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Old 11th January 2019, 09:42 AM   #1
Crawtator
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Steam propelled spacecraft can explore "forever"

https://phys.org/news/2019-01-steam-...y-explore.html

Interesting research and article. I thought some of you might like to take a look at it and discuss. Seems like it could be a valuable tool in long-term exploration of asteroids, moons and other rocky bodies (or at least any with appreciable water).
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Old 11th January 2019, 09:59 AM   #2
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It looks interesting and practical, but the degree of ignorant and gushing hyperbole that's gone into the article is kind of a turn-off.

Basically, it uses pressurized water vapor (steam) as a reaction mass. As long as each new asteroid or comet it visits can provide enough water to refill its tank, and as long as its energy source lasts, it can continue exploring.
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Old 11th January 2019, 10:53 AM   #3
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It would depend on how long all the electronic and other parts would continue to function. What is the life expediency of electronics these days?
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Old 11th January 2019, 11:01 AM   #4
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I mean, don't get me wrong. This is one of very few practical spacecraft designs that has the ability to replenish its reaction mass after launch. A probe like this, with suitably robust components and a long-lived power supply could conceivably flit from asteroid to asteroid doing science for a very long time.

Voyager and Pioneer have demonstrated the viability of long-lived probes. This development gives such probes a lot more to offer.
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Old 11th January 2019, 11:19 AM   #5
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Originally Posted by Crawtator View Post
Steam propelled spacecraft can explore "forever"
But who's going to volunteer to shovel coal into the damn thing for all that time?
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Old 11th January 2019, 11:20 AM   #6
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More seriously, how can it do that "forever"? It needs something to mine water and something to heat it. That has to run out at some point, and I'll bet it's closer to 20 years than "forever".
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Old 11th January 2019, 11:48 AM   #7
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Well, obviously "forever" was hyperbole. But the article discusses that having this tech as a means of increasing the longevity of missions which costs millions, if not billions, of dollars and increases the mobility of the spacecraft seems like a great idea. I assume the reason this wasn't considered before was due to the fact that, until recently, we had no idea how ubiquitous water was in the solar system. Is that a fair statement?
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Old 11th January 2019, 11:53 AM   #8
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Originally Posted by Hans View Post
It would depend on how long all the electronic and other parts would continue to function. What is the life expediency of electronics these days?
Not sure this answers the question to your satisfaction, but I found an interesting article concerning the different factors which must be considered for space electronics. No firm answers in the article, though, just considerations...

https://www.analog.com/en/technical-...lications.html
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Old 11th January 2019, 12:05 PM   #9
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Originally Posted by Crawtator View Post
Well, obviously "forever" was hyperbole. But the article discusses that having this tech as a means of increasing the longevity of missions which costs millions, if not billions, of dollars and increases the mobility of the spacecraft seems like a great idea. I assume the reason this wasn't considered before was due to the fact that, until recently, we had no idea how ubiquitous water was in the solar system. Is that a fair statement?
Yes but still my question stands: how long could such a craft really operate?
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Old 11th January 2019, 02:00 PM   #10
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Hell if I know. The link I posted concerns all of the factors involved in determining what parts to use and the fail-safe requirements. It doesn't give any information about how long they could last. I think that one of the major problems with this sort of transport of a ship would be the repeated landing and/or drilling of the subject material for water extraction. That sort of vibration would lower the life expectancy of the ship, but I have no idea by how much.

Perhaps an engineer or space-related-field person could answer this question?
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Old 11th January 2019, 02:37 PM   #11
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Originally Posted by Crawtator View Post
Hell if I know. The link I posted concerns all of the factors involved in determining what parts to use and the fail-safe requirements. It doesn't give any information about how long they could last. I think that one of the major problems with this sort of transport of a ship would be the repeated landing and/or drilling of the subject material for water extraction. That sort of vibration would lower the life expectancy of the ship, but I have no idea by how much.

Perhaps an engineer or space-related-field person could answer this question?
Roughly it could last approximately the same length of time as a satellite does now, but travelling through the solar system instead of just orbiting Earth.
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Old 11th January 2019, 02:43 PM   #12
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Originally Posted by Red Baron Farms View Post
Roughly it could last approximately the same length of time as a satellite does now, but travelling through the solar system instead of just orbiting Earth.
My guestimate is in teh range between how long the Voyager probes have lasted (those would have less wear and tear than this idea) and how long the Mars Rovers lasted (those acted in similar ways, but had more to deal with in the way of terrain/weather, I think).

