Quote from: spacenut on 06/17/2018 01:37 amWhat we may need from space is more raw minerals like aluminum, iron, titanium, cobalt, copper, zinc, lead, etc.We are not in short supply of any of those on Earth. Aluminum is 8% of the Earth's crust, iron is the most abundant, titanium is the 9th most abundant...There is likely no market on Earth for raw material from space. Not unless the price was close to zero, which means no one is making money in space mining raw material.QuoteMany of these minerals may have to be mined on the moon, Mars, or the asteroids to keep up with depletion of earths mineral resources.Again, we're not on a path to mineral depletion here on Earth. Even "rare-earth elements" are not rare, just hard to extract.No, the predominant market for raw material mined in space will be for consumption IN space, and it will be used for building the equipment and dwellings we'll need to expand humanity out into space, since it's too expensive to ship all that mass up from the surface of Earth.QuoteOnce mined, they may be smelted and processed into finished goods in O'Neil cylinders or on the moon or Mars. From what I've read about the processing of raw material here on Earth, you won't want to do it in a human-habitable structure due to all the poisonous chemicals that are used when processing ore here on Earth.However space has some advantages that could be used to develop new ways to process ore in space, such as zero gravity and a constant source of heat (and cold). First we need a source of raw material though...
What we may need from space is more raw minerals like aluminum, iron, titanium, cobalt, copper, zinc, lead, etc.
Many of these minerals may have to be mined on the moon, Mars, or the asteroids to keep up with depletion of earths mineral resources.
Once mined, they may be smelted and processed into finished goods in O'Neil cylinders or on the moon or Mars.
Quote from: johnfwhitesell on 06/16/2018 07:36 pmQuote from: meekGee on 06/16/2018 06:37 pmMeanwhile what exactly is the plan to build in LEO or on the moon? Factories that do what?-Make rocket fuel on the moon-Make structural elements on the moon-Produce solar panels or mine materials in spaceRight. So two things:Technically, to reduce this to practice, what's the path? You need ISRU, right? Non-existent in orbit, and cryogenic, maybe, sparsely, in craters on the lunar pole.Mine material in space? What material?Financially, who'll buy the product? I mean if the goal is to make money, and the people as you say are on Earth, who wants structural elements that are made on the moon?
Quote from: meekGee on 06/16/2018 06:37 pmMeanwhile what exactly is the plan to build in LEO or on the moon? Factories that do what?-Make rocket fuel on the moon-Make structural elements on the moon-Produce solar panels or mine materials in space
Meanwhile what exactly is the plan to build in LEO or on the moon? Factories that do what?
Quote from: meekGee on 06/16/2018 07:50 pmQuote from: johnfwhitesell on 06/16/2018 07:36 pmQuote from: meekGee on 06/16/2018 06:37 pmMeanwhile what exactly is the plan to build in LEO or on the moon? Factories that do what?-Make rocket fuel on the moon-Make structural elements on the moon-Produce solar panels or mine materials in spaceRight. So two things:Technically, to reduce this to practice, what's the path? You need ISRU, right? Non-existent in orbit, and cryogenic, maybe, sparsely, in craters on the lunar pole.Mine material in space? What material?Financially, who'll buy the product? I mean if the goal is to make money, and the people as you say are on Earth, who wants structural elements that are made on the moon?It's sequential. First you use lunar fuel to take satellites from LEO to GEO, saving mass. Then you start to replace the mass of satellites with extraterrestrial materials. Then they get more advanced until you can do things like space solar power. ULA seems to think there is promise in microwave power transmission. My personal opinion is that orbital datacenters are a much more promising then transmitting power to earth. Datacenters are already consuming hundreds of terrawatts of electricity a year and that's expected to grow drastically. If orbital datacenters were buying 3 PWh of electricity at 1 cent/kWh that would be a 30 billion dollar electricity market in orbit. That is the kind of market that could get a moon colony going.
