# What's the cheapest way to bring something from LEO back to earth? **URL:** \ **Category:** Factual Questions\ **Created:** [November 3, 2019, 6:21am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939 "2019-11-03T06:21:37Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\ **Post date:** [November 3, 2019, 6:21am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/1 "2019-11-03T06:21:37Z")
Assume we manage to tow an asteroid from outer space into LEO and we establish a robotic mining colony there to extract platinum and nickel. How do we get the minerals from LEO down to earth affordably while also not turning them into high velocity projectile bombs? Do we currently have theoretical plans for how to bring large amounts of material down from LEO in an economical manner that allows us to recover the material and integrate it into our supply chains? ---
**Author:** ![SamuelA](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@SamuelA](https://boards.straightdope.com/u/SamuelA)\ **Post date:** [November 3, 2019, 6:31am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/2 "2019-11-03T06:31:16Z")
Well, if it’s metal, it doesn’t need a soft landing. In principle you could build disposable heat shields and have the metal chunks make controlled craters in a target zone on land. In reality, you mentioned a key precondition. A _robotic mining colony_. Really sophisticated robots, right? So advanced that the same software and hardware backend allows for robots that build other robots on earth, right? This makes the robots dirt cheap, right? Well, why not have the same robots mine for materials on earth? They could work in deep mines, mines that are too hot for humans and full of safety hazards that clever robots have no trouble with. Some metals, such as platinum and iridium, are extremely rare on earth. In that case, you could build large shuttle rockets, similar to the SpaceX BFR - robots would build them - and soft land a few dozen tons of metal per round-trip. Everything else, robots would mine on earth. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [November 3, 2019, 6:38am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/3 "2019-11-03T06:38:44Z")
Heat shields and parachutes have worked well and were inexpensive. Big chunks of metal don’t need a very soft landing or that much heat protection so the method should be less expensive than when sending humans back to earth. ---
**Author:** ![SamuelA](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@SamuelA](https://boards.straightdope.com/u/SamuelA)\ **Post date:** [November 3, 2019, 2:51pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/4 "2019-11-03T14:51:19Z")
> [@TriPolar](#): > > Heat shields and parachutes have worked well and were inexpensive. Big chunks of metal don’t need a very soft landing or that much heat protection so the method should be less expensive than when sending humans back to earth. Right. And one cost savings is to leave the parachutes off. Let the whole assembly hit a higher terminal velocity relative to it’s aerodynamic profile. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [November 3, 2019, 3:10pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/5 "2019-11-03T15:10:57Z")
[**Maxim 11:**](https://tvtropes.org/pmwiki/pmwiki.php/Quotes/SchlockMercenary) Everything is air-droppable at least once. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [November 3, 2019, 3:20pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/6 "2019-11-03T15:20:40Z")
> [@Shalmanese](#): > > …we establish a robotic mining colony there to extract platinum and nickel. How do we get the minerals from LEO down to earth… Not sure I understand the question completely. Minerals and Ores both have the sought metal in them but the Ores have them in concentrations economic for extractions. Also, you say that the robotic colony **extracts** the metals. If they have already extracted the metal, why wouldn’t they just send the metal to earth ? Why are they sending the minerals ? Also, I think while robotics maybe advanced enough to make this look reasonable, mining and metallurgy is very primitive to do any sort of extraction in space. Most of the ore processing on earth relies on gravity separation, water washing, heating things up or reducing them with other chemicals - things that you cannot do in space based on today’s technology. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [November 3, 2019, 3:27pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/7 "2019-11-03T15:27:28Z")
