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On the Nuclear Imperative

by Paul Gilster | Jul 31, 2009 | Advanced Rocketry | 39 Comments

Sometimes our concerns about the human future are eerily like those of our ancestors. Giancarlo Genta (Politecnico di Torino) likes to quote an ancient Assyrian tablet on the matter, one said to have been rendered around 2800 BC: Our Earth is degenerate in these latter days; bribery and corruption are common; children no longer obey their parents; every man wants to write a book and the end of the world is evidently approaching. Marvelous as it is, the quote may be apocryphal, as Genta noted in his recent talk at the deep space conference in Aosta. In fact, I suspect it is, unless the bit about every man wanting to write a book was literally written 'every man wants to keep his household accounts on a clay tablet' or some such. But whatever the case, the quote echoes similar sentiments found throughout history, thoughts that evoke a golden age when things were just plain better than they are in the present and the future did not seem so dark. Which is not to say we don't have serious...

Cometary Catastrophe? Not So Fast…

by Paul Gilster | Jul 30, 2009 | Asteroid and Comet Deflection | 14 Comments

Once again we're asked to reconsider our views about the outer Solar System. In this case, the area in question is the Oort Cloud, which begins at roughly 1000 AU and continues, by some estimates, as far as three light years from the Sun. It's a spherical cloud of comets, probably numbering in the billions of objects, most of which will never be observed because of their distance and faint signature. Getting comets into the inner Solar System is necessary for closer observation, but it's also risky for living beings. At least, that's been the prevailing belief, given that comet collisions with Earth could theoretically produce extinction events. New research, however, has begun to challenge this view. Nathan Kaib (University of Washington) and doctoral adviser Thomas Quinn have developed computer models to study how comet clouds behave. The simulations trace the evolution of comets over a 1.2 billion year period and allow the team to estimate the highest number of comets possible in...

Enceladus: More Evidence of Liquid Water

by Paul Gilster | Jul 29, 2009 | Outer Solar System | 13 Comments

I'm pushed for time this morning but do want to catch up with Cassini news, in particular the recent findings from Enceladus. The plumes of water vapor and ice particles erupting from the moon continue to capture the imagination. Cassini's Ion and Neutral Mass Spectrometer was used during Enceladus flybys in July and October of 2008, with results just released in Nature. Out of all this we get this interesting find, as discussed by Hunter Waite (SwRI), who is lead scientist on the instrument involved: "When Cassini flew through the plume erupting from Enceladus on October 8 of last year, our spectrometer was able to sniff out many complex chemicals, including organic ones, in the vapor and icy particles. One of the chemicals definitively identified was ammonia." William McKinnon (Washington University, St. Louis) calls ammonia "sort of a holy grail for icy volcanism," noting that this is our first unambiguous detection of ammonia on an icy satellite of a giant planet. Finding it is...

Notes & Queries 7/27/09

by Paul Gilster | Jul 28, 2009 | Culture and Society | 4 Comments

Tau Zero in the Press Edinburgh-based journalist Ian Brown offers up an overview of interstellar issues in Scotland's Sunday Herald. The core of the story is an interview Brown conducted with Tau Zero founder Marc Millis, who as Brown notes was formerly the manager of NASA's Breakthrough Propulsion Physics project. The Tau Zero Foundation grows out of that work (though it retains no NASA connection), and it's good to see us getting publicity in a popular science story that captures TZF's imaginative spirit while avoiding sensationalism. Brown calls us "a grass-roots network of physicists, mathematicians, engineers and science journalists," an accurate description. Here's a snippet quoting Millis on the nature of interstellar striving: "How much we accomplish is, of course, tied to the resources we acquire. The focus will be on making incremental progress rather than big projects." As a physicist, he knows the sheer immensity of the challenge. Many scientists believe we will never...

Galactic Life in Context

by Paul Gilster | Jul 27, 2009 | Astrobiology and SETI | 35 Comments

Does complex life emerge at a gradual, uniform rate? If so, we can come up with one answer to the Fermi paradox: We have not detected signs of extraterrestrial life because the time needed for complex life to appear generally exceeds the life of a star on the main sequence. But the assumption that intelligence appears over time with a gradual inevitability -- a key tenet of work by Brandon Carter, Frank Tipler and others in the 1980s, may not in fact be true. Solar system-wide events connect life with its stellar environment, while galaxy-wide events provide yet another context. Punctuated Evolution Among the Stars Milan ?irkovi? (Astronomical Observatory, Belgrade) and colleagues have much to say about this in a new paper in Astrobiology. It's a rich treatment of our older assumptions and newer thinking about punctuated evolution, the idea that life actually evolves in spasms rather than smooth ascents. Species remain relatively stable for long periods but endure sudden changes that...

