# 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:** 2
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [November 4, 2019, 6:15am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/21 "2019-11-04T06:15:30Z")
I think we’re overanalyzing. Built the rentry vehicles out of the core material with very high surface area to weight. Air resistance to slow the object, spread over a large area, means much less heat and less loss. Note the SpaceX boosters fall from a great height and only have to use their rockets to slow down when they are close to landing, since they are essentially empty cans with a high drag compared to weight, so a low terminal velocity. heck, build them shaped like giant windmills so they float to ground at a moderate speed spinning like a maple seed. ---
**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, 6:27am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/22 "2019-11-04T06:27:04Z")
> [@Gray\_Ghost](#): > > What would a large deposit of Helium-3 go for? The price on Earth is about $12000 per gram right now, and it’s not getting any cheaper. Obviously unloading a _large_ deposit would depress the price by a significant factor. ---
**Author:** ![RioRico](https://avatars.discourse-cdn.com/v4/letter/r/f04885/32.png) [@RioRico](https://boards.straightdope.com/u/RioRico)\ **Post date:** [November 4, 2019, 6:50am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/23 "2019-11-04T06:50:48Z")
> [@Shalmanese](#): > > 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. Who thinks Belters will allow groundhogs to grab their resources? If they do, wouldn’t the tech implicit in asteroid-towing also be sufficient to assure soft landings in a gravity well? Easier, why not fashion vast parachutes and massive heat shields from asteroid detritus? Use the rest of the detritus to fabricate outer-space infrastructure. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [November 4, 2019, 10:40am UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/24 "2019-11-04T10:40:31Z")
> [@RioRico](#): > > Who thinks Belters will allow groundhogs to grab their resources? Who are these Belters of which you speak? > [@](#): > > If they do, wouldn’t the tech implicit in asteroid-towing also be sufficient to assure soft landings in a gravity well? Not at all. It’s much easier to push things around in orbit than to soft land on a high gravity planet. > [@](#): > > Easier, why not fashion vast parachutes and massive heat shields from asteroid detritus? Parachutes are usually made of nylon although probably could be made of other polymers. How do you easily make polymers from the stuff found in asteroids? Some asteroids have lots of carbon, but it’s not in the form of monomers. > [@](#): > > Use the rest of the detritus to fabricate outer-space infrastructure. Detritus is stuff that you can’t use for anything except reaction mass. Anything you can use to make space infrastructure is not detritus. Iron, aluminum, copper and some other metals are useful for that. They’re far more valuable in space than they are on Earth. The only metals you want to bring down to Earth are ones that aren’t very useful for infrastructure but are valuable on Earth. ---
**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, 12:22pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/25 "2019-11-04T12:22:11Z")
“Belters” is a common science fiction term (especially in Niven’s Known Space series) for humans who live in the asteroid belt, with an industry built primarily around mining. “Groundhogs” is presumably derogatory slang for humans who live on (and probably have never left) Earth. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [November 4, 2019, 12:58pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/26 "2019-11-04T12:58:16Z")
Here’s a whacko idea for slowing down items dropped from LEO without using heat shields or parachutes. Laser Propulsion. I worked on Arthur Kantrowitz’ plan to send things up from the Earth (actually, he suggested elevated spots, like plateaus and mountaintops) to LEO by using a series of pulses from ground-based lasers. This was NOT using light pressure – the light pulse would evaporate a metered amount of ablative material (ice, ideally), and the succeeding pulse would feed energy into it via inverse bremstrahlung that would expand it and provide oomph, something called a _Laser Sustained Detonation_ wave\*. If it works going up, it would work as well going down. Even better, arguably, because you only have to slow the descent, not push the whole load against gravity. The great part is that it’s basically a rocket that doesn’t use explosive and dangerous materials, and all the heavy parts get to stay on the ground. The problem is that you have to be extremely careful in your aiming. And you use an awesome amount of power, since the lasers involved