The science fiction trope that often comes to mind in conjunction with the interstellar ark idea is of the crew that has lost all sense of the mission. Brian Aldiss’ Non-Stop (1958), published in the US as Starship, is a classic case of a generation ship that has become the entire world. The US title, of course, gave away the whole plot, which is sort of ridiculous. Have a look at the British cover, which leaves the setting mysterious for most of the book, and the American one, which blatantly tells you what’s going on. I wonder what Aldiss thought of this.
Be that as it may, interstellar arks are conceived as having large crews and taking a lot of time to move between stars, usually on the order of thousands of years. We can trace the concept in the scientific literature back to Les Shepherd’s famous 1952 paper on human interstellar travel, a key paper in the evolution of the field. An interesting adaptation of the paper appeared in Science Fiction Plus in April of the following year (see The Worldship of 1953). Alan Bond and Anthony Martin, whose names will always evoke Project Daedalus, likewise discussed interstellar arks, and Greg Matloff, whose presentation we looked at in the last post, has been working the numbers on these craft for much of his career.
Let’s look, then, at what Matloff and Joseph Meany say in their paper on aerographite. Here we’re talking about a sailcraft driven by solar photons rather than beamed energy, one that is based on an inflatable, hollow-body sail (itself a concept that goes back at least to the 1980s). Working with Roman Kezerashvili, Matloff has in the past addressed hollow-body sails made of beryllium as well as graphene, last discussing the latter in an interstellar ark concept in 2014. Here he and Meany set up an aerographite-graphene variant using a 90% absorptive and 10% reflective layer of aerographite that effectively pushes against the Sun-facing surface of graphene.
We’re in the realm of big numbers again. The radius of the sail is 764 kilometers, with the sail massing 5.49 X 106 kilograms. The as yet unpublished paper on this work shows that the payload mass (2.56 X 107 kilograms) is considerably higher than would be possible using a hollow-body sail made only of graphene. It’s interesting that for the close solar pass envisioned in the ‘sundiver’ maneuver for the sail, Matloff chooses a perihelion of 0.1 AU in order to hold down the g forces for the human crew. The point came up in the question session after his Montreal talk, for there do seem to be technologies for sustaining (for a short period) g-forces of 3 g and beyond, which would allow for a closer perihelion pass.
In any case, our ark reaches Alpha Centauri in about 1375 years carrying a crew of several hundred. If that figure seems exasperatingly high, consider that in the past few decades we’ve gone from the routine assumption that an interstellar mission would take millennia to the now plausible suggestion that we can get it down to a century or so. Massive arks, of course, take much longer, but this number isn’t bad. NASA’s Les Johnson told me in 2003, when I mentioned a thousand-year mission, that he would love to see a plan for one that could make the journey that fast. But here we are, discussing materials and techniques that can go well below that for unmanned probes. And then there is that Breakthrough Starshot concept of 20 percent of lightspeed…
We are, in other words, making progress. But so much remains to be done with regard to this particular material. Indeed, the work on graphene reminds us how little we know about the physical properties of aerographite. The paper lays out some large questions:
- Will what we know of aerographite’s properties be sustained when we reduce the thickness to a single micron?
- Will aerographite be stable at the temperatures demanded by our perihelion calculations?
- Will aerographite equal the performance of graphene when exposed to the space environment?
- What about trajectory adjustment for a non-reflecting surface like aerographite?
Thus the paper’s conclusion:
It is wise to consider the above discussion as very preliminary. There are many unknowns regarding aerographite and graphene that must be addressed before the missions discussed can be considered feasible.
One unknown is the closest feasible perihelion distance. Just because the Parker Solar Probe will likely survive its close perihelion pass does not mean that a carbon hyper-thin sail will do the same. It is necessary for some researcher to perform an exhaustive study of the effects of the near-Sun space environment upon these substances. A good consideration of the issues to be addressed is the exhaustive study for beryllium solar-photon sails performed by Kezerashvili [9].
