Sail Technologies Go Interplanetary

With its May 18 launch date fast approaching, Japan’s IKAROS hybrid sail mission is at last getting a bit of press attention, long overdue in my opinion. The Daily Mail, at least, has just run a story on IKAROS, which will combine two mission concepts within a single spacecraft. Its solar sail works conventionally, using the momentum of photons from the Sun to accelerate the craft. But the JAXA designers have added thin film solar cells on the sail membrane. These produce the electricity that could be used in future (and larger) iterations to drive an ion engine.

But IKAROS (Interplanetary Kite-craft Accelerated by Radiation of the Sun) is a demonstrator, not only taking the sail concept into space but pushing it into interplanetary regions. Launched in tandem with the Venus Climate Orbiter AKATSUKI, the spacecraft will deploy its sail a month after launch on the way to Venus, and having swung by the planet, will test out its propulsion and navigation systems. Kelvin Long, head of Project Icarus, was the first to forward me the link to the Daily Mail story, and that reminds me to note that despite the similarity in names, IKAROS bears no relation to the interstellar probe design Kelvin’s team is developing.

Not that the interstellar community doesn’t have high hopes for sail concepts, and it’s safe to say that anyone interested in the problems of deep space propulsion will rejoice at the launch of IKAROS. What we need at this juncture, with reams of theoretical work compiled, is to start gathering data from live missions. Perhaps the most obvious issue for IKAROS and any other design is sail deployment. The IKAROS sail is a square membrane with a diagonal distance of 20 meters, made of polyimide some 7.5 micrometers thick, with the solar cells, steering devices and dust-counter sensors fitted directly to the membrane.

Image: The IKAROS sail, a hybrid design with attached solar cells. Credit: JAXA.

Osamu Mori, project leader for IKAROS, describes the sail membrane in this interview:

Polyimide resin allows us to create a much lighter sail. As well as being extremely strong, it doesn’t need glue, because it can be joined using heat sealing. Polyimide resin is originally yellow, but one side of IKAROS’s sail is silver. This is because aluminum is vapor deposited on one side of the film, in order to reflect sunlight more efficiently. In addition, the film is reinforced in such a way as to prevent it from splitting all the way if it’s ripped. If the solar sail is torn, its performance will decline slightly, but it can still continue its space travels.

One way to deploy a sail is to use conventional mast and boom construction, but you pay a penalty in weight and complexity. The IKAROS team had a different idea. The sail, wrapped and folded around the body of the spacecraft, will be spun up to 20 revolutions per minute. Spinning the spacecraft will allow centrifugal forces to unfurl the sail, and spin-stabilization will likewise keep the weight down due to the lack of a supporting truss. JAXA’s sail team has conducted experiments both on the ground and aboard a balloon, where the sail membrane was spread in a near-vacuum.

Mori adds that sail orientation and navigation is going to prove an interesting issue. IKAROS could change the direction of the sail with an onboard thruster but can also maneuver solely with solar power, changing the reflectivity of various parts of the sail by ‘frosting’ the film. The part of the sail with reduced reflectivity thus generates less acceleration, so the sail’s attitude can be controlled. In addition, IKAROS will carry a dust counter and an instrument to observe gamma ray bursts.

Japan’s plans for the hybrid sail/cell design are quite ambitious. JAXA’s Jupiter and Trojan Asteroids Exploration Program was born in 2003 and chose solar sail technologies for the mission. IKAROS is thus a demonstrator not only for sail concepts in general but for the specific issues that a Jupiter mission will face. At 5 AU, a sail in Jupiter space receives only 4 percent of the amount of sunlight it would in Earth orbit, drastically reducing the effectiveness of a conventional sail. This is the reason for the solar cell experiment, which would drive an ion engine needed for maneuvering a larger Jupiter-bound sail.

But first things first. The IKAROS demonstrator will need to prove itself in terms of deployment, navigation, attitude control and power generating capabilities, teaching us whether future hybrid designs using ion propulsion are indeed feasible. We’ll begin to learn more on May 18, when IKAROS and AKATSUKI blast off from the Tanegashima Space Center.


Astrobiology in Houston: From Fossils to SETI

NASA’s teleconference from the Astrobiology Science Conference 2010 in Houston offered some interesting news about the discovery of microscopic fossils in gypsum from a period about six million years ago, when the Mediterranean Sea had all but dried up. Gypsum (calcium sulfate) precipitates out of sea water, and the find has implications for finding life on Mars, as I’ll explain in a moment.

