[X] My Assistant

[Mark6]

Today I heard this on NPR: Exploring a moon by boat

The mission could launch around 2016 and be sailing on Titan around 2022 — if this team gets through a highly competitive selection process to get funding from NASA. Stofan and her colleagues are busy working up their proposal for when NASA begins to accept ideas for future Discovery-class missions.

Quick Google search on Dr. Stofan's name found this: What Next for Titan?

Ellen Stofan has a Discovery-class Titan lake lander proposal. I've not seen the presentation, but a friend who has tells me that it is less capable than the ESA lake lander proposed for TSSM. (This would make sense – ESA had a budget of ~$1B for just the lake lander and balloon. Stofan has just $450M and has to fit a carrier craft and launch vehicle into that budget.) The 2007 report did not look at lake landers. I know of Stofan by reputation, and she's highly competent. However, fitting in a carrier, lander (with entry shell), and launch vehicle within a Discovery mission budget seems ambitious. Perhaps this could be done with a New Frontiers budget ($650M with the launch vehicle provided by NASA outside this budget), although the 2007 budget suggested that a budget twice this amount would be needed just for an atmopheric probe.

Aside from above quote's understandable skepticism of the Discovery-class price tag, where would plutonium for this mission come from? I thought it is all already allocated?

[dvandorn]

It's a wonderful example of how observing affects the thing being observed.

I'm also just a tiny bit skeptical that you can vent the heat from the boat's warm interior (including waste heat from the ASRGs) up into the air and not have any effect on the temperature or composition of the fluid in which you're floating your boat. At the very least, you will heat a column of air over the boat that will cause chemical reactions in the liquids and gases suspended in the heated air column. Products of those reactions will tend to fall back out of the air column, and if they're heavy enough they'll land in the fluid. Most of this fallout would happen near the boat, I would think. So, anything your vented heat precipitates out of the "humid" air will then change the nature of the air and the fluids you're observing.

Also, what happens if the atmosphere over the lake contains an inversion layer that traps the "superheated" air close to the lake surface? We're talking about a rather thick atmosphere, here. Microclimates might well come into existence in such conditions that we don't know enough to model very well, and they could not only trap hot air for short periods, they would also be disrupted by hot, dry air, making our observations of them resemble Mike's burnt tree branch.

I just keep thinking, even if the heat released is relatively low by our standards (under 100 degrees C), the difference between that and the boiling point of the fluids they're in is much larger than you'd think. I'd imagine that if you applied the same degree of difference to, say, the boiling point of water, it would be something like trying to examine the ocean from a boat that's venting white-hot plasma at 5,000 degrees C. Your water collectors, designed to tell you all sorts of things about the chemistry and properties of the seawater, might just end up picking up a bunch of charred feathers and bird carcasses and leave you trying to understand how those fit in with your model of the oceanic environment...

-the other Doug

[Drkskywxlt]

It's a wonderful example of how observing affects the thing being observed.

I'm also just a tiny bit skeptical that you can vent the heat from the boat's warm interior (including waste heat from the ASRGs) up into the air and not have any effect on the temperature or composition of the fluid in which you're floating your boat. At the very least, you will heat a column of air over the boat that will cause chemical reactions in the liquids and gases suspended in the heated air column. Products of those reactions will tend to fall back out of the air column, and if they're heavy enough they'll land in the fluid. Most of this fallout would happen near the boat, I would think. So, anything your vented heat precipitates out of the "humid" air will then change the nature of the air and the fluids you're observing.

Also, what happens if the atmosphere over the lake contains an inversion layer that traps the "superheated" air close to the lake surface? We're talking about a rather thick atmosphere, here. Microclimates might well come into existence in such conditions that we don't know enough to model very well, and they could not only trap hot air for short periods, they would also be disrupted by hot, dry air, making our observations of them resemble Mike's burnt tree branch.

I just keep thinking, even if the heat released is relatively low by our standards (under 100 degrees C), the difference between that and the boiling point of the fluids they're in is much larger than you'd think. I'd imagine that if you applied the same degree of difference to, say, the boiling point of water, it would be something like trying to examine the ocean from a boat that's venting white-hot plasma at 5,000 degrees C. Your water collectors, designed to tell you all sorts of things about the chemistry and properties of the seawater, might just end up picking up a bunch of charred feathers and bird carcasses and leave you trying to understand how those fit in with your model of the oceanic environment...

-the other Doug

Doug...the waste heat is absolutely an issue and was brought up by a Decadal Survey panelist when Dr. Stofan presented. They plan to have the heat radiators on the top of the "boat", but they do recognize that they will be a warm bubble traveling through a very cold liquid. She mentioned that it is an issue that they will address in greater detail for their official Discovery proposal later this year/early next year.

[dvandorn]

Doug...the waste heat is absolutely an issue and was brought up by a Decadal Survey panelist when Dr. Stofan presented. They plan to have the heat radiators on the top of the "boat", but they do recognize that they will be a warm bubble traveling through a very cold liquid. She mentioned that it is an issue that they will address in greater detail for their official Discovery proposal later this year/early next year.

Thanks! I've learned through long experience that when I assume that people have taken into account things that seem extremely obvious to me, and I never say anything, others invariably have missed the same realization. Of course, when I *do* mention these things, it ensures that someone has already considered it and is taking it into account...

-the other Doug