aren’t very efficient. But they might be able to fix that. The idea of ground-to-orbit laser propulsion of this sort has been used in science fiction for decades – Jerry Pournelle’s _High Justice_; Michel Kube-McDowell’s _The Quiet Pools_, Dean Ing’s _The Big Lifters_, and my own _The Flight of the Hans Pfaall_. > **[Laser propulsion](https://en.wikipedia.org/wiki/Laser_propulsion)** > > Laser propulsion is a form of beam-powered propulsion where the energy source is a remote (usually ground-based) laser system and separate from the reaction mass. This form of propulsion differs from a conventional chemical rocket where both energy and reaction mass come from the solid or liquid propellants carried on board the vehicle. > The basic concepts underlying a photon-propelled "sail" propulsion system were developed by Eugene Sanger and the Hungarian physicist György Marx. Propulsion co... \*I’m sure the acronym LSD is pure purely fortuitous. ---
**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 4, 2019, 1:00pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/27 "2019-11-04T13:00:36Z")
> [@dtilque](#): > > Parachutes are usually made of nylon although probably could be made of other polymers. How do you easily make polymers from the stuff found in asteroids? Some asteroids have lots of carbon, but it’s not in the form of monomers. Glass can be spun into fibers. That includes all sorts of silicate compounds. Bright S (silicacaseous) asteroids are the asteroids closest to earth. ETA: Silicates can also be used for heat shields. ---
**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, 3:35pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/28 "2019-11-04T15:35:30Z")
> [@CalMeacham](#): > > Here’s a whacko idea for slowing down items dropped from LEO without using heat shields or parachutes. > > Laser Propulsion. > > I worked on Arthur Kantrowitz’ plan to send things up from the Earth (actually, he suggested elevated spots, like plateaus and mountaintops) to LEO by using a series of pulses from ground-based lasers. This was NOT using light pressure – the light pulse would evaporate a metered amount of ablative material (ice, ideally), and the succeeding pulse would feed energy into it via inverse bremstrahlung that would expand it and provide oomph, something called a _Laser Sustained Detonation_ wave\*… I’ve seen the videos of the small rigs using the tech to climb a tower or wire. CRACK-CRACK-CRACK-CRACK. How do they address the eye safety issues and what’s the largest size they ever lifted with the tech? ---
**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 4, 2019, 3:51pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/29 "2019-11-04T15:51:07Z")
> [@CalMeacham](#): > > I worked on Arthur Kantrowitz’ plan to send things up from the Earth (actually, he suggested elevated spots, like plateaus and mountaintops)… That’s why we need to buy Venezuela now with it’s value bottomed out. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [November 4, 2019, 4:32pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/30 "2019-11-04T16:32:07Z")
> [@DPRK](#): > > The price on Earth is about $12000 per gram right now, and it’s not getting any cheaper. Obviously unloading a _large_ deposit would depress the price by a significant factor. I’m not sure how you can have a large deposit of He-3. It’s a noble gas with a boiling point of 3.2 Kelvin. There’s only so much of it that can be trapped in rock. A surface exposed to the solar wind accumulates He-3 but we’re talking tens of ppb (parts per billion). Meaning you need to process a thousand tons of regolith to get maybe one ounce (30 grams) of He-3. ---
**Author:** ![Isosleepy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/isosleepy/32/479_2.png) [@Isosleepy](https://boards.straightdope.com/u/Isosleepy)\ **Post date:** [November 4, 2019, 5:03pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/31 "2019-11-04T17:03:16Z")
> [@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 Missing some zeroes there. Like 3. ---
**Author:** ![PastTense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pasttense/32/14550_2.png) [@PastTense](https://boards.straightdope.com/u/PastTense)\ **Post date:** [November 4, 2019, 5:29pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/32 "2019-11-04T17:29:06Z")
Here are statistics on global steel production: > **[List of countries by steel production](https://en.wikipedia.org/wiki/List_of_countries_by_steel_production)** > > This article summarizes the world steel production by country. > In 2020, total world crude steel production was 1877.5 million tonnes (Mt). The biggest steel producing country is currently China, which accounted for 57% of world steel production in 2020. In 2020, China became the first country to produce over one billion tons of steel. In 2008, 2009, 2015 and 2016 output fell in the majority of steel-producing countries as a result of the global recession. In 2010 and 2017, it started to rise ... ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [November 4, 2019, 5:30pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/33 "2019-11-04T17:30:18Z")
