Prior Visions of Star Flight

by Marc Millis Here is a holiday gift from Tau Zero as compiled by TZF's founding architect Marc Millis. It's part of Marc's continuing effort to find earlier references to the interstellar concepts -- many of them in fiction -- that we routinely ponder today. Some of these go back to the early 20th Century and in some cases the 19th. Compilations like this are always works in progress, as we found when putting together a list of interstellar propulsion concepts for the first chapter of the book Marc and Eric Davis edited, Frontiers of Propulsion Science, where one memory triggered another and the list kept growing. Readers are encouraged, then, to add other references to older material, as those of us who delight in prowling through old science fiction magazines have access to a mother lode of fictional precedents. I'll also mention that this post will be the last of 2011 -- as I did last week, I'll skip the Friday and Monday posts in honor of the holiday, with the next post...

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New Work on FTL Neutrinos

A paper in the December 24 issue of Physical Review Letters goes to work on the finding of supposed faster-than-light neutrinos by the OPERA experiment. The FTL story has been popping up ever since OPERA -- a collaboration between the Laboratori Nazionali del Gran Sasso (LNGS) in Gran Sasso, Italy and the CERN physics laboratory in Geneva -- reported last September that neutrinos from CERN had arrived at Gran Sasso's underground facilities 60 nanoseconds sooner than they would have been expected to arrive if travelling at the speed of light. The resultant explosion of interest was understandable. Because neutrinos are now thought to have a non-zero mass, an FTL neutrino would be in direct violation of the theory of special relativity, which says that no object with mass can attain the speed of light. Now Ramanath Cowsik (Washington University, St. Louis) and collaborators have examined whether an FTL result was possible. Neutrinos in the experiment were produced by particle...

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Complex Molecules on Pluto

I hope everyone is having a happy holiday season and looking forward to the upcoming New Year's festivities. In the intervening window, let's look at the outer Solar System. No other spacecraft has ever come as close to Pluto as New Horizons now has, already halfway between the Earth and the distant dwarf planet. It's also worth mentioning that New Horizons is only the fifth spacecraft to venture so deep into the Solar System, following the two Voyagers and the Pioneer spacecraft. July of 2015 will be an extraordinary time as we wait for data return from the mission and begin to find answers to some of the many questions that await us there. But studies from closer to home are continuing to reveal more about Pluto/Charon as well. The Cosmic Origins Spectrograph aboard the Hubble Space Telescope has found evidence for complex hydrocarbon and/or nitrile molecules on the planetary surface. Alan Stern, principal investigator for New Horizons, is behind the study, whose work was recently...

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A Break for the Holidays

Best holiday wishes to all from Centauri Dreams. I'm now going on an abbreviated schedule, with no post today or on Monday. I'll follow the same pattern next week as we close in on the New Year. The next regular post, then, will appear Tuesday December 27, and we'll see what interesting news items accumulate between now and then. Let me also add thanks to the entire readership for high-quality comments all through 2011 that have focused our discussions and opened up new insights on interstellar topics. Here's to holiday cheer, good companionship and breakthrough ideas.

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Planets Survive Red Giant Expansion

The most interesting thing about the worlds known as KOI 55.01 and KOI 55.02 is not just the fact that they are -- if current thinking holds -- the smallest planets yet detected around an active star other than our Sun, but that they are evidently survivors of the most extreme kind of experience. KOI 55, their host star, is of subdwarf B class, the exposed core of a red giant that has lost most of its gaseous envelope. The two planets that circle it are in such tight orbits that they would have been engulfed when the central star went through its red giant expansion. What a scenario, one we've often contemplated in these pages as we look toward the future of our own Sun. We tend to think in terms of planets that survive the red giant phase by orbiting far enough from the primary not to be swallowed up in it -- smaller worlds like Mercury, Venus and the Earth would not survive the experience. But KOI 55.01 and KOI 55.02 evidently were swallowed, and probably represent the remains of...

