by Paul Gilster | Oct 10, 2011 | Culture and Society |
I’ve got an out of town speaking gig today and am pressed for time, so this may be a good occasion for something I needed to do anyway for the record, which is to highlight the papers given by Tau Zero Foundation and Project Icarus people at the recent 100 Year Starship Symposium. Most of the following were delivered as individual talks, although some were presented in panels. If you’re interested in reading the papers each author prepared for the conference, many (but not all, evidently) are to be published in the Journal of the British Interplanetary Society. I’ll deliver publishing details when they become available.
Here are the presentations of those associated with Tau Zero:
- E. Davis, “Faster-Than-Light Space Warps, Status and Next Steps”
- K. Denning, “Inertia of Past Futures” (anthropology)
- P. Gilster, “The Interstellar Vision: Principles and Practice”
- G. Landis, “Plasma Shield for an Interstellar Vehicle”
- C. Maccone, “Sun Focus Comes First, Interstellar Comes Second (Mission concept)”
- J. Maclay, “Role of the Quantum Vacuum in Space Travel”
- G. Matloff, “Light Sailing to the Stars”
- M. Millis, “Space Drive Physics, Intro and Next Steps”
- M. Millis, “Cockpit Considerations for Inertial Affect and FTL Propulsion”
- R. Noble, “Small Body Exploration Technologies as Precursors for Interstellar Robotics”
- S. White, “Warp Field Mechanics 101”
You may also be interested in Slate‘s take on the Symposium, which focuses on some of the breakthrough propulsion concepts at the far edge of the speculative frontier. The Smithsonian’s blog also carried an update about the conference, while MSNBC offered up a look at possible starship destinations, a major interest as we continue to lack planetary data for nearby stars. Finally, I loved Gregory Benford’s article describing the 100 Year Starship Symposium: The First Hard Science Fiction Convention.
Papers and presentations from the Icarus team in Orlando were plentiful indeed:
- J. Benford, “Recent Developments in Interstellar Beam-Driven Sails”
- B. Cress, “Icarus Interstellar’s New Icarus Institute for Interstellar Sciences”
- A. Crowl, J. Hunt, “How an Embryo Space Colonization (ESC) Mission Solves the Time-Distance Problem”
- J.R. French, “A Review of the Daedalus Main Propulsion System”
- R. Freeland, “Fission-Fusion Hybrid Fuel for Interstellar Propulsion”
- P. Galea, “Machine Learning and the Starship: A Match Made in Heaven”
- A. Hale, “Exoplanet Studies for Potential Icarus Destination Stars”
- A. Hein, “Technology, Society and Politics in the Next 100-300 Years: Implications for Interstellar Flight”
- A. Hein, K. Long, “Exploratory Research for an Interstellar Mission: Technology Readiness, Stakeholds and Research Sustainability”
- R. Obousy, “A Review of Interstellar Starship Designs”
- R. Obousy, “A 21st Century Interstellar Starship Study”
- M. Stanic, “Fusion Propulsion Comparison”
- R. Swinney, “Initial Considerations in Exploring the Interstellar Roadmap”
- R. Swinney, “Navigational and Guidance Requirements of an Interstellar Spacecraft”
- A. Tziolas, “Long Term Computing”
- A. Tziolas, ” Starflight Academy: Education in Interstellar Engineering”
Also, be aware that Ian O’Neill is continuing his coverage of the Icarus study, the latest article being a look at sex in space that circles around to starship design. Icarus team member Tiffany Frierson gives us her personal perspective on the conference (and it was a pleasure to meet Tiffany, who was often to be found circulating near the Icarus and Tau Zero tables snapping photos). Athena Andreadis presents an insightful look at the conception and preconceptions of the conference in If They Come, It Might Get Built. Finally, Centauri Dreams contributor and Astronomy Now editor Keith Cooper offers up his own take on starship design and fusion propulsion in an excellent essay that delivers helpful background and segues into the Icarus team’s thoughts on fusion’s future between the stars.
by Paul Gilster | Oct 7, 2011 | Outer Solar System |
Among all the planets, Uranus seems to get the least play in science fiction, though it does have one early advocate whose work I’ve always been curious about. Although he wrote under a pseudonym, the author calling himself ‘Mr. Vivenair’ published a book about a journey to Uranus back in the late 18th Century. A Journey Lately Performed Through the Air in an Aerostatic Globe, Commonly Called an Air Balloon, From This Terraquaeous Globe to the Newly Discovered Planet, Georgium Sidus (1784) seems to be reminiscent of some of Verne’s work, even if it pre-dates it, in using a then cutting-edge technology (balloons) to envision a manned trip through space.
