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Trying to figure out the practicalities of drilling through the ice on Europa's surface, to drop a sub into the water beneath.

From what I understand the three most viable methods would be

  1. Wait for a crevice or opening to form and go through,

  2. Melt through,

  3. Drill through.

For the purpose of the question, assume that we have already got a nuclear-powered vehicle to Europa, that can be used to supply enough power for whatever method is used to get through.

Q1 - If melting or drilling, what is the fastest we might be able to get all the way through. Are we talking minutes, hours, days/weeks?

Q2 - If trying to find a way to slip through a crevice or an opening - what exactly might this entail? Would it literally be a matter of waiting until an opening appears, then quickly offloading the sub down into the water?

thanks!

S

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closed as too broad by Mołot, Ash, Renan, Rekesoft, L.Dutch May 22 '18 at 16:22

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ How big is the sub? $\endgroup$ – Dan Clarke May 22 '18 at 13:18
  • $\begingroup$ Assume around 150ft. Could be slender or turtle shaped. $\endgroup$ – J Seale May 22 '18 at 13:29
  • $\begingroup$ One question per question. please. Make sure you'll find a moment to look at tour and help center, too. $\endgroup$ – Mołot May 22 '18 at 13:53
  • $\begingroup$ Getting in, you can either melt or drill. But how do you get out? $\endgroup$ – user47242 May 22 '18 at 14:04
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    $\begingroup$ This is not about Worldbuilding it's about aerospace engineering and you could "write a book about it" because it lacks too many specific details as well. $\endgroup$ – Ash May 22 '18 at 15:13
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Drill through.

A motorized road ice scraper can remove about half an inch of ice at every passage. So you place the scraping heads of several of them on a beam, yet others on another beam etc., until you build a spoked wheel. You've now got a boring head - basically a vertical tunnel boring machine. Between head and head, nozzles can be set up to spray tiny jets of hot water under high pressure, to break down the ice and make the work easier for the scrapers. The water can be recycled indefinitely.

With sixteen orders of scrapers and turning at ten RPM, which isn't much when boring through ice, the disk can bore at about two meters per minute assuming each head has the same efficiency of a road scraper. The pulverized ice can be pumped up using tubes filled with gas (I expect that occasionally the tube will need to be flushed with hot gas to prevent blockages). Or it can be pressed into hollow, Teflon-coated tubes using pistons.

The scraping disk is lowered from the surface, with the submarine on top of it. When it arrives at the ocean, it is lowered further so that the submarine is released gently, then it is brought up again.

Depending on the ice resistance and risk of a collapse, the tunnel might be excavated by a two-part boring head: the boring disk itself, over which the sub is hosted. And a hollow vertical cylinder, as wide as the tunnel, with vertical treads, capable of going up and down. Instead of the winches being on the surface, and ten kilometers' worth of cables be paid out, this cylinder would lower itself inside the tunnel and keep the boring disk going down at constant speed. It could have horizontal drills capable of penetrating for several tens of meters inside the walls, injecting water just above 0 °C and letting it freeze in place (allowing for ice expansion, of course - we don't want to frack the tunnel walls). Or it could keep a central layer at a temperature just above 0 °C. In both cases, the end result is that any cracks or vacuum pockets or irregularities in the tunnel walls get replaced by solid ice.

At one seventh G, the risk of the tunnel walls becoming so much denser than the average Europan ice, that they get torn down by their own weight should be negligible even when considering ten kilometers' worth of depth. Also, a height of ten kilometers (1350 m Earth equivalent) are well within the compressive strength of Ice XI.

(the melting method to reach the ocean of Europa is detailed in Charles Sheffield's Cold as Ice, using a fusion generator devised by Cyrus Mobarak).

In reality

Following up to Richard Hansen's comment, I found out that this design has already been developed and tested. The speed of the Rapid Access Ice Drill is around 3300 meters in 200 hours, including setting up camp and dismantling everything; I think it's safe to assume around 25 meters an hour. The RAID uses slowly rotating medium speed drills, electrically powered; using fusion power sources is likely to go a lot faster, e.g. combining hot water drilling and grinding heads.

enter image description here

Other possibilities

Orbital microwave cannon - it would melt the ice, then boil the water, and finally disperse the water vapour. This has the advantage of very low risk from cave-ins (but still requires lowering the sub somehow). On the other hand, a ten-kilometer borehole full of microwaved gas without a real atmosphere, in about one seventh gee, will create a plume possibly high enough to interfere with orbital vehicles before being dispersed by the solar wind. Internal refraction of microwaves and ablation from the rising vapor plume will also cause the tunnel to grow larger at the mouth, and require proportionally more energy to be excavated.

Orbital kinetic strike - assuming a very dense impactor (depleted uranium/tungsten alloy), the Newton penetration formula in ice XI gives a length factor of around 20: that is, the penetrator will punch 20 times its length before dispersing its momentum. Drilling a ten-kilometer bore will require a 500m solid metal penetrator, or multiple accurate KEW strikes. There is the risk of the ice fracturing, which can interfere with the sub operations.

