nuclear propulsion

[brian carroll <human@electronetwork.org>]

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NASA considers nuclear boosters for space rockets

http://www.newscientist.com/news/news.jsp?id=ns9999972

11:30  	05  July  01
Ian Sample

NASA is thinking about using nuclear boosters to lift rockets into
orbit at a fraction of the cost of today's all-chemical launchers.

The agency hopes the public will be less resistant to
nuclear-assisted rockets now that the Bush administration is
considering a return to nuclear power. But anti-nuclear protesters
claim nuclear launchers would make accidents much more damaging and
accuse NASA of "playing Russian roulette".

.

NASA is keen to move away from conventional chemical rockets to
lighter, more powerful propulsion systems. "We've taken chemical
rockets pretty close to as far as we can," says Robert Adams of
NASA's Marshall Space Flight Center in Alabama.

"Nuclear systems give you a chance to reduce your mass and so your
overall costs to orbit," Adams says. Nuclear propulsion could allow
single-stage rockets to reach orbit - cutting the need for expendable
boosters and allowing what he calls "airline-like" access to space.


High flyer


Adams will describe conceptual plans for a "nuclear-enhanced
air-breathing rocket" at a meeting of the American Institute of
Aeronautics and Astronautics in Salt Lake City, Utah, next week. A
uranium dioxide fission reactor will heat hydrogen from an on-board
tank to 2500 °C. The hot hydrogen will then be mixed with air from
outside the rocket and combusted at almost 4000 °C.

After lift-off, a chemical rocket would first be used to accelerate
the rocket to Mach 2, before the nuclear engine was triggered. "You
wouldn't fire this reactor up until we got about 30,000 feet off the
ground," he says.

Adams's calculations show that a nuclear-assisted rocket could
produce far more thrust than conventional rockets. It would also be
lighter and be able to lift a bigger fraction of its starting mass
into orbit - perhaps as much as 45 per cent. "With existing systems,
it's more like 10 per cent," he says.

Whether the rockets will ever be safe enough to carry astronauts is
not yet clear. "We'd have to do a lot more calculations on the
radiation side of things," says Adams.


Plutonium power


Nuclear generators have been used before to provide electricity on
board spacecraft such as the Cassini probe which is on its way to
Saturn. But these generators don't use fission reactions, they simply
use the heat generated by a lump of radioactive plutonium to produce
electricity.

Even so, Cassini and other plutonium-carrying probes have drawn
criticism from anti-nuclear protesters fearful of nuclear fallout if
the rocket exploded on the launch pad or during its ascent.

But a change in public attitude towards nuclear power would take the
heat off NASA, says George Schmidt, deputy manager of the Propulsion
Research Center at Marshall.

"It really requires an education of the public," he says. "If there's
an enhancement of understanding about what nuclear is about, we can
benefit from that."


"A matter of time"


But the worries won't disappear, says George Maise, an aeronautical
engineer who works on nuclear-assisted rockets for Plus Ultra
Technologies in Stony Brook, New York.

"There are some legitimate safety and environmental issues if the
spacecraft were to crash during launch," he says. Triggering the
reactor in the atmosphere could also be a problem. "The idea of
deliberately releasing fission products into the atmosphere, even in
negligible amounts, is going to be a very hard sell."

Bruce Gagnon of the Global Network Against Weapons and Nuclear Power
in Space, which organised protests against Cassini, isn't reassured.
"It's just a matter of time before there's an accident," he says.


11:30  	05  July  01 copyright New Scientist dot com 2001.
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