India: Yeah, we would like to 3D-print igloos on the Moon The Indian Space Research Organisation (ISRO) is planning to build igloos on the Moon with a view to creating an Antarctica-like outpost. Dr Jitendra Singh of the Department of Atomic Energy and Department of Space gave the response to a question (PDF) asked in the Indian Parliament by Shri Suman Balka last week, a member of …
Escape velocity on the moon: ~2.4km/s
Muzzle velocity of current cannon/ordinance: ~1.2km/s - ~1.7km/s
Current ordinance isn't up to the task (and is hella expensive). A dedicated system may be able to surpass escape velocity, but will still be hella expensive, especially considering the amount of waste that gets generated.
You won't neeed to throw it upwards. When done with your rubbish just throw it over the edge of the moon and it will disintegrate in Earth's atmosphere. Just don't drop any rocks.
As one thicko Murican politician seems to think - people throwing rocks off the moon towards Earth is a serious risk.
Wikipedia tells me that the US test fired a rail gun with a muzzle velocity of 2.5 km/s in 2008. When I was a little boy, a picture book suggested that a linear accelerator would be used to get Lunar material into orbit. IIRC, the same concept is present in Duncan Jones' film Moon.
While I don't deny either of those things, I would like to point out that I said current ordinance - Railguns are still only found as prototypes (feel free to correct me if I'm wrong).
They also have an issue that the military are trying to accelerate hunks of magnetic metal in a magnetic field while the LUnar GarbagE Railgun (LUGER) would predominantly be accelerating plastics of some description.
That last paragraph was mainly to justify coming up with a referential acronym for the system. I still think that the prohibiting factor in this would be cost - 1/2mv^2 is a harsh mistress.
If you're capable of building a sustainable base on the moon, then cost isn't going to be an issue because you've already solved your energy problem.
As to the rail gun... you can use anything within the payload. Google Sabot round. At issue is aiming the payload and the payload being a smart payload which can change trajectory because the rail gun can't.
I'm aware of sabots, but, possibly going a bit too far down the rabbithole mentally, I was thinking that if you're throwing rubbish away, it would probably be best if you were to not have to manufacture casings for the rubbish you're hurling into the void.
Then my mind started working on a way you could design the system so that you loaded the rubbish into a container with no top that will stop by some means (probably including springs and/or shenanigans involving reversing the polarity)
As has been pointed out above though, the whole premise is utterly stupid on chips unless you're trying to make the events of Wall-E happen.
"Railguns are still only found as prototypes "
Railguns have a tendency to self destruct (magnetic flux forcing the rails apart), but their top speed is only limited by atmospheric friction. That "blowing themselves apart" problem has been around since the Nazis started playing with them in the 1930s and the USA hasn't solved the problem yet (although China may have done. They're not publicly claiming it yet, but it looks like they've actually put a railgun on a ship, which nobody else has ever done.)
Linear accelerators don't go quite so fast but they don't tend to fly apart. They can go more than fast enough to reach lunar escape velocity.
None of this matters for the subject at hand. Biological waste is valuable enough that you'd want to retain and recycle it on a lunar colony, not dump it. The Moon is a Harsh Mistress and There Aint No Such Thing as a Free Lunch.
Current ordinance refers to regulations - I can't see them firing items anywhere.
However, current ordnance, in the sense of guns, probably (I bow to your superior knowledge) won't produce the speeds required. But that's just a design feature - I'm sure they could fire things faster with a new design if they wished...
"Escape velocity on the moon: ~2.4km/s"
With a large solar array, plus a big pile of supercapacitors and switching gear, that's possible. For the record, ~2.5km/s used to be acheivable using the UK's prototype 90mm bore railgun, but we sold it to the USA for use on their test/development program.
Throwing rubbish away, unless it is on a trajectory to the sun, is always a bad idea.
Once people burned rubbish, or buried it in the garden (I still find the odd old bottle). They dumped it in the sea ('the sea is big enough to swallow everything'), they dumped it in rivers, they dumped it in holes in the ground. Round the corner from me they dumped it down an old mine shaft, which they later capped. Then the old car wedged in the shaft rusted, the pile collapsed and a nice new hole appeared where the kids play.
In every case it comes back and bites someone in the bum.
Reduce, reuse, recycle. Rubbish can't be forgotten about.
Some of the public lavatories in Alberta's park areas appear to be merely thrones where one defecates into a cavernous area underneath, no septic tank as far as I could tell (Not that I have looked too closely nor indeed wanted to), not a place to lose your phone (No I didn't).
"thrones where one defecates into a cavernous area underneath"
aka "Long drop" or pit latrine - like what your great-great-great-grandfather/mother used to use. (and some of us who are much younger remember from our childhoods along with telephones that had crank handles)
In general you toss lime into them regularly and periodically dig a new hole. A sense of smell is definitely a handicap.
Is this really something we should worry about? Since there is no atmosphere and no running water on the Moon, trash will remain exactly where you put it forever. Just bury it - some of it might be useful again in the future so even if shooting it into the Sun was remotely practical I think it would be a bad idea.
