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A Science Critique of Aurora by Kim Stanley Robinson

I haven’t yet read Kim Stanley Robinson’s new novel Aurora (Orbit, 2015), though it’s waiting on my Kindle. And a good thing, too, for this tale of a human expedition to Tau Ceti is turning out to be one of the most controversial books of the summer. The issues it explores are a touchstone for the widening debate about our future among the stars, if indeed there is to be one. Stephen Baxter does such a good job of introducing the issues and the authors of the essay below that I’ll leave that to him, but I do want to note that Baxter’s novel Ultima is just out (Roc, 2015) taking the interstellar tale begun in 2014’s Proxima in expansive new directions.

by Stephen Baxter, James Benford and Joseph Miller

‘Ever since they put us in this can, it’s been a case of get everything right or else everyone is dead . . .’ (Aurora Chapter 2)

Stephen-Baxter

This essay is a follow-up to a review of Kim Stanley Robinson’s new novel Aurora by Gregory Benford, which critically examines the case that Robinson makes in the book that ‘no starship voyage will work’ (Chapter 7) – at least if crewed by humans. This is a strong statement, and even if the case is made in fictional form it needs to be backed up by a powerful and consistent argument. Greg criticises Robinson’s book mostly on sociological, political and ethical grounds.

Here, to complement Greg’s analysis, we take a critical look at the science in the book. Is Robinson’s ship a plausible habitat for a centuries-long voyage? Could the propulsion systems function as described? Is the planetary threat encountered by the would-be colonists biologically plausible?

This entry is mainly the initiative of Jim Benford, well known to readers of this blog; Jim is President of Microwave Sciences based in Lafayette, California, and his interests include electromagnetic power beaming for space propulsion. Also contributing has been Joseph Miller, biologist and neuroscientist, previously of the University of Southern California Keck School of Medicine, now at the American University of the Caribbean School of Medicine, with a long-time interest in extraterrestrial life. As for myself, I’m a science fiction writer, part-time contributor to such technical projects as the BIS-initiated Project Icarus, and author of some interstellar fiction myself, such as Ark (2009). And as the full-time writer I’m the one who got the privilege of writing up our conversations. Thanks, guys!

I should start by saying that Stan Robinson has been on my own (very short) list of must-read writers for the last twenty-five years at least, and that Aurora is a key book, as with all Robinson’s work deeply researched and deeply felt. If you haven’t bought the book yet, do so now.

Basics

Aurora is a tale of a multigeneration starship mission to Tau Ceti. (Note that Robinson’s starship is unnamed; here I’ve referred to it as ‘the Ship’.) The Ship reaches its target, but when it proves impossible to colonise the worlds there, a remnant of the crew struggles back to Earth.

This review is an analysis of technical and science aspects of this mission, based solely on evidence in the novel’s text. Of course any errors or misreadings of Robinson’s text are our sole responsibility.

We’ll be making comparisons with two classic studies. The BIS’s Project Daedalus (1978) was a study of an uncrewed interstellar probe which used the same fusion-rocket technology as did Robinson’s Ship in its deceleration mode. Daedalus had initial mass 50,000t (tonnes) of fuel (30kt deuterium (D), and 20kt helium-3 (He3)), the dry mass of its two stages amounted to 2700t, the payload was 450t, and the exhaust velocity was about 3.3%c, with cruise velocity 0.12c (c being the velocity of light). The Daedalus propulsion system was used only for acceleration; it couldn’t decelerate, and so was a flyby mission at its target star. In Aurora the Ship uses its fusion rocket only to decelerate.

Meanwhile the ‘Stanford Torus’ space habitat design (Johnson, 1976) was a product of a 1975 workshop involving NASA Ames and Stanford University. The final design was a torus 1790m across with the habitable tube 130m in diameter. Of a total surface area of about 2.3km2, 10,000 people would inhabit a usable surface area of about 0.7 km2. The station, located at L5, would be built of lunar resources. The total mass would be about 10 million t, of which 9.9 million t would be a radiation shield of lunar slag around the habitable ring in a layer 1.7m thick, leaving 0.1 million t as structural mass. The relevance to Aurora is that the Ship looks like two Stanford Toruses attached to a central spine.

Let’s begin by looking at the Ship’s construction and inhabitants.

The Ship

Construction

Most of what we learn about the Ship’s structure is given in Chapter 2. The Ship consists of a central spine 10km long, around which 2 rings of habitable ‘biomes’ spin, torus-like. Each ring consists of 12 cylindrical biomes, each 4km long, 1km diameter. There are also spokes and inner rings. The rings rotate around the spine to give a centrifugal gravity of 0.83g.

The 24 biomes contain samples of ecospheres from 12 climatic zones: Old World versions in one ring, New World in the other. Each biome has a ‘roof’ with a sunline, which models the required sunlight and seasonality, and a ‘floor’ on the side away from the spine. The liveable area in each cylinder is given as about 4 km2, which is about a third of the cylinder’s inner surface area: 96km2 total. In each biome there are stores under the ‘floor’, including fuel; we’re told this is used as a radiation shield during the cruise.

rotor station

The total habitable space is allocated as 70% agricultural; 5% urban / residential; 13% water; 13% protected wilderness. The wilderness areas are meant to be complete ecologies.

The crew numbers given appear contradictory; in some places Robinson states there are about 2100 total, but elsewhere is given a number of 300 people per biome which would total 7200. The crew numbers do vary through the centuries-long mission, with births and deaths.

How reasonable are these numbers, given the mission’s objectives? Could the Ship support that many people? Are they enough to found a human population at the target? And is there room for true wilderness?

Closed Ecologies

We don’t yet know how to maintain closed ecologies for long periods. The Ship’s biomes would suffer from small-closed-loop-ecology buffering problems, as Robinson illustrates very well in the text; we see the crew having to micro-manage the biospheres, and dealing with such problems as the depletion of key trace elements through unexpected chemical reactions. In some ways this may prove to be an even more daunting obstacle to interstellar exploration than propulsion systems.

Human population

If there are 300 people per biome, and given a total of 96km2 habitable area, that’s a population density of 75 /km2. Compare this with Earth’s global average of 13 /km2 ; crowded southern England is 667 / km2. In terms of the ability of the agricultural space (70% of total) to support the crew, that seems reasonable to us.

But if only 5% of the space is used for residential purposes, the effective living density is high, at 1500 per km2 – comparable to densely populated urban areas such as Hong Kong. Such densities would seem problematic on a long-duration mission, though of course the crew do have access to the other 95% of the habitable areas; people hike the wildernesses.

This group is of course meant to be sufficient to found a new human breeding population on a virgin world. What is the minimal population size to maintain the species without an evolutionary bottleneck? Something like 1000 is a good guess. Robinson’s original population was at least twice that. If that population size was maintained, genetic diversity would plausibly be sufficient.

‘Wilderness’

We’re told (Chapter 2) that each biome has about 4km2 of living space and that 13% of that space is given over to ‘wilderness’, that is 0.52 km2 per biome. The ecologies can include apex predators. In a biome called Labrador, for instance, ‘In the flanking hills sometimes a wolf pack was glimpsed, or bears’ (chapter 2).

This idea is explored in more depth in Robinson’s 2312, in which mobile habitats called ‘terraria’, hollowed-out asteroids, are used as reserves for species threatened on a post-climate-change Earth. But even these terraria are not very large in terms of the space needed by wildlife in nature. A wolf pack, consisting of about 10 animals, may have a territory of 35 km2 (Jędrzejewski et al, 2007). A 2312 terrarium with an inner surface area of about 160 km2 would have room for only about 4 packs, or about 40 individual animals, a small population in terms of genetic diversity.

It seems clear that the much smaller biomes of the Ship, though large in engineering terms, would be far too small to be able to host meaningful numbers of many animal species in anything resembling a natural population distribution. A wilderness needs a lot of room.

Mass

We are given a mass breakdown for the Ship as a whole. We’re told that during the Ship’s cruise phase, when it is fully laden with fuel, the total mass is 76% fuel, 10% each biome ring, and 4% the spine.

We aren’t told the Ship’s total mass, however, and to study the propulsion system’s performance we’ll need at least a guesstimate. This is derived by a comparison with the Stanford Torus design.

Each torus-like biome ring consists of 12 pods of length 4km, diameter 1km. So the surface area of 1 pod is 14.1 km2, including end caps. And the surface area of one biome ring is 170 km2 (which is much larger than the Stanford Torus).