Image: Near-infrared views of Uranus reveal its otherwise faint ring system, highlighting the extent to which it is tilted. Credit: Lawrence Sromovsky, (Univ. Wisconsin-Madison), Keck Observatory.
When ‘Vivenair’ wrote, Uranus had just been discovered (by William Herschel in 1781). The author used it as the occasion for political satire, and not a very good one, according to critic James T. Presley, who described it in an 1873 article in Notes & Queries as ‘a dull and stupid satire on the court and government of George III.’ Vivenair evidently put the public to sleep, for Uranus more or less fades from fictional view for the whole of the 19th Century. More recent times have done better. Tales like Geoff Landis’ wonderful “Into the Blue Abyss” (2001) bring Uranus into startling focus, and Larry Niven does outrageous things with it in A World Out of Time (1976). But although it doesn’t hold up well as fiction, Stanley G. Weinbaum’s story about Uranus may sport the most memorable title of all: “The Planet of Doubt” (1935).
What better name for this place? The seventh planet has a spin axis inclined by a whopping 98 degrees in reference to its orbital plane — compare that to the Earth’s 23 degrees, or Neptune’s 29. This is a planet that is spinning on its side. Conventional wisdom has it that a massive collision is the culprit, but the problem with that thinking is that such a ‘knockout blow’ would have left the moons of Uranus orbiting at their original angles. What we see, however, is that the Uranian moons all occupy the same 98 degree orbital tilt demonstrated by their parent.
New work unveiled at the EPSC-DPS Joint Meeting in Nantes, France is now giving us some answers to this riddle. A team led by Alessandro Morbidelli (Observatoire de la Cote d’Azur) ran a variety of impact simulations to test the various scenarios that could account for Uranus’ tilt. It turns out that a blow to Uranus experienced when it was still surrounded by a protoplanetary disk would have reformed the entire disk around the new and highly tilted equatorial plane. The result would be a planetary system with moons in more or less the position we see today, as described in this news release.
But this is intriguing: Morbidelli’s simulations also produce moons whose motion is retrograde. The only way to get around this, says the researcher, is to model the Uranian event not as a single impact but as at least two smaller collisions, which would increase the probability of leaving the moons in their observed orbits. Given all this, some of our planet formation theories may need revision. Says Morbidelli:
“The standard planet formation theory assumes that Uranus, Neptune and the cores of Jupiter and Saturn formed by accreting only small objects in the protoplanetary disk. They should have suffered no giant collisions. The fact that Uranus was hit at least twice suggests that significant impacts were typical in the formation of giant planets. So, the standard theory has to be revised.”
The questions thus raised by the ‘planet of doubt’ may prove helpful in understanding how giant planets evolve. More on this when the paper becomes available.
by Paul Gilster | Oct 6, 2011 | Asteroid and Comet Deflection |
Getting water into the inner Solar System is an interesting exercise. There has to be a mechanism for it, because the early Earth formed at temperatures that would have caused any available water to have evaporated. Scientists have long speculated that water must have been delivered either through comets or asteroids once the Earth had cooled enough to allow liquid water to exist. The former was preferred because the water content in comets is so much higher than in asteroids.
But the theory had problems, not the least of which was that comets studied in this regard showed deuterium levels twice that of Earth’s oceans. The ratio of deuterium and hydrogen, both made just after the Big Bang, can vary in water depending on its location because local conditions can affect the chemical reactions that go into making ice in space. A comparison of the deuterium to hydrogen ratio in extraterrestrial objects can be compared to water found in Earth’s oceans to identify the source of our water. Now comet Hartley 2 swings into the picture, for researchers have announced that its hydrogen/deuterium ratio is similar to Earth’s oceans.
Image: This illustration shows the orbit of comet Hartley 2 in relation to those of the five innermost planets of the Solar System. The comet made its latest close pass of Earth on 20 October last year, coming to 19.45 million km. On this occasion, Herschel observed the comet. The inset on the right side shows the image obtained with Herschel’s PACS instrument. The two lines are the water data from HIFI instrument. Credit: ESA/AOES Medialab; Herschel/HssO Consortium.
