Centauri Dreams
Imagining and Planning Interstellar Exploration
Revealing The New Universe and a Shared Cosmology
By Larry Klaes
Larry Klaes, a frequent Centauri Dreams contributor and commenter, here looks at a new book that explores humanity’s place in the cosmos. Is there a way to rise above our differences of outlook and perspective to embrace a common view of the universe? The stakes are high, for technology’s swift pace puts the tools of exploration as well as destruction in our hands. C.P. Snow explored the gulf between science and literature 50 years ago, but as Larry notes, the division may be broader still as we confront the possibility of intelligent life other than ourselves.
Just about anyone who has even taken the time to go outside on a clear night and stare up at the starry firmament over their head (assuming it is also largely free of the relatively recent artificial impediment called light pollution) has often been moved in rather profound ways by the sight, whether they are astronomically inclined or not. This feeling can be summed up, I think, by this quote from the artist Vincent van Gogh: “When I have a terrible need of – shall I say the word – religion. Then I go out and paint the stars.”
The Universe – or, I should say, what we can see with unaided vision, which amounts to several thousand stars (including the Sun), the Moon, and a few neighboring planets as viewed from Earth – seems to have always evoked such “spiritual” thoughts and feelings since the time of our very distant ancestors: There is the plausible theory that some of the animal drawings found in many of the caves of prehistoric Europe actually represent star patterns. The heavens were where the most powerful gods resided, both visible and hidden. The skies were also home to what various cultures considered their best members, once they passed on from this life (usually their rulers and warriors).
Then science came along and did its level best to end all this superstitious nonsense.
Oh, it all started out innocently enough. Some ancient Greek thinkers like Thales of Miletus simply removed the supernatural elements from the natural explanations for the nature of the world. Others like Democritus considered all gods to be the products of limited and flawed human imaginations and that only “atoms and the void” made up the real Universe. One man named Aristarchus of Samos went as far to say that Earth was a mere planet circling the Sun, which was just one of those numerous points of light in the night sky.
However, the ideas of these guys never quite caught on with most of humanity, which needed to know in their hearts that not only were they more than just a temporary collection of elements, but that someone or something out there considered them to be very special despite their often very obvious limitations and flaws. Thus for most of the next few thousand years, the West stuck largely with religion for their comforting answers, which did not have and often even rejected any solid evidence for the proof of its legitimacy.
Things started to really get torn apart culturally when the Renaissance and the Enlightenment came along. The turning point for this change is often cited as the day that the Roman Catholic Church told the Italian astronomer Galileo Galilei to stop supporting the ideas of one Nicholas Copernicus (who was influenced by the aforementioned Aristarchus) and anything else that seemed to contradict what was written in the Bible – or else.
Although Galileo essentially complied with the Church authorities, the ball named science began to really get rolling after this event and gained speed in the following centuries. Among those who did the most to solidify science as the main way to view the Cosmos in those early days of the so-called modern era was Sir Isaac Newton, who showed that it was gravity which kept Earth orbiting the Sun rather than fly off into the void and not bands of angels pushing our planet around our star via God’s Will.
Ironically, Newton was also a devout Christian who intensely studied the Bible to determine, among other things, that the world would come to an end in the year 2060. This was not terribly strange, however, as most scholars of his time and place did not see a division between science and religion; they assumed that God had made the Universe and science was the divinely inspired way for humanity to learn how He did it.
Eventually, though, as science and technology gained a stronger footing in civilization, the division between empirical and spiritual knowledge grew to the point that even today, the general public tends to feel torn and alienated by the perceived coldness and fact-only basis of science and the emotion-based ideas of religion and spirituality. Many folks often end up choosing one viewpoint or the other, conflicting with the other side and their own thoughts and feelings in the process. The results are a current society that is a living paradox, one that has a firmer grasp on how the Universe began than before along with the tools required to make this possible, while at the same time remaining focused on our home world, our baser immediate needs, and holding onto beliefs which our ancient forbearers would still recognize.
Can the two sides be reconciled before our society is presumably wrecked by the cultural clash, and if so, how?
In 2011, Yale University Press released a book titled The New Universe and the Human Future: How a Shared Cosmology Could Transform the World. The authors of this work are Nancy Ellen Abrams and Joel R. Primack, both professors at the University of California, Santa Cruz, who also happen to be a married couple.
