by Paul Gilster | Mar 18, 2011 | Missions |
by Andreas Tziolas
After a 15 minute main thruster burn early this morning (UTC), the MESSENGER spacecraft is now in orbit around Mercury. Congratulations to the entire MESSENGER team. As we look forward to much more from Mercury, I want to turn today’s session over to Andreas Tziolas, for some thoughts on the mind-bending process of designing an interstellar spacecraft. Dr. Tziolas is a theoretical physicist and spacecraft engineer, currently serving as the Deputy Project Leader of Project Icarus. In his recent PhD (2009), he explored cosmologies resulting from brane collisions in string theory. He is currently the chief scientist for Variance Dynamical, an electronics prototyping company in Anchorage, Alaska developing radiation hardened electronics for use in space exploration. In this article, Dr. Tziolas talks to us about the legend of Icarus and offers some personal reflections from his experience as a part of the inspirational Project Icarus design team.
There have been many projects and collaborations inspired by the dramatic flight of Icarus. A young boy adorns wings made of sticks and wax to soar to the heavens together with his father, Daedalus. As legend would have it, the young boy elated by the sensation of flight decides to push the limits of his father’s creation and, ignoring his warnings, flies higher and higher until the Sun’s radiant beams melt the wax with which his wings were held together and he falls helpless to the ocean, never to be seen again.
The story is quite tragic and brief. There is no need for eloquence in conveying it, nor have I ever searched out the complete telling of the tale. For one I have never felt the need to, perhaps because any retelling would only contradict and confuse its personal meaning to me. I believe it’s a tale of a boy that looked up to his father, an accomplished scientist who managed to fulfill man’s ageless dream of flying. Young Icarus must have grown up carefully observing his parents thinking how one day, he will surpass them, make them proud, go further and higher than they ever could. And so he did.
The tale is then a story of a young man coming of age. In that all important moment of revolt, he disobeys his father and pushes ahead, a man now, flying far above his father, ever climbing higher and higher, tasting freedom and independence as he climbed to touch the Sun. I believe Icarus would have kept on going until he found a new sky, far up and into space where he may have paused to regard the stars before returning to Earth to tell his father all about it.
Pushing Past the Boundaries
Having been part of Project Icarus since its inception, I have come to realize how many of our designers share the spirit of this young boy of legend. We may not all have the genius of our father, Daedalus but we are intent to push the boundaries of science and technology to make a contemporary plausible reference design from which humanity might one day construct the vessel to voyage to the stars. Like so many others, we stand on the shoulder of giants – the inspirational Project Daedalus team, who were the first to piece together the sticks and rope and wax wings – to show us how the seemingly impossible was merely difficult. The British Interplanetary Society has the richest history, amongst all space organizations ever, for supporting those ideas which matter – the ideas which inspire. We are proud to be descended from that same house.
Image: The Project Daedalus design, as developed by the British Interplanetary Society in the 1970’s. Credit: Adrian Mann.
I feel fortunate that my path in life led me to being a part of this project; to have become a physicist, inspired by all those science fiction movies and books and to have made some small contribution to science. I have also seen, with great disappointment, those sometimes more capable than me, move away from that which inspired them – sometimes even looking down with contempt at notions of starships, planetary terraforming and faster-than-light travel. Somewhere along the way that special fire went out, perhaps because it seemed too difficult or science did not yet have the faculty to clearly provide a path towards such accomplishments.
So now a group of volunteers decide to hoist themselves up onto the shoulders of those intellectual giants and take on the most challenging of space endeavors. Designing a starship is difficult business. Managing a team of international volunteers and keeping the project on track is, as it turns out, a fairly interesting story in itself.
Making Icarus Happen
First and foremost, we are all volunteers which means of course we are not being paid for our work. The amazing consensus amongst the team however, is that any contribution we make towards advancing mankind to the stars is sufficient reward. As such we have come to expect the highest quality of scientific work from each other which is ensured through a rigorous internal review process. Trade studies, research notes and papers are first published internally and are subject to the highest level of academic and professional scrutiny.
