"Dozens of companies, including all the major automobile manufacturers, have designed engines that burn hydrogen--they're a lot like the internal combustion engines we have in cars today," says Al Sacco, director of the NASA-supported Center for Advanced Microgravity Materials Processing (CAMMP) at Northeastern University in Boston.
explains: "Zeolites are porous, rocky substances that act like molecular sponges.
In their crystalline form, zeolites are threaded by a network of interconnected tunnels and cages, similar to a honeycomb.
A fuel tank lined with such crystals might be able to trap and store hydrogen gas "in a liquid-like state--without heavy cryogenics.
With support from NASA's
Space Product Development program at the Marshall Space Flight Center
and colleagues at CAMMP
are working to make zeolite gas tanks a reality.
described how a temperature-controlled zeolite gas tank might work: "We would add some negatively-charged ions to the zeolite.
"The zeolites we have now can store quite a bit of hydrogen," notes Sacco
"But not enough."
"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.
In 1995, Sacco
travelled to space as a mission specialist onboard the space shuttle Columbia (STS-73).
purpose: to grow better zeolite crystals.
"The next step is the International Space Station," says Sacco
and others at CAMMP
have built a Zeolite Crystal Growth Furnace, which was installed on the ISS
in early 2002.
"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."
Zeolite crystals grown on Earth (above) and zeolite crystals grown onboard the shuttle Columbia in 1995 (below).
has envisioned a worldwide transition from fossil to hydrogen fuels.