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A Closer Look at the Titan Airplane

by Paul Gilster | Apr 6, 2012 | Outer Solar System | 11 Comments

Yesterday's discussion of the AVIATR mission to Titan inevitably brought up another prominent Titan mission concept: Titan Mare Explorer (TiME). I'll have more to say about this one next week, as today I want to continue talking about AVIATR, but you can once again see how Titan enthralls us with its 'Earth-like' aspects. Need a thick atmosphere around a moon? Titan is your only play, and if, as with TiME, you want to put an instrument package into an off-planet surface lake, you'll be hard pressed to do it anywhere else, at least in this Solar System. These two mission concepts fire the imagination -- they're the kind of thing kids like me used to dream about when we plunked down our money at the newsstand for copies of Galaxy or Fantasy & Science Fiction. It's unlikely, though, that both missions will fly. If TiME, which is a Discovery-class mission finalist and thus cost-capped at $425 million, is chosen, then the odds on AVIATR probably drop. AVIATR, a New Frontiers-class...

AVIATR: Roaming Titan’s Skies

by Paul Gilster | Apr 5, 2012 | Outer Solar System | 13 Comments

Each of our highest priority targets in the outer Solar System offers something unique, from Europa’s internal ocean to the geysers of Enceladus. But Titan exerts the kind of fascination that comes from the familiar. The imagery of lakes and river channels reminds us inescapably of our home world, even if the temperature on the Saturnian moon averages a brisk 94 K, which works out to -291 degrees on the Fahrenheit scale. But because of its thick atmosphere we have options for exploring Titan that are unavailable on the other icy moons, and we’re working with a landscape that is a compelling frozen doppelgänger of Earth, a landscape we’d like to explore up close. As we saw yesterday, part of the outer system puzzle is getting supplies of plutonium-238 up to speed, and there is at least some movement on that front. If we want to get aggressive about exploring Titan, one excellent way to deploy that plutonium is aboard AVIATR (Aerial Vehicle for In-situ and Airborne Titan...

Plutonium-238 and the Outer System

by Paul Gilster | Apr 4, 2012 | Missions | 13 Comments

Powering up a spacecraft is a lot easier to manage in the Sun-rich environment inside the orbit of Mars than it is out past the orbit of Jupiter. Solar panels provide plenty of power for a satellite in near-Earth orbit, for example, but moving into the outer system invokes the need for RTGs -- radioisotope thermoelectric generators -- powered by radioactive decay. If you read through the specs on the FOCAL mission design presented here last Friday, you saw that this attempt to reach the Sun's gravitational lens would demand 20 RTGs, and thus requires resumed production of plutonium-238. What's happened is that US production of 238Pu was halted as far back as 1988, leaving us with stockpiles that should be sufficient for missions in the pipeline through the end of this decade. That's the view of Leonard Dudzinski, NASA's Radioisotope Thermoelectric Generator program executive, who was speaking at the opening session of the 43rd Lunar and Planetary Science and the Nuclear and Emerging...

Planets Around an Ancient Star

by Paul Gilster | Apr 3, 2012 | Exoplanetary Science | 32 Comments

The idea of 'deep time' exerts an abiding fascination. H.G. Wells took us forward to a remote futurity when his time traveler looked out on a beach dominated by a red and swollen Sun. But of course deep time goes in the other direction as well. I can remember wanting to become a paleontologist when I discovered books about the world of the dinosaurs, my mind reeling from the idea that the world these creatures lived in was as remote as any distant star. Paleontology was a grade-school ambition I never followed up on, but the Triassic and Jurassic eras still have a hold on my imagination. In a SETI context, deep time presents challenges galore. Charles Lineweaver's work offers up the prospect that the average Earth-like planet in our galactic neighborhood may well be far older than our own -- Lineweaver calculates something like an average of 1.8 billion years older. Would a civilization around such a star, if one could survive without destroying itself for so long, have anything it...

Re-Thinking The Antimatter Rocket

by Paul Gilster | Apr 2, 2012 | Antimatter | 27 Comments

Once when reading Boswell's monumental life of the 18th Century writer and conversationalist Samuel Johnson, I commented to a friend how surprised I had been to discover that Johnson didn't spend much time reading in his later years. "He didn't need a lot of time," replied my friend, a classics professor. "He tore the heart out of books." That phrase stuck with me over the years and re-surfaced when I started working with Adam Crowl. More than anyone I know, Adam can get to the heart of a scientific paper and explain its pros and cons while someone like myself is still working through the introduction. And because of his fine work with Project Icarus, I thought Adam would be just the person to explain the latest thinking about a classic concept that Friedwardt Winterberg would like to take to the next level. by Adam Crowl In Jules Verne's From the Earth to the Moon, the bold Frenchman Michel Ardan, in his first speech to the Baltimore Gun Club, when discussing travelling to the Moon...

