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Into the Orion Arm

Although we have little observational data to go on, the existence of the Oort Cloud simply makes sense. We see new comets coming into the inner system that are breaking up as they approach the Sun, obviously not candidates for long survival. There has to be a source containing billions of comets to account for those we do see. The Kuiper Belt is stuffed with what we can call ‘iceteroids,’ all moving more or less along the plane of the ecliptic until, well beyond the Kuiper Belt itself at about 10,000 AU, the disk shaped belt of material spreads into the spherical Oort Cloud. A nudge from a rogue planet or passing star is enough to produce the velocity change to send a comet inward.

We’ve been looking this week at possible human uses for cometary objects, including the fact that they’re rich in water but also nitrogen and carbon wrapped up in interesting organic compounds. From the standpoint of resource extraction, we also find interesting elements like silicon, sulfur, nickel, chromium, magnesium and iron available in at least small amounts. Tiny worlds a few kilometers in diameter, rich in resources and loaded with water, existing by the trillions. Surely a space-oriented civilization of the future will find a way to exploit them.

Protecting the Inner System

But it’s likely that long before we start talking about a human presence in the Oort Cloud, we’ll be engaged in robotic studies driven by the sheer necessity of protection. Recent near-miss asteroid events have raised public consciousness about near-Earth objects that could pose a threat to our planet. Comets can wreak havoc as well, with the difference that near-Earth objects are gradually becoming tracked and catalogued. With an NEO, we can plot trajectories that give us time to consider how to move an object that might not be projected to hit for decades.

Comets are different. We can’t predict when a new one is going to appear. Robert Zubrin points out that when the huge comet Hale-Bopp was detected in 1995, it was well beyond the orbit of Saturn, but moving at a speed sufficient to cross the Earth’s orbit a mere two years later. An object like this, massive and moving at high velocity, would have been all but impossible to deflect if we had learned it was headed for us. Deflecting a fast-moving comet, as opposed to a nearby asteroid, means getting to it when it is still deep in the outer system. Planetary protection will all but ensure we’ll have a presence in the Kuiper Belt and Oort Cloud one day.

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Image: Comet Shoemaker-Levy 9, torn into pieces as a result of a close approach to Jupiter in July 1992, before its later impact with that planet. The major cometary fragments range in size from one to a few kilometers. Credit: JPL.

Whether such a presence is largely robotic or not, it will spur the technologies we’ll eventually use for starflight. And not just the technologies — as we’ve seen, human settlements on O’Neill cylinders exploiting cometary resources would be case studies in isolation and social experimentation. Starships designed for fast crossings (multiple decades) or gradual voyaging (thousands of years) will have to incorporate what we’ve learned about people working together to keep communities in coherence when far from home. The Oort Cloud has a role to play.

The Fork in Interstellar Evolution

It’s possible that we may see two kinds of starflight in the next thousand years. I turn again to Richard Terra, whose article “Islands in the Sky” ran in the June, 1991 issue of Analog (it’s also reprinted in a 1996 hardcover from Wiley with the same name, a volume of essays edited by Stanley Schmidt and Robert Zubrin). Terra’s notion is that the wealthy inner system cultures will eventually develop what Ben Finney calls ‘fastships,’ spacecraft capable of moving at a substantial percentage of the speed of light. These will always be the first to cross the interstellar divide, but a slower wave of migration will follow.

The point is this: A small but growing human population in the Oort Cloud will master cometary motion, taking advantage of the fact that at 10,000 AU, the speed needed to orbit the Sun is just 300 meters per second. Compare this to the Earth’s 30,000 meters per second and it should be obvious that it takes only a small change in velocity to alter a comet’s orbit. We’ll have learned this in theory if not in practice because it factors into the engineering needed to divert a potentially dangerous comet from striking our planet decades in the future. Learn how to bump comets to change their orbits and you start thinking about what else you might do with such an object.

Interstellar space must be littered with comets that have been ejected from our system through the 4.6 billion years of its existence. Some estimates run as high as 1000 Earth masses in cometary material, so the resource base between us and the nearby stars should be plentiful. If Oort Cloud comets are separated by about 20 AU, these interstellar comets may be hundreds of thousands of AU from each other. The Oort Cloud should be in perpetual flux as some interstellar comets enter and move through it while other comets are pushed back out.