The Ship’s biomes seem to lack a Stanford-like cloak of radiation-shielding material. Robinson says that ‘fuel, water and other supplies’ are stored under the biome floors to provide shielding; the ceilings are shielded by the presence of the spine. Elsewhere Robinson says that during the voyage, the fuel is ‘deployed as cladding around the toruses and the spine’ (Chapter 2)

Assume then that if a Ship biome ring has the same structural properties as the Stanford torus, and if most of its mass is in the hull, then a guesstimate for a single ring mass (without the fuel cladding) can be obtained by multiplying Stanford’s 0.1m tons structure mass (without shielding) by a factor to allow for the Ship ring’s larger surface area. The result is (0.1 * 170 / 2.3 =) 7.4 million tons per biome ring. We know this is 10% of the Ship’s total mass, which therefore breaks down as

76% fuel = 56.2 million tons
20% biome rings = 14.8 million tons
4% spine = 3 million tons
Total = 74 million tons.

These numbers shouldn’t be taken seriously, of course, except as an order of magnitude guide. Maybe they seem large – but remember that Daedalus needed 50,000t of fuel to send a 450t payload on a flyby mission to the stars, a payload comparable to the completed mass of the ISS. By comparison the Ship will be hauling two habitat rings each fifteen kilometres across. This is not a modest design.

Notice that if the Ship’s propulsion follows the Daedalus ratio, the fuel would consist of 60% D = 33.7m tons, 40% He3 = 22.5m tons.

And notice that since this fuel is used for deceleration only, the acceleration systems need to push all this mass up to ten per cent of lightspeed. These numbers do illustrate the monstrous challenges of interstellar travel, with a need to send very large masses to very large velocities, and decelerate them again.

On that note, let’s consider the propulsion systems.

Propulsion

Mission Profile

The Ship is a generation starship. Launched in 2545, it travels 11.8ly (light years) to Tau Ceti at cruise 0.1c (chapter 2). According to the text the journey consists of a number of phases.

  • The Ship is accelerated to the cruise speed of 0.1c by means of electromagnetic ‘scissors’ slingshot at Titan, imposing a brief’ acceleration of about 10g, and then a laser impulse for 60 years.
  • The Ship decelerates at the Tau Ceti system using its on-board fusion propulsion system. The technology, like that used by Daedalus, is known as ‘inertial confinement fusion’ (ICF), in which pellets of fuel are compressed, perhaps with laser or electron beams, until they undergo fusion; the high-speed products provide a rocket exhaust. For twenty years the Ship is decelerated by the detonation of fusion pellets at a rate of two per second. The fusion fuel is a mix of D and He3, as was the case for Daedalus (Chapter 1).
  • We’re told that the total journey time is about 170 years (Chapter 3), consistent with the profile given.
  • Colonisation in the Tau Ceti system is attempted and fails (this will be considered below).
  • A section of the crew chooses to return to the Solar System. The ICF system is refuelled at Tau Ceti, and used to accelerate the Ship to 0.1c (Chapter 5).
  • As the Ship’s systems break down, the surviving crew completes the final leg of the journey in cryosleep.
  • The Ship has no onboard way to decelerate at the Solar System (Chapter 6). The ICF fuel was exhausted by the acceleration from Tau Ceti, save for a trickle to be used during Oberth Manoeuvres (see below). The laser system reduces the Ship’s speed, but not to rest: from 10%c to 3%c. We’re told that the Ship then sheds the rest of this velocity mostly with 28 Oberth Manoeuvres, using the gravity wells of the sun, Jupiter, and other bodies. This process takes 12 years before crew shuttles are finally returned to Earth.

We can consider these phases in turn.

Acceleration from Solar System

In considering the acceleration system, it should be borne in mind that what we need to do is to give a very large, fuel-laden Ship sufficient kinetic energy for it to cruise at 0.1c. And because of inevitable inefficiencies, the energy input to any acceleration system will have to be that much greater.

In fact the launch out of the Solar System is a combination of two methods, vaguely described, neither of which is remotely efficient. There’s a ‘magnetic scissor’ that accelerates the ship over 200 million miles: ‘…two strong magnetic fields held the ship between them, and when the fields were brought together, the ship was briefly projected at an accelerative force equivalent to 10 g’s’.

(Of course such acceleration would stress the crew, even though in tests humans have survived such accelerations for very short periods – indeed the book claims five crew died. And such acceleration could stress lateral structures, such as the spars to the biome rings. Perhaps the stack is launched with its major masses in line with the thrust, and reassembled later.)

In Jim Benford’s grad school days, he ran some actual experiments on this effect, using a single turn coil. The energy in the capacitor bank driving it was about 1 kJ and the subject of the acceleration was a screwdriver sitting on a piece of wood in the coil centre. The coil current pulsed to peak in 2 µs. The screwdriver was accelerated across the room to a target at about 10 meters per second. The kinetic energy of the screwdriver was about 5 J and therefore the efficiency of transfer was less than 1%. It seems unsafe to assume an efficiency much better than this.

For the Ship, there then follows a laser driven acceleration. While lasers can certainly accelerate light craft, as has been shown experimentally, they can’t accelerate the enormously massive vehicle that the novel describes. The power required to accelerate by reflection of the laser photons can be calculated from the Ship mass (74 million tons), final velocity and acceleration time (to 0.1c in 60 years, so 0.17% g). The amount of power is about 100,000 TW, a truly astronomical scale. (Earth’s present electrical power output is 18 TW.) The efficiency of power beaming is low because only momentum is transferred from the photons to the ship. Efficiency is the time-averaged ratio of velocity to the speed of light. Therefore the efficiency of this process is about 5%.

The Ship and its mission would have to be a project of a very wealthy and very powerful interplanetary civilisation. It seems unlikely that they would resort to such a hopelessly inefficient system, if it could be made to work at all.

Deceleration at Tau Ceti

The Ship uses its onboard fusion rocket to decelerate.

We’re told the ICF deceleration phase takes 20 years at 0.005g, starting from 10%c cruise speed, with a Ship with an initial fuel load of 76% total mass. These numbers enable us immediately to calculate one critical number, the exhaust velocity of the fusion rocket. A ship with 76% fuel mass has a mass ratio (wet mass / dry mass) of (100/24=) 4.17. The rocket equation tells us that given that mass ratio and a total velocity change of 0.1c, the exhaust velocity must be 7%c. This is twice that of Daedalus, but perhaps not impossible for an advanced ICF system.

Our mass guesstimate above allows us to assess the performance of the rocket. Consuming 56.2mt of fuel in 20 years gives a mass usage rate of 94 kg/sec (cf Daedalus first stage 0.8 kg/sec). (Notice that the two fusion ‘pellets’ consumed per second are pretty massive beasts; in the Daedalus design pellets a few millimetres across were delivered at a rate of hundreds per second. This detail may be implausible. Indeed 49kg may be larger than fission critical mass!)

You can find the rocket’s thrust by multiplying mass usage by exhaust velocity, to get about 2000 MN (megaNewtons). This is much larger than the Daedalus first stage’s 8 MN. And the rocket power is 20,000 TW (the Daedalus first stage delivered 30 TW). Note that this power number is comparable to the launch figures.

Again, these numbers can be taken only as a guide. But you can see that the power generated needs to be maybe three orders of magnitude better than Daedalus, and exceeds our modern global usage by four orders of magnitude.

Meanwhile this system would consume a heck of a lot of fusion fuel. Where would you acquire that fuel, and where would you store it?

The storage is the easy part, relatively. Daedalus’s 50 kt of fuel was stored in six spherical cryogenic tanks with total volume 76,000 m3. At similar densities to store the Ship’s fuel load would require 860 million m3. That sounds a lot, but the volume of a biome ring is about 38 billion m3, so the fuel volume is only 2% of this, making it plausible that it could be stored, as Robinson says, in cladding tanks on the biome rings and spine, without requiring large separate structures. The Ship is big but hollow. It’s not immediately clear however how effective a layer of fuel would be as a cosmic radiation shield.

And note that the need for cryogenic store over centuries before use would be a challenge – as would the need to store any short-half-life propulsion components such as tritium, which has a half-life of 12.3 years, and would decay away long before the 170-year mission was over.
Getting hold of the fusion fuel, meanwhile, is the tricky part. It’s hard to overstate the scarcity of He3 in the Solar System, and presumably at Tau Ceti. Even Daedalus’s 20,000t would deplete the entire inventory of the isotope on Earth (37,000t), and the Ship’s 22.5mt would dwarf the Moon’s store (1 million t); only the gas giants could reasonably meet this demand (the Daedalus estimate was that the Jovian atmosphere contains about 1016 t). The Daedalus design posited acquisition from Jupiter, but estimated that to acquire Daedalus’s fuel load in 20 years would require that the Jovian atmosphere be processed at a rate of 28 tonnes per second. So again the challenge for the Ship’s engineers will be three orders of magnitude more difficult.

And regarding the return journey, although the Ship is stripped down, a fuel load of similar order of magnitude must be acquired from the Tau Ceti system, and without the assistance of a Solar-System-wide infrastructure. Of this huge project, Robinson says only that ‘volatiles came from the gas giants’ (Chapter 4).

