How to Build a Starship — and Why We Should Start Thinking About It Now

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With a growing number of Earth-like exoplanets discovered in recent years, it is becoming increasingly frustrating that we can’t visit them. After all, our knowledge of the planets in our own solar system would be pretty limited if it weren’t for the space probes we’d sent to explore them.

The problem is that even the nearest stars are a very long way away, and enormous engineering efforts will be required to reach them on timescales that are relevant to us. But with research in areas such as nuclear fusion and nanotechnology advancing rapidly, we may not be as far away from constructing small, fast interstellar space probes as we think.

Scientific and societal case

There’s a lot at stake. If we ever found evidence suggesting that life might exist on a planet orbiting a nearby star, we would most likely need to go there to get definitive proof and learn more about its underlying biochemistry and evolutionary history. This would require transporting sophisticated scientific instruments across interstellar space.

But there are other reasons, too, such as the cultural rewards we would get from the unprecedented expansion of human experience. And should it turn out that life is rare in our galaxy, it would offer opportunities for us humans to colonize other worlds. This would allow us to spread and diversify through the cosmos, greatly increasing the long-term survival chances of Homo sapiens and our evolutionary descendants.

Five spacecraft — Pioneers 10 and 11, Voyagers 1 and 2, and New Horizons — are currently leaving the solar system for interstellar space. However, they will cease to function many millennia before they approach another star, should they ever get to one at all.

Clearly, if starships are to ever become a practical reality, they will need to be based on far more energetic propulsion technologies than the chemical rockets and gravitational sling shots past giant planets that we use currently.

To reach a nearby star on a timescale of decades rather than millennia, a spacecraft would have to travel at a significant fraction — ideally about 10% — of the speed of light (the Voyager probes are traveling at about 0.005%). Such speeds are certainly possible in principle — and we wouldn’t have to invent new physics such as “warp drives,” a hypothetical propulsion technology to travel faster than light, or “wormholes” in space, as portrayed in the movie Interstellar.

Top rocket-design contenders


An artist’s conception of the proposed Project Orion spacecraft powered by nuclear propulsion. Image Credit: NASA

Over the years, scientists have worked out a number of propulsion designs that might be able to accelerate space vehicles to these velocities (I outline several in this journal article). While many of these designs would be difficult to construct today, as nanotechnology progresses and scientific payloads can be made ever smaller and lighter, the energies required to accelerate them to the required velocities will decrease.

The most well thought through interstellar propulsion concept is the nuclear rocket, which would use the energy released when fusing together or splitting up atomic nuclei for propulsion.

Spacecraft using “light-sails” pushed by lasers based in the solar system are also a possibility. However, for scientifically useful payloads this would probably require lasers concentrating more power than the current electrical generating capacity of the entire world. We would probably need to construct vast solar arrays in space to gather the necessary energy from the sun to power these lasers.

Another proposed design is an antimatter rocket. Every sub-atomic particle has an antimatter companion that is virtually identical to itself, but with the opposite charge. When a particle and its antiparticle meet, they annihilate each other while releasing a huge amount of energy that could be used for propulsion. However, we currently cannot produce and store enough antimatter for this to work.

Artist’s view of a ramjet. The enormous electromagnetic field is invisible. Image Credit: NASA

Artist’s view of a ramjet. The enormous electromagnetic field is invisible. Image Credit: NASA

Interstellar ramjets, fusion rockets using enormous electromagnetic fields as a ram scoop to collect and compress interstellar hydrogen for a fusion drive are another possibility, but these would probably be yet harder to construct.

The most well developed proposal for rapid interstellar travel is the nuclear-fusion rocket concept described in the Project Daedalus study, conducted by the British Interplanetary Society in the late 1970s. This rocket would be capable of accelerating a 450 tonne payload to about 12% of the speed of light (which would get to the nearest star in about 36 years). The concept is currently being revisited and updated by the ongoing Project Icarus study. Unlike Daedalus, Icarus will be designed to slow down at its destination, permitting scientific instruments to make detailed measurements of the target star and planets.

All current starship concepts are designed to be built in space. They would be too large and potentially dangerous to launch from Earth. What’s more, to get enough energy to propel them we would need to learn to collect and manage large amounts of sunlight or mine rare nuclear isotopes for nuclear fusion from other planets. This means that interstellar space travel is only likely to become practical once humanity has become a spacefaring species.