Let me quote Terra on this:

Some of these interlopers are bound to be found within Sol’s own Oort Cloud, working their way free of the Sun’s grip, at perhaps one in every several thousand. Relative velocities between Solar and interstellar comets will be low, and it will be tempting for Oort Cloud residents to hitch a ride outward — perhaps farther out into the permanent Cloud, perhaps out into interstellar space. Drifting outward at about 10 km/s or about 2 AU per year, they will make slow progress indeed. In 50,000 years they will be halfway to the nearest stars. But by then they will be wholly adapted to life in interstellar space and will perhaps not be too concerned with visiting other star systems.

So maybe there’s no one way to depict interstellar expansion. Fastships propelled perhaps by fusion or beaming technologies or antimatter may eventually cut the journey to decades. Over the millennia, a species fully adapted to living in space — and surely evolving in ways we’ll be unable to predict — will populate the outer system and move in slow generation ships between stars that may no longer be so much a destination as a curiosity. Perhaps some Oort Cloud communities will, as Terra suspects, alter a comet’s orbit so as to make a gravity assist maneuver around the Sun, all the while shielding the nucleus with solar power collectors.

Gravity assist might pick the speed up to 150 kilometers per second, which works out to a bit over 8000 years to Alpha Centauri. Whether such a traveling colony world would actually put colonists on a planet around the destination star is conjectural. Perhaps more likely is the idea that they would study the new solar system and then set course for another. The human species will be in the process of evolutionary forking, and after a few such journeys between the stars, the meeting between the cometary travelers and their fastship brethren would be an interesting one to see. What would these two different branches of humanity still share?

I don’t know the answer to that question, but it gets at the meaning of what it is to be human. Our future Oort Cloud dwellers will have not only an isolated gene pool but the tools of genetic engineering at their disposal, which could make biochemical and even structural changes possible at a faster clip than straightforward natural selection. If our species survives its technological adolescence — by no means a sure thing, as the Drake Equation reminds us — then humans around other stars are going to take a wide variety of forms adapted to their environments, a flowering speciation that could spread humanity out into the Orion Arm.

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Comments on this entry are closed.

  • Rob Flores March 28, 2013, 11:16

    If we are talking about a 16-20km inward bound comet, admitely the
    options are few. Because of the extreme parabolic path, the Delta-vee
    a solution that requires orbiting or landing on, or placing some pusher engine on it is out of the question. So that leaves interception with nukes.

    You would have to in short time frame, comandeer all heavy launch vehicles coming into line within 2 -3 months. Create a nuclear carrier
    vechicle with guidance & power to get it to the proximity of the comet.
    Detonate Adjacently. you can probably send 10 -12 2 megatons
    devices. MIRV style on 2-3 carriers.

    Are we admiting that we cannot deflect such a body a few cm/s at the
    orbit of Mars? Isn’t that all it would take.

  • Ronald March 28, 2013, 11:30

    In response to this and the previous two related posts on comets, the Oort Cloud and interstellar travel;

    It makes little sense to me that there would be a fast ánd a slow track to the stars at the same time, among human civilizations which are still in regular contact with each other. In my opinion the fast mode would always win.

    I also have my doubts about the necessity and even the usefulness of Oort Cloud objects and the like, as so-called stepping stones to the stars.
    This is, because it seems to be based on an earth-biased view of ‘refueling’, and the need/use for that is dependent upon the balance between return versus investment plus risk.
    What I mean is this, a fast track to the stars, without some exotic physical breakthrough, depends on the mastering of two technologies:
    – a propulsion system (be it fusion, fission or laser) which can attain a significant proportion (at least 5%, preferably 10 or 20%) of c.
    – a suspended animation (‘hibernation’) system, which allows passengers to remain in a state of very low metabolism, aging and hence metabolic requirements (food, water, oxygen) for a long time (many years, decades), and be revived safely after that period.

    As basic physics teaches us, once a space craft is at its maximum speed after acceleration, it will just keep coasting along until it is decelerated, which also costs an enormous amount of energy.
    No need, nor usefulness in slowing down for refueling.

