Ready about

So, here's where things stand with the discussion of Orion, DARPA's "100 year starship".

We currently have the technology to build a ship which could reach Alpha Centauri in 88 years.

In the context of this series on outmigration, our primary purpose in doing so is to migrate some small portion of the human gene pool off-world, to enhance the possibility of our continued survival as a species. This seems to be one of DARPA's purposes as well.

In order for Alpha Centauri to actually warrant traveling to it, we would need to know beforehand that a world exists in that system which is significantly more hospitable than Mars or other locations in our solar system, but devoid of life.

We will likely have the ability to determine this with some confidence in the coming decade. The existence or non-existence of an earth-sized world with a significant amount of liquid water on its surface will probably be known within the next few years, assuming that the Exo-Earth Imager telescope is completed.

If no such world is found, then the search would shift to Barnard's Star. If Barnard's Star proved similarly devoid of habitable worlds, Orion will almost certainly not be built. At least, not the interstellar version of Orion. There would simply be no point.

Assuming that a suitable world is found, determining the existence of life will prove more challenging, but high concentrations of atmospheric oxygen or methane on a temperate world would be a pretty good first clue. If we should find conclusive evidence of life on such a world, that would immediately shift the focus away from colonization toward very cautious exploration. Because a war of the worlds, even unintentional and even on a microbial scale, is likely to end badly for everyone involved.

If our hypothetical "goldilocks world" should prove mostly habitable but uninhabited, the first priority of the new colonists will be terraforming it from "mostly habitable" to truly earth-like. By definition, any world worthy of traveling four lightyears to terraform should be pretty quick and simple to terraform. A need for much more than simple oxygenation of the atmosphere (by photosynthetic or chemical means) would tip the balance back in favor of Mars or Europa for permanent colonization. But we cannot begin to estimate what steps would be necessary for terraformation until we have a pretty good understanding of the world as it currently exists. And until we know those steps, and what resources we can hope to find on that world to help accomplish those steps, we have no way of determining how much of the cargo space of the Orion vessel would be committed to carrying either materiel for terraformation, or equipment for surviving on a non-terraformed world.

This brings us to something of an impasse. We have the technology and resources to build the working parts of Orion. But we do not yet have the knowledge to determine what to carry in it, and for a one-way sojourn to the nearest stars, we cannot leave that to guesswork. Until the Exo-Earth Imager is operational, and we have real data about the planetary systems of Alpha Centauri and Barnard's Star, we cannot proceed much further on this tack.

The good news is, if all goes well we may have the answers we need much sooner than we would realistically begin building Orion.

In the mean time, we have left an enormous question unanswered which is critical for human colonization not only of the stars, but of the other worlds within our own solar system. Our quest for a habitable-but-uninhabited world raises the question of how in fact life arises on a world, and how common this process actually is. So I want to take this discussion on a different tack for a bit, and look at how life arose on earth, and how likely it is that life has arisen elsewhere. For the next several posts I'm going to look at abiogenesis, panspermia, and exobiology generally.

Helm's a lee.

TED Talk on Project Orion

George Dyson on TED Talks, interesting new/old footage from original project.

http://www.ted.com/talks/george_dyson_on_project_orion.html

Project Orion series update

It's been nearly a month since my last post on Project Orion (DARPA's proposed "hundred year starship"), so I want to do a quick recap and an explanation of where the series is going.

So, to recap:

We started with the premise that the ultimate survival of the human species requires that humans establish permanent settlements beyond earth's atmosphere.

We explored different possible locations for human settlement within the solar system. Some or all of these will certainly be colonized, but none of them are especially habitable by humans and other terrestrial life.

We explored the nearest star systems, and determined that the Alpha Centauri system is by far the best candidate for having an earth-sized planet with liquid water on the surface.

We explored existing propulsion systems for reaching Alpha Centauri, and found that only one currently existing method could reach Alpha Centauri within a single human lifetime. That method is nuclear pulse propulsion, which is a polite way of saying lighting off a bunch of atomic bombs behind a space craft and blasting it into the next solar system. Intact.

We learned that the US government has had the plans and technology to build a vessel of this type since 1957. Really. It was called Project Orion. It was then canceled due to the Partial Test Ban Treaty of 1963. The Cold War is over, and now DARPA and NASA are looking at it again. But I'm not sure that governmental agencies or corporations have the attention span for a project of this magnitude. This may be something that interested individuals need to start collaborating on independently of governments.

The next parts of the series will explore what life would be like, both on Orion for 88 years and also beginning settlement and terraformation of an earthlike world in the Alpha Centauri system.

I've had some requests to eventually turn this series into a book. I will probably at least consolidate it into an ebook and make that available here. In the mean time, I'm going to go back through the series and tag the posts as "Project Orion" and "Outmigration" to make then easier to find.

Ad astra!

Farmers in the Sky

It's been almost two weeks since I've posted about outmigration to Alpha Centauri and Project Orion, because there's been so much going on otherwise. I want to get back to that now over the next few weeks, and specifically I want to focus on the logistics of how Orion would realistically be built, and also what conditions would be like for the crews who would, in some cases, be destined to live out their entire lives on board a crowded vessel not much bigger than a modern container ship.

