Wired Looks at Advanced Propulsion

by Paul Gilster on May 5, 2009

Wired has picked up on our Frontiers of Propulsion Science book with just published interviews of Marc Millis and Eric Davis, co-editors of the volume. Interviewer Sharon Weinberger had a tough assignment, dealing with a 739 page collection of technical and scientific papers aimed, as she notes, at scientists and university students. But her questions were well chosen, particularly in drawing out why a book like this was necessary.

Defining the Terms

fps_cover

Marc Millis, founder of the Tau Zero Foundation, noted the need for a single, defining reference point outlining the current status of research and the opportunities presented. Thus the motivation:

To clear the way for progress, my colleagues and I decided to compile this one document covering the status, issues, and unresolved questions behind a variety of known concepts, and to link the ideal goals back to real physics details. To the extent possible, we endeavored to treat these subjects impartially; showing both their visionary relevance and their critical issues.

All of this is in the context of building a base for future work more than hawking the merits of any particular approach. Moreover, advanced propulsion studies needed a volume that identified the founding references that later work could build upon:

The intent was to create a document that other researchers could use as a reliable starting point for productive research – chipping away at the issues and unknowns that might one day enable practical interstellar flight.

The book emerges into an environment where the decision to re-play Apollo has seen cutbacks in the kind of fundamental research pursued by projects like Breakthrough Propulsion Physics, which Millis once headed at NASA. The situation is not new. Three times more private funding went into propulsion physics research in the late 1990s, Millis notes, than was supplied by government. The trick now will be to encourage private initiatives to publish their results widely, for the benefit of the entire community.

Rigorous Concepts, Testable Hypotheses

These are thorny matters in a field as prone to exaggerated claims as cutting-edge propulsion, but high-quality research that engages the scientific community through peer-reviewed journals is out there. Eric Davis notes the need for rigorous, lab-tested concepts of the sort he pursues at the Institute for Advanced Studies at Austin, and also as CEO of Warp Drive Metrics:

…there is no general hesitancy toward conducting experiments by scientists. There is a larger question that looms in this regard: “Does a particular concept have a rigorous hypothesis or theory worth testing in the lab?” This question addresses whether any concept is testable. According to the scientific method, experiment must be driven by hypothesis, or in absence of a hypothesis, one uses laboratory empirical studies to produce a hypothesis. There are an enormous amount of concepts floating around out there and most of them do not have a testable hypothesis. That makes it very difficult for any serious scientist to justify doing experiments.

Even those ideas that make the grade of testability can fail the test, as some of the concepts examined in Frontiers of Propulsion Science make clear. A serious-minded inventor with a breakthrough in mind will, if confronted with such evidence, go back to figure out where the problem is. But not everyone takes the scientific method so seriously, Davis notes:

Often, however, the inventor holds on to his original belief, attacks the independent evaluation process as being flawed, and continues to hype his claim, a sure indicator of the pathological science position that is not self-corrective. In this case, as time passes and no positive contribution to the energy field emerges, the process of independent evaluation becomes more and more appreciated as unbiased.

In Search of a New Model

Getting fewer sales pitches and more credible research is what interstellar studies needs, which is why Frontiers of Propulsion Science stands out (in the interest of transparency, I should note that I wrote the first chapter of this book, so consider me an interested party). Where we go next seems clear. NASA did support the compilation of Frontiers, but that was its last contribution to such research, with further support withdrawn as of October of last year. Now we turn elsewhere. A growing commercial space sector gives hope of private funding to support rigorous research. Driving the attempt is not, as Millis notes, the kind of Cold War tension that boosted Apollo, but today’s understanding that the very habitability of Earth is endangered.

Is the answer to Fermi’s ‘Where are they?’ question that technological civilizations simply cannot survive their growing pains? A culture unable to muster its defenses against space-borne impactors, facing the ever-present prospect of future war with advanced weaponry and contemplating environmental change may well wonder if survival is possible. Basic research into the options for getting off-planet is the kind of insurance policy it should create, if not governmentally, then by private initiative.

And that, in support of Tau Zero, is why this site continues.

{ 26 comments }

Paul Titze May 5, 2009 at 12:09

After finishing the last chapter of the book, I was left with more questions than I originally thought of which means the book did a good job.