So how do you measure the hydrogen/deuterium ratio in the water of a comet? The answer is an instrument called HIFI, which operates aboard the European Space Agency’s Herschel infrared space observatory. HIFI (Heterodyne Instrument for the Far Infrared) is a high-resolution heterodyne spectrometer developed in The Netherlands that covers two bands from 480-1250 gigaHertz and 1410-1910 gigaHertz. Herschel was examining the comet’s coma, which develops as frozen materials inside vaporize when the comet moves closer to the Sun.
Remember, previous comet studies had found hydrogen/deuterium ratios different from our oceans. The difference between these comets and Hartley 2 may be that Hartley 2 was formed in the Kuiper Belt, whereas other comets studied in this regard are thought to have first formed near Jupiter and Saturn before being flung out by the gravitational effects of the gas giants, returning millions of years later for their pass around the Sun. The hydrogen/deuterium ratio we see in water ice may well have been different in the Kuiper Belt than in ice that first formed in the inner system, where conditions are much warmer. Further comets studies may confirm the idea.
Says Dariusz Lis (Caltech):
“Our results with Herschel suggest that comets could have played a major role in bringing vast amounts of water to an early Earth.This finding substantially expands the reservoir of Earth ocean-like water in the solar system to now include icy bodies originating in the Kuiper Belt.”
Surely the early oceans were the result of both comet and asteroid impacts, but the new findings point back to comets as major players. Even so, we have plenty of work to do to understand the role of the lightest elements and their isotopes in the early Solar System. Six comets besides Hartley 2 have been examined for hydrogen/deuterium levels, all with deuterium levels approximately twice that found in Earth water. Kuiper Belt comets were once thought to have even higher deuterium levels than Oort Cloud comets, an idea the Hartley 2 results have now refuted.
The team led by Paul Hartogh (Max Planck Institute for Solar System Research) has also used the Herschel Observatory to measure the hydrogen/deuterium ratio in comet 45P/Honda-Mrkos-Pajdusakova, another Kuiper Belt comet whose data is now under analysis, so we may soon have new data to add to this story. The paper is Hartogh, “Ocean-like water in the Jupiter-family comet 103P/Hartley 2,” published online in Nature 5 October 2011 (abstract).
And there is further news out of the joint meeting in Nantes, France, of the European Planetary Science Congress and the American Astronomical Society’s Division for Planetary Sciences, where this work was announced. As noted in this article in Nature, a new study of the Sun-like star Eta Corvi, which is roughly the same age our Sun was during the Late Heavy Bombardment (when most water is thought to have been delivered to the Earth), shows that the star has an inner ring of warm dust that is rich in carbon and water. Team leader Carey Lisse (JHU/APL) thinks we’re seeing the traces of one or more Kuiper Belt-class comets being flung into the inner system, colliding with a planet there to form the ensuing ring of material.
by Paul Gilster | Oct 5, 2011 | Exoplanetary Science |
Three planets recently discovered through Kepler data provide an interesting take on how we look at smaller planets. Not that the planets around the star designated Kepler-18 are all that small — two of them are Neptune-class and one is a super-Earth. But what is becoming clear is that given the state of our current technology, we’ll have to get used to a process different from planet verification as we move to ever smaller worlds. The technique is being referred to as planet validation — it helps us determine the probability that the detected object could be something other than a planet.
Image: The orbits of the three known planets orbiting Kepler-18 as compared to Mercury’s orbit around the Sun. Credit: Tim Jones/McDonald Obs./UT-Austin.
The new system shows how this works. Kepler-18 is a star similar to ours, about 10 percent larger than the Sun and with 97 percent of the Sun’s mass. Around it we have Kepler-18 c and d, which turn up through transits. Planet c has a mass of about 17 Earths and is thought to be some 5.5 times the size of Earth. Its orbit takes it around Kepler-18 in 7.6 days. Kepler-18 d is 16 times as massive as the Earth, 7 times Earth’s size, and orbits its primary in 14.9 days. These two Neptune-class worlds are, interestingly enough, in a 2:1 resonance: Planet c orbits the star twice for every single orbit of planet d. The demonstrable resonance is ample proof that these are planets in the same system and not something else mimicking a planetary signature.