What gave me a chuckle, though, was that after a discussion between four crack astrobiologists about life’s appearance on Earth and the best ways to search for it elsewhere, the first question from reporters was about Stephen Hawking’s views on aliens, and whether NASA had a policy on broadcasts to the stars.

The answer is clearly no, and NASA’s Mary Voytek noted the differences of opinion between the agency’s scientists on the issue, prompting Steven Squyres (of Mars rover fame) to note that our signals are already in play in the form of TV broadcasts and planetary radar signals. I’m thinking that Bill Schopf, who introduced the micro-fossil research, must have been bemused at having his work so quickly trumped. But Schopf (UCLA) and Jack Farmer (Arizona State) are onto something with implications for future sample return missions from Mars, so let’s put Hawking and aliens aside.

Micro-Fossils and Mars

It turns out that little work has been done with fossils preserved in gypsum because, as Schopf said, most scientists assumed that sulfate deposits undergo sedimentary changes that, as with carbonates, would crush such tiny fossils, which is why you don’t, for example, find micro-fossils preserved in limestone on Earth. But it turns out that Schopf and Farmer have found fossils in numerous deposits of gypsum. And the interesting follow-on is that Mars has huge areas at the north pole and the equatorial region near Valles Marineris where gypsum is common. The Opportunity rover, as a matter of fact, landed on a sulfate deposit.

Now that we know that a biosignature can be preserved in sulfates, we can think about mission implications. For gypsum is soft enough to trench with the robotic arm of a rover. It’s also soluble in water. Dissolve away the mineral material and you just might find clumps of organic material and perhaps fossils, all of which was fodder for Steve Squyres’ later discussion of a sequence of three Mars missions, incorporating a rover to collect samples, a lander that would pick them up, and an orbiter that would recover the samples and return the package to the Earth.

Asteroid Ice and Organics

Likewise of astrobiological note (and discussed briefly in the teleconference) were the new papers on the infrared spectra of the main-belt asteroid 24 Themis, which show a frosty coating of water ice and organics on the object. The ice was an unusual find, for at this distance (roughly 480 million kilometers from the Sun), ice is not stable and needs to be replenished. Themis is about 200 kilometers in diameter and it’s possible that replenishment is coming from within, which reminds us of scenarios in which incoming objects brought water to the early Earth.

This BBC story on the asteroid find quotes Andy Rivkin (Johns Hopkins) on the matter:

“Finding ice in Themis and the Themis family opens up the possibility that you might have brought in water from asteroids as well as comets; and that potentially allows a lot more water to be brought in and it also allows the isotopic compositions to work out the way we need them to, to match the Earth.”

That last reference is to the fact that Earth water does not match well with comets as the single origin. Adding icy asteroids to the mix could resolve the complication. For more on this, see Campins et al., “Water ice and organics on the surface of the asteroid 24 Themis,” Nature 464 (29 April 2010), pp. 1320-1321 (abstract) and Rivkin and Emery, “Detection of ice and organics on an asteroidal surface,” Nature 464 (29 April 2010), pp. 1322-1323 (abstract).

SETI Takes the Stage

The Astrobiology Science Conference ends today with morning sessions on biosignatures and the quest for life on Mars. Two SETI sessions have been held to the afternoon, the final one much in the spirit of the Hawking debate that has been raging on the Net all this week. That session is titled “Global Engagement and Interstellar Message Construction.” Chaired by Frank Drake and Douglas Vakoch, it goes into the intricacies of communication between intelligent beings of entirely different evolutionary and cognitive histories. It’s good to see that Jim and Gregory Benford will be discussing their ideas on cost-optimized interstellar beacons — much debated in these pages — in the earlier SETI session. Check the AbSciCon2010 site for abstracts.

Claudio Maccone also called yesterday from Houston. He’s at AbSciCon 2010 with poster presentations on the uses of the Karhunen-Loève Transform in SETI, especially as they relate to fast-moving sources, and our ability to use the KLT in future space communications with our own probes. Maccone’s idea of a ‘radio bridge’ using the gravitational lenses of both the Sun and Alpha Centauri — enabling interstellar communications with no more power than a cell phone — should play well to this audience. For more on the KLT, see this earlier post, and check here for the radio bridge.


Notes & Queries 4/28/10

Solar Sail Symposium in July

The 2nd International Symposium on Solar Sailing (ISSS 2010) draws closer, the event occurring July 20-22 at New York City College of Technology of the City University of New York. The focus will be on recent advances in solar sailing technologies and near-term solar sailing missions, with coverage of hardware, enabling technologies, concepts, designs, dynamics, navigation, control, modeling and mission applications and programs. The deadline for abstracts is May 15, 2010, with full information available at the symposium’s Web site.

