Help - Search - Members - Calendar
Full Version: New Frontiers 3 - updates
Unmanned Spaceflight.com > EVA > Exploration Strategy
vjkane
NASA posted this update on its website today. No nuclear power for the next mission and list of acceptable candidate missions likely to come this spring:

"The National Aeronautics and Space Administration (NASA) Science Mission Directorate (SMD) plans to release an Announcement of Opportunity (AO) for the third New Frontiers (NF-3) mission no earlier than June 2008. Downselection would occur in 2009. This NF-3 AO will solicit only missions that do not require nuclear sources for power generation or propulsion.

Once the National Research Council's (NRC's) New Opportunities for Solar System Exploration (NOSSE) committee reports to NASA on mid decade NF science mission priorities in March 2008, NASA plans to release more details about allowed targets for the upcoming NF-3 AO."

http://www.spaceref.com/news/viewsr.html?pid=27162
nprev
Kind of puzzled about the prohibition on RTGs; is this just to stay within the cost cap? It sure as hell rules out any outer-system proposals.
vjkane
QUOTE (nprev @ Feb 27 2008, 08:50 PM) *
Kind of puzzled about the prohibition on RTGs; is this just to stay within the cost cap? It sure as hell rules out any outer-system proposals.

My understanding from other websites is that it is primarily to stretch out the availability of the existing plutonium supply. If I remember correctly, MSL and the next Flagship missions use up the bulk of the remaining supply. After that, NASA wants to switch to Stirling-based power supplies, but probably isn't willing to commit a New Frontiers class mission to be the first flight demonstration.

Cost may also be a consideration, although I have not heard that mentioned.

All missions currently in the queue -- lunar sample return, comet sample return, Venus lander, Saturn probe (and I think I'm missing one) -- can be done with solar power.
Mariner9
Yeah, for the first time in my life I'm bummed that the US does not have an active nuclear weapons production program. At least then we would have supplies of plutonium around.

From what I remember reading, Alan Stern is dividing up the plutonium (that NASA gets) between the MSL, the expected ballpark requirement for the Flagship mission, and then one Sterling RTG powered Discovery class mission.

I'm not really sure why it is limited to Discovery and not allowed on New Fronteirs. One reason may be flight duration. New Fronteirs mission budgets are big enough that outer planet missions are practical (and indeed, the first 2 missions in the program are to the outer planets). An outer planets mission is likely to be operating much longer than an inner planets probe. Unlike a tradition RTG (which has no moving parts) the Stirling generators are comparatively new and I don't think anyone has tried running one continuously for 10 years.

A real shame, because I still want the New Fronteirs class Io Observer that volcanopele keeps wishing for.
nprev
Thanks, VJ; makes sense. They might also be trying to drive innovation by imposing such a fundamental constraint, but I'm still not wild about it.

Increasingly, the outer Solar System is where most of the really intriguing things in planetary exploration seem to be, and it would be nice to see a process/administrative framework dedicated to encouraging its exploration. Solar-powered Saturn probes are just barely within the realm of the possible, but for Uranus & beyond...fuggetaboutit.
vjkane
QUOTE (Mariner9 @ Feb 27 2008, 11:29 PM) *
is limited to Discovery and not allowed on New Fronteirs. One reason may be flight duration. New Fronteirs mission budgets are big enough that outer planet missions are practical (and indeed, the first 2 missions in the program are to the outer planets). An outer planets mission is likely to be operating much longer than an inner planets probe. Unlike a tradition RTG (which has no moving parts) the Stirling generators are comparatively new and I don't think anyone has tried running one continuously for 10 years.