Cheers, Paul.

tacitus May 5, 2009 at 13:04

Is the answer to Fermi’s ‘Where are they?’ question that technological civilizations simply cannot survive their growing pains? A culture unable to muster its defenses against space-borne impactors, facing the ever-present prospect of future war with advanced weaponry and contemplating environmental change may well wonder if survival is possible.

You know, it’s likely we’ll have more than one bite at that cherry (though hopefully we won’t need more than one!). There aren’t too many scenarios where a global catastrophe will completely doom us as a species, especially if we do it to ourselves. If the doomsday event is a bioterror-caused global pandemic, all-out nuclear war, or global warming, there’s likely to be enough of us left to pick up the pieces and try again, and we won’t have to do it from scratch either. (Biological Armageddon is probably the most likely, but I suspect that there would be enough time for some groups to take action and isolate themselves from the agent in almost all scenarios.)

Of course, if there is a space-borne disaster like a massive comet or asteroid impact, or the sun acts up, or a gamma ray burst sweeps over us, or a supernova happens too close to us, then we could be wiped out completely, but we’re not more than 50 years away from being able to defend against the only one of those that is likely to happen in the next few hundred years (the asteroid/comet impact).

So, with those considerations, I am not sure that self-destruction is as obvious an answer to Fermi’s paradox as some would have it. It is possible that after multiple failures, there simply will not be enough resources left to carry on, the ecosphere having sustained too much damage, or it may be that getting to the point where a civilization is off the home planet is not the problem, but what comes afterwards. Interstellar travel looks to be a far greater hurdle than migrating out into the Solar System, and perhaps as weapons become even more dangerous in the future, all out war between planets within the same solar system is the type of thing that finally does a civilization in.

Basic research into the options for getting off-planet is the kind of insurance policy it should create, if not governmentally, then by private initiative.

Absolutely! Space elevator here we come!! :-)

Administrator May 5, 2009 at 13:19

tacitus writes:

we’re not more than 50 years away from being able to defend against the only one of those that is likely to happen in the next few hundred years (the asteroid/comet impact).

Agreed, though with this caveat — I think we’re fifty years away from defense capability only if we continue to push the needed research. Depending on the priorities we assign, what should take fifty years could stretch out considerably!

Administrator May 5, 2009 at 13:21

Paul Titze’s comment above is really positive to me, because the book was aimed at providing the reliable research basics while pointing to where things might go next. Wonderful to hear this confirmation.

John Hunt May 5, 2009 at 13:49

I think that our emphasis should be placed upon near-term propulsion methods which can be reasonably fielded within this century. There will always be a place for fundamental research of breakthrough propulsion methods. But our first priority should be the development of the first true interstellar mission which will address the most pressing issue of our time — namely, the threat to humanity from self-replicating technology. Given this near-term threat, hypothesizing about improbability drives using hundreds of tons of unobtanium should not distract us from working on the immediate priority.

John Hunt May 5, 2009 at 14:13

Tacitus, You are leaving out two of the most probable existential technologies: 1) nanotech and 2) self-replicating chemicals.

Imagine if, in 50 years, all around the world, colleges are purchasing cheap desktop molecular manufacturing equipment. You type in a chemical structure and in milliseconds the machine combines carbon, hydrogen, oxygen, and nitrogen atoms into the molecule of your choice.

So, say a graduate student comes up with a brilliant idea. Why not write a program which directs the machine to incrementally produce entirely novel chemicals of ever increasing size which do not necessarily arise from natural biochemical pathways. He leaves the program running overnight and in the morning finds that the machine has produced hundreds of thousands of novel chemicals.

Now, say just one of those is self-replicating, uses CO2 as feedstock, sunlight as its energy source, and is small enough that it is blown about by the breeze. If it is limited only by the quantity of atmospheric CO2 then what good does it do for “some groups to take action and isolate themselves from the agent”. How long can they survive before they have to enter a collapsed biosphere deplete of atmospheric CO2 but saturated with the self-replicating molecule?