One last note on early aerographite sails: What interesting problems they pose for tracking. We’d have to use infrared to follow their course, and a space-based telescope to do that because of infrared absorption in Earth’s atmosphere. Heller and team figured out in their aerographite paper that JWST could track a 1 m aerographite sail out to 2 AU. But swarm configurations (and we’ll be talking about this concept again in the near future) produce a signature that could be detected well beyond the Kuiper Belt. An onboard laser would greatly simplify the problem if we could find ways to power it up aboard the highly miniaturized craft that would be our first experiments.
The paper is Matloff & Meany, ”Aerographite: A Candidate Material for Interstellar Photon Sailing,” submitted to JBIS and ultimately to be published as part of the proceedings of the Interstellar Research Group’s 2023 symposium. The 2014 paper on graphene arks is “Graphene Solar Photon Sails and Interstellar Arks,” JBIS Vol. 67 (June 2014), 237-246 (abstract). The paper on beryllium sails by Roman Kezerashvili is “Thickness Requirements for Solar Sail Foils,” Acta Astronautica 65 (2009), 507-518 (abstract).
I take back my comment yesterday about these sails as being stealthy. Clearly not nearly stealthy enough!
I do wonder about the scale-up though. Unlike a ping pong ball, an aerographite sphere will need a gas to inflate it. While it can be evacuated for a small sphere, will a large sail not need internal gas pressure to keep it inflated sufficiently to maintain its shape under acceleration forces, even gentle ones? The larger the sphere radius, the greater the mass of the internal gas to the sail mass which increases as proportional to the radius.
For large sails, would it not be better to have a classic sail design that keeps its shape through tension, rather than resisting compression? This may well mean that graphene is favored for large sails, even if aerographite proves superior for small sails.
For the immediate future, I would think that manufacturing technology will decide on the material and design. We cannot yet fabricate large areas of graphene – hence the focus on this technology for computation. Aerographite seems easier to manufacture so a small spherical sail (even a conventional kite design) might be possible sooner than graphene. Coupled with the miniaturization of the payload, this might be the easiest route to a high-performance sailcraft, if mainly used for monitoring our system out to the SGL at 550 AU.
Lastly, just how is the spherical sail going to maintain stability with a payload? A payload forward of the center of gravity will be unstable. If it is inside the sphere, how will it make observations and relay the data? Will the payload not need to be behind the sphere to make observations, even if initially inside the sphere to avoid the temperatures near perihelion?
Great questions re: configuration of the payload. I wonder if the payload infrastructure should be distributed across the sail and thereby not present a point load? Such a configuration could also be part of providing a tensioning element. If the project is crewed, they may enjoy being spread out. Also, the whole thing may need to be rotated to provide an artificial gravity experience for the crew. So I think about a torus, the ring is crew quarters and the center is the sail.
IMO, Aldiss’ novel was best entitled Non-Stop. Having recently reread the novel, the downbeat ending shows why that title is the better of the two. As the post selects just 2 covers from the many used, here is the link to all the covers for this novel. Non-Stop/Starship covers. Interesting that the jungle theme is used with both titles. [I like the German title – literally translated as Journey Without End” or “Endless Journey”]
very cool.
Very interesting post. It made me think of Aurora, the Kim Stanley novel. This story also has a sad ending and overall attitude to exploring other star systems. I’m going to re-read it and try to find Non-Stop to read as well. I tend to think there will be massive difficulties if we do ever succeed in reaching a nearby habitable exoplanet with a viable startup population. Not to say we shouldn’t try as long as we don’t kill off everything we don’t like there. Is this even possible for us?
I continue to suspect that our colonies on extrasolar planets will be orbital habitats, their crews having adapted so thoroughly to this kind of environment on their multi-generational trip outward that living on a planet is going to seem unduly stressful, if nothing else. Of course, they will one day be joined by a different kind of colonist from a much faster ship, probably living on the surface. If this happens, we will have two distinct populations of inhabitants around other stars.
So the fast hyperspace or wasp ships of Asimov and Star Trek could allow for humans also to colonize planets, while the slow, generation ships would be more conducive to space habitat living?