Correction re WISE

by Paul Gilster | Apr 2, 2012 | Administrative | 3 Comments

Last week I reported on information from a source on the WISE mission that no new red dwarfs had yet been discovered out to a distance of 10 light years. This past weekend I received an email from my source apologizing for mis-typing. He had meant to say no brown dwarfs -- not red dwarfs -- out to a distance of 10 light years. And as I mentioned with the earlier post, the data analysis continues and there may be surprises yet to come. A nearby brown dwarf is something I've been writing about here for some time, pondering its implications and wondering whether one might actually turn up that was closer than the Alpha Centauri stars. So the news is that no brown dwarfs matching the description have yet turned up, but the hunt continues.

Interstellar (Precursor) Mission & Vehicle Design

by Paul Gilster | Mar 30, 2012 | Uncategorized | 39 Comments

by Marc Millis Tau Zero's first graduate student project has been completed. Berkeley Davis, a 2nd Lt. at the United States Air Force Institute of Technology, Dayton Ohio, completed his Masters thesis on a deep space probe to perform Claudio Maccone's gravitational lens mission (FOCAL). For those unfamiliar with FOCAL, it is a mission to utilize the gravitational lens effect that begins at approximately 550 AU from the Sun, one that in the view of Maccone will offer huge magnifications for the study of targets like the Cosmic Microwave Background. For more, see the Centauri Dreams archives. IMPETUS Maccone, Deep Space Flight and Communications: Exploiting The Sun as a Gravitational Lens (Springer, 2009). MISSION/VEHICLE STUDY Davis, Berkeley. R. (2012) Gravitational Lens: The Space Probe Design (Thesis), AFIT/GA/ENY/12-M06, Air Force Institute of Technology. To provide a realistic baseline on what is possible, the student was asked to constrain his design to commercially...

ESO: Habitable Red Dwarf Planets Abundant

by Paul Gilster | Mar 29, 2012 | Exoplanetary Science | 45 Comments

Red dwarfs are all over the news thanks to an announcement by the European Southern Observatory. Results from a new HARPS study show that tens of billions of planets not much larger than Earth are to be expected in the habitable zones around this class of star. The finding reinforces the growing interest in M-class stars and becomes especially interesting when you realize that faint red stars like this make up as much as 80 percent of the stars in the Milky Way. That leaves plenty of room for astrobiology, depending on factors we need to discuss below. Do we suddenly have a close destination for a potential interstellar probe? Well, Barnard’s Star has always been in the running for an early mission because of its relative proximity to us at 5.94 light years. But we still have no word on planets there (despite a much publicized but soon discredited set of observations from a 1969 paper). Proxima Centauri is available at 4.2 light years, but we have yet to learn whether it has planets....

An Interstellar Reminiscence

by Paul Gilster | Mar 28, 2012 | Culture and Society | 2 Comments

by A. A. Jackson Although it was probably science fiction that got Al Jackson into interstellar flight, he remembers discovering the work of Eugen Sänger back around 1960 and becoming energized to seek out the few scientific papers on relativistic rocket designs that were then available. With a firm background in engineering, he turned to physics in 1975, receiving a PhD from the University of Texas at Austin, a natural move for a man who had worked for NASA during the heyday of Apollo as astronaut trainer on the Lunar Module Simulator. Going through Al’s papers is a fascinating exercise in its own right, but I was reminded because of our recent articles on Robert Bussard’s ramjet ideas that Al had worked with Daniel Whitmire. Bussard spoke about fusing protons in his ramscoop engine, but subsequent analysis showed that the power needed to compress protons to fusion densities far outweighed the power that would be produced. It was Daniel Whitmire who developed the ‘catalytic ramjet’...

Catalyzed Fusion: Tuning Up the Ramjet

by Paul Gilster | Mar 27, 2012 | Missions | 18 Comments

Long-time Centauri Dreams readers have learned to tolerate my eccentricities (or, at least, they’re kind enough not to dwell on them). One of them is my love of poking around in old books related to space travel, which is how Benjamin Field’s A Narrative of the Travels and Adventures of Paul Aermont Among the Planets (1873) recently caught my eye. I don’t know much about Field other than that he chose to produce this tale of interplanetary wanderings under a pseudonym, but what’s fun about his tale is that after his journeys to Jupiter, Saturn, Mars and Venus are over, Field’s protagonist returns to Earth to find that the planet is fully fifty years older, though he himself has aged hardly at all. Time dilation, the reader might say, but of course Field wouldn’t have known anything about special relativity. It’s fun to consider, though, how an idea that in 1873 would have been simple fantasy -- that someone might travel at high speed and age at a different rate than those he left...