But the super-Earth, Kepler-18 b, is something else again. A team led by Bill Cochran (University of Texas at Austin) went to work with the 5-meter Hale Telescope at Palomar, aided by adaptive optics, to examine Kepler-18 to see whether the transit signal they thought to be a super-Earth was genuine. Finding no background objects that could have influenced the finding, they were able to calculate the odds that Kepler-18 b is not a planet at 700 to 1. Cochran thinks this process of planet validation is going to become much more significant as Kepler brings in new data:
“We’re trying to prepare the astronomical community and the public for the concept of validation. The goal of Kepler is to find an Earth-sized planet in the habitable zone [where life could arise], with a one-year orbit. Proving that such an object really is a planet is very difficult [with current technology]. When we find what looks to be a habitable Earth, we’ll have to use a validation process, rather than a confirmation process. We’re going to have to make statistical arguments.”
So we can with a high degree of probability rule out any of the objects — stars, background galaxies — that might in any way compromise the transit data. The planetary signature of the super-Earth seems real enough, though established in a different way than Kepler-18 c and d, whose gravitational interactions can be readily demonstrated. The planet is thought to be 6.9 times Earth mass and twice Earth’s size. All three worlds orbit much closer to their parent star than Mercury does to the Sun, the super-Earth Kepler-18 b being the closest, with a 3.5 day period.
We can also deduce an interesting possibility about Kepler-18 b, as noted in the paper:
The inner, 3.5-day period planet Kepler-18b, is a super-Earth that requires a dominant mixture of water ice and rock, and no hydrogen/helium envelope. While the latter cannot be excluded simply on the basis of the planet’s mass and radius, the evaporation timescale for a primordial H/He envelope for a hot planet such as Kepler-18b is much shorter than the old age derived for the Kepler-18 system, and such a H/He envelope should not be present. Thus, despite its lower equilibrium temperature, Kepler-18b resembles 55 Cnc e and CoRoT-7b… Kepler-18b, together with 55 Cnc e… are likely our best known cases yet of water planets with substantial steam atmospheres (given their high surface temperatures).
The discovery was announced at a joint meeting of the American Astronomical Society’s Division of Planetary Science and the European Planetary Science Conference in Nantes, France. More on the Kepler-18 results in this news release from the University of Texas at Austin. Look for these results in an upcoming issue of the Astrophysical Journal Supplement Series devoted to Kepler, which will appear in November. The paper is Cochran et al., “Kepler 18-b, c, and d: A System Of Three Planets Confirmed by Transit Timing Variations, Lightcurve Validation, Spitzer Photometry and Radial Velocity Measurements” (preprint).
by Paul Gilster | Oct 3, 2011 | Culture and Society |
I’m just back from the 100 Year Starship Symposium. The thoughts below were written yesterday evening (the 2nd), just after the event ended.
It’s a lovely evening here in Orlando, one I’m enjoying while sitting out in front of the Hilton waiting for my taxi. I got a chuckle out of the audience at my talk at the 100 Year Starship Symposium when I mentioned something that is completely true: I’m actually a very retro kind of guy. Sure, starships are a passion, but I also restore old fountain pens, love film noir, and as I told the audience, chose an overnight sleeper train to come to Florida in rather than an aircraft.
They enjoyed the observation, probably because we’re all an odd mix of personally defined and often contradictory impulses. But as I soak up this gorgeous Florida evening, I’m feeling a profound singleness of purpose. To begin with, it’s clear to me that writing about the starship conference won’t be a matter of a single Centauri Dreams entry but rather a series of thoughts and recollections that will be scattered through any number of future articles. The experience was obviously memorable, the largest conference devoted to interstellar flight that I could have imagined, and as David Neyland, its organizer, told me, it happened because so many people came from so far in the service of a numbingly futuristic idea.
People like my friend Adam Crowl, who came all the way from Brisbane, Australia, and with whom I enjoyed good conversation throughout the event. People like Kelvin Long, the man whose inspiration put Icarus into operation, who came with fellow Icarus people like Pat Galea and Rob Swinney from the UK and Andreas Tziolas from Alaska. Marc Millis and I found an excellent Italian restaurant, and the next night I had a wonderful dinner conversation with Greg Benford over salmon and a superb Carneros Pinot Noir (thanks Al Jackson for picking up the wine tab!). I enjoyed my chats with Jim Benford as well, and it was great to see Richard Obousy, who came over from Texas. Special thanks to the many Centauri Dreams readers who introduced themselves as I walked between sessions.