Deceleration at Solar System

At the end of the novel, the Ship returns to Earth, decelerating mostly using what is called the ‘Oberth Manoeuvre’, invented by Hermann Oberth in 1928. This is a two-burn orbital manoeuvre that would, on the first burn, drop an orbiting spacecraft down into a central body’s gravity well, followed by a second burn deep in the well, to accelerate the spacecraft to escape the gravity well. A ship can gain energy by firing its engines to accelerate at the periapsis of its elliptical path.

Robinson wants to use this to decelerate from 3% of light speed down to Earth orbital velocity. 3% of lightspeed is 9,000 km/s. For reference, Earth’s orbital velocity is 30 km/s. Several deceleration mechanisms are referred to in the book. An unpowered gravity assist, passing by the sun and reversing direction, can steal energy from the sun’s rotational motion around the centre of the galaxy. That’s worth about 440 km/s. Other unpowered gravity assists can be used once the ship is in a closed orbit in the sun’s gravitational well. Flybys for aerobraking in the atmospheres of the gas giants are referred to as well. Altogether, these can get you <100 km/s.

But the key problem with using the Oberth Manoeuvre for deceleration of this returning starship is that this craft is on an unbound orbit. That means that, on entering the Solar System its trajectory can be bent by the sun’s gravity, but will then exit the System because it has not lost enough velocity to be bound to the Solar System. To be bound would require velocity decreased down to perhaps 100 km/sec, which is 1% of the incoming velocity. Therefore 99% of the deceleration has to take place in the first pass. And you can’t get that much from an Oberth Manoeuvre.

Cryosleep

As the Ship’s systems collapse, the returning crew gets from Earth plans to build a cryonic cold sleep method, which allows the viewpoint characters to survive until they reach the Earth.

This technology logically undermines most of the problems the early parts of the novel confront, and therefore undermines most of Robinson’s point about the difficulty of interstellar travel: If only the colonists had waited a few centuries for cryo technology, it would all have been so much easier! But this contradicts Robinson’s thesis.

Aurora

Having arrived at Tau Ceti, the colonists’ target planet, called Aurora, is judged lifeless but habitable from a remote sensing of an oxygen atmosphere – presumed created by non-biological process billions of years ago – but in the event the environment proves lethal for humans because of the presence of a deadly ‘prion’.

In a sense this is the point of the novel, that even if we reach the stars we will find only dead or hostile worlds: ‘I mean, they [alien worlds] are all going to be dead or alive, right? If they’ve got water and orbit in the habitable zone, they’ll be alive. Alive and poisonous . . . What’s funny is anyone thinking it [interstellar colonisation] would work in the first place’ (chapter 3). And as Greg noted in his essay this reflects recent misgivings expressed by Paul Davies and others about the habitability by Earth life of exoplanets.

Is this reasonable? And is Robinson correct that this could be the solution to Fermi’s famous paradox?

Robinson seems to be saying ‘alive’ worlds will be toxic to all possible biological explorers (there is a little wiggle room here since non-biological automated probes might still survive such worlds). This is a bold statement, but plausible since we lack any relevant data. However Robinson also says ‘dead’ worlds, essentially rocky Earth-size planets in the Goldilocks zone, could be terraformed but that project would take thousands of years. But why should that matter in a galaxy that is billions of years old? There should be plenty of time to terraform such planets, either by biological explorers or perhaps some type of self-replicating von Neumann probes or seed ships. There appears to be no solution in Aurora to Fermi’s question.

Oxygen and Biosignatures

(See Sinclair et al (2012) for a relevant reference.)

It seems implausible that oxygen in Aurora’s atmosphere might not be a biosignature: that is, that it could credibly be created by non-biological processes. Without some continual input into the atmosphere, you would expect any oxygen to rust out, as on Mars. Robinson says the oxygen on Aurora is due to the ultraviolet breakdown of water. We haven’t run the numbers, but that would be a hell of a lot of UV (which itself could make the planet uninhabitable). That might actually work better as a mechanism for oxygen production on Mars, at least long ago when Mars had liquid water. Indeed, UV is how Mars lost its water and atmosphere, and the same would happen on a dead Earthlike world. So Aurora can’t have oxygen; it gets blown off after the hydrogen from water.

Robinson also cites a failure to detect CH4 and H2S, possible markers of life, in Aurora’s air as ruling out a biological origin for the oxygen. However the interpretation of the presence of methane (CH4) in the Martian atmosphere has been a bone of contention for well over 15 years. Is it a biomarker or an index of geological activity? And as far as hydrogen sulphide goes, it sure as hell is not a biomarker on Io!

The ‘Prion’

The most significant biological problem in Robinson’s scenario is the organism that was so toxic to humans on Aurora. This is said to be ‘something like a prion’, and is apparently an isolated organism: as far as the explorers could tell there simply was no wider biosphere on Aurora.

For a biologist, that sounds really weird. This is a satellite a couple of billion years older than Earth and the only evolved organism is a prion? In addition we are not sure what ‘something like’ really means, but if it was indeed like a prion one must ask: where on Aurora are the proteins capable of being misfolded by a prion action? That’s what prions do; they cannot exist in isolation. And then why was it that human proteins, from a different biosphere altogether, were such a good match to the prion’s mechanisms?

Of course you can say it was ‘something like’ a prion but not really a prion. But then, what makes it ‘like’ a prion if not protein-folding?

It would take a lot more detail to make this strange single-organism biosphere a plausible ecosystem. Maybe if Robinson ever revisits Aurora and the stayers we could find out! Joe Miller thinks that an Andromeda Strain-like organism, inimical to Earth biology, is no more or less likely than ET organisms which simply find Earth biology indigestible. We don’t know, but the possibility that ET biology would be simply oblivious to Earth biology is a plausible situation, though not treated very much in SF because it is not very dramatic!

Conclusions

Robinson’s Aurora is a finely crafted tale of human drama and interstellar exploration. Its polemic purpose appears to be to demonstrate, in Robinson’s words, that ‘no [human-crewed] starship voyage will work’. There is much of the science and technology we haven’t explored in this brief note; there’s probably a master’s thesis here – indeed I’ve recommended the book to Project Icarus as a study project.

However, to summarise our conclusions:

  • The human crew transported to Aurora may plausibly be large enough to support a new breeding population. And the Ship’s dimensions seem adequate to support the crew through their centuries-long mission.
  • The challenge of maintaining small closed biospheres is depicted credibly, but the ‘wilderness’ areas of the biome arks are too small for their purpose.
  • Of the elements of the propulsion system, the electromagnetic / laser Solar System acceleration system needs to be so powerful it stretches credibility, while the Oberth Manoeuvre return-deceleration system as depicted is impossible. The ICF fusion rocket system appears generally credible, but would require the acquisition of heroic amounts of helium-3 fuel, a challenge especially at Tau Ceti.
  • Regarding Aurora itself, the notions of a non-biogenic oxygen atmosphere, and of a single-organism biosphere, and that an extraterrestrial organism as described might necessarily be inimical to humans, all lack credibility.

In summary, while Aurora is an intriguing combination of literary, political, scientific and technical notions, and while it reflects many current speculations about the difficulty of interstellar travel, in many instances it lacks the supporting credible scientific and technical detail required to make its polemic case that human interstellar travel is impossible. The journey is not plausible, and nor is the destination.

What Aurora illustrates very well, however, at least at an impressionistic level, is the tremendous difficulty of mounting such a voyage. Interstellar travel is a challenge for future generations, which will bring both triumph and tragedy.

References

Kim Stanley Robinson, Aurora, Orbit, 2015.

Kim Stanley Robinson, 2312, Orbit, 2012.

Bond et al, Project Daedalus Final Report, British Interplanetary Society, 1978.

Johnson, Richard D. and Holbrow, Charles, (editors), ‘Space Settlements: A Design Study’, NASA SP-413, 1977.

Jędrzejewski W, Schmidt K, Theuerkauf J, Jędrzejewska B, Kowalczyk R. 2007. ‘Territory size of wolves Canis lupus: linking local (Białowieża Primeval Forest, Poland) and Holarctic-scale patterns’. Ecography 30: 66–76.

Sinclair, S., Schulze-Makuch, D., Radley, C., Papazian, A., Miller, J., Marzocca, P. Lee, J., Gaviraghi, G., How to Develop the Solar System And Beyond: A Roadmap to Interstellar Space, Kindle Books, 2012.

