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Comment by safety1st | Hacker News Reader

Yeah I think a mission to see whether we can scoop up stuff that's been blasted up to the surface or even into orbit (and probably picking up some data on the ice crust along the way) is a lot more promising.

Just saying, there are people in these comments observing that "you can buy a 25km fiber cable online" lol... I love the exuberance but people may not be fully grokking the scope of the engineering problem here :) every mission comes at the expense of other possible missions, and drilling 25km down into Europa could easily be a feat that we would fail to accomplish even with 5 or 10 missions. There are challenges we will not surmount in our lifetimes, and this might be one of them. Deep drilling is dramatically harder than your average HN user probably realizes... exuberance alone cannot conquer physics.

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Well, what good is a naive misgiving if you don't even use it to haughtily dismiss genuine expertise? I can't tell you how many times I've had developers essentially manaplain my non-dev fields of expertise to me knowing that I was a credentialed professional and they were making stab-in-the-dark assumptions. Phrases like, "theoretically, it should be very simple," should usually be replaced by, "It would be ridiculous to assume everything I don't know about this is inconsequential, but here are some baselessly confident words about it:".

What good is a professional credential if you don't use it as an appeal to authority to shut down any criticism of your opinions? /s

On a more serious note, it's a travesty that lawyers get all the hate and PEs get none.

add to this the constant claims in the field of renewable energy and the energy transition. I've heard "energy storage is a solved problem" so many times that i cannot help but laugh.

Code & techbros are not the solution to everything.

Then, some will dust off that Larry Wall quote about hubris as if it's exculpatory... Well, I read that book too, and he was definitely talking about problem-solving approaches in software development, and not general-purpose personality traits for software developers.

You have to use more expensive radiation hardened fiber for Europa because the cheap stuff will literally go dark. It is likely there will also be a lower rate copper signaling path in case the umbilical tether is slightly damaged. Previous efforts to drill outside of Earth (mostly Mars) have proven difficult; there have been suggestions to instead "melt" through the ice with a radioisotope thermoelectric generator but this presents a different set of problems.

Rest assured that incredibly smart people at a propulsion laboratory are working on solving these sorts of problems. If you are a citizen of the USA, you can help by asking your elected representatives to adequately fund these efforts so these personnel won’t be laid off in the next few months.

If it truly is just ice it would likely be more effective to melt through and spool out power/comms behind it (think TOW missile) rather than drill through. Carrying spare energy is a less thorny problem than all the (literal) moving parts required to autonomously drill a few miles in the outer solar system.

That would be a lot of power required to prevent refreezing. If we're just throwing nonsensical ideas out, why not drop your probe down one of the geysers? Let the planet make the holes for you. You just need to make it so it doesn't get blown out each time the planet/moon sneezes. Of course, because I used the hand wavy word just means you automatically get to triple the cost estimate.

Would refreezing break the cable?

If you build the probe so that it has the spool of cable in it, then the probe has to be as large as the full load of cable. If you make the probe just big enough to do what it needs while pulling the cable from the lander then it can be much smaller. If using the smaller probe, then the cable will need to be fully movable as it melts deeper. The larger probe with the full length of cable will require much more energy as it needs to melt a much larger hole.

Where is all of this energy coming from?

> Where is all of this energy coming from?

A nuclear reactor, probably.

https://en.wikipedia.org/wiki/Radioisotope_heater_unit

Really? To heat and melt sufficient ice around 25km of cabling? I don't know what temperature this ice is at, I think on the surface Europa averages around -300F, so it's probably at least that low. I guess a lot is going to depend on whether you're fine with the ice refreezing around the cable - if the ice shifts at all, the cable breaks. Keeping the whole thing heated continuously seems implausible

that would surely mess with any organics you might want to find

No, not really. Water is very effective shielding, and you could melt a base station through the ice and do exploration with subs it sends out if you want fairly pristine samples. In the Jupiter system, it's also hardly the biggest radiation source around.

I think our breakdown in understanding here is our concept of cables. When I say cable (and many others here) I mean fiber optic cable. Even with 25km of fiber optic cable it is rather small and light. Drones, missiles, and torpedoes are already doing this with many miles of cable in a tight space. The issue with this which I am not sure about is the dynamic of the ice on the fiber optic cable and how well it would hold up to refreezing of the ice.

