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Unmanned Spaceflight.com _ Manned Spaceflight _ Manned Landing On Titan

Posted by: nprev Oct 19 2006, 09:08 PM

Just got to thinking about some of the problems that may have to be addressed if & when we ever try to visit Titan in person.

The first thing that comes to mind is what might happen if some Titanian air gets inside an oxygen-rich manned spacecraft, say from minor airlock residue. I imagine that the explosive potential of some of the trace gasses is pretty high, and there's probably also a significant risk of poisonous compounds as well. So, here are some tenative requirements:

1. REALLY efficient air-scavenging airlocks.
2. Surface suits that can't trap external gasses in creases, folds, etc.
3. Spark-proof electrical/electronic everything.
4. Smoking is strictly forbidden (with apologies to the entire 1950s SF movie genre!) rolleyes.gif

Gotta be more...any ideas?

Posted by: RedSky Oct 19 2006, 09:48 PM

In reference to your item #4... here's something from 1960. There was a TV show that tried to "accurately" portray man going into space and to the moon. Here's the lead actor of that series showing he has the right stuff as a macho astronaut... laugh.gif Well... it was 1960, after all. Guess no "lighting up" on Titan. ('Course there always is niccotine gum)


Posted by: volcanopele Oct 19 2006, 09:59 PM

You definitely want a very efficient air filtering system. Obvious flammability aside if enough Titan air got into an enclosed environment, you also have to be concerned about the amount of benzene that a settler would come into contact with: http://www.scorecard.org/chemical-profiles/summary.tcl?edf_substance_id=71%2d43%2d2

Posted by: ngunn Oct 20 2006, 01:15 PM

I would love to go, but I'd prefer to be inside some submarine-like object rather than any kind of body suit.

Posted by: ugordan Oct 20 2006, 01:28 PM

I find it compelling that you could go around on Titan, pick up "rocks" you find interesting and when you get back to the ship, all those rocks just melt away under earthly temperatures. There's something about the fact that entire mountains, everything you see there would just melt if you held it in your hands long enough. Provided you had big enough hands... biggrin.gif

An ocean world in out mindset, yet rock solid... Not to mention even more extreme cases like Triton!

Posted by: JRehling Oct 20 2006, 09:08 PM

The really compelling thing (offset by many hazards) is that the pressure is actually okay for people. That makes it unlike any other solid surface-locales in our solar system.

That would allow for some flimsy suits if it weren't for the extreme cold. Of course, if we sent Minnesotans to Titan, they'd only need scuba gear and a warm hat.

Posted by: mchan Oct 21 2006, 02:28 AM

QUOTE (ugordan @ Oct 20 2006, 06:28 AM) *
I find it compelling that you could go around on Titan, pick up "rocks" you find interesting and when you get back to the ship, all those rocks just melt away under earthly temperatures. There's something about the fact that entire mountains, everything you see there would just melt if you held it in your hands long enough. Provided you had big enough hands... biggrin.gif

An ocean world in out mindset, yet rock solid... Not to mention even more extreme cases like Triton!

If the surface is not very rocky (rocks or water ice rocks), perhaps cross-country skis might be a viable transport mechanism. Adjust heat flow from suit radiators into the skis to avoid freezing in place.

On worlds further out, e.g., more distant TNO's, where the surface is frozen gas, allowing heat radiators in uncontrolled contact with the surface might cause the gas to boil off violently.

Posted by: dvandorn Oct 21 2006, 03:18 AM

QUOTE (JRehling @ Oct 20 2006, 04:08 PM) *
Of course, if we sent Minnesotans to Titan, they'd only need scuba gear and a warm hat.

Yah sure, you betcha!

wink.gif

-the other Sven... or is that Ole?

Posted by: JonClarke Oct 21 2006, 06:19 AM

A slightly higher internal than external pressure would deal with most of the issues of contamination, of the interior.

Jon

Posted by: djellison Oct 21 2006, 09:16 AM

What would be the physiological effects of living at 1.6+ Bar?

I was thinking that you could get away with basically a 'warm suit' with breathing gear ( i.e. the Baxter suggestion in 'Voyage' )

HOWEVER.....

The only way to not contaminate from outside to inside the module via the airlock would be to evacuate it to as near a vacuum as you can at each cycle..

i.e. people put on suits, get in. 'habitable' air then pumped out into a pressure vessel so the airlock is at as near a vacuum as can be made.

THEN - you repressurise with 'titanian' air up to titanian pressue.

On the way back in - shut the door, pump out to a vacuum dumping it to the atmosphere outside, then represurise with the air evacuated before the EVA began...that would minimise the cross contamination in the meantime

BUT

It then means you have to have an EVA suit that can manage a near vacuum so it's going to look more like a modern EVA suit rather than something more minimal that one might immediately assume would be enough for Titan.

maybe smile.gif

Doug

Posted by: nprev Oct 21 2006, 12:19 PM

1.6+ bar and mostly nitrogen to boot. If the lander & EVA suits were pressurized at that level, it sounds like the crew could get a BAD case of the bends when they return to the mother ship unless they decompress...better add a zero-gee decompression chamber to the shopping list! huh.gif

Posted by: tasp Oct 21 2006, 02:09 PM

A vacuum capable airlock might be rather heavy to drag all the way to Titan, maybe the airlock could be a conformal bag, and the pressure difference could squeeze the atmosphere back outside.

Residual gases would still be present but could be dealt with something not too dissimilar to the lithium hydroxide packs, just use a different chemical for the hydrocarbon smog absortion you want.