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  • Joseph Morris August 14, 2015, 10:45

    I’m an SF writer (if only a self-published one),but I am also somewhat of an amateur historian, which puts me into a paradox. As an SF writer I’m supposed to predict the future, particularly that of science and technology, while my historic experience tells that is impossible. The history of science and development on this world is one of creative destruction, where whole new technologies emerge and destroy the older ones: a la the automobile and the horse and buggy. The industrial revolution totally upended the 16th and 17th century artesian. Malthus predicted a world overpopulation and starvation because he couldn’t foresee the rise of winter wheat, fertilizers, and other agricultural advancements that are feeding the world today,

    The job of an SF writer is to explore the future. However, if one limits oneself to mere extrapolations of existing technology, then you’re not writing a science fiction novel, you’re just writing some future prediction of current history and trends. I’m guilty of this in my novels but the one thing I won’t do is let it give up the hope of extending ourselves somehow into the galaxy. Physics is littered with people who said and proved things are impossible and who bathed in the orthodoxy of today’s beliefs.

  • ole burde August 14, 2015, 11:39

    Stephen Baxter does a great job of analyzing ” Aurora” … thorough , fair rational and NICE is the password .
    The problem is , that anybody such an myself who believes in reaching for the stars now increasingly faces an OPPONENT that is anything but nice , it actualy looks more like a concerted effort to destroy the ETHOS of spaceexploration by stealing and poisoning its symbols and narrative traditions .
    So , perhaps NICE is not the answer ..
    Kim Stanley Robinson seems to have been ”infected” by an upgraded version of the ideological virus that was described so well in Larry Nivens ‘Fallen Angels’ .
    In this book , a ‘green” political movement gains power by OPENLY being against technology and progress . What Robinson tries to advance is a much more advanced version of the virus that was , perhaps for the first time , seen in the big-time Hollywood movie Avatar . Now we have more dangerous ideology which does not openly make frontal assaults on Progress , but only attacks specific aspects of progress and technology when this can be made under the protection of Hollywood or other powerplayers .
    Try reading the latest Scientific American , you will find an article that proves my point .

  • RobFlores August 14, 2015, 11:53

    It seems to me that KSR is a Solar System flogger. His perspective must be that the human race will eat, sleep and die in the confines of the solar
    system. It is a fair argument that for at least 4 billion years the solar system
    will provide all the necessary living space the human race might ever need, even accounting for the migration of the habitable zone.
    But I think KSR is missing a key element in his analysis. One colonization attempt may fail. But the human race will keep on trying.
    Why?. Because it will one the few challenges humanity will have.
    Think about it. 400 years from now. Envision 200 year life spans. No
    disease. Automated systems taking 90% of the drudgery out of existence.
    That leaves very little of actual potential achievements left to humanity. Defeat at one attempt to colonize is not going to stop it’s attempt. They will take lessons from the defeat. Maybe next time they launch Several colony ships with better prospects.
    I am pretty sure that for every successful colonizing group expanding across seas or hostile lands on Earth, more than a handful of groups have perished.

  • Charlie August 14, 2015, 15:10

    These are very important questions that I have asked in the past. And it concerns whether or not there exist sufficient backup and redundancies in all the systems such as to make a voyage even feasible. Psychological aspects seem to be something which may be a showstopper are multigenerational ships. Someone on here made a brilliant suggestion that it might be best to send a multitude of different ships, each within sight of one another with different types of colonist. The reasoning here was that by having a multitude of different ships, if an individual became bored the individual could simply migrate between the ships get a fresh perspective. That’s something that ought to be thought about Seriously! You can get awfully tired of looking at the same old faces.

  • Abelard Lindsey August 14, 2015, 15:25

    I think Robinson is right in saying that alien life is likely to be toxic for humans.

    In any case, we’re not going to the stars until we’ve developed an “O’neill-style” solar system wide civilization over the next few centuries. Robinson’s timing of his “Aurora” trip starting in the 24th century seems about right to me.

    We have to develop biomemes (closed ecologies) for space colonization anyways (SSI has identified this as a key technology). This will take time as it can only be done through lots of trial and error, maybe 50-100 years. The good news is that the biomemes do not have to be exactly 100% to start with as we can mine asteroids for key materials that our biomemes run out of. Over time, and through much experimental trial and error, we will get biomemes that are pretty close to 100%.

    Unless we get FTL, I think the issue of interstellar travel to be moot. By the time we do it, we will have been living in space colonies for a good 2-3 centuries and will consider them to be “home”. i think it unlikely that such people will go through the hassle of generational star travel just to settle an “Earth-like” world.

  • Hop David August 14, 2015, 15:58

    “An unpowered gravity assist, passing by the sun and reversing direction, can steal energy from the sun’s rotational motion around the centre of the galaxy. That’s worth about 440 km/s.”

    For a hyperbolic path, inbound Vinfinity and outbound Vinfinity have the same speed. It’s direction that is changed. A change of direction with regards to the sun can result in a change of speed with regard to galactic center. But no change in speed with regard to the sun. So no 440 km/s delta V for decelating into solar capture.

    “…while the Oberth Manoeuvre return-deceleration system as depicted is impossible.”

    Correct.

    Ordinarily velocity at periapsis is a lot higher than Vinf. Since energy scales with square of velocity, a small burn at periapsis usually results in a big energy gain. But in this case velocity at the bottom of the gravity well is so little different from Vinf that the Oberth gain is neglible. A hyperbola’s speed is sqrt(Vesc^2 + Vinf^2). In this case Vinf is much, much higher than Vesc. Even if the perihelion were sun grazing, Vesc would only be around 600 km/s. About 7% of the 9,000 km/s Vinf.

    Robinson’s science is abysmal. If he’s making at stab at had SF he should learn some math and physics.

  • Coacervate August 14, 2015, 16:21

    The SF I would like to read incorporates all of the sciences. As various disciplines continue to converge we can pause to anticipate what human beings (a self-domesticated species) will become (self-evolved trans-bionic species).

    A good writer should see todays political mess, project through the next world war that, to me at least, seems inevitable (or a creative way to defuse it!) and spring board from there to a kind of Earth 2.0 with new ethics, new imperatives.

    Nothing is worth reading if it does not have the capacity to change the way we think…in a positive way.

  • Coacervate August 14, 2015, 17:27

    I might be fun to list some bullet points for a starship senario:

    * The ship should be alive in the sense it can repair itself against metoroid breach, provide life support to itself and the onboard ecologies.

    * use of suspended animation

    * novel advances in ethics/believe systems …read rejection of superstition

    * novel sources of energy… do we know enough about Kasimir Effect or Dark stuff to make some guesses? obviously I do not :)

    * analogies with polynesians. What motivated? what was their success rate?

    I’m probably all wet. Ray Bradbury once wrote to the effect that the author of a good SF story makes a deal with the reader…”Just give me this one plausible possiblity and set it as reality and I’ll tell you what could happen.” I’ve always loved that sentiment but spinning a grand tale of H. sapiens’ stellar future may require more than one “deal”.

    thanks for indulging my mutterings

  • Astronist August 14, 2015, 18:25

    Worth noting that helium-3 is no longer needed for a fusion pulse engine, making fuel acquisition very much easier. The breakthrough was made by Robert M. Freeland, a member of the Icarus team:
    http://www.jbis.org.uk/paper.php?p=2013.66.290

    Stephen
    Oxford, UK

  • Astronist August 14, 2015, 18:36

    Regarding the comment by Joseph Morris above: the job of an SF writer to explore possible futures does not necessarily commit him or her to portray seemingly magical technological breakthroughs. The fact that such disruptive changes have been occurring over the past couple of centuries does not prove that they will continue to happen in the future. A future scenario based only on physics we know today is a perfectly possible future.

    Robinson has clearly chosen to portray a future in which technological progress has run out of magic. It’s his privilege to make such speculations, and has generated an interesting debate.

    Stephen
    (also, as it happens, a self-published SF writer)

  • Ron Smith August 14, 2015, 21:19

    This article mentions something that I’ve always been curious about, but never seen anyone try to address: Is it more likely that alien organisms will find each other indigestible, and thus have no effect on each other, or will new arrivals be so lacking in defenses, i.e. immunities, that the number of simple decay organisms will overwhelm and destroy any new arrival (as in Wells War of the World)?

  • Joseph Morris August 14, 2015, 22:45

    @Astronist: You might be right but I don’t think so. It would be arrogant of us to think we’re at the end, that there’s nothing left for us to break through. But even if I’m wrong, there are dangers in trying to extrapolate on existing technology as the comments here show. I’ve never been into generation ships because in my mind they’re and admission of failure, that we have hit a limit, that in reality we’re trapped in this solar system. It goes against what makes us human — the ability to dream, to explore, and to beat the odds.

  • Brett August 15, 2015, 2:50

    I’m reading the book now, and it’s a good read. I’d add a couple of points-

    1. It’s crazy that they’re actually relying on the biomes for food, air, water, and so forth. They even admit that the ship itself is vastly more robust and sturdy than the ecosystems it carries, so they should be operating basic life support as a fully artificial ship-board system while keeping the biomes as living preserves for life and diversity they’ll need at the destination (and also possibly to preserve the sanity of the intergenerational crew).

    @Charlie

    And it concerns whether or not there exist sufficient backup and redundancies in all the systems such as to make a voyage even feasible.