As the subtitle of their work states, Abrams and Primack think that a “shared cosmology” could break this conflict our species is currently in: If we would all just agree on the origin and composition of the Cosmos as stated by modern science, and especially our place in it all, we will not only save ourselves but become truly universal beings with unlimited horizons and a renewed and vibrant sense of being, one that van Gogh with his need for religion via the celestial realm might have found comforting.
Image: The Carina Nebula in visible light. Credit: NASA.
So, do the authors have The Answer to Life, the Universe, and Everything Else? Well… like the world in which we reside, the results are at once both clear and more complex than a single resolution can provide.
The core of the concern held by Abrams and Primack – that industrial humanity has gotten away from its original ancestral views of the heavens and needs to reconnect with its cultural roots in order to truly make it in the Universe – is one I have long agreed with. Science via technology may know far more about the true makeup and actions of the stars and other worlds in space than our ancestors could even imagine, but modern civilization and its various trappings have also made many of us less aware of what goes on in the sky than our forbearers.
This disconnect has brought us to a strange state where we have the knowledge and ability to literally reach the stars, yet only a fraction of the resources and funding from our civilization goes to space exploration and science education. This has also led us to still act as if Earth is the focal point of existence and will somehow continue to sustain humanity even as we are now over seven billion in number and climbing literally every second. In essence, many individuals are intellectually aware of our true place in the Cosmos, but culturally we are still in the huts and caves, distracted into thinking otherwise by the smooth surfaces and shiny toys in those dwellings.
With The New Universe, Abrams and Primack make a mighty and interesting intellectual effort to explain our long history with the Cosmos and reconnect us with the heavens through modern science with some religious symbolism and ideas that simultaneously try not to turn science into yet another religion in the process. This effort is an outgrowth of their earlier collaborative book, The View from the Center: Discovering Our Extraordinary Place in the Cosmos (Riverhead Books, New York, 2006), and based on their participation in the Terry Lecture Series at Yale University in October of 2009.
The authors recognize that for as much as we have evolved in knowledge and technology since first emerging from the trees and savannahs several million years ago, our biology is still deeply connected to those tribal ancestors rooted in small communities and seeing the world as both infused and controlled by the supernatural.
We are still very much social animals, loyal to the views and beliefs of our groups, which vary across the planet. Abrams and Primack not only want to unite these disparate views through modern cosmology – the Universe started with the Big Bang, almost all of the Cosmos is composed of Dark Matter and Dark Energy – but they want it done NOW.
Their urgency comes from the view that the Twenty-First Century is a pivotal point in human history. We have the comprehension and the ability to know how existence really works and the means to lift ourselves out of the tribal mindset that is eating away at our planet’s resources and wrecking Earth’s environment. However, we only have so long to use our modern skills and tools before civilization loses its literal and collective fuel along with its focus, falling into a Dark Age that our descendants may never truly recover from. Or perhaps we may even drop all the way to the extinction of our species, taking many other living residents of this planet along with us.
I tend to agree with the authors of The New Universe that we are on the edge of either greatness or doom with our global society. I think that before the end of this century, humanity has to shed those ancient cultural and even instinctual views and behaviors which make us continue to act like we are still in little disconnected villages where the collective view of the world ends at our local horizons and warring on other groups will only have consequences for the enemy. We also need to be more aware of the potential threats from beyond Earth as well, such as from the planetoids and comets that wander out Sol system which could one day strike our world and cause devastation on a global scale.
This edge we are perched upon may not have enough leeway to allow us to wake up only when impending disaster appears. Would we be able to build a Worldship to conduct a celestial rescue of at least a portion of our species, for example, if most people remain ignorant of what is in the Universe and disconnected from it and have failed to support an infrastructure in space which would be required for the construction and operation of a giant vessel for carrying many humans safely across the Milky Way galaxy for thousands of years?