Refreezing isn't the big issue; shifting of the ice (causing physical severing of the line) is. We don't have a great handle yet on how much it moves around.

Yes, I think we definitely have a gigantic misunderstanding of cable here. Mine is based in reality, while yours seems to be very unrealistic. How in the world is a fiber optic cable going to do what needs to be done? Where is the power coming from to heat the probe via a fiber optic cable? Even a fiber optic cable at a length of 25km is a very large spool. If you want the probe to hold the spool and unwind as it goes, it must be at least the size of the spool of cable. If you think this would work with an unsheathed piece of bare fiber cable, then your just not even trying to be serious.

I see another misunderstanding then. With this method the actual probe would use nuclear material to melt its way through the ice. In addition, the heat of the nuclear probe on one side and the ice on another (or melting ice) would make for the ideal conditions of a peltier (or just use a traditional RTG) device to power onboard sensors and electronics. The fiber optic cable is only for communication.

> use nuclear material to melt its way through the ice

All 300 watts of it? It's not going to even make an indentation, let alone through 10s of km of ice.

Simple reactors can be designed to be turned up and down according to need. A 300w RTG is more than enough to run all the necessary electronics. The ice-melting 30,000w+ heater can be a second rector that is spooled up only when ice needs melting.

we're attempting to search for life and the thing you want to do is use radioactive heaters? we deliberately crashed a satellite into the planet to avoid having it potentially contaminate the moons we are curious about, and yet you're thinking they'd just irradiate everything like this? it's really just not logical

The concern is more spreading Earth life. NASA's Planetary Protection team (which is a delightful job title) is largely concerned with sterilizing stuff we send out so any discovery of microbes on Mars doesn't turn out to be hitchhikers.

Even a fully fleged nuclear reactor isn't gonna do much damage to Europa and potential life. Swimming in a nuclear reactor's fuel pool is quite safe; water's some of the best shielding we have. https://what-if.xkcd.com/29/

In the outer solar system, under miles of ice, in total darkness and cold .. it is nuclear or nothing. Short of antimatter batteries, there is no other source of power that would be even theoretically suitable.

The spool can be a long, thin "pipe" of wound cable that goes with one end of the "pipe" pointing to the rear (up). You can put an arbitrary amount of cable in a given hole diameter by making the spool taller.

(Google image search suggests that a similar approach has been taken by the TOW, it's not a spool that could be reversed by adding a motor to an axis, more like a tightly packed coil that gets straightened as wire is pulled out)

As for the energy, I assumed GP was thinking of solar panels on the surface. I also assume that we share scepticism based on the low sun intensity out in the orbit of Jupiter... (and that's before you even start wondering how much further away from the melting point that ice will be than all ice of conventional human experience)

>You can put an arbitrary amount of cable in a given hole diameter by making the spool taller.

Wouldn't this be limited to the tensile strength of the material and the weight of the cable? Granted, Europa has much less gravity, but 25km is a lot of cable weight.

Consider something as small as fishing line; one online estimate gives it .245g/m. At 25km, that's over 3 tons of line weight hanging down a hole on Earth or nearly 800 lbs on Europa.

The probe bears on the ice below it and the cable gets held by the ice that's re-frozen above the hole.

What you have to worry about is the ice shifting and severing the cable.

Could you embed a series of metallic needles as you melted your way down, then communicate via radio waves that travel needle to needle? They would not need to be connected. Just close by.

I think there are still mechanics at play that would have to be considered.

>The probe bears on the ice below it

This implies it is bearing the weight of the entire cable above it. So instead of the tensile stress being the limiting factor, it's not the compressive stress. If you're intent is to retract the spool, it would still be in tensile stress as it comes up. (And you'd need enough torque to do so. But maybe you the plan would be to abandon in place).

>What you have to worry about is the ice shifting and severing the cable.

I agree, that's a pretty big concern.

Now I’m wondering whether you could fire sonar pings through the ice and transmit data using an acoustic sonar modem. Then the ice-melting probe could be completely untethered. It would be a profoundly unfriendly probe though: a hot radioactive ball emitting ultra-loud pulses. We would have to attach an apology note.

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