Harnessing a Fuel to the Stars
Source: The Birmingham News
November 7, 2000
HUNTSVILLE - A trip to the moon in 7.5 minutes. Mars in
a day.
These cosmic treks could be possible by the end of the
21st century with the help of antimatter. When this rare substance
collides with regular matter, it creates the most powerful known
energy source in the universe.
Researchers at NASA's Marshall Space Flight Center in
Huntsville are trying to find a way to harness this collision and use
it in engines that could propel spacecraft to speeds approaching
science fiction proportions.
Space & Technology
"Out of all the things we've got ... antimatter is the
only one capable of providing true high-speed, interstellar-type
flight," said Jim Martin, an aerospace engineer at Marshall's
Propulsion Research Center. "But it's with one caveat: you have to
have a lot of it." Every thing we touch or use is matter, Martin said.
"Everything around us is regular matter," he said.
Antimatter is the same as matter, but reversed - like
looking in a mirror, Martin explains. On the atomic level, antimatter
has an opposite charge and opposite spin. When the two collide, they
destroy each other and create energy.
Antimatter is scarce. Other than labs, it's usually only
created when cosmic rays collide with particles floating in space.
Martin and other Marshall researchers are working on an
antimatter storage system.
One theory of why antimatter is so scarce is that, at
the time of the Big Bang, a bit more matter than antimatter was
generated, Martin said.
The annihilation of matter and antimatter is the most
energy-dense reaction known in modern physics, Martin said.
Antimatter packs 10 billion times more energy than a
chemical rocket system such as the space shuttle, Martin said. "It
packs 1,000 times more energy of a fission system, and 100 times that
of fusion," he said.
For example, 42 milligrams of antimatter - about the
size of a BB - is equivalent to all the energy of the fuel carried in
the external tank of the space shuttle, Martin said. "It packs a heck
of a punch."
Rocket engines using only matter and antimatter as their
fuel could propel spacecraft to speeds approaching 40 percent of the
speed of light - or about 75,000 miles per second.
But getting the hundreds of pounds to tons of antimatter
required for such a system poses a major obstacle.
Because there's so little of it left in the universe,
antimatter has to be created in labs. There are only two U.S. labs
where antimatter can be created - Brookhaven National Laboratory in
New York and Fermi National Accelerator Laboratory in Illinois. They
produce it in large particle accelerators for use in physics
experiments.
The two labs produce tiny invisible traces of the stuff
each year - a whopping total of about two billionths of a gram.
At that rate it would take centuries and cost about $6
billion to produce just one microgram, Martin estimated. That amount
would still be invisible to the naked eye.
So what looks to be the most likely near-term solution
is a hybrid engine that uses a tiny amount of antimatter to spark a
fission/fusion-based engine.
That would involve adding a small amount of antimatter -
tinier than the tip of a pin - to the fission/fusion fuel mix, Martin
said. The antimatter would add enough energy to initiate a fission
reaction, which heats the fuel, sparking the more powerful fusion
reaction, he said.
Such a hybrid system could propel a spacecraft to speeds
ranging up to 558 miles per second, Martin said. That's like going
from Huntsville to Mobile in less than a second, to the moon in 7.5
minutes, or to Mars in 1 day - depending on Mars' orbital position.
In comparison, chemically fueled propulsion systems such
as those on the shuttle can propel spacecraft to speeds of 24,000
miles per hour. At that speed, it would take days to reach the moon
and months or more than a year to reach Mars.
Before antimatter can be used for propulsion, however,
key technological breakthroughs have to be made, Martin says.
One is the production of antimatter. It would take tens
of billions of dollars to build a facility dedicated solely to
producing enough antimatter - milligrams a year - to operate a hybrid
system, Martin said. Difficult to store
But perhaps the biggest technological challenge is
capturing, storing and preserving densely packed antimatter in a small
container and then extracting it at the right time and in the right
amount for the engine, Martin said.
Storage is what Martin is concentrating on in his
Marshall lab. He is the principal investigator for the High
Performance Antimatter Trap (HiPAT).
The HiPAT storage system basically has a small
electromagnetic bottle where chilled antimatter can be suspended to
keep it from touching the walls or banging into anything and
annihilating itself.
Marshall is spending about $100,000 a year on hardware
for the system, plus the salaries of the researchers.
Martin hopes HiPAT will be ready to go to one of the
U.S. labs - possibly Fermi - next summer to corral its first
antimatter and bring it home.
At Fermi, the antimatter is speeding around inside a rin
g that's about 1,000 feet in diameter, Martin said. "You have a swarm
of these things going at the speed of light (186,0000 miles a second)
and you've got to slow them down and not kill them," he said.
The antimatter will have a short shelf life - about two
weeks - so HiPAT would have to make a number of trips to the lab to
get more. Marshall researchers have plans to build a transport system
on an 18-wheeler for HiPAT so it can be easily transported.
The goal after experimenting with HiPAT is to make a
better trap - one that preserves antimatter longer, increases its
density, and can be used as the fuel tank for a hybrid engine, Martin
said.
"The next 10 to 20 years we'll probably prove the theory
... and we'll get to the point where we can build higher density
systems," Martin said.
"Then we can take it on for development of real
missions."
by Kent Faulk
News Staff Writer
© 2000
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