One beef I have with The New Universe is their attitude towards extraterrestrial life, especially the intelligent kind. It is clear that Abrams and Primack are in the camp that says Earth may harbor the only intelligent life in all of existence (or at least this Universe), although they throw in the word “possibly” and its proper variations each time the subject of its reality is mentioned. As with the Rare Earth folks, they too think that simple organisms may dwell on many worlds throughout space, but as life becomes more complex, so too the odds of it happening, until biological evolution comes to the human species, where the odds of making more than one version of us on another planet seem astronomical – or so they claim.
Image: Our place in the Universe. Credit: Yale University.
I get the distinct feeling that Abrams and Primack deliberately downplay the possibility for ETI to keep the focus on our species and civilization, which they already feel has had so many cosmic demotions in the last few centuries that the one which says we are just one of many intelligences in the Universe might somehow bring us down socially – despite the fact that the idea of aliens of all types has been an integral part of human society for generations now. While these fictional beings are often lacking in strong scientific integrity, they are part of our culture and they have created a level of cosmic awareness that likely did not exist in prehistoric times.
While it is true that we have no present scientific proof of extraterrestrial life and that any ETI which do exist are probably many light years from Earth, it does not help the cause of the authors to downgrade the possibility of life elsewhere, especially if they are serious about humanity becoming truly cosmically aware. The level of awareness they are asking for goes beyond just taking care of our planet. It means that our curiosity, drive, and even survival will cause us to move first beyond our home world and eventually our planetary system into the wider galaxy. Our knowledge of what exists among the 400 billion other star systems of the Milky Way contains many serious gaps, including the amount and types of alien life. ETI may or may not be an immediate concern for our species, but as students of the Universe, Abrams and Primack should know better than to dismiss something that could have a major effect on humanity in one form or another.
In regards to their views on ETI and the recent Centauri Dreams article on the hypothetical intelligence of stars, the authors discussed this subject and the possibility of galaxies and even the Universe as living entities in the FAQ chapter, which was clearly honed from the Q&A portions of their lectures and earlier book. Their answer is that galaxies are too large to be intelligent, in that it would take many thousands of years for the stars to communicate among themselves and millions of years for galaxies to talk to each other, assuming their thought waves or equivalents move no faster than light speed.
For those who wonder exactly who this book is for, the authors have said that it is essentially for everyone, while Primack also declared in one interview that The New Universe is aimed at the high school student both literally and intellectually. With the study of the heavens often being a great intellectual equalizer, educated folks of almost all ages who may be novices when it comes to astronomy and history – or who need some educational refreshers or just want our cosmological history presented in a concisely written package – will also find this work quite useful.
The fact that The New Universe is deliberately not some dry recitation of astronomy and history, makes a noble effort to reconcile the two cultures as defined by C. P. Snow, and implores its participants to care for our planetary home may ironically alienate some readers; however, the book’s title makes it clear up front what one is getting into, so the choice – just as it is with humanity when it comes to our place in the Cosmos – is ultimately yours.
The companion Web site for The New Universe, which includes among the information video presentations made specifically for the book, is here.
Summer Comes to Green Town
Summer in Green Town, Illinois back in 1928 opened like this:
“It was a quiet morning, the town covered over with darkness and at ease in bed. Summer gathered in the weather, the wind had the proper touch, the breathing of the world was long and warm and slow. You had only to rise, lean from your window, and know that this indeed was the first real time of freedom and living, this was the first morning of summer.”
Thus the beginning of Ray Bradbury’s Dandelion Wine, which I re-read not long after the author’s death. With catastrophic fires in the American west and triple-digit heat along the Atlantic seaboard, summer has indeed come, and so has a brief summer holiday for Centauri Dreams. Although I won’t have months ahead of me the way Bradbury’s character Douglas Spaulding did, I am looking forward to a week off. This site is now approaching its eighth anniversary and I’m ready for a break, one that will give me time to catch up on reading, do necessary work around the house, and take care of a couple of speaking engagements. I also plan to have some time to do nothing but put my feet up and relax.
“The bleak mansions across the town ravine opened baleful dragon eyes. Soon, in the morning avenues below, two old women would glide their electric Green Machine, waving at all the dogs. “Mr. Tridden, run to the carbarn!” Soon scatting hot blue sparks above it, the town trolley would sail the rivering brick streets.”
