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Unmanned Spaceflight.com _ Exploration Strategy _ Nuclear-powered Discovery Mission?

Posted by: Mongo Jan 8 2008, 09:12 PM

Emily's blog entry from today seems not to have been mentioned here yet: http://www.planetary.org/blog/article/00001285/

This would be absolutely huge, if it pans out. From the blog:

QUOTE

Alan explained to me that the Stirling generator is almost ready for prime time. They have years of simulated time running the generator, and next month, they're going to fire up a flight model and run it for a year. Once it's run for a year without incident, he told me, he'd be quite comfortable seeing it on a Discovery mission, though not on an outer planets flagship mission. He said he wouldn't risk putting a never-flown power supply on the flagship mission, not without seeing it run successfully on a cheaper mission first.

You might wonder what principal investigator would be willing to take on this risk, but Alan told me there's a lot of appetite out there for a nuclear-powered Discovery mission because of all the possibilities it opens up. He said that Jim Green (director of the Planetary Science Division of NASA's Science Mission Directorate) put out a call for mission concept proposals, asking the science community what they'd do if the next Discovery mission was nuclear-equipped. He said they got more than forty proposals, of which they plan to select ten and fund them for a yearlong study. The proposals included all kinds of stuff previously inconceivable for Discovery: go look for ice at the lunar poles with a rover; go rendezvous with a Centaur, one of the small bodies like Chiron or Pholus that orbits in the outer solar system and may be an interloper from the Kuiper belt; send a probe into Saturn's atmosphere; go land on Mercury.

Huge, huge news.

Bill

Posted by: vjkane Jan 8 2008, 09:47 PM

You can read details of the announcement at http://nspires.nasaprs.com/external/viewrepositorydocument/cmdocumentid=113068/C.26%20DSC%20Mission%20Concepts.pdf. Net: free stirling engine with 280W at beginning of mission (6720 watt-hours/day compared to Opportunities' current 635.) Proposals must be enabled by the use of nuclear; can't just substitute solar for nuclear.

My concern with this offer is that I'm not sure how many mission opportunities it really opens up. Phoenix busts the Discovery budget and already had a pre-built spacecraft and entry shell. New Horizons (about the simplest outer planets mission possible) is 2X the Discovery budget. So other than a rover in the polar craters on the moon, what missions are enabled that will fit within the Discovery budget? It's that money thing that is tripping up my imagination. Apparently not the scientific communities since I've been told that dozens of ideas were submitted.

So, I'd like to encourage everyone else to show how limited my imagination is. What mission capabilities would this enable that would fit withing Discovery budget?

Posted by: ngunn Jan 8 2008, 09:50 PM

QUOTE (Mongo @ Jan 8 2008, 09:12 PM)

Emily's blog entry from today seems not to have been mentioned here yet:

Actually I posted the link a few minutes before you - in 'OPAG reports', but then I was reacting to different news!

Agreed, the nuclearised Discovery idea is interesting. But if the Stirling uses so much less plutonium why blow almost all the available supply on one 'old technology' mission when you could save it and fly six or seven Stirlings?

Posted by: mchan Jan 9 2008, 04:55 AM

Moving parts. Stirling prototypes have run for years in Earth labs, but have yet to run in space for any long duration. Even the ion thrusters on Dawn (actually their immediate forebears) have flown before on Deep Space 1. This would as much a New Millenium type technology mission as a Discovery mission.

The ASRG is being supplied gratis and the cost cap is $450 million to include launch. Discovery / Scout implies (politically) at least the Dawn levels of US content, e.g., the launch, at least 1 major instrument, and the spacecraft itself. Using Dawn as an example, get an ESA country or Japan to supply as many major instruments that they can contribute.