I talked with a guy in NASA advanced technologies about this. Stern wants to limit the risk both of $s and time (i.e., no ten year missions that might fail before data collection). There are a number of interesting missions that could be done with two pairs of Sterling engines and electric propulsion, but only one pair is allowed in the Discovery mission. So I am really going to be curious to see what is proposed. My guess is that a lunar polar crater rover or a Mars network station will win out. A repeated Io flyby mission would be nice, but I don't think you can do that on a Discovery budget even with a free Sterling engine.
nprev
QUOTE (vjkane @ Feb 27 2008, 04:27 PM) *
Stern wants to limit the risk both of $s and time (i.e., no ten year missions that might fail before data collection).


That's sort of a surprising statement given the demonstrated longevity of recent missions. The state of the art seems to lend a lot of credence to the idea of spacecraft surviving at least ten years, particularly for orbiters or fly-bys that don't have to cope with the ancillary factors introduced by planetary environments. Is this focus on short-term projects perhaps driven by a need to conserve costs incurred by maintaining ground support teams?
vjkane
QUOTE (nprev @ Feb 28 2008, 01:46 AM) *
That's sort of a surprising statement given the demonstrated longevity of recent missions.

My understanding is the concern that the Sterling engine would have to perform for the full 10-15 year period, not with any other part of the spacecraft. I think this makes sense. Who would want to bet $500M on a new piece of technology with moving parts lasting 10-15 years if the entire scientific payback could only come at the end of that period? I could easily see a mission that would have earlier payback, and then a mission of opportunity that bet a small amount of money on that the engines would last that long. I think the Sterling engines would last 10-15 years, but if I were the manager with the budget authority and responsibility to the taxpayers, I would pick a demonstration mission that paid back within a much shorter time period.

I would not be at all surprised to see NASA keep whatever craft is launch alive for as long as possible just to monitor the long term performance and possible failure of the Stirling Engine. Sounds like a great candidate for a Mars Network station, although I don't know that a lander could fit in the Discovery budget.
nprev
Okay, gotcha now; I wasn't thinking in terms of the Stirling engine alone.

Frankly, they probably should do an LEO/MEO technology demo flight before committing to using it on planetary missions; lots of Earth science objectives still exist, and you can still have an array in place as a backup in case the thing dies prematurely.
dvandorn
QUOTE (Mariner9 @ Feb 27 2008, 04:29 PM) *
Yeah, for the first time in my life I'm bummed that the US does not have an active nuclear weapons production program. At least then we would have supplies of plutonium around.

The U.S. alone has more than twenty thousand thermonuclear devices, at varying states of age and maintenance, lying around in storehouses around the world. Most of them contain a fair supply of weapons-grade plutonium. We're probably talking *tons* of weapons-grade plutonium in existence today.

How many weapons would you have to cannibalize to construct enough RTGs for, say, a dozen outer-planet missions? One? Ten? Twenty?

Is it at least *possible* that we need those outer planet missions more than we need those very few weapons (out of a large stockpile)?

It just seems to me that saying there's a shortage of plutonium is not correct. We just have to be willing to lose a few bombs out of an enormous stockpile in order to replenish the supply available for RTGs.

-the other Doug
nprev
Don't forget half-life burn-out, oDoug, to say nothing of engineering considerations. I strongly suspect that dismantling weapons to harvest Pu might well be more expensive, labor-intensive, and produce less of a yield then producing it directly from reactors for the express purpose of using it for UMSF. (Also don't forget that there's a very narrow bottleneck for any such process: the Pantex plant in Amarillo, TX.) My thinking here is that NASA needs to submit a requirement to DOE to cover missions that will launch over the next 10-15 years, and continue doing so.
mchan
QUOTE (Mariner9 @ Feb 27 2008, 02:29 PM) *
Yeah, for the first time in my life I'm bummed that the US does not have an active nuclear weapons production program. At least then we would have supplies of plutonium around.

Nuclear weapons production is not directly related to the production of Pu-238 used in RTGs / SRGs. The same reactors may be used to produce Pu-238 and Pu-239 (for weapons), but the feedstock and breeding profiles are different. A reactor being used to produce Pu-238 can't be used to produce Pu-239 at the same time.