How do they launch to a lunar base without bringing that self-replicating chemical with them?

tacitus May 5, 2009 at 15:32

John, thanks for freaking me out :-)

I guess I would lump that type of scenario in with the chances of a post-expansion-into-space catastrophe. I don’t know how feasible the type of nanotechnology that scenario would require, but I would think the odds are it won’t happen until we’ve begun the move out into the space in a meaningful way. But if we’re stuck within our own Solar System for the next 500 years or more, there is still plenty of time to screw things up. Even if we survive Earth’s destruction, it would make things much harder to maintain a viable civilization and recover without it.

ljk May 5, 2009 at 15:58

I hope the idea of “saving” humanity from a world that it may have
made unlivable in the process is not the overall goal of interstellar
travel. It will be easily argued from this point that if we as a species
wrecked one planet then we will simply do the same at a new world,
then have to keep moving on in order to survive. We will come across
as bad as the aliens in the 1996 SF film Independence Day. This is also
the theme in the new film Battle for Terra.

Rescuing the human race from a disaster beyond our control will be
another matter, of course. But again we should not focus on the
“negative” reasons for interstellar travel as the first and foremost
reasons to go out to the stars. Instead let us focus on the initial
reasons we wanted to go into space to begin with: To see if it can be
done and to learn directly what is in the galactic neighborhood. In
other worlds, for the sake of exploration and knowledge.

kurt9 May 5, 2009 at 16:49

One does not need interstellar travel to escape a global disaster. Dispersion throughout the solar system in O’neill style habitats is sufficient. The kind of “desktop molecular manufacturing equipment” that John describes should make construction of those O’neill habitats far easier than otherwise.

I actually have the opposite attitude than John does about this kind of physics research. Current space transportation ventures are in the $100 million dollar range. Anything interstellar is going to be in the billions of $ range for the next century, based on current technology. Working on the
breakthrough physics, as presented in the book, could be done for a few million to tens of millions of $ range. Although breakthrough physics is a black swan, it could represent “low hanging fruit”, financially speaking.

tacitus May 5, 2009 at 18:28

It will be easily argued from this point that if we as a species
wrecked one planet then we will simply do the same at a new world,
then have to keep moving on in order to survive. We will come across
as bad as the aliens in the 1996 SF film Independence Day. This is also
the theme in the new film Battle for Terra.

I believe that’s unduly pessimistic. Although it’s only been 64 years, we have lived with nuclear weapons without wiping ourselves out so far (though it’s been close once or twice!), and if we ever get to the stage where interstellar travel is routine then pressures over “living space” and resources will ultimately decline as we spread out and our technology continues to improve. Sure there will always be dangerous rivalries of some sort but I believe that if and once we get out of this evolutionary bottleneck of being stuck on the same planet and in the same solar system, our long term future is pretty much assured. When and if we get to that point, I have no idea.

Brad Neuberg May 5, 2009 at 20:42

I posted this on the Wired site but it doesn’t seem like its making it through, so posting it here as well…

Great interview! I’m a big fan of the Tau Zero Foundation (make sure to check out their up to date blog at http://www.centauri-dreams.org/ which is always chock full of new scientific developments affecting interstellar flight, exoplanets, cosmology, and more). Marc Millis and Eric Davis have a good mix of skepticism plus open mindedness; it’s very rare to find such a mixture. The original Project plan written by Marc (http://gltrs.grc.nasa.gov/reports/2004/TM-2004-213406.pdf) is something that anyone who is trying to do unconventional yet scientific research should read; it sets out a strong set of policies for intellectual honesty while remaining open minded to the unconventional. I work at Google and recently pointed some colleagues over at Google.org working on breakthrough energy research (the RE < C initiative focused on making the price of Renewables less than Coal: http://www.google.org/rec.html) at Marc’s original project plan, since it provides a great framework for approaching breakthrough ideas. I often recommend it to anyone who is scientifically or organizationally approaching new ideas.

One question; I don’t have alot to give but I’ve wanted to send a small amount to help support the Tau Zero Foundation every month (similar to a public radio subscription). Marc or Eric, is there a way to donate this way to the Foundation?

Best,
Brad Neuberg
http://codinginparadise.org

James M. Essig May 5, 2009 at 23:39

Hi Folks;

Let’s keep our hopes up for the test of the VASIMR engine designed by the Ad Astra Rocket Company. They are scheduled to test it on the ISS this year. The rocket could accordingly get us to Mars in only 39 days and my estimate is that with an ordinary small but shielded nuclear fission reactor, out to the kuiper belt in one year, even much less if the active fission fuel isotope to overall reactor mass including shielding is high enough.

