We'll explore Titan with a methane submarine, a methane submarine, a methane submarine... Titan’s largest sea of liquid is estimated to be over 1,000 feet deep, judging from new radar analysis, making it an ideal location for a future autonomous robotic submarine to explore. Saturn's moon Titan, and our home world Earth, are the only two bodies in the Solar System known to have stable liquid on their surfaces. …
"strong currents and tides could help the vehicle navigate underwater."
For values of navigate that include tossed about like the bit of jetsum it will become. One wonders if it will ever be declared derelict, and will anyone try to recover it out from under NASA based on the old sine spe recuperandi or sine animo revertendi clauses of maritime law.
That was my first thought as well. I assume the intent is that strong tides and currents will make it easy to move around to many different locations without needing to use much of its own power, which has obvious benefits given the weight and power limitation for spacecraft. "Navigate" has implications of actually being able to choose where it goes, which seems less likely to be the case.
On a different note, although krakens are often depicted as giant squid or octopus-like things, that's not actually how they were originally described. They were either basically just something so big that it seemed to be a bit of land, but with a mouth that could swallow a bunch of stuff when it opened, or sometimes explicitly described as a really big whale. All the talk about tentacles and speculation that the stories were inspired by giant squid are based on much later variations; the original stories seem be fairly obvious cases of people taking something they're familiar with - whales - and making up tales about really big ones.
> to move around to many different locations
Assuming it is not stranded (or even broken up) on some reef... Letting currents and tides move you around is always quite risky.
On the other hand, real "navigating" will be mostly impossible since we lack any precise information about the location. It is the same situation ancient explorers faced, except there will be nobody up the crows nest to see the telltale wave patterns of hidden reefs, or detect the oncoming storm... And programming an AI to do that will be hard since we've very little experience with methane ocean features.
And I don't even mention the presence of the kraken which gave that sea its name... :-D
Heat is a big issue here.
I think the motion via tides & currents may be due to the relative energy level that will be needed to operate the craft and its equipment. The temperatures mentioned (-179.6°C, -292°F, 93.6K) allow about a 20° surface temperature rise before boiling the methane becomes a bouyancy issue*.
It could be that running a useful motor and it's power source (RTG basically) requires the craft to maintain a minimum speed to avoid sinking.
*The sub will fall in any gaseous methane filled gap below it (however small) and slowly 'sink' because it is in a gas bubble even if it has positive bouyancy compared to the liquid surrounding the bubble.
Well that's altitude control solved. Heat to the bottom: melt your way lower. Heat to the top: melt your way higher. Normal running means tacking up and down.
It probably works in the horizontal plane, too. Heat to the front: melt your way forwards. Etc...
I haven't thought about any pressure issues.
Yes, the smallest gap between ambient temp and the HC boiling point should be at the surface, If the sub never has to surface1 the designers could work on a larger heat budget. But we don't know the actual temperature gradient as depth increases so there's also the possibility that the sea is slightly warmer at depth for whatever reason and gap actually narrows2.
There is the possibility that the first subs entire mission is a one way dive calling out temp & density as it plummets, that alone would be a major achievement in data gathering and pretty much guarantee sub#2 has a good operational envelope.
Basically the engineering for this first sub will be a best educated guess dive into the unknown based on distant observations and fly-bys as all first of type probes have been (This one is likely to be the first into liquid).
1I'm guessing at a tethered buoy with radio relay equipment for data transfer.
2Accurate calculations can't be made without detailed information about actual temperatures & densities, they're something the sub itself will need to collect.
My first though was about lubrication for bearings, etc. But the issue of a power source is a serious one as even with batteries able to charge/discharge at -179C you need ways to top them up. Solar panels will provide SFA at that sort of distance, so unless you can somehow work a fuel cell to use the lake you are back at RTG supplies.
But as heat engines efficiency depends on the difference in absolute temperature, it might well be possible to use 100C-ish RTG and the lake's -179C to drive a Sterling engine for power and propulsion.