    The settling of Oort Cloud comet like objects in view of interstellar travel and colonization is only useful if those objects have a lot of interesting resources to offer, (a lot) more than it takes to slow down, settle, build up a local technological civilization, build up a large space-faring capability, and face all the risks and adversities of such frigid outposts.

    I still strongly believe in the fast(est possible) way to the stars.

  • James D. Stilwell March 28, 2013, 12:50

    Anyone contemplating building worldships should read Harry Bates short story “Alas, all Thinking” to realize the perils of life aboard a comtainer of a few thousand souls traveling for 100s of years….Living at the dead end of a tamed society, where ‘why’ becomes a dangerous word, so horrifying is endless meditiation, that together it could lead to mass suicide…Marc Millis is right, centuries of starflight time will be required before the little details of human group sanity become crystal clear….Of course a Star Trek civilization would change everything….

  • Astronist March 28, 2013, 13:12

    I wouldn’t exaggerate the danger long-period comets may pose to Earth. Certainly they come in much faster, but only have two shots at hitting us every perihelion (assuming they cross Earth’s orbit at all). Then we don’t see them again for thousands of years. The reason near-Earth asteroids are such a threat is that they share the same orbital space, and may encounter Earth again and again every year before finally striking the planet.

    Stephen

  • Orbital March 28, 2013, 15:25

    Very good Carl Sagan video about setting off into the interstellar night with comets.

    http://www.youtube.com/watch?v=LDIo_SpFI60

  • David A. Czuba March 28, 2013, 16:52

    Oftentimes, we read of the causes of Oort cloud disturbance as “a nudge from a rogue planet or passing star”, yet little evidence exists for those conditions as well. “Passing star” is code for the gravitational wave of a long-passed star. Detecting gravitational waves, as well as the vector, or direction, as they traverse through our solar system, may prove an important method for predicting Oort cloud disturbance. One this point, developing a long-baseline interferometry device that orbits in the elliptical plane antipodal from the largest planetary body, Jupiter, would be very useful. It would provide a day’s “warning” of a gravity wave, and where to look, generally, for any disturbed iceteroids. Call it a solar system tsunami warning system. Then, one among our robotic protection craft stationed at various points would activate to intercept and nudge the object to a safe trajectory to avoid Earth, if that indeed was where it was headed. Given the history of the shooting gallery we call the solar system, the chances are good for a collision every 30 to 60 million years. Like the Cascadia Fault along the Pacific Northwest coast, we’re overdue for a whopper.

  • Horatio March 28, 2013, 17:33

    Comets and iceteroids may have more to offer than just the basic elements they are made of.

    If you can make a small energy investment to set a number of rocks and iceteroids into motion and under controlled collision course, you may be able to profit from affordable kinetic energy. If the intervening objects are massive enough, you could liberate a non-trivial amount (megatons) of energy.

    How to capture this energy (space mills? portable array of mirrors?) is another story.
    But the opportunity is clearly there to be explored.

  • Adam March 28, 2013, 18:02

    Contra James’ pessimism I can imagine people adapting to life on cometoids and living for millennia on such. But the suspended animation option is still possible, perhaps bioengineered. If the Comet-Riders do adapt to star-travel via suspended animation, then we’ll have the start of a species divergence.

  • Brett Bellmore March 28, 2013, 21:33

    Nobody is likely to use comet hopping as a means to interstellar travel, but comet hopping for it’s own sake will guarantee interstellar travel happens, if we get out into the solar system, and don’t otherwise attempt interstellar travel.

    I rather like the idea that comet hopping could lead to speciation; It would result in isolated reproductive pools, after all. OTOH, in the end DNA is just a data storage medium, and how isolated is a reproductive pool if they’ve got access to communications equipment? Only as isolated as they mean to be, I would think.

    But I could still see humanity separating into the star huggers, who have vast energy and matter at their disposal, and use it to (relatively) rapidly spread across the galaxy, and the widely dispersed cometary society, spreading much more slowly, but reseeded at each newly colonized star by the local malcontents.

