Bringing iron asteroids down to Earth?

[rrw4rusty]

Hi,

I'm writing a science fiction story and in the future we are having to bring iron asteroids down to Earth. These asteroids are 1 to 3 miles in diameter and shaped charges brake up the asteroid and push it down into the atmosphere in such a way that the house size chunks land in an unpopulated area.

But... will they burn up in the atmosphere? I know natural ones do but these are traveling at great velocities. How could I bring iron asteroid material down to Earth in such a way that there's enough left to make it worth the effort?

Is there a better forum or place to ask this?

Thanks,
Rusty

 

[DaveC426913]

Hi,

I'm writing a science fiction story and in the future we are having to bring iron asteroids down to Earth. These asteroids are 1 to 3 miles in diameter and shaped charges brake up the asteroid and push it down into the atmosphere in such a way that the house size chunks land in an unpopulated area.

But... will they burn up in the atmosphere? I know natural ones do but these are traveling at great velocities. How could I bring iron asteroid material down to Earth in such a way that there's enough left to make it worth the effort?

Is there a better forum or place to ask this?

Thanks,
Rusty

Asteroids that large will not burn up so much as they will tend to explode.

 

[BobG]

Here's a link to a book that discusses it. A portion of the book is available for viewing on line.

Dynamics of Atmospheric Reentry

Nickel-iron meteorites surviving reentry are fairly common. However, slowing it down and controlling where it lands is a problem. You could slow it down enough to orbit the Earth (vs a high speed hyperbolic orbit). Any decreases beyond that lower the satellite's altitude and, as the altitude decreases, the atmosphere becomes thicker and the satellite will continue to decelerate and lose altitude, but will still reenter the atmosphere at a pretty high rate of speed.

You won't have any fine control of where a rock with an uneven surface will land. In fact, there's no fine control of where most satellites will land when they reenter the atmosphere, since they're designed to live in space, not reenter the atmosphere (in fact, almost all of a satellite burns up in the atmosphere - spherical titanium fuel tanks, however, seem to survive reentry quite well). When satellites are deorbited at the end of their life, the operators aim for big targets, such as the Pacific Ocean.

Without a shape specifically designed for reentry, the best you'll be able to hope for is to aim for a continent with very few inhabitants and then search the continent for your 'meteorite'. Monitoring the rock before reentry and the telltale streak of a flaming rock falling from the sky makes it something that's at least possible, but it will still entail a large overhead for operations - especially for insurance to cover the rare few that land in a city instead of a remote area.

In addition to the linked book, check out how hard it was to solve the controlled reentry problem during the early days of the space age. For the US's first reconnaissance satellites, it wasn't until the 13th try that they got one to land close enough to it's target for it to be recovered. (The recovery of the film cannisters is a pretty interesting operation in itself, as they used to be snatched out of the sky as they fell by a C-119 airplane. It would be so cool to tell people your job was flying around in a plane and catching objects falling from outer space.)

[PLAIN]http://www.aviationnews.eu/blog/wp-content/uploads/2010/08/c-119_CORONA-600x342.jpg

 

[DaveC426913]

[PLAIN]http://www.aviationnews.eu/blog/wp-content/uploads/2010/08/c-119_CORONA-600x342.jpg[/QUOTE]
I have a 48^th scale C-119 Flying Boxcar plastic model kit at home in my library, still in its shrinkwrap, waitnig for the day when I am motivated to build a diorama of the Phoenix in partial construction from the 1965 Jimmy Stewart http://www.aerovintage.com/phoenix3.jpg".

Sorry. Carry on...

 

[Max™]

http://launchloop.com/

 

[DaveC426913]

http://launchloop.com/

Ah. And this can be used to land asteroids?

 

[Office_Shredder]

Launching something into space and landing something from space are not equivalent problems Max

I'm envisioning a magnet based system... the asteroid is magnetized in space, and then magnets are used to push it around to control/slow its descent. Unfortunately any plane with a magnet attached flying close enough to actually push the asteroid would have to have a hell of an engine to get close enough (equal force against the plane, which pales in comparison in terms of mass)

 

[Max™]

Pretty sure you could bring something in on a suitable trajectory to dock with a launch loop/follow it down.