US launch in the timeframe mean an EELV which will run at least $130 million going by the recent NASA contracts. Assuming the cheapest EELV gives twice the payload capability as a DeltaIIH opens up sizable missions from Mercury to Mars and perhaps beyond if Earth gravity assists are used. So you have $320 million for the spacecraft plus 1 instrument plus operations costs, plus 2 or 3 more instruments from international partners.

The ASRG needs to be an enabler, so someplace with little or no sunlight, so here are a few rather derivative missions:

A Phoenix which operates thru the Martian polar winter.

A New Horizon on the 2016 Jupiter, Saturn, Neptune, KBO flyby trajectory mentioned in the OPAG thread with intenational partners supplying a simple probe for Saturn or Neptune might be possible if an international partner would also supply the launch, or using Earth gravity assists with trying to reduce long flight time operations cost with increased use of hibernation during cruise.

A Dawn that goes out to the Trojans or possibly even Chiron.

Posted by: vjkane Jan 9 2008, 07:00 AM

I would really, really like to see the Jupiter > Saturn > Neptune > KBO mission, even if it doesn't have an atmospheric probe (but it should!). Since the booster only has to get the craft to Jupiter and crazy speed (probably) isn't needed, then we could probably do with a much cheaper launcher than New Horizons used. Even better if another nation launches it. Which means they would also help pick up the costs of the instruments. So maybe, although I don't know if Stern will want to wait that long (2016 for launch).

Another possibility would be the Jupiter Trojans, although those could be solar powered (just).

Other ideas?

Posted by: mps May 8 2009, 02:37 PM

Didn't find a suitable thread and didn't want start a new one, so I'll post it here.
http://www.msnbc.msn.com/id/30621668/

Posted by: nprev May 8 2009, 02:49 PM

That's excellent news, thanks! I saw a version of this article yesterday that described the shortage, but no mention of DoE's intent to resume production.

Posted by: Mongo May 14 2009, 10:05 PM

There's an http://futureplanets.blogspot.com/2009/05/interesting-charts.html about the restart of Pu-238 production over at the Future Planetary Exploration blog. In particular, it contains these three charts:

Posted by: ngunn Oct 4 2009, 09:57 PM

Not sure where to put this - hope here's OK.

http://www.sciencedaily.com/releases/2009/10/091004020806.htm

Posted by: Vultur Oct 5 2009, 06:39 AM

A Centaur mission would be really cool. So would a long-term lunar-south-pole-crater mission, especially if LCROSS finds water there.

QUOTE (mchan @ Jan 9 2008, 05:55 AM)

Moving parts. Stirling prototypes have run for years in Earth labs, but have yet to run in space for any long duration

This may be a stupid question ... but can't they put them in vacuum and bombard them with radiation, even in Earth labs? And if they can replicate the space environment, what is the difference?

Posted by: djellison Oct 5 2009, 07:31 AM

Zero G?

Posted by: centsworth_II Oct 5 2009, 03:45 PM

I don't know how significant it is, but I don't think cosmic rays can be produced in Earth testing.

Posted by: mps Oct 20 2009, 08:06 AM

http://www.spacenews.com/policy/pu-238-restart-denied-with-final-passage-energy-bill.html

Posted by: vjkane Oct 20 2009, 03:29 PM

QUOTE (mps @ Oct 20 2009, 08:06 AM)

http://www.spacenews.com/policy/pu-238-restart-denied-with-final-passage-energy-bill.html

I haven't discussed this on my blog yet because it's not clear what the implications are. As I understand it, the plutonium crunch for the coming decade was projected based on needs from the manned spaceflight program (gotta deal with those 14 day nights on the moon). With the manned moon program in question, my understanding is that funds are withheld pending resolution of whether or not there is a need in the next decade or two.

Posted by: stevesliva Nov 23 2009, 08:14 PM

There may be some hope from private industry:
http://www.technologyreview.com/energy/23959/?nlid=2550

Medical device makers using medical isotopes to make long-lived batteries. The buzzword is betavoltaics.

No doubt the currents from these things are pretty small, though.