    It’s all speculative at this point, but if you really wanted to be safe you’d send the ship with the capability and resources to effectively re-build itself several times over in mid-transit.

    2. I’m not so sure going with 24 biomes was a good idea from a design stand-point. It might have been smarter if they’d done four biomes, but made them much larger (allowing for more biomass and better diversity in each). I’m thinking a “Warm Wet Biome”, “Warm Dry Biome”, “Cool Wet Biome”, and “Cool Dry Biome”.

    3. The whole thing with the “prions” makes sense to me. It’s not that they were somehow attacking human cells – it was that the colonists were walking masses of warm, wet living space full of organic materials. So they’d plunk down inside of their bodies, and said colonists’ bodies would react with an immune system reaction that eventually killed them trying to fight off the foreign objects (the fever).

    4. I don’t see the colony ship idea as futile, especially since it was an extension of their existing habitats (the terraria). That would make a lot more sense to a society used to living long-term in space habitats than it does to us. It’s just that they were eventually outpaced by technology, which happens – and which is a perennial issue for any sort of long-distance generation ship transport proposal.

  • Joy August 15, 2015, 3:06

    In Alastair Reynold’s Revelation Space universe, Yellowstone was first settled by a robotic ship. The ship carried human embryos in cryo storage, which were thawed and growth in artificial wombs. The babies were then raised by robotic nannies. Of note, Reynolds does note that humans raised by robots might not be psychologically normal.

    Still, this approach solves many problems. Human embryos are lightweight, and we already have the means to store them. If a ship can carry one human embryo, it could carry a million. Only the embryo storage need to have maximum radiation shielding. The trip time can be however long it needs to be to be energetically feasible.

    If the ship fails in flight, nobody died. If the destination world is not promising, the embryos need not be thawed, no harm done. If 99% of the embryos are not viable on arrival, no problem, you still have the option of creating ten thousand baby humans. Whether this actually constitutes human starflight is a matter of opinion. But the point is, we have been cryo storing human embryos since the 1970s. One need not postulate fast interstellar travel, cryo sleep of adult humans or generation ships to plant human colonies amongst the stars.

  • Adam August 15, 2015, 4:14

    Hi Astronist,

    Robert Freeland was expanding on work by Brian Halyard, but in turn that’s based on multiple criticisms of the ICF fuel choice false dichotomy between D/He3 and D/D. If we could use the “dry fuel” reaction – lithium-6 deuteride – and keep the neutrons confined in the fusion plasma, then things would be much easier.

    Adam

  • ole burde August 15, 2015, 4:51

    If we accept that SF should be mostly based on extrapolations from existing knowledge , trends and history in general , then it becomes relevant to examine to what extend this Rule is being observed i specific cases , and alternatively if there are certain areas of future-history in which ”The Rule is ” broomed under the carpet’ .
    When Robinson , and many others, choose a scenario where a Gigantic Manned Spaceship are build mostly WITHOUT concern for the economics of the project , can this in any way be connected to The Rule ? … We live in an age where the planet as a whole i having a certain growth in its economy , but on the other hand the fraction of this economy which is invested in manned spaceflight i shrinking much faster for reasons of political nature . This could change of course , but we are still waiting for a good Rule-based SF -explanation why this should happen …
    Compare this to another area of Rule-application , the human factor : an impossible problem or a challenging solution ? …In reality , individual humans have consistently outperformed the challenges they were confronted with in space and in other dangerous environments …in the early 90’ties I can remember a great lot of ”experts” telling us that humans would never be capable of building the ISS because it was ”too far outside the limits of human performance envelope” …and now we have Robinson &friends telling us that humans will never be capable of facing another kind of challenge.. ( why didn’t they just find a way to KILL the damned ‘prions’ ? ) …. On the other hand the Human Factor is also blamed for detail-problems of technology where an individual person made a mistake or a wrong decison , such as led to the catastrofic failure of two Spaceshuttles .
    My point is that these detail-problems can be fixed permanently by the natural Evolution of technology , but only if we can resist the urge to blame somebody , to seek revenge whenever something goes wrong . If you look for the real downside to the Human Factor , that’s where to look , because this natural urge to seek revenge in the pursuit of justice , can be USED to destroy almost anything including spaceshuttles .
    All in all , Robinson chose to follow The Rule in a very selective manner . The very real problems of economy is declared nonexistent , while the very real solutions embedded in Human Nature is declared equaly nonexistent .
    When people apply rules in a selective manner , beyond a certain point ,it implies that they are trying to change The Rule to reach some other objective which does not belong inside the Rules …Such as writing an Avatar-compatible book that would fit Hollywoods post-modern anti-imperialistic politics .
    Politics can poison almost anything , it is an invasive species .

  • Phil August 15, 2015, 5:48

    A thought-provoking analysis by some profound thinkers, as usual! Aurora is a fascinating read but like 2312, the science is deeply flawed. My only quibble is that abiotc oxygen atmospheres are not, to my mind, completely impossible. What do the authors think about the “Mirage Earth” model by Rodrigo Luger and Rory Barnes [Rodrigo Luger, Rory Barnes. Extreme Water Loss and Abiotic O2 Buildup On Planets Throughout the Habitable Zones of M Dwarfs arXiv:1411.7412v2 (astro-ph.EP)]?

    They proposed that the long pre-main sequence phase for low-mass M dwarves* means that close-orbiting terrestrial worlds may remain in a runaway greenhouse state for tens of millions of years in which photolysis of stratospheric water vapour would lead to the rapid dessication of the planet and, as a consequence of preferential hydrogen escape, substantial oxygen buildup – the paper posits 5 bars/megayear (!) oxygen accumulation for an Earth-mass planet (although admittedly, these worlds would also have a super-Venusian** CO2 load which might make one question the habitability). Even with really efficient oxygen sinks significant and highly detectable levels of atmospheric oxygen would remain for quite a while. Of course, Tau Ceti is a G8 dwarf, and older than Sol to boot, so this scenario doesn’t apply…although for YZ Ceti, it might be a possibility?

    Phil
    *Okay, okay…dwarfs. My bad, I like Tolkien.
    **No grief people, please…I’m not even sure how to pronounce ‘supercytherean’

  • J. Jason Wentworth August 15, 2015, 7:19

    It would be interesting to see critiques–on scientific and sociological bases–comparing Kim Stanley Robinson’s “Aurora” and John W. MacVey’s “Journey to Alpha Centauri” (which was later reprinted, with additional technical information, as “How We Will Reach the Stars”).

    MacVey had no illusions that his 1/50 c starships ‘Columbus’ and ‘Drake’, even though they would depart Earth on their 215-year, 8-generation journeys in the year A.D. 2500 (when technology will–if we don’t cause another dark age before then–be greatly advanced over today’s), would *not* stretch the capabilities of even that era to their limits. He also freely conceded that the sociological and moral precepts of the starships’ crews would have to differ significantly (particularly with regard to the onboard government and justice system) from what we in the West would willingly tolerate.

    Still, Robinson’s novel, even though it falls short in the scientific accuracy department, does offer a valid cauionary tale where the preparedness for the unknowns of a one-way, sub-relativistic interstellar voyage are concerned. It would seem reasonable that before any such colonization vessels depart for their distant destinations in real life, their target exoplanet(s) will have been scrutinized using vastly improved Earth- and/or satellite-based instruments, to make sure (or at least make it a very probable possibility) that the planet(s) could indeed support Earthly life forms. (Interestingly, “Journey to Alpha Centauri”/”How We Will Reach the Stars” also posits uncertainty–when the two ships leave Earth–as to whether habitable planets exist around either of its target stars, Alpha Centauri A and Alpha Centauri B.)

  • Michael Spencer August 15, 2015, 8:08

    KSR is on my must-read list, too, ever since the stunning “Mars” trilogy, along with just a few others, including the Benfords, Vinge, Reynolds, Bear, Niven, Banks (alas, no longer), McDevitt, and Hamilton.

    But his science just barely passes the smell test. I know that. I know that when he tells me about wilderness biomes, or when he posits a well-settled solar system (2312), he’s making general statements. KSR is not interested in the science. When he frames a story that hangs so heavily on science the story simply fails. Witness the last part of “Aurora”, which fails not so much on the story arc but on too much verifiable detail. Yes, SF readers hunger for hard science. And yes, the hard science must be correct. That’s why “Aurora” fails. Can’t believe the science.

    But it’s still an vital contribution, worth owning, reading, and discussing. KSR continues bringing important topics to the common discussion.

    Writing SF presents the author with a conundrum possessed by no other genre: every nit-picking, arm-chair science nut with a calculator can check your work!