Updating the Gravitational Focus Mission

by Paul Gilster | Jul 24, 2009 | Outer Solar System | 23 Comments

If you'll examine the cover of Claudio Maccone's new book carefully, you'll see an interesting object at the lower right. It's a spacecraft with two deployed antennae connected by a tether. The book is Maccone's Deep Space Flight and Communications, whose subtitle -- 'Exploiting the Sun as a Gravitational Lens' -- tells us much about the author's view of how early interstellar missions should proceed. And Maccone devoted a session at the recent conference in Aosta to these matters, making the case for taking advantage of this natural phenomenon. Uses of Gravitational Lensing We've looked at the Sun's gravitational lens, and the FOCAL mission Maccone champions to exploit it, many times here on Centauri Dreams. But for newcomers, gravitational focusing has been an active astronomical tool since 1978, when a 'twin' image of a quasar was found by the British astronomer Dennis Walsh. The gravitational field of a galaxy between the Earth and the quasar had bent the light from the more...

Habitable Exomoons Should Be Detectable

by Paul Gilster | Jul 23, 2009 | Exoplanetary Science | 15 Comments

The hunt for exomoons -- satellites of planets around other stars -- gets more interesting all the time. This morning I received a note from David Kipping (University College London), who has been studying methods for finding such objects. Kipping and colleagues have a paper soon to be published by Monthly Notices of the Royal Astronomical Society that discusses how to detect habitable exomoons using Kepler-class instrumentation. And it turns out that finding such worlds is well within our present capabilities. A bit of background: Kipping's method is to analyze two useful sets of signals. Transit timing variations (TTV) are variations in the time it takes a planet to transit its star. Kipping and team acquire these data and then weave the TTV information together with what is called transit duration variation (TDV). The latter is detectable because as the planet and its moon orbit their common center of mass, velocity changes can be observed over time. Put TTV and TDV together and...

A New Jovian Impact

by Paul Gilster | Jul 22, 2009 | Asteroid and Comet Deflection | 12 Comments

It's a lively Solar System indeed. In yet another confirmation of the value of amateur astronomy, Australia's Anthony Wesley tipped off scientists on July 19 that a new object had struck Jupiter and observatories around the world zeroed in on the event. It comes exactly fifteen years after the 'string of pearls' comet Shoemaker-Levy 9 struck the giant planet. Infrared images show a likely impact point near the south polar region, visible in the image below. Image: A large impact shown on the bottom left on Jupiter's south polar region captured on July 20, 2009, by NASA's Infrared Telescope Facility in Mauna Kea, Hawaii. Image credit: NASA/JPL/Infrared Telescope Facility. Unlike Shoemaker-Levy 9, this event may have been caused by a single object. UC Berkeley and SETI Institute astronomer Franck Marchis explains: "The analysis of the shape and brightness of the feature will help in determining the energy and the origin of the impactor. We don't see other bright features along the same...

Chinese Test of Eclipse Anomaly

by Paul Gilster | Jul 21, 2009 | Exotic Physics | 11 Comments

Tibor Pacher has been kind enough to publish the text of my public lecture in Aosta, Italy on his PI Club site. The lecture took place at the Aosta town hall and wasn't part of the ongoing conference just down the street, although some conference participants attended. It's a broad overview of earlier work on interstellar flight. My intention was to acquaint non-scientists with the fact that the subject has been under study for decades in ways that do not violate the laws of known physics. A major challenge is how to scale some of the colossal engineering involved down to realistic levels. Although I only touched upon it in the lecture, I often talk about the twin tracks of interstellar studies. The first track comprises work that tries to scale current technology up for an interstellar mission. The second track is oriented toward examining physical laws in hopes of finding potential breakthroughs that current theory doesn't allow. No one knows if such breakthroughs are possible, but...

On Apollo 11

by Paul Gilster | Jul 20, 2009 | Culture and Society | 37 Comments

I sometimes wonder whether Neil Armstrong wrestled all the way to the Moon with what he would say when he stepped out onto the surface. The answer is probably tucked away somewhere in the abundant literature on the Moon landings. I know that if it were me, I'd be turning over the options in my mind for months in advance. What do you say upon achieving what is obviously one of the most significant accomplishments in history? Did Armstrong ponder alternatives even as he descended from the lander? In any case, the words carried a great truth. Giant leaps are made up of small steps, and not just the first step of a single astronaut leaving a footprint. It wasn't just a Saturn V that got Apollo 11 to the Moon -- it was also Einstein, and Newton, and Leibniz, and thousands of mathematicians, physicists, engineers and yes, philosophers throughout history whose work pushed the possibility forward. This is, not coincidentally, the philosophy of the Tau Zero Foundation: ad astra incrementis....