It’s not 1928 anymore, but Bradbury somehow makes that seem irrelevant. And although I’m certainly not twelve like Douglas Spaulding, a July morning with thunderstorms brewing takes me right back to how it felt. Expect the next Centauri Dreams post on July 9, one week from today. I’ll keep an eye on the site and will moderate comments when possible. Otherwise, for the next week I’ll be disappearing into Green Town. See you soon.
Private Funding for Asteroid Telescope
Asteroids are certainly having their moment in the press, what with the combined attention being paid first to Planetary Resources and its plans for asteroid mining, and now the B612 Foundation, with a plan that in some ways tracks the Planetary Resources model. As announced yesterday, B612 intends to build a space telescope using private funding and launch it into a Solar orbit, from which it can carry out discovery and mapping operations targeting asteroids that might pose a threat to the Earth. You’ll recall that Planetary Resources also has an ambitious agenda in terms of developing a series of small space telescopes.
NASA, it’s true, is already searching for Earth-crossing asteroids, and between ground-based efforts and space-borne missions like the Wide-Field Infrared Survey Explorer, thousands of asteroids that pass near the Earth have been discovered. But what the B612 Foundation is calling Sentinel will be dedicated to finding the smaller objects whose effect could still be catastrophic. I see that Ed Lu, a seasoned astronaut who is now chairman and CEO of the Foundation, has the most recent impact in mind when he describes the mission:
“The orbits of the inner solar system where Earth lies are populated with a half million asteroids larger than the one that struck Tunguska (June 30, 1908), and yet we’ve identified and mapped only about one percent of these asteroids to date. During its 5.5-year mission survey time, Sentinel will discover and track half a million Near Earth Asteroids, creating a dynamic map that will provide the blueprint for future exploration of our Solar System, while protecting the future of humanity on Earth.”
Image: Fallen trees at Tunguska, in a photo taken in 1927, long after the event. Credit: Wikimedia Commons.
Tunguska was, of course, a catastrophe we dodged, but only because it fell in a relatively unpopulated area of Siberia. Theories differ as to exactly what the object was, but whatever struck this remote region created the largest impact event in recorded history. The explosion knocked down trees over an area covering 2150 square kilometers. We can only imagine what would happen if an explosion of this size took place over a large metropolitan area.
Thus the 5.5-year mission of Sentinel, to be built by Ball Aerospace and the team behind the Spitzer and Kepler space telescopes. The plan is to catalog 90 percent of the asteroids larger than 140 meters, with the capability of discovering objects as small as 30 meters in diameter. As to Tunguska-sized objects (40-meters wide), B612 thinks it can find 50 percent of them.
The 1.5 ton telescope works in the infrared with a 50-centimeter mirror, with survey operations to scan the entire night half of the sky every 26 days to identify moving objects. Sentinel will orbit between Earth and Venus, scanning the skies near the Earth’s orbit with the Sun at its back. After a five year period of development and testing, launch aboard a SpaceX Falcon 9 is expected in 2017-2018.
Image: Projected orbit for Sentinel. Credit: B612 Foundation.
The man most identified with the B612 Foundation is Apollo 9 astronaut Rusty Schweickart, who founded it and now serves as chairman emeritus. Says Schweickart:
“For the first time in history, B612’s Sentinel Mission will create a comprehensive and dynamic map of the inner solar system in which we live – providing vital information about who we are, who are our neighbors, and where we are going. We will know which asteroids will pass close to Earth and when, and which, if any of these asteroids actually threaten to collide with Earth. The nice thing about asteroids is that once you’ve found them and once you have a good solid orbit on them you can predict a hundred years ahead of time whether there is a likelihood of an impact with the Earth.”
Even better is the fact that getting to a dangerous asteroid in plenty of time — a decade or more is preferable — leaves us with a variety of options for deflecting its course, something we’d have little time to manage in cases like that of the recent close pass by asteroid 2012 LZ1, which turned out to be fully a kilometer wide and made its approach scant days after its discovery. The more eyes on the sky the better, for the deflection options, studied by the B612 Foundation itself ever since its founding in 2002, include slow-acting trajectory changers like ‘gravity tractors,’ in which a spacecraft deflects the object using only its gravitational field as it orbits the asteroid.