> [@Shalmanese](#): > > A…tow an asteroid from outer space into LEO and we establish a robotic mining colony there to extract platinum and nickel… If we had the technology to do these things, the last step would be trivial by comparison. Reentry (or entry) from LEO just takes a tiny bit of delta-V, and heat shield and structural integrity to make sure it doesn’t burn up or break up during reentry. Actually it won’t even matter if they broke up, as long as they don’t burn up. Just designate a remote desert as a target area, and drop lumps of metal onto it. It’ll get mixed up sand and dirt, but we’ve got robots that can refine metals, right? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 3, 2019, 6:03pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/8 "2019-11-03T18:03:29Z")
Plus, of course, a big part of why you’d want to mine asteroids is to get the raw materials to make more space infrastructure. Why go to the trouble of sending it down here at all, when it’s more useful up there? ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [November 3, 2019, 6:34pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/9 "2019-11-03T18:34:01Z")
> [@Chronos](#): > > Plus, of course, a big part of why you’d want to mine asteroids is to get the raw materials to make more space infrastructure. Why go to the trouble of sending it down here at all, when it’s more useful up there? Some metals are going to be more valuable on Earth than in space. For example, relative to Earth, asteroids have more platinum-group metals and there’s likely to be very limited use for them in constructing space habitats and other infrustructure. But there are many industrial uses for them and probably would be more if their prices come down somewhat. The factories that use those metals are on Earth, not in space. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [November 3, 2019, 7:00pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/10 "2019-11-03T19:00:48Z")
> [@SamuelA](#): > > Right. And one cost savings is to leave the parachutes off. Let the whole assembly hit a higher terminal velocity relative to it’s aerodynamic profile. You need some control or a heavier heat shield to keep it from staying at hypersonic speeds on the way down. And the result of a misplaced landing or failure to reduce velocity creates enormous economical and safety risks. Parachutes only help to mitigate those risks. Cost was the object here, assuming we don’t just want massive fireballs falling out of the sky then heat shields and parachutes are the way to go. For a higher cost the material could be shaped into a controllable aerodynamic shape where the landing spot can be more selective, even if it doesn’t need a soft landing like a human craft. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [November 3, 2019, 8:31pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/11 "2019-11-03T20:31:19Z")
> [@SamuelA](#): > > Right. And one cost savings is to leave the parachutes off. Let the whole assembly hit a higher terminal velocity relative to it’s aerodynamic profile. I expect that the cost of the parachutes is less than the value of the metal that would be burned up without one. If so, the parachutes are a good investment. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [November 3, 2019, 10:15pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/12 "2019-11-03T22:15:35Z")
> [@Tim\_T-Bonham.net](#): > > I expect that the cost of the parachutes is less than the value of the metal that would be burned up without one. If so, the parachutes are a good investment. That would probably depend on where the parachutes come from. If they have to be shipped up from Earth, then the cost of launches could make them more expensive. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [November 4, 2019, 12:07am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/13 "2019-11-04T00:07:08Z")
If the asteroids have water or some such suitable gas or fluid, you can use it to actively cool the Heat shield of the vessel bringing it. Similar cooling techniques are used in cooling gas turbines blades in +2000F temperatures. The surface is made porous by drilling holes and the cooling fluid is made to flow outward through these holes (pores). > **[Turbine blade | Cooling](https://en.m.wikipedia.org/wiki/Turbine_blade#Cooling)** > > At a constant pressure ratio, thermal efficiency of the engine increases as the turbine entry temperature (TET) increases. However, high temperatures can damage the turbine, as the blades are under large centrifugal stresses and materials are weaker at high temperature. So, turbine blade cooling is essential for the first stages but since the gas temperature drops through each stage it is not required for later stages such as in the low pressure turbine or a power turbine. Current modern turb ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [November 4, 2019, 12:18am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/14 "2019-11-04T00:18:43Z")