Side note: there is an excess of Pu-239 around from retiring and dismantling a large part of the huge stockpiles from the Cold War. Can't use it for RTGs / SRGs, though.
nprev
Ah! Very enlightning, MC; thank you! smile.gif

Guess the question then becomes what is the demand for Pu-238? Damned if I can think of any besides UMSF...so, it's even more critical that NASA asserts its needs.
centsworth_II
Wikipedia mentions one other use (now obsolete):
"...as of 2003 there were somewhere between 50 and 100 plutonium-powered
pacemakers still implanted and functioning in living patients."
ohmy.gif
http://en.wikipedia.org/wiki/Plutonium
vjkane
QUOTE (nprev @ Feb 28 2008, 05:39 AM) *
Guess the question then becomes what is the demand for Pu-238? Damned if I can think of any besides UMSF...so, it's even more critical that NASA asserts its needs.

I've read that there is a game of budgetary chicken going on. DOE wants NASA to foot the entire start up bill for restarting the production of the correct type of plutonium.
mchan
Past budget documents for Pu-238 production have referred to two users: NASA and national security. The Ivy Bells recording devices attached to Soviet undersea communications cables are speculated to be powered by RTGs. The CIA lost an RTG in the Himalayas in the mid 60's.

A recent NY Times article refers to continued use by national security --

http://www.nytimes.com/2005/06/27/politics/27nuke.html
vjkane
This tidbit on the Stirling engine proposals was at http://ssedso.gsfc.nasa.gov/initiatives/lu...unar_GSFCV2.pdf (which is quite a worthwhile presentation to read over on SMD's overall direction and lunar missions):

Discovery and Mars Scout Mission Concept Studies
New concepts using a GFE - Radioisotope Power System
Received 41 proposals - 14 Lunar mission concepts
Evaluation in February with selection in March
Mariner9
Does anyone know if the next Discovery mission is certain to be one of the Stirling proposals? Alan Stern made a big deal about soliciting proposals for missions that could use the Stirling. But it sounded at the time that NASA was mostly trying to determine just what missions were possible under a Discovery budget but had never been proposed because they would need nuclear power (and in this case a more efficient nuclear power source).

My point is this: Are the current studies aimed directly at making the next Discovery mission nuclear powered? Or, will the studies be completed for information gathering only, and then the top contenders be allowed to be submitted during the next general Discovery AO, competing against whatever else is submitted?
tedstryk
This is a really interesting document about solar power in the outer solar system.


http://www.lpi.usra.edu/opag/nov_2007_meet...solar_power.pdf

Might be applicable here.
vjkane
QUOTE (Mariner9 @ Feb 28 2008, 05:23 PM) *
Does anyone know if the next Discovery mission is certain to be one of the Stirling proposals?

I don't know that it's certain, but they want good proposals to be ready to compete. I presume that two equally good proposals, one Sterling engine and one solar powered, will favor the Sterling engine.
nprev
QUOTE (tedstryk @ Feb 28 2008, 12:37 PM) *
This is a really interesting document about solar power in the outer solar system.


Yes, it was, Ted; thanks!

I'm sort of surprised that the authors didn't mention the deployment risk for some of these monster arrays (250 m2 for a Uranus orbiter!!!) In fact, that's so large that it would probably place maneuvering constraints in terms of max delta-V in order to avoid warping the arrays & possibly messing up inter-cell connections/harnesses.
ugordan
QUOTE (nprev @ Feb 29 2008, 02:53 PM) *
In fact, that's so large that it would probably place maneuvering constraints in terms of max delta-V in order to avoid warping the arrays & possibly messing up inter-cell connections/harnesses.

Slight correction there: not delta-V, but acceleration.
nprev
Der...yes, of course. I was thinking about course corrections to impart delta-V (esp. orbital insertion burns), done went & stepped on my tongue; thanks, UG! smile.gif
Paolo
From the National Academies Press:
Opening New Frontiers in Space: Choices for the Next New Frontiers Announcement of Opportunity
gpurcell
QUOTE (Paolo @ Jul 29 2008, 06:48 PM) *



Thanks for the link, Paolo.