In this process disagreements are a natural occurrence, the resolution of which is usually orchestrated by the Project Leader (PL), the Deputy Project Leader (DPL) and the Core Design Team, which is comprised of those who have proven their worth to their team through their dedication and quality of work. In other research organizations, conflicts are resolved either by deferring to a higher authority or by an appropriate democratic process and vote. In Project Icarus neither are appropriate, since volunteers can neither be fired, nor disciplined since any work contributed has been done with significant personal investment. The democratic method is also meaningless, since a panel of experts in interstellar engineering would be required, which doesn’t exist anywhere in the world. It would seem that Project Icarus has reinvented an almost forgotten process of conflict resolution, which is done through respect and reason. Discussions are respectfully conducted at all times, the resolution of which relies solely on what is reasonable. These reasonable technical decisions are steering the design process towards a plausible spacecraft design which is essential to establishing our credibility.
And what about motivation? How do you motivate someone to get cracking and study up on the latest antimatter confinement paper, when he or she already works full time and has a family? It is indeed very difficult. Project and Module Leaders must frequently remind designers of deadlines for finishing studies and ask for progress reports. Team performance is tabulated and monitored for studies which are potentially falling behind. Emails to delinquents are written in a strange tone which somehow combines appreciation for work promised and freely offered with the resounding crack of the whip.
Sometimes management is management, even in Project Icarus, but for the most part yet another fascinating phenomenon tends to align the team with our research objectives. You see, everyone on the team is a scientist of sorts. OK, so yes, everyone is one or another sort of geek. Some are computer geeks, others technology geeks, sci-fi geeks, rocketry geeks, etc, etc the list goes on. On occasion designers will come across something loosely related to an Icarus research study topic while reading their favorite geek-blog and email it to the rest of the team. From the commentary that follows, ideas are formulated which are slowly technically justified and extended resulting in our designers getting excited and motivated. An all important side-effect of this process is that the entire team stays informed of the latest scientific developments, beyond the capacity of any one geek.
Growth of the Project
In the last year, Project Icarus has been steadily growing in popularity through our presentations at conferences in Europe and the USA, paper publications and through articles appearing in scientific magazines and notable websites such as the Discovery Channel. I have noticed that every time we appear in the press, the team rejoices and their research efforts are invigorated. In a sense, this exposure justifies the long hours of work that is being poured into the project.
I know for a fact several of our designers are people that have been working on the problem of interstellar flight for many years, training themselves by carefully monitoring technological innovations and scientific articles for small pieces of the puzzle. For most of us, not lucky enough to be working for NASA or a distinguished university with a space research group, we are still left with that feeling of looking in from the window, regardless of how many papers we read on Magnetic Confinement Fusion in our free time. Project Icarus is a home, or a docking station if you will, to all those dedicated thinkers.
Image: Daedalus arrives at its target, Barnard’s Star. Credit: Adrian Mann.
There are certainly many many other organizations inspired by space out there, like the Mars Society for instance, but that’s Bob Zubrin’s dream. Wouldn’t it be nice to join a group of like minded people who like you, are willing to put 5 years of concerted effort into designing a starship or a lunar research station or a space elevator? Sure there are some aspiring companies out there which have worked hard to get funded to do that kind of research, but they don’t have to be the only ones.
In the same way we create our man-caves and mom-caves – our little corners of heaven in our garage where we can work on small but fulfilling microelectronics or woodworking projects, we could also band together, get organized and allow ourselves to become a cog in a great machine that builds dreams out of science. I wonder what the world would look like if we all got up in the morning and went to our regular jobs in our offices and worksites, came home, had some dinner, watched some TV, played with the kids and then sat down in front of the computer to work on the designs of a starship or satellite. This is not the first time someone had this idea, nor am I saying that this is something new. Wikipedia was built from the community and a truly excellent job has been done. Others are now finding ways to motivate what are being called “crowd-sourcing” projects, where the content is built up from users.
The Real Ending of the Icarus Story
Icarus flew towards the Sun and burned his wings and now Project Icarus is designing a starship to fly to a nearby Star. “What an unfortunate choice of name!”, most people tell us. Maybe I watch too many movies, but I don’t believe the legend is complete and that there is more to the tale of Icarus, either lost through the ages or just waiting for ages to be told.