  • J. Jason Wentworth August 15, 2015, 8:20

    The electromagnetic “scissors” launch method used for the starship in Kim Stanley Robinson’s novel “Aurora” (this launch method is described and analyzed in Greg Matloff’s and Eugene Mallove’s “The Starflight Handbook: A Pioneer’s Guide to Interstellar Travel”) would be unwieldy for such a huge, massive vessel (the launcher would have to be ridiculously long, and strong), BUT…such a scissors launcher of reasonable size–which we might be able to build even today–might be perfect for slinging off small (perhaps up to a ton or so; more advanced, stronger tether-scissors could launch more mass at once) starprobes at 0.1 c, or maybe even faster (because the moving point of intersection between the “blades” could move so fast. I can even envision a possible scissors launcher that might be practical using existing space tether technology; it could be like this:

    Two rotating “bolo”-type space tethers could be so arranged that their centers of rotation (as the two tethers rotate in opposite directions to keep them taut) would be coupled, perhaps using magnetic bearings in order to avoid any mechanical friction and wear. The two tethers could be spun up for launching probes be means of either electric thrusters at their tips or an electric motor at their common “hub.” (Such a motor need not have a casing; electromagnets on each tether, situated close to the hub, could do this, much like the motor of a Hunter ceiling fan [it has different numbers of permanent magnets and electromagnets on the armature and surrounding it; because they never line up exactly, because of their different numbers–one odd, one even–there is always a “push-pull” effect on the armature, making it spin using very little electricity].) Electromagnets–or perhaps even permanent magnets, for tiny probes–would be fastened along the two counter-rotating tethers. Now:

    After the tethers were spun up to the desired rotational speed, a probe (with electromagnets or permanent magnets on it, to repel the bolo “blades'” magnets) would be placed at the point where the blades will intersect when they “come around again” (this point being chosen so that the “flicked away” probe will shoot away in the desired direction to reach the chosen target star or planet (this system could be used for interplanetary as well as interstellar missions). When the blades close in on the probe’s location, it is “flicked” along at ever-increasing velocity, by the rapidly-advancing point of intersection of the two blades. If desired, numerous probes could be launched in quick succession using the scissors (they might require an additional “spin-up impulse” after each probe launch because of the energy they would “lose” to each probe, but the mass ratio of the scissors to a probe would be so large that it shouldn’t require much, or take very long to replenish it).

  • Joseph Morris August 15, 2015, 8:20

    @ole burde and Astronist: Extrapolating from existing trends can only lead you to a limited view of the future. Human history has been driven by the force of creative destruction, with the introduction of disruptive technologies, beginning with tools, then hunting, then fire, then language, then agriculture, etc., all the way up through the Industrial, Transportation, and Information Revolutions. So extrapolating existing trends only puts you at the trailing edge of our future. There’s nothing wrong with that except it seems to me speculative fiction writers should be looking for the next disruptive discovery and the ones after that. Then the fiction becomes truly speculative. For me, I believe we will find a way around the lightspeed limit. It will probably take something really disruptive to accomplish that. And even if the technology is not disruptive, the impact on humanity civilization will certainly be.

  • Rob Henry August 15, 2015, 8:30

    I haven’t read the book, but from this review several things stand out as puzzling me.

    1) on arrival with our 76% fuel, it would make no sense other than to pack all easily replaced materials, such as soil and water around our first deceleration fuel pellets. If this was actually done, then the simple use of the rocket equation would make our task look harder than it actually was.

    2) On the return journey the craft might be lighter still as we can arrive with nothing left, and don’t have to worry about our final population being too small to avoid genetic bottlenecks.

    3) The wilderness areas being too small assumes that the environment is not engineered for higher efficiency than currently seen on terra firma. Land environments typically currently see a 100-1000 fold reduction in biomass per step up the food chain. In a few hundred years, I bet we have the knowledge base to micromanage these to reflect marine efficiencies where the factor is only ten. I am near certain we can have our wolves and bears if we really want to.

  • Frank Smith August 15, 2015, 8:59

    Like several of the commentators, I find it implausible that a colonization attempt would be made without an extensive robotic scouting and landing precursor mission.

    My other thought would be each human carries more bacteria than human cells. Wouldn’t it be just as likely that our bacterial and viral ride-a-longs, with a billion years of evolutionary wars behind them, be a real threat to simple alien life?

  • Jer August 15, 2015, 10:27

    As much as I believe that there will never be an epic multi-generational colonization ship that would require a substantial portion of a solar system’s resources to send a small group on a Hail Mary expedition, I do believe that there will be ongoing experiments, extended pleasure/research trips, and extra-solar ‘one-way’ trips with small groups in their self-sustaining life ‘crafts’ slowly extending the reach of humanity. Why?

    – I can’t believe that a wealthy and technologically advanced society would come across a ‘situation so dire’/’destination so promising’ that they would/could spend/invest such a substantial fraction of their civilization’s resources on a few rather than adapting/comforting/ inspiring the vast majority – despite the possible impending doom/discovery. I am not convinced our species is noble/farseeing enough to send out a small ‘last hope’/’techno discovery’ group to continue/promote humanity in such a way.

    – I am actually quite astounded that there is a group that sees terraforming as the most logical/inevitable next step in getting us to start inhabiting other star systems, irrespective of our technological level. It seems similar to the notion of an intellectually/emotionally/socially-well-adjusted individual or small group wanting to suddenly build an off-the-grid cabin in the middle of nowhere with all the isolation and work involved, forever – despite a great variety of modern, dense or sparse built-up areas (assuming no over-population or widespread poverty).

    I see it more likely that the infinitely complex, comfortable, and sustaining space ‘motorhomes’ /hollowed asteroid-resorts (likely way more life affirming and rich on experience as any type of city life) start to sprawl outward from a critical population density (perhaps inner solar system size), slowly expanding over centuries to within a decade’s distance from the next solar system/rogue star/ interstellar entity with a few making slight detours to swing by. Extra-solar systems are more likely ‘soon’ engulfed by the swarms of individual/ family-ish/ community space-faring groups’ sprawl – multi-year side trips without significant society-wide contribution. What would be society’s level of achievement have to be that groups of 1 – 50, making up a sizeable percentage of the population (>20%), could afford to have a custom space-faring life vehicle? If we were to hollow out every asteroid/convert significant solar system mass to a fleet of vehicles, how many could be made?

    But how to make this a dramatic novel? Well, 2312 did well with the intrigue and drama on a significantly built up civilization.

  • Brett Bellmore August 15, 2015, 11:33

    That the slingshot maneuver wasn’t going to work was so obvious on it’s face to anybody who has the slightest grasp of orbital dynamics, I have to conclude that Robinson had just written himself into a corner. He had a star ship that needed help to launch, and needed it to come back on it’s own. Something had to break, and it wasn’t going to be his plot. Laws of physics had to go, instead.

    He couldn’t solve the problem with a technological advance, because he wanted interstellar colonization to be impossible, and any relevant advance would make it easier.

    The big plot hole, of course, is the idea that a generation ship crew, who have grown up knowing nothing but life in an artificial habitat, are going to fixate on colonizing a planet. Instead of just building more and bigger habitats. But, again, he wanted interstellar colonization to be impossible, and this would have undercut that.

    On the question of how Earth life would interact with an extraterrestrial biology, I guess that depends. We could be biologically oblivious to each other. We could find each other toxic. We could find each other yummy. I expect it would be a combination of the latter two, unless the other biology was radically different from our’s. Silicon based, or something. All it would take for us to find them toxic would be different handedness. But the root layer of biology, the bacteria, lichen, and so forth? They’d probably chow down anyway. On both sides.

  • James Stilwell August 15, 2015, 12:36

    Joy has taken all the fun out of the Aurora project…
    A million embryos frozen for a millennial trip…
    The ship is maintained by the Kubrick artilects…
    Then the baby humans are raised by the same artilects…
    And Earth wouldn’t know a thing about the outcome for a 1000 years…
    Our hello would take a 1000 years to get there…
    Their hello would take another 1000 years to get here…
    Is this the future of human civilization?

  • ole burde August 15, 2015, 15:25

    Brett Bellmore : As you said , Robinson wanted interstellar colonisation to be impossible . Exactly , but why would he choose such a pessimistic view of the basis for his own profession as an SF writer ? Why write SF at all ,if you dont believe in its core values ? If the idea was to warn us about real dangers , the plot should have presented us with the possibility for a positive outcome IF we listened to the warning . …otherwise it is not a warning but more like value-judgement …like in ‘This Is Wrong” …..
    Why would anyboddy become a sucsesful professional footballplayer , and then go on to seek the destruction of the game by joining the chorus whining about the malechauvinistic violent nature of the game ?

  • Rob Henry August 15, 2015, 17:45

    To continue the list of things that puzzle me

    4) humans should be able to easily withstand 10g simply by being being floated in water.