I suspect flammability won't be much of a concern due to dilution below the ignition concentration (atmosphere is mostly N2 in any regard), but I suspect the smell of the Titanian atmosphere will be hideous.



Posted by: nprev Oct 21 2006, 10:14 PM

Yeah, I suspect that the funk factor of Titan's atmosphere will be pretty significant. At least that will provide some good leak-detection capabilities! smile.gif

Posted by: ugordan Oct 21 2006, 11:27 PM

QUOTE (tasp @ Oct 21 2006, 03:09 PM) *
but I suspect the smell of the Titanian atmosphere will be hideous.

Why would it be hideous? Surely not due to methane itself as the gas is odorless, contrary to popular thinking. As for smog particles, their concentration in the air is probably lower than in a smoggy city back here.

Posted by: tasp Oct 22 2006, 02:00 AM

From the Titan chapter in The New Solar System, I see we might expect besides the nitrogen, methane and argon, to find methyl radicals (CH3), ethane, acetylene, ethylene, polyacetylene, cyanide, and various breakdown products of several of them. I suspect Cassini will be casting a far better understanding of the atmospheric constituents.

It may be possible there is still some ammonia extant there too, perhaps most of the nitrogen in the atmosphere is from dissassociated ammonia after all, and it might be clatharated with the water ice.

I'm still thinking it will be stinky there.

Posted by: JonClarke Oct 22 2006, 09:05 AM

QUOTE (nprev @ Oct 21 2006, 12:19 PM) *
1.6+ bar and mostly nitrogen to boot. If the lander & EVA suits were pressurized at that level, it sounds like the crew could get a BAD case of the bends when they return to the mother ship unless they decompress...better add a zero-gee decompression chamber to the shopping list! huh.gif


A drop in 0.7 bar is not enough to result in the bends when people don in Shuttle EMU. So I don't see why a 0.6 bar drop should be an issue. If it is a concern, the ascent vehcile would require many hours to ascent to orbit and dock to the other ship, during which time the pressure could be gradually lowered. Breathing an atmsophere with a higher partial pressure O2 durting ascent would also speed N2 outgassing, if required.

As for the airlock, what is the rate at which methane and other noxious gases can be removed from the atmosphere, and how is it removed?


Jon

Posted by: nprev Oct 22 2006, 10:56 PM

Oh, okay; so maybe the pressure differential isn't a big deal, then. Thanks! smile.gif

I have no idea how efficiently Titanian air could be scrubbed from an airlock, nor how long it would take. However, if pressure turns out not to be too big an issue physiologically, then keeping the lander cabin at a slightly higher pressure than the outside as you'd suggested before should stop most unwanted influx.

Here's another issue: How will they generate electricity? Solar cells are out, obviously. Would a whole bunch of RTGs do the trick, or would they need a somewhat larger nuclear power plant? (Of course, by the time we're actually able to do this we may well have compact fusion power sources...here's hoping! tongue.gif )

Come to that, would it be worthwhile to haul in a bunch of oxygen & run fuel cells? Are there some easy ways to liberate H2 from Titan's surface compounds? Or, would it be simpler to "burn" some of the simpler CH compounds as conventional fuels using our oxygen cache?

Posted by: JonClarke Oct 23 2006, 12:21 AM

QUOTE (nprev @ Oct 22 2006, 10:56 PM) *
I have no idea how efficiently Titanian air could be scrubbed from an airlock, nor how long it would take. However, if pressure turns out not to be too big an issue physiologically, then keeping the lander cabin at a slightly higher pressure than the outside as you'd suggested before should stop most unwanted influx.


I have done some reading on particulate removal, which can be very fast and efficient, but don't know much about organic gases, which is why I asked. It would be interesting to find out how much pressure differential is required. Labs and factories that use hazardous materials run an\t lower pressures than the outside world, warships and some military vehicles operating under NBC conditions have higher internal presures to keep nasties in and out respectivively, this could serve as a guide for what would be required on Titan.

QUOTE (nprev @ Oct 22 2006, 10:56 PM) *
Here's another issue: How will they generate electricity? Solar cells are out, obviously. Would a whole bunch of RTGs do the trick, or would they need a somewhat larger nuclear power plant? (Of course, by the time we're actually able to do this we may well have compact fusion power sources...here's hoping! tongue.gif )


RTGs probably don't deliver enough power for a crewed mission. Failing compact fusion I think a fission reactor is the best option, at least initially. The high atmospheric density makes it easier to dispose of waste heat from a reactor on Titan than on the Moon or Mars, rather than relying on passive radiators (remember for every kW of electricity a reactor typically generates about 10 kW of waste heat), cooling fans would greatly increase the effectiveness of convection in dumping heat. Heat pads or rods into the ground would be another option, but you would not want to over do it.

For a permanant station, a wind farm might be an attractive supplement, given the low gravity, high atmospheric density, and presence of locally strong winds (there are lots of dunes on Titan). Titan has an internal heat source so geothermal (titanothermal?) power is another alternative.

QUOTE (nprev @ Oct 22 2006, 10:56 PM) *
Come to that, would it be worthwhile to haul in a bunch of oxygen & run fuel cells? Are there some easy ways to liberate H2 from Titan's surface compounds? Or, would it be simpler to "burn" some of the simpler CH compounds as conventional fuels using our oxygen cache?