Even if there was a substantial lunar colony the amount of trash generated is likely to be small by Earth standards, since the value proposition of recycling will be so much better versus bringing stuff from Earth or making it locally.
Something particularly hazardous like radioactive waste or toxic chemicals you might want to bury a little deeper and further from inhabited areas, just to protect against the unlikely possibility of a meteor landing on top of it and sending it flying...
"Something particularly hazardous like radioactive waste or toxic chemicals you might want to bury a little deeper and further from inhabited areas, just to protect against the unlikely possibility of a meteor landing on top of it and sending it flying..."
Or in case it reaches a critical mass and explodes with such force that it splits the moon in half, send the survivors on a magical interstellar tour such that they reach a new star system every week and manage to spend a few days at each.
there are better materials than ICE, and could be made from moon dust which is basically 'regolith', not unlike concrete in many ways.
https://en.wikipedia.org/wiki/Lunarcrete
additionally, there have been several proposal with respect to ice as a construction material, one which was proposed back in WW2...
https://en.wikipedia.org/wiki/Pykrete
this example uses wood pulp plus ice, but there are other potential materials as well, that would help prevent the ice from subliming away in the vacuum on the moon.
Another good alternative would be GLASS. Yes, GLASS. And the lunar surface contains a lot of Titanium, which would be really good for support.
So now you get building materials that are local to the moon, and require very little (if any) water to make:
a) sulfur-based or other 'dry' concrete
b) titanium mined on the moon
c) glass made from silicates on the moon
d) solar and nuclear energy to power it all (2 weeks of night every month, so you'd need something to power stuff when it's dark, and nuclear makes the most sense).
Anyway, an igloo is kind of odd and impractical. But using LUNAR MATERIALS is definitely the way to go.
I see where you are coming from, and tend to agree. But the basic technology developed for 3D printing igloos from regolith could perhaps be adapted for printing cheap igloos/huts out of Indian soil? That might help relieve the problem in rural areas, but not in city slums.
And in a (generally) warm and dry climate (okay, yes, monsoon...) a 'shanty' may actually be borderline acceptable as somewhere to live. If it came to priorities, a decent shanty with clean water, sanitation and some electricity may be preferable to a nice shiny igloo with none of them.
....and a country like the UK can spaff money on things like Trident and brexit when they don't have affordable housing for most of the population, feed school children, etc. etc.
At least this sort of thing generally has useful spin-offs. I've yet to see anything useful come out of nuclear weapons and xenophobia.
Well there is at least one useful thing that came from nuclear weapons : an understanding of meteorite impacts.
It was the study of the first nuclear crater that revealed many common points with what are now called impact craters.
So that's one good thing in a literal sea of horrific consequences. Was it worth it ? I don't know.
I do, however, know that xenophobia has never done any good anywhere at any time.
Native Americans (i.e., American Indians) would have fared much better with a huge helping of xenophobia. They couldn't have fared worse. Welcoming hordes who want to destroy your culture is not a good survival tactic.
My ancestors of the first part had no effective means to resist my ancestors of the second part. An unfriendly welcome would have delayed things by a decade or two--except that instead of almost a century of more-or-less friendly relations, things would have been decidedly unfriendly. Europe was in the middle of conquering the world due to technological advances and population pressures. The tech deficient here was far too great for the locals to have any chance of repelling the migration.
"....and a country like the UK can spaff money on things like Trident and brexit when they don't have affordable housing for most of the population, feed school children, etc. et"
you know, MOST of that could be fixed with pure capitalism. You have to assume that the reason people have no housing is that it's not being built fast enough, the reason they have no food is because it's not being produced in farms fast enough, and the reason people lack money is because they don't have jobs.
So what's the solution? pay out tax dollars to people who claim they don't have enough money to get housing/food/etc.? I think NOT (think of where it has to come from, and how UNsustainable THAT would be). Instead, you ENcourage private enterprise to do what it's good at, create jobs, produce stuff people want, and tell GUMMINT to just STAY OUT OF THE WAY as much as possible. [yeah here come the exploitation arguments, yotta yotta - *yawn*]
Just stating "the obvious" ya know?
So, where are all of those "straw man" xenophobics anyway? Maybe there's a handfull of wackos, but that's it, right? Do YOU know any xenophobics? I mean REAL xenophobics, not "accused of it" because "political correctness" or something, the way the P.C. fascists throw around 'word of the day'-phobia accusations right/left/up/down/wherever all the time. And if you do not know anyone that's a xenophobic [likely], then ARE there any in significant numbers? And that's my point. People just want to live their lives in private and not be disturbed or coerced by anyone/thing, because THAT is human nature. I think most people are really like that. And I know a LOT of people 'like that'.
And nuke weapons helped prevented the world from falling to fascism and communism. I think _that_ is pretty useful, don't you?
"and tell GUMMINT to just STAY OUT OF THE WAY as much as possible. [yeah here come the exploitation arguments, yotta yotta - *yawn*]
I think all the recent exposés of the likes of Cambridge Analytics, Facebook, Google and their ilk shows what capitalism gets up to when the law is failing to keep up and regulation is light.