    5) Why are so many adamant that nonbiological dense O2 is unlikely when I have never seen any explanation for the loss of Cytherean photolytically produced O2 whereby transport of ferrous materials to its surface (which are significantly denser than ferric materials) could come within an order of magnitude of rusting the hundred tons/m^2 or so of O2 that would be necessary. To me, the bulk of the excess must have been accelerated off Venus as O+, a non-thermal loss type that won’t necessarily work as efficiently on other worlds – it certainly hasn’t/isn’t doing so from Earth!

    Also @Ron Smith, I agree. The macromolecules of our immune systems show clear signs of a greatly accelerated rate of evolution compared to any other type I know of, and being helped by genetic transfer, presumably from previous infections. No one knows the rate at which bacteria and viruses enter our body tissue, especially our blood stream, but it could be billions per day. Our immune system is so powerful, rapid acting, and well honed to Earth’s pathogens that not a single one of these can be grown from the bloodstream of a healthy person – but if there were one exception to it, say every trillion infections or so – then we would be doomed. Even if the exception couldn’t digest our tissue it would grow slowly inside like a cancer feeding on simple molecules like acetate and oxygen.

  • Adam August 15, 2015, 19:24

    Having published one paper on Embryo Space Colonization, maybe my opinion carries some weight. I personally think the better approach is to “body-print” adult humans directly from sufficiently high resolution scans – think the ‘resurrection’ of Leeloo from “The Fifth Element” if you want a visual impression of what I mean. As our ability with neuroprostheses and organ-building improves over the next ~50-100 years, we’ll reach the point where we can download a full brain-scan into an advanced whole-brain neuroprosthesis in a printed body. Whether such a person is considered human, cyborg, android or some other arbitrary category is really more about philosophical hair-splitting over styles of embodiment.

    What does that mean for interstellar travel? Smaller starships are much easier to launch, requiring much less in-space infrastructure – if any. Clever carbon solar-sails could, in theory, enable speeds of 0.01-0.06 c without any augmentation by massive laser arrays.

  • Wojciech J August 15, 2015, 20:24

    One thing that continues to bug me in Aurora(forgive the pun), is the fact that the first planet humans decided to colonize had life on it, and was pretty close to Earth.
    This would mean that statistically life is pretty widespread in the universe, and should be detectable by possible telescopes a civilization like the one described by Robinson in Sol System(numerous asteroid colonies, colonized Saturn moons) would have easy access to.
    Hence by the time the Ship would arrive at Aurora, humanity would be aware of dozens, if not hundreds of living worlds nearby.
    Existence of such life would make interstellar travel a issue not of colonization but of first contact of unparalleled proportions in human knowledge of the universe and a necessity to any society valuing knowledge and science.
    This issue is completely avoided in Robinson’s book(as is the fact that seemingly advanced human civilization has forgotten about the fact that most of Earth’s biosphere is in its litosphere).

  • Ron S August 15, 2015, 21:48

    While not quite on topic, here is an interesting mapping of SF books, by hypothetical events and year of publication and year of the event, whether it is positive or negative, and field of impact. Interesting, if you like that sort of thing. Obviously not all of these authors’ future visions are compatible.

    http://www.ritholtz.com/blog/wp-content/uploads/2015/08/future.jpg

  • Coacervate August 15, 2015, 23:08

    @James Stilwell and Joy

    You can either accept the horrid scale of the universe as a cruel joke or just another hurtle for overcome. Joy’s embryonic seeds are a reminder, to me at least, that all we need to send is information and technology to transcribe/translate into beings. Of course these beings should carry pre-encoded encyclopeadic knowlege, just as my pet kitten does. I never trained her to wake me up by rattling the blinds…it was just there.

    There seems to be a lot of talent here. Would it be fun/useful for us to work together? What would our book tell us about ourselves and what we need to become to go to space for real. Lets get Andy (the Martian) onboard too!

  • Rob Henry August 15, 2015, 23:22

    Another thing to add
    6) Several here seem confused by what ‘prion-like’ means, but to me there seems an obvious answer. That is how I would describe a system where genetic information is held in a 3D or 2D lattice rather than a linear molecule, and that information is stabilised via conformational changes on its macromolecule constituents. It is only remotely possible that this could passed on to human brain proteins, and more likely these arrays would catalyse their base molecule production when exposed to precursor chemicals. These would result in the slow buildup of prion like plaques within their host environment.

  • Charlie August 15, 2015, 23:45

    Certainly, many, many interesting comments on this page here. I have not read the book I just heard about it, but I think that I’m interested enough that I actually may go out and purchase the thing at full price just to get a good read on it ! I haven’t read all your comments, but some of them like Joy’s seems to merit at least first crack at what I had to say.

    It would seem to me that the idea of raising embryos is a OK problem and solution to interstellar flight, BUT there is the problem as to what degree you are able to go ahead and control the situation so that the arriving embryos can be race properly and to people. For example, if people were raised by machines from birth that might be OK if you had a machine (à la Terminator, but nice. Of course) that could completely act like a human being and would fool the person throughout his/her life. I mean after all, what difference does it make if the person who is raised by the machine ever find out whether or not the person that raised him/her was in fact a real human being? What possible difference does it make with regards to the development of the person irrespective of what it was or who would was it raised it?

    I sincerely believe that there are people who would go on interstellar mission tomorrow if it was offered, and there was a reasonable chance of survival. There are people out there who are so self sustained internally that they probably can endure things that most people would rather not face and poor would probably be ideal candidates for missions like this. You know the type, super dedicated, intensely interested, and risk-taking to the Max ! So I don’t think that psychological barriers would necessarily be a impediment to interstellar travel. You would just need to find somebody be tough enough to want to undergo the isolation and limited lack of varying interaction with too many people. My essay you could get tired of the same faces, but some people actually don’t. I could say a lot more, but I’ll relinquish the floor.

  • Steve Bowers August 16, 2015, 5:36

    An abiotic oxygen atmosphere would be possible on a waterworld, because the water would provide a barrier to prevent the oxygen ‘rusting out’ (to use Baxter’s phrase). But presumably the planet would be mapped beforehand to determine if there were any landmasses.
    Mapping a planet at interstellar distances would be challenging, but surely not as challenging as getting 74 million tonnes up to 0.1c.

  • Steve Bowers August 16, 2015, 5:43

    By the end of this book the human race has developed cryosleep, a much more sensible way of colonising the universe. I would expect a second wave of colony ships to be launched, much smaller and lighter, and possibly even faster, to go and annexe those innumerable worlds and asteroids out here that do not have dangerous pathogens.

  • Brett Bellmore August 16, 2015, 9:54

    “Why write SF at all ,if you don’t believe in its core values ?”

    Because you want to challenge/change them? I suppose it’s possible that you missed one of the major cultural evolution factors in the 20/21st century, but there are a lot of people out there who, when they discover a subculture which seriously disagrees with their own values, will join it *with the intention of dragging it into such agreement.* Whether or not the people originally making up that subculture want their values changed.

    You find almost all of those people on the “left”.

    That’s how the ‘literary’ culture has reacted to SF. And they’ve made great progress in subverting SF’s technophilic, optimistic, essentially extropian values, replacing them with their own technophobic, pessimistic, and ultimately nihilist values.

  • ole burde August 16, 2015, 12:48

    It seems strange to me that many of the people writing here would prefer to populate our future starships with robots , body printed adult humans , cyborgs , humans brains ”downloaded” into computers , or in short anything BUT more-or-less natural humans …
    It becomes even stranger if you consider that the REASON for rejecting a slightly modified human crew , often are based on the very real need to make slight modifications in genetics (radiation resistance) , psycology ( resitance to depression) and behavior patterns ( enhanced family-building ) ….
    Why would anybody prefer to give up much , if not most of what it means to be human , in order to escape the need for the small but unavoidable changes that evolution will demand of our species to make us fit for a generationship ?
    Is it because the smaller , more realistic changes are ‘closer to home’ and thereby violates existing cultural bias (‘human rights’) , while the more far-reaching transformations are (so far! ) too theoretical to be included in the ‘prohibition manual’ ?

  • Wojciech J August 16, 2015, 13:13

    Steve Bowers-at the end of book, Sol System is sending new colony ships to other systems, we don’t have learn anything about detection of life signatures on other planets, which the civilization described by Robinson should be able to do with relative ease.
    The argument against this effort is simply stating that it is wrong and a woman hitting a man who proposes that humanity will endure eventually. Robinson also smuggles a sentence about those willing to colonize other planets as “a group of white men” which is allusion to certain ideological views his background has(and might not be obvious to everyone).
    But really this book is a polemic, not a realistic SF.
    With the technology of the colonists(and remember they were sent back hundreds years ago) a whole planet could have been terraformed, a ship sent back to Sol System and whole interplanetary infrastructure build. So a single ship carried technology potent enough to change the face of whole solar system.
    Yet when it returns to Sol System, everything is mostly as it was before. And yet,if they had such technology, it would allow them to make our home system a teeming, rich place full of mega scale habitats, wonders of engineering and so on.