Bring it back on SpaceX Starships, which would presumably be coming back with 50 ton load capacity. Most of the time I would imagine those rockets going up full and coming back empty, so why not load them with gold and platinum first? if they fly 10 times a month, you could bring back 500 tons of material per month. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 4, 2019, 2:40am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/15 "2019-11-04T02:40:16Z")
Even if you’re sending up Starships anyway, it’ll still be cheaper to just crater the metal than to bring it back gently. Whatever system the Starship uses for landings, it won’t be designed for that kind of cargo load. ---
**Author:** ![runningdude](https://avatars.discourse-cdn.com/v4/letter/r/e9c0ed/32.png) [@runningdude](https://boards.straightdope.com/u/runningdude)\ **Post date:** [November 4, 2019, 3:02am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/16 "2019-11-04T03:02:57Z")
> [@Sam\_Stone](#): > > you could bring back 500 tons of material per month. That sounds like a big number, but it is very small compared to the size of most industries. The US steel industry alone, for instance, produces 7000 tons a month. The Chinese steel produces 1,000,000 tons a month. Space metals would require millions of tons monthly to be economically viable. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [November 4, 2019, 3:24am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/17 "2019-11-04T03:24:10Z")
What about all that space-mined helium? Seems like you would want to bring the tanks back in one piece. ---
**Author:** ![Gray\_Ghost](https://avatars.discourse-cdn.com/v4/letter/g/c0e974/32.png) [@Gray\_Ghost](https://boards.straightdope.com/u/Gray_Ghost)\ **Post date:** [November 4, 2019, 3:50am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/18 "2019-11-04T03:50:10Z")
> [@runningdude](#): > > That sounds like a big number, but it is very small compared to the size of most industries. The US steel industry alone, for instance, produces 7000 tons a month. The Chinese steel produces 1,000,000 tons a month. > > Space metals would require millions of tons monthly to be economically viable. 2017 global production platinum: 8 million ounces. [The Biggest Platinum Metal Producers](https://www.thebalance.com/the-10-biggest-platinum-producers-2339736) Or 400 tons, at 10 troy oz to the pound. For gold, it’s roughly 2500-3000 tonnes a year. [How Much Gold Has Been Mined? | World Gold Council](https://www.gold.org/about-gold/gold-supply/gold-mining/how-much-gold) Neodymium is a bit more common, with a mine in Australia producing around 10,500 tonnes a year. [https://investingnews.com/daily/resource-investing/critical-metals-investing/rare-earth-investing/rare-earth-producing-countries/](https://investingnews.com/daily/resource-investing/critical-metals-investing/rare-earth-investing/rare-earth-producing-countries/) This assumes we don’t find a diamond asteroid, perhaps as a chunk of some gas giant core. Edit, the point is, if certain minerals are more readily found in their pure states in space, being restricted to 50 tons at a time may not be a dealbreaker. What would a large deposit of Helium-3 go for? ---
**Author:** ![Gray\_Ghost](https://avatars.discourse-cdn.com/v4/letter/g/c0e974/32.png) [@Gray\_Ghost](https://boards.straightdope.com/u/Gray_Ghost)\ **Post date:** [November 4, 2019, 4:12am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/19 "2019-11-04T04:12:32Z")
Oh, and cheapest way to deorbit the stuff is probably to process some of it, and expel the slag as a reaction drive to deorbit the ore. Spin a silica blanket around the product. Maybe deploy some high drag apparatus that deploys after reentry? I was thinking of solid helical fins on the payload, so the payload could spin down like a seed pod? ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [November 4, 2019, 5:18am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/20 "2019-11-04T05:18:24Z")
> [@am77494](#): > > If the asteroids have water or some such suitable gas or fluid, you can use it to actively cool the Heat shield of the vessel bringing it. Only undiffrentiated asteroids would have any meaningful water. Only nickle-iron core fragments from blasted diffrentiated asteroids would have reasonably enriched sidreophile elements. (Undiffrentiated asteroids would have higher concentrations than in a random handful of Earth soil, but very unlikely enough of a concentration to make landing the thing on Earth profitable. But then again, you can almost 100% likely say the same about core chunks. It would probably always be cheaper and easier to make mines multiple miles deep in the Earth’s crust.) [Next page](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939.md?page=2)