Project Prometheus--turbine or MHD?

Does anybody know whether Project Prometheus is going to use a
turbine-driven generator or an MHD?

In article ,
Asherian wrote:
Does anybody know whether Project Prometheus is going to use a
turbine-driven generator or an MHD?

Nobody's made any decisions at that level of detail. It might well do
something like thermionic conversion.

MHD is actually pretty unlikely. As I understand it, making reliable,
long-lived MHD systems is an unsolved problem.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

(Henry Spencer) wrote in
:

In article
, Asherian
wrote:
Does anybody know whether Project Prometheus is going to
use a turbine-driven generator or an MHD?

Nobody's made any decisions at that level of detail. It
might well do something like thermionic conversion.

How would thermionic conversion work? I keep imagining
a big vacuum tube triode set up as an oscillator...
The cathode being directly heated by the reactor.

--Damon

In article ,
says...
(Henry Spencer) wrote in
:

In article
, Asherian
wrote:
Does anybody know whether Project Prometheus is going to
use a turbine-driven generator or an MHD?

Nobody's made any decisions at that level of detail. It
might well do something like thermionic conversion.

How would thermionic conversion work? I keep imagining
a big vacuum tube triode set up as an oscillator...
The cathode being directly heated by the reactor.

The thermionic device also needs to be able to dissipate the waste heat,
so they probably won't want to heat it directly with the core. They will
conduct heat to it and then have a system that efficiently radiates away
the excess.

--
__________________________________________________ ___
Quibbler (quibbler247atyahoo.com)
"It is fashionable to wax apocalyptic about the
threat to humanity posed by the AIDS virus, 'mad cow'
disease, and many others, but I think a case can be
made that faith is one of the world's great evils,
comparable to the smallpox virus but harder to
eradicate." -- Richard Dawkins

If an MHD, you have exhaust that can be an additional, albeit minor, source of
thrust.

(MSu1049321) writes:

If an MHD, you have exhaust that can be an additional, albeit minor,
source of thrust.

I think you will find that to produce a reasonable amount of power, you
will need to use a rather significant (i.e., not a "minor") flow of mass,
which would quickly exhaust your supply of working fluid unless you are
running a "closed cycle" MHD unit...


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

Damon Hill wrote in message 36...
(Henry Spencer) wrote in
:
Nobody's made any decisions at that level of detail. It
might well do something like thermionic conversion.

How would thermionic conversion work? I keep imagining
a big vacuum tube triode set up as an oscillator...
The cathode being directly heated by the reactor.

This is not a theoretical technology, it's not quite off
the shelf at the moment, but it's proven technology. It
works very simply, just about how you describe, except
using solid state systems. It was a feature of the,
functional, Russian Topaz-2 space nuclear reactor.

Damon Hill writes:

(Henry Spencer) wrote in
:

In article
, Asherian
wrote:
Does anybody know whether Project Prometheus is going to
use a turbine-driven generator or an MHD?

Nobody's made any decisions at that level of detail. It
might well do something like thermionic conversion.

How would thermionic conversion work? I keep imagining
a big vacuum tube triode set up as an oscillator...
The cathode being directly heated by the reactor.

No triodes required --- just a diode: The hotter of two electrodes
"boils off" more electrons than the colder electrode, leading to a
potential difference net flow of electrons from the "hot" to the "cold"
electrode. Also, the space between electrodes is not usually a vacuum,
but usually contains an easily ionized alkali metal vapor such as cesium,
to neutralize the space-charge density of the electron flux.


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

(Asherian) wrote


Does anybody know whether Project Prometheus is going to use a
turbine-driven generator or an MHD?

What little has come out, mostly relative to JIMO, leads me to
think that they're intending to revive SP-100 as a first step.
IIRC, the baseline SP-100 design used thermoelectric converters,
though there was consideration of thermionic or dynamic upgrades.

Manned Mars propulsion will require something beyond that.

(Allen Thomson) wrote in message . com...
(Asherian) wrote


Does anybody know whether Project Prometheus is going to use a
turbine-driven generator or an MHD?

What little has come out, mostly relative to JIMO, leads me to
think that they're intending to revive SP-100 as a first step.
IIRC, the baseline SP-100 design used thermoelectric converters,
though there was consideration of thermionic or dynamic upgrades.

Manned Mars propulsion will require something beyond that.

Science Daily just had a release from Los Alamos that's related; you
might have seen it at other sites, too.

quote
Los Alamos Leading Fast-paced Reactor Research To Power Planned
Journey To Jupiter's Icy Moons

LOS ALAMOS, N.M., Feb. 10, 2004 -- A proposed U.S. mission to
investigate three ice-covered moons of Jupiter will demand fast-paced
research, fabrication and realistic non-nuclear testing of a prototype
nuclear reactor within two years, says a Los Alamos National
Laboratory scientist.

The roots of this build and test effort have been under way at Los
Alamos since the mid-1990s, said David Poston, leader of the Space
Fission Power Team in Los Alamos' Nuclear Design and Risk Analysis
Group.

NASA proposes using use electrical ion propulsion powered by a nuclear
reactor for its Jupiter Icy Moons Orbiter, an element of Project
Prometheus, which is scheduled for launch after 2011. However, the
United States hasn't flown a space fission system since 1965.

Poston discussed technical requirements for such a fission reactor in
two presentations Monday at the Space Technology and Applications
International Forum in Albuquerque. Los Alamos is a co-sponsor of the
forum. Poston discussed "The Impact of Core Cooling Technology Options
on JIMO Reactor Designs" and "The Impact of Power and Lifetime
Requirements on JIMO Reactor Designs."
/quote

and

quote
Most researchers have agreed on the best fuels and reactor
construction materials for the proposed fast-spectrum, externally
controlled JIMO reactor. The major design choice that remains is how
best to transport power from the reactor core to the power conversion
system.

Los Alamos and NASA are examining three primary options for core
cooling: pumped liquid-metal sodium or lithium; sodium or lithium
liquid metal heat pipes; and inert helium or helium-xenon gas. Many of
these options have been tested for decades for terrestrial reactors,
but the reactor for JIMO would be unique, Poston said.
/quote

The original is at Los Al's site:
http://www.lanl.gov/worldview/news/r...e/04-005.shtml

/dps