The road to the stars therefore begins here — by gradually building up our capabilities. We need to progressively move on from the International Space Station to building outposts and colonies on the Moon and Mars (as already envisaged in the Global Exploration Roadmap). We then need to begin mining asteroids for raw materials. Then, perhaps sometime in the middle of the 22nd century, we may be prepared for the great leap across interstellar space and reap the scientific and cultural rewards that will result.The Conversation

Ian Crawford, Professor of Planetary Science and Astrobiology, Birkbeck, University of London

Disclosure Statement: Ian Crawford is a scientific consultant for Project Icarus.

This article was originally published on The Conversation. Read the original article.

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Discussion — 14 Responses

  • Tom Riley January 27, 2016 on 12:10 pm

    The minimum mass plan is best star plan. The human genome as data is our minimum mass. Interstellar radiation is the worst enemy of our data so the genome must be encoded in a radiation resistant matrix like diamond.

    We then need to actually send a group of nanobots with the data that are capable of building bigger robots and facilities out of asteroids, which in turn can then convert the human genome back into humans.

    The rocket must be fusion powered to get there in any reasonable time. The most efficient fusion cycle fuses Boron-12 into Helium. We will need a Boron Burner.

    Then comes the really hard part. We need to redesign our society to be sustainable so that we will be available to assist in 10,000 years when word comes back that the remote process has started. This is clearly the place to start.

    I wrote a short story outlining this process a couple years ago, “They are Not Coming“.


    Tom Riley
    [email protected].

    • Paul Irwin Tom Riley January 27, 2016 on 11:22 pm

      Fuse boron into helium?

    • bt0pping Tom Riley February 11, 2016 on 10:55 am

      > We then need to actually send a group of nanobots with the data that are capable of building bigger robots and facilities out of asteroids, which in turn can then convert the human genome back into humans.

      I had a similar thought about sending the genome across space, but the conveyance of soul would be lost. The genome of Albert Einstein sent across the cosmos and reassembled by nanobots would not be equivalent to Albert Einstein arriving at the closest habitable planet and phoning home.

      It’s reasonable that AI/ML/DL/VR developed by that time could cultivate the human experience in a developing human, but it would likely grow up like a baby that had only been nurtured via FaceTime. Unless the virtual experience was so immersive that it was something like virtual training in The Matrix, it’s unlikely that the human would actually represent our species.

      If it were possible at all, I’d imagine a certain number of generations of these vat-grown humans would have to be developed in a program that their learned behavior gradually came to understand the entire cycle of life. The virtual training would have to understand the gamut of social psychology and the spacecraft would have to be big enough to cultivate the emergent culture before it reached the destination.

      This is all self-defeating if in fact (as the goals of the story say) we are intending to reach the destination “in decades”. Such a minimum mass craft would have no room for these generations of vat grown humans to be re-started. And if we are only traveling for decades with a craft big enough to hold humans, “the long nap” with highly experienced humans is a far more attractive outcome than building all these training devices and the testing that would be required on earthbound fetuses to make sure they worked when they arrived.

  • andrewbuilder January 27, 2016 on 2:51 pm

    Science fiction has, I expect unintentionally, perpetrated one of the greatest crimes to humanity. It encourages us to believe that life as humans is possible on another planet. It encourages us to take comfort in the possibility that, should we destroy this planet, an alternate existence awaits us elsewhere in the universe.

    So we continue to act recklessly on this planet our home, because our subconscious assures us that an alternative awaits.

    To be clear, my humble opinion is that life exists on other planets in our own and other galaxies.

    Even in the case that one planetary body exists that could support, or could be transformed to support, human existence, will we be capable of reaching this in time?

    To be clear, my humble opinion is that humankind will, eventually, find a mechanism that enables travel to other parts of our own and other galaxies.

    Why would we do this while we have the opportunity to make the most of our own planet? Surely it is more important to apply our intelligence and resources to properly care for what we already have?

    • DSM andrewbuilder January 27, 2016 on 7:27 pm

      Life on Earth has a use-by date simply because the sun is on track to expand as it matures and even a minor change in it’s radiation output will drive the climate into a state that cannot sustain life.

      The only way humans, and the rest of life on earth, can survive is if we can learn to survive in artificial space environments that we can fully control and place around more stable stars such as red dwarfs.

      Sure this is a long way off, but sustainable means forever, right?

