifts in the scientific landscape.

  • ljk April 29, 2011, 14:45

    Kenneth H., how far have these people who advocate teleporation, antigravity, and antimatter methods actually gotten with their research? How much money, resources, and other supports do they have?

    If we are having trouble making fusion energy happen, which is at least proven through solar physics and in hydrogen bombs and has had millions of dollars put into its development, how do you expect these other ideas to come to fruition any time soon? I could just as easily say we need to find or make our own cosmic wormholes for instant transportation to anywhere in the galaxy, but without resources or support this is all just talk bordering on science fiction.

    Under other circumstance I might worry about sounding like the people who once said that heavier than air flight will never happen, but years of seeing claims like this by people and groups who can’t possibly make them happen has made me skeptical in these areas. I will be among the first to rejoice should we have such technological breakthroughs, but so far it is still a lot of talk and white papers, distracting from our real chances of interstellar flight.

    I would still like to see some group resurrect the Orion nuclear fission propulsion concept. It is the closest idea we have to a real propulsion method and had development not been stopped in 1963, we might have at least witnessed a much more expansive exploration of the Sol system by now. Maybe even a probe on its way to Alpha Centauri, if I dare say so.

  • Rob Henry April 29, 2011, 16:47


    What’s really confusing me is that if you truly anticipate some form or scale of teleportation being possible over stellar scales within a century, surely its greater use would be in transferring the massive amount of information inherent in molecular structure. I note that you bring up this topic in reference to interstellar transport, not as an answer to the Great Silence. To an outsider that sounds like you lack enough confidence in your technology to consider the prospects of its fruition particularly closely.

  • Kenneth Harmon April 30, 2011, 16:45

    Dear Rob Henry, Ijk, Eniac and Richard Obousy,

    I am going to say something here that may sound a little cynical or in fact may be somewhat offensive to some of you, and forgive me I do not mean to be, but it needs to be said. As a general rule of thumb where dealing with longer term technology investment and development “one must follow the military app”, This is one of the “golden rules” of the history of technology development since much can get done under the guise of military applications. Just look at Von Braun and the V-2 as exhibit A.

    This is why I am far more optimistic about the fairly rapid development of things like Anti-matter Technology and Teleportation Technology starting with but not exclusively limited to macroscopic quantum Teleportation. They along with potential “game changers” such as Quantum Computing, Directed Energy, and Nano-Technology have a direct nearer term military application. Under the right set of conditions such as a major War (or new Cold War) within the next ~15 years they would be candidates for massive investment (many 10’s of Billions+).

    On the other hand, and quite sadly, both Fusion Energy and Fusion Propulsion such as the type envisaged for Icarus have always been seen as “nice to have” technology, but they are generally perceived especially within the U.S. Government as being long term “we get there when we get there” technologies even under crisis conditions. Therefore, barring something extraordinary like an ET event they will relatively speaking be funding starved for many decades to come whereas both Anti-matter Technology and Teleportation Technololgy could really “break out” in terms of priority funding in the nearer term (next ~15 years) under the right set of National Security conditions. One example would be the U.S. being forced to Mobilize itself for a major War or Cold War in the next ~15 years as some reputable analysts (including the NIC) believe is increasingly likely. Under such a scenario the current general fear of risk and lack of vision we see, especially within the U.S. and especially over the last ~40 years could disappear over night. In essence, it is amazing what the U.S. can do when it is desperate and we are forced to innovate, but it is usually for a Military purposes.

    For example, just imagine being a person in 1932 and trying to project the level of technology advance a mere 15 years later in 1947. The rate of development would have been impossible to project as things that were viewed as “Fringe Science” at best in 1932 were routine by 1947. Of course what made this happen was the unfortunate neccessity of WW-2. Of course, no doubt you will say, but Ken look at the current Deficit problems, and various other major constraints which is no doubt true. However, before we get overly caught up in the Conventional Wisdom of our times let me just site one Historical pattern as a potential contrarian indicator. (1621, 1701, 1781, 1861, 1941, 2021?), Approximately, every 80 years the U.S. or the earlier 13 Colonies have faced a major Crisis situation so we are about due in the next 10 years. This in turn tells me that many of the constraints that today we consider “normal” and have been in place for at least the last ~40 years may be going away sooner then we think.