Well the rocks appear to be water ice and ice clathrates, so with the waste heat you could melt the ice and electrolyse the water to oxygen. Methane and hydrogen could be recovered if needed, or simply dumped. The amount of methane in the Titanian atmosphere will support combusition with the addition of sufficient oxygen. So you could simply run reverse combustion engine, drawing ambient atmosphere into a combustion chamber, injecting oxygen, and igniting the mixture for example with a diesel engine or gas turbine. This makes long range ground vehicles and aircraft a much easier proposition than on Mars, for example. Methane and oxygen would be an ideal propellant combination for ascent and descent vehicles, although again, with sufficient plant and abundant atmospheric nitrogen, methane and a source of oxygen you could also manufacture storable hypergolics like hydrazine and nitrogen tetroxide, if you needed to.

Jon

Posted by: RNeuhaus Oct 23 2006, 03:13 AM

How will the astronauts will be able to talk to their familiars, relatives, friends and lovers since the Earth and Saturn are separated by a varying distance between 1,411,725,400 km to 1,576,725,400 km (the communications signal will take between 78 to 87 minutes depending to the orbital Saturn and Earth position around the Sun).

It is possible to overcome the distorsion of telecomunications. How?

Rodolfo

Posted by: ugordan Oct 23 2006, 07:02 AM

Easily. They will not talk. They will send messages.

Posted by: nprev Oct 23 2006, 07:41 AM

Yeah, on pretty much any body but the Moon real-time comm with Earth just ain't happening...unless you got a really good tachyon receiver/transmitter... laugh.gif

JC's comments were quite interesting. Sounds as if the expedition could harness indigenous resources rather easily if suitably equipped. This may prove attractive to commercial interests as well (al a Clarke's Imperial Earth). I'm sure that once the Moon and Mars are colonized Titan & Saturn's rings (and a nod here to Asimov's The Martian Way) will become the Solar System's Saudi Arabia for volatiles.

Posted by: nprev Nov 24 2007, 08:08 AM

Reviving this thread just because it's interesting, and also for a question to anyone with hazmat experience: How do you scrub dangerous heavy organics out of an airlock, or off of spacesuits?

I suspect that Titan may have some of these; in fact, it may have some compounds we've never encountered before. Would any Titanian EVAs require, say, a wash-down of the suits with acetone plus some sort of purge procedure before the astronauts would be safe to re-enter the lander?

Sounds extreme, I know, but there well might be some very potent organic poisons in the Titanian environment; never too early to think about countermeasures.

Posted by: djellison Nov 24 2007, 09:54 AM

Look up how much effort they took to make sure there was no NH3 on the spacesuits after recent ISS spacewalks involved in cooling loops smile.gif

Doug

Posted by: Juramike Nov 24 2007, 02:45 PM

QUOTE (nprev @ Nov 24 2007, 03:08 AM) *
Reviving this thread just because it's interesting, and also for a question to anyone with hazmat experience: How do you scrub dangerous heavy organics out of an airlock, or off of spacesuits?



Actually, this is a pretty easy.

The bulk of Titan's atmosphere is nitrogen. It would be straightforward to set up a condensation/refining unit that could make and store pure liquid nitrogen directly from the atmosphere. (Heck, you are almost at the liquid temperature anyway). That would give you a useful supply of nitrogen for flushing and for atmosphere reconstitution.

Once inside the airlock, a flush of warm (298 K) nitrogen will bring everything up to "normal" temperature, and volatilize most of the organics. A few evacuation/purge cycles with nitrogen should flush out most of the volatile yukkies. Then a simple scrub down of the suits with common decontamination solvents (fancy soaps and detergents) (at this point you could also use water), a last evac/purge cycle with fresh nitrogen, and you should be good.

The evacuation procedures could be replaced with extensive nitrogen atmosphere changes or multiple airlocks, or simple door chambers, each with a higher positive pressure to maintain atmospheric integrity.

Future colonists would have to live at a slightly elevated pressure inside their living environment (slightly above 1.5 Atm) to ensure that any breaches have a positive pressure going from "good" environment to "contaminated" enviroment. (Most GMP labs maintain their environment by having a slight positive pressure). [On Earth's surface, the pressure goes up 1 atmosphere for every 33 feet of water on Earth, so simply snorkeling gets you exposed to Titan's pressure!]

Inside the living environment, organic contaminants can be filtered from the atmosphere using a wide variety of filters that have been developed. Go to any hardware store and you can see NIOSH filters that will remove acidic, basic, or neutral volatile organics for respirators. Activated charcoal is the best for removing most volatile organic compounds (VOC's). There are also commercial analyzers that can be used to monitor the atmosphere for buildup of any organics.

The only energy intensive part will be keeping and maintaining the oxygen part of the atmosphere. That will have to be recycled and/or generated from electrolysis of water ice.

All of the precautions used for high VOC environments on Earth (e.g. paint sheds), could be easily incorporated for future living spaces on Titan. The harder problem will be insulating from the extreme cold.

-Mike

Posted by: nprev Nov 24 2007, 03:21 PM

Great, interesting thoughts as per usual, Mike! smile.gif Demanding procedures to be sure, but clearly practical.

Is the cold really that big a problem, though? I was thinking that the habitable enclosure(s) could be built like giant Dewar vessels with a vacuum layer between the inner & outer shells.

In fact, this paradoxically might require a cooling mechanism to keep the interior okay, which might provide a serendipitous benefit. I see a series of "heat pipes" (thick copper cables?) from the interior vessel out to the surface, where they're hooked to ice melting/water capturing devices...waste heat doesn't need to be wasted...

Posted by: Reckless Nov 24 2007, 03:45 PM

Realising that Titan's atmosphere is 98% plus nitrogen, will oxygen released by any habitat be able to ignite some of the methane (drizzle) or to put it another way are there any sources of ignition that might cause the oxygen to burn?

