Hydrogen Cars

"If we can grow zeolite crystals that hold 6% to 7% of their own weight in hydrogen," says Sacco, "then a zeolite tankful of hydrogen would be competitive with an ordinary tankful of gasoline." The best existing zeolites can hold only 2% to 3%, however.

In 1995, Sacco traveled to space as a mission specialist onboard the space shuttle Columbia (STS-73). His purpose: to grow better zeolite crystals. "In low-gravity, materials come together more slowly, allowing zeolite crystals to form that are both larger and more orderly." Zeolite crystals produced on Earth are small, roughly 2 to 8 microns across. "That's about one-tenth the thickness of a human hair." The ones he grew on the space shuttle were not only 10 times bigger, but also better organized internally - a promising start.

more Zeolite crystals grown on Earth (above) and zeolite crystals grown onboard the shuttle Columbia in 1995 (below)

"The next step is the International Space Station," says Sacco. He and others at CAMMP have built a Zeolite Crystal Growth Furnace, which was installed on the ISS in early 2002. "Ken Bowersox, the ISS Expedition 6 commander, has used the furnace to grow some crystals for us. Ken had to correct some unexpected problems with the mixing of the crystal growth solution - this shows the values of humans in space - but after that the experiment went smoothly."

"Now we need to get those crystals back to Earth where we can examine them. A few might come down in May," when the Expedition 6 crew leaves the ISS in an Soyuz capsule. "I'd really like to see them," says Sacco.

The goal, he says, is not to mass produce zeolite crystals in space. That's not economical - at least not yet. "We simply want to find out if it's possible to grow zeolite crystals that can reach the 7% threshold. If we can do that in space, we'll figure out how to reproduce the process on the ground."

Throughout his career, Sacco has envisioned a worldwide transition from fossil to hydrogen fuels. It's a big dream, but it could happen. "Zeolites may be the key to hydrogen fuel as a leapfrog technology."

Coming soon… a hydrogen fueling station near you?