What lightens the hearts of space enthusiasts is the fast pace of development for projects like these now that commercial launches are becoming a reality. Sentinel will be able to take advantage of advances in computing as well as our accumulated experience with infrared sensing, but it wouldn’t be in the cards if it weren’t for the launch capability provided by the Falcon 9. It also relies on the combined efforts of scientists, entrepreneurs and venture capitalists, along with the individual contributions needed to raise the several hundred million dollars needed. Speaking of which, the B612 Foundation donation page is open for business.
It’s interesting to put the fund-raising effort in the context of other attempts to fund major projects, as Ed Lu did when talking to Alan Boyle before the news conference announcing Sentinel in San Francisco. Boyle discussed the matter in his Cosmic Log column:
Lu pointed out that the estimated cost of the mission, amounting to a few hundred million dollars, was comparable to the cost of building a performing arts center, a museum, or a planetarium like the one where today’s briefing was being held. The San Francisco Museum of Modern Art, for example, has raised more than $437 million in its current capital campaign. “There are 50 to 100 projects larger than ours going on at any time in the United States, and nobody bats an eye,” he said.
And as Lu went on to recall, some of the observatories that are at the heart of astronomy’s history were built with private financing, including the Lick Observatory, the Keck Observatory and Palomar. The guess here, given our crowd-source mentality in a time of government cutbacks, is that the B612 Foundation will indeed raise enough money to fly this mission, serving as a precedent for other such efforts. The Planetary Society’s LightSail comes to mind, but private and commercial space efforts of all kinds are clearly on a fast upward trajectory.
Measuring Non-Transiting Worlds
Although I want to move on this morning to some interesting exoplanet news, I’m not through with fusion propulsion, not by a long shot. I want to respond to some of the questions that came in about the British ZETA experiment, and also discuss some of Rod Hyde’s starship ideas as developed at Lawrence Livermore Laboratory in the 1970s. Also on the table is Al Jackson’s work with Daniel Whitmire on a modified Bussard ramjet design augmented by lasers. But I need to put all that off for about a week as I wait for some recently requested research materials to arrive, and also because next week I’m taking a short break, about which more on Monday.
For today, then, let’s talk about an advance in the way we study distant solar systems, for we’re finding ever more ingenious ways of teasing out information about exoplanets we can’t even see. The latest news comes from the study of Tau Boötis b, a ‘hot Jupiter’ circling its primary — a yellow-white dwarf about 20 percent more massive than the Sun — with an orbital period of 3.3 days. An international team has been able to measure the mass of this planet even though it is not a transiting world. The work, published in Nature and augmented with another paper in Astrophysical Journal Letters, opens up a new way to study not just the mass of exoplanets but also their atmospheres, whose signature is a key part of the work.
Image: This image of the sky around the star Tau Boötis was created from the Digitized Sky Survey 2 images. The star itself, which is bright enough to be seen with the unaided eye, is at the centre. The spikes and coloured circles around it are artifacts of the telescope and photographic plate used and are not real. The exoplanet Tau Boötis b orbits very close to the star and is completely invisible in this picture. The planet has only just been detected directly from its own light using ESO’s VLT. Credit: ESO/Digitized Sky Survey 2.
51 light-years away in the constellation of Boötes (the Herdsman), Tau Boötis b was discovered by Geoff Marcy and Paul Butler in 1996 through radial velocity methods, which measure the gravitational tug of the planet on its host star. Picking up the stellar ‘wobble’ flags the presence of a planet but leaves us with a wide range of mass possibilities because the angle of the planet’s orbit around the star is unknown. Thus a gas giant at a high angle to the line of sight could show the same signature as a smaller planet at a lower angle. For that reason, we’ve been limited with radial velocity to setting just a lower limit to a planet’s mass.
Transits work better for determining mass because we can measure the lightcurve of the planet as the star’s light dips during the transit, adding that to the radial velocity findings to work out both mass and radius. We’ve also been able to study exoplanet atmospheres in transiting worlds, looking at the star’s light and subtracting out the atmospheric signature. But transiting worlds are uncommon, dependent on the chance alignment of the system with our line of sight. What this new work provides is a way to study non-transiting worlds at a higher level of detail, down to investigating the composition of their atmosphere. Future telescopes should be able to apply these techniques far beyond the realm of hot Jupiters like Tau Boötis b.