Oh I really wish I could work on that project!
The problem with a boat is that it will be subject to the winds and cross-currents. Underwater vehicles would only have to deal with currents. Oceanographers have quite a lot of experience with autonomous submarines:
https://noc.ac.uk/facilities/marine-autonomous-robotic-systems/autosubs
Although maybe there is a DoD interest in getting civilian funding for AI control systems:
https://thenextweb.com/neural/2020/03/10/the-us-navy-is-developing-ai-powered-submarines-that-could-kill-autonomously/
Watch this space!*
*Sorry, couldn't resist that.
"A boat can even have a sail for propulsion."
What sail material would you propose at that temperature? Sails undergo all kids of stresses that you don't see on a pretty news broadcast of San Francisco Bay or Sydney Harbour[0].
[0] Yes, I typed "Harbour", not "harbo(u)r" ... it's a proper noun, they can name it what they like.
Are you suggesting that Patrick Duffy is not from Earth after all then and that he landed on that beach from a great altitude? That makes sense. Perhaps he used his webbed hands and feet to punt himself across the vastness of space. After all it is a viable alternative to ION drives.
Seems to be going into this but to what end?
What are they possibly hoping to discover in a bath of liquid hydrocarbons at around 93K ? There are parts of Earth's seas and oceans that have never been explored due to the facts a. That it's difficult, and b. That your ability to sense your surroundings is severely hampered. If you are going to that by radar etc. Why not do it from the surface.
Frankly, a lot more useful science can be done 'in atmosphere'.
A nice headline but ....really...?
Same reason why we explore Titan at all - because its there. Sure, no one expects to find life so it isn't likely to potentially lead to a world changing discovery.
If we want to potentially find multicellular life in our solar system, probably the only possible candidates are liquid water oceans under ice in places like Europa, and methane clouds of the gas giants. Navigating Titan's seas might help us learn things that help either/both of those potential future missions.
' Because it's there' doesn't really cut it in a budget request or a research funding round though does it?
When you are competing with well considered science you need to offer a bit more than 'might' as a rationale.
If you want to research Europa's suspected ocean or a gas giants gas clouds, go there and do it.
I fail to see the value in diving into a cold hydrocarbon soup if your goal is to find signs of life in a water body or gas cloud.
Agreed, at that temperature any biochemistry is going to be glacially slow. As for using methane in place of water that doesn’t really work, it’s too reactive.
The water ocean on Europa is a much better bet for lifeforms. Deep down around the hydrothermal vents. No much more than bacteria though I wouldn’t think.
As for using methane in place of water that doesn’t really work, it’s too reactive.
I think you'll find that, at 93K, it's a whole lot less reactive. And, of course, it's only going to be reactive with something in another oxidation state, as far as I am aware, the atmosphere of Titan is chemically reduced. Methane doesn't react very readily with other hydrocarbon species where the oxidation state of the carbon is similarly negative (methane is -4, ethane is -3), you'd need something that can actually react with it, such as oxygen or a halogen for anything much to happen, otherwise you'd find that methane is actually pretty unreactive stuff.
Mmmm, take a look at the Woods Hole Oceanographic Institute's page on "Drifters and Floaters", https://www.whoi.edu/what-we-do/explore/instruments/instruments-floats-drifters.
Upshot: we already build autonomous mobile sondes and float 'em and drift 'em (with optional buoyancy control) in Earth's oceans. It could be that the final plans for the Titanic exploration (no relation!) will involve several small, lightweight, rugged drifters and floaters, so if one beaches itself the mission is not, well, on the beach.
This is a cool (sub zero) idea but I hope they are allowing for some variability in the science package after the results of the first lander are known since the article implies that this would be considered for a later mission. Pictures of a Titan smoker, if there are any, would nerd me out.
And since nobody's mentioned it, I'll ask. Doesn't the smell annoy Moray Sinus? I'll be here all week.
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