It's sequential. First you use lunar fuel to take satellites from LEO to GEO, saving mass. Then you start to replace the mass of satellites with extraterrestrial materials. Then they get more advanced until you can do things like space solar power. ULA seems to think there is promise in microwave power transmission.
For kicks, if you had a prefect radiator, and were rejecting heat at 100C, you'd need 1000 m2 for a single lonely MWatt.
Quote from: meekGee on 06/17/2018 05:48 pmFor kicks, if you had a prefect radiator, and were rejecting heat at 100C, you'd need 1000 m2 for a single lonely MWatt. In order to generation that MW of heat you would need 1 MW of electrical generation. With a solar panel efficiency of 25% and a solar flux of 1.3 kW per m^2 that requires 3000 square meters of solar array. The arrays only receive light on one side so it would make sense to pick a material with a high emissivity for the other side. IIRC emissivity is equivalent to light absorption so it would make sense to make the solar panels have emissivity as close to the absorption efficiency as possible. So let's say 95% on the radiation side, 30% on the solar panel side. So that is 1.2 MW of heat to ditch (200 kW is the radiation heat on the panels) emitted through 6000 square meters with an average emissivity of 67%. Based on those assumptions, the equilibrium temperature would be 270 Kelvin, just shy of freezing. This is ignoring the effects of earth shadow which would require a larger array and thus lower the equilibrium temperature. This is also ignoring the heat distribution problem, which would likely be the much more difficult challenge.
You're going to need to break down your assumptions.One ton of fuel in LEO may cost $10K (if you believe P2P), $300K if you assume $50M per BFR launch.
Not so fast... When your array is that big, its easy (relatively) to conduct electricity inwards... But much harder to pump heat outwards.
Quote from: meekGee on 06/18/2018 04:03 amNot so fast... When your array is that big, its easy (relatively) to conduct electricity inwards... But much harder to pump heat outwards.It feels like you are playing "gotcha!" here after I just finished saying that I thought that was the more significant problem. To repeat myself, I think the heat distribution is the more significant concern. The reason I talked about the heat exchange was because that was what you were talking about.In regards to the distribution, I am even less fluent in thermal conduction then in radiation so it's more difficult for me to say. However I will note again that I think datacenters would be in LEO, where they would need considerably larger arrays for the necessary power due to the shadow. This means that the equilibrium temperature for the radiation would be even lower. This would allow for an even larger gradient of temperature between a computer chip kept at temperatures above 0 Celsius and the radiator panels. It seems to me that if there is a temperature gradient of around 30 degrees or so, it should be possible to design the system to achieve the task with passive thermal conduction. It may even be possible to take advantage of the heat gradient for a small amount of energy reclamation. If you are apt with thermal conduction calculations and would like to explain things better I would welcome the insight. But if it's just a gut thing, 100 meters of distance with a 30 degree difference or so seems pretty reasonable to me. Maybe the centers would be hotter then earth, maybe colder, but it feels like it would be in the ballpark of earth.
My bad.... Reading too fast on the phone. Leaving orig intact as a lesson to my future self.