Remember, this thing would be 50 miles up, damn near halfway to the lowest space shuttle orbit, and with enough accelerative ability to toss payloads into those orbits, or receive them.

More importantly, you could get the processing equipment needed to actually work with asteroids in space up with a loop, and land craft with just processed material as needed.


Think it would be wonderful for more sci fi stories and whatnot to mention them instead of dweeby elevator ideas, maybe even shape some future policy makers towards an achievable real world launch system.

 

[rolerbe]

Rusty,

Since it's SF, perhaps you can also use the notion of a space elevator (look it up in Wiki). Manuever the asteroid into geosync orbit, match positions to the nearest space elevator, chunk it up to suitable sizes in space, haul it down the elevator.

Not a crazy notion if you have very high tensile strength wires like (non-existant) nano-fibers.

Good luck with the story.

 

[Max™]

*screams*

That is exactly what I was trying to avoid, by suggesting a realistic alternative.


We could build a launch loop with real world materials (check out the site, about $2 billion from estimates), we will need magical fairies spewing unobtainium to build an elevator.

 

[Evo]

In the sci-fi books I've read, they carry out mining of the asteroid itself, while it's in space.

I wonder which would be more realistic, mining in space or bringing them to the ground on earth? What would be the difference in getting one to the surface of the moon for mining, then bringing the smaller fragments of ore to earth? In case it's not already obvious, I have no clue about this stuff, but I like science fiction.

 

[JaredJames]

Or take the Red Dwarf style approach and build a mining ship which processes asteroids.
(I think it took them in through the front)

 

[BobG]

Rusty,

Since it's SF, perhaps you can also use the notion of a space elevator (look it up in Wiki). Manuever the asteroid into geosync orbit, match positions to the nearest space elevator, chunk it up to suitable sizes in space, haul it down the elevator.

Not a crazy notion if you have very high tensile strength wires like (non-existant) nano-fibers.

Good luck with the story.

*screams*

That is exactly what I was trying to avoid, by suggesting a realistic alternative.


We could build a launch loop with real world materials (check out the site, about $2 billion from estimates), we will need magical fairies spewing unobtainium to build an elevator.

I agree that there would be huge problems with a space elevator. It's a great idea in theory (a perfectly spherical Earth, no wind or other stresses, a way to make a cable thousands of kilometers in length while still being stronger than any in existence, plus an incredibly cheap energy source).

Your solution has the same problems. For one, I think your loop would have to be at least twice as high. It has to intersect the orbit of the asteroid before the atmosphere is causing heating and perturbations to the orbit of the asteroid. The asteroid has to be traveling at an orbital speed (approximately 7800 meter/sec at a heighth of 200 km). The vehicle in your launch loop has to accelerate to match the asteroids orbital speed in order to catch it, and then your vehicle has to slow down without burning up. I can understand how a 'cable' moving 14,000 meters/sec can accelerate the catch vehicle, but I don't see how the vehicle is going to slow down.

There's a reason it's called a launch loop.

The disadvantage of breaking up the asteroid in space is that you have to launch vehicles into space to catch the pieces and bring them down. That's an awful lot of launches with an awful lot of fuel or a few launches with really big spacecraft and an awful lot of fuel.

Or, if the launch loop lowers the launch cost enough, break up the asteroid and the launch loop launches the spacecraft that will bring the asteroids to Earth.

The key to all solutions is that the fuel used for any solution costs less than the iron that burns up in the atmosphere (keeping in mind the free reentry solution has that pesky problem of unpredictability that has to be overcome).

Planing and shaping the asteroid to form a nice balanced shape with a bottom shaped like a space capsule and coating it with something similar to the tiles on the space shuttle would provide some possibility, with the difficulty that all of this would have to be done on an asteroid orbiting the Earth. I'm not sure that would be a cheaper option than just breaking the asteroid up and shipping it down in spacecraft if the launches are cheap, but at least it offers a cool job (asteroid sculpting) and offers some drama with the occasional reentry malfunction that takes out a city (if you want them to make a movie from your book, then I think taking out a city is essential).