What Matteo Brogi (Leiden University) and team did was to use the high-resolution CRIRES spectrograph on the Very Large Telescope at the European Southern Observatory’s Paranal Observatory in Chile to study the light from this system and determine the exquisitely fine changes in wavelength caused by the motion of the planet around the star. The observations at near infrared wavelength (2.3 microns) worked with the signature of carbon monoxide in the atmosphere, which allowed the researchers to work out the angle (44 degrees) that Tau Boötis b orbits the primary. Brogi, lead author of the paper on this work, comments:
“Thanks to the high quality observations provided by the VLT and CRIRES we were able to study the spectrum of the system in much more detail than has been possible before. Only about 0.01% of the light we see comes from the planet, and the rest from the star, so this was not easy.”
The hope is that the technique can be used in future studies to look for molecules associated with life. We’re a long way from that result, but this first step tell us how exciting the era of the new giant observatories — think the European Extremely Large Telescope and its ilk — is going to be. Tau Boötis b turns out to be about six times as massive as Jupiter, as determined through the displacement of the spectral lines of the detected carbon monoxide, and the team intends to look for other molecules in its atmosphere as the studies continue. Larger instruments will allow us to move far beyond the limited range of transiting worlds to tighten our knowledge of distant exoplanet systems, a step forward in the refinement of radial velocity techniques.
The paper is Brogi et al., “The signature of orbital motion from the dayside of the planet τ Boötis b,” Nature 486 (28 June 2012), pp. 502-504 (abstract). See also Rodler et al., “Weighing the Non-Transiting Hot Jupiter τ Boo b,” Astrophysical Journal Letters Vol. 753, No. 1 (2012), L25 (abstract). A news release from the European Southern Observatory is also available, as is this release from the Carnegie Institution for Science. Thanks to Antonio Tavani for the pointer to this work.
Fusion and the Starship: Early Concepts
Having looked at the Z-pinch work in Huntsville yesterday, we’ve been kicking around the question of fusion for propulsion and when it made its first appearance in science fiction. The question is still open in the comments section and I haven’t been able to pin down anything in the World War II era, though there is plenty of material to be sifted through. In any case, as I mentioned in the comments yesterday, Hans Bethe was deep into fusion studies in the late 1930s, and I would bet somewhere in the immediate postwar issues of John Campbell’s Astounding we’ll track down the first mention of fusion driving a spacecraft.
While that enjoyable research continues, the fusion question continues to entice and frustrate anyone interested in pushing a space vehicle. The first breakthrough is clearly going to be right here on Earth, because we’ve been working on making fusion into a power production tool for a long time, the leading candidates for ignition being magnetic confinement fusion (MCF) and Inertial Confinement Fusion (ICF). The former uses magnetic fields to trap and control charged particles within a low-density plasma, while ICF uses laser beams to irradiate a fuel capsule and trap a high-density plasma over a period of nanoseconds. To be commercially viable, you have to get a ratio of power-in to power-out somewhere around 10, much higher than breakeven.
Image: The National Ignition Facility at Lawrence Livermore National Laboratory focuses the energy of 192 laser beams on a target in an attempt to achieve inertial confinement fusion. The energy is directed inside a gold cylinder called a hohlraum, which is about the size of a dime. A tiny capsule inside the hohlraum contains atoms of deuterium (hydrogen with one neutron) and tritium (hydrogen with two neutrons) that fuel the ignition process. Credit: National Ignition Facility.
Kelvin Long gets into all this in his book Deep Space Propulsion: A Roadmap to Interstellar Flight (Springer, 2012), and in fact among the books in my library on propulsion concepts, it’s Long’s that spends the most time with fusion in the near-term. The far-term possibilities open up widely when we start talking about ideas like the Bussard ramjet, in which a vehicle moving at a substantial fraction of lightspeed can activate a fusion reaction in the interstellar hydrogen it has accumulated in a huge forward-facing scoop (this assumes we can overcome enormous problems of drag). But you can see why Long is interested — he’s the founding father of Project Icarus, which seeks to redesign the Project Daedalus starship concept created by the British Interplanetary Society in the 1970s.