Quote from: johnfwhitesell on 06/18/2018 04:49 amQuote from: meekGee on 06/18/2018 04:03 amNot so fast... When your array is that big, its easy (relatively) to conduct electricity inwards... But much harder to pump heat outwards.It feels like you are playing "gotcha!" here after I just finished saying that I thought that was the more significant problem. To repeat myself, I think the heat distribution is the more significant concern. The reason I talked about the heat exchange was because that was what you were talking about.In regards to the distribution, I am even less fluent in thermal conduction then in radiation so it's more difficult for me to say. However I will note again that I think datacenters would be in LEO, where they would need considerably larger arrays for the necessary power due to the shadow. This means that the equilibrium temperature for the radiation would be even lower. This would allow for an even larger gradient of temperature between a computer chip kept at temperatures above 0 Celsius and the radiator panels. It seems to me that if there is a temperature gradient of around 30 degrees or so, it should be possible to design the system to achieve the task with passive thermal conduction. It may even be possible to take advantage of the heat gradient for a small amount of energy reclamation. If you are apt with thermal conduction calculations and would like to explain things better I would welcome the insight. But if it's just a gut thing, 100 meters of distance with a 30 degree difference or so seems pretty reasonable to me. Maybe the centers would be hotter then earth, maybe colder, but it feels like it would be in the ballpark of earth.A copper conductor to move 1 MW of power 100 meters under 30 dT will need 0.833 m^2 area and mass 749,700 kg.Even flowing water is 100x less area and 1000x less mass than copper conductors, so a pumped water system would be more like 1000 kg, plus the mass of the pump.And in microgravity it's possible to build phase change heat transfer systems that are far better than passive conduction or water flow, both per area and per mass. I'm not sure exactly how much better, but IIRC it's in the 1,000s to 10,000s of times, which would put a 1 MW system in the 100s of kg. Both phase change and water flow mean messing with fluids though, which could be a pain.
The ISS has one. Lightweight, it is not. Here's why.You calculate above the theoretical weight of a linear system, or rather estimate it by using "1000x lighter" type multipliers.Even if that calculation was true, you have to distribute heat over an area. The lateral conductivity of thin films is very low. So you need to drag your heat distribution tubing all over the place to cover almost literally every square inch (or, use a thicker and conductive material for the radiator).Either way, a problem. If you have thin tubing, pumping requires higher pressurres. MMOD becomes an issue.
-----This is getting too technical and OT.The root cause is that you need to build terrestrial-scale infrastructure, and there isn't a way to make that happen gradually and organically - not even with a Trillion dollars.Industry needs to grow while being profitable. That's what differentiates a business plan from a lofty goal.I would love for Bezos to show his plan. There is no reason to keep it a secret, as SpaceX has shown. I suspect however that there isn't one.He'll go for tourism if that proves profitable, and maybe the aforementioned oneWeb play once New Glen flies.
Quote from: meekGee on 06/18/2018 01:33 pmThe ISS has one. Lightweight, it is not. Here's why.You calculate above the theoretical weight of a linear system, or rather estimate it by using "1000x lighter" type multipliers.Even if that calculation was true, you have to distribute heat over an area. The lateral conductivity of thin films is very low. So you need to drag your heat distribution tubing all over the place to cover almost literally every square inch (or, use a thicker and conductive material for the radiator).Either way, a problem. If you have thin tubing, pumping requires higher pressurres. MMOD becomes an issue.The ISS radiator systems have a deployed full system areal density of 8.8 kg/m^2, so a 1000 m^2 MW class array would be 8800 kg, which is not entirely impractical.Quote-----This is getting too technical and OT.The root cause is that you need to build terrestrial-scale infrastructure, and there isn't a way to make that happen gradually and organically - not even with a Trillion dollars.Industry needs to grow while being profitable. That's what differentiates a business plan from a lofty goal.I would love for Bezos to show his plan. There is no reason to keep it a secret, as SpaceX has shown. I suspect however that there isn't one.He'll go for tourism if that proves profitable, and maybe the aforementioned oneWeb play once New Glen flies.Agreed. I don't see a killer app for industry in LEO or cislunar space, yet.But I think tourism and comms can lay the infrastructure foundations, and then perhaps industry will follow.
This is getting too technical and OT.The root cause is that you need to build terrestrial-scale infrastructure, and there isn't a way to make that happen gradually and organically - not even with a Trillion dollars.
Neither party has even mentioned these, but they seem like a potential booming industry in LEO. And one that likely will be cheaper to service and upgrade than to replace. I'm looking forward to watching that shake out.
Incidentally, is there a term like "cislunar" for "between LEO and cislunar, inclusive"? I can't think of one. Cisterra?