They're fun flights of fancy, but that's all they are.

The Space Elevator article ignores some of the practical problems of establishing an elevator. For example, it says:

"The real problem is that, at $500 per gram, nanotubes are currently too expensive, and worldwide production is estimated to be less than 100 pounds per day."

No, that's not the real problem. The real problem is that bulk nanotube materials don't have anything like their theoretical microscopic properties. Expense and low production are secondary problems compared to the basic issue of, "We don't have a material strong enough to make a space elevator."

The space elevator would only partly answer the asteroid mining problem. It'd be great to have a metal-rich asteroid as the counterweight for a space elevator (the asteroid would be very useful for space-based industry), but the construction and operating costs of elevators may be very high compared to the cost of common industrial metals, which limits the ability to mine the asteroid and deliver the goods to Earth.

For example, CNN opines that the elevator could reduce launch costs by 98%. Great. Let's pick a cheap launch firm, like the Russians, and generously say the Rooskies can launch for $1000/pound (vs. $10K/pound in the US). 2% of $1000 is $20 a pound. Now, $20/pound is frickin' awesome for space travel (don't get me wrong) but raw iron goes for only $0.20-$0.30 a pound, I think. Common steels aren't much more expensive. Aluminum alloys tend to be about 3-4x as expensive as steel per pound, but that's still a fraction of $20/pound. Who wants to buy "space steel" that costs $20 a pound when you can get it from Earth for a fraction of the cost?

There are rarer materials that might come from an asteroid - like platinum group metals - at a profit, but it won't be the basic industrial metals that make up most of the $20 trillion claim.

I admit, I love to use space elevators and asteroid mining in near- to mid-future settings (2050 to 2200AD), but don't expect to see them soon.

Um...how big is it? Would it create a new tidal effect due to gravitational pull?

No. A monstrous asteroid with enough metals to support mankind's industrial needs for centuries is only about 5km across. It won't exert enough tidal forces to be noticeable with anything other than sensitive scientific instruments.

The short answer is: no.

The medium answer is: no such thing.

The long answer is: a little rock like an asteroid doesn't register among the gravitational movers and shakers in the Solar system. The objects that matter are the Sun and Jupiter. As far as Earth is concerned, the moon is also important.

The solar system is a messy, chaotic place. Some objects, like the planets, have found stable havens that are resistant to minor changes, but even safe havens aren't perfect. Jupiter is a beast that can disturb planetary tilts - without the moon stabilizing Earth's tilt, Earth would be flipping quite a few degrees within just a few million years, like Mars. Smaller objects like the many wandering asteroids and comets get scattered in encounters with planets and quite often end up nose diving into the sun.

Moving a huge asteroid like Ceres (~1000km diameter) might cause local issues (i.e., for the asteroid belt), but something like a mountain-sized rock is a non-issue to planets. Such debris has been passing Earth - and all the planets - for billions of years with no ill effects.

Now, when debris HITS a planet, there's plenty of ill effects, but that's not due to "gravity pollution."

Yes! And it will definitly hurt the eco-system on the moon!

Sorry, that "cosmic balance" stuff sounds like one of the Eco-Crappers from "Fallen Angels"

I was under the impression the $20/pound was for starlift, not for bringing stuff back down? With creative use of generators, I could see dropping things from orbit actually being used to create power, in addition to giving you metal to sell on the ground.

The rate I heard for launching was $10,000 a pound, so $20 a pound back down makes sense. (Unless it is the counterweight for the elevator.)

I am also wondering how these satellite solar collectors are supposed to work. Do they create actual electricity in orbit and beam it down with microwave (again the tech isn't developed), or are they just collecting energy (heat and radiation or ?) and somehow beaming the energy down.

If they could prove that the Earth was producing "organic" materials such as oil, it would be a huge deal and covered far and wide for more than just the oil aspect. As of now, it's all hypothetical, but there are several theories about fossil fuel production.

Hydrocarbon. I'd be interested in hearing how large quantities of hydrogen were making it through the mantle to be bonded with carbon. What I can find with a quick search is "...that the process of hydrocarbon formation has taken place in the crust after a deep infiltration of meteoric waters...". The people supporting non-biological processes for production seem to be all oil companies, and they also seem to discount the total lack of quantity they find as relevant.

Really? I'm curious what you base the link to oil companies on.

There was a guy that came through Calgary last year. He had been invited to give a talk about non-biological sourced hydrocarbon in front of a number of oil company people, primarily geologists and related professionals. This fellow was noteworthy in that he had vocally predicted that the moon's surface was largely covered by a layer of dust when such predictions were not vogue. Damned if I can remember his name, I'd have to check with a geoligist friend of mine.