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  • $\begingroup$ Thanks for the info. So you'd estimate approx three or four days drilling with a boring machine? If we were to assume 10km of ice? $\endgroup$ – J Seale May 22 '18 at 13:43
  • $\begingroup$ Yes. The same setup can be used to retrieve the sub, too. $\endgroup$ – LSerni May 22 '18 at 15:03
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    $\begingroup$ @LSerni, even given 20 days, it's only half a foot a minute. I also think it is fair to take into account that there will be delays to cold equipment failure. Just because we are on Europa does not mean that the cold wont wreck havoc with fluid systems. You are correct that you don't need to worry about preserving the core or avoiding contamination of the ocean, but you do need to drill a larger hole. Currently LSU is doing research on using lasers to bore through Arctic ice. I'm running out of characters so I will just refer to VALKYRIE and DEPTHX. The goal is to eventually deploy to Europa $\endgroup$ – Richard Hansen May 23 '18 at 16:16
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    $\begingroup$ Decided to add a second comment. But you are right that it did not take the full 20 years. I just think your ice scrapping idea is overly optimistic. The programs are basically currently similar to the Russian one in that they want to study subsurface water, but vastly different and higher performing methods. They are dropping drones down the holes and getting pretty detailed maps of the the lakes. $\endgroup$ – Richard Hansen May 23 '18 at 16:22
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    $\begingroup$ Also... i'm not sure why speed is so important... fastest Humans have managed to reach Saturn was voyager 1 in just over 3 years, why not slow down do it right, whats a few more days when you're working on that scale... and also, scientists will never stop worrying about contaminating an environment they are wanting to study, NEVER! $\endgroup$ – Blade Wraith May 24 '18 at 8:32
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First off, we assume this is an internal sea on Europa, based on the evidence we've seen so far, however we do not know for certain if it is small localized pockets of liquid water or a massive sea, how deep it is or more importantly how deep the ice is. i know that's a strange point but it is worth realizing that fact. for the sake of argument, we'll assume there is a massive sea under the ice. Which i do admit i hope is the case.

The Geysers

Probes would likely be sent to observe the Geysers to research them, however they would not "wait for an opening" as by the time it opening the outward pressure would be too high to send something down, and once the geyser stopped the hole would quickly freeze over thus limiting the ability of the probe

Drilling

Drilling is definitely going to be the best option, mainly because this mission would be a scientific mission, so most likely they would land a core sampling device on Europa, so they could analysis each layer of ice as they dig, this would give them far more information then melting the ice. and i would assume this core sampler to capture each Core, and then Store them for eventual analysis by Humans. This hole would be likely be about 10 cm in diameter

Once the probe has reach liquid water, then it would most likely send a very long arm covered in analytical systems done the hole, and into the water, this would most likely stay there as a near permanent fixture.

Second Mission

After they had confirmed the theory about an ocean, and hopefully found something worthy of note, then maybe they would send a large craft, in that event they would most likely send large drilling platform to open a hole about the size of a dustbin lid. and small Underwater Unmanned Vehicles (basically a remote control torpedo without lab systems instead of the bangy bit) would be sent to investigate, but it would be powered by a cable running to the surface, Nuclear Powered Probes have been theorized before, but never used as they risk exposing their target research to radiation and therefore potentially destroying that which they hope to find. they UUV may take water water samples and return them to the surface to be picked up by a later mission or even for the Landing Vehicle to have a return vehicle that could deliver the core samples and water samples back to earth. however once again, doing so posing a risk to the samples themselves by exposing them to the harsh environment of space and more significantly, re-entry.

Likely the samples would never return to Earth, and there is a huge list of requirements space probes has to go through if they ever expect to make contact with Water, liquid or frozen, none of the Mars rovers are permitted to go anywhere near the Ice they've found on the surface, just in case they managed to cross contaminate it with microbes from Earth.

Again you don't want to risk killing anything that you're hoping to find

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  • $\begingroup$ Thanks. The drilling platform makes sense. I guess this could be scaled up, if trying to position a larger vehicle under the ice $\endgroup$ – J Seale May 22 '18 at 15:21
  • $\begingroup$ Realistically it has to come down to the why? Lserni's idea for drilling a large hole makes sense, but what are they trying to gain, Scientists would definitely want to keep the core samples all the way down for testing, and UUVs are incredibly capable craft even today, let alone whenever a mission like this might get launched. smaller the better, because its lighter, therefore easier and cheaper to launch off Earth, if you had a rocket capable of landing 8000kgs on Europa, and you had everything you needed in a 1000KG UUV, then why not send 8 of them instead of 1 big one. $\endgroup$ – Blade Wraith May 22 '18 at 15:56
  • $\begingroup$ Fair point. I think it would be on the assumption that they had already sent UUVs down, found something of interest, and now wanted to send a manned vehicle down for further investigation. That second bit is a bit of a leap but I think it would be OK if what the UUV had found could justify it. $\endgroup$ – J Seale May 22 '18 at 18:02
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Punch through.

Your proposed methods are all useful for terrestrial ice breaking operations. But on Europa, you have an extremely energetic option not available on earth - gravity slingshot of an interplanetary ice impactor craft.

Swing your ice impactor around a suitably positioned body and bring it down into Europa at speed. It will break you some ice. You might want to have your research vessel in orbit at a safe distance. Bring it down right behind the ice breaker craft.

A similar endeavor has already taken place - the Deep Impact mission. You could deliver more (or less?) energy by tweaking the speed and mass of your impactor. https://www.nasa.gov/mission_pages/deepimpact/spacecraft/impactor.html

enter image description here

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  • $\begingroup$ Interesting, had not read much about this method before... $\endgroup$ – J Seale May 22 '18 at 15:20
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Drill

you can get down through the ice either way.

When it comes time to go home, your submarine needs to be able to climb out of the ice. You may be able to get out with an ice volcano, but I wouldn't want to count on it, if I was on the sub. I'd want the ability to drill upwards at an angle and haul myself out on treads.

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