Although I had planned to push straight on to look at instrumentation for a true interstellar mission (using Mike Gruntman's landmark paper on the topic), I want to revise that schedule because of the recently announced antimatter news. We'll return to the instrumentation issue on Monday, including the tricky question of how a probe designed to reach 400 AU can make effective measurements given its speed (75 km/s in the best case scenario Gruntman looks at). Because that question just gets trickier as speeds ramp up, it's a major one for planning. But on to antimatter, a cloud of which has been known to exist around the galactic center since the 1970s, when balloon-based gamma-ray detectors first located it. Gamma rays are significant in terms of antimatter because electrons encountering positrons (their antimatter equivalent) annihilate each other, with their mass converted into high energy gamma rays. So the cloud's presence is well established. The question since its detection is...

Robert Forward used to talk about antimatter factories in space, installations that would draw their power from the Sun. He would point out that at a distance of 1 AU, our star delivers a gigawatt of energy for each square kilometer of collector. And being Robert Forward, he thought big: Build a collector array one hundred kilometers on a side to produce a power input of ten terawatts, enough to drive several antimatter factories at full power and produce a gram of antimatter each day. Forward saw the antimatter problem as a matter of scaling and cost (and he often talked about 'small problems of engineering'). As we've seen in the last few days, James Bickford (Draper Laboratory) is more than aware of both these issues, but unlike Forward, he's keen on mining naturally occurring sources of antimatter right here in the Solar System. Forward's huge factories may some day be built, but for now, let's talk about how to get our early antimatter missions into the realm of possibility by...

James Bickford's antimatter work for NASA's Institute for Advanced Concepts, a Phase II study completed just as NIAC was announcing its closure, prompted a number of comments from readers when I opened discussion of it on Monday. And I can see why. We're used to thinking of antimatter production as an extraordinarily expensive process happening only in particle accelerators. And even when we commit the resources to make it, we get only the tiniest amounts, and at costs so high that they make propulsion concepts for antimatter seem chimerical. But Bickford wants us to consider a naturally occurring source of antimatter, one that might offer the potential of being collected in space for a variety of missions. Key to the idea is the fact that high-energy galactic cosmic rays (GCR) continually bombard the upper atmosphere of the planets in our Solar System, as well as interacting with material in the interstellar medium. The result is 'pair production,' the creation of an elementary...

Great ideas fan out in unexpected directions, which is why James Bickford now looks at antimatter in a new light. Bickford (Draper Laboratory, Cambridge MA) realized that an adaptation of Robert Bussard's interstellar ramscoop might have its uses in collecting antimatter. The concept grew out of the realization that antimatter sources were available not only near the Earth but farther out in the Solar System, where antiparticles could be collected and used to boost spacecraft initially to speeds of 100 kilometers per second. That's sufficient for interstellar precursor missions outside the heliosphere, including the possibility of getting a payload to the Sun's gravitational focus, where a new kind of space-based astronomy waits to be exploited. Refine the process enough and you start talking about even greater speeds through more efficient antimatter collection, one great benefit being that instead of producing the stuff in Earth-bound particle accelerators, you're actually mining...

Antimatter would seem to be an ideal propulsion candidate for starships. After all, the annihilation of matter and antimatter is mind-bogglingly efficient, releasing energies that fission or fusion engines could not hope to achieve. A single gram of antimatter meeting a gram of ordinary matter would release the energy of a 20-kiloton bomb. And talk about mass ratios -- Robert Forward calculated that a one-ton Centauri probe moving at a tenth of lightspeed would require no more than four tons of liquid hydrogen and forty pounds of antimatter. In fact, antimatter sounds great until you realize that current production runs in the range of nanograms per year. And even if we could magically boost antimatter production, containment remains a problem. A Penning trap, which uses electrical and magnetic fields to hold the charged particles in suspension from normal matter, is heavy, hard to manage and houses only a small amount of antimatter, although Penn State's Mark I offered a significant...