Reconfiguring the Early Solar System

by Paul Gilster | Jul 17, 2009 | Outer Solar System | 7 Comments

Other than Monday, the week here has been devoted to the outer planets, and before I leave that subject, I want to work in the findings of a team of astronomers looking at the early history of the asteroid belt. Recent numerical simulations suggest that many of the objects found in the 'main belt' between the orbits of Mars and Jupiter actually formed far out in the Solar System, moving inward during a violent spasm of planetary evolution. That points to an early system that, at particular times, underwent upheaval caused by a rearrangement of the gas giant planets. This is the so-called Nice model, so named because much of the work on it was performed at the Observatoire de la Côte d'Azur in Nice. The model proposes that the gas giant planets migrated to their present positions long after the protoplanetary gas disk had dissipated, playing a role in the Late Heavy Bombardment of the inner planets some 3.9 billion years ago, and producing many other effects, including the formation...

Cryovolcanism on Charon?

by Paul Gilster | Jul 16, 2009 | Outer Solar System | 5 Comments

Gentry Lee (Jet Propulsion Laboratory) discusses the question of extraterrestrial life on a program called Are We Alone, which airs this evening on the Discovery Channel at 2100 EDT (0100 UTC on the 17th). Lee is chief engineer for the Solar System Exploration Directorate at the Jet Propulsion Laboratory, a veteran of Viking and Galileo, and a co-author of Arthur C. Clarke. He was also involved with Carl Sagan on COSMOS, so he knows something about video productions. Pushing Back Astrobiology As I've noted in the two previous posts, we're moving into an era of re-examination of the Solar System. It's one that leads inevitably to a new understanding of the concept of habitable zones, with life now being considered a possibility on places that were once thought off-limits. Europa is unusual enough, but the evidence for that ocean beneath the ice is persuasive. Can we extend the paradigm all the way out to the Kuiper Belt? If so, missions like the Haumea orbiter or probes to other...

Haumea: Technique and Rationale

by Paul Gilster | Jul 15, 2009 | Outer Solar System | 11 Comments

Yesterday's look at a fast orbiter mission to Haumea raises useful questions. The mission, developed conceptually by Thales Alenia Space and presented at Aosta by Joel Poncy, is particularly demanding because this outer system object has no atmosphere. You can make the case for a Neptune orbiter with associated study of Triton, as several readers have already done, but if you want to orbit Haumea, no aerobraking is possible to ease orbital insertion. The Haumea mission, in other words, deliberately pushes the state of the art in both propulsion and power generation. Poncy noted in his talk at the Hotel Europe that his team had adapted an in-house software model to optimize the propulsion possibilities. The team considered only electric or magneto-plasma technologies (for the latter, think VASIMR -- Variable Specific Impulse Magnetoplasma Rocket). They assume a direct trajectory to Haumea with arrival around 2035, when the object is at 49 AU, and they weigh the benefits of a gravity...

Fast Orbiter to Haumea

by Paul Gilster | Jul 14, 2009 | Outer Solar System | 16 Comments

One of the surprises of the Aosta conference was Joel Poncy's presentation on a fast orbiter mission to Haumea. Poncy (Thales Alenia Space, France) and colleagues have been developing ideas for the extraordinarily difficult challenge of not just sending a probe to the outer system, but slowing it down for orbital capture. It's one thing to do this, say, for Neptune, where a thick atmosphere can be used for aerobraking, but it's quite another to contemplate doing the same for an airless trans-Neptunian object (TNO) like Haumea. Nonetheless, there are solid reasons for thinking about such a mission. The first is purely scientific. As Poncy did, I'll use outer planet specialist Mike Brown's illustrations of what has happened to our Solar System in the last few decades. The first illustration shows the Solar System most of us grew up with, a system with nine planets that were more or less clearly defined, with what was assumed to be a certain amount of debris and cometary material...

Back from Italy, We Turn to Nanotech

by Paul Gilster | Jul 13, 2009 | Advanced Rocketry | 8 Comments

One of the things that makes travel both entertaining and exasperating is the assurance that the best laid plans will come up against events beyond your control. Thus I arrived at Milan's Malpensa airport in plenty of time for my Delta flight, only to be told that the flight had been canceled. But Delta moved quickly on setting me up with an Alitalia flight to New York that left only thirty minutes after the first had been scheduled to leave, and after two more connections (and a twenty-three hour day on the move) I arrived back home. The photo is a shot of the streets of Aosta one early morning, from a walk I took on the last day to remember it by. I returned with a satchel full of notes, the conference proceedings, numerous business cards and the world's worst back-ache, a consequence of trying to move too fast in crowded airports with laptop and luggage. While the latter heals, I've also decided not to try to move through the Aosta material in one go -- there's too much of it, and...

