On Wed, 19 May 2004 21:27:29 +0100, David CL Francis
wrote in Message-Id:
:

I remember someone talking about nuclear powered aircraft many years
ago. He said that it would solve one aviation problem; about the
placement of the cg. Wherever the reactor was placed, with its
shielding, that's where the cg would be. ;-)


Here's some information on the subject:

http://www.defensetech.org/archives/000918.html
ATOMIC PLANES IN THE WORKS?
The first line sure is juicy: "After more than six decades of
research, the first atom-powered airplane is cleared for takeoff."

And even if the substance doesn't quite back up the tantalizing intro
in the current Popular Mechanics -- which it doesn't -- this is still
an interesting concept.

The attraction of a nuclear plane is that it doesn't run out of fuel.
Convert a drone to atomic power, and it could stay aloft just about
forever, the thinking goes.

The nuclear drone wouldn't have a traditional fission reactor, running
on uranium or plutonium. Instead, it would be powered by hafnium-178.

"In the late 1990s, researchers at the University of Texas in Dallas
made a remarkable and unexpected discovery about [halfnium]," the
magazine says. "When they bombarded the metal with 'soft' X-rays like
those your dentist uses to examine your teeth, the metal released a
burst of gamma rays 60 times more powerful than the X-rays."

This reaction could be safer than conventional ones, the magazine
argues.

"The gamma ray output drops precipitously the moment power to the
X-ray machine is turned off... Since it produces only gamma radiation,
less shielding is required. And should an accident occur, there is
less of an environmental concern than with fission. Hafnium-178 has a
half-life of only 31 years compared to thousands of years for other
reactor fuels. In addition, unlike uranium or plutonium, hafnium-178
cannot support a chain reaction, which means it cannot be used to make
rogue nuclear weapons."

But, despite the potentially attractive features, an atomic drone is
nowhere near takeoff.

"Project managers for Northrop Grumman and the U.S. Air Force Research
Laboratory tell Popular Mechanics they have begun discussions that
could lead to the conversion of a Global Hawk [drone] to a
nuclear-powered aircraft… They have not yet signed a contract to
convert a Global Hawk to nuclear power, they are aware of discussions
taking place within the Air Force." (emphasis mine)

THERE'S MO Some scientists are pouring cold water all over the
halfnium idea, reader MS points out. "May not make physical sense,"
was the opinion of 5 of 12 Pentagon researchers appointed to look into
halfnium bombs.

AND MO Defense Tech "deserves better than Popular Mechanics doing a
fair imitation of the National Inquirer," says Los Alamos consultant
and nuclear proliferation expert Russell Seitz.

With so-called "isomers" like halfnium-178, he writes, "energy has
both to be put in and gotten out. The mere fact that more and better
physicists using fiercer x-ray sources and more sensitive gamma
detectors can't get any signal out of the same isotopes -- even upon
many experimental iterations and variations -- satisfies me that
[this] is just another example of the economics of desire."

AND MO The Defense Department was looking at atomic planes back in
the 1940's, reader JM notes, with a project called "Nuclear Energy for
the Propulsion of Aircraft," or NEPA. And for a year or so, the
Pentagon considered irradiating human test subjects, to see how much
nuclear exposure pilots could take. After Manhattan Project scientist
Dr. Joseph Hamilton pointed out that such experiments would have "a
little of the Buchenwald touch," the idea was finally, and thankfully,
dropped.


--

Irrational beliefs ultimately lead to irrational acts.
-- Larry Dighera,