A very significant amount of the habitable space within Orion would necessarily be devoted to agriculture. Other than some gardening and landscaping (and one summer priming tobacco as a teenager) I have almost no background in agriculture whatsoever. But we need to have some basic ballpark estimates of what types of plants (and maybe animals) we would need to grow, how much space is needed to grow them, and what kind of yield we could expect from that space and how many colonists could be fed and clothed with that yield. In choosing the species to bring with them, the colonists need to consider both the environment of the spacecraft and also the environment of the world they ultimately intend to terraform and colonize. A plant which is ideal for one environment may not be ideal for another. On the other hand, it may be that if we have enough information about the colony world, we can tailor our on-board agriculture to best suit that eventual terraforming.

Incidentally, we will be considering the requirements for terraforming some of our earlier colonial candidates within our own solar system at some point in the near future.

So, some of our considerations from the plants we would bring are going to be food yield, fiber yield, wood yield, pollination, planting-to-harvest time and biodiversity.

One plant candidate worth considering is Pearl Millet, which has a yield of about 2000 kilograms per acre in about four months time, which is pretty impressive.

There are others which need to be considered, but for our purposes I'm just trying to get an idea of how much space will be required for agriculture and how many colonists will be supportable by that.

It may well be that the first colonists will be selected not for their skills as pilots or technicians, but rather as horticulturalists.

Steam Engine Time

Back in early November of last year NASA and DARPA announced that they were quietly moving forward with Project Orion, the "100-year starship" first designed in the late 1950's and then scrapped due to Cold War politics. At that time I wrote what turned out to be only the first in a large number of posts about Orion. In the course of researching that post I went, among many other places, to Wikipedia. At the time they had a very short article on Orion, with very little real information.

This afternoon I started researching Orion for yet another upcoming post. I'm planning to write a bit about what the voyage planning and living conditions would be like on an 88-year trip to Alpha Centauri. I needed to get dimensions of the payload space to begin planning how that could be parsed out among 1000 colonists and everything they would need to survive that long, and how that would then transition to colonizing a world without oxygen, four light years away from the nearest COSTCO.

So, shamelessly, I went back to Wikipedia. I was shocked and pleased to find that the current article on Orion had about five times as much information as had been there in November.

I'm also seeing references to Orion cropping up in some unusual places. Non-science-y places. It seems like a general awareness of the Orion Project is slowly creeping into our collective conscious. I think when people learn that we've had the technology to build a ship to the nearest stars since the Eisenhower administration, but that we haven't actually bothered to do so, they're pretty appalled. That's good. It's reasonably appalling.

The fact that Orion planning has survived the DARPA budget cuts so far, in this year of mindless runaway budget disemboweling, is very telling.

The steam engine was actually first invented by Hero of Alexandria in the 1st century CE, but nothing was really done with it until the late 1700s, when suddenly inventors all around the world, independently of each other, began inventing and applying steam engines. Planet earth had finally reached "steam engine time", and so the world steam-engined.

We may have reached whatever critical mass is necessary to start finally building a nuclear pulsed-fission ship to the stars. It's Orion time.

Barsoom, again.

So far we've discussed our options for permanent human colonies within the solar system, and we've examined the current state of interstellar travel and the stars we can reasonably hope reach within a human lifetime. Our search for a home outside of the solar system has been narrowed, essentially, to Alpha Centauri. We have established the possibility (without assigning probability) of habitable worlds there.

We have the technology, right now, to launch a colonial expedition to Alpha Centauri. But we cannot in good conscience do so until we have some idea that they will find a suitable world once they get there.

Our parameters for what constitutes a "suitable world" narrow considerably when we are talking about an 88 year one-way trip.

The world must be well within the habitable zone of the star, and there should be plenty of liquid water on the surface. The size and gravity of the planet should be very similar to earth's. The atmosphere should be dense enough for a person to be able to walk around in it without protection. The atmosphere should not be corrosive or toxic. A person should be able to walk around comfortably wearing no more equipment than a respirator and an oxygen source.

The atmosphere should not, however, contain oxygen. Because oxygen would mean that the planet had already been colonized.

The bottom line is this. Any conceivable candidate for human settlement around the stars of Alpha Centauri needs to be a helluva lot more hospitable than Mars. Because Mars is much, much closer.

The good news is that we currently have the technology, and soon will have the ability, to determine if any earth-sized planets exist within the habitable zones of Alpha Centauri. The NASA mission (SIM, the Space Interferometry Mission) to do so was officially defunded in 2010, so it will be up to other countries or private interests to continue this research. Hopefully Europe, India, Russia or China will take the lead in the Space Race and keep the ball rolling. The United States, unfortunately, seems to have thrown in the towel. But this is a venture "for all mankind", so it really doesn't matter who does the work, so long as the work gets done.

If earth-sized planets are found within any of the habitable zones of Alpha Centauri, the next step is to determine, from here, what the atmospheric composition and hydrography of the world is, and generally learn as much as we can from earth or earth-orbit before beginning the process of sending people there. Amazingly enough, it is probably possible, right now, to build a space-hypertelescope which would give us as much information about a planet around Alpha Centauri as Giovanni Schiaparelli's telescope gave him about Mars.

The telescope is currently called the Exo-Earth Imager (EEI). It consists of multiple orbital mirrors focused into a single telescope, and could presumably be improved upon once it was operational by adding more mirrors. From 10 light years away (more than twice the distance to Alpha Centauri), earth would look like this:

From such imagery we could make some pretty good assumptions about a planet. Or, like Schiaparelli and Percival Lowell, we could make some really bad assumptions. But it's a starting place.