Seen in the light of current fusion efforts, Daedalus is a reminder of how massive a fusion starship might have to be. This was a vehicle with an initial mass of 54,000 tonnes, which broke down to 50,000 tonnes of fuel and 500 tonnes of scientific payload. The Daedalus concept was to use inertial confinement techniques with pellets of deuterium mixed with helium-3 that would be ignited in the reaction chamber by electron beams. With 250 pellet detonations per second, you get a plasma that can only be managed by a magnetic nozzle, and a staged rocket whose first stage burn lasts two years, while the second stage burns for another 1.8. Friedwardt Winterberg’s work was a major stimulus, for it was Winterberg who was able to couple inertial confinement fusion into a drive design that the Daedalus team found feasible.
I should mention that the choice of deuterium and helium-3 was one of the constraints of trying to turn fusion concepts into something that would work in the space environment. Deuterium and tritium are commonly used in fusion work here on Earth, but the reaction produces abundant radioactive neutrons, a serious issue given that any manned spacecraft would have to carry adequate shielding for its crew. Shielding means a more massive ship and corresponding cuts to allowable payload. Deuterium and helium-3, on the other hand, produce about one-hundredth the amount of neutrons of deuterium/tritium, and even better, the output of this reaction is far more manipulable with a magnetic nozzle. If, that is, we can get the reaction to light up.
It’s important to note the antecedents to Daedalus, especially the work of Dwain Spencer at the Jet Propulsion Laboratory. As far back as 1966, Spencer had outlined his own thoughts on a fusion engine that would burn deuterium and helium-3 in a paper called “Fusion Propulsion for Interstellar Missions,” a copy of which seems to be lost in the wilds of my office — in any case, I can’t put my hands on it this morning. Suffice it to say that Spencer’s engine used a combustion chamber ringed with superconducting magnetic coils to confine the plasma in a design that he thought could be pushed to 60 percent of the speed of light at maximum velocity.
Spencer envisaged a 5-stage craft that would decelerate into the Alpha Centauri system for operations there. Rod Hyde (Lawrence Livermore Laboratory) also worked with deuterium and helium-3 and adapted the ICF idea using frozen pellets that would be exploded by lasers, hundreds per second, with the thrust being shaped by magnetic coils. You can see that the Daedalus team built on existing work and extended it in their massive starship design. It will be fascinating to see how Project Icarus modifies and extends fusion in their work.
The Z-pinch methods we looked at yesterday are a different way to ignite fusion in which isotopes of hydrogen are compressed by pumping an electrical current into the plasma, thus generating a magnetic field that creates the so-called ‘pinch.’ Jason Cassibry, who is working on these matters at the University of Alabama at Huntsville, is one of those preparing to work with the Decade Module 2 pulsed-power unit that has been delivered to nearby Redstone Arsenal. Let me quote what the recent article in Popular Mechanics said about his thruster idea:
Cassibry says the acceleration of such a thruster wouldn’t pin an astronaut to the back of his seat. During shuttle liftoff, rocket boosters generate a thrust of about 32 million newtons. In contrast, the pulsed-fusion system would generate an estimated 10,000 newtons of thrust. But rocket fuel burns out quickly while pulsed-fusion systems could keep going at a “slow” but steady 24 miles per second. That’s about five times faster than a shuttle drifting around in Earth orbit.
A slow but steady burn like this would be a wonderful accomplishment if it can be delivered in a package light enough to prove adaptable for spaceflight. Given all the background we’ve just examined — and the continuing research into both MCF and ICF for uses here on Earth — I’m glad to see the Decade Module 2 available in Huntsville, even though it may be some time before it can be assembled and the needed work properly funded. Because while we’ve developed theoretical engine designs using fusion, we need to proceed with the kind of laboratory experiments that can move the ball forward. The Z-pinch machine in Huntsville will be a useful step.
Z-Pinch: Powering Up Fusion in Huntsville
The road to fusion is a long slog, a fact that began to become apparent as early as the 1950s. It was then that the ZETA — Zero-Energy Toroidal (or Thermonuclear) Assembly — had pride of place as the fusion machine of the future, or so scientists working on the device in the UK thought. A design based on a confinement technique called Z-pinch (about which more in a moment), ZETA began operations in 1957 and began producing bursts of neutrons, thought to flag fusion reactions in an apparent sign that the UK had taken the lead over fusion efforts in the US.