If the VASIMR proves its meddle, I can see great things comming as a result in short order as far as the planetary solar system and the Kuiper Belt being opened up for human crewed missions.

Now, plasma can be accelerated on a particle basis to arbitarilly high energies commensurate with the total acceleration potential that the charged particles pass through. Fusion, then matter antimatter reactions, and perhaps even zero point field energy extraction can enable ever higher gamma factors for the exhaust stream.

Even if we are limited to using the zero point fields for some sort of nuclear energy or nuclear energy like localized extraction or interaction energy on the scale of picometers or femtometers, instead of for repulsive field effect like macroscopic schemes, we will still in theory perhaps be able to achieve reactionary thrust propulsion through space to arbitrarilly high gamma factors thereby opening up the entire visible cosmos and far beyond its current boundaries for human space flight.

You never know, researchers at the LHC and/or the Relativistic Heavy Ion Collider luminosity upgrade might discover some reaction that is more exothermic than pure matter antimatter annihilation as we know it. If any such reaction exist, it is likely to be at the quantum-chromo-dynamics level or perhaps even sub-QCD level. I am thinking of an additional nuclear or sub-nuclear force in particular.

Either way, this very year, we are given the prospect of a technology that is an intermediate step between our first human missions to our nearest stellar neighboors and just plain old going back to the Moon under ordinary chemical rocket power and slow ordinary chemical rocket power trips to Mars which would take at least 6 months.

My advice is, in addition to being practicioners of Tau Zero, we need to strongly advocate for the utilization of the VASIMR rocket which has already been developed on some scales.

James M. Essig May 6, 2009 at 0:08

Hi Folks;

I may have gotten the date for the ISS test wrong and assumming that the Ad Astra Rocket Company’s website is up to date, the test year will be 2012. The quote below is taken from the Ad Astra Company’s website.

“Ad Astra is testing a full-scale ground prototype called the VX-200. This test will pave the way for the construction of the first flight unit, the VF-200-1 to be tested in space in 2012.
The VF-200-1 engine will consist of two 100 kW units with opposite magnetic dipoles in order to have a zero-torque magnetic system. The electrical energy will be coming from ISS at a low power level, stored in batteries and used to fire the VF-200-1 at 200 kW. The VF-200-1 project will serve as a “pathfinder” for the ISS National Laboratory by demonstrating a new class of larger, more complex science and technology payloads.”

Note that Ad Astra Rocket Company’s website is available at the following link:

http://www.adastrarocket.com/home1.html

Ronald May 6, 2009 at 9:44

John and tacitus are basically referring to the same fundamental risk to a civilization and a planet, which can be described as a deadly global epidemic (pandemic) be it biological or technlogical.

And exactly this risk might offer a possible (partly) answer to the Fermi paradox in another way than just the self-destruction of a civilization, which can be summarized in one word: contamination.

Maybe other advanced civilizations have learned, either through interstellar communication or the hard way, that interplanetary contamination in the broadest sense poses the single greatest risk to any civilization and that, therefore, there exists some kind of (inter)galactic prime directive of isolation and non-(or minimal) intervention.

BTW, I strongly disagree with the idea that small space-based colonies, such as O’Neill habitats or modified asteroids, giant comets, Kuiper Belt/Oort Cloud objects and the like would be sufficient, or even better, for survival, as compared with a planet.
On the basis of the concept of island biology it should be noted that small islands pose much (in fact exponentially) greater extinction risks through chance events (s..t happens) than very large habitats. And even more so if the ‘island’ is of great (technical) complexity.

Therefore, I still believe we need large habitats, such as planets, for long-time survival.

Administrator May 6, 2009 at 9:44

Brad Neuberg writes:

One question; I don’t have alot to give but I’ve wanted to send a small amount to help support the Tau Zero Foundation every month (similar to a public radio subscription). Marc or Eric, is there a way to donate this way to the Foundation?