 

[DaveC426913]

Think it would be wonderful for more sci fi stories and whatnot to mention them instead of dweeby elevator ideas...

Funny that you disparage elevators. Contary to this launch sytem, which requires a vast energy source, space elevators are basically free energy-wise. And they work both ways up and down.

 

[JaredJames]

Out of curiosity, are there really that many asteroids that could be broken down into chunks the size of houses coming within a reasonable range to earth? (At least so far as being able to make a business out of it goes.)

Would it not just be easier to send something to Mars and mine that?

(I'm not trying to change your story, I'm just curious about the asteroid count.)

 

[Office_Shredder]

I like Evo's idea. Crash the asteroid into the moon and pick up the pieces at your leisure. I only wonder if there's potential for destroying all life by knocking the moon out of orbit (speaking of a movie idea: They have 72 hours to stop the moon from crashing into the planet! ... oh, that's been done already?)

 

[BobG]

I like Evo's idea. Crash the asteroid into the moon and pick up the pieces at your leisure. I only wonder if there's potential for destroying all life by knocking the moon out of orbit (speaking of a movie idea: They have 72 hours to stop the moon from crashing into the planet! ... oh, that's been done already?)

Really?! What movie was that? (I want to see it! I don't care if it is a stupid premise!)

How about if we just knock it into an elliptical orbit that comes closer to the Earth, providing us with some awesome waves for surfing! I want to see Annette Funicello in a sci fi movie!

 

[BobG]

Out of curiosity, are there really that many asteroids that could be broken down into chunks the size of houses coming within a reasonable range to earth? (At least so far as being able to make a business out of it goes.)

Would it not just be easier to send something to Mars and mine that?

(I'm not trying to change your story, I'm just curious about the asteroid count.)

Really big asteroids are rare. However we just had a couple in the 20 to 65 meter size pass close by earlier this month (Sep 9). Apophis, a 350 meter asteroid, passes close by about every 7 years. Apophis would definitely have to be broken up and brought in in several smaller pieces. It's real hard to find a good landing spot for a 350 meter asteroid.

There is no accurate count of how many asteroids come close to the Earth, seeing as we haven't been tracking them for very long. Near Earth Asteroid Discoveries

 

[Office_Shredder]

Really?! What movie was that? (I want to see it! I don't care if it is a stupid premise!)

Well, it wasn't a movie per se. The video game Majora's Mask was based on the premise of the moon hitting the planet

 

[Evo]

Well, it wasn't a movie per se. The video game Majora's Mask was based on the premise of the moon hitting the planet

I will go on record as saying that the moon hitting the Earth would be bad.

 

[DaveC426913]

I will go on record as saying that the moon hitting the Earth would be bad.

Citations?

 

[JaredJames]

I will go on record as saying that the moon hitting the Earth would be bad.

I agree with Dave, I can foresee there being some minor issues, but without a full scale government funded study into the matter I would be hesitant to comment on the 'major' issues that such an event may or may not cause!

 

[Max™]

Funny that you disparage elevators. Contary to this launch sytem, which requires a vast energy source, space elevators are basically free energy-wise. And they work both ways up and down.

http://launchloop.com/slides/launchloop.pdf

Includes a breakdown of materials based on current prices, something like $540 million (page 37/40 of the pdf), with the $2 billion number listed below as a ballpark for the first one + research costs.

Assume the total cost of the Launch Loop, including research costs, comes to 2 billion dollars. If it is used
at only 30% capacity of 500 MWe (26,000 metric tons per year), and is amortized over 1 year as a highrisk
venture, the cost per gross kilogram (including 6 cents per kWh oil fuel cost) is $85. While this launch
rate is nearly two orders of magnitude above present U.S. launch rates, it is a tiny fraction of the 3.5
million tons per year capacity of the basic system.
Later, at 85% usage of a 4 GWe power capacity (750,000 tons per year), 5 year amortization, 9 billion
dollar capital cost, and 1.3 cents per kWh fuel cost, the cost per gross kilogram is $3. At this cost, labor
and vehicle systems will probably dominate net payload cost.
Total Launch Loop system cost is likely to be well below that of Earthtohighorbit
rocket systems.

http://ap1000.westinghousenuclear.com/index.html

These aren't exactly absurd energy requirements, and an elevator would still require energy for the payload climbers.