Image: The IKAROS hybrid sail concept. A solar sail gathers sunlight as propulsion by means of a large membrane while a solar “power” sail gets electricity from thin film solar cells on the membrane in addition to acceleration by solar radiation. What’s more, if the ion-propulsion engines with high specific impulse are driven by such solar cells, it can become a “hybrid” engine that is combined with photon acceleration to realize fuel-effective and flexible missions. Credit: JAXA.

Given that CUNY is the home turf of solar sail experts Greg Matloff and Roman Kezerashvili, the conference should become the epicenter for current analysis of these technologies. The major space agencies are strapped for cash, but a robust solar sail literature continues to flourish and interesting mission concepts are under development at the Japanese space agency JAXA, where a demonstrator hybrid solar sail/solar cell mission is being readied for launch on May 18, and at The Planetary Society, whose LightSail-1 may fly later this year.

Surviving Technological Adolescence

I love Philip Morrison’s statement that ‘SETI is the archaeology of the future,’ quoted by Jill Tarter in a recent opinion piece on CNN. Archaeology is all about the past, and the targeted beacon we might detect from a civilization a thousand light years away would have information about its past, not its present state. So while the information would not be up to date, it would be deeply informative, telling us by example that at least one civilization had lived long enough to survive the danger of self-destruction by means of its own technology, or at least long enough to send the signal.

The longevity of a technological civilization is the crucial factor in so much of this discussion. Give it a high value and the chances are that any civilization we encounter will be older than our own. That concerned Stephen Hawking enough to worry about what a powerful, nomadic culture might do to a life-bearing world it encountered. The other side of the coin is what Tarter suggests, that longevity brings with it a measure of wisdom. Suppose we make not just electromagnetic contact but actually encounter an alien culture in our own system:

Well, one thing is for sure: If they can get here, then their technology is superior to ours, and not just by a little! Arthur C. Clarke’s third law is, “Any sufficiently advanced technology will be indistinguishable from magic.”

Can we be certain that their magic would do us harm? I would hope that Hawking would agree that a large value for L (a requirement for that magical, star-spanning technology) could also mean that their distant civilization had found a way to stabilize itself in order to survive and grow old. That might require outgrowing any aggressive and belligerent tendencies that may have characterized their youth.

Paul Davies makes much the same case in an essay this morning via the Wall Street Journal, although Davies is more emphatic:

…suppose by some fluke aliens did come to visit Earth in the near future, then comparisons with Columbus are in any case wide of the mark, and reflect the rampant anthropocentrism that pervades much speculation about alien life. Just because we go around wiping out our competitors doesn’t mean aliens would do the same. A civilization that has endured for millions of years would have overcome any aggressive tendencies, and may well have genetically engineered its species for harmonious living. Any truly bellicose alien species would either have wiped itself out long ago, or already taken over the galaxy.

I prefer Jill Tarter’s approach, which notes that an advanced society might have to outgrow its aggressive tendencies to survive. Davies takes that conjecture and elevates it to a principle: “A civilization that has endured for millions of years would have overcome any aggressive tendencies…” Perhaps. But we’ve never encountered such a civilization, and have no way of knowing how it would behave.

Tarter is careful to note that the SETI Institute isn’t involved in broadcasting messages, but in listening to the universe to learn what might be out there, adding “If signals are detected, everyone on the planet should have a voice in deciding how to respond.” That assumes, of course, that we pick up a targeted transmission rather than extraneous signals from a civilization merely going about its business. The latter case still leaves the question open: Inform another intelligent species of our existence, or continue to listen and learn?

A Wanderer in the Oort Cloud?

How to explain odd, detached Kuiper Belt objects like Sedna? One way is through a large object perturbing the Oort Cloud, a possibility examined in a new paper by John Matese and Daniel Whitmire (University of Louisiana at Lafayette). The duo have been working for some years now on comet dynamics, in particular on the orbital parameters of ‘new’ Oort cloud comets, ‘new’ being understood as first-time entrants into the inner planetary region. It turns out an anomalous pattern exists here that can be explained by an Oort Cloud giant planet.

Because we have no detection from IRAS or 2MASS data, we can place a limit on the possible mass and present distance of this object. If it exists, the world the authors call Tyche (the good sister of Nemesis) is between one and four Jupiter masses and orbits in the innermost region of the outer Oort Cloud. The optimum wavelength for detecting the putative planet is in the 5-micron region, well within the limits of the WISE infrared survey, and the new paper suggests just where WISE might look.

