Although I've often seen Arthur Conan Doyle's Sherlock Holmes cited in various ways, I hadn't chased down the source of this famous quote: "When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth." Gerald Jackson's new paper identifies the story as Doyle's "The Adventure of the Blanched Soldier," which somehow escaped my attention when I read through the Sherlock Holmes corpus a couple of years back. I'm a great admirer of Doyle and love both Holmes and much of his other work, so it's good to get this citation straight. As I recall, Spock quotes Holmes to this effect in one of the Star Trek movies; this site's resident movie buffs will know which one, but I've forgotten. In any case, a Star Trek reference comes into useful play here because what Jackson (Hbar Technologies, LLC) is writing about is antimatter, a futuristic thing indeed, but also in Jackson's thinking a real candidate for a propulsion system that involves using...

My family has had a closer call with ALS than I would ever have wished for, so the news of Stephen Hawking's death stays with me as I write this morning. I want to finish up my thoughts on antimatter from the last few days, but I have to preface that by noting how stunning Hawking's non-scientific accomplishment was. In my family's case, the ALS diagnosis turned out to be mistaken, but there was no doubt about Hawking's affliction. How on Earth did he live so long with an illness that should have taken him mere years after it was identified? Hawking's name will, of course, continue to resonate in these pages -- he was simply too major a figure not to be a continuing part of our discussions. With that in mind, and in a ruminative mood anyway, let me turn back to the 1950s, as I did yesterday in our look at Eugen Sänger's attempt to create the design for an antimatter rocket. Because even as Sänger labored over the idea, one he had been pursuing since the 1930s, Les Shepherd was...

Antimatter's staggering energy potential always catches the eye, as I mentioned in yesterday's post. The problem is how to harness it. Eugen Sänger's 'photon rocket' was an attempt to do just that, but the concept was flawed because when he was developing it early in the 1950s, the only form of antimatter known was the positron, the antimatter equivalent of the electron. The antiproton would not be confirmed until 1955. A Sänger photon rocket would rely on the annihilation of positrons and electrons, and therein lies a problem. Sänger wanted to jack up his rocket's exhaust velocity to the speed of light, creating a specific impulse of a mind-boggling 3 X 107 seconds. Specific impulse is a broad measure of engine efficiency, so that the higher the specific impulse, the more thrust for a given amount of propellant. Antimatter annihilation could create the exhaust velocity he needed by producing gamma rays, but positron/electron annihilation was essentially a gamma ray bomb, pumping out...

Antimatter will never lose its allure when we're talking about interstellar propulsion, even if the breakthroughs needed to harness it are legion. After all, a kilogram of antimatter, annihilating itself in contact with normal matter, yields roughly ten billion times the amount of energy released when a kilogram of TNT explodes. Per kilogram of fuel, we're talking about 1,000 times more energy than nuclear fission, and 100 times the energy available through nuclear fusion. Or we could put this into terms more suited for space. A single gram of antimatter, according to Frank Close's book Antimatter (Oxford, 2010), could through its annihilation produce as much energy as the fuel from the tanks of two dozen Space Shuttles. The catalog of energy comparisons could go on, each as marvelous as the last, but the reality is that antimatter is not only extremely difficult to produce in any quantity but even more challenging to store. Cram enough positrons or antiprotons into a magnetic bottle...

An antimatter probe to a nearby star? The idea holds enormous appeal, given the colossal energies obtained when normal matter annihilates in contact with its antimatter equivalent. But as we’ve seen through the years on Centauri Dreams, such energies are all but impossible to engineer. Antimatter production is infinitesimal, the by-product of accelerators designed with a much different agenda. Moreover, antimatter storage is hellishly difficult, so that maintaining large quantities in a stable condition requires multiple breakthroughs. All of which is why I became interested in the work Gerald Jackson and Steve Howe were doing at Hbar Technologies. Howe, in fact, became a key source when I put together the original book from which this site grew. This was back in 2002-2003, and I was captivated with the idea of what could be called an ‘antimatter sail.’ The idea, now part of a new Kickstarter campaign being launched by Jackson and Howe, is to work with mere milligrams of antimatter,...

Talking about antimatter, as we've done in the past two posts, leads to the question of why the stuff is so hard to find. When we make it on Earth, we do so by smashing protons into targets inside particle accelerators of the kind found at the Fermi National Accelerator Laboratory in Batavia, IL and CERN (the European Organization for Nuclear Research). It's not exactly an efficient process from the antimatter production standpoint, as it produces a zoo of particles, anti-particles, x-rays and gamma rays, but it does give us enough antimatter to study. But there is another way to find antimatter, for it occurs naturally in the outer Solar System and even closer to home. James Bickford (Draper Laboratory, Cambridge MA) has looked at how we might trap antimatter that occurs in the Earth's radiation belts. In a report for NIAC back in 2006 (available here), Bickford laid out a strategy for using high temperature superconductors to form two pairs of RF coils with a radius of 100 meters,...