    Actually, for Icarus I fully support the Fusion first approach, although like Ijk I also like the old Orion approach since I would love to see a Manned Mission to Alpha Centauri by the mid to late 21st Century provided of course there is anything there.. Unlike most, including Marc Millis, I still consider such a mission to be a real possibility by the late 21st Century given what I suspect may happen within the next ~15 years as Humanity is forced by circumstances to make another huge technology leap when we least expect to. That said, it would be nice if those designing Icarus could design in enough margin that if radical new propulsion methods came along the Icarus design could be readly adapted. Given the focus on Fusion Propulsion the Icarus design will likely be a very large beast, which is very good news since such design should be able to readily adapt to newer and more efficient tecnology breakthoroughs.

  • ljk May 5, 2011, 15:23

    I know one thing that is on your side, Kenneth H.: Most of us won’t be around by the time we learn whether these predictions come true or not. :^)

  • Eniac May 6, 2011, 2:19

    The first paragraph on Wikipedia for “quantum teleportation” makes it clear that the research taking place in this field is not concerned with transporting matter, and not even ‘classical’ information. No serious researcher would claim that this “technology” would ever transport objects from one place to another, whatever their scale or complexity.

    Even if it were possible, to make a prediction about the future that goes “will be routine by the 2090′s at the very latest if not decades before” is patently absurd. We cannot even predict with such accuracy when electric cars will be routine, or oil obsolete.

  • ljk May 20, 2011, 14:05

    For those who keep hoping that The Government-Military have alien starship propulsion drives hidden away at Area 51 taken from the 1947 Roswell Incident, you may finally have to start looking elsewhere, or even build your own:


  • ljk May 31, 2011, 4:00

    Projects in Profusion: A Skeptical Look at 3 Wild Fusion-Energy Schemes

    Venture capitalists and funding agencies aim to get some bang for their alternative fusion bucks, but a lot of unknowns remain

    By Graham P. Collins | May 26, 2011

    When it comes to radical energy solutions, an extreme long shot is a nuclear power scheme that would combine fusion and fission. Existing nuclear plants all run on fission, the splitting of heavy nuclei such as uranium, to produce power—not to mention tons of hazardous waste.

    Fusion joins together light nuclei, as occurs in stars and hydrogen bombs, but practical fusion-power generation has yet to be demonstrated despite decades of research. One of the newest ideas is a hybrid plant in which fusion would trigger atom splitting in spent nuclear fuel, boosting the energy output and “burning up” the waste.

    Yet that hybrid approach looks positively mainstream alongside some other speculative fusion work that has recently attracted attention and venture capital. Online chatter about alternative fusion research reignited this month when the ambitiously named General Fusion announced it had raised $19.5 million from investors including Amazon.com’s founder Jeff Bezos. General Fusion’s planned machine would look right at home illustrating a steampunk novel.

    Compared with the billions that governments are sinking into projects such as the National Ignition Facility (NIF) and ITER, $20-or-so million is a pretty cheap lottery ticket. But is there really any chance of a payoff? Is any concrete progress getting reported? Here’s a quick snapshot of three of the projects.

    Full article here:


  • ljk June 1, 2011, 1:34

    Here is another review on the Area 51 book, also pretty much denouncing it all around and showing that the idea may have come from an SF story:


  • ljk August 25, 2011, 0:15

    Fusion power: is it getting any closer?

    For decades, scientists have been predicting that, one day, the same process that powers the sun will give us virtually unlimited cheap, clean electricity. Are they wrong?

    Leo Hickman

    guardian.co.uk, Tuesday 23 August 2011 21.00 BST