If nothing else, that would give a decent range of expectation, I think.
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Old 11th January 2019, 02:52 PM   #13
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Originally Posted by Belz... View Post
Yes but still my question stands: how long could such a craft really operate?
Until the water filter clogs up.
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Old 11th January 2019, 03:05 PM   #14
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Originally Posted by Belz... View Post
Yes but still my question stands: how long could such a craft really operate?
Probably for a really long time. We have space probes that have been operating for 40 years. We have rovers on Mars that have operated for 2-3 times longer than the original mission plan, and their primary constraint was dust on the solar panels.

The point of this is not that the probe will be able to operate for some magical amount of time. The point is that the amount of reaction mass it carries at launch is no longer the primary constraint on mission duration. And this in turn opens up new opportunities for scientific exploration.

Limited reaction mass means a probe is severely restricted in the bodies it can visit. Most of its travel has to be done passively, via orbital mechanics and carefully-timed launch windows, with minimal course correction and insertion burns. One probe, one asteroid, basically.

With this, a single probe has much more scope to change orbits and rendezvous with additional objects. A probe that will last for decades but only has enough fuel for one visit can now be a probe that will last for decades but has enough fuel to keep visiting new places the entire time.

"How long could such a craft really operate?" is in my opinion a red herring. The answer is simple and groundbreaking. What used to be, "it can operate until it runs out of fuel" can now be, "it can operate until its core components finally break down." Which, the way NASA seems to build probes, would be fifty years after launch.
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Old 11th January 2019, 03:29 PM   #15
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Steampunk.
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Old 11th January 2019, 03:52 PM   #16
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I am not a physicist but:

It seems to me that relying on asteroids to provide fuel potentially interferes with the object being observed - probably enough to severely compromise the research.

On the other hand maybe there are tons and tons of asteroids and it wouldn't be a big deal to suck some of them dry.
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Old 11th January 2019, 03:53 PM   #17
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Originally Posted by Steve001 View Post
Steampunk.
Not enough useless cogs.
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Old 11th January 2019, 04:01 PM   #18
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Originally Posted by Minoosh View Post
On the other hand maybe there are tons and tons of asteroids and it wouldn't be a big deal to suck some of them dry.

This won't be doing that. Way too small to do that.
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Old 11th January 2019, 04:48 PM   #19
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Originally Posted by Hans View Post
It would depend on how long all the electronic and other parts would continue to function. What is the life expediency of electronics these days?
Depends strongly on how they are designed and operated. You can over-engineer them to last a very long time even under very harsh conditions, but that's not usually worth the expense of designing or building them that way for consumers. And in regards to operation, even desktop chips can often be run at a variety of voltages and speeds. Crank the voltage and speed up, you get higher performance but more power consumption and heat (which will lower lifespan). Drop the voltage and speed, drop the performance but also lower the heat and extend the lifespan.
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Old 11th January 2019, 04:56 PM   #20
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There's also little point in over-engineering something past the estimated lifespan of its tightest constraint. Our longest lived probes today are happy side effects of the materials and processes we were going to use anyway, just to make them last long enough to complete the mission.

We have not yet begun to see how long a probe can last, if we had a reason to really try.

This technology gives us a reason.
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Old 11th January 2019, 08:12 PM   #21
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Another possible advantage I can think of is it sounds like a lander based on this would be able to extract itself from the situation the Rosetta lander found itself in.
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Old 11th January 2019, 10:22 PM   #22
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Not a new idea at all

Anyone who has read Asimov's novella "The Martian Way" will remember that the "scavenger" spacecraft in the story used water as a reaction mass.
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Old 12th January 2019, 12:02 AM   #23
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My problem with this is how fast would the steam be going when it leaves the craft? If it is not very fast then it would not give much thrust.

I suppose it could super heat water then allow the steam to escape to provide thrust. But that would require a lot of energy and water. Plus a strong tank to hold the water.
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Old 12th January 2019, 03:47 AM   #24
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Originally Posted by RecoveringYuppy View Post
This won't be doing that. Way too small to do that.
I'm used to thinking of spaceships as fairly large and asteroids as small with little to no water available. So the smallish craft (the size of a VW bug? Or much smaller?) would scoop up ice and melt it/boil it with solar power? Have we identified a lot of asteroids that we could navigate to, that have H2O in useful quantities?

It's blown me away, what planetary scientists have been able to do with Mars landers and orbiters, the Cassini mission and the Voyager probes. But still, I have a terrible imagination when it comes to space exploration. What is the utility of an asteroid-hopping self-fueled probe, and what would be its limitations? Is there any chance it could yield clues about how life started on Earth, and would that knowledge be compromised by using parts of asteroids as fuel?