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Kepler Finds Earth-Sized Planets

I'm delighted that we keep finding solar systems so different from our own. The discovery of two new planets that are roughly the size of the Earth just confirms the feeling -- in a galaxy of dazzling fecundity, every system we look at has its own peculiarities to instruct and delight us. The system around the star called Kepler-20 (from its designation by the space observatory studying planetary transits) is a case in point. Yes, it has small, rocky worlds, but it also has three larger planets, and all five orbit closer than the orbit of Mercury in our own system. Kepler-20 is a G-class star somewhat cooler than the Sun located some 950 light years from Earth in the constellation Lyra. Moreover, while we once assumed that smaller planets orbited close to stars while larger gas giants orbited further out in the system (again based on our own system and our assumptions about it), our new discoveries point to different scenarios. In Kepler-20 we have a system where the larger planets...

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Update on Innovative Interstellar Explorer

by Ralph McNutt Because of the interest that the Innovative Interstellar Explorer mission generates whenever I write about it, I was pleased to receive Ralph McNutt's latest update on IIE. This was written in response to a recent article in these pages on the Voyager missions and refers to several of the comments in that thread. I first talked to Dr. McNutt about interstellar precursors back in 2003, when researching my Centauri Dreams book. Now at Johns Hopkins University Applied Physics Laboratory, the physicist's space experience is comprehensive. He is Project Scientist and a Co-Investigator on NASA's MESSENGER mission to Mercury, Co-Investigator on NASA's Solar Probe Plus mission to the solar corona, Principal Investigator on the PEPSSI investigation on the New Horizons mission to Pluto, a Co-Investigator for the Voyager PLS and LECP instruments, and a Member of the Ion Neutral Mass Spectrometer Team on the Cassini Orbiter spacecraft. He has published over 150 science and...

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Into the Planetary Rainforest

So-called 'super-Earths,' planets larger than the Earth but smaller than Neptune, pose problems to our theories of planet formation. The most recent illustration of this came in the announcement that the candidate planets found by Kepler had now reached 2,326. Remember, many of these will not be confirmed -- they're candidates -- but taken in the aggregate, what is interesting here is that one-third to one-half of these candidates fit the super-Earth category. And just as we had a problem with 'hot Jupiters' in trying to figure out their orbital position, many of these new planets are likewise in orbits close to their parent star, where the models say they shouldn't be. Things seemed so much simpler when we just had a single solar system to worry about, our own. Then, the idea of core accretion could readily account for everything we saw. The dust in the protoplanetary disk was thought to have aggregated into small planetesimals which, in the course of time and numerous collisions,...

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Spaceflight and Legends: A Dialogue with Michael Michaud

I’ve been hoping to publish a dialogue between Michael Michaud and myself ever since talking to him at the 100 Year Starship Symposium and pondering his paper “Long-Term Perspectives on Interstellar Flight." Centauri Dreams readers will know Michael as the author of the must-have Contact with Alien Civilizations: Our Hopes and Fears about Encountering Extraterrestrials (Springer, 2006), and will also remember his contributions to previous articles in these pages. He has served as director of the U.S. State Department’s Office of Advanced Technology and acted as chairman of working groups at the International Academy of Astronautics that discuss SETI issues, in addition to publishing numerous articles and papers on the implications of contact. In this dialogue, I took some of the elements of his 100 Year Starship presentation and used them as the launching pad for an exploration of how to turn humanity’s attention starward. PG: Michael, I’ve been going through the paper you presented...

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Voyager in the Doldrums

One of the pleasures of writing Centauri Dreams is digging into a paper to look at it from various directions, as I did recently with Jim Benford's work on cost-optimized beamed sails. Jim has been working on these concepts for a long time, and although I had originally intended to devote two days to his latest, the depth of his analysis led me to extend the discussion to a third day. That kind of focus invariably means I get behind in other stories, though, so I want to be sure to catch up with matters like the recent news about the Voyagers as they continue to exit our system. I always point to the still functioning instruments of the Voyagers as an outstanding example of how we can build spacecraft for the long haul -- these tough platforms show what can be done with careful design, and future craft fully optimized for even longer flights certainly seem practical. In this case, three instrument packages -- the Cosmic Ray Subsystem, the Magnetometer and the Low Energy Charged...