      • RS DSM February 7, 2016 on 11:18 pm

        The human extinction point is a 100% certainty in the next one thousand years, assuming we win the 50/50 chance of surviving global warming. My source? Just about anyone qualified to give an opinion. They all say the same.

        But we can change, I hear you say. To which I quote Drucker: “Culture eats strategy” And Kahneman, who’s system 1 & 2 model, widely accepted, says we can’t any longer even think our way out of trouble.

        • DSM RS February 8, 2016 on 1:21 pm

          And you/they are 100% wrong because we are within reach of unlimited energy from fusion, total control of matter at the atomic level via nano-fabrication, furthermore AI will accelerate science even further.

          You would be surprised how few humans and in how small a space are required to ensure that humans, and a DNA library of all life on Earth, survive. But even if you live 1000 meters below the surface you will not survive much longer than those on the surface because the expanding sun will be so energetic that the heat will get down to you and you can’t go deeper due to the internal heat of the planet caused by natural radioactive decay.

          The problems is with thinking that we can live forever in an unchanging paradise on the surface of this planet, if only we treat it with “respect”. This is the primary delusion of environmentalism.

          The sun will expand and destroy Earth completely therefore our long term goal must be to leave it, to travel to other stars. The technologies required to do so are also the technologies required to live on the surface of any planet in the most sustainable, efficient and least disruptive way. They are also the technologies required to never need set foot on a planet again. With self sustaining star-ships of sufficient size you can build civilisations near any source of bulk hydrogen and or helium because all other matter can be synthesised from it.

          All life on earth can fit into a small pace too, we are a thin smear of carbon on the surface of a big ball of iron. Take a sheet of paper, the largest yet thinnest you can find and fold it into a long thin strip, then join the ends into a loop. Add some spin to give things weight and you have all the vast vistas of earth in a volume far smaller than Earth itself.

          The volume of Earth is 1.08321×10^12 km^3, but all of the water on it fits into only 1.332×10^9 km^3 or a volume that is only 1/16th the size of the Moon!

          There is enough mass in the Ort cloud to fabricate thousands of Biosphere scale, interstellar travelling, habitats.

          Yup, we can duplicate life on Earth a thousand fold and launch it into the galaxy, every matter rich, yet energetically quiet, spot we can find. And once those mobile Earths reach their destinations the process is repeated so that within a million years the entire Galaxy is filled with life. Even then we still only have trillions of years ahead of us because even this universe is in constant change and will become incompatible with life as we know it.

          No offence intended but, if you can’t get your head around the above you are not part of the solution you are part of the problem, regardless of how many mung beans you eat.

  • nuwri456 January 27, 2016 on 4:35 pm

    MusicLuv to ALL eyes that see read and hear this. With the technology our scientists have discovered along with the Alien technology the government has kept hidden for decades, it’s more than a reality, they are just really don’t want to expose that truth to the public, they would then have to explain all the other kept lies in the vault.
    I do music for a living but am well read on may different subjects.

    • DSM nuwri456 January 27, 2016 on 6:55 pm

      We can’t use alien spaceships because they don’t have toilets. Ever see a room or device in any of those leaked diagrams that is labelled toilet? How do you explain that huh? You can’t!

  • Kyle Cayce January 27, 2016 on 4:44 pm

    This article prediction of interstellar travel beginning in the 22nd century seems to ignore the potential of exponenyials. Isn’t that the central idea of SU?

  • Gabe Petrie January 27, 2016 on 6:51 pm


    ” If we ever found evidence suggesting that life might exist on a planet orbiting a nearby star, we would most likely need to go there to get definitive proof and learn more about its underlying biochemistry and evolutionary history. ”

    … and to do so, we would not need to send any human beings or even a large starship. We would need only to send a space probe with sufficiently powerful cameras for imaging thermal, visual and other data. After all, when we want to study life on Earth our general rule is not to interfere with the organism(s) being studied but to try and gather data from as far away as possible.

    Also, if we discover life on another planet, it would be the best of all ideas possible to simply keep it quiet for some time, probably on the scale of a few decades to perhaps a hundred years. It would be best to get a proper understanding of these life forms *before* the inevitable human stampede — going on current standards of human conduct. A large space ship mission would attract a great deal of attention and raise many questions, whereas a small space probe mission could be done without letting the public know.

    Even the mission of getting a probe there and getting it into a stable orbit could take decades, so the need for some delay in the information is self fulfilling.