The paper, submitted to Icarus, is Matese and Whitmire, “Persistent Evidence of a Jovian Mass Solar Companion in the Oort Cloud” (preprint).


GJ 436b: Mystery and Its Uses

Yesterday’s musings on extraterrestrial contact were inspired both by Stephen Hawking and the surrealist painter Giorgio de Chirico (1888-1978). Whereas Hawking opined that an encounter with an alien culture could be dangerous, my own hunch was that it would be deeply mysterious and perhaps not even understood as contact, given the huge differences in technology between us. That called De Chirico’s strange cityscapes to mind, what Walter Wells calls ‘their deep and often irrational shadows, their empty walkways and portentous silences.’

It helped, of course, that years ago I had reviewed V.S. Naipaul’s The Enigma of Arrival, which draws heavily on the De Chirico painting of the same name (shown above). Naipaul’s book is a strange, autobiographical meditation whose subject is consciousness confronted with mystery. He imagines one of the two figures in the painting as a traveler and conceives a story based on the scene, one set in what he calls a ‘dangerous classical city,’ but he soon becomes caught up in autobiographical introspection and The Enigma of Arrival turns into an exercise in self-indulgence.

Too bad, because Naipaul at his best is a great writer. Even so, both the De Chirico painting and Naipaul’s treatment of it stayed with me, and it has often occurred to me that our scientific ‘arrivals’ can in their own way be just as enigmatic. A case in point: Last week we learned that the Spitzer Space Telescope, in its studies of the Neptune-sized planet GJ 436b, had performed an analysis of the distant world’s atmosphere. The result was unusual. GJ 436b should, by our current theories, show the clear signature of methane in its atmosphere. In fact, an atmospheric mix of hydrogen, carbon and oxygen in a temperature range up to 1000 Kelvin (726 degrees Celsius) should feature just tiny amounts of carbon monoxide and a large supply of methane.

But GJ 436b gives us just the opposite. Spitzer can detect its carbon monoxide but finds a clear deficiency of methane. In fact, the amount of methane here is 105 times less than predicted for a planet in thermochemical equilibrium. H2O is also present, as is CO2 in trace amounts. The technique, using the secondary eclipse as the planet moves behind its star as seen from Earth, has been proven sound and used on several ‘hot Jupiters.’ Spitzer worked with six infrared wavelengths and simply didn’t come up with what was expected. Joseph Harrington (University of Central Florida) is principal investigator on this work:

“In this case, we expected to find methane not because of the presence of life, but because of the planet’s chemistry. This type of planet should have cooked up methane. It’s like dipping bread into beaten eggs, frying it, and getting oatmeal in the end.”

Not a satisfying result in one sense, but of course from the scientific perspective, unusual results are all the more fascinating because they challenge us to improve our theories. GJ 436b is located in the constellation Leo some 33 light years away, orbiting an M-dwarf in a 2.64 day orbit. And while we figure out how to account for this planet’s atmosphere, we can also look forward with excitement to the extension of these techniques to smaller and cooler worlds, rocky planets not that much bigger than the Earth that could conceivably house life.

De Chirico’s art is all about showing life’s mystery and dwelling upon our aesthetic response. Science, on the other hand, uncovers mysteries like that of GJ 436b, but its aim is to resolve the tension they create by adjusting our models to fit incoming data. Good scientists rejoice in mystery even as they set about understanding it, much as the reader of suspense novels turns pages in anticipation of untangling the plot. What new enigmas may turn up when we have the ability to detect biomarkers on Earth-class worlds? And who will be the new De Chirico to capture the scene?

The paper is Stevenson et al., “Possible thermochemical disequilibrium in the atmosphere of the exoplanet GJ 436b,” Nature 464 (22 April 2010), pp. 1161-1164 (abstract).


The Enigma of Contact

What Stephen Hawking thinks about aliens made news this weekend, and Centauri Dreams readers will know from our past discussions more or less what Hawking has to say. Assuming we come into contact with an extraterrestrial civilization, it is widely assumed that one of two things will happen. Either an alien visit will be devastating, as has all too often happened when cultures with widely different technologies met, or a benign transfer of information will occur, in which case we benefit by our exposure to new science and revolutionary ideas.

A Threat to Humanity?

