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Say I want a world where there are many moons orbiting the Earth. They will be man made (so no convenient asteroids).
So there is a scientist and he designs moons.
How far forward from modern day society (2016) would we have to be so that moons are cheap enough to be commercially available?

You can make them out of asteroid bits but I'm not looking for just asteroids. I'm thinking more...synthetic. You can use asteroid bits, I just want a more synthetic moon feel, like a comic moon.

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  • $\begingroup$ This will likely close as being primarily opinion based. No one knows how long it will take to develop this much, and there aren't exactly developing fields like this to observe, so people will be left to speculate. $\endgroup$ – Zxyrra Nov 23 '16 at 3:39
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    $\begingroup$ We've had artificial moons since the 1960s. They are called "satellites"... $\endgroup$ – John Feltz Nov 23 '16 at 3:45
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    $\begingroup$ Do satellites look like moons? $\endgroup$ – John Meow Nov 23 '16 at 3:46
  • $\begingroup$ What is a moon? Note that even in a post scarcity society like Star Trek, they don't do anything like this. You don't need just the engineering capacity, but a background that justifies it. Why build a moon rather than a space station? $\endgroup$ – Brythan Nov 23 '16 at 4:06
  • $\begingroup$ John, you accepted an answer twelve minutes after posting your question. Remember this site is seen worldwide. It takes 24 hours for everybody to have a look at the questions. This is a courtesy. $\endgroup$ – a4android Nov 23 '16 at 4:51
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Using the Kardashev Scale: 3600 Years from now

The Kardashev Scale categorizes civilizations by how much energy they can harness and control. At Level II, a civ can harness the total power of its native star through a giant space structure - which, you could reason, is about the place, engineeringwise, it would need to be in to be able to build a moon.

Estimates conclude that we will be a Type I in around 200 years - and a Type II around 3400 years from then - so you could argue that about 3600 years from now, we will be able to construct moons at will, with ease.

Why the answer is not 50 years from now:

  • No reputable source supports technological growth at this extreme rate
  • It takes thousands of years to form planets and moons with high-speed natural collisions so 50 years is thousands of years too short, even if we had the tech
  • We do not have the means to harvest mass on this scale - ex. "blowing up Mars" is not something we can do now, nor will we be able to do, for centuries
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  • $\begingroup$ Woow I'm disappointed $\endgroup$ – MolbOrg Nov 23 '16 at 5:48
  • $\begingroup$ @MolbOrg In me or the human race lol $\endgroup$ – Zxyrra Nov 23 '16 at 6:06
  • $\begingroup$ I have no doubt about humankind, it is my God. U part of humanity, I part of humanity so we are partially gods, but answer is soso, but it is a part of humanity god thinking ways so my first comment probably was moment of my weakness)) $\endgroup$ – MolbOrg Nov 23 '16 at 7:45
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50 years*

I'm the scientists.

Technology itself is not so complex, just stack piles of dirt on top of each other. It is that simply and same way the pointless use of matter. You could do billions of space habitats from that mater for people to live, and wasting all those matter is almost a crime.

But if you wish comic look you have to address that question to designers, and if you do wish just a look, not the mass then you even do not need a mad scientist for that. Just make a big sphere and cover it with dust and purchase moon look design.

If you need moon look and moon mass then Mars can be used to make about 8 moons.

If you ok with moon look, and moon gravity, but 2-10 times bigger size - shell world is a way to go.

Energy and technology

Kardashev Scale is useless in defining technologies and predicting energy possession vs time. It just says now you a Lieutenant (T1), now you a First Lieutenant (T2), now you a Captain (T3) - but it depends on you and your efforts to get those rank, yes a bit of luck helps, but mostly it is efforts.

Estimating possible power production based on previous earth energy production grow is pointless because of space. On earth, there is one earth related coefficient of that grow, in space it is another space related coefficient.

On earth you have to move million's tonnes of matter to make a dam, to produce few GW of power. (about 30-40 million tonnes for this one Oroville Dam youtube docu about dam's , Oroville Dam, wiki or List of the tallest dams in United States and it produces only 890MW (not its main purpose)) A bit more proper example Sayano–Shushenskaya Dam It was used 10 million cubic meters of concrete, it is about same 30 million tonnes of concrete, and it produces 6.4 GW of power.

