Limiting probes to only those that can get through 10s of kms of ice is short-sighted.
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.
On a more serious note, it's a travesty that lawyers get all the hate and PEs get none.
Code & techbros are not the solution to everything.
Where is all of this energy coming from?
A nuclear reactor, probably.
All 300 watts of it? It's not going to even make an indentation, let alone through 10s of km of ice.
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/
(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)
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.
What you have to worry about is the ice shifting and severing the cable.
>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.
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 that's not your claim then I don't understand your valuation and the rest of the comment doesn't track.
And not to engage at a base level but my use of immeasurable is correct in being interpreted as "large" unambiguously, at least by Merriam webster.
A "viable billion dollar mission" includes all sorts of other things that are of value, including developing capabilities to do things that are strategically important, which I would claim is where a large majority of that billion dollars comes from. Similarly, I would expect that JPL would very much inflate the value of their own work. Everyone does.
Also, I see "incapable of being measured" with "broadly : indefinitely extensive" tacked on in the MW definition. There is no requirement there that "immeasurable" mean "large", just "incapable of being measured" with the expectation that it is used when describing things that are extreme. My most recent use of "immeasurable" was "immeasurably small" which I'm sure you would agree is a proper use.
Hosting the photos costs money too, which I don't think GP is considering.
If NASA had to personally crowdfund these $5b missions, they'd probably still happen. That sum is also in the ballpark of Apple's marketing budget - I would not at all be surprised if they spent that much just to get their logo on the mission. Not to be outdone, Samsung pays next one.
But maybe you wanted to talk about the value-add to the society instead - which is easily going to dwarf $1m by many orders of magnitude just through advances in sciences, industry, and international cooperation that happen in the course of planning, building, executing, and pouring over results of such a mission. All of these things have a tendency to accrue interest, so the sooner, the better.
You could also take a state-centric view, and there also I guarantee you that the value of the image-lift and international cooperation is going to be worth more than a measly $1m to the US. A US president making a single international state visit costs multitudes of that.