Brad, not sure if we’re set up for automated withdrawals or anything like that, but regular contributions are absolutely welcome. Best thing to do is leave a message for Marc on the Tau Zero primary site (www.tauzero.aero). He’ll have the latest on where we are re contribution setups.

Ronald May 6, 2009 at 10:27

tacitus May 5, 2009 at 18:28
(…) I believe that if and once we get out of this evolutionary bottleneck of being stuck on the same planet and in the same solar system, our long term future is pretty much assured. (…)

Exactly, fully agreed! Also see my previous post above. It has even been assumed by scientists and authors referring to the (modified) Kardashev scale (rather based on dissemination than energy harnessing), that once a civilization reaches the level of interstellar, than it basically becomes indestructible. This qualification may be arguable, but it would certainly increase the chances of survival of that civilization or at least of that species and its offspring in a spectacular way.

Ronald May 6, 2009 at 10:34

But I also agree with ljk, that we shouldn’t focus so much on notions of ‘escape’ and survival, but rather and primarily on the goals of exploration, knowledge, and the spreading of life. From this enhanced survival may follow as a result, not as a goal per se.
Before settling other planets I think we should even pass the test of being able to manage our own in reasonably sustainable ways (e.g. with regard to major issues like energy, food production, population control, global peace).

ljk May 6, 2009 at 12:07

Tacitus, I was not attempting to be “unduly pessimistic”. I usually
consider myself to be rather optimistic when it comes to the benefits
of going into space for our species and society.

I was responding with my view on one of the stated goals of interstellar
exploration from the main article of this thread, that we may all need
to hop into interstellar arks and take off for new digs should something
bad happen to our current home world.

I said there and repeat here that going to the stars just because we are in
big trouble – especially if we created the problem in the first place – should
not be the first or overarcing goal of spreading out into the galaxy unless
we have absolutely no other choice. However, I have the unfortunate
feeling that if things get really bad on Earth we won’t be able to leave our
planet at all, let alone set off for Alpha Centauri or anywhere else in the
Milky Way galaxy.

There is another issue of one of our stated goals of interstellar eminent
domain which also needs to be more fully addressed. This is in regards
to finding an Earthlike exoworld. Most often one of the desires for finding
such a place involves our descendants travelling to such places. Unless
we have come up with a form of FTL drive by the time our species can
traverse at least the nearer regions of the galaxy, few known star systems
are near enough which will allow any starship with a human crew to fly out
and back for a visit. If humans do go out to this “new” Earth, it will be for
a permanent stay. Anything else will be a ridiculous expenditure of money,
time, and resources.

Now, unless there is some aspect of a world that resembles Earth enough
so that we could live on it without a space suit or pressure dome which I
am unaware of, there is no way I can think of where a planet that has
naturally developed to resemble our world could do so without more
than a little help from native flora and fauna. Even if there is nothing on
this world which we would consider to be seriously intelligent and aware,
there will still be life on this exoplanet, probably a lot of it.

So what do we do about this? Do we still send a colony ship full of humans
(and it may have to be a multigenerational one, which brings up a whole
bunch of new issues) to this new world and let them start a new society
there – assuming anyone could stop them at all in the first place? Will the
new arrivals find a way to live in harmony with the native organisms, or
will it become an us vs. them situation?

And what happens if there is an intelligent species on this Earthlike place?
Even if they are “primitive” by our standards, do we just let our descendants
move in anyway?

Just as life on this planet has wiped out its competitors, or been wiped out
itself by external forces since the first microbes appeared almost four billion
years ago, is this just the natural state of things everywhere with organic
beings, that one invades the space of another to take their land and resources
to survive? Would our future human colonists simply be acting out part of
an ancient and cosmic drama? Or are we still clueless children who do not
have any idea what we are about to step into out there?

To boldy go where no one has gone before will definitely be interesting,
that is for sure.

Pat Galea May 6, 2009 at 14:03

I’m just over halfway through the Frontiers of Propulsion Science book. It’s been a great read so far! Lots of juicy material to chew on here.

Tau Zero Foundation donations can be made here using PayPal:

http://tauzero.aero/site/html/support_us.html

The images for the PayPal buttons seem to have disappeared, but if you hover your cursor just below where the donation boxes are you should see the cursor change shape to indicate where the buttons are hiding.

