“But nukes also have technical obstacles to overcome at these scales, and potentially greater costs and political issues.”

It’s not a matter of costs or political issues those can be resolved.

Again is say gov’t and industry are not in the same cooperative mood as in the ’70′s. It does not compare to today’s political realities where a larger independent political mindset upset with business-as-usual Rep/Dem duopoly is not getting the job done anywhere. Which is my point there needs to be mechanisms to establish a relationship again.

Remedy:

-political issues: Increase political participation allow muli-party elections.
-costs issues: bring some sanity in the type of macro-economics that policy is set to. Keynesian economics only prolongs the economic crash replace with Austrian economics would bring common sense into affordability.

“Maybe someday VASIMR or another ion engine will catch up, but Rover and NERVA set a very high bar.”

At this point in time nothing trumps NTR by far. Rover/NERVA already did the work a template is already established its time now to put it to use for a real space program the public has waited long enough !

It time for space agencies to get real and stop wasting money.

I wouldn’t argue with any of your points. I was just pointing out that “theoretically” a very advanced solar array could replace nukes even on the MW-class applications. I agree that solar has more technical obstacles to overcome than nukes at these scales. But nukes also have technical obstacles to overcome at these scales, and potentially greater costs and political issues.

“VASIMR… does not compare with NTR thrust power and development.”

There is no doubt about that at this point in time. Maybe someday VASIMR or another ion engine will catch up, but Rover and NERVA set a very high bar.

FWIW…

The FY 2007 budget, rolled out in February CY 2006, shows the Prometheus cut.

http://www.nasa.gov/pdf/142458main_FY07_budget_full.pdf

The Prometheus cut does _not_ show up in the FY 2006 budget, rolled out in CY 2005.

http://www.nasa.gov/pdf/107486main_FY06_high.pdf

And for what little it’s worth, the wikipedia entry for Project Prometheus also confirms the 2006 termination, not 2005.

“I am not confusing nuclear power with nuclear propulsion”

I didn’t say that. I said you were confusing the nuclear power and propulsion technology program (Prometheus) with the Jupiter Icy Moons Orbiter (JIMO) mission, which employed those technologies.

“My point was that anything smacking of nuclear energy, is fraught with expense and NASA has virtually no chance to fund it. Look at P-238 for chris-sake.”

A bad example. Congress rejected DOE’s Pu-238 production restart request last year because they want to see the users (NASA and classified users) contribute. It has nothing to do with RTG expenses, which are a very small fraction of the costs associated with a space nuclear reactor.

And plutonium is Pu, not P.

“A working space qualified nuclear reactor is billions of dollars in R&D away followed by billions in developing a system to use it. Pipe dream in this climate.”

And tens of billions to finish Constellation is not?

FWIW…

“Very large and very efficient solar arrays could theoretically replace nukes even for the megawatt-class propulsion applications.”

-Solar Arrays tend to limited to the mass in area sq. largest flown 50kw.
-vibration and uneven distribution and heat build up (problems with large arrays on ISS due to mechanical vibration (see press articles)
-Dramatic drop in solar power with distance from sun AU distance even with thin film arrays.
-induces collection loss and illumination non uniformity, reducing the PV efficiency.
-Problems with fitting super large arrays in launch faring and deployment
-Problems with solar arrays in soil-firma operations dust and weathering limitations reduce power.

You can’t manipulate the physics from the source (sun) for solar power.
You can manipulate the physics from the source (reactor) heat sinking.

VASIMR is still feeble propulsion and is totally dependent on it’s power source. I has limited potential but it does not compare with NTR thrust power and development.

Ares I hadn’t even been invented. The end of Prometheus was due to return to flight of Shuttle, restoring Hubble and a host of other reasons.
I am not confusing nuclear power with nuclear propulsion. My point was that anything smacking of nuclear energy, is fraught with expense and NASA has virtually no chance to fund it. Look at P-238 for chris-sake. A working space qualified nuclear reactor is billions of dollars in R&D away followed by billions in developing a system to use it. Pipe dream in this climate.

I’m full of “of”?

What exactly does an “authority thought” sound like?

“It was canceled in 2005 because its costs had ballooned to 11 billion and NASA needed funds to pay for Shuttle return to flight, Hubble repair bills and lawmaker pork.”

Prometheus ramped down from about a half-billion dollars in 2005 to $100 million in the 2006 budget to pay for Ares I/Orion from the ESAS rollout in fall the prior year. Nearly all of that remaining $100 million went to close down the program.

Also, you’re confusing the nuclear power and propulsion program (Prometheus which never experienced ballooning costs) with the JIMO mission (which did experience ballooning costs).

“Griffin hadn’t been in office one month before he canceled it.”

Wrong. Griffin became Administrator in April 2005. Prometheus ramped down in 2006, a year later.

“In fact Prometheus was a big R&D program for game changing, bold technologies to cruise around the solar system far faster than was possible”

Yes, it was. No one said it wasn’t.

“I bet the airy fairy nonsense in Obama’s bill will also be cut to pay for pressing Nasa operations too. And soon.”

Unlikely. With Shuttle retirement, NASA’s operational burden is going down.

FWIW…

It was canceled in 2005 because its costs had ballooned to 11 billion and NASA needed funds to pay for Shuttle return to flight, Hubble repair bills and lawmaker pork. Griffin hadn’t been in office one month before he canceled it. Ares I and Constellation didn’t exist. In fact Prometheus was a big R&D program for game changing, bold technologies to cruise around the solar system far faster than was possible. Sound familiar? It was nuked to pay for more pressing operational needs. I bet the airy fairy nonsense in Obama’s bill will also be cut to pay for pressing Nasa operations too. And soon.

Prometheus was terminated by Griffin to generate funding for Ares I/Orion. Nothing to do with nuclear propulsion per se.

“Also does anyone know if Vasimir can be useful without a nuclear power plant?”

VASIMIR has multiple applications (station reboost, slow cargo propulsion, fast human propulsion, etc.) at different power levels (kilowatt versus megawatt). Very large and very efficient solar arrays could theoretically replace nukes even for the megawatt-class propulsion applications. But whether arrays can be deployed and maintained and whether technical issues like spacecraft charging could be overcome affordably remains to be seen. (But similar issues are true for a megawatt-class nuclear plant, which has also never been developed for and operated in space.)

“When Bolden was prattling about zipping around the solar system in a matter of weeks, I wonder what new technology he had in mind?”

I won’t pretend to read his mind, but there are equally capable in-space propulsion concepts and technologies, some of which have been around for decades, besides VASIMIR.

FWIW…