I believe that, like so many heroes that fall off of cliffs and fall into the ocean, Icarus was not lost at sea after his long fall from touching the Sun. Icarus came to on the shore of a Greek beach, exhausted and confused. After searching through the sky for his father for many days and nights, he took pause and collected himself. He started a fire and found he had melted the sand into glass and that the soft clay had become rock. After studying these carefully, he saw the future unfolding and understood his destiny. He meticulously collected materials to slowly build himself a better set of wings made of fabric and steel, working day and night under the hot sun. He did not tire or lose confidence, for he had had the best of teachers, his father Daedalus. And he would not be repeating his mistakes.
If anyone reading this feels motivated, then please feel free to contact Project Icarus. We have a lot of work to be done and we are in need of competent scientists. We believe that everyone brings something new to the project and the least you will get in return is a profound kinship, a thirst for learning and an interstellar starship with a good name.
by Paul Gilster | Mar 17, 2011 | Exoplanetary Science |
Before I get into today’s story, which is an interesting study on planets around white dwarfs that Andrew Tribick passed along, I want to say a few words about Japan. Centauri Dreams has many, many readers in that country, and the terrible images and stories coming out of there have haunted me these past few days. The suffering of those displaced by the earthquake and tsunami, and the continued problems in resolving the worsening situation at Fukushima, make it hard to focus on any other topic. Speaking for myself here at Centauri Dreams — and I know I speak for the entire Tau Zero Foundation as well — you Japanese readers remain in our thoughts and prayers, and will continue to do so until these great national wounds are healed.
On the space front, today is the day when MESSENGER enters Mercury orbit. Below is the schedule for the events, which we’ll follow closely as orbital insertion occurs.
White Dwarfs and Potential Planets
But for now let’s talk about white dwarfs, those interesting survivors of Sun-like stars that have gone through the red giant phase and presumably swallowed up planets within roughly Earth’s distance from the Sun. An interesting paper from Eric Agol (University of Washington) takes a look at exoplanet possibilities around white dwarfs, and draws some surprising conclusions. We have, of course, searched for habitable planets primarily around stars that are much younger, assuming that a planetary system that had undergone the transformation of a red giant into a white dwarf would be unlikely to provide a suitable home for life. But Agol isn’t so sure.
Remember the process: Stars like the Sun eventually exhaust their nuclear fuel and at some point lose their outer envelope, leaving only the hot core behind. The core, now a hot white dwarf at temperatures exceeding 100,000 Kelvin, will begin a long process of cooling. A typical white dwarf might be half as massive as the Sun, but not much larger than the Earth in size, and as this NASA article points out, that means it’s extremely dense, perhaps 200,000 times as dense as the Earth itself. When it comes to matter, only neutron stars surpass that density.
Agol points out that the most common white dwarfs have surface temperatures in the range of 5000 K, which leads to his calculation that a planet would need to orbit no closer than about 0.01 AU to be at a temperature where liquid water could exist on the surface. What’s intriguing from the standpoint of finding such planets is that a potentially habitable world like this, Earth-sized or even smaller, would in principle be detectable because of the small size of the host star. The white dwarf, in fact, could be completely eclipsed by a habitable planet that orbits it.
But how does a planet survive the preceding red giant phase? One possibility is that new planets could form out of gases near the white dwarf, especially in binary systems where gravitational interactions could play a helpful role. We know of two neutron stars that have planets that conceivably formed from the disk created after a supernova event. Moreover, the pulsar 4U 0142+61 has been shown to have a circumstellar disk thought to have been formed from supernova debris. Planetary capture or migration can’t be ruled out, either.
Defining a Habitable Zone
I’m going to post Agol’s chart on white dwarf habitable zones (WDHZ) below to illuminate what he has to say. Here the habitable zone is plotted against time as a blue-shaded region, and because the white dwarf is cooling, the region shrinks with time. The planet starts off too hot for liquid water, passes through the white dwarf habitable zone, and then becomes too cold for life.
Image: The WDHZ for MWD = 0.6M? vs. white dwarf age and planet orbital distance. Blue region denotes the WDHZ. Dashed line is Roche limit for Earth-density planets. Planets to right of dotted line are in the WDHZ for less than 3 Gyr. Planet orbital period is indicated on the top axis; white dwarf effective temperature on the right axis. Luminosity of the white dwarf at different ages are indicated on right. Credit: Eric Agol.