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Notes & Queries 12/14/11

I normally scan through various news items for the Notes & Queries posts, but in this case I've been trying to catch up on my reading. In particular, I've been looking at books that could be useful in inspiring young people to get interested in astronomy and engineering. Here's a look at three titles that more or less fit that bill. The budding rocket scientist will love the revised Zubrin, particularly with its infectious and expansive sense of what's possible, but younger students may find their minds tweaked by the two other selections, both of which I'd recommend for a high-school audience. We never know what can launch a career, but scientists are always reminding me of particular books they read when they were kids that made all the difference. Back to the Red Planet Toward the end of Robert Zubrin's The Case for Mars (revised edition, 2011), the author looks at three possible models for getting humans to the Red Planet. It's a significant section because Zubrin recognizes the...

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A Path Forward for Beamed Sails

Minimizing the cost of a project is no small matter because, as Jim Benford points out in the paper we've been examining over the past several days, cost determines how we decide on competing claims for resources. In the case of a beamed sail mission and its infrastructure, the cost is largely the reusable launcher or 'beamer,' which is the beam source and the antennae needed to radiate the beam. Benford is able to derive general relations for cost-optimal transmitter aperture and beam power, from which he can estimate capital cost and operating cost using today's parameters. He can then study the economics of high-volume manufacturing. How to get from today's economics to tomorrow's? This is where the concept of the 'learning curve' comes into play -- it is the decrease in unit cost of hardware with increased production. A 90 percent learning curve means that the cost of a second item is 90 percent the cost of the first, while the fourth is 90 percent the cost of the second, and as...

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Obousy Appearance on TV Tonight

Be aware that the History Channel show The Universe will air an episode at 2200 EST tonight (December 13) in which Richard Obousy will discuss interstellar propulsion concepts. The air time will probably vary depending on your cable provider, so be sure to check. Richard, once project leader of the Icarus effort and still actively involved at every stage of the Icarus design, is a Texas-based physicist whose work we have often discussed in these pages. I was there for his presentation on Icarus at the recent Oak Ridge interstellar workshop and look forward to seeing him on the tube. Addendum: This episode is now available online.

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Optimizing Interstellar Mission Costs

Although we frequently talk about beamed sails for interstellar missions, the fact is that spacecraft on the scale Robert Forward used to talk about that could take us to Alpha Centauri in 40 years won't come out of nowhere. The evolution of the solar sail into the beamed sail will involve all kinds of experimentation and a variety of mission concepts developed for use right here in the Solar System. Consider just one, a microwave-driven sail that could reach Mars in one month, and Pluto in five years. I wrote about this one in A Microwave-Beamed Sail for Deep Space. The idea comes from Jim and Greg Benford, who discussed it in a 2006 issue of the Journal of the British Interplanetary Society. The scenario involved a phenomenon the duo had discovered in their laboratory work on microwave beaming. Experimenting with a 7.5 g/m2 carbon sail, they had uncovered the fact that molecules evaporating from the sail created accelerations beyond what would have been expected from photons alone....

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The Case for Beamed Sails

There is a natural path through solar sails, which are now flying, toward beam-driven propulsion, and it's a path Jim Benford has been exploring for the last eighteen years. In my Centauri Dreams book I described how Jim and brother Gregory ran experiments demonstrating that carbon sails could be driven by microwave beams back in the year 2000. We learned that the theory worked -- a sail could indeed be propelled by a beam of photons -- and moreover, we learned that the configuration of the craft and propulsion system allowed it to be stable. Now we're talking about beam-riding, which the Benfords were able to demonstrate in later experiments. For it turns out that the pressure of the beam will keep a concave-shaped sail in tension, and as Jim pointed out in a recent email, the beam also produces a sideways restoring force. His work showed that a beam can also carry angular momentum and communicate it to the sail, allowing controllers to stabilize the structure against yaw and drift....

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Detecting a ‘Funeral Pyre’ Beacon

Beamed propulsion continues to be a particular fascination of mine, which is why I want to start a discussion tomorrow of Jim Benford's latest paper on beamed sails and how they might be optimized for both performance and cost. Reading through Benford's work, however, I also came across Chris Wilson's recent articles in Slate, which discuss Jim and Gregory Benford's work on interstellar beacons and the SETI ramifications. I want to be sure to point to Wilson's How to Build a Beacon because I don't see 'Benford beacons,' as they're increasingly called, discussed much in the media, and Wilson does a fine job at setting the concept in context. Messages into Deep Time The two part Slate series (the first article is The Great Silence) considers humanity's legacy and relates it to the issues raised by SETI. The Arecibo message sent in the direction of the globular cluster M13 in November of 1974 is Wilson's point of departure. Carl Sagan and Frank Drake set up the famous message in the...