    ” the cultural rewards we would get from the unprecedented expansion of human experience. ”

    Go ahead, name a few.

    “it would offer opportunities for us humans to colonize other worlds”

    Thought so.

    “Clearly, if starships are to ever become a practical reality, they will need to be based on far more energetic propulsion technologies than the chemical rockets and gravitational sling shots past giant planets that we use currently.”

    This is not true at all and displays a great deal of ignorance about how useful gravitational pull can be for completing a space mission. The reason why the probes you mentioned will cease to operate before very long is because they are already operating full-tilt and have been since their launch.

    If we were to send a space probe to a distant star using gravitational pull and a series of adjustments, we would not need anything except navigational and propulsion systems to operate until the probe reaches the distant star, at which point the probe could begin operating on solar power. That being given, we need not make any advances in propulsion considering we can accelerate the probe to amazing speeds using simple impulse drives such as a tiny laser beam. The probes we’ve sent out historically have been sent on missions to investigate the planets of our own solar system and their accelerations have been set to match the needs of navigating our busy neighborhood for the purposes of doing fly-by recon of planets and moons. This wouldn’t be necessary for a probe that is just being sent out of the solar system at an opportune moment to try to reach a distant star, and the probe could be allowed to accelerate and reach speeds within the limits of its structural stability.

    “building outposts and colonies on the Moon and Mars (as already envisaged in the Global Exploration Roadmap). We then need to begin mining asteroids ”

    Which all follows in suit with your sentiments that the best thing about space travel is expanding the horizons of the prospective human space empire. I argue that it would be far better time spent if we were to manage human life on Earth so that it doesn’t stray outside of safe parameters — “safe” for the biodiversity of Earth and the ecology of the Earth environment.

    Arguably, there’s a far better way to manage things, and I’ve maintained this model for years. “All” we need to do is cull the human population of Earth to within a few hundred million persons and regress their standard of civilization to nearly prehistoric times, and to maintain and cultivate this population by way of a space-faring, technoshamanstic theocracy. The hunter-gatherer humans of Earth would be ensured to live lives full of leisure and plenty, while the techno-religious world government in place would continue to research and develop advances in the sciences, especially focused on the exploration of space. Regular contact between the hunter-gatherers and the scientists would take the form of spiritual rituals and would serve the purpose of maintaining fresh student stock for the scientists and providing medicine and other technological artefacts for the hunter gatherers in exchange.

    A bit fascist, I admit, especially the part about decimating the human population to within a few hundred million — that’s not likely to go over well — but it arguably would work in the “looks good on paper” spirit.

    At that point, sure, I would be able to agree with you on prospects of mining the moon and the asteroids and settling other biologically active, Earth-like exoplanets. That hypothetical human civilization could be seen to be responsible and reasonable enough that they wouldn’t simply be the stereotypical slave-mining “alien race” of so much science fiction, going from world to world killing and stealing everything in site at a geometric progression.

    • CAgamefowl Gabe Petrie February 1, 2016 on 1:29 pm

      Someone just watched Cloud Atlas. Not a bad idea tho. I’d want the option to live both as a primative and as a technoshaman, immortally of course.

  • shin January 29, 2016 on 10:13 am

    Experimental EM Drive? or at least ion drives. but we must always have more than twice the accelerant necessary to go somewhere and to stop. A round trip is always at least 3 times the fuel requirements: 1)accelerate, 2)slow down, 3)returning acceleration… assuming you can be intercepted by shuttles carrying fuel to help slow you down, otherwise you need 4x the fuel. Landing on a planet is also a mess, however, the gravitational pull of celestial bodies like asteroids and moons can probably be used to reduce the total amount of fuel necessary between trips.

    Perhaps swarms of small drones that fetch meteors and dust and bring it back to some kind of filter refinery on the main ship for fuel? That would allow our future ships to basically “feed” as they travel. Torus ring habitats are a must at least during sleeping hours, and the bigger the diameter, the better. We should also have at least two escape vehicles such as landers or shuttles, capable of at least accelerating toward a safe return location, stocked with enough food, water, heating power, and air filters to get at least some of the crew back home. Every ship should also have redundancies and several surplus components, the most being air and sealant plates and chemicals for holes. We should expect any ship launched for more than 10 AUs to look like swiss cheese and be able to plug as many holes as possible. Onboard gardens, and synthetic skies may be necessary to help reduce cabin fever and isolation problems.