If I had one criticism of what happened here, it’s that there were so many good papers to listen to, so many good people to hear, that the multi-track structure made it impossible to do everything I would have wanted to do. Michael Michaud’s paper on the long term implications of interstellar flight was a priority for me, but I had also committed to a number of readers that I would cover one of the breakthrough propulsion sessions — I was using Twitter to do a bit of live ‘micro-blogging’ — and I not only missed Michael’s talk, but found myself sitting on the floor typing, the session being completely packed as Marc Millis, Jordan Maclay, Eric Davis and Sonny White talked space drives and Alcubierre theory.
OK, you choose. Which of these would you go to and which would you regret missing:
- “A Review of Interstellar Starship Design” – Richard Obousy (Icarus Interstellar)
- “Light Sailing to the Stars” – Greg Matloff (New York City College of Technology)
- “Mass Beam Propulsion: An Overview” – Gerald Nordley
- Panel: “Structuring the 100 Year Starship” – Mae Jemison, moderator (The Jemison Group)
- “Making Aliens” – Athena Andreadis
- “Star Probes and ET Intelligence” – Stephen Baxter
It wasn’t easy, and it was like that all the time.
On the last day, we had a late meeting among Tau Zero and Icarus people and by the time we finished, almost everyone had left the conference facility. The venue was suddenly deserted and quiet, with that eerie sense you get when an enormous structure, seemingly at once, becomes empty. We found unused symposium programs and posters leaning up against a table. Think about this, I joked. We could collect all these and in twenty years, who knows what they would bring on eBay! We were laughing about this but I did cast a wistful glance back. Maybe we really should have picked the extras up…
Anyway, this was really a four-day conference packed into the equivalent of two days, so we were all running from paper to paper, session to session, with little time for breaks and even less time for meals until the day was over. A new meme was emerging – the ‘interstellar buzz’ – and it was palpable. I think everyone was as jazzed as I was about the fact that this meeting was even happening. How often do I get to chat with Jill Tarter in the elevator, catch up on the latest from my friend Claudio Maccone or have dinner conversation with John Cramer and Marc Millis talking about the CERN neutrino results?
Not that I was doing the talking in that conversation — I’m a writer, not a scientist, and I was in Orlando to keep learning as much as I could about a topic that’s so multi-faceted and rich that every new nugget uncovered seems to expose an even deeper vein of ore. So there was much listening to be done, banking on the willingness of scientist after scientist to share ideas and point me in the direction of further sources.
We managed plenty of Tau Zero and Icarus business as well, so in the rare free time discussions continued. The Icarus team was all over the place, and I quickly learned that if I stood even for a moment at the Tau Zero table, I would get pulled into a conversation related to one or the other (as well as my Tau Zero duties, I serve as a consultant for Icarus). My sense is that the starship conference is getting lots of pop from the media, which leads to the question of how long the interstellar buzz can be maintained. Time will tell, but my major goal long-term is to see the public getting back into the space game in terms of enthusiasm and interest, and turning Apollo-like passions toward the interstellar deep.
Can that happen? Maybe some day, and I’m not so unrealistic as to expect that a single symposium can make it happen overnight. But Dave Neyland had the right idea when he got DARPA into this game, because the DARPA imprimatur brought an intensity of focus that the community had been lacking. People who work on these topics invariably do so in their spare time. They’re separated not only by distance but the pressures of work and only occasionally see each other at conferences. An event like this can reveal how concentrated is their interest and how wide their potential audience, as long as we can build on what happened here.
I ran into a friend as I was waiting for my taxi who told me the whole thing was making him emotional, and I had something of the same reaction. What has to be said about many of the people working in this area is that they do it not only because of the utter fascination of the challenge, but because getting to the stars is a multi-generational quest for them, one they generally (though not universally) assume will not be achieved in their lifetimes, but one they believe with a passion their descendants will experience. And it is with a deep sense of commitment that they come forward to offer up their expertise for this gift to an unknowable futurity.
Emotional? Sure. Interstellar flight has long been talked about and it fills the pages of science fiction, but to see some of the best minds in a host of disciplines attacking it as a scientific problem and actually planning to create an organization that can last long enough to bring it seriously closer is a powerful experience. I’m now writing this in Orlando’s train station, having caught that taxi and resumed my work afterwards, and the sense that this was a once in a lifetime event just won’t go away. We’ll have other interstellar gatherings, but this one feels like a game-changer, one we’ll be talking about in various ways for a long time.