Roy F

Posted by: nprev Nov 24 2007, 04:35 PM

Only thing I can think of would be an electrical problem like a broken wire touching the superstructure, arcing & sparking. However, there are likely to be many such interfaces, so the problem becomes keeping the internal atmosphere isolated from the external interfaces; not particularly easy.

The good news is that if the habitat has positive pressure as Mike suggested then you basically get a jet of flame shooting outwards at the joint; no interior fire. Bad news is that this could still cause one hell of a lot of damage, and might be difficult to extinguish.

Posted by: ngunn Nov 24 2007, 05:07 PM

Combustion is not my field but I'd be surprised if 2%, or even the saturation level of 5% or so methane would be a sufficient concentration to support combustion with oxygen, especially starting from cryogenic temperatures. Assuming the Titan base used a normal terrestrial oxygen/nitrogen mixture the risk would be even less. Cold nitrogen is a pretty good fire extinguisher. However you wouldn't want your oxygen tanks to be struck by lightning during one of those once per millennium downpours!!!

Posted by: nprev Nov 24 2007, 06:46 PM

Ah. Then we need to just ground the hell out of the place.... smile.gif

Posted by: Reckless Nov 24 2007, 08:04 PM

Thanks for the replys all. I feel a lot safer now about going outside to look at one of these methane/ethane lakes. And the nice slow moving waves smile.gif

Roy

Posted by: Juramike Nov 24 2007, 09:18 PM

QUOTE (ngunn @ Nov 24 2007, 12:07 PM) *
Combustion is not my field but I'd be surprised if 2%, or even the saturation level of 5% or so methane would be a sufficient concentration to support combustion with oxygen, especially starting from cryogenic temperatures.


I'd be more concerned with higher hydrocarbons and other organic brought in by the astronauts. Some of that stuff might melt as it gets warmer and could support combustion inside the living module. For example, hexane (solid at Titan's temperatures) might get tracked in on the astronauts boots or clothing, and it will volatilize and support combustion quite nicely in a 20% O2/N2 environment. (Diethyl ether would be even more impressive)

-Mike

Posted by: nprev Nov 24 2007, 11:23 PM

Eek. So, outside-only booties & gloves stowed in the outermost airlock might be a very good idea, then? (Don't know what to do if anybody fell down outside & got this stuff on their suit, though...maybe an entire overgarment is the answer?)

EDIT: Got it! One stage of the ingress process should be pure N2 @ 300K to evaporate all this crap over a suitable (ta-da, da!) interval, then purge it out...afterwards, normal re-entry.

EDIT2: The process of going back inside is going to be a LOT like standard military chemical warfare decontamination procedures; gee, what fun. sad.gif

Posted by: tty Nov 25 2007, 08:52 PM

20 % O2 would seem excessive (and probably unhealthy) at 1,6+ atmospheres. 10 % should be enough for breathing as well as decreasing fire risks and the quantity of oxygen needed.

As for leaks from an overpressure habitat it seems likely to me that small leaks might well be self-sealing since the water and the CO2 in the interior atmosphere would freeze instantly at Titanian temperatures.

Posted by: nprev Nov 25 2007, 11:45 PM

Hey, that's a great point about self-sealing leaks, tty! Guess that periodic inspections/maintenance would catch these so the crew could spackle them over.

Hot wiring faults to the outside are still worrisome, though. Might be best to have all that stuff completely outside the main habitat with its own power supply and an RF link to the inside, and THAT thing would have to have some serious ground-fault interrupt protection.

Posted by: Juramike Nov 26 2007, 12:29 AM

Hydrocarbon solvents have a very low electical conductivity. Flowing hydrocarbon solvents (like methane, I suppose, but more OSHA data exists for hexanes) tend to build up static charges.

I wonder if a methane rain event on the outside of the habitat would build really impressive levels of static charge? In the "natural" environment, I also wonder if methane flowing along a Titan river stream might also build up an impressive static load.


"Solvents and fuels produced from petroleum (e.g., benzene, toluene, mineral spirits, gasoline, jet fuel) can build up a charge when they are poured or flow through hoses. They tend to hold a charge because they cannot conduct electricity well enough to discharge when in contact with a conducting material, like a metal pipe or container, that is grounded. When enough of a charge is built up, a spark may result. If the vapour concentration of the liquid in air is in the "flammable range" and the spark has enough energy, a fire or explosion can result."

Source: http://www.ccohs.ca/oshanswers/prevention/flammable_static.html

Since there is no oxygen in Titan's atmosphere, fire or explosion is not an option. But could "ground lightning" or spark discharges occur in the flowing streams?

-Mike




Posted by: nprev Nov 26 2007, 01:02 AM

Think that would depend on the composition of the surrounding terrain, which is probably water ice with a lot of organic impurities (my guess is that on Titan H2O takes the role of SiO2 on Earth). Liquid water on Earth is significantly conductive only when it has dissolved salts or metallic ions, IIRC; don't know about ice. If the channels are carved out of good insulators, though, there well might be a good-sized charge in the fluid (and maybe also the atmosphere itself at times?)

Scary thought, though; in addition to grounding the hell out of the habitat, surface explorers may well have to have conductive suits with grounding straps dragging on the "soil" to avoid being zapped! (I have a mental image of spacesuits with dragging tails, but it's almost too stupid-looking to bear...beats blowing up, or frying the suit electronics, or even being electrocuted, though.)

Anyone else getting surprised at how un-easy surface exploration of Titan may turn out to be? That nice, thick atmosphere seems to have led to a false sense of security... unsure.gif

Posted by: dvandorn Nov 26 2007, 05:38 AM

All in all, though, Nick, Titan offers more of the raw materials humans would need to create a self-sustaining colony than just about any other body in the Solar System (except for Earth).