Tatooine

So far we've looked at all three of the Alpha Centauri stars individually for potential habitable planets. There are, however, other possible planetary orbits in a binary or trinary star system.

I remember the first time I read the opening words of the original Star Wars:

It was a vast, shining globe and it cast a light of lambent topaz into space -- but it was not a sun. Thus, the planet had fooled men for a long time. Not until entering close orbit around it did its discoverers realize that this was a world in a binary system and not a third sun itself.

Immediately I thought of Alpha Centauri, and the possibility that Proxima was really a planet like Tatooine (yes, I was that 12-year-old). Proxima isn't a planet. But it is possible for a planet to orbit both stars of a binary system.

Here is what we see most typically:

If the two stars in a binary system are less than three astronomical units apart, the planetary disk tends to form around both of the stars, like Tatooine. If the stars are separated by greater than fifty astronomical units then the planetary disks form around the individual stars. Between three and fifty AU a planetary disk is less likely to form.

The distance between Alphas Centauri A and B is between 11 and 36 AU, averaging 24 AU. This would seem to indicate that a planetary disk around either star is unlikely, however we believe there happen to be planetary disks around both A and B.

A "Tatooine-like" orbit around both stars would take the planet far outside of the habitable zone; it would be rather more like Hoth than Tatooine, except that humans truly could not live there.

All that said, a world around either of the two major stars of Alpha Centauri would, occasionally, be afforded really spectacular twin sunsets.

Stupid Star Wars trivia: The planet Tatooine is never actually named that at any point in the first movie (what eventually became Episode IV of the series). During the filming it was called Utapau, which name was ultimately given to one of the worlds in Episode III.

Pandora and the Comet Empire

Our third and final candidate in the Alpha Centauri star system is Alpha Centauri B, a K1-class orange dwarf star just a bit smaller than our sun. It also happens to be the star of the moon Pandora in James Cameron's movie Avatar.

Alpha Centauri B is slightly less "sunlike" than Alpha Centauri A. However, computer modeling of accretion patterns from the protoplanetary disks results in an earth-sized rocky planet neatly inside the liquid-water habitable zone of Alpha Centauri B on more modeling runs than not. This is not true of Alpha Centauri A, although it is certainly possible that a planet from another orbit might have been captured into a habitable zone orbit of A.

The first salient question which arises is whether or not a planet within, say, 50% of earth's mass in either direction, actually exists in the habitable zone of Alpha Centauri A or B (or Proxima, for that matter).

We don't know if any such planets exist, yet. We do know what does not exist. There do not appear to be any planets in the Alpha Centauri system larger than five times the earth's mass. No gas giants like Jupiter or Saturn, no ice giants like Uranus and Neptune, around any of the three Alpha Centauri stars. Sorry, Mr Cameron. At the very least, the absence of any giant planets in the system means that the orbits within the habitable zones of each of the three stars are available for earth-sized rocky planets, should they happen to exist.

One possibility that we cannot discount yet is that there are no planets in the Alpha Centauri system at all. Given that each of the three stars are distant enough from each other to have had independent protoplanetary disks, and given the high metallicity of each of the three stars ("metal", to an astronomer, is any element heavier than hydrogen or helium), the simple law of averages would seem to indicate that there are planets around at least one of the Alpha Centauri stars, if not all three. But right now we don't know that for sure, because we do not yet have the means of detecting planets as small as we're hoping to find. NASA had a mission well underway to build and launch an interferometry telescope called SIM for specifically this purpose, but it's funding was cut in 2008 and the program was canceled. Hopefully Russia, China, India, the European Union or some private interest will pick up the ball that the United States has dropped and run with it, because a lot of decision making is going to depend on that information.

But, the best computer modeling we currently have for planetary accretion shows that earth-like planets should have formed around Alpha Centauri B, and Jupiter-like and Neptune-like planets should not have. Observation seems to confirm the modeling regarding giant planets; whether it will also confirm the modeling regarding small, rocky planets, only time will tell. Here is the research of Ji-Wei Xie, Ji-Lin Zhou, and Jian Ge of Nanjing University and University of Florida at Gainesville, respectively, regarding planetary accretion around Alpha Centauri B:

http://arxiv.org/PS_cache/arxiv/pdf/1001/1001.2614v1.pdf

Given that it is possible for earth-sized worlds to exists within the habitable zone of Alpha Centauri B, the next question is, "how habitable"?

Alpha Centauri A and Proxima would likely serve the function of clearing the majority of asteroids and comets out of the way, so that a world around Alpha Centauri B would not be constantly pummeled. On the other hand, at least some of earth's water came from comets, so some cometary activity is probably useful. As it stands, we really don't know how most of the water on earth (or Europa or Enceladus or Mars or...) got there, so a better understanding of the role of cometary hydration would go a long way toward understanding how the unique trinary gravitational profile of the Alpha Centauri system is going to affect the hydrographic percentage of its worlds.

New technology is needed to help us image the Alpha Centauri system before sending even robot probes four and a half light-years away. The new technology is almost ready to implement. More on that, soon. With luck and perseverance we should know within the next few years whether or not there are planetary candidates worthy of further exploration around the stars of Alpha Centauri.

Or, you know, three-meter tall naked blue people.

