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New Frontiers 3 - updates
mchan
post Feb 28 2008, 05:17 AM
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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
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vjkane
post Feb 28 2008, 02:53 PM
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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


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Mariner9
post Feb 28 2008, 05:23 PM
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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?
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tedstryk
post Feb 28 2008, 08:37 PM
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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.


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vjkane
post Feb 28 2008, 11:03 PM
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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.


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nprev
post Feb 29 2008, 01:53 PM
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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.


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ugordan
post Feb 29 2008, 02:27 PM
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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.


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nprev
post Feb 29 2008, 04:06 PM
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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


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Paolo
post Jul 29 2008, 06:48 PM
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From the National Academies Press:
Opening New Frontiers in Space: Choices for the Next New Frontiers Announcement of Opportunity


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gpurcell
post Jul 29 2008, 07:04 PM
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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.
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vjkane
post Jul 29 2008, 08:28 PM
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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.


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Mariner9
post Jul 31 2008, 07:16 PM
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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
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tedstryk
post Jul 31 2008, 08:28 PM
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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.


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vjkane
post Jul 31 2008, 08:43 PM
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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...


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hendric
post Aug 1 2008, 05:16 PM
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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


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