I have a different take. By the time we have crewed starships, almost all the human population will be living in cities, with just a small population electing to live in rural or wilderness regions on Earth. Cities, especially if they become arcologies, will be much more comfortable and interesting places to live.
KSR’s Aurora was about the dangers of surface living on exoplanets. [He was also not sanguine about the sustainability of the generation starships either, which deteriorated over time.]
With O’Neill’s logic of living in space as true today as it was in the 1970s, it seems to me that humanity will prefer to live in habitats built to meet terrestrial standards. Natural planets will be varied in conditions, and any life might be inimical to our biology. Why subject oneself to this when there’s a perfectly suited habitat to return to? Surface excursions yes, multi-year working contracts yes, but eventually a return to the habitat to live. This is the model for the crew in Vonda McIntyre’s Starfarers novels. It is also largely the model that the crew of the Enterprise has in Star Trek. Deep Space Nine is very similar – a city in space where the protagonists live between trips to Bajor. If the habitat dwellers want to simulate living on the surface, immersive views projected from the surface, with smells and sounds, might be an acceptable, and safe, substitute.
The surface of alien planets is for our robots to work in.
Paul,
Aside from bountiful scientific treasures from research on such an extra-solar structure, it’s hard to imagine any other reason to construct such a thing. I wonder what benefits accrue to such a habitat not available anywhere orbiting the Sol system?
Satisfying a human exploratory psyche comes to mind, as does the purse adventure of it. There’d be trade, of course, in some imagined FTL future; but here I run out of ideas.
And, once more thing: the collective race-memory of such an event as crossing interstellar space. How would such an event color civilization, in the broadest sense, I wonder? Such a colossal thing would have culture-level impacts, surely. But I digress.
Fascinating digression, though. Several SF novels of material here.
Great article. I have 4 points to make, confidence, target selection, experience, and project configuration.
In terms of confidence, I wouldn’t put anybody on a multi-generational flight that was operated by any organization that had not demonstrated an ability to sustain its operations over multi-generations. We need to work on developing such sustainable organizations. United Nations kinds of things.
Second, it is hard to imagine that the crew would be coming back. Ergo we need to get much better at selecting targets that offer the prospects of supporting human life. These, when found, may not be as close as current targets. Why go somewhere that you can’t come back from if you can’t look forward to colonizing?
Third, it is unlikely that any target planet will be goldilocks. Or let’s say confidence in the destination conditions will be low. Given the stakes are human lives and extraordinary project costs, we need to build many generations of experience in colonizing only marginally hospitable targets. Venus and Mars come to mind, as to some of the large moons, and even asteroids (mining).
In terms of project configuration, the ark must include at least the ability to launch at some sizable fraction of the speed of light, the size and scope to host a number of humans for 50 or more generations, the ability to decelerate the payload in the proximity of the target, and sophisticated computing/communications capabilities to either assist the human crew or replace the human crew (if lost) for some parts of the mission and to provide robust investigative capabilities.
On this last point I envision a “do everything” project configuration. The ark will consist of 3 parts which will assembled during launch and disassembled for re-purposing at the target. The transporter sail and habitation will be initially unmanned to facilitate a very close perihelion pass for maximum acceleration. This unmanned section must include all components such as the orbiter/lander to be deployed at the target, the robotic elements also to be deployed at target, and all the shielding and supplies for the journey. Since the human crew will not participate in the perihelion pass, the separate crew cockpit must be accelerated to a matching speed and docked into the transporter on its way to the outer solar system. This will involve very powerful engines, but will not need the kind of shielding and life support required for a long journey. The orbiter/lander systems must also have the same kind of inter-system deceleration and navigation capabilities as the initial crew cockpit system. This can be dropped off in the target system to begin the science missions while the arc executes a deceleration maneuver, even over many decades.
In a way the project aspects you outline might be described as a mission architecture. And it is sensible to develop a mission architecture in tandem with a project approach to set-up the industrial elements, infrastructure and long-lived organisations and funding source necessary to enable that architecture. Finally, configuration management to enure the activities and deliverables are coordinated and compatible over such a phenomenally long period of development and execution. Over many generations the crew needs to continue developing and expanding their own technologies and capabilities to remain resilient and avoid obsolescence in their isolation; that needs to be built into the mission architecture, too. After all, it is a world of it own.