    Lastly I note that the above article lacked one thing that Robinson based his whole book on:the belief in mystical power of Earth over human beings.
    In the book we learn that if humans do not come to Earth in their lifetime they will slowly but surely die quicker and suffer from disease. This is never explained in satisfactory way, has no real basis in science, and seems to be new version of a mystical belief in supernatural element of the planet, somewhat akin to Gaia.

  • Alex Tolley August 16, 2015, 14:28

    @adam

    Having published one paper on Embryo Space Colonization, maybe my opinion carries some weight. I personally think the better approach is to “body-print” adult humans directly from sufficiently high resolution scans – think the ‘resurrection’ of Leeloo from “The Fifth Element”

    Embryo colonization seems less fanciful that whole body printing. I would be very surprised if you could store a mind and then upload it into printed brain unless the resolution is at the sub-neuron level.

    But why print a biological body at all – isn’t that biology chauvinism? The mission failed because of biology. Why not print artificial bodies and upload (or not) [human] minds into them? Machines will be well advanced by then, and the lack of biology ensures that all suitable worlds can be occupied without regard to biology issues. Then the starship payload need be no more than universal replicators (printers) and resource extractors. Artificial bodies would make many interstellar travel issues disappear, allowing various approaches that do not fail due to human biological needs.

    In addition, once arrived, the ship could become a receiver for minds to be uploaded into new factory built bodies, the rate of upload depending on the transmission bandwidth from the solar system, or other inhabited stars.

    This seems to me to be a simpler, more technically feasible approach than printing the complexity of a human body which is adapted to Earth conditions.

  • Alex Tolley August 16, 2015, 15:38

    @Ole Burde

    It seems strange to me that many of the people writing here would prefer to populate our future starships with robots , body printed adult humans , cyborgs , humans brains ”downloaded” into computers , or in short anything BUT more-or-less natural humans …

    Modifying humans won’t buy enough improvement or changes to avoid the obvious problems. It is like arguing that fish should modify themselves to colonize the land, e.g. small modifications to avoid desiccation, rather than evolve into true land dwellers.

    Machine bodies will develop very quickly offering a more robust form to live in space and travel the stars. Whether human minds will occupy those bodies or not is up for grabs. But clearly, low cost, small ships carrying the offspring of biological humans will likely travel to the stars far in advance of any humans unless there is breakthrough physics in the next century. This seems a natural outgrowth of our existing robotic missions, offering a path to stellar exploration with “reasonable” budgets. Economics will trump desires, much as the robotic Cassini mission to Saturn happened, whilst the fictional manned Discovery from 2001: A Space Odyssey wasn’t even close to becoming viable.

  • Peter Popov August 16, 2015, 17:02

    The argument why human star travelling is close to impossible is plainly manifested in this fine analysis of “Aurora” . The jet power of the fusion engine and the tens of millions of tons of fusion fuel needed simply means such endeavors are centuries away. I can’t remember the article, but it was a rough energy estimate of a generation ship and a fast crewed probe. Both estimates, assuming current rate of GDP increase put much less ambitious schemes about two centuries away. The estimate here is of the same order. We simply don’t know what society will look like and care about in 2200. So, I think we need to establish an industrialized civilization that spans the solar system, prior to worrying about human star travel. And hope the Singularity does not hit us in the meantime. And if the solar system gets colonized, and if we still care, and if we are still biological, then it will happen in some way which can hardly be figured today.

  • Coacervate August 16, 2015, 18:18

    Is it possible (likely?) that we are developing the beginnings of the answer to the Fermi paradox here in this thread?

    By the time we advance science/technologies sufficient to achieve interstellar travel, our goals will also have changed. My goal is knowledge. What if flying hardware and wetware to stars turns out to be the least efficient way of achieving the goal?

    What is our/your goal?

  • Brett Bellmore August 16, 2015, 21:45

    “Both estimates, assuming current rate of GDP increase put much less ambitious schemes about two centuries away.”

    But there’s no particular reason to expect the current very anemic GDP increase (In the US actually negative, if you use 1980 measures of inflation.) to continue for two centuries. We’re not, in the opinion of this tooling engineer, all that far from being able to build a Von Neumann replicator. Once we’ve got that the economy is going to completely change, undergo a classic S curve transition to a much, much higher GDP.

  • Joseph Morris August 16, 2015, 22:54

    So much pessimism here. And so many limits on imagination. Everyone here keeps talking off of extensions of today’s technology. Fusion drive is certainly not the ultimate sublight drive. Antimatter drives have higher inherent ISPs. And don’t tell me they’re impossible. They’re only impossible with today’s tech.

    And not once have I seen FTL mentioned here as a means of reaching the stars. No matter that NASA is funding Sonny White’s work. Yes, I know most physicists believe his work is nonsense. But if you don’t try, then you automatically fail by default. If his stuff doesn’t work, then so be it, but it may stimulate someone lese.

  • Eniac August 17, 2015, 0:30

    Astronist:

    Worth noting that helium-3 is no longer needed for a fusion pulse engine, making fuel acquisition very much easier. The breakthrough was made by Robert M. Freeland, a member of the Icarus team:
    http://www.jbis.org.uk/paper.php?p=2013.66.290

    It is indeed worth noting. It would also have been worth an extra sentence naming the mystery fuel in question. The link you quote refuses to do so unless 5 pounds are paid, which leaves me feeling like Tantalus, or worse, like a gullible target of advertising. Perhaps you would care to complete your comment with some actual information?

  • Eniac August 17, 2015, 0:54

    This article (and the book it is about) is a great exercise in looking at the feasibility of fast generation ships, and not surprisingly has the concept come up short in the realism department. Here are some concerns of mine:

    1) Generation ships were, I thought, primarily conceived as an answer to the difficulty of reaching high speeds, so to have one that reaches 0.1 c seems absurd to begin with.

    2) Both the novel and the critique are needlessly concerned about genetic diversity: It is exceedingly easy to carry any amount of diversity on board in the form of frozen sperm, eggs, or embryos. With cryosleep technology, the most economic mission profile that avoids unknowns such as robotic wombs or mind uploading is a small group of women accompanied by a well-equipped sperm bank. Include a seed bank and some animals (females+sperm) for good measure.

    3) Having some biology training, I consider deadly alien organisms extremely unlikely, especially “prion-like” ones. Prions, worse even than viruses, depend on the specific biology of their hosts. In particular, they could never be the only lifeform in an ecosystem, nor would they be able to do their trick in an organism with incompatible biology, as we should assume aliens to be. The only way an organism could be infectious to Earth life is was fully biologically autonomous, a bacterium at minimum. As someone else has said, such organisms could feed on the inorganic goodies found within our bodies. I am pretty sure, though, that such organisms would be easy prey for our immune system. Earthly pathogens, without exception, have evolved complex adaptations to evade earthly immune responses, aliens would be ill-equipped in comparison. IN particular, I am bothered by the suggestion that their natural ecosystem does not include hosts at all. There is no such thing as an accidental pathogen: Free-living organisms are not pathogenic, and pathogens generally cannot thrive without hosts.

  • ole burde August 17, 2015, 3:50

    Alex Tolley : ”Modifying humans won’t buy enough improvement or changes to avoid the obvious problems. It is like arguing that fish should modify themselves to colonize the land, e.g. small modifications to avoid desiccation, rather than evolve into true land dwellers.”
    Actually that is EXACTLY what fish did , as the FIRST stage in their further evolution as landdvellers . Just as we humans have 95 % of our DNA in common with the other primates , so the first sucesful landdvellers (an amfibous species called Ichstyustega , a lung-fish capable of running on its evolved fins ) also had probably much more than 95% of their DNA in common with their fish-ancestors .
    Evolution never throw away a good design , and we humans are a very sucsesfull design indeed . What usually happens in evolutionary change , is that new capabilities are added to to the ancestor-design by very very small additions of new DNA , which manages to change the funktional output of large chunks of existing DNA-program code .
    The most ”obvious problems” facing humans in the cheapest-possible generationship are radiation-resistance , psycology and behaviour If these can be solved by genetic modification together with an advanced selectionprocess , the constraints of design will change dramaticly to a point where a low -mas ship becomes possible … much less than one % of ‘Aurora’
    Evolution is the most complicated information-processing system in the known universe . We can learn from it how to change ourselves just enough to fit the jobdescription in a generationship , and other space habitats . A smal group of such modified humans can bring with them a large cryo-bank of frozen embryoes , some of which can be natural humans and some not .

  • Wojciech J August 17, 2015, 4:40

    Coacervate-yes that is something that comes up often in discussions.Once you have technology allowing you for interstellar travel and colonization, you no longer have to.An interstellar travel would be for exploration and knowledge, not for colonization.Terraforming planets might happen, but as a vanity project, not neccesity.