There are all the elements we need to survive -- specifically, carbon, hydrogen, oxygen and nitrogen -- in great abundance. The only thing in short supply is a good power source. Yes, if you crack enough oxygen from the water ice you'd be able to burn a lot of the hydrocarbons, but that burning would generate less energy than what you'd need to crack that much oxygen out, I fear.

The one thing we'd need to import from Earth is a good energy source to make Titan a good place for human habitation. Unfortunately, the only thing I can think of that would work well there would be nuclear energy, and you don't want to have to transport megatons of fissile materials all the way out to Saturn! (You think you have issues with the anti-nuke crowd *now*...)

-the other Doug

Posted by: tty Nov 26 2007, 07:16 AM

QUOTE (dvandorn @ Nov 26 2007, 06:38 AM) *
Yes, if you crack enough oxygen from the water ice you'd be able to burn a lot of the hydrocarbons, but that burning would generate less energy than what you'd need to crack that much oxygen out, I fear.


On the other hand heat engines should be very effective on Titan because of the very low ambient temperature. It will take some exotic engineering to make full use of heat engines where the cold end is at 90 K, but the end result might be spectacular. Think of a steam turbine, then you use the waste heat from the condenser to heat the habitat, then you use the waste heat from the habitat to run a carbon dioxide based stirling engine then you use the waste heat from that to run a methane based stirling engine....

QUOTE
Unfortunately, the only thing I can think of that would work well there would be nuclear energy, and you don't want to have to transport megatons of fissile materials all the way out to Saturn!


Why not? Uranium-based reactor fuel is almost completely harmless until it has been irradiated.

Posted by: dvandorn Nov 26 2007, 07:37 AM

QUOTE (dvandorn @ Nov 25 2007, 11:38 PM) *
...you don't want to have to transport megatons of fissile materials all the way out to Saturn!

QUOTE (tty @ Nov 26 2007, 01:16 AM) *
Why not? Uranium-based reactor fuel is almost completely harmless until it has been irradiated.

I was actually thinking about the extremely high mass of fissile materials. Takes a lot more energy to send a cubic mile of uranium to Saturn than sending a cubic mile of, say, lithium batteries.

-the other Doug

Posted by: djellison Nov 26 2007, 08:34 AM

QUOTE (dvandorn @ Nov 26 2007, 07:37 AM) *
Takes a lot more energy to send a cubic mile of uranium to Saturn than sending a cubic mile of, say, lithium batteries.


You're not looking at that the right way. How much energy does it take to send, say, 1 MWhr of energy in the form of Uranium. Now how much energy does it take to send 1 MWhr of energy in the form of Li cells? You are assuming 1 kg of battery provides the same amount of energy as 1 kg of Uranium.

Doug

Posted by: dvandorn Nov 26 2007, 08:43 AM

Oh, I understand -- uranium has a higher potential energy density than a lithium battery. I'm just thinking in terms of logistics. Any plan that requires bringing along enough fissile materials to support a manned base is going to be harder to accomplish (in terms of just getting everything to Titan and setting it up) than a plan that can actually draw enough power for its operations from indigenous sources.

Titan is just so energy-poor... you'd need to cover hundreds of square kilometers of landscape with solar cells to get anything useful at that distance from the Sun and through that thick haze. And you just can't extract heat out of a system that doesn't have any...

-the other Doug

Posted by: djellison Nov 26 2007, 09:08 AM

QUOTE (dvandorn @ Nov 26 2007, 08:43 AM) *
Any plan that requires bringing along enough fissile materials to support a manned base is going to be harder to accomplish (in terms of just getting everything to Titan and setting it up) than a plan that can actually draw enough power for its operations from indigenous sources.


Not really, no. It's entirely dependent on the mass of a small reactor compared to the mass of whatever equipment and resources you bring along to use 'indigenous' sources (such as taking O2 to burn local material) I would also have thought the former would be simpler and more reliable. That one would be heavier than another is not certain.
Doug

Posted by: ngunn Nov 26 2007, 09:49 AM

Has anyone mentioned 'hydro'power? All you need is a lake on a hilltop - or one with tides. There could be 'geo'thermal possibilities too, and wind power.

Posted by: nprev Nov 26 2007, 12:00 PM

QUOTE (dvandorn @ Nov 25 2007, 09:38 PM) *
All in all, though, Nick, Titan offers more of the raw materials humans would need to create a self-sustaining colony than just about any other body in the Solar System (except for Earth).

-the other Doug


Oh, I completely agree; think Clarke got it exactly right in Imperial Earth...Titan will someday be the equivalent of Saudi Arabia just because most of the rest of the Solar System is so volatile-poor and because it's cheap in terms of energy to lift the materials off.

The energy generation problem is thorny, though, and I don't see any practical alternatives at all to fission reactors at this point. Hopefully by the time we get there to stay--thinking about 200 years from now--we'll have solved the fusion power problem in a cheap and highly portable fashion; no worries then! smile.gif

EDIT: Doug's comment about importing O2 got me thinking. Maybe all we really need is a "seed" energy source, and by this I mean something to establish an initial energy generation process that's used to fire off another process using indigenious resources which in turn becomes self-sustaining...sort of like striking a match. (Sorry for the generality.)

Posted by: Juramike Nov 26 2007, 12:52 PM

Nigel nailed it! There are lots of really good energy sources on Titan:

Wind - wind speeds low but fairly steady, but atmosphere is thicker than on Earth. And dunes give a great indicator of funneling of winds from topographical features. (Double Bonus, we can use dune features visible NOW to select best places for wind farms!)