Using the WDHZ limits, Agol defines a ‘continuously habitable zone’ (CHZ) as a range of orbital distances habitable for a minimum duration. Choosing a minimum duration of 3 billion years produces a continuous habitable zone within 0.02 AU, so we have a three billion year period for the development of life at that distance. The author comments on the consequences:
…the range of white dwarf temperatures in the portion of the CHZ within the WDHZ is that of cool white dwarfs, ? 3000–9000 K (right hand axis in Fig. 1), similar to the Sun. At the hotter end higher ultraviolet flux might affect the retention of an atmosphere, these planets would need to form a secondary atmosphere, as occurred on Earth. Excluding higher temperature white dwarfs only slightly modifies the CHZ since they spend little time at high temperature. Cool white dwarfs are photometrically stable…, which is critical for finding planets around them.
Finding a White Dwarf Planet
An interesting prospect indeed, one that Agol further explores by simulating sky surveys that could find such planets. Among the latter calculations, it’s interesting to note that the GAIA mission will observe 200,000 disk white dwarfs between 50 and 100 times each, making the detection of a white dwarf with a habitable planet a real possibility. Even more likely are the prospects for the Large Synoptic Survey Telescope, a planned wide-field survey in Chile.
And what would life be like on a planet orbiting in the habitable zone of a white dwarf?
The most common white dwarf has Teff [effective temperature] ? 5000 K, close to that of the Sun; consequently, inhabitants of a planet in the CHZ will see their star as a similar angular size and color as we see our Sun. The orbital and spin period of planets in the CHZ are similar to a day, causing Coriolis and thermal forces similar to Earth. The night sides of these planets will be warmed by advection of heat from their day sides if a cold-trap is avoided… Transit probabilities of habitable planets are similar for cool white dwarfs and Sun-like stars, but the white dwarf planets can be found using ground-based telescopes… at a much less expensive price than space-based planet-survey telescopes.
This is a provocative paper, one that jolts us into thinking about habitable zones in places where we hadn’t thought of looking before. Yet as we’re finding in our exoplanet research, the universe keeps yielding surprises, and a habitable planet around a white dwarf may not be so bizarre after all. Does anyone know of any science fiction writers who have tackled such a scenario? If so, do let me know. Agol’s paper is “Transit Surveys for Earths in the Habitable Zones of White Dwarfs,” in press at the Astrophysical Journal Letters and available as a preprint.
Addendum: See the comments below for a link to a discussion of white dwarf planets that I was hitherto unaware of.
by Paul Gilster | Mar 16, 2011 | Missions |
We rarely talk about the inner planets here, and even Mars gets short shrift. That’s because I decided at the outset that because there were so many excellent sites covering planetary exploration — and especially Mars — my only focus within our Solar System would be on the outer planets and, of course, what lies beyond them. But the MESSENGER mission is simply too fascinating to ignore, the first mission to Mercury since Mariner 10 way back in 1974, and beyond that, one of its project scientists is a man I deeply respect, Ralph McNutt (JHU/APL), who in addition to his MESSENGER duties also serves as one of the consultants for the Project Icarus starship design.
In fact, McNutt’s work in regions both near and far from the Sun is voluminous. For MESSENGER, he will be analyzing the planet’s surface composition using data from the spacecraft’s X-Ray Spectrometer and Gamma-Ray and Neutron Spectrometer instruments. But he’s also a co-investigator for the New Horizons mission to Pluto/Charon, works with the Cassini team on the Ion Neutral Mass Spectrometer investigation, acts as a science team member for the Voyager probes, and is actively involved in interstellar probe design, as witness his work on the Innovative Interstellar Explorer mission, a near-term precursor probe to 200 AU.
Image: This high-resolution mosaic of NAC images shows Mercury as it appeared to MESSENGER as the spacecraft departed the planet after the mission’s second flyby of Mercury. This mosaic resembles one of the first images received back at Earth following that flyby, an image that showed for the first time the spectacular rays of Hokusai crater extending great distances across Mercury’s surface. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.