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New Worlds Targeted by Allen Telescope Array

The on-again, off-again SETI search at the Allen Telescope Array is back in business as Jill Tarter and team focus in on some of the more interesting worlds uncovered by the Kepler space telescope and follow-up observations. You'll recall that last April the ATA was in hibernation, having lost its funding from the University of California at Berkeley, which had operated the Hat Creek Observatory in northern California where the ATA is located. It took a public campaign to raise the funds needed for reactivation and new operations, as well as help from the US Air Force in the form of its own assessment of the ATA's applicability in its space situational awareness studies, which include developing a catalog of orbiting space objects. The SETI Institute, along with third-party partners and volunteers, has set up SETIstars.org as a fund-raising operation specifically targeting the ATA -- it's important to realize that getting the array back in operation is a first step in the larger...

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Kepler-22b: A ‘Super-Earth’ in the Habitable Zone

It's fun to see Kepler-22b -- an intriguing new world that lies 600 light years from us toward Lyra and Cygnus -- being referred to as the 'Christmas planet' in the newspapers this morning, the latter a nod to Kepler chief scientist William Borucki, who said he thought of the planet that way, as a seasonal gift to the team. Borucki's enthusiasm is understandable, and it's echoed by Geoff Marcy (UC-Berkeley), who called the Kepler-22b work a 'phenomenal discovery in the course of human history.' I can't argue with scientists of this calibre -- with a surface temperature not so different from an April afternoon where I live, Kepler-22b can lay claim to being the smallest planet we've found orbiting in the habitable zone of a star like our Sun. The host star is, in fact, a G5-class object with mass and radius only slightly less than that of our Sun, which is a G2, and the planet in question orbits it with a period of 289 days, some 15 percent closer to its star than we are to ours....

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Terraforming: Enter the ‘Shell World’

If we ever achieve manned missions to the stars, one of the assumptions is that we will find planets much like Earth that we might live on and colonize. But what if the assumption is flawed? There are surely many Earth analogues in the Milky Way, but we don't know how widely they are spaced, and a near-miss isn't necessarily helpful, as both Mars and Venus attest. People like Robert Zubrin continue to advocate terraforming as a solution for Mars, and it may well happen one day, but supposing we get to another star, would we have the moral right to terraform a world with living creatures on it, even if they didn't meet our criteria for intelligence? Robert Kennedy (The Ultimax Group), working with colleagues Kenneth Roy and David Fields, has been pondering these issues and went through a possible solution at the recent Tennessee Valley Interstellar Workshop in Oak Ridge. If we stop worrying about Earth analogues, a range of interesting possibilities open up, as our own Solar System...

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Interstellar Flight: Equations and Art

Les Johnson (MSFC) always says that the coolest job title he ever had in his long career at NASA was Manager of Interstellar Propulsion Research. Think about it -- if going to the stars is your passion and you have a title like that, you must feel that you have really arrived. These days he goes by the more prosaic title of Deputy Manager for the Advanced Concepts Office at Marshall Space Flight Center in Huntsville, but as the recent interstellar workshop in Oak Ridge demonstrated, he's also ranging widely on his own as conference organizer, author and science fiction aficionado. His presentation in Oak Ridge was designed to jump start the conference with a survey of the problems of interstellar flight and the long list of possible propulsion solutions. The Interstellar Conundrum The problems are clear enough. Think of the distance between the Earth and the Sun (about 150 million kilometers). That's 1 astronomical unit (AU). Shrink that distance to one foot and imagine the Solar...

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Charter

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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If you'd like to submit a comment for possible publication on Centauri Dreams, I will be glad to consider it. The primary criterion is that comments contribute meaningfully to the debate. Among other criteria for selection: Comments must be on topic, directly related to the post in question, must use appropriate language, and must not be abusive to others. Civility counts. In addition, a valid email address is required for a comment to be considered. Centauri Dreams is emphatically not a soapbox for political or religious views submitted by individuals or organizations. A long form of the policy can be viewed on the Administrative page. The short form is this: If your comment is not on topic and respectful to others, I'm probably not going to run it.

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