I spent this past weekend poking into antimatter propulsion concepts and in particular looking back at how the idea developed. Two scientists -- Les Shepherd and Eugen Sänger -- immediately came to mind. I don't know when Sänger, an Austrian rocket designer who did most of his work in Germany, conceived the idea he would refer to as a 'photon rocket,' but he was writing about it by the early 1950s, just as Shepherd was discussing interstellar flight in the pages of the Journal of the British Interplanetary Society. A few thoughts: Sänger talked about antimatter propulsion at the 4th International Astronautical Congress, which took place in Zurich in 1953. I don't have a copy of this presentation, though I know it's available in a book called Space-Flight Problems (1953), which was published by the Swiss Astronautical Society and bills itself as a complete collection of all the lectures delivered that year in Zurich. If you like to track ideas as much as I do, you'll possibly be...

If you didn't see this morning's spectacular launch of the SpaceX Falcon 9, be sure to check out the video (and it would be a good day to follow @elonmusk on Twitter, too). As we open the era of private launches to resupply the International Space Station, it's humbling to contrast how exhilarating this morning feels with the great distances we have to traverse before missions to another star become a serious possibility. We've been talking the last few days about the promise of antimatter, but while the potential for liberating massive amounts of energy is undeniable, the problems of achieving antimatter propulsion are huge. So we have to make a lot of leaps when speculating about what might happen. But let's assume just for the sake of argument that the problem analyzed yesterday -- how to produce antimatter in quantity -- is solved. What kind of antimatter engine would we build? If everything else were optimum, we'd surely try to master a beamed core drive, the pure product of the...

Antimatter is so tantalizing a prospect for propulsion that every time a new slant on using it appears, I try to figure out its implications for long-haul missions. But the news, however interesting, is inevitably balanced by the reality of production problems. There's no question that antimatter is potent stuff, with the potential for dealing out a thousand times the energy of a nuclear fission reaction. Use hydrogen as a working fluid heated up by antimatter and 10 milligrams of antimatter can give you the kick of 120 tonnes of conventional rocket fuel. If we could get the cost down to $10 million per milligram, antimatter propulsion would be less expensive than nuclear fission methods, depending on the efficiency of the design. But how to reduce the cost? Current estimates show that producing antimatter in today's accelerator laboratories runs the total up to $100 trillion per gram. But when I was researching my Centauri Dreams book, I spent some time going through the collection...

In Stephen Baxter’s wonderful novel Ark (Roc, 2010), a team of scientists works desperately to come up with an interstellar spacecraft while epic floods threaten the Earth. The backdrop gives Baxter the chance to work through many of our current ideas about propulsion, from starships riding a wave of nuclear explosions (Orion) to antimatter possibilities and on into Alcubierre warp drive territory. I won’t give away the solution, but will say that it partly involves antimatter used in an unorthodox way, and because Baxter’s is a near-term Earth, there simply isn’t enough antimatter to go around. That means getting to Jupiter first to harvest it. Antimatter in space is an idea that James Bickford (Draper Laboratory) analyzed in a Phase II study for NASA’s Institute for Advanced Concepts, for he had realized that high-energy galactic cosmic rays interacting with the interstellar medium (and also with the upper atmospheres of planets in the Solar System) produce antimatter. In fact,...

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...

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...

Now that NASA's Institute for Advanced Concepts (NIAC) is back in business, I'm reminded that it was through NIAC studies that both Gerald Jackson and James Bickford introduced the possibility of harvesting antimatter rather than producing it in huge particle accelerators. The idea resonates at a time when the worldwide output of antimatter is measured in nanograms per year, and the overall cost pegged at something like $100 trillion per gram. Find natural antimatter sources in space and you can think about collecting the ten micrograms that might power a 100-ton payload for a one-year round trip mission to Jupiter. Contrast that with Juno's pace! That assumes, of course, that we can gather enough antimatter to test the concept and develop propulsion systems -- doubtless hybrids at first -- that begin to draw on antimatter's power. Bickford (Draper Laboratory, Cambridge MA) became interested in near-Earth antimatter when he realized that the bombardment of the upper atmosphere of the...

Are we ever going to use antimatter to drive a starship? The question is tantalizing because while chemical reactions liberate about one part in a billion of the energy trapped inside matter -- and even nuclear reactions spring only about one percent of that energy free -- antimatter promises to release what Frank Close calls 'the full mc2 latent within matter.' But assuming you can make antimatter in large enough amounts (no mean task), the question of storage looms large. We know how to store antimatter in so-called Penning traps, using electric and magnetic fields to hold it, but thus far we're talking about vanishingly small amounts of the stuff. Moreover, such storage doesn't scale well. An antimatter trap demands that you put charged particles into a small volume. The more antimatter you put in, the closer the particles are to each other, and we know that electrically charged particles with the same sign of charge repel each other. Keep pushing more and more antimatter...