> [@Gray\_Ghost](#): > > I’ve seen the videos of the small rigs using the tech to climb a tower or wire. CRACK-CRACK-CRACK-CRACK. How do they address the eye safety issues and what’s the largest size they ever lifted with the tech? We used to zap dime-sized pieces of acetal plastic in our lab. as far as I know, the biggest item that’s been lifted “in the wild” is one of Leik Myrabo’s “Apollo Lightcraft”, which are about the size of a volleyball and probably weigh about a pound. He shot them up into the sky using a pulsed carbon dioxide laser at White Sands. When they shut off the laser and it fell, they caught it in a net. Of course, that’s only for testing – they envisioned sending up a three-man crew or equivalent, eventually. The lightcraft differed from the ablation method we were using in that there was no material to be ablated – the bottom part of the craft and a special ring around the outside were highly polished mirrors that focused the light onto a sample of air and used the ambient atmosphere as the material heated. Obviously, this would only work as long as the atmosphere held out. The idea was to get the craft moving to the necessary velocity while still in the atmosphere. Since you can continuously feed in energy, it’s not like Jules Verne’s cannon in _From the Earth to the Moon_. You don’t need one big acceleration at the start, squishing your payload into jelly. According to [Leik Myrabo - Wikipedia](https://en.wikipedia.org/wiki/Leik_Myrabo), the record flight was 10.5 seconds and achieving a height of 72 meters (236 feet). > **[Lightcraft](https://en.wikipedia.org/wiki/Lightcraft)** > > The Lightcraft is a space- or air-vehicle driven by beam-powered propulsion, the energy source powering the craft being external. It was conceptualized by aerospace engineering professor Leik Myrabo at Rensselaer Polytechnic Institute in 1976, who developed the concept further with working prototypes, funded in the 1980s by the Strategic Defense Initiative organization, and the decade after by the Advanced Concept Division of the US Air Force AFRL, NASA's MFSC and the Lawrence Livermore Nat When ... we were working o a beam about 6" in diameter for our own efforts when the plug got pulled on the project. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [November 4, 2019, 5:31pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/34 "2019-11-04T17:31:43Z")
> [@Chronos](#): > > “Belters” is a common science fiction term (especially in Niven’s Known Space series) for humans who live in the asteroid belt, with an industry built primarily around mining. “Groundhogs” is presumably derogatory slang for humans who live on (and probably have never left) Earth. I’m aware of who Belters are in SF. I was asking who they were in the real world. The answer is they don’t exist and will probably never exist. ---
**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, 6:22pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/35 "2019-11-04T18:22:25Z")
> [@Chronos](#): > > 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. Starship is designed to land with 50 tons of cargo, as I understand it. My point is that if they are coming back and landing empty, it’s a freebie to load them up with expensive stuff first. Just letting the stuff fall to Earth is not free. They would have to be encased in some sort of heat shield, which presumably would have to be manufactured in space from the slag of the asteroid or something, then you’d need a de-orbit burn, then you’d have recovery operations. With a Starship, you just land the stuff, and you’re done. If your ship was coming back empty anyway, it’s a free ride other than docking in space - which you’d have to do to prep the stuff for a re-entry anyway. For very large quantities that exceed the limits and availability of current rocket transport, sure. Find a big open desert and drop the stuff on it. ---