A Milanese Morning (with NEOs)

by Paul Gilster | Jul 10, 2009 | Asteroid and Comet Deflection | 4 Comments

The driver who took me from Aosta to Milan yesterday evening spoke no English, but he was an affable young man who had a love for fast cars. As we drove along a fine Alpine highway, a low red sports car moved fast us so quickly that I almost didn't see it. But suddenly the driver, who had said next to nothing thus far, erupted with "Italian car! Beautiful!" He stretched out the last word as if savoring the idea, then looked over at me making a thumbs up. Well, it was beautiful, and it was followed by two more similar cars making speeds I could only guess at. I wondered what it felt like to drive such a car, and how quickly it would get to Milan. One of the best things about wrapping up the Aosta conference, which we did with a farewell party yesterday afternoon, is that I head back to the States with a satchel full of papers. I've only been able to mention a few of them thus far, but next week I should have the chance to talk about them at more leisure. Here in Milan I have a few...

Aosta Update for Thursday

by Paul Gilster | Jul 9, 2009 | Culture and Society | 2 Comments

I'm just in from an early morning walk around the streets of Aosta, enjoying a brisk spring morning. The streets at this hour are largely empty and the Sun lights the nearby peaks. We have a heavy session of papers on this last day of the conference, and we had an even longer day yesterday, followed by my public lecture at the Aosta town hall last night. Following the talk, Giancarlo Genta, his lovely wife Franca, and Guido Cossard, the assessore of cultural affairs (who turns out to be an astronomy buff and something of an expert on archaeoastronomy), took me on a walk around town looking at medieval and Roman sites. We wound up having a late night beer and I didn't get in until 1:30. This is a travel day, as I change hotels in preparation for tomorrow's flight from Milan. So I'm going to hold any of the discussion about the papers yesterday, which were so rich that I'd prefer to get into them when I have more than a few minutes. In particular, the solar sail sessions opened my eyes...

Aosta Update for Wednesday

by Paul Gilster | Jul 8, 2009 | Culture and Society | 15 Comments

Today we get into the heart of this interstellar conference, with multiple sessions on propulsion via solar and electric sail, as well as looks at specific mission concepts and robotic applications in deep space. I spent a good part of our bus ride back from Bard castle yesterday talking to Pekka Janhunen, creator of the electric sail concept, about its possible interstellar applications. Pekka does not believe this system, based on electric tethers riding the solar wind, could muster the velocity to go interstellar, but he does see it as a viable candidate for braking into a destination system, and just as important, exploring it. I'm anxious to get the latest on his work and also to look at fusion alternatives, which Claudio Maccone will present now that we've learned that Claudio Bruno can't make it here. As I get ready for the day to start, I'll drop in here some notes from the first day. These are no more than a skeletal outline -- I'll use the conference proceedings when I get...

Busy Times in Northern Italy

by Paul Gilster | Jul 7, 2009 | Culture and Society | 4 Comments

I had intended to use today's post to talk about yesterday's sessions here in Aosta, but it's going on midnight here, and tomorrow will clearly not afford any opportunities to write. Tuesday turns out to be our sightseeing day. We leave the hotel at 9:00 and head for Verrès, where we visit the Mechatronics Laboratory of the Politecnico di Torino. Then we head up into the mountains, visiting the Bard fortress, with individual visits to the Museum of the Alps. After lunch at what is said to be an excellent restaurant called La Polveriera, we go to an exhibition called 'Verso l'alto, l'ascesa come esperienza del sacro' -- Towards the heights: The ascent as experience of the sacred. Then to dinner at the Hotel Notre Maison, where we are promised traditional Aosta Valley food. Image: The Aosta town hall, where our opening sessions were held. Later, we moved to the Hotel Europe. As for tomorrow, we don't get back to the hotel until midnight. No more today or I'll be late for the bus, but...

First Day in Aosta

by Paul Gilster | Jul 6, 2009 | Culture and Society | 2 Comments

What I'll surely remember the most about arriving in Italy is the sight of snow on the Alps as the plane descended out of a cloudy morning sky into Milan. But right after that comes the two hang gliders that soared past an alpine peak as the van that was taking me to Aosta moved north toward the town, the landscape becoming a series of valleys cutting through the steep clefts. The second of the two hang gliders looked for all the world as if it were going to land right on the highway, a daunting thought given how the traffic was moving, but as we rounded a turn I saw that it had caught an updraft and was angling out and away. What a view the pilot must have had. Image: The view from my room at the Hotel Europe in Aosta. It was hot and humid when I took this, but cooled off dramatically during the night. If the air conditioner worked, all would be perfect. Below is a photo from the street in front of the hotel. As you can tell, this is the place to be for a guy who loves mountains the...

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In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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