A Brief Window: The Bussard Ramjet in the 1960s

by Paul Gilster | Mar 26, 2012 | Culture and Society | 18 Comments

It's fascinating to watch how expansive ideas take hold in the public imagination. The idea of a starship that could scoop up particles from the interstellar medium came to Robert Bussard while he was at Los Alamos Scientific Laboratory and, as we saw recently in our articles on slowing down a starship, became the basis for subsequent magsail concepts because Bussard's design evidently generates far more drag than effective thrust. But before the problems of the design became widely known, Walter Sullivan, a writer for the New York Times, had brought the ramjet into play for future human journeys to the stars in a book called We Are Not Alone (definitely not the same book as the 2011 title by Dirk Schulze-Makuch). Subtitled 'The Continuing Search for Extraterrestrial Intelligence' in its latest revision, the original 1964 book was written at a time when SETI was an infant discipline (although the later revision goes through the Drake equation and places SETI in the context of...

Century of the Starship

by Paul Gilster | Mar 23, 2012 | Culture and Society | 33 Comments

I once thought about putting together a collection of classic papers on interstellar flight. It would start with early work by the likes of Les Shephard, Eugen Sänger and Carl Wiley (whose groundbreaking paper on solar sails appeared not in a scientific journal but in Astounding Science Fiction). The book would proceed with the key papers of Forward, Bussard and Dyson and move into papers from the Project Daedalus report, then to Matloff and Mallove and up to the present day, with a long look at the Italian solar sail work of Vulpetti, Maccone and Genta. Especially later in this period there is abundant material to choose from, and there's Alcubierre to consider, and Millis' work with the Breakthrough Propulsion Physics project. And then there's Geoff Landis and Robert Frisbee and the closely reasoned sociological analyses of Michael Michaud and... Well, you can see what happens when you start pondering editing possibilities. The book is already growing to enormous size and I've done...

Crowd-Funding the Exomoon Hunt

by Paul Gilster | Mar 22, 2012 | Astrobiology and SETI | 27 Comments

I've been trying to figure out why exomoons -- moons around planets that orbit stars other than our own -- have such a fascination for me. On the purely scientific level, the sheer amazement of discovery probably carries the day, meaning that I grew up in a time long before we had confirmation of any exoplanets, and now we're talking about getting data on their moons. But there's also that sense of the exotic, for we can wonder whether gas giants in the habitable zone, which may be more plentiful than we realize, might have life on their own rocky moons. David Kipping (Harvard-Smithsonian Center for Astrophysics) has been a key player in the exomoon hunt for some time now (search under his name in the archives here and you'll retrieve articles going back for years). David is now working with a 'crowd-funding' source called Petridish.org to fund a new mini-supercomputer that will go to work on the Hunt for Exomoons with Kepler (HEK) project. The idea behind HEK is to use Kepler data...

Starship Surfing: Ride the Bow Shock

by Paul Gilster | Mar 21, 2012 | Interstellar Medium | 26 Comments

We've been looking at slowing down a starship, pondering ways the interstellar medium itself might be of use, and seeing how the stellar wind produced by the destination star could slow a magsail. A large solar sail could use stellar photons, but the advantage of the magsail is that it's going to be effective at a greater distance, and we can also consider other trajectory-bending effects like the Lorentz turning studied by Robert Forward and P.C. Norem. But if you take a look at the relevant papers on magsails and other uses of the medium, you'll find that they all assume the interstellar medium is more or less uniform. We know, of course, that it is not. For one thing, the Sun itself seems to be near the boundary of the Local Interstellar Cloud, and there are a number of such clouds within about 5 parsecs of the Solar System. In fact, we're not exactly sure whether the Sun is just outside the LIC or barely within it. In any case, as Ian Crawford has pointed out, Centauri A and B...

Interstellar Space: Uses of the Medium

by Paul Gilster | Mar 20, 2012 | Missions | 3 Comments

One of the first things we need to do in terms of interstellar exploration is to get a spacecraft built for the purpose to travel outside the heliosphere and give us solid measurements on the interstellar medium. The Voyagers are doing their best but they were never designed for what has become their interstellar mission, and while we can marvel at their longevity, it's with the knowledge that their resources are few and their years of useful data gradually drawing to an end. Something along the lines of Ralph McNutt's Innovative Interstellar Explorer would do the job nicely, allowing us to sample the environment that much longer missions will have to work in. Lorentz Force Turning The interstellar medium (ISM) is important not just because we have to learn about things like shielding a fast-moving spacecraft and cosmic ray flux but also because we may be able to use some aspects of the medium for deceleration. Yesterday's discussion of magsails reminded me of a 1969 paper by P. C....