I think it's nice to live in a country where a free press can actually legally write negative pieces about the expensive and dangerous ventures assumed by a less-than-competent government, like free wealth transfer-funded universal healthcare.
Save your pence. When you require a timely life-saving operation, you'll be getting on a plane and paying for it yourself.
Given that ISRO seems keen to attract foreign launch customers and there's apparently a continual effort to drive down development costs I think making a meal of India's economic disparities is a bit disingenuous, no?
Or should Indian industry be limited to diesel tractors and mud brick factories?
I had very fond memories of watching Space 1999 as a kid so took it upon myself to acquire the complete set. They say never meet your heroes. I'd add to that, leave nostalgia where it belongs - in the past.
I haven't summoned up the courage to watch UFO yet. Could it be worse?
On Earth we would use cement, mud or adobe. I guess one could sinter (fuse) the powder material by aiming an array of mirrors at one spot (then spread more powder on top and repeat - effectively the same process as Selective Laser Sintering of titanium powder on earth).
The mirror array can be relatively lightweight, seeing as how it doesn't have to withstand any wind, and not too much gravity. However, it will require a mechanism to shed off lunar dust that settles on the mirrors - perhaps a rapid vibration such as is employed on DSLR sensors.
How does this 3D house printing compare with an inflatable structure which can be used as a former for polyurethane foam?
Excellent questions.
The basic requirements seem to be:
1) uses locally sourced materials
2) strong
3) can be made airtight
4) extendible
It has been suggested elsewhere that a good approach is to build structures (however you want) and then cover them with a good layer of loose regolith for protection, so expanded foam doesn't sound like a goer. A network of connected 3D printed igloos, covered in regolith, could be quite cosy, as well as cheap and practical. Be nice to have a few windows though.
However, it will require a mechanism to shed off lunar dust that settles on the mirrors
My understanding is that lunar regolith is a nightmare because it becomes electrically charged and sticks to things electrostatically. The solution to this on a mirror (effectively a piece of shaped foil) would presumably be to have a potential difference between the mirror and a grid-shaped collector electrode underneath so that all the regolith sticks to that instead. Periodically reversing the potential for a short time would clean the collector.
Reversing the polarity seems to fix most things in space.
"
However, it will require a mechanism to shed off lunar dust that settles on the mirrors
"
What dust? The only dust that will be above ground level will be that kicked up by any activity - and that doesn't travel far and is short-lived. Each dust particle will behave the same as a large rock in the speed with which it falls back to the ground. Just situate the mirrors out of the arc of dust that the printing process might be raising, and they will remain pristine.
"How does this 3D house printing compare with an inflatable structure which can be used as a former for polyurethane foam?"
sounds good to me. and it could be made RE-USABLE to make MORE structures after the concrete cures.
https://en.wikipedia.org/wiki/Lunarcrete
ok - you'd start with a thin enough layer so that the inflated structure doesn't collapse under the weight. But then, you remove the inflatable part, then build on top of the existing layer. I'd also assume some kind of support structure underneath it as well, not just air pressure. Lunar titanium. But it would begin with the inflatable structure that you mentioned. It's a good idea. I like it.
"The mirror array can be relatively lightweight, seeing as how it doesn't have to withstand any wind, and not too much gravity. However, it will require a mechanism to shed off lunar dust that settles on the mirrors"
A second, larger array of mirrors to burn off any dust that settles on the first one. Of course, that will then have its own dust problems, but the solution at this point should be obvious...
"A sphere or igloo-like dome is the most efficient shape for a habitat in a vacuum."
Well which is it? Igloos aren't spheres -- they're helical catenoids.
As you say, "the devil is always in the detail."
Well the solution's easy innit...
Just set up huge bonfires, strategically placed around the moon's surface. Add a few oxygen bottle for y'know, combustion, set them going... let the CO2 gather in the atmosphere.. plant a load of space-trees, and other various hardy plants.. they eat the CO2, produce oxygen... and that's the moon terraformed ready for the populace to move to.
Foolproof plan. I should be King of Earth.
If the Moon's atmosphere was extremely high pressure, then this statement would be a slam dunk.
Unfortunately, it's the opposite. It's a hard vacuum and are we planning to pressurize these habitats? The pressure differential might assist in holding up a large flat roof.
All things considered, it's very unlikely that a minimum surface area sphere is optimum shape.
By the way, has anyone figured out how to 3D Print a lintel in place. Specifically, making the Lintel Paste hang in mid-air (or on the Moon, hang in mid-vacuum) over the door or window opening, precisely the way that soggy paste generally doesn't in a gravitational field. Perhaps the Wall Paste Cartridge tube would have pre-hardened lintel beams distributed throughout the paste, and the 3D Printer would somehow squeeze its cheeks together and peristalsisly select and push-out a pre-hardened Lintel on command. Or perhaps, someday, doors and windows will be 3D Printed in place, complete with associated hardware (door knobs, hinges). Someday soon, all habitats will be 3D printed. Right down to 3D Printed lovely warm bread in the 3D Printed oven.
Your problem could be solved by 3D printing construction bricks of various dimensions, then using something like this to lay them afterwards. Sort of a giant Lego technics set!
https://youtu.be/FXhZEV22Jrw
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