Anyway this guy was heckled. I mean straight out heckled to the point that the chairman of the society that invited him got up and asked people not to be so rude to the guest, even if they didn't agree with him.

The people talking about it might be somehow related to the geology field which is a critical field for oil and gas exploration and recovery. So that seems a pretty natural association. Obviously people that are making a living looking for oil and gas are going to be front and center among those interesting in where the hell it comes from.

But the theories about non-biological source oil, gas, and coal have very little support among the oil and gas industry. Past hucksters that used and abused the theory to fleece people haven't helped much.

As for the validity of the theory and proof, it is my understanding that there has been some physical chemistry evidence to suggest that some hydrocarbons found to have some sort of non-biological source, or at least a source that doesn't match up with current biological source theories. It was also shown last year that it is theoretically possible for methane to be created from a non-biological source, at least in a guesstimation of some mantle conditions.

A very oddball theory in some ways, and no way it accounts for the majority of our current hydrocarbon reserves. But exactly how much is out there, if any, and even where to look for it if it was there is a real head scratcher. They have a tough enouch time finding the stuff on a biological source basis where they have specific sedimentary layers they are looking in.

Boy, I bet that was embarassing.

You have to use the same machinery, use the same personnel, and pay for the same mortgage when you bring stuff down the elevator as stuff going up the ladder.

So, if there's a difference in electrical bills, I don't think that's going to significantly alter the price of shipping cargo up or down a fancy vertical railroad that might cost trillions of nuyen.

Current global production of steel is in the range of 500 to 1000 million tons per year. That's 0.1 cubic kilometers of steel per year.

A metallic asteroid might be 70% or more metal by volume, mostly iron.

A 5km diameter asteroid, one with a volume of about 60 cubic kilometers, would have about 40 cubic kilometers of metal, mostly iron.

In other words, at the consumption rate of steel (which has been roughly steady for a couple of decades), a 5km metallic asteroid would have enough iron to meet the needs of humanity for 400 years.

The other metals present should be good for a similar time scale.

Research. Misguided goals lingering from the 1960s Space Race. If you're going as far as Mars for "practical" (profitable) reasons, you might as well go to the asteroid belt or capture an Earth-crossing asteroid.

The densest form of energy that is wandering about space - near Earth anyway - is sunlight. So solar power satellites, if built, would be big solar cell arrays (photovoltaics).

They would then beam the power to Earth by microwaves or lasers.

As for being undeveloped tech, it's not undeveloped. Microwave power delivery is proven and almost trivial to manage. It's a non-issue as far as offering road blocks. The bigger problems are:
1) Assembling large structures in space (not demonstated)
2) Maintaining large structures in space (not demonstrated)
3) Building large structures in space cost effectively (unlikely to no-chance in hell)

I know SR has SPSs, but the real world economic analyses behind them are usually laughably optimistic and SR doesn't demonstrate the advanced launching systems (like orbital elevators) that might make SPSs cost-competitive with fusion power plants built on the ground (which SR also has).

There is also the good 'old not keeping all of our eggs in on basket. Move a few million people to Mars and the human race can survive if the arth is destroyed from some unforseeable reason (presuming that Mars isn't destroyed, as well). This is the best and most practical reason for long term space colonization.

It's a practical reason for space colonization, but Mars has an obnoxiously deep gravity well. It's also about as hard to live on Mars as anywhere else in space. And Mars only has about as much elbowroom as Earth's surface.

So, if you're going to live in space, you might as well pick some place that supports industry well, is easy to reach, has lots of elbowroom for the mass, and has all the elements you need to live - like the asteroid belt.

Do you mean as compared to an asteroid, or is gravity there somehow not proportionate?

Thank you very much for the clarification and answers. I appreciate it very much.

What I mean by "obnoxiously deep gravity well," is a personal opinion thing. My pet definition is that any vehicle launching from the object needs to be over half fuel by mass (when using realistic chemical fuels) just to reach orbit.

Earth's moon is at the low end of "obnoxiously deep" because a launch vehicle needs to be about half fuel by weight to reach orbit. Mars is worse - the vehicle needs to be about 3 parts fuel per part of dry weight and cargo.

On the other hand, a launch vehicle operating from even the largest asteroid, Ceres, only needs to be 20% fuel by mass to reach orbit with a generous safety margin and average fuel efficiencies. A vehicle just barely able to reach Martian orbit would be hotrod in the asteroid belt.

Communities and industrial facilities in the asteroid belt are like...seaport and river communities on Earth. They have easy access to high-capacity, cheap shipping via barges and gigantic oceangoing ships because it takes almost no effort to transfer cargo from the city to the transport and send the cargo on its way across the world. In comparison, colonies on planets