An elevator also requires advances in material sciences beyond what we currently have available, while a launch loop does not.


You could bring something down to meet the loop and let it brake by accelerating the rotors in the loop directly, then haul it down to a base station as usual.

It is of course quite a bit easier to get down into a gravity well than to leave one, but that is why the effort should be devoted to more effective methods of going up, isn't it?

 

[DaveC426913]

http://launchloop.com/slides/launchloop.pdf

Includes a breakdown of materials based on current prices, something like $540 million (page 37/40 of the pdf), with the $2 billion number listed below as a ballpark for the first one + research costs.

You miss the point. Construction is a one-time cost. It's the operating costs that add up.

It is of course quite a bit easier to get down into a gravity well than to leave one, but that is why the effort should be devoted to more effective methods of going up, isn't it?

Yes, which makes one wonder why you would turn your nose up at the opportunity to go up basically "for free".

 

[rolerbe]

Well, at the risk of more *screams*, another (future, SF) thought would be to machine the incoming asteroid into (one or more) lifting bodies. Yes, they're heavy and dense (or they're not worth much), but consider the recent space shuttle -- really very small wing area, and you would not have to have even that much lift for an unmanned body.

So, assume elliptical asteroid. Split in half to have reasonably smooth underbody. Carve away some of the upper edges to create stubby winglets. Attach computer controls (or even real pilots for dramatic potential), and some pretty modest reaction jets, and 'fly' (as in controlled crash) the thing down. Pilots guide to selected impact area and jettison just before crashdown.

I won't do the calculations of required lift, etc., but might be worth an hour or two of the OP's time.

 

[Max™]

That would work as well, but you'd have to make more of a heat shield/lifting body to take something down through the stratosphere/troposphere than you would if you were just maneuvering it to intercept a loop 50 miles up.

You can make a similar type of structure called a space fountain, where you fire a stream of projectiles up from a ground station to be caught/returned by an upper station. If the upper station was allowed to move upwards, you could lift it bit by bit, and build a usable lifting track from the ground up which wouldn't have to support the vast material stresses imparted on an elevator.

 

[JaredJames]

Max, don't mean to sound too negative here, but you seem fairly set on having a launch loop so is there really a point in us suggesting any more ideas?

Just because the launch loop could send items up to space, it doesn't mean it could bring them back down. The impact force of a house size asteroid hitting it (even after being slowed down slightly) would be immense. The materials don't react the same to sudden impact as they do to prolonged exposure (to a force - as would be experience during a launch).

Also, if your picture is a good depiction of it, and it is 50km high. That would make it roughly 200 - 300km wide. Do you really believe this is any more viable than a space elevator? I see a lot of 'hypoothetical' and 'assuming' in your links and articles so I don't know how seriously to take them.
According to this source http://news.bbc.co.uk/1/hi/business/7180539.stm - they put the cost of a power plant to fuel your loop at $4.5 billion dollars, blowing your "assumption of 2 billion dollars" build costs out of the water (you did say you would need a power station to power the loop - I've used a nuclear plant for costing), plus there are then operating costs for such a plant. And then you still need to build the launch loop and I think $500 million dollars is extremely optimistic for such a leviathan of a structure.

In your book it may well be the solution, but it seems as if you're pushing this as a real life solution, hence my response. I personally agree that a space elevator is the key to getting things to and from space, but until we have the materials, that is out of the question.

 

[DaveC426913]

Max, don't mean to sound too negative here, but you seem fairly set on having a launch loop so is there really a point in us suggesting any more ideas?

Max is not the one writing, Rusty is the OP. The launch loop is merely Max's pet.

 

[Jimmy Snyder]

Mine the asteriod in situ and send the iron to L5. Build the infrastructure for a community there and send as many people as you have resources to support. Eventually we'll all get out of this gravity well up where we belong.

 

[JaredJames]

Max is not the one writing, Rusty is the OP. The launch loop is merely Max's pet.

Ah, then apologies.