Ronald May 11, 2009 at 11:40

There may be another (partial) answer to the Fermi Paradox, that I have been pondering recently and that worries me a bit. This one is not in contradiction with others that are mentioned here in in the next thread, but rather encompasses and supercedes them: the age distribution of solar type stars in (the galactic habitable zone of) our Milky Way galaxy.

I haven’t done my home work on the population structure of solar type stars in our MW properly yet, as I mentioned in another thread (see “How many Stars in the Galaxy”, http://www.centauri-dreams.org/?p=6606), but I have been getting the following preliminary impression, particularly from the work of Lineweaver: An Estimate of the Age Distribution of Terrestrial Planets in the Universe: Quantifying Metallicity as a Selection Effect (arXiv:astro-ph/0012399v2 9 Mar 2001); The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way (Science, 2004);

I quote from the former publication:
“The analysis done here indicates that three quarters of the earth-like planets in the Universe are older than the earth and that their average age is 1.8 ± 0.9 billion years older than the earth”.

And from the latter publication:
“By comparing the age distribution (…), we find that ~ 75% of the stars that harbor complex life in the Galaxy are older than the Sun and that their average age is ~ 1 Gy older than the Sun”.

Remarkably, I often found, also in other publications about solar twins, solar analogs, and the like, that (significantly) older age for a sunlike star is generally considered a virtue, because it would have allowed for ample time for the development of complex life. This by itself is most probably true.

However, what surprises me is, that the very important issue of such a star gradually evolving off the main sequence and hence blowing its own habitable zone outward, even long before actually becoming a subgiant, is omitted in this line of reasoning.

Our own Sun, a G2 star, is expected to become too bright and hot for any higher life in about 500 to 600 million years, when the Sun is about 5 gy of age (and too hot for any life in about a billion years).
In other words, the ‘habitable life span’ of a sunlike star is considerably shorter than its entire main sequence life span (assuming an earthlike planet in the continuously HZ).
And this habitable life span will be correspondingly shorter for larger-mass, brighter sunlike stars, such as F9, G0 (and longer toward later G and early K).

In fact, several of the solar twins hailed in recent years as good candidates for habitable planets, such as 37 Geminorum, 16 Cygni B, HR 2290 (= Hip 30104, HD 44594) and Hip 73815 (HD 133600), may already be (much) too old, in combination with their stellar characteristics, to be comfortable to (complex) life.

The above argumentation is why I would favor slightly dimmer solar type stars (mid-later G, early K) as more optimal candidates for habitable planets with complex life: the longer habitable life span remaining from the moment that complex life emerges.

John Hunt May 11, 2009 at 22:43

plasma can be accelerated on a particle basis to arbitarilly high energies

James, what is limiting being able to do this? Is it the length of the accelerator? The quantity of power necessary to accelerate a significant amount of fuel to .99c, or what? Could power be beamed to a craft with an accelerator? Can the accelerator be either linear or circular?



we need to strongly advocate for the utilization of the VASIMR rocket

By my calculations, high-end VASIMR could get us to Alpha Centauri in about 4,400 years. That speed is good for getting around our solar system but hopefully advances can get it at least twice as fast. I don’t see a logical reason that magnetic fields couldn’t accelerate the ions to any particular speed. So I agree that we should advocate for VASIMR to be used. I think that it is one of the more developed forms of advanced propulsion.

small islands pose much greater extinction risks through chance events

Ronald, I totally agree. My emphasis would be that planets provide vast quantities of resources whereas O’Neill colonies would either be dependent on contaminatable planet/asteroid resources or be 100% efficient. Also, stuff breaks down and it’s always good to be able to construct from raw resources.

once we get out of…being stuck on the same planet…our long term future is pretty much assured.