A, B, or both A and B

Our next candidate in the Alpha Centauri system is Alpha Centauri A, a G2V star like our own sun. It is about 10% more massive than our sun, but is otherwise the most "sunlike" of any star on our list. It is locked into a binary orbit with the slightly smaller and dimmer Alpha Centauri B, which will be the topic of tomorrow's post.

Alpha Centauri A and B orbit each other in a period of about 80 earth years, during which time they come as close to each other as the sun and Saturn, to as far away from each other as the sun and Pluto. Each has a habitable zone far enough away from the other that it is not seriously affected by the other star. So, theoretically, there may be planets within the habitable zones of both A and B.

Our searches so far have not detected planets around either A or B, which eliminates the possibility of planets any larger than five times as massive as the earth around either star. There is, however, some reason to believe that earthlike planets may have formed (or may have been gravitationally captured) into the habitable zones of these stars. Planets have already been detected orbiting similar binary star systems, such as Gamma Cephei.

For a planet to be a good candidate for human habitability around Alpha Centauri A it would need to be about 1.25 times the earth's distance from the sun. It is possible, based on current modeling, that an earth-sized rocky planet may have formed there. However, it is also possible that no planets have formed around Alpha Centauri A at all. There is also some concern that the absence of a gas giant planet such as Jupiter or Saturn may indicate a lack of cometary activity in the inner star system, which would mean that the planets of both Alphas Centauri could be bone dry. However, the very fact of the binary nature of the system, plus distant Proxima, means that it is likely that either Kuiper Belt comets or Oort Cloud comets are diverted into the inner star system.

As we will see tomorrow, Alpha Centauri B is a much better candidate for a human habitable planet. But the combination of both stars, plus Proxima, makes Alpha Centauri singularly intriguing, even if it didn't happen to be our closest neighbor.

Three stars for the price of one

We now resume our regularly scheduled series on interstellar outmigration, already in progress.

Based of the speed of space travel currently attainable and the length of a human lifetime, with or without currently available methods of suspended animation, there really is only one star system close enough to be reached by a mission crewed with humans. That system is Alpha Centauri. The very good news is, Alpha Centauri is not one star but three. The even better news is, each of those three stars are potential candidates for human-habitable worlds.

We'll consider each of these three stars in turn, beginning with the closest.

Proxima Centauri is the closest star to our sun, as far as we know. When the NASA WISE-mission data is all crunched we may find a brown dwarf star which is nearer, even within our sun's gravitational influence, but a brown dwarf is not much of a candidate for a habitable exoplanet.

Proxima, however, is an M5 class red dwarf. Any planet within the habitable zone of a red dwarf would be tidally locked with the star, meaning just like our moon, one side of the planet would always face the star while the other side always faced away from it. This is not a good scenario for habitability. However, if there happened to be a gas giant or ice giant planet within the habitable zone, a large moon of the planet might well prove habitable. This may prove true for other red dwarf stars, but Proxima has been proven to not have any planets larger than about two earth-masses in circular orbits in its habitable zone, so if there is a habitable moon there it must be around a planet not vastly larger than itself. However, if the planet were only slightly larger than its earth-sized moon, we might not have detected either of them yet. So this is still within the realm of possibility, at the moment.

Another issue for habitability around Proxima (or any red dwarf star) is that most of the starlight is emitted in the infrared spectrum. Terrestrial plants would need to be genetically engineered to optimize photosynthesis from the remaining visible spectrum light. This does not seem to me to be an insurmountable challenge, but genetic engineering is definitely not my field of expertise.

The third difficulty with many red dwarf stars, and Proxima in particular, is that many of them are flare-stars, meaning that they undergo very large periodic stellar flares, similar to solar flares of our own sun. This is problematical because of the physical proximity of the habitable zone to the star. But not necessarily a deal-breaker.

The verdict on Proxima Centauri? Not an especially great candidate for a planet or moon habitable by humans. But a good enough candidate for us to at least slow down and take a look on our way to the two bigger stars of Alpha Centauri.

More on them, beginning tomorrow.

Sea Monkeys in Space

In July of 2005 a baby girl named Laina Beasley was born to a family in California. Her birth was remarkable only in that she had been conceived 13 years earlier, and then frozen to -235°C.

Earlier in 2005 Dr Mark Roth at the Fred Hutchinson Cancer Research Center here in Seattle induced suspended animation in mice for six hours by introducing them to an atmosphere containing 60 ppm hydrogen sulfide combined with external cooling. There's a really thought-provoking TED Talk about his work here:
http://www.ted.com/talks/mark_roth_suspended_animation.html

Human ova can remain fertile when frozen for more than a year, and human sperm can remain fertile when frozen for more than 12 years. In 2008 Hiroshi Suzuki successfully transplanted a previously frozen ova of a Labrador Retriever into another in order to preserve the genetic material of guide dogs, which are otherwise sterilized before they reach sexual maturity.

Artemia salina, the brine shrimp sold as Sea Monkeys, are able to survive for years in cryptobiosis, during which time they can survive extremes of temperature ranging from −190°C to 105°C for short periods of time. All this without human intervention, other than the school children providing the 105°C environments, with or without adult supervision. In an environment with no humidity and no oxygen they can remain in stasis for up to two years; in a more benign environment they seem to be able to survive indefinitely, like plant seeds.

So. This is where the science of suspended animation stands right now. Mark Roth disclaimers at the beginning of his talk that he isn't interested in using his techniques to extend the range of human space exploration. I happen to be.