**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, 6:35pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/36 "2019-11-04T18:35:53Z")
> [@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. No one is going to bring iron ore or steel to Earth. It’s far too inexpensive to warrant asteroid mining. We’ll mine those things for sure, hut we’ll use them in space, not on Earth. The stuff we might bring back to Earth has to be very valuable. Gold, Platinum, other extremely rare elemenfs. We only produce 2500 tons per year or so worldwide. That 500 starship loads per year. Platinum is even better. Annual platinum production is only about 150 tonnes. Platinum is currently about $30,000 per kilo. So a single Starship load could bring back about $23 million in platinum, which would more than pay for the entire flight. I can imagine an economy like this: A space mining company finds a gold and platinum rich asteroid, and begins processing. They ship the stuff back to a depot in low Earth orbit, then simply offer a discounted spot price for anyone who wants to buy it from orbit. Let the market figure out the best way to return it to Earth. Some company might come up with a fantastic method for returning it cheaply and make a fortune, Others like SpaceX realize that after each satellite launch mission they could rendezvous with the depot, pick up a load of metal, and bring it back for extra profit. But ultimately, we don’t know how it will work. Once a market has been established there will be innovation and competition for ways to use the materials in space or on Earth. We are certain to be surprised by what this market ultimately looks like. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [November 4, 2019, 7:21pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/37 "2019-11-04T19:21:11Z")
> [@scr4](#): > > I’m not sure how you can have a large deposit of He-3. It’s a noble gas with a boiling point of 3.2 Kelvin. There’s only so much of it that can be trapped in rock. A surface exposed to the solar wind accumulates He-3 but we’re talking tens of ppb (parts per billion). Meaning you need to process a thousand tons of regolith to get maybe one ounce (30 grams) of He-3. What about “mining” the gas giants for Helium? Gotta be easier to get lots of helium there (if not necessarily the heavy isotopes). Just send a container ship on a highly elliptical orbit through the outer layers and let the speed compress the gas into your shell. ---
**Author:** ![Horatius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/horatius/32/3572_2.png) [@Horatius](https://boards.straightdope.com/u/Horatius)\ **Post date:** [November 4, 2019, 7:48pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/38 "2019-11-04T19:48:47Z")
> [@md2000](#): > > I think we’re overanalyzing. Built the rentry vehicles out of the core material with very high surface area to weight. Air resistance to slow the object, spread over a large area, means much less heat and less loss. Note the SpaceX boosters fall from a great height and only have to use their rockets to slow down when they are close to landing, since they are essentially empty cans with a high drag compared to weight, so a low terminal velocity. heck, build them shaped like giant windmills so they float to ground at a moderate speed spinning like a maple seed. I recall reading a proposal to return mined materials by basically blowing giant metal balloons. It’s in space, so the balloon is filled with vacuum. Find the right ratio of thickness of metal vs. size of balloon so that the balloon is self-supporting once in atmosphere, and then just apply a small de-orbiting burn to it. It produces the high drag to weight ratio you mention, and if you can set it up just right, it could be close to neutrally buoyant at surface level atmospheric pressure. You could add a layer of slag to the outside as an ablative heat shield too, if needed. I’ve never done the math on it to see if it would really work, but it sounds cool. And even if it doesn’t work perfectly, it would still reduce the velocity by quite a bit, making [lithobraking](https://en.wikipedia.org/wiki/Lithobraking)more effective, since, as others have pointed out, we really don’t care if we crash a lump of metal into the ground. ---
**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, 8:28pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/39 "2019-11-04T20:28:15Z")
> [@Horatius](#): > > Find the right ratio of thickness of metal vs. size of balloon so that the balloon is self-supporting once in atmosphere There isn’t one. ---
**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, 8:39pm UTC](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939/40 "2019-11-04T20:39:14Z")
Ah, OK, Starship is designed to be able to take 50 tons on a round-trip, but some trips will be one-way deliveries (putting satellites into orbit), so you’re thinking that you might as well take a cargo down, too. The problem there is that “space” is not all one place. If you’re launching a satellite, you’re going to be in whatever orbit that satellite needed to be in to do whatever job it does. And that’s probably a very different orbit than the orbit of your platinum depot. And changing orbits can be just as expensive as going into orbit to begin with. [Previous page](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939.md?page=1) [Next page](https://boards.straightdope.com/t/whats-the-cheapest-way-to-bring-something-from-leo-back-to-earth/842939.md?page=3)