For more than half a century, thermonuclear fusion has held out the promise of cheap, clean, and virtually limitless energy. Unleashed through a fusion reactor of some sort, the energy from 1 gram of deuterium, an isotope of hydrogen, would be equivalent to that produced by burning 7000 liters of gasoline. Deuterium is abundant in ocean water, and one cubic kilometer of seawater could, in principle, supply all the world's energy needs for several hundred years.

So why haven't we built any such reactors? Basically, because after spending billions of dollars on research, we have yet to identify an economically viable fusion-reactor technology that can consistently produce more energy than it consumes. Today, researchers are using enormous lasers or powerful magnetic fields to trigger limited fusion reactions among deuterium and other hydrogen isotopes. Results are promising and yet still modest—and so the challenge remains.

For several years our research groups—at Purdue University in West Lafayette, Ind.; Rensselaer Polytechnic Institute in Troy, N.Y.; and the Russian Academy of Sciences branch in Ufa—have been working on a new way to create fusion reactions. By applying sound waves to a deuterium-rich liquid, we create pressure oscillations that implode tiny bubbles filled with deuterium vapor. The bubbles' violent collapse can cause some of the deuterium nuclei to undergo fusion.

It is hard to imagine that mere sound waves can possibly produce in the bubbles, even briefly, the extreme temperatures and pressures created by the lasers or magnetic fields, which themselves replicate the interior conditions of stars like our sun, where fusion occurs steadily. Nevertheless, three years ago, we obtained strong evidence that such a process—now known as sonofusion—is indeed possible.

Since then, we have been working to improve and scale up our apparatus, investigating the possibility that it can produce a sizable surplus of energy. If this proves possible—and it's still a big "if"—sonofusion could become a revolutionary new energy source.

To explore this enticing possibility, early this year our research team joined forces with others to create the Acoustic Fusion Technology Energy Consortium, or AFTEC. Its five founders are Boston University; Impulse Devices Inc. in Grass Valley, Calif.; Purdue University; the University of Mississippi in Oxford; and the University of Washington in Seattle. Its goal is to promote the development of sonofusion and its related science and technology.