But right now, it looks like about an additional 20 years is the most we can do. I'm actually guardedly optimistic that we are making such rapid advances in this field that we may see this number expand to a century or more, in which case all of the stars on my previous list may be within the reach of human colonists.

This would afford us gains in the distance a vessel could travel, but it would still need to be large enough to sustain an ongoing non-hibernating population of all of the colonists, human and otherwise. Because if the colonists reached their destination star and there was NOT a suitable candidate world for colonization, the vessel which brought them would need to sustain them, and their descendants, possibly forever.

But right now, with the suspended animation technology we currently possess we could extend the the reach of a single generation to Barnard's Star. Only. And Barnard's Star, frankly, isn't that interesting of a candidate.

So, Alpha Centauri it is, for now. In the next few posts we'll look more closely at our nearest stellar neighbor, what we might expect to find there, what the trip there might entail, and how we might make that a future home for some of our descendants.

88 Years

The Orion pulsed-fission starship will be able to attain and maintain speeds of 5% of the speed of light, or about 15,000 kilometers per second. This is the fastest speed which a crewed or uncrewed vessel may be propelled with current technology and resources (it is theoretically possible for a vessel which constantly accelerates throughout an interstellar journey to go much faster, but there isn't enough fissionable material in the solar system to sustain this). More, it may well prove to be the fastest speed practical regardless of any advances in propulsion technology. For example, a grain of sand striking an object traveling at 12% of the speed of light will release the energy of a hydrogen bomb. Which would, in the words of Han Solo, "end your trip real quick".

So, 5% of the speed of light. From earth to Alpha Centauri in a mere 88 years. 88 years is a long time, in the scale of a human lifetime. Current human life expectancy world-wide is 67 years, but varies greatly by region. The longest national life expectancy on earth right now is nearly 90 years, in the Principality of Monaco, which speaks well to my retirement plans. In the extreme, the actual human lifespan is constrained by the Hayflick Limit of about 50 cycles of cellular mitosis, which translates to about 121 years. Jeanne Calment of France lived to be 122 years and 164 days old, but she is definitely the upper bracket.

Let us assume, for the sake of argument, that through a combination of eugenics, medicine, and rigorously controlled diet, regimen and environment, that we can guarantee that an entire crew will live to an age of 120 years. Let us also assume that, through an extraordinary but not inconceivable training regimen, all of the crew could be trained to complete the first part of their mission by the age of 14, and then would launch at this time. 102 years from the moment of their births the crew would reach Alpha Centauri, old but spry with another good 18 years left in them to explore the star system.

This seems pretty far-fetched for a number of reasons. But it does demonstrate that it is theoretically possible, with existing technology, for a single generation of humans to reach and explore the three nearest stars, including Proxima.

The next nearest star, Barnard's Star, at 118 years is just beyond the reach of a human generation. The next star beyond that, Wolf 359, is 156 years.

But, still, three stars, two of which are pretty decent candidates for habitable (or at least terraformable) planets, and a third which is at least possible, isn't a bad dice roll. If there was only going to be one other star system within our relatively easy reach, we could have done a helluva lot worse.

In point of fact, unless we choose to use some form of suspended animation (several of which are already possible, more on this in an upcoming post, soon), the first generation or generations of crew will get busy creating the next generations of crew rather soon into the flight. We don't need to make elaborate plans to create "generation ships"; nature will take care of that part all by itself. Because the ship will be a completely closed ecosystem for the entirety of the journey, populations of all species on board will need to be closely regulated. But in the end, there will be plenty of young people to colonize any worlds found around the Alpha Centauri stars.

This method could also be used to reach Barnard's Star, if there were compelling evidence of habitable planets or moons there. But that seems fairly unlikely.

It is not, however, reasonable to expect entire generations to live out their lives and die in a tin can in hopes that their descendants might one day colonize a distant star. To go further than Alpha Centauri or Barnard's Star, a different method is needed. The next post will explore possibilities of suspended animation.

Process of elimination, part 1

The first step in analyzing which of the 28 closest stars are the best candidates for human habitability is to separate them out by spectral class.

19 of the 28, or 68%, are M class red dwarf stars. These will be dealt with as a separate topic, because although they are definitely second-tier (but definitely not bottom-tier) candidates, there are an awful lot of them.

2 of the stars are class DA white dwarfs, which can reasonably be eliminated from the list. These two happen to be companions of class A star Sirius A and class F star Procyon A. The presence of white dwarf companions probably eliminates these two stars as well.

There are no class O or class B stars in the list, which is fine since they would have been eliminated anyway. Class A stars would be marginal, but the only class A candidate is Sirius. Given that Sirius also has a companion white dwarf, it is reasonable to remove Sirius from the list.

That leaves us with our "A list" of Main Sequence F,G and K class stars.

The two Alphas Centauri are G2 (like our sun) and K1 respectively, and our closest neighbors at 4.4 light years away. As an added bonus, red dwarf Proxima Centauri is right on the way to them, so we would get three reasonable candidates for the price of one.

Epsilon Eridani is class K2, at a distance of 10.5 light years.

61 Cygni is a binary system of a K5 and K7 class orange dwarf stars. It is 11.4 light years away.

Epsilon Indi is a K5 star with two brown dwarf companions, 11.8 light years away. Margaret Turnbull considers Epsilon Indi to be our single best candidate for a truly earth-like planet within some 20 light years of earth.

