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...