  • Colin Weaver March 28, 2013, 22:46

    Hmmm, call me paranoid, but … “The point is this: A small but growing human population in the Oort Cloud will master cometary motion, taking advantage of the fact that at 10,000 AU, the speed needed to orbit the Sun is just 300 meters per second. Compare this to the Earth’s 30,000 meters per second and it should be obvious that it takes only a small change in velocity to alter a comet’s orbit.”

    Given the militaristic nature of many human societies, this also means that the Oort Cloud is the ultimate “high ground advantage”. A small change in velocity can alter a comet’s orbit to miss the Earth or other important inner-system locations, but equally a small change in velocity can alter a comet’s orbit to TARGET those same locations.

    Anyone willing to take the risk that when we get that far our we’ll be sensible enough not to use that advantage for the wrong reasons. Imagine someone with the mindset of the North Korean leadership in the Oort Cloud …

  • Eniac March 28, 2013, 23:21

    Paul:

    Gravity assist might pick the speed up to 150 kilometers per second,

    I do not think that is correct. Any speed gained by approaching the sun will have to be given back on the way out. What remains is at most the relative velocity between the sun and the target. ~10-30 km/s, perhaps, and only in the direction the sun is travelling.

    the meeting between the cometary travelers and their fastship brethren would be an interesting one to see. What would these two different branches of humanity still share?

    I don’t know the answer to that question, …

    One thing we can be sure they would share is their history. They would have the same origin, and be very aware of that. Both groups could bring up the same 2013 Centauri Dreams blog entries within nanoseconds on whatever serves the purpose of a “screen” for them, if they were so inclined.

  • Eric March 29, 2013, 1:47

    Hmm. This makes me think Fermi Paradox again. We might want to think of the selection pressures afforded by the ultra-scarcity of energy and other resources. A population living in Oort clouds will have many billion or trillions of opportunities to fine-tune adaptions in that kind of environment.

    It may be intelligence / sentience would have a huge adaptive disadvantage, since energy would be very scarce. Why bother fueling all of that unneeded cognitive overhead? Also, after a population has gone through several generations of munching on more or less interchangeable ice balls, what else could it learn of any use? High intelligence may be useless in a selective environment of mind numbing repetition, of ice ball after ice ball (by the 100s of billions!). Future human populations (or AIs? or current aliens?) living in Oort clouds may have an evolutionary tendency to conserve engery by stripping out everything not directly involved with very slow metabolism and reproduction. They may be as interested in conversation as lichen. Likewise they may have a lichen’s capacity for conversation.

  • Peter Chapin March 29, 2013, 9:13

    Over geologic time I think it’s probably a near certainty that passing stars would cause some disruption of the Oort cloud. In “Vistas of Many Worlds” by Erik Anderson the author points out that in about 1.4 million years Gliese 710 will pass only about 0.8 light years from the sun. At that distance the Oort clouds of the two stars (assuming they both exist) may interact. For example, the inner solar system might potentially pass through the outer edges of Gliese 710’s cloud.

    Such encounters have probably occurred many times over the life of the solar system and they might account for periods of higher than usual bombardment and corresponding mass extinctions due to impacts.

    In any case, I agree with Astronist. A case can be made to invest in protecting the Earth from NEOs since, by definition, they encounter the Earth frequently on short time scales. I don’t think the threat from Oort cloud bombardments is a concern… maybe in 1.4 million years it will be.

  • GaryChurch March 29, 2013, 11:02

    “- a propulsion system (be it fusion, fission or laser) which can attain a significant proportion (at least 5%, preferably 10 or 20%) of c.
    – a suspended animation (‘hibernation’) system, which allows passengers to remain in a state of very low metabolism, aging and hence metabolic requirements (food, water, oxygen) for a long time (many years, decades), and be revived safely after that period.”

    I agree- “the balance between return versus investment plus risk that many seem to think is so important is the major stumbling block.” Money is great stuff- except when it keeps us trapped on Earth.

  • GaryChurch March 29, 2013, 11:37

    “I wouldn’t exaggerate the danger long-period comets may pose to Earth.”

    I wouldn’t trivialize it either. On the scale of geologic time it is essentially a random but inevitable event; the danger is real.