Tau Ceti is a G8 star 11.9 light years away. Tau Ceti was the reason I chose the otherwise arbitrary distance of 12 light years; I wanted Tau Ceti to be included. Tau Ceti is ranked as target number three for the Terrestrial Planet Finder orbital telescope after the Alphas Centauri, if it is ever completed and launched.

Each of these five candidates warrant their own post here, which will be forthcoming.

The next 32 stars after Tau Ceti are all white, red or brown dwarfs. After that is K5 class Groombridge 1618 at about 16 light years followed by a lot more red and white dwarfs. But we have plenty to play with here already, and the rules don't change the further out we go.

Second star to the right

There exists already something called the "HabCat", which is a catalog of stars believed to be likely candidates for having habitable planets. It was created by Margaret Turnbull and Jill Tarter, and prior to Felisa Wolfe-Simon's discovery last year that some prokaryotes were playing merry hell with the periodic able and substituting arsenic for phosphorus to build their DNA HabCat listed some 17,000 stars which potentially hosted life as we know it. I have no idea what Iron Lisa's work has done to this number, but I have to guess that it has increased exponentially.

I'm going to limit my list to those stars which are about 12 light years from earth, but as we'll see later in this series, that limit may prove purely arbitrary. In upcoming posts we'll cover each of these candidates in detail, but right now I just want to present the list. The candidates which are bolded are among Margaret Turnbull's top five candidates for habitable stars out of that 17,000. "Travel time" is how long it would take a vessel, in solar years, to reach that star from earth orbit at 5% of the speed of light, which is the maximum attainable by standard pulsed atomic fission, such as Orion would use. "Distance" is in light years.


NAME, CLASS, DISTANCE, TRAVEL TIME

Proxima Centauri, M5, 4.2, 84
Alpha Centauri A, G2, 4.4, 88
Alpha Centauri B, K1, 4.4, 88
Barnard's Star, M4, 5.9, 118
Wolf 359, M6, 7.8, 156
LaLande 21185, M2, 8.3, 166
Sirius A, A1, 8.6, 172
Sirius B, DA2, 8.6, 172
Luyten 726-8A, M5, 8.7, 174
Luyten 726-8B, M6, 8.7, 174
Ross 154, M3, 9.7, 194
Ross 248, M5, 10.3, 206
Epsilon Eridani, K2, 10.5, 210
LaCaille 9352, M1, 10.7, 214
Ross 128, M4, 10.9, 218
Gliese 866 (A,B&C), M5, 11.3, 226
Procyon A, F5, 11.4, 228
Procyon B, DA, 11.4, 228
61 Cygni A, K5, 11.4, 228
61 Cygni B, K7, 11.4, 228
Struve 2398 (A&B,) M3, 11.5, 230
Groombridge 24A, M1, 11.6, 232
Groombridge 24B, M3, 11.6, 232
Epsilon Indi A, K5, 11.8, 236
DX Cancri, M6, 11.8 , 236
Tau Ceti, G8, 11.9, 238

238 years seems like an awfully long time. Ten generations, even, as we currently count that. But as we will see in a later post, it may be possible for one generation of colonists to depart earth and arrive at Tau Ceti still young enough to start building a permanent colony.

Only Boring Astronomers Find Gratification Knowing Mnemonics

When looking to the nearest stars as candidates for human settlement, we're looking for a star which could have a relatively earth-sized planet or moon orbiting within the "goldilocks zone", the distance at which surface water is at a liquid state. This is most likely to be a main-sequence F, G or K class star like our sun, although an M class red dwarf may harbor possibilities. A later post will discuss the particular considerations of finding a habitable world in orbit around a red dwarf star.

We're going to look, in the next few posts, at the stars out to about 12 light years from our sun. The map below shows the stars out to 15 light years, but it's a pretty good start. Must run, more to come.

Lightcraft: To the stars, by laser

Some of the next few posts here are going to be continuing the discussion of human outmigration, now focusing on possible destinations beyond our solar system.

Before delving too much into the nearby stars and considerations of reaching them, I want to briefly touch on some alternative technologies to pulsed atomic fission which could conceivably get us there.

Regarding space travel propelled by fusion reactors, antimatter, Bussard ramjets, Alcubierre warp-drives and the like; I find them interesting to think about but irrelevant to this current discussion. Technology which may or may not exit one day is intriguing, but I'm much more interested in things that we have the technology to build right now. Because that "one day" may never come, or may only come many millenia in the future.

This is not pessimism, and it is not trivial. Human technology has always progressed in rapid bursts followed by very, very long plateaus, and we may have already reached our newest plateau. The last 50 years have seen huge advances in computer technology and biotechnology and medicine, but most other technologies have remained relatively stagnant. Rocket-powered space flight, atomic fission nuclear reactors, jet aircraft, submarines, digital computers and radio-propagated television all existed in some form or another by the end of World War II. Gasoline-powered internal combustion is still the most efficient motive force we have harnessed to date.

We have no reason, at all, to anticipate that we will advance beyond these technologies within another thousand years, or ever.

So, my focus is on technologies which do currently exist. The rest is science fiction.