I think Kim Stanley Robinson (I should have used his entire name on my last post) has it right. Things wear out. The same will be true of generation star ships. What arrives at the target world will not be anything like what leaves Earth. It will have a much degraded capacity if it arrives at all. The enormous cost makes me think we will never attempt it. I think we’re talking trillions in today’s dollars aren’t we? Small robotic missions at extremely high speeds yes, more than likely with the ability to go into orbit, but human missions? No. After all we haven’t even gotten back to the moon after 50 years. It’s ludicrous.
Just to finish the thought on human ambition and directionality let’s take a look at where we do spend trillions. On new ways to kill each other. And look at the descent into fascism happening all over the world. I used to be highly hopeful for the human future but we need to show we intend to do the right things moving forward and that doesn’t include savagery, chaos, and denial. Time to wake up as a species if we intend to have a long future. I see some signs of despair appearing in our science fiction as well. That gives me pause. I always look to SF as a guidepost to where we are heading. We are a bipolar species with some terrible destructive tendencies. Can they be brought under control? It’s all hanging in the balance I would say.
SciFi went in a rather dystopic direction several times in the past, usually coincident with the general euphoria or depression of the existing economic and social situations. We can see the existing problems and the possible/probable consequences ahead if we don’t change course, and those consequences are being explored by some SciFi authors.
It is a pity we have no equivalent of the Craig Stiles in Ray Bradbury’s The Toynbee Convector (1984) to push our collective selves in the right direction with regard the biospheric mess we are making, as well as other problems we are making or have made as a result of our collective decision making. We may well become one of the collapsed civilizations that a future Jared Diamond will write about. If so, there will be abundant material for future people to use to explain why the collapse happened.
Science fiction’s dystopian side was in full view back in the 1960s and I remember it being discussed a great deal in Barry Malzberg’s columns in F&SF in that era, among others. There has remained a pronounced dystopian streak to this day and it shows no signs of exhaustion. I have always thought that SF’s skill at predicting the future has been exaggerated, but in this case it may well have been portraying what was ahead.
My favorite SF Dystopias are the ones where everything is turned on its head. The 1950s have prime examples of these. Frederik Pohl and Cyril M. Kornbluth were the masters of these. At least I consider them dystopian , The Space Merchants and Gladiator at Law. They are set in the future but have domesticated settings. Who in the world could have thought of turning Madison avenue advertising into a dystopian universe? Pohl had worked in the late 40s and little into the early 1950s in New York advertising (apparently making quite a lot of money). Pohll and Kronbluth’s stories are wry and deceptive. Clever commentary on the world carried to a clever extremes.
Pohl wrote some stand alone longish dystopian stories that just made my jaw drop. Especially funny is The Midas Plague and Tunnel Under the World. The Midas Plague is about as upside down as one can get. The movie The Truman Show is different enough but the backbone of the story is Tunnel Under the World , I don’t know if Pohl ever complained.
Kingsley Amis , in his survey of modern science fiction, New Maps of Hell (1961), was very impressed with Pohl and Kornbluth.
You’re right, Al. Pohl and Kornbluth were devastating when working this vein of SF, and largely creating it. Gladiator at Law was something else, and I’m also thinking about some of Kornbluth’s searing short fiction. Another topic for our next symposium conversation.
Generation ships and robotic workers are reminders of a quaint and bygone future. Probably what will face us is more, and so much less, than human. Begin with https://www.frontiersin.org/journals/science/articles/10.3389/fsci.2023.1017235 – a proposal to build commercial thinking assets, “organoid intelligence”, out of human brain cells. Add in the slow advance (however crude) toward printing of other organs that would be needed to complete an intact biological system. ( https://www.asme.org/topics-resources/content/3d-printed-organs-nearing-clinical-trials ) Wrap this up in a mass of AI and robotic technology, and simmer in the philosophically bankrupt stew made with unreflecting materialism and the rejection of natural order, human dignity, and every concept of a human soul distinguishable from farm animals and computer text generators.