  • william f collins March 29, 2013, 16:01

    I hopefully foresee the development of a gradual interplanetary spacefaring civilization that will gradually expand to the nearby star systems. Sadly, a star trek type civilization will remain an unattainable dream/fantasy.

  • GaryChurch March 29, 2013, 17:14

    “Sadly, a star trek type civilization will remain an unattainable dream/fantasy.”

    Not sad at all william, reality is better.

  • GaryChurch March 29, 2013, 17:41

    “A small change in velocity can alter a comet’s orbit to miss the Earth or other important inner-system locations, but equally a small change in velocity can alter a comet’s orbit to TARGET those same locations.”

    I point out in my essay “Water and Bombs” that it may be a common occurence in the galaxy for a planet to be sterilized as much as possible by bombardment with comets- to make way for the introduction of invasive alien species. Centuries later when the colonists show up they have a basic native ecosystem to build on- the original civilization and all complex life would be gone.

    Stephen Hawking warned us about the hazards of contact with alien civilizations; I believe him. We need spaceships.

  • ljk April 1, 2013, 15:03

    GaryChurch said on March 29, 2013 at 17:41:

    “I point out in my essay “Water and Bombs” that it may be a common occurence in the galaxy for a planet to be sterilized as much as possible by bombardment with comets- to make way for the introduction of invasive alien species. Centuries later when the colonists show up they have a basic native ecosystem to build on- the original civilization and all complex life would be gone.

    “Stephen Hawking warned us about the hazards of contact with alien civilizations; I believe him. We need spaceships.”

    What if our Worldship-traveling descendants end up using the comets of the solar systems they want to colonize in the manner Stephen Hawking and others are worried that some expansionist ETI might do to us? Will that make it alright because the future members of our species are trying to survive?

    Assuming our descendants have not changed so much so that they do not need an Earthlike world to survive on – be it a natural planet or one they terraform – what will make it ethically acceptable to essentially take over another world? No life forms smarter than say a fish or a cow? What if truly livable planets or moons are at a premium in this galaxy?

    We can attempt to clear our collective conscious by saying such events won’t happen for centuries from now. But we are setting in motion today what will be the colonization of the galaxy, or at least the attempt at such an effort. Most people naturally assume that the ultimate point of sending robot probes to the stars is to follow them with human crews for colonization.

    We might also comfort ourselves by saying that our children will only terraform “dead” comets, planetoids, and larger worlds, or that they will remain in space aboard their Worldships, only making brief pit stops at natural celestial bodies for supplies. We also assume that future people will be even more tolerant of beings which are different from them – but will that apply to aliens? Especially the ones that are not humanoid, and those will probably be the majority thanks to evolution.

    The points I just made might be moot, as who knows how things will go centuries in the future, plus can we really stop or control what our children will do once they are far from Earth, and have superior technology and information at that. However, I hope we will continue to think beyond primarily the technical aspects of reaching Alpha Centauri, just as we hope any ETI coming our way are just saying Hi out of scientific curiosity and do not plan on staying.

  • Brett Bellmore April 2, 2013, 6:50

    “Assuming our descendants have not changed so much so that they do not need an Earthlike world to survive on”

    If they’ve arrived at a star via world-ship, I think we can safely assume they don’t “need” planets to survive on.

  • GaryChurch April 3, 2013, 11:21

    “-what will make it ethically acceptable to essentially take over another world?”

    When they write history books about it then they will start worrying about ethics.

  • tom April 8, 2013, 19:51

    Keeping manned space travel in the realm of reality has brought out very interesting ideas. I find all the ‘psychological’ speculations are about how ‘we’ would endure in ‘endless’ spaceflight. The imagery of hordes of defeated humans running about like ‘rats in a boiler room’ begs biased from peculiar authors. Most of the 7 billion+ humans on Earth don’t have 3 meals a day and secondary educations… much less ‘due process’. Worldships should give a model of ‘sustainability’ & ‘rising standards’ of living… given the nature of multi-generations living and dying together, this is not unlike our nature of building farms or towns like our ancestors have been doing since the beginning of recorded civilization. Where will we be in the next 100 millennium? I venture that no great leader from the Pliocene imagined the world we live in now. As we may be similarly disadvantaged, but sufficiently endowed to invest on such longterm goals.