I am currently only aware of one technology which exists even in prototype which has an equal or better chance of getting humans to the nearest stars than pulsed fission. That is Leik Myrabo's Lightcraft. Lightcraft utilizes a very powerful pulsed laser or maser (the original prototype used a laser from the Reagan-era "Star Wars" program) aimed at the vehicle to either superheat the atmosphere around it or ablate part of the vessel itself to generate (a lot of) thrust. By not carrying chemical or nuclear fuel, you end up with a spacecraft which is mostly payload.

You may have seen a video for this which was circulating about a year ago on YouTube. It isn't readily apparent, but the video was actually shot around 1999; it just needed a forum like YouTube to reach a larger audience. Here's the video:
http://www.youtube.com/watch?v=6wMpU7AZGvQ

There are some pretty serious issues with Lightcraft from the standpoint of crewed spaceflight. For example, I don't know how most passengers would handle being centrifuged at 6000 rpm, which is apparently necessary for stability. It is not inconceivable that the passenger compartment could be isolated from this rotation, and buffered from the 20 Gs of lift the craft generates on lift-off. But it's a consideration.

Meanwhile, Lightcraft technology is being seriously considered for small payload Low Earth Orbit transport. For a total cost of about $50,000 (including the satellite) Lightcraft can place a 100 kg satellite into orbit. Compared to $50 million + for an Atlas/Delta launch, that's a pretty huge savings.

For interstellar applications Lightcraft is actually a tiny bit faster than pulse fission, but it requires much more time for deceleration so the overall time enroute is slightly more for a 4 lightyear trip that it would be for Orion, but these differences are functionally pretty negligible.

So, as this series continues I'm going to continue to focus on pulse fission, because that technology is far more ready to be applied off-the-shelf to this purpose. But history may one day prove that Lightcraft technology is how we actually accomplish our first missions to the nearest stars.

100-Year Starship: the Navy Weighs In

In 1987 and 1988 the US Naval Academy teamed up with NASA to develop their own version of an atomic-pulse driven ship to the stars. Their version was unmanned, and their destination was very specifically the Alpha Centauri system. Most of the actual advances Project Longshot put forward which actually improved upon Project Orion were in developing the details of a functional pulse-propulsion system. Orion hatched the concept, Longshot started delving into the nuts and bolts.

Some of the astronomy was less than stellar. The star Project Longshot refers to as "Beta Centauri" is actually Alpha Centauri B. I hope. Also, the orbital period of Proxima Centauri, if in fact Proxima orbits A and B at all, is so huge as to render considerations of it utterly insignificant within the span of a human lifetime, or a short interstellar space mission. Nonetheless, the Annapolis pukes US Naval Academy scientists and engineers contributed significantly to the discussion of atomic pulsed propulsion.

Here's the pdf of Project Longshot:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890007533_1989007533.pdf

Midnight Train to Georgia

Yesterday I posted about the possibility of private citizen volunteers collectively building earth's first ship to the stars, rather than waiting for governments or corporations to take the lead.

Governments are hamstrung by their electorate, and corporations are hamstrung by their shareholders. So, take the governments and corporations out of the picture completely, and turn the project over to people who care enough about it to build the ship in spite of the price-tag. This seemed to me like a reasonable solution to a reasonable problem.

Then, this morning, I saw a pretty cool video of Thursday's launch of the space shuttle Discovery, taken by a passenger on a commercial airliner. Then I read the comments on Yahoo about the video. People were actually using the internet to complain that there was no reason to spend tax dollars on the space program. If people cannot appreciate that our space program is the reason they have things like television, the internet, GPS and weather satellites, then a ship to the nearest stars which wouldn't get there in their lifetime if it were launched today is going to be a harder sell.

Especially when there are, for example, 24,000 homeless people right here in King County. Yes, there are many other important things to spend money on. Now I want to express the cold, hard reality of why building a starship is at least as important as funding for housing, health, education, welfare, energy, the environment and defense.

Nobody really likes to say this, but it still needs to be said. As a species we managed to survive the Cold War, and kudos to us for that. But as our population rushes past 7 billion on the way up, the odds of our surviving another century, as a species, continue to dwindle. In addition to the simple and eternal forces of nature which tend to stabilize exploding populations (such as famine and plague), and the ever-present possibility of a one-time mass-extinction event such as an asteroid impact or supervolcano eruption, there is the very real possibility that homo sapiens will be counted among the species driven to extinction by unmitigated global warming. Regarding this last possibility I am guardedly hopeful; as a species we do have the ability to correct this still, if we get off of our collective asses right now and correct it. I'll be posting a lot more about this later; Freeman Dyson, who first conceived of the Orion starship, has actually given us a workable solution to bring down atmospheric CO2 levels to a survivable or even comfortable level. But that is a topic for another post.

The bottom line is, if we as a species continue to keep all of our eggs in one planetary basket, sooner or later our species will become extinct. This is of course true for every species, but we have the unique perspective of becoming aware of the very real possibility of the extinction of our species within what would otherwise have been our lifetimes. Every generation, of course, has fantasized that they were the last; Jesus imagined that he and his disciples were living in the end of times, and we've succeeded in surviving another hundred generations since then. And again, we survived the Cold War, which was far from an inevitable outcome to that conflict. But every species larger than a cockroach which has lived prior to the K-T asteroid event has eventually faced extinction, and so long as we remain an earthbound species, we will as well.