Last edited by Minoosh; 12th January 2019 at 03:53 AM. Reason: Trying to come up with credible scenarios
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Old 12th January 2019, 05:11 AM   #25
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Originally Posted by Hans View Post
It would depend on how long all the electronic and other parts would continue to function. What is the life expediency of electronics these days?
I doubt the electronics would be the bottleneck. Presumably there are mechanical parts for collection of water as well as some form of steam turbine itself. Would imagine these would fail long before electronics would.
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Old 12th January 2019, 07:46 AM   #26
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Originally Posted by Minoosh View Post
Have we identified a lot of asteroids that we could navigate to, that have H2O in useful quantities?
Since this apparently has enough thrust to take off from any object without an atmosphere, it's fair to say that we know of comets, asteroids, Moons, and even dwarf planets that have vast plains of ice, some rivaling Siberia in size.

Even without knowing the details of how "wet" an object needs to be for this device to work it's definitely the case that there are a lot of objects it could visit.
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Old 12th January 2019, 08:41 AM   #27
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I did not know there was that much water in the solar system, or how much gravity limits landing sites.

Would this be more of a lander or an orbiting/fly-by craft?
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Old 12th January 2019, 09:23 AM   #28
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Battery life? I see that the ISS batteries have an expected life of ~6 years, so with journey times in the dimmer outer reaches of the Solar System being measured in years or even decades the batteries' performance looks like a major issue.
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Old 12th January 2019, 09:32 AM   #29
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It would have to get in contact with the object it's extracting water from, so lander, or "docker" for low gravity objects, would have to be one of it's capabilities.

This is just a prototype so what it could "actually" do is a bit speculative now. But the idea that a steam powered thruster could get to and from any object without an atmosphere is a very workable idea.

Based on current understanding we expect that the moons and planets of the solar system have approximately 30 times the liquid water that Earth does. Water in the form of ice is way beyond that. H2O is hydrogen and oxygen, two of the most common atoms there are. H20 is one of the most common molecules there are. It's quite possible that it's the second most common molecule in the solar system. It's certainly near the top. Despite being home to the only known liquid surface oceans we actually live in a dry part of the solar system.
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Old 12th January 2019, 09:40 AM   #30
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Originally Posted by GlennB View Post
Battery life? I see that the ISS batteries have an expected life of ~6 years, so with journey times in the dimmer outer reaches of the Solar System being measured in years or even decades the batteries' performance looks like a major issue.
In the first place we have Radioisotope batteries and even nuclear reactors that can power spacecraft.

But getting your fuel from a source based in space is a game changer. It makes it feasible to talk about going places without being concerned about minimum energy orbits. Moving 5 to 10 times faster becomes a near term goal.
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Old 12th January 2019, 10:26 AM   #31
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Originally Posted by Minoosh View Post
I did not know there was that much water in the solar system, or how much gravity limits landing sites.

Would this be more of a lander or an orbiting/fly-by craft?
The article was very thin on details, so it's hard to really evaluate how this would work in practice. By definition, this has to be used with a lander. I suppose you could have a lander with an orbiting mothership, but since the mass of the spacecraft is likely to be dominated by the fuel load, there may not much advantage to leaving part of the system in orbit, and it adds a lot of complexity, so I'm assuming it's always just a lander.

Also, if they're just using it for flybys, I don't think that this would actually work any better than a conventional non-refillable ion thruster because the efficiency of the ion thruster should be so much higher that you'd need an unreasonable number of refueling cycles to break even.

(I was working on a more detailed response here, but it was getting really long and I hadn't even gotten to my main point so . . . )
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Old 12th January 2019, 12:34 PM   #32
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Originally Posted by GlennB View Post
Battery life? I see that the ISS batteries have an expected life of ~6 years, so with journey times in the dimmer outer reaches of the Solar System being measured in years or even decades the batteries' performance looks like a major issue.
I think battery life is more measured in discharge / recharge cycles. The ISS batteries probably would go though these rapidly. The steam propelled spacecraft would go though these very slowly. Hence the batteries would last decades.
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Old 12th January 2019, 12:42 PM   #33
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Originally Posted by rjh01 View Post
I think battery life is more measured in discharge / recharge cycles. The ISS batteries probably would go though these rapidly. The steam propelled spacecraft would go though these very slowly. Hence the batteries would last decades.
Concur. LEO spacecraft (like ISS) are brutal on batteries; generally they have to discharge the batteries every orbit and the LEO orbits are pretty short (less than 2 hours). An interplanetary spacecraft could go years without having to use the battery, depending on the system design.

