http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2004/10/04/MNGM393GPK1.DTL&type=printable
<http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2004/10/04/MNGM393GPK1.DTL>Air
Force pursuing antimatter weapons
Program was touted publicly, then came official gag order
- Keay Davidson, Chronicle Science Writer
Monday, October 4, 2004
The U.S. Air Force is quietly spending millions
of dollars investigating ways to use a radical
power source -- antimatter, the eerie "mirror" of
ordinary matter -- in future weapons.
The most powerful potential energy source
presently thought to be available to humanity,
antimatter is a term normally heard in
science-fiction films and TV shows, whose heroes
fly "antimatter-powered spaceships" and do battle
with "antimatter guns."
But antimatter itself isn't fiction; it actually
exists and has been intensively studied by
physicists since the 1930s. In a sense, matter
and antimatter are the yin and yang of reality:
Every type of subatomic particle has its
antimatter counterpart. But when matter and
antimatter collide, they annihilate each other in
an immense burst of energy.
During the Cold War, the Air Force funded
numerous scientific studies of the basic physics
of antimatter. With the knowledge gained, some
Air Force insiders are beginning to think
seriously about potential military uses -- for
example, antimatter bombs small enough to hold in
one's hand, and antimatter engines for 24/7
surveillance aircraft.
More cataclysmic possible uses include a new
generation of super weapons -- either pure
antimatter bombs or antimatter-triggered nuclear
weapons; the former wouldn't emit radioactive
fallout. Another possibility is antimatter-
powered "electromagnetic pulse" weapons that
could fry an enemy's electric power grid and
communications networks, leaving him literally in
the dark and unable to operate his society and
armed forces.
Following an initial inquiry from The Chronicle
this summer, the Air Force forbade its employees
from publicly discussing the antimatter research
program. Still, details on the program appear in
numerous Air Force documents distributed over the
Internet prior to the ban.
These include an outline of a March 2004 speech
by an Air Force official who, in effect, spilled
the beans about the Air Force's high hopes for
antimatter weapons. On March 24, Kenneth Edwards,
director of the "revolutionary munitions" team at
the Munitions Directorate at Eglin Air Force Base
in Florida was keynote speaker at the NASA
Institute for Advanced Concepts (NIAC) conference
in Arlington, Va.
In that talk, Edwards discussed the potential
uses of a type of antimatter called positrons.
Physicists have known about positrons or
"antielectrons" since the early 1930s, when
Caltech scientist Carl Anderson discovered a
positron flying through a detector in his
laboratory. That discovery, and the later
discovery of "antiprotons" by Berkeley scientists
in the 1950s, upheld a 1920s theory of antimatter
proposed by physicist Paul Dirac.
In 1929, Dirac suggested that the building blocks
of atoms -- electrons (negatively charged
particles) and protons (positively charged
particles) -- have antimatter counterparts:
antielectrons and antiprotons. One fundamental
difference between matter and antimatter is that
their subatomic building blocks carry opposite
electric charges. Thus, while an ordinary
electron is negatively charged, an antielectron
is positively charged (hence the term positrons,
which means "positive electrons"); and while an
ordinary proton is positively charged, an
antiproton is negative.
The real excitement, though, is this: If
electrons or protons collide with their
antimatter counterparts, they annihilate each
other. In so doing, they unleash more energy than
any other known energy source, even thermonuclear
bombs.
The energy from colliding positrons and
antielectrons "is 10 billion times ... that of
high explosive," Edwards explained in his March
speech. Moreover, 1 gram of antimatter, about
1/25th of an ounce, would equal "23 space shuttle
fuel tanks of energy." Thus "positron energy
conversion," as he called it, would be a
"revolutionary energy source" of interest to
those who wage war.
It almost defies belief, the amount of explosive
force available in a speck of antimatter -- even
a speck that is too small to see. For example:
One millionth of a gram of positrons contain as
much energy as 37.8 kilograms (83 pounds) of TNT,
according to Edwards' March speech. A simple
calculation, then, shows that about 50-millionths
of a gram could generate a blast equal to the
explosion (roughly 4,000 pounds of TNT, according
to the FBI) at the Alfred P. Murrah Federal
Building in Oklahoma City in 1995.
Unlike regular nuclear bombs, positron bombs
wouldn't eject plumes of radioactive debris. When
large numbers of positrons and antielectrons
collide, the primary product is an invisible but
extremely dangerous burst of gamma radiation.