MESSENGER is set to achieve Mercury orbit after a 4.7 billion mile trip that has included fully fifteen trips around the Sun and six planetary flybys. Orbital insertion should be around 0100 UTC on the 18th, marking the first time a spacecraft has orbited the planet. It’s been a long journey not only in miles but in time since MESSENGER launched more than six and a half years ago. Ahead is a year-long science mission as MESSENGER orbits the barren world in an orbit that closes to within 200 kilometers of the planet’s surface. Says APL’s Eric Finnegan:
“For the first two weeks of orbit, we’ll be focused on ensuring that the spacecraft systems are all working well in Mercury’s harsh thermal environment. Starting on March 23 the instruments will be turned on and checked out, and on April 4 the science phase of the mission will begin and the first orbital science data from Mercury will be returned.”
Remember that Mariner 10’s images of Mercury’s surface were made during three flyby maneuvers in 1974 and 1975, but the spacecraft could only send us pictures of one side of the planet. MESSENGER has been filling in the gaps through its own flybys, and now we’ll complete the picture. What’s exciting isn’t just the thrill of making a full study of a little-examined world, but knowing that the more we learn about the geological history, surface composition and other salient facts about Mercury, the more we learn about rocky planets in general, knowledge which we’ll apply as we try to make sense out of the smaller worlds we find around other stars.
Coping with heat will be a major issue for this mission, which is why the spacecraft’s instruments are shielded against the reflection from the planet’s surface. Thermal issues have consequences for the spacecraft’s orbit as well, says Ann Sprague (University of Arizona):
“The spacecraft is going to go very fast, traveling around the planet every 12 hours. The orbit is highly elliptical to allow the spacecraft to cool down. We couldn’t do this with a circular orbit, like around Mars. Everything would just overheat. MESSENGER must swoop in, keeping its sunshade pointed toward the Sun, and then it has to swing out far into space so it can cool down.”
We have much to learn, including the question of whether frozen water may be found beneath dust layers in the permanently shadowed crater bottoms at the poles, the nature of the planet’s exosphere (a thin region of atoms and ions generated by charged particles from the solar wind striking the surface and interacting with elements there), and the question of Mercury’s magnetic field. The planet is small enough (not much larger than the Moon) that it should have solidifed to the core, as this UA news release points out. But the presence of a magnetic field tells us that there may be molten material inside, generating a field MESSENGER will examine closely.
All of this reminds me that Mariner 10’s Mercury travels had ramifications in unexpected ways. Flaking paint from the spacecraft’s high-gain antenna caused problems with its navigation sensors and a disturbed star tracker caused the spacecraft to roll, venting critical attitude control gas. The control team at the Jet Propulsion Laboratory was able to use Mariner 10’s solar panels to adjust the spacecraft’s attitude, an early and striking demonstration of the power of solar photons. These days we’re just entering the era of the solar sail, but it’s worth recalling that the concept was demonstrated much earlier, and in this case, in entirely unanticipated ways.
by Paul Gilster | Mar 15, 2011 | Deep Sky Astronomy & Telescopes |
Having a constant named after you ensures a hallowed place in astronomical history, and we can assume that Edwin Hubble would have been delighted with our continuing studies of the constant that bears his name. It was Hubble who showed that the velocity of distant galaxies as measured by their Doppler shift is proportional to their distance from the Earth. But what would the man behind the Hubble Constant have made of the ‘Hubble Bubble’? It’s based on the idea that our region of the cosmos is surrounded by a bubble of relatively empty space, a bubble some eight-billion light years across that helps account for our observations of the universe’s expansion.
The theory goes something like this: We assume that the Hubble Constant should be the same no matter where it is measured, because we make the larger assumption that our planet does not occupy a special position in the universe. But suppose that’s wrong, and that the Earth is near the center of a region of extremely low density. If that’s the case, then denser material outside that void would attract material away from the center. What we would see would be stars accelerating away from us at a rate faster than the more general expansion of the universe.
The Hubble Bubble is an ingenious notion, one of the ideas advanced as an alternative to dark energy to explain why the expansion of the universe seems to be accelerating. If you had to choose between a Hubble Bubble and a mysterious dark energy that worked counter to gravity, the Bubble would seem a safer choice, given that it doesn’t conjure up a new form of energy, but the observational evidence for the Bubble is lacking, and now the idea has been hobbled by new work by Adam Riess (Space Telescope Science Institute) and colleagues.