I'd still be nervous about battery life for a multi-decade mission, but I agree that ISS isn't representative.
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Old 12th January 2019, 12:54 PM   #34
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Originally Posted by RecoveringYuppy View Post
In the first place we have Radioisotope batteries and even nuclear reactors that can power spacecraft.
Yup. And they all have finite lifetimes. Unless the WINE can be modified to mine for radioisotopes, then process and install them. Alternatively, for operation in the inner solar system you can use solar cells, but they also have finite lifetime, and the WINE would need to be able to produce replacements. In principle this is not impossible (space is a decent vacuum, which makes solar cell production a lot simpler, but still....).

Quote:
But getting your fuel from a source based in space is a game changer. It makes it feasible to talk about going places without being concerned about minimum energy orbits. Moving 5 to 10 times faster becomes a near term goal.
This does not get its fuel from "a source based in space" - it gets its reaction mass, which is quite a different story. And no, it does not allow ignorance of things like minimum energy orbits, since the vehicle has to be able to produce enough delta-v to dock with a target water source. What it does allow is "puddle-jumping" around the asteroid belt or the Kuiper belt. In all cases delta-v is low, and the issue of locating the next body to be exploited is completely ignored. As Sagan remarked, "Space is big", and bad sci-fi movies to the contrary, asteroids are a long way apart.
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Old 12th January 2019, 01:01 PM   #35
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Originally Posted by WhatRoughBeast View Post
Yup. And they all have finite lifetimes. Unless the WINE can be modified to mine for radioisotopes, then process and install them. Alternatively, for operation in the inner solar system you can use solar cells, but they also have finite lifetime, and the WINE would need to be able to produce replacements. In principle this is not impossible (space is a decent vacuum, which makes solar cell production a lot simpler, but still....).
Don't be ridiculous.


Originally Posted by WhatRoughBeast View Post
This does not get its fuel from "a source based in space" - it gets its reaction mass, which is quite a different story.
True about water being the reaction mass but remember that sunshine you mentioned?
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Old 12th January 2019, 01:10 PM   #36
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Originally Posted by RecoveringYuppy View Post
In the first place we have Radioisotope batteries and even nuclear reactors that can power spacecraft.
I was going to post about their still 'limited life', but WhatRoughBeast beat me to it. Then you retorted with 'sunshine', but that just gets us back to solar panels and batteries.

wtf? None of this points to such a thing buzzing around 'forever', and even a decade is huge stretch of the imagination.
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Old 12th January 2019, 01:15 PM   #37
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The people who think that putting forever in quotes means we're supposed to take it literally are just being too stupid to take seriously.
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Old 12th January 2019, 01:32 PM   #38
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Originally Posted by RecoveringYuppy View Post
The people who think that putting forever in quotes means we're supposed to take it literally are just being too stupid to take seriously.
Lovely dodge. How seriously should we take:

"We could potentially use this technology to hop on the Moon, Ceres, Europa, Titan, Pluto, the poles of Mercury, asteroids—anywhere there is water and sufficiently low gravity."

when each launch to each new destination is powered by steam? How long is the steam-powered trip from Ceres to Pluto, just by way of example?

It's all a load of bollocks, designed to attract funding from idiots that have more money than sense.
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Old 12th January 2019, 01:37 PM   #39
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We should take that seriously. It's you that should be ignored.

BTW I think they are actually understating the potential. There doesn't have to be water at every potential landing site. We got on and off the Moon without having to refuel. This technology won't need to either.

Are you not aware that we've already been to Pluto? Extrapolate from there.
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Last edited by RecoveringYuppy; 12th January 2019 at 01:38 PM.
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Old 12th January 2019, 01:52 PM   #40
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Originally Posted by dasmiller View Post
The article was very thin on details, so it's hard to really evaluate how this would work in practice. By definition, this has to be used with a lander. I suppose you could have a lander with an orbiting mothership, but since the mass of the spacecraft is likely to be dominated by the fuel load, there may not much advantage to leaving part of the system in orbit, and it adds a lot of complexity, so I'm assuming it's always just a lander.

Also, if they're just using it for flybys, I don't think that this would actually work any better than a conventional non-refillable ion thruster because the efficiency of the ion thruster should be so much higher that you'd need an unreasonable number of refueling cycles to break even.

(I was working on a more detailed response here, but it was getting really long and I hadn't even gotten to my main point so . . . )
I can see that they might want to have two parts to the spacecraft. Have both a lander and an orbiter. The lander would not have many solar cells. Nor a powerful rocket. The orbiter would have many of the scientific instruments. The lander could even be two landers. One part would do all the mining and producing the water and the other part would ferry the water between the first part and the orbiter. The lander might want to land in an area that does not have much contact with the Earth. But that is ok. It can communicate via the orbiter.
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