Thus, in principle, a positron bomb could be a
step toward one of the military's dreams from the
early Cold War: a so-called "clean" superbomb
that could kill large numbers of soldiers without
ejecting radioactive contaminants over the
countryside.
A copy of Edwards' speech onNIAC's Web site
emphasizes this advantage of positron weapons in
bright red letters: "No Nuclear Residue."
But talk of "clean" superbombs worries critics. "
'Clean' nuclear weapons are more dangerous than
dirty ones because they are more likely to be
used," said an e-mail from science historian
George Dyson of the Institute for Advanced Study
in Princeton, N.J., author of "Project Orion," a
2002 study on a Cold War-era attempt to design a
nuclear spaceship. Still, Dyson adds, antimatter
weapons are "a long, long way off."
Why so far off? One reason is that at present,
there's no fast way to mass produce large amounts
of antimatter from particle accelerators. With
present techniques, the price tag for
100-billionths of a gram of antimatter would be
$6 billion, according to an estimate by
scientists at NASA's Marshall Space Flight Center
and elsewhere, who hope to launch
antimatter-fueled spaceships.
Another problem is the terribly unruly behavior
of positrons whenever physicists try to corral
them into a special container. Inside these
containers, known as Penning traps, magnetic
fields prevent the antiparticles from contacting
the material wall of the container -- lest they
annihilate on contact. Unfortunately, because
like-charged particles repel each other, the
positrons push each other apart and quickly
squirt out of the trap.
If positrons can't be stored for long periods,
they're as useless to the military as an armored
personnel carrier without a gas tank. So Edwards
is funding investigations of ways to make
positrons last longer in storage.
Edwards' point man in that effort is Gerald
Smith, former chairman of physics and Antimatter
Project leader at Pennsylvania State University.
Smith now operates a small firm, Positronics
Research LLC, in Santa Fe, N.M. So far, the Air
Force has given Smith and his colleagues $3.7
million for positron research, Smith told The
Chronicle in August.
Smith is looking to store positrons in a
quasi-stable form called positronium. A
positronium "atom" (as physicists dub it)
consists of an electron and antielectron,
orbiting each other. Normally these two particles
would quickly collide and self-annihilate within
a fraction of a second -- but by manipulating
electrical and magnetic fields in their vicinity,
Smith hopes to make positronium atoms last much
longer.
Smith's storage effort is the "world's first
attempt to store large quantities of positronium
atoms in a laboratory experiment," Edwards noted
in his March speech. "If successful, this
approach will open the door to storing militarily
significant quantities of positronium atoms."
Officials at Eglin Air Force Base initially
agreed enthusiastically to try to arrange an
interview with Edwards. "We're all very excited
about this technology," spokesman Rex Swenson at
Eglin's Munitions Directorate told The Chronicle
in late July. But Swenson backed out in August
after he was overruled by higher officials in the
Air Force and Pentagon.
Reached by phone in late September, Edwards
repeatedly declined to be interviewed. His
superiors gave him "strict instructions not to
give any interviews personally. I'm sorry about
that -- this (antimatter) project is sort of my
grandchild. ...
"(But) I agree with them (that) we're just not at
the point where we need to be doing any public
interviews."
Air Force spokesman Douglas Karas at the Pentagon
also declined to comment last week.
In the meantime, the Air Force has been
investigating the possibility of making use of a
powerful positron-generating accelerator under
development at Washington State University in
Pullman, Wash. One goal: to see if positrons
generated by the accelerator can be stored for
long periods inside a new type of "antimatter
trap" proposed by scientists, including
Washington State physicist Kelvin Lynn, head of
the school's Center for Materials Research.
A new generation of military explosives is worth
developing, and antimatter might fill the bill,
Lynn told The Chronicle: "If we spend another $10
billion (using ordinary chemical techniques),
we're going to get better high explosives, but
the gains are incremental because we're getting
near the theoretical limits of chemical energy."
Besides, Lynn is enthusiastic about antimatter
because he believes it could propel futuristic
space rockets.
"I think," he said, "we need to get off this
planet, because I'm afraid we're going to destroy
it."
E-mail Keay Davidson at
kdavidson@sfchronicle.com.
Page A - 1
URL: http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2004/10/04/MNGM393GPK1.DTL
<http://sfgate.com/chronicle/info/copyright/>
©2004 San Francisco Chronicle |
<http://sfgate.com/feedback/>Feedback |
<http://sfgate.com/chronicle/faq.shtml>FAQ
|