Served is a crew of homunculi, printed upon arrival from frozen cell stocks and electronic support components to fit any environment and mission. They are turned on with every skill they need in place, and every instilled belief and attitude to keep them on track to work day and night. Morale and obedience is not an issue; slave, shackle and whip are all one object from the molecular level up. Broiler turkeys might rebel and live free, but these things will not. And yet, they can have all the (directed and monitored) intellect of a university of humans, if those humans could transfer knowledge directly without needing to sit in classrooms and stand for exams. As I contemplate them I start to question what dark instinct ever drove us to invade the heavens or the earth.
The Frontiers article on organoid brains reminded me of a P K Dick story that starts with Martian [?] organisms that are fixed from morphing into effective brains. They are given little trolleys to provide mobility. Ugh!
However, I think the article makes some dubious claims. Firstly just because we currently build COPUs on von Neuman architectures does not require that we do. There were designs for asynchronous, unlock chips. Neuromorphic chips are not serial architectures. Similarly, GPUs and FPGAs are not serial either. Secondly, organoids provide a simple model to design neuromorphic architectures that can be conceptually scaled up to larger sizes to work more like fallible, but effective, animal and human brains. lastly, despite claims of “Moore’s Law” ending, it is clear that as Feynman suggested there is a long way to the bottom, that it should be possible to reduce CPU architectures to far smaller component sizes. Experimental work has shown that individual molecules could act as wires and possibly as state devices, and that chips could be made very much smaller if these molecules could be laid down in some fashion. So there is no reason to push for organic brains to be used, and which must still be supported metabolically.
You paint a very ghastly, “Brave New World” dystopia for seed ships. Who is going to be the elite that controls these slave humans doing all that labor? IMO, colonization is more likely to be successful with independent people. Printing up a vast range of [robotic] machines seems to be more logical than [post]humans, even if the humans are to be the controllers. There is no need to build dams with people and wheelbarrows as was once suggested of the Chinese.
I have no doubt there will be attempts to create biological horrors, especially in authoritarian regimes. However, I am encouraged that despite what is claimed about Silicon Valley culture, scientists and engineers do adhere to ethics and rules, even if some of their masters don’t. I suspect that the era of techno-elite greedheads may have run its course. Certainly, there are enough signs that the lower ranks are revolting against some of the more egregious ideas of these people.
Of course, the future you depict is centuries away, so who knows?
The “concept of a human soul distinguishable from farm animals” is the principal tool used to establish the existence of farm animals and slaves. Real easy to establish a “natural order” of lower beings undeserving of dignity if humans are the only beings possessed of a soul.
Imho, the fact that post-humans “can have all the (directed and monitored) intellect of a university of humans” and possess bodies suited to any environment is such an advancement to agency that it won’t be granted to the enslaved but adopted by humans. There goes the natural order, I guess.
I don’t believe that farm animals are truly comparable to human slaves. After all, the human slaves of any given era were free in a prior era, and their free descendants daily prove themselves our equals. When pale-skinned slave children turned up in the markets of Rome, Gregory I campaigned against slavery. He coined the phrase “non Angli, sed angeli” as his era’s counterpart to “Black is Beautiful”. Today, college students whose families are still sweeping aside the residue of centuries of slavery and prejudice prove themselves witty, brilliant, ambitious, creative; co-workers, partners, friends. None of this ever has nor ever will happen with a chicken, even a pig. I think it will soon become clear that there is not merely a quantitative difference, but a truly fundamental and remarkable distinction, between human neural networks and those of other species.
Hi Paul
This all assumes that a Star-Ark is limited by human acceleration tolerance. But what if the fast sail is detached from the Star-Ark? Use the sails as macrons to push a Star-Ark over a longer acceleration track-way. Keeping the sails going in the right direction is non-trivial, but surely worth the research investment if it shaves off centuries of travel time. Given that Greg Matloff has research the use of macrons extensively, I think it’s a worthwhile option to explore further.