Interstellar theorist Richard Obousy (Baylor University) has some thoughts about William and Arthur Edelstein's ideas on flight near the speed of light. As discussed in these pages on Friday, the Edelsteins, in a presentation delivered at the American Physical Society, had argued that a relativistic rocket would encounter interstellar hydrogen in such compressed form that its crew would be exposed to huge radiation doses, up to 10,000 sieverts in the first second. Because even a 10-centimeter layer of aluminum shielding would stop only a tiny fraction of this energy, the Edelsteins concluded that travel near lightspeed would be all but impossible. Obousy, who handles the Project Icarus Web site, has his own credentials related to high speed travel, authoring a number of papers like the recent "Casimir energy and the possibility of higher dimensional manipulation" (abstract) that press for continued work into breakthrough propulsion. And when he talked to astrophysicist Ian O'Neill...

Antimatter's allure for deep space propulsion is obvious. If matter is congealed energy, we need to find the best way to extract that energy, and our existing rockets are grossly inefficient. Even the best chemical rocket pulls only a billionth of the energy available in the atoms of its fuel, while a fission reaction, powerful as it seems, is tapping one part in a thousand of what is available. Fusion reactions like those in a hydrogen bomb use up something on the order of one percent of the total energy within matter. But antimatter can theoretically unlock all of it. Freeing Trapped Energy The numbers are startling. A kilogram of antimatter, annihilating with ordinary matter, can produce ten billion times the amount of energy released when a kilogram of TNT explodes. Heck, a single gram of antimatter, which is about 1/25th of an ounce, would get you as much energy as you could produce from the fuel tanks of two dozen Space Shuttles. This is the ultimate kick if we can figure out a...

Irradiate a millimeter-thick gold target with the right kind of laser and you might get a surprise in the form of 100 billion positrons, the antimatter equivalent of electrons. Researchers had been studying the process at Lawrence Livermore National Laboratory, where they used thin targets that produced far fewer positrons. The new laser method came about through simulations that showed a thicker target was more effective. And suddenly lasers and antimatter are again making news. Hui Chen is the Livermore scientist behind this work: "We've detected far more anti-matter than anyone else has ever measured in a laser experiment. We've demonstrated the creation of a significant number of positrons using a short-pulse laser." Image: Physicist Hui Chen sets up targets for the antimatter experiment at the Jupiter laser facility. Credit: Lawrence Livermore National Laboratory. What's happening here is that ionized electrons are interacting with gold nuclei, giving off energy that decays into...

Antimatter's great attraction from a propulsion standpoint is the ability to convert 100 percent of its mass into energy, a reaction impossible with fission or fusion methods. The trick, of course, is to find enough antimatter to use. We can produce it in particle accelerators but only in amounts that are vanishingly small. There is evidence that it is produced naturally, at least in trace amounts, in the relativistic jets produced by black holes and pulsars. Indeed, a cloud of antimatter 10,000 light years across has been described around our own galaxy's center. And at least one scientist, James Bickford (Draper Laboratory), has worked out ways to extract antimatter produced here in the Solar System, a method that he believes would be five orders of magnitude more cost effective than creating the stuff on Earth. But what about early antimatter, particles left over from the earliest days of the universe? According to prevalent theory, the universe may have been awash with the stuff...

Just how hard would it be to build a true interstellar craft? I'm not talking about a spacecraft that might, in tens of thousands of years, drift past a star by happenstance, but about a true, dedicated interstellar mission. Those of you who've been following my bet with Tibor Pacher on Long Bets (now active, with terms available for scrutiny on the site) know that I think such a mission will happen, but not any time soon. And the proceedings of the Joint Propulsion Conference, held last month in Hartford, go a long way toward explaining why the problem is so difficult. Wired looked at the conference results in a just published article, the most interesting part of which contained Robert Frisbee's speculations about antimatter rocketry. Two things have been clear about antimatter for a long time. The first is that producing sufficient antimatter is a problem in and of itself, one that may keep us working with tiny amounts of the stuff for some time to come. Even so, interesting...

Those gamma rays coming out of galactic center, flagging the presence of an antimatter cloud of enormous extent, have spawned few explanations more exotic than the one we consider today: Black holes. Primordial black holes, in fact, produced in their trillions at the time of the Big Bang and left evaporating through so-called 'Hawking radiation' ever since. That's the theory of Cosimo Bambi (Wayne State University) and colleagues, who are studying the same antimatter cloud we recently examined here in terms of its possible connection with low mass X-ray binary stars. Hawking radiation offers a mechanism for small black holes to lose mass over time. But since the phenomenon has never been observed, the upcoming launch of the GLAST (Gamma-ray Large Area Space Telescope) satellite again looms large in significance. GLAST should be able to find evaporating black holes, assuming they are there, and there is even some possibility that the Pierre Auger Observatory may eventually detect tiny...