Deflating the Bubble
Riess used data from the new Wide Field Camera 3 (WFC3) aboard the Hubble Space Telescope to measure the Hubble Constant to a greater precision than ever before. The value the team arrived at — 73.8 kilometers per second per megaparsec — means that for every additional megaparsec (3.26 million light years) a galaxy is from Earth, it appears to be moving 73.8 kilometers per second faster away from us. The uncertainty over the figure for the universe’s expansion rate in the new observations has now been reduced to just 3.3 percent, reducing the error margin by a full 30 percent over the previous Hubble measurement in 2009.
The new precision is thanks to Wide Field Camera 3, which helps the scientists study a wider range of stars to eliminate systematic errors introduced by comparing the measurements of different telescopes. The team compared the apparent brightness of Type Ia supernovae and Cepheid variable stars to measure their intrinsic brightness and calculate the distances to Type Ia supernovae in distant galaxies. Riess calls WFC3 the best ever flown on Hubble for such measurements, adding that it improved “…the precision of prior measurements in a small fraction of the time it previously took.” Further WFC3 work should tighten the Constant even more, and even better numbers should be within range of the James Webb Space Telescope.
This work is significant because as we tighten our knowledge of the universe’s expansion rate, we restrict the range of dark energy’s strength. The Bubble theory arose because scientists were looking for ways around a dark energy that opposed gravity. But the consequences of a Hubble Bubble are clear — if it’s there, the universe’s expansion rate must be slower than astronomers have calculated, with the lower-density bubble expanding faster than the more massive universe that surrounds it. Riess and team have tightened the Hubble Constant to the point where this lower value — 60 to 65 kilometers per second per megaparsec — is no longer tenable.
Lucas Macri (Texas A&M University), who collaborated with Riess, notes the importance of the study:
“The hardest part of the bubble theory to accept was that it required us to live very near the center of such an empty region of space. This has about a one in a million chance of occurring. But since we know that something weird is making the universe accelerate, it’s better to let the data be our guide.”
Riess, you may recall, is one of the co-discoverers of the universe’s accelerating expansion, having demonstrated that distant Type Ia supernovae were dimmer than they ought to be, an indication of additional distance that had to be the result of faster than expected expansion. Meanwhile, it’s extraordinary to realize how much the Hubble instrument has helped us pin down the value of the Hubble Constant, which had seen estimates varying by a factor of two before the telescope’s 1990 launch. This NASA news release points out that by 1999, the Hubble telescope had refined the value of the Hubble Constant to an error of about ten percent. Riess’ new work continues the 80-year measurement of this critical value and promises more to come.
The paper is Riess et al., “A 3% Solution: Determination of the Hubble Constant with the Hubble Space Telescope and Wide Field Camera 3,” Astrophysical Journal Vol. 730, Number 2 (April 1, 2011). Abstract available.
by Paul Gilster | Mar 14, 2011 | Culture and Society |
All weekend long, as the dreadful news and heart-wrenching images from Japan kept coming in, I wondered how press coverage of the nuclear reactor situation would be handled. The temptation seemed irresistible to play the story for drama and maximum fear, citing catastrophic meltdowns, invoking Chernobyl and even Hiroshima, along with dire predictions about the future of nuclear power. My first thought was that the Japanese reactors were going to have the opposite effect than many in the media suppose. By showing that nuclear plants can survive so massive an event, they’ll demonstrate that nuclear power remains a viable option.
This is an important issue for the Centauri Dreams readership not just in terms of how we produce energy for use here on Earth, but because nuclear reactors are very much in play in our thinking about future deep space missions. Thus the public perception of nuclear reactors counts, and I probably don’t have to remind any of you that when the Cassini orbiter was launched toward Saturn, it was with the background of protest directed at its three radioisotope thermoelectric generators (RTGs) that use plutonium-238 to generate electricity. A similar RTG-carrying mission will doubtless meet the same kind of response.
What the public thinks about nuclear power, then, has a bearing on how we proceed both on Earth and in space. So how are the media doing so far with what is happening in Japan? Josef Oehmen, an MIT research scientist, has some thoughts on the matter. In an essay published yesterday by Jason Morgan, an English teacher and earthquake survivor who blogs from Japan, Oehmen gives us his initial reaction:
I have been reading every news release on the incident since the earthquake. There has not been one single (!) report that was accurate and free of errors (and part of that problem is also a weakness in the Japanese crisis communication). By “not free of errors” I do not refer to tendentious anti-nuclear journalism – that is quite normal these days. By “not free of errors” I mean blatant errors regarding physics and natural law, as well as gross misinterpretation of facts, due to an obvious lack of fundamental and basic understanding of the way nuclear reactors are built and operated. I have read a 3 page report on CNN where every single paragraph contained an error.