This was major news in its day and it invigorated a world looking for newer, cheaper sources of power, but sadly, the results proved bogus, the neutrons being byproducts of instabilities in the system and not the result of fusion at all. Fusion has had public relations problems ever since, always the power source of the future and always just a decade or two away from realization. But of course, we learn from such errors, and refined pinch concepts — in which electric current induced into a plasma causes (via the Lorenz force) the plasma to pinch in on itself, compressing it to fusion conditions — continue to be explored.
Image: The ZETA device at Harwell. The toroidal confinement tube is roughly centered, surrounded by a series of stabilizing magnets (silver rings). The much larger peanut shaped device is the magnet used to induce the pinch current in the tube. Credit: Wikimedia Commons.
In today’s Z-pinch work, current to the plasma is provided by a large bank of capacitors, creating the magnetic field that causes the plasma to be pinched into a smaller cylinder to reach fusion conditions (the axis of current flow is called the z axis, hence the name). Here we can think of two major facilities used in nuclear weapons effects testing in the defense industry as well as in fusion energy research: The Z Machine located at Sandia National Laboratories in New Mexico and the MAGPIE pulsed power generator at Imperial College, London. And lately a Z-pinch machine called a Decade Module Two has made the news.
As explained by an article in The Huntsville Times back in May, researchers at Marshall Space Flight Center and their colleagues at the University of Alabama at Huntsville will have a Decade Module Two (DM2) at their disposal once they finish the process of unloading and assembling the house-sized installation at Redstone Arsenal. Originally designed as one of several modules to be used in radiation testing, the DM2 was the prototype for a larger machine, but even this smaller version required quite an effort to move it, as can be seen in this Request for Proposal issued back in August of 2011, which laid out the dismantling and move from L-3 Communications Titan Corporation in San Leandro, CA.
The DM2 got a brief spike in the press as news of the acquisition became available, but note that the 60-foot machine is not expected to be powered up any earlier than 2013 and will not reach break-even fusion when it does. But this pulsed-power facility should be quite useful as engineers test Z-pinch fusion techniques and nozzle systems that would allow the resulting plasma explosions to be directed into a flow of thrust to propel a spacecraft. Z-pinch and related ignition methods have been under study for half a decade, but Huntsville’s DM2 may move us a step closer to learning whether pulsed fusion propulsion will be practical.
Image: Z-pinch engine concept. Credit: NASA.
The fusion power effort includes not just MSFC and UAH but Boeing as well. Jason Cassibry (UAH) talks about its ultimate goal as being a lightweight pulsed fusion system that could cut the travel time to Mars down to six to eight weeks, and he’s quoted in this story in Popular Mechanics as saying that “The time is perfect to reevaluate fusion for space propulsion.” Working the kinks out of Z-pinch would be a major contribution to that effort, and we can hope the DM2 installation may lead to the design and testing of actual thrusters, though right now we’re still early in the process.
The Popular Mechanics article goes on to explain Z-pinch’s propulsion possibilities this way:
Cassibry imagines attaching a large reactor on the back of a human transport vessel. Similar to how the piston of a car compresses fuel and air in the engine, the reactor would use electrical and magnetic currents to compress hydrogen gas. That compression raises temperatures within the reactor up to 100 million degrees C—hot enough to strip the electrons off of hydrogen atoms, create a plasma, and fuse two hydrogen nuclei together. In the process of fusing, the atoms release more energy, which keeps the reactor hot and causes more hydrogen to fuse and release more energy. (These reactions occur about 10 times per second, which is why it’s “pulsed.”) A nozzle in the reactor would allow some of the plasma to rush outward and propel the spacecraft forward.
There aren’t many machines that can produce the power demanded by pulsed fusion experiments and Centauri Dreams wishes the DM2 team success not only at the tricky business of Z-pinch fusion experimentation but the even trickier challenge of funding deep space propulsion research. None of that will be easy, but if we can get to the stage of testing a magnetic nozzle for a pulsed fusion engine using the DM2 we’ll be making serious headway. Right now the work proceeds one step at a time, the first being to get the DM2 up and running.
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