Yep, I too agree. Although I ultimately advocate for an interstellar colony to overcome Fermi concerns, a Moon or Mars colony seems like worthwhile insurance and also practice for “Beyond”. However, I am nervous about whether we’ll establish a truly self-sufficient lunar or even underground base by the time of the first potentially existential self-replicating technologies (2020-30?).

we shouldn’t focus so much on notions of ‘escape’ and survival, but rather and primarily on the goals of exploration

Sorry Ronald, I’ve got to disagree with you here. If we had the time that would be fine. But multiple self-replicatng technologies are imminent. Exploration is a recipe for delaying survival strategies. Lunar missions should first be about establishing a base and learning to live off the land. We lose little by exploring later.



a world that resembles Earth enough so that we could live on it without a space suit or pressure dome


ljk, that’s exactly what I’m talking about. The first exoplanet we inhabit will probably have a CO2 atmosphere of a different pressure, different gravity, probably only ice water, and no plants or bacteria whatsoever. Only through technologic paraterraforming will it be liveable. But we can do exactly that. There’ll probably be no native microbes to deal with.

In other words, the ‘habitable life span’ of a sunlike star is considerably shorter than its entire main sequence life span

If we can come up with a logical reason why intelligent civilizations don’t exist and therefore our civilization is very unique then this could be good news since it doesn’t so strongly press upon us the idea of universal self-extinction.

Administrator May 12, 2009 at 10:35

Ronald writes:

The above argumentation is why I would favor slightly dimmer solar type stars (mid-later G, early K) as more optimal candidates for habitable planets with complex life: the longer habitable life span remaining from the moment that complex life emerges.

Good points, Ronald, and you’re right — the age issue is usually cited as an advantage rather than as a potential problem re the size and placement of the biosphere. I do note, though, that we’re still in the early going re reliable estimates of stellar ages, particularly on the macro-level we’re discussing here.

Ronald May 13, 2009 at 6:59

Thanks, John and Paul, for your interesting comments.

John: “The first exoplanet we inhabit will probably have a CO2 atmosphere of a different pressure, different gravity, probably only ice water, and no plants or bacteria whatsoever. Only through technologic paraterraforming will it be liveable.”
I totally agree and the first specimen of that kind of planet will undoubtedly be a solar planet (sorry for the open door): our own Mars. It can gradually be terraformed, first within domes, then the entire atmosphere. According to people like Zubrin, Birch, Ahrens, Fogg, the atmosphere could be breathable in a couple of centuries to a thousand years. Maybe within decades there could be self-reliant and sustainable colonies, like oases in the desrt. This would already enhance humankinds survival chances significantly (though nothing like a completely habitable exoplanet).

“If we can come up with a logical reason why intelligent civilizations don’t exist and therefore our civilization is very unique then this could be good news since it doesn’t so strongly press upon us the idea of universal self-extinction.”
A positive attitude towards Fermi, I like that. Another added advantage to ‘civilizational loneliness’ in our galaxy would be lack of competition, no risk of having to fight for our place in the galactic pecking order.

Further to my previous post and later G-stars: a typical G5 star with a mass of about 0.9 solar and a luminosity of about 0.8 solar could be expected to have a complex-life-habitable-lifespan some 10 – 15 % longer than our sun, i.e. some 5.5 – 5.8 billion years (instead of our sun’s just over 5 billion orso, in other words another 0.5 – 0.8 gy longer). That may not seem like a big difference, but from the rise of complex life on our planet to the present is ‘only’ some 500 – 600 million years, and complex life may only have a similar period left on earth, before it gets too hot. In this view, a similarly long added period constitutes a significant advantage for any higher life.

For a typical G8/K0 star, the hab-life span would easily be 70 – 100% longer than our sun’s. Now, that’s really interesting, roughly 3 – 5 billion years added for the survival and evolution of complex life (provided that geological activity can also continue this long).

And that’s why I like these dimmer/later solar types stars so much: significantly longer stable lifespans. And they are more abundant as well. Brings us back to Fermi though.

Pat Galea May 27, 2009 at 18:38

I have now finished the FOPS book, and I’ve written up an overview here:

http://galearesearch.co.uk/archives/132

It’s not really a review, but it might be useful for anyone who’s wondering whether they want to buy it or not, as it should give a feel for what the book is covering.

Administrator May 27, 2009 at 19:36

Pat, what a terrific job you’ve done on this. Thanks for the link, and I hope anyone pondering buying the book will give this a read. Fine work, Pat.

Pat Galea May 28, 2009 at 16:57

Thanks! It’s a fantastic book, and I hope that prospective researchers will find my write-up a useful starting point for appreciating the scope of the book.

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