6.4 GW it is about 3400 x 3400 m square at 40% efficiency at L1 (Lagrange point). If mass of construction per square meter is about 1kg, difference is not exciting just 3 times less of materials, not exciting because even launching that from moon costs a significant amount of energy. But nice thing about microgravity is that construction can be very light weight, because they do not need same construction strength they need in a gravity well. Thin reflective foil can be used to focus the sun light and it can be with minimal construction strength (some king of light weight frame) 4600 tonnes of foil to focus the light - and that is 10000 less materials to generate same amount of energy.

Concrete is not for free is also energy expensive process to make it.

Escape velocity from the Moon is 2.38 km/s, and to launch let say those 5000 tonnes of materials we need significant amount of energy, but with 6.4GW we can do that each 35 minutes. It is fair to say that we need about same energy to produce the foil and frame, same to collect ore on the Moon, same for just in case(for misc needs, efficiency of launch system, energy to extend its capabilities etc).

So basically the system can grow each 2 hours in 2 times. After 24hours it can produce 4096 times more energy than original system. So The system, even with energy launch costs from the moon have very high grow rate.

On earth, we just can't scale things so fast, because all solutions here are not mass efficient, and there is very limited space to grow the systems, and there no need in such fast grow - not real places to use it for the cost it has.

A situation where we need to create a Moon is different, because we need a lot of energy for different processes involved, and it makes sense to grow energy production as fast as we can to achieve needed energy generation level.

SpaceX reusable launch cost is expected to be 140'000 \$ per tonne, it is about 1'400'000 kWh energy wise(0.1\$ per kWh) or 5.04e+12 J per tonne. And the 5000-tonne construction with 6.4GW energy generation may grow 2 times in about 45 days.
No launch loop, no space elevators, but just a technology we expect to have in 10years. 45 days! In Space! by a rocket! compare it to the time it was needed to build both dam's. 15 years for Sayano–Shushenskaya Dam, 7 years for Oroville Dam.

  • I didn't multiply energy by 4 as I did for nonrocket launch system, because above energy is a fraction of energy which is needed for the rocket, about 0.23% of it, not significant.

Uvaga-Achtung-Warning-Внимание

Space and Earth are way way much different than people usually think, for the cost of launching 10000 (actually less) new Martians to the Mars, we can actually be a type 1 civilization in 3.5 years, with SpaceX BF class rocket.

Type 2 - in 6.9 years.

Type 2 not so simple, some technology improvements are needed, but type 1 is easy, no new technologies are needed.

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  • $\begingroup$ Blowing up Mars (ignoring the fact that this will be impossible in 50 years, and that even if somehow we could, an average scientist would have governments and budget in his way) to make 8 pseudo-moons is not the same as "cheap enough to be commercially available" so this does not answer OP's Q $\endgroup$ – Zxyrra Nov 23 '16 at 7:48
  • $\begingroup$ @Zxyrra I provided links to description of technologies op needs for the project, both links in first section of the answer are strongly related. They are not something too sophisticated. Shell world and blow Jupiter and make 25 thousand moons. Moon is pretty significant space body, it never be dirt cheap, specially if it just passive dirt. Really I recommend both links. As about KS, efficiency of energy usage is a big deal actually, in some times it is limited by physics in some we are way below that limit, but more advanced then we were. $\endgroup$ – MolbOrg Nov 23 '16 at 8:10
  • $\begingroup$ T1 we can be 10 years later just with tech we have today, just because we will to use rockets more efficient, and our efforts more efficient. T2 is a bit more of challenge, same problem as with A supercomputer around the sun I focused on that cheap thing, I knew it will be a issue. $\endgroup$ – MolbOrg Nov 23 '16 at 8:10
  • $\begingroup$ Moving rockets aside, being able to harvest enough material to make a moon or even assemble it in 50 years is unprecedented. $\endgroup$ – Zxyrra Nov 23 '16 at 8:13
  • $\begingroup$ @Zxyrra read link I have provided, watch a video. $\endgroup$ – MolbOrg Nov 23 '16 at 8:15

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