Reactor Basics and the Fukushima Story
What to do? Oehmen proceeds to go through the basics about nuclear reactors and in particular those at Fukushima, which use uranium oxide as nuclear fuel in so-called Boiling Water Reactors. Here the process is straightforward: The nuclear fuel heats water to create steam, which in turn drives turbines that create electricity, after which the steam is cooled and condensed back into water that can now be returned for heating by the nuclear fuel. Oehmen’s article, which I recommend highly, walks us through the containment system at these plants.
Image: Reactor design at Fukushima. Credit: BraveNewClimate.
The scientist also makes an obvious point that some in the media should probably take note of. We are not talking about possible nuclear explosions here of the kind that happen when we detonate a nuclear device. For that matter, we’re not talking about a Chernobyl event — the latter was the result of pressure build-up, a hydrogen explosion and, as Oehmen shows, the rupture of the containments within the plant, which drove molten core material into the local area. That’s the equivalent of what’s known as a ‘dirty bomb,’ and the main point of Oehmen’s article is that it’s not happening now in the Japanese reactors and it is not going to happen later.
I won’t go through the entire Fukushima situation here, but instead will send you directly to Oehmen’s essay, which was also reproduced on the BraveNewClimate site with a series of illustrations. But a few salient points: When the earthquake hit, the nuclear reactors went into automatic shutdown, with control rods inserted into the core and the nuclear chain reaction of the uranium stopped. The cooling system to carry away residual heat was knocked out by the tsunami, which destroyed the emergency diesel power generators, kicking in the battery backups, which finally failed when external power generators could not be connected.
This is the stage at which people began to talk about a core meltdown. Here is Oehmen on that scenario:
The plant came close to a core meltdown. Here is the worst-case scenario that was avoided: If the seawater could not have been used for treatment, the operators would have continued to vent the water steam to avoid pressure buildup. The third containment would then have been completely sealed to allow the core meltdown to happen without releasing radioactive material. After the meltdown, there would have been a waiting period for the intermediate radioactive materials to decay inside the reactor, and all radioactive particles to settle on a surface inside the containment. The cooling system would have been restored eventually, and the molten core cooled to a manageable temperature. The containment would have been cleaned up on the inside. Then a messy job of removing the molten core from the containment would have begun, packing the (now solid again) fuel bit by bit into transportation containers to be shipped to processing plants. Depending on the damage, the block of the plant would then either be repaired or dismantled.
Nuclear After-Effects
So much for mushroom clouds over Fukushima. Oehmen’s article refers primarily to the Daiichi-1 reactor, but what is happening at Daiichi-3 seems to parallel the first reactor. He goes on to walk through the after-effects of all this, including the not inconsiderable issue that Japan will experience a prolonged power shortage, with as many as half of the country’s nuclear reactors needing inspection and the nation’s power generating capacity reduced by 15 percent. As to the effect of radiation in the environment:
Some radiation was released when the pressure vessel was vented. All radioactive isotopes from the activated steam have gone (decayed). A very small amount of Cesium was released, as well as Iodine. If you were sitting on top of the plants’ chimney when they were venting, you should probably give up smoking to return to your former life expectancy. The Cesium and Iodine isotopes were carried out to the sea and will never be seen again.
I don’t want to minimize the effect of any of this (and I certainly don’t want to play down the pain, both physical and psychological, of the brave people of Japan), but at a time when terror over nuclear operations seems to be running rampant, it’s important that a more balanced view come to the fore in the media. In a message a few minutes ago (about 1330 UTC), Jason Morgan told me that the Oehmen essay would be posted soon on the MIT website, so I’ll link to that as soon as it goes up. Do read what Oehmen has to say as a counterbalance to the sensationalism that seems to follow nuclear issues whenever they appear, and help us keep a sane outlook on a very sad situation.
Addendum: MIT has now published a modified version of the Oehmen essay.