Braking Against a Stellar Wind

by Paul Gilster | Mar 19, 2012 | Interstellar Medium | 12 Comments

This morning I want to pick up on the 'problem of arrival' theme I began writing about on Friday, and we'll look at interstellar deceleration issues a good bit this week. But I can't let Monday start without reference to the Icarus results from Gran Sasso that finds neutrinos traveling at precisely the speed of light. All of this adds credence to the growing belief that the earlier Opera experiment was compromised by equipment problems. The news is all over the place (you might begin with this BBC account) and while we'll keep an eye on it, I don't plan to spend much time this week on neutrinos. We still have much to get done on the subject of slowing down. Magsails and Local Resources When you begin to unlock the deceleration issue, the options quickly multiply, and you find yourself looking into areas that weren't remotely the subject of your earlier research. As we saw on Friday, the concept of magnetic sails grew organically out of Robert Bussard's idea of an interstellar ramjet....

Starships: The Problem of Arrival

by Paul Gilster | Mar 16, 2012 | Sail Concepts | 30 Comments

You wouldn't think that slowing down a starship would be the subject of a totally engrossing novel, but that's the plot device in Poul Anderson's Tau Zero (1970, though based on a 1967 short story called "To Outlive Eternity"). Anderson's ramscoop starship, the Leonora Christine, can't slow down because of damage suffered in mid-cruise. Edging ever closer to the speed of light, the crew experiences all sorts of time dilation wonders as they wrestle to regain control, and the ending, while scientifically dubious, is also in every way unforgettable. Anderson could be guilty of over-writing but few writers are gifted with his sheer imaginative sweep. I'm thinking that coupling a ramscoop with a problem in deceleration is just the ticket for getting into the whole issue of starship arrivals. We can start with Robert Bussard's 1960 paper "Galactic Matter and Interstellar Spaceflight," which unwittingly paved the way for the whole magsail concept. Bussard came up with what for a time...

WISE: Into the Infrared Sky

by Paul Gilster | Mar 15, 2012 | Deep Sky Astronomy & Telescopes | 13 Comments

As promised, we now have the infrared sky at a new level of detail thanks to the labors of the Wide-Field Infrared Survey Explorer (WISE) mission, which has now mapped (with a few slight glitches) more than half a billion objects, from galaxies to stars to asteroids and comets. We can now expect a new wave of papers from the more than 2.7 million images WISE has delivered at four infrared wavelengths and can explore the WISE atlas of some 18,000 images ourselves. The Big Picture But first, I want to step back and look at astronomical discovery in context, a thought spurred by Larry Klaes, who sent me a note originally posted on the HASTRO-L mailing list (by Rich Sanderson, of the Springfield Science Museum in Massachusetts). Every now and then I read something that wraps back into the past and yet implies future things, generating a sense of connection with what the enterprise is all about. Such is the case in this passage Sanderson quotes from an 1875 book by Richard Proctor that...

Thoughts on Antihydrogen and Propulsion

by Paul Gilster | Mar 14, 2012 | Antimatter | 22 Comments

Normally when we talk about interstellar sail concepts, we're looking at some kind of microwave or laser beaming technologies of the kind Robert Forward wrote about, in which the sail is driven by a beam produced by an installation in the Solar System. Greg and Jim Benford have carried out sail experiments in the laboratory showing that microwave beaming could indeed drive such a sail. But Steven Howe's concept, developed in reports for NASA's Institute for Advanced Concepts, involved antimatter released from within the spacecraft. The latter would encounter a sail enriched with uranium-235 to reach velocities of well over 100 kilometers per second. That's fast enough to make missions to the nearby interstellar medium feasible, and it points the way to longer journeys once the technology has proven itself. But everything depends upon storing antihydrogen, which is an antimatter atom -- an antiproton orbited by a positron. Howe thinks the antihydrogen could be stored in the form of...

Looking Into Kepler’s Latest

by Paul Gilster | Mar 13, 2012 | Astrobiology and SETI, Exoplanetary Science | 37 Comments

I've held off a bit on the latest Kepler data release because I wanted some time to ponder what we're looking at. The list of candidate planets here is based on data from the first sixteen months of the mission, and at first blush it seems encouraging in terms of our search for Earth-class planets. But dig deeper and you realize how much we still have to learn. Not all the trends point to the near ubiquity of rocky worlds in the habitable zone that some have hoped for. You might remember, for example, Carl Sagan famously saying (on 'Cosmos') that one out of every four stars may have planets, with two in each such system likely to be in the habitable zone. Kepler's Candidates and Some Qualifications I remember being suitably agog at that statement, but we've learned more since. John Rehling, writing an essay for SpaceDaily, didn't miss the Sagan quote and uses it to contrast with his own analysis of the new Kepler material showing that Earth-like planets may be considerably harder to...

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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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