Hawking, who has been working on an upcoming program for the Discovery Channel, opts for the former, as this story in TimesOnline notes. Most life elsewhere in the universe, the physicist believes, will be relatively simple, microbial or primitive animals. But there will be exceptions:

…a few life forms could be intelligent and pose a threat. Hawking believes that contact with such a species could be devastating for humanity.

He suggests that aliens might simply raid Earth for its resources and then move on: “We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet. I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonise whatever planets they can reach.”

Historical analogies are inevitable:

[Hawking] concludes that trying to make contact with alien races is “a little too risky”. He said: “If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans.”

Ambiguity and Recognition

We’ve argued this point of view and its opposite many times in these pages. My own belief is that contact with an advanced culture would be something different than either of the above alternatives. Assume a wide enough disparity in our capabilities and the problem will be knowing when an encounter has actually taken place. Indeed, just as a civilization a million years in advance of our own (and we should ponder exactly what ‘in advance’ means) might have no real interest in us, we for our part might not even be able to recognize them.

One of many possible examples: Suppose our inability to find magnetic monopoles is actually a marker for intelligent activity. The problem with magnets is that they’re always dipoles, north pole at one end and south at the other. A magnetic monopole is an isolated ‘north’ or an isolated ‘south,’ and there’s precedent for this in the fact that electric charges come as monopoles. There’s a rather robust literature about magnetic monopoles but the problem is that nobody can find them, despite a false alarm back in the early 1980s.

We believe that magnetic monopoles should have been created in the early universe, and one notion about where they’ve gone is that a period of cosmic inflation spaced an abundant population of monopoles so widely that finding even one would be all but impossible. But maybe that theory is wrong. A sufficient number of ‘north’ monopoles encountering their ‘south’ monopole counterparts would create vast amounts of energy. So what if, as Paul Davies speculates in The Eerie Silence, the lack of monopoles tells us something:

Theoretical physicists are masters at predicting things that might exist, but don’t seem to be there. Exotic subatomic particles with whimsical names such as neutralinos, shadow matter and axions grace the theorists’ lexicon, but haven’t yet shown up in the lab. At the other end of the mass range are mini-black holes, quark stars and cosmic texture, to name but a few. Did ET make off with them? Clearly, extreme caution is needed before considering alien culpability.

Extreme caution indeed, and no one is seriously suggesting this is the case. In fact, even as Davies goes through a set of scenarios for viewing possible extraterrestrial activity — his point being to ask whether we would know it when we found it — he’s quick to add this:

Remember Bayes’ rule: the hypothesis that aliens are the correct explanation for the anomalous absence of something is only as good as the prior probability of an alien super-civilization in the first place. That may be very low. By contrast, the prior probability that Professor A’s theory of the so-and-so particle, or Dr B’s prediction of such-and-such an astronomical object, is simply wrong could be a lot higher.

But if we’re willing to go to this speculative extreme, it seems worth saying that a civilization that evolved aeons after a Kardashev Type II-scale engineering project had depleted local resources might not be able to tell that it was living among the debris of a neighborhood that had been effectively ‘mined out’ of materials that would have proven of use to the former super-civilization.

The Real Encyclopedia Galactica

My guess is that if there are other civilizations in the galaxy at the present time and if we at some point do encounter them, we’ll have a lot of trouble figuring out what they’re after, where they’re going, or what their motives are. Let’s hope such an encounter would be benign enough for us to learn, ponder and muse about the unfathomability of intelligence that has evolved elsewhere. Maybe we would be able to communicate enough to acquire deep knowledge, but I suspect the idea that there is an Encyclopedia Galactica out there to be studied is a chimera. The real Encyclopedia Galactica is more likely to be the one we build with science, one whose entries we refine with new observation and experiment.

A 2002 Roper poll taken in the US found that most Americans are ‘comfortable with and even excited about’ the discovery of an extraterrestrial culture. If the poll is accurate, Hawking’s ideas will probably strike most of its respondents as alarmist in tone, and reminiscent of a particular kind of bad science fiction movie. The problem is that we have only one example to work with, our own. We can see what has happened in the history of our species to cultures that have met superior technologies, but when it comes to encounters with entirely different beings, we have no template to fall back upon.

That leaves us guessing, a pleasurable human activity that is a long way from science. I think alien nomads in massive starships are a lot less likely than alien bacteria, but we press on with the search for both kinds of life and anything that may exist in between. Meanwhile, I’ll watch Hawking’s program with pleasure. The man is a titan. He has paid his dues and continues to expand the way we look at the universe, and the last thing I would do is take his views lightly.