"Hydro" - If any of the polar streams are flowing at rates even close to those predicted by dimension, there's a massive potential for methane fluid flow.

Geothermal - Findind a fairly recent crater could allow you to trap residual heat from liquid water-ammonia. Also, there might be circulating fluids down deep (molten water-ammonia? molten organics?). Water has good heat capacity due to it's phase change energy. (It releases lots of heat on crystallization)

Chemical - There may be natural organic ore bodies that could be useful for energy production. For example (and I'm speaking off the top of my head - someone would need to look at the energies to see if it would be useful), a deposit of pyridinium N-oxides might be equivalent of a fuel deposit on Earth. (Pyridinium N-oxide could be used as an oxidant). There could be other potential reactant bodies lying around (or easily mined) that are prevented from reacting due to kinetic barriers from normal Titan conditions. Add a catalyst, or enough heat to overcome the barrier, and bingo, you've got an energy source. (Maybe not as impressive as fire, but any exothermic reaction helps!)

Finally, what are then energies involved in splitting water, taking the oxygen, then burning hydrocarbon? (This might be "carbon neutral" on Titan - since you are swapping one IR absorber for another)

What are the energies for:

H2O --> H2 + O2 [uphill]
O2 + CH4 --> CO2 + H2O [downhill]
H2 + C2H4 (or C2H4) + cat --> C2H6 [downhill]


Titan has oodles of potential energy sources. We've got evidence of wind (Huygens drift and dunes), evidence for permanently flowing liquids is tanalizingly close, and exploitable chemical and geothermal sources will require more research and examination. (So surface exploration serves two roles: science and energy prospecting).

-Mike

Posted by: djellison Nov 26 2007, 01:41 PM

I assume this is all 500 years-from-now-Titan-colony type speculation. Any first visit or indeed, first 'round' of visits - I wouldn't rely on ANYTHING other than that which I could take with me.

Doug

Posted by: ngunn Nov 26 2007, 02:03 PM

QUOTE (djellison @ Nov 26 2007, 01:41 PM) *
I wouldn't rely on ANYTHING other than that which I could take with me.


Why? Robots would already have constructed the habitation, the windfarm and the geothermal station - and the kettle would be on for tea. smile.gif

Posted by: tasp Nov 26 2007, 03:08 PM

'Tracking in' materials from outside might be complicated by some of the materials possibly formed outdoors not being particularly volatile below 0 C. Kerogen (or precursors) have been tenatively ID'd on asteroids, and might occur on Titan too. Polymerized Titanian 'gunk' might have to be carefully scrutinized by Huygen successors to assess the dangers. Additionally, our earthian environment is characterized by a polar solvent, water, and we are most skilled and experienced with that. Titan seems to have a 'hydrological' cycle driven by a non-polar fluid, and probe design will be challenging in regards to material properties and chemical effects.

Posted by: Juramike Nov 26 2007, 03:47 PM

QUOTE (tasp @ Nov 26 2007, 10:08 AM) *
Titan seems to have a 'hydrological' cycle driven by a non-polar fluid, and probe design will be challenging in regards to material properties and chemical effects.


Material properties and challenges of exploring a hydrocarbon environment have been done on Earth. There is a huge amount of experience designing probes for gas pipelines and hazardous chemical reactors that could be used. I don't think there are any chemical conditions that could exist on Titan that haven't already been dealt with somewhere in a chemical manufacturing process, save for the extreme cold.

Check out "pigging" of pipelines: http://en.wikipedia.org/wiki/Pigging
[EDIT: Could this be Doug's Next Big Robotic Project? wink.gif ]

The basic amines that might be present would be a slight chemical challenge to some plastics and polymers due to their corrosive nature (gum rubber would be a bad idea). But Titan is in an overall reducing environment, so the rust and oxidation of metal components won't be a problem.

-Mike

Posted by: dvandorn Nov 27 2007, 05:53 AM

What still concerns me about any operations on Titan (manned or unmanned) is the rather phenomenal temperature difference at which terrestrial machines and organisms (i.e., us) can operate versus Titan's natural environment.

Any terrestrial outpost or machinery is going to add *significant* amounts of heat to the Titanian environment. If ever there was a situation where observing a phenomenon affects that phenomenon, this is it.

We may have to figure out how to develop robots that can operate entirely at Titanian temperatures before we set out to study the place at close range, because the heat our current technology would be pumping into the local materials will change them in innumerable ways, and we won't see them as they've developed in situ.

-the other Doug

Posted by: ngunn Nov 27 2007, 09:34 AM

QUOTE (dvandorn @ Nov 27 2007, 05:53 AM) *
We may have to figure out how to develop robots that can operate entirely at Titanian temperatures before we set out to study the place at close range


Exactly. But in fact Titan conditions could be quite benign for machines. Certainly there's no problem with electronics working at those temperatures (superconducting materials available), and a nitrogen atmosphere should be an advantage over a vacuum as far as moving parts are concerned. I haven't yet heard mention of anything mooted in Titan's surface chemistry that would attack metals. There could be a problem finding an insulating material that is flexible rather than brittle at those temperatures for cable sheathing, etc., but those chemists are very resourceful. (Give Juramike 20 minutes. smile.gif )

The serious point behind my last post is that I don't ever envisage a manned visit in gung-ho Apollo style with people climbing down a ladder to the surface and bouncing around in boots. I think the first human visitors will arrive at a fully operational base station (not just VERY well insulated but with active heat pumping like an inside-out fridge) complete with rooftop docking system; a rover bay would be added later. Their main task will be to service and upgrade the robots.