A quick read through Chapter 2 leads me to believe the door has been kicked wide open for another Jupiter mission for NF3 if it can be brought in under the cost cap.
vjkane
QUOTE (gpurcell @ Jul 29 2008, 08:04 PM) *
A quick read through Chapter 2 leads me to believe the door has been kicked wide open for another Jupiter mission for NF3 if it can be brought in under the cost cap.

It has been, although I cannot see NASA selecting both a Jovian Flagship and New Frontiers mission. If the Flagship decision goes to Enceladus/Titan, however, a Jovian New Frontiers mission could be chosen. The problem, however, is that for this round, nuclear fuel sources are ruled out. A mission to Jupiter could be done with solar cells, but the most interesting targets (in my opinion) -- Europa and Io -- may be difficult even for repeated flybys because of the effects of radiation on those cells. It may also be hard to fit the radiation hardening of the electronics within that budget to enable study of those moons. If the only viable targets are Ganymede and Callisto, I'm not sure the mission would fair well in the selection process.
Mariner9
It is hard to imagine a solid Io or Enceledus mission using solar cells.

It is also hard to imagine a Discovery Class Io Observer using a Strirling Nuclear generator, although one is currently under study.

Now if only we could get those two combined ....

ah heck, as long as I'm wishing for something I'll wish for a large cache of previously unknown cheap plutonium to become available in the next 6 months
tedstryk
What I could see happening, particularly if Io gets the NF funding and Titan gets the flagship, is that the Io mission morphs into sort of a Galileo 2 mini-flagship, particularly if plutonium does become available.
vjkane
QUOTE (tedstryk @ Jul 31 2008, 09:28 PM) *
What I could see happening, particularly if Io gets the NF funding and Titan gets the flagship, is that the Io mission morphs into sort of a Galileo 2 mini-flagship, particularly if plutonium does become available.

The problem, as I understand it is the radiation hardening of the electronics. A NASA presentation suggested that a Europa mission could be done with solar cells (i.e., they would work long enough to enable the mission before radiation damage, but the presentation also said that more study was needed)

To avoid the radiation damage to the electronics, the Discovery proposal is inclined (this is from memory) 45 degrees to the Jovian equator. It is hard to then have the orbiter flyby other moons. Not impossible -- one could envision a mission with sufficient fuel to raise the periapsis to the orbit of Ganymede, where gravity assists could reduce the inclination. Galileo did a periapsis raise from within Io's orbit to (I think) between Europa and Ganymede's orbits.

If a Galileo II was done, it could do much more intensive studies of the moons. Any Galilean moon orbiter pumps the orbit down so that frequent flybys occur. A Galileo II could do this and encounter the same moon repeatedly. An old NASA article even showed that the latitude of encounter could be varied by encountering the moon in slightly different locations (the Jovian point of periapsis changes longitude and "walks" around the planet).

I don't want to come across as a naysayer. My favorite mission choices are Titan for the Flagship mission and a Jovian Galileo II for the New Frontiers (followed by a Saturn/Neptune/KBO plutonium powered New Frontiers for the selection after that). It's just that pesky radiation that makes it hard to do it cheaply...
hendric
What about using a solar concentrator to drive a Sterling engine? Granted, it would require more pointing accuracy, and a gimballed solar wing, but it would be radiation proof. If the concentrator had a decent heat storage capability, it could provide power during the night side as well. Be an interesting CubeSat experiment! smile.gif

Here is an oddly appropriate announcement. I don't know how much this might improve current RTG power, or reduce the amount of material necessary, but any improvement in either is good!

http://www.spectrum.ieee.org/jul08/6496
This is a "lo-fi" version of our main content. To view the full version with more information, formatting and images, please click here.
Invision Power Board © 2001-2014 Invision Power Services, Inc.