Incidentally there’s a lovely visualisation of Les Shepherd’s Ark that Winchell Chung tracked down on “Atomic Rockets” here: Colony Sphere
Just wondering if it would be possible to use the design as envisaged to reduce g forces but allow higher g and velocity sails that impart their momentum on the way out. A sort of extra boost sail stream.
“Will what we know of aerographite’s properties be sustained when we reduce the thickness to a single micron?”
Personally, I’m fairly confident that, by the time you’ve got it down to a single micron thick, it will be effectively transparent.
Regular graphene only intercepts 2.3% of light per layer, after all. It seems you actually need to put a significant number of atoms in the path of a photon to stop it.
I am not so sure about that.
The distance between carbon nuclei is about 0.15 nm
So carbon materials could theoretically pack 6000 atoms in depth to create a 1-micron material. Even at 1% reflection, this results in an almost perfect 100% blocking of light. Aerographite is far less dense, but it seems to me that if the carbon atoms are highly absorptive, then just a few hundred atoms thickness on average will make the material opaque to light. Just 100 atoms would make the material over 80% opaque. Of course, the physics of the optics of aerographite may be nothing like this BoE calculation, but it may indicate that the material still has a very high absorption at just 1-micron thickness.
I agree with Kim Stanley Robinson’s assessment of world ships. Open, complex and dynamically interwoven ecosystems either don’t survive “canning” or have a short shelf-life. However, that doesn’t rule out much simpler, closed, domesticated ecosystems. However complicated an closed ecosystem can get, we are unlikely to send one to another star system until long term viability is proven. There wouldn’t be much sense installing a propulsion system on a habitat until its ecosystem is stable. Since closed ecosystems can’t demonstrate long term stability without being stable for long time spans, we are centuries or eons away from sending world ships. There will likely be a better propulsion system available 1000 years in the future.
Going back to the Brian Aldiss novel “Starship”, my copy was the 2nd edition (same cover but 50 cents) and not read for quite some time now – just a multi-generational time lapse.
Back in those days I did catch a drift in what Aldiss would write about. If I understood correctly he had spent some time in the East Indies or Indonesia back in the 1940s. And sometimes that experience would get folded back into his very imaginative stories.
Consequently, we get a jungle environment in a spacecraft engaged in interstellar flight.
Whatever element of these stories is most fanciful, it is hard to say. But the notion of a tropical reserve on its way between stars seems like an element of the unexpected. I suppose that a closed environment has to have some sort of stable regime, but a likely issue to me would be the ability to maintain an environment not freeze everything out. After all, a low velocity starship will spend most of its time in a surrounding environment of very low temperature.
If the tropical environment is sustained, it must be bled from some sort of large scale power source. It might have radiators anyway, but if power goes out, say for repairs, reboot, routine maintenance… Things could really cool down.
Perhaps the Aldiss mission started out in more of a temperate zone environment and after some thermostat failure the closed environment heated up a notch or two. But more likely the thermostat would wander farther afield: either burn up or shut down.
In other words, it seems to me that a propulsion shutdown and a power outage would be a more likely fate, extreme cold and little light in the middle of nowhere.
That’s one stage set I don’t feel comfortable exploring, but for a multi-generational ship, it’s one that the builders would have to address with some good answers.
We do have current day evidence that human spacecraft can establish thermal equilibrium for a biosphere. Decades of space station operation have demonstrated that. But I suspect that we also take a lot of that stability for granted. Gateway is not yet launched, but it would be interesting to see a report on what it had to do above and beyond what the ISS requires. In fact, beside the radiation, hanging out in a spacecraft on its way to Mars is going to be spent in the light of a dimmer and smaller sun, Spacecraft habitats heading further out with a sun getting smaller still, the supporting internal thermal sources and insulation should increase further. And then past Pluto…for gerbils, lab rats and people…
Where does the trend end?
Perhaps the low mass and high insulation coefficients of aerogel would be a candidate for limiting thermal leakage in an interstellar craft. But I don’t see much in the Starship first edition illustration to suggest its anticipation.