Our government appears to be acutely aware of this. Even the eviscerated proposed NASA budget for 2012 includes funding for five things:

1) Maintaining the ISS as a crewed facility outside of earth's atmosphere,
2) Maintaining weather and climatological earth satellites,
3) Maintaining satellites to track Near Earth Orbit asteroids and comets,
4) Maintaining satellites searching for earth-like planets around nearby stars,
5) Developing heavy-lift capabilities to establish permanent colonies on the Moon and Mars.

Both the George W Bush and Barack H Obama administrations have ultimately made these five things their budgetary priorities for NASA. If Bush and Obama agree that these are our most important priorities, that's worth noticing.

The Moon and Mars are our best candidates for quick mass-migration, with arguments in favor of both but ultimately only Mars has enough water to sustain a very large human population. But, as has been previously discussed here, Mars and the Moon frankly suck as places for humans to live. So ultimately, for humans to survive as a species, we will need to migrate further. And we may not have the luxury of waiting a very long time to do so.

The meek shall inherit the Earth. With perseverance, the rest will inherit the stars. Between us, our species and our evolutionary descendants may survive a very long time.

Atomic Starships and other hobbies

I've been thinking a lot about DARPA's current study of Project Orion, the 1957 vintage atomic pulse powered starship. Funding to build it is a question, manpower and know-how to build it is a question. Orion has been sitting on a back launch-pad for 54 years for these and other considerations. We have the technology. We just need the budget.

The budget isn't small. The best estimates for Orion are somewhere around $25 billion, about the same as the entire Apollo program. As of this spring we will have 7 billion people on this planet. That's $3.57 a head, just under a penny a day for one year, before cost overruns.

There are, right now, collective building and restoration projects for all kinds of seagoing vessels, from sailing ships to WWII era military craft to submarines. These are being built, restored and sailed by volunteers. They're being funded by private donations and bake sales.

Devoting hundreds of hours of one's life to restoring an old sailing ship, or an old liberty ship, is hella cool. How much cooler would it be to spend that energy building a freaking starship?

Why wait for the government to find funding for Orion? Why not just get some interested people together and start building the damned thing? It would be slow, at first. But no slower than the pace at which it has already been built since 1957, which is no pace at all. Get someone like George Dyson (or hell, Richard Branson!) to manage the project, and then as funds are raised to build it bit by bit, build it bit by bit. Those who have a useful skill-set can donate a little time to the project as they can. There are lots of NASA and JPL alumni running around looking for work right now in the wake of the Constellation closings, maybe some of them would be interested. There's no special rush, let's just build it as well as we can and as fast as we can, and get on with it.

There used to be a bumper sticker which read "It will be a great day when our schools get all the money they need and the Air Force has to hold a bake sale to buy a bomber." To hell with governments. We, ourselves, can hold bake sales, car washes, benefit concerts and a whole lot more to raise revenue to build a ship which will travel to the nearest stars. If we roll up our sleeves, we can build this thing.

Pandora awaits.

DARPA keeping Project Orion in the air

Valentine's Day is few days past, but I'd like to talk for a moment about "love". Love is a strong word. It's an awfully strong word to apply to a governmental agency, especially one mostly devoted to finding new and creative ways to make those people over there be dead. Especially on the same week that I did my taxes. But right now, I think I love DARPA.

Because while NASA's new budget has left most of its deep-space exploration projects in ashes, DARPA is quietly continuing its work on the 100-Year Starship.

http://straitofmagellan.blogspot.com/2010/11/100-year-starship-project-orion.html
(Intended that to be a simple hotlink, but Blogspot is glitchy this morning.)

The Defense Advanced Research Projects Agency is the branch of the US Department of Defense who typically make all of the cool James Bond stuff for all four branches of the US military. They're a think tank whose only charter is radical innovation, and many of their innovations have had application far broader than the military (if you can read this post, thank DARPA). DARPA (ARPA at the time) was formed as a response to the Soviet launch of Sputnik, in hopes that the US would never again be out-technologied by anyone. Yes, I just made up that word.

So, DARPA just issued a press release for their first workshop of several throughout 2011 focusing on Project Orion, or whatever they happen to be calling it now. This is notable from the press release:

“We picked the 100-Year Starship name because it would require a long-range sustainable effort to get our species to other stars,” said (Dave Neyland, Director of DARPA’s Tactical Technology Office). “Looking at history, most significant exploration, like crossing oceans or continents for the first time, was sponsored by patrons or groups outside of government. We’re here because we’d like to start with a mechanism that gets this long-range project out of the government, and make sure it is an energized and self-sustaining enterprise.”

Read: This project is going to take a lot of time and a lot of money to accomplish, let's get it out from under the two-year electoral cycle and the one-year federal budget cycle or it's never going to be completed.

Bravo.

The press release continues:

Workshop members addressed a wide range of issues, such as why humans should visit the stars, the risks involved, the economic and socio-political-religious obstacles, and the type of governance structure needed. Other topics, such as the importance of having short-term achievable goals, identifying a destination for a 100-Year Starship, bringing together a core group of experts/enthusiasts, interest groups and private funding, and the continued importance of science and technical education for the youth of the world were also discussed at length.

I have some thoughts percolating on this, will be posting more later when they're better formulated. But I think this is a very good sign that we're moving ahead with Orion, cautiously. And that, friends, is a huge thing.

Here's the press release:

http://www.darpa.mil/news/2011/100YearStarshipWorkshopRelease.pdf