Posted by: Juramike Nov 27 2007, 01:30 PM

The cold is going to be THE big problem facing probes, machines, and colonists on Titan. Compared to other moons, Titan's atmosphere is thick, cold, and windy. So there will more heat conducted away from warm objects on Titan compared to other moons where objects will be partially be isolated by vacuum.

[Compare keeping hot coffee in a Thermos to trying to keep a hot cup of coffee in a pan of cold water.]

A heavy methane rain would also do a really great job of sucking heat away from warm stuff on the surface as well, both from conductivity from the moving fluid but also from the instant evaporation of the methane rain drops when it hits the warm surface. Just like the first raindrops from a summer thunderstorm disappear when they hit a warm sidewalk here on Earth.

But think of the fun the colonists will have shattering roses, driving nails with bananas, and other fun low-temperature experiments.

-Mike

Posted by: nprev Nov 28 2007, 01:08 AM

Odd how the analogies between Venus & Titan keep cropping up, even though sometimes 180 deg out of phase from one another. Dewar-type vessels have also been proposed for Venusian probes.

Posted by: Stephen Nov 28 2007, 07:13 AM

QUOTE (ugordan @ Oct 21 2006, 12:28 AM) *
I find it compelling that you could go around on Titan, pick up "rocks" you find interesting and when you get back to the ship, all those rocks just melt away under earthly temperatures. There's something about the fact that entire mountains, everything you see there would just melt if you held it in your hands long enough. Provided you had big enough hands... biggrin.gif

Correct me if I'm mistaken but it isn't Titan's surface composed of at least some proportion of ices? Meaning compounds which are liquid or gas at normal earthly temperatures. That raises the question of what would happen to that Titanian surface if it were subjected to earthly temperatures, especially over a prolonged period.

Wouldn't those ices soften, and eventually melt or subliminate?

If so wouldn't that lead (eventually) to objects (like landers, rovers, nuclear reactor modules) getting bogged in the Titanian surface, or even (given enough time) sinking into that surface in a more substantial fashion, whether in a more or less graceful way (albeit no doubt with various degrees of tilting) or via periodic subsidences (as the earthly temperatures caused the ices component to leach away from the silicate stuff, gradually undermining the integrity and load-bearing capacity of the Titanian surface).

=====
Stephen

Posted by: edstrick Nov 28 2007, 09:25 AM

Some of the surface materials may DETONATE on being warmed.
Take (I think) cryogenic nitrogen and methane ices mixed, irradiate with charged particles.... it turns yellow, and DETONATES on being warmed toward sublimation temperatures.

Posted by: ngunn Nov 28 2007, 09:44 AM

QUOTE (edstrick @ Nov 28 2007, 09:25 AM) *
Some of the surface materials may DETONATE on being warmed.


Does this require the presence of oxygen? If not, there could be some alarming things happening in cryovolcanic areas.

Posted by: Juramike Nov 28 2007, 09:15 PM

QUOTE (edstrick @ Nov 28 2007, 04:25 AM) *
Some of the surface materials may DETONATE on being warmed.
Take (I think) cryogenic nitrogen and methane ices mixed, irradiate with charged particles.... it turns yellow, and DETONATES on being warmed toward sublimation temperatures.



Do you have a reference for this? I poked around a little and couldn't find anything.

But it might be possible: Some possible culprits would be diazomethane (CH2N2) and even more hazardous cousins diazidomethane and triazidomethane (HC[N3]2). Diazomethane is yellowish and explodes when it crystallizes. (Chemists playing with this stuff had to use new joint-free glassware free from any surface defects. These days trimethylsilyl azide is a much safer alternative in recipes). The azidomethanes are exceptionally nastybad compounds that detonate at greater than 70% concentration. Many laboratory accidents occur when azidomethanes are accidentally generated. (I assume triazidomethane blows back to formamidine and 3 molecules of rapidly expanding nitrogen gas).

One described example: http://pubs.acs.org/cen/safety/19930419.html

All these detonations would NOT require the presence of oxygen.

(Azides are famously shock-sensitive. Sodium azide is used to make airbags inflate rapidly during collisions. Metal azides are even worse. IF (and it's a big if) light organic azides could be generated on Titan, these could be a bad thing.)

-Mike

Posted by: nprev Nov 29 2007, 01:04 AM

Good grief... blink.gif !!! Are you saying that there may be natural minefields on Titan? Do these compounds have an affinity for each other, or do they tend to disperse? (By that I mean in the "wild" state instead of under laboratory conditions, if the possible circumstances for natural formation are at all understood; assuming it doesn't happen naturally on Earth.)

Posted by: Juramike Nov 29 2007, 12:42 PM

QUOTE (nprev @ Nov 28 2007, 08:04 PM) *
Good grief... blink.gif !!! Are you saying that there may be natural minefields on Titan? Do these compounds have an affinity for each other, or do they tend to disperse? (By that I mean in the "wild" state instead of under laboratory conditions, if the possible circumstances for natural formation are at all understood; assuming it doesn't happen naturally on Earth.)



IF azides can form on Titan. (I'm not sure if azides can form through photochemical or atmospheric means.) (It is comforting to note that Huygens didn't get blown up when it landed.)


Like anything else, concentration could occur through solvents reworking the surface or crust and concentrating compounds in ore deposits. Differential solubilities could cause selective deposition as sparingly soluble species ploop out of solution.

("If your are not part of the solution, you are part of the precipitate.")