Rusty, I don't know what sort of system you are looking for, do you want something really sci fi (some sort of anti-gravity 'beam' to bring them in)? Or are you looking for something realistic or potentially viable (with a hint of sci fi)? I only ask this as letting them drop out of the sky clearly isn't the ideal solution here.

Max, I still think you are trying to push this as a 'perfect solution' to space travel.

 

[Max™]

Mine the asteriod in situ and send the iron to L5. Build the infrastructure for a community there and send as many people as you have resources to support. Eventually we'll all get out of this gravity well up where we belong.

Edit: this is another idea I'm fond of. Hollow some asteroids out into habitats while you're up there too!


It's not that I'm exclusively for the loop, I'm just completely against elevators, they're currently impossible. The material stresses are significant enough that even if we had a material that could support itself to that height, which we don't yet, we still need to protect the portion at the base from atmospheric stresses, and the top from micrometeors/major meteorite impacts. Plus the stresses of carrying loads.

There is an arguably far better way to do the same thing, which could be built today, and would make an interesting variation from the normal unobtanium space elevator plot device.

I always liked my sci fi to be at least plausible, a space elevator is not plausible.

Contrary to what you might read on some sites: http://spaceelevatorconference.org/default.aspx

As for the size, there is a graphic in the PDF showing multiple sites located in the pacific and atlantic ocean near the equator, selected based on past weather patterns/projections of future storminess. 2000 km stretched across the pacific isn't as big as you might think.

You would build it at the surface of the ocean, then after getting it completed you'd begin to circulate the rotor through the sheath, which would raise it to the necessary height in a controlled manner, allowing you to set up cross braces and so forth.

I admit it is something of a pet project, as I remember daydreaming about the things I would do if I could build and own a space elevator, before reality brought that idea literally crashing down.

I learned about the loop concept a year or two ago, though I had seen the space fountain idea years earlier, but I didn't discover just how possible it would be to actually do something like this until I was rambling about how silly it is to be excited over the "recently discovered mineral wealth in Afghanistan" news story last year, and pointing out just how vast the resources available in a single average sized asteroid wouild be.

"Yeah, but how are you going to go get those resources?"

*looks around, sees the lofstrom paper*

'Eureka!'

 

[DaveC426913]

I always liked my sci fi to be at least plausible, a space elevator is not plausible.

Do you know what 'plausible' means?


Not only is it plausible, it's quite possible, just not yet. Our technology is currently showing that the trend will get us there.

To suggest it's not possible let alone that it's not plausible is like suggesting that Rusty should not have PetaFlop computers in his story. Since they haven't been built yet, they never will be. And that means they're not even plausible. Nonsense.

 

[Max™]

Reasonable, or probable.


http://spaceelevatorconference.org/Documents/RT%20Space%20Elevator%20Space%20Debris%2022June%2010.pdf

Compare the difficulties inherent there, the issues of a continuous 100,000 km long megastructure that has to be built from the top down, beyond just developing the materials strong enough to build it, getting the material into orbit, assembling it, and also protecting it from impacts, etc.

Vs

A 2000 km multi-part megastructure which can be built on the surface, lifts itself to altitude, and requires no amazing advances in material sciences, or amazing amounts of incredibly rare materials.

Heck, a pre-existing loop would actually solve part of the difficulty with building an elevator, as you could use it to get the elevator materials up to GEO.

 

[DaveC426913]

Reasonable, or probable.

Well, reasonable is subjective. And probable is only available to you since you can see the future and we can't.

and requires no amazing advances in material sciences, or amazing amounts of incredibly rare materials.

This is one point, not two. It's a materials science challenge, granted, but the materials aren't exactly "rare".

a continuous 100,000 km long megastructure

The space elevator does not have to be 100,000km long; it need only be 35,000km long.

The space elevator is one order of magnitude larger than the launch loop. You overestimate it by almost another order of magnitude.


The space elevator has one thing that the launch loop does not: a strong grassroots movement - a lot of interested people in useful positions who not only think it can be built, but are highly motivated to get their own hands dirty.

The space elevator may end up getting built despite being "impossible"...

 

[JaredJames]

Where did a 100,000km structure come from?

I was under the impression space elevators only had to be just above 36,000km.

EDIT: (Seriously Dave, this just ain't fair! )