If we need a huge particle accelerator to produce antimatter and use it only for exotic experiments, how are we ever going to ramp up production to the point where it becomes practical as a propulsion system? One answer may be that as we study the minute amounts of antimatter available for study today, we are learning how to use it in ways that are far more likely to catch the public eye, as in medicine. And treating cancer effectively -- ask any patient -- is anything but theoretical. At CERN (European Organization for Nuclear Research), the Antiproton Cell Experiment (ACE) has been running since 2003. It's an attempt to look at antimatter's effect on cancer cells, and its results are startling. Antiprotons, it turns out, are four times more effective than protons at destroying live cancer cells. Here's CERN's Michael Holzscheiter on the encouraging news: "To achieve the same level of damage to cells at the target area one needs four times fewer antiprotons than protons. This...

An operating run at Fermilab involving the Tevatron, the world's highest-energy particle accelerator, has produced an experimental result of extraordinary precision, one that has measured transitions between matter and antimatter that occur three trillion times a second. Tevatron Run 2, from February of 2002 to January of this year, produced trillions of collisions between protons and antiprotons to achieve the discovery, a measurement sought for two decades. Making the fast change is the B_s meson (pronounced B-sub-s), whose behavior is predicted by the Standard Model that describes our understanding of fundamental particles and forces in the universe. The finding thus reinforces that model in the world of the exquisitely small. The B_s meson is made up of a bottom quark bound by the strong nuclear interaction to a strange antiquark. These exotic particles, present in abundance in the early universe, can only be produced and studied at particle accelerator installations like...

Exciting news on the antimatter front with the launch of PAMELA, a probe designed to detect antimatter in space. Standing for Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics, the PAMELA spacecraft lifted off from Baikonur on June 15. The mission should be a significant upgrade to previous balloon-borne attempts to survey antimatter inflows in the cosmic rays falling on Earth. Image: A look at PAMELA, a dedicated mission to study antimatter. Credit: Firenze/INFN. "It's the first serious, dedicated space experiment to detect cosmic rays," says Felix Aharonian, an astrophysicist from the Max Planck Institute in Heidelberg, Germany, in a news story by Mark Peplow on Nature.com. Which makes PAMELA an intriguing thing indeed, and worth considering in light of other studies of antimatter in space, such as James Bickford's recent work on antimatter collection in the Solar System, and the long-term prospect of antimatter factories working around a gas giant like...

Ponder how difficult current antimatter work is. We produce the stuff in our particle accelerators and rely on extracting antiparticles from collision debris. One in about 105 proton collisions actually produces an antiproton that can be collected. This is why we see figures like $62.5 trillion per gram (some estimates are even higher) for antiproton production costs. Not only that, but once we have created antimatter, we have to store it in a vacuum in magnetic/electric fields to keep it from any contact with normal matter. All these are problems with using antimatter for propulsion. After all, it's one thing to store tiny amounts of antimatter in bulky Earth-based traps, and quite another to scale storage up to protect the antimatter from annihilation for a period of months or years, not to mention the need to transport it into orbit for uses in space. But as James Bickford (Draper Laboratory, Cambridge MA) and team point out, antimatter creation and storage in space seems more...

One of the beauties of antimatter is its efficiency. A fission reaction uses up about 1 percent of the available energy inside matter, whereas the annihilation of antimatter and matter converts 100 percent of the mass into energy. No wonder tiny amounts of antimatter can have such powerful effects. Put a gram of matter together with a gram of antimatter and you release the equivalent of a 20 kiloton bomb, about the size of the one that destroyed Hiroshima. And if you really want to see antimatter's potential, consider what it does to mass ratios, which compare the weight of a fully fueled spacecraft with that of an empty one. In his book Mirror Matter: Pioneering Antimatter Physics (New York: John Wiley & Sons, 1988), Robert Forward spoke of antimatter-driven spacecraft with mass ratios of 5 to 1 (by contrast, the Apollo missions operated with a ratio of 600 to 1). Indeed, Forward believed that a 1-ton probe to Alpha Centauri would require roughly four tons of liquid hydrogen and...

Antimatter seems the boldest -- and newest -- of propulsion concepts, but in fact Eugen Sänger's work on the uses of antimatter in rocketry goes back to the 1930s. The German scientist thought it would be possible to reflect gamma rays produced by the annihilation of electrons and positrons to produce thrust. His work wowed the Fourth International Astronautical Congress in 1952, but there was a catch: the gamma rays created by this reaction seemed too energetic to use the way Sänger hoped -- they penetrated all known materials and could not be channeled effectively into a rocket exhaust. Which is why most antimatter designs since have focused on antiprotons. When antiprotons and protons annihilate each other, they produce not only gamma rays but pi-mesons, short-lived particles also known as pions. Many of these are charged as they emerge from the proton/antiproton annihilation, and can therefore be controlled by sending them through a strong magnetic field. Early designs by Robert...

Following up on yesterday's intriguing antimatter results at Fermilab, a neutrino study called the Main Injector Neutrino Oscillation Search (MINOS) is providing independent confirmation of a critical idea: neutrinos have mass. This is significant news because it helps to illuminate earlier experiments that suggested neutrinos oscillate between three different types, something that could occur only if they do have mass, and an effect that, given the sheer abundance of neutrinos in the universe, may provide clues to why antimatter has disappeared and how galaxies originally formed. Neutrinos are odd things indeed; they can pass through the entire Earth without interacting with matter. MINOS studies them by producing neutrinos at Fermilab using protons accelerated in a 4000 foot tunnel pointing toward a second detector some 450 miles away in Soudan, Minnesota. The neutrinos are measured first with a detector below the Fermilab site, with a second measurement being taken at a 6000-ton...

With 700 physicists from 90 different institutions in 20 countries working on an experiment, you expect interesting results. And the DZero experiment at Fermi National Accelerator Laboratory is living up to the expectation. Scientists at Fermilab have been studying a subatomic particle known as the B_s meson (pronounced 'B sub s'). Their work suggests that this particle actually oscillates between matter and antimatter more than 17 trillion times per second. The data come from over 1 billion events at Fermilab's Tevatron particle accelerator, and more precise results are expected soon from a different Fermilab collaboration. And the more we learn, the better: exactly how particles turn into their own antiparticles, and with what frequency, is a major issue that could point to answers in an even bigger one, the balance between matter and antimatter in the universe. For if matter and antimatter appeared in equal numbers at the time of the Big Bang, their mutual annihilation should have...

With Hayabusa apparently stabilized and ready to begin its return journey to Earth, and with the Falcon-1 launch delayed until mid-December, it's time to return to research. But not before congratulating the Japanese space agency (JAXA) for the probe's apparent success in landing on the asteroid Itokawa, collecting surface samples, and lifting off again. These would be the first asteroid materials ever returned to Earth, and if their landing in 2007 proceeds as planned, they will be the capstone of a remarkable mission. On the research front, what catches the eye this foggy North Carolina morning is the report in Nature that scientists may have created positronium molecules made out of two positronium atoms. If so, it would be a singular accomplishment. Positronium replaces the hydrogen proton with a positron (the antimatter equivalent of an electron). So instead of normal hydrogen's single electron moving around a proton, you get an electron moving around a positron which, like the...

"It is quite possible to build atmospheric vehicles using an antimatter drive. After all, a tenth of a gram of the stuff could power a family flivver to orbit and back. But no machine is perfect, and even that tiny smidgin of antimatter would devastate the countryside if anything went wrong. When antimatter drives first become practical, we can expect treaties banning its use for propulsion within Earth's atmosphere. There are other potential uses for it on Earth; for example, as an ultimate compact source of energy to power an MHD [magnetohydrodynamic] electric plant. The exhaust product is a high-temperature plasma... MHD power does not have to be used to propel vehicles; it could also take care of those demand surges on a nation's electrical power grid. Will the treaties ban this use, too? We will risk a guess: yes. We will have other sources of energy from space by that time, and they do not involve the potential destruction of even a milligram of antimatter gone astray. So far...

Two studies stand out in the list of Phase 1 awards recently announced by NASA's Institute for Advanced Concepts (NIAC). Gerald Jackson of Hbar Technologies (Chicago) will work on "Antimatter Harvesting in Space," while James Bickford of Draper Laboratory (Cambridge, MA) will study "Extraction of Antiparticles Concentrated in Planetary Magnetic Fields." Both offer solutions to the huge antimatter production problem that currently has us extracting tiny amounts at fantastic price from particle accelerators here on Earth. Jackson's is a familiar name. He and Steve Howe at Hbar are well known in the antimatter community as proponents of a fascinating and evidently feasible antimatter sail concept that would be energized by minute amounts of antihydrogen (see this earlier Centauri Dreams story). Jackson's new work on antimatter harvesting suggests taking antimatter collection into space, snaring antiprotons produced by the collision of cosmic rays with dust and solar wind protons. "Just...