-Mike

Posted by: djellison Nov 29 2007, 12:51 PM

QUOTE (Juramike @ Nov 29 2007, 12:42 PM) *
("If your are not part of the solution, you are part of the precipitate.")


That's GENIUS.

Doug

Posted by: Juramike Nov 29 2007, 03:54 PM

QUOTE (djellison @ Nov 29 2007, 07:51 AM) *
That's GENIUS.

Doug


(I can't take credit for it)

(But you can buy the T-shirt: http://www.redmolotov.com/catalogue/design.php?design_code=solutionprecipitate)

Posted by: Shaka Nov 29 2007, 07:04 PM

QUOTE (Juramike @ Nov 29 2007, 02:42 AM) *
(It is comforting to note that Huygens didn't get blown up when it landed.)

-Mike

Are you sure we know how many times it landed?
cool.gif

Posted by: nprev Nov 30 2007, 07:51 AM

QUOTE (Shaka @ Nov 29 2007, 11:04 AM) *
Are you sure we know how many times it landed?
cool.gif


laugh.gif ...we'd have to rename it the "Wile E. Coyote Memorial Station"...

Posted by: edstrick Nov 30 2007, 11:45 AM

"Do you have a reference for this? I poked around a little and couldn't find anything...."

This was being presented back in the late 80's at Lunar and Planetary Science Conferrences, post Voyager-2 at Triton. Results may/probably-are also in DPS and AGU Spring/Fall meeting abstracts.

re: "Wile E. Coyote Memorial Station"
ROTFLMAO.

Posted by: nprev Dec 1 2007, 10:10 AM

smile.gif ...thank you, Ed, but all credit to Shaka for that mental image!

Damn interesting, though. We've been thinking of organics as essentially inert, but quite obviously they're not else life on Earth wouldn't have happened in the first place. Titan's chemosynthetic history & capabilities are unknown, and it will probably take several generations of surface probes to shed enough light to enable manned exploration...

Posted by: rlorenz Dec 1 2007, 03:00 PM

Re: stuff blowing up on Titan

QUOTE (Juramike @ Nov 28 2007, 04:15 PM) *
Do you have a reference for this? I poked around a little and couldn't find anything.

But it might be possible: Some possible culprits would be diazomethane (CH2N2) and even more hazardous cousins diazidomethane and triazidomethane (HC[N3]2).
.....


Solid acetylene (C2H2) can polymerize explosively. Some wag in the early 1990s suggested that
Huygens' landing might set the whole planet off

But of course, meteorite impacts or shockwaves from tunguska-like breakups etc. would do that
on a regular basis anyway, so the accumulation of explosives will not be large

Posted by: nprev Dec 1 2007, 03:45 PM

Well, assuming for the moment that we're not likely to hop across the surface from multiple "land-mine" encounters, how would a large manned vehicle (LM-class or better) execute EDL? Seems easier at first glance than landing on Mars because of the thicker atmosphere & lower gravity (and lower initial orbital velocity to shed).

Side note- "If you're not part of the solution, you're part of the precipitate"...comedian Steven Wright, no? That guy is absolutely brilliant.

Posted by: David Dec 2 2007, 02:36 AM

QUOTE (nprev @ Dec 1 2007, 03:45 PM) *
Well, assuming for the moment that we're not likely to hop across the surface from multiple "land-mine" encounters, how would a large manned vehicle (LM-class or better) execute EDL? Seems easier at first glance than landing on Mars because of the thicker atmosphere & lower gravity (and lower initial orbital velocity to shed).


There's always the possibility of splashdown!

Posted by: nprev Dec 2 2007, 05:57 AM

QUOTE (David @ Dec 1 2007, 06:36 PM) *
There's always the possibility of splashdown!


True, given accurate targeting...but then what?

I'd hate to have to design an auxiliary propulsion system to get the damn thing near the shore (remember, we're talking a manned vehicle here), to say nothing of disembarcation...lots of complexities here.

Posted by: dvandorn Dec 2 2007, 08:35 AM

How effectively, given current materials technology, can we insulate the "ground" where we would locate a Titanian habitat from the heat within the hab?

Seems to me we're going to have to limit heat leakage from the hab *very* selectively, or else the "ground" (or at least some of it) will become liquid where in direct contact... thereby alleviating your worries, Nick. No matter what we do, she'll eventually end up afloat, regardless!

smile.gif

-the other Doug

Posted by: David Dec 2 2007, 05:19 PM

QUOTE (nprev @ Dec 2 2007, 05:57 AM) *
True, given accurate targeting...but then what?

I'd hate to have to design an auxiliary propulsion system to get the damn thing near the shore


Oh, I can think of a reasonably simple and deployable auxiliary propulsion system -- it would consist of a thin, tough, cold-resistant fabric stretched between two or more spars...

Posted by: nprev Dec 2 2007, 07:04 PM

Ahrrr...har, har, har, David! tongue.gif Yeah, I'm thinkin' that playing mast monkey in a spacesuit even at 0.25G might not be the safest way to go...(although I hear the Navy guys from another thread cheering in the background)...

oDoug, that's a scary thought. Only thing that could be done is, assuming that the habitat/lander is basically a Dewar flask, limiting the internal vessel physical interfaces to & beyond the outer shell so that heat conduction is controllable: I'd use some thick, heavily insulated copper cabling (unless an advanced superconductor is available 200 years from now when all this might happen) attached near each interface point about 100m long, and stick the business end into the "soil" that far out...let it melt over there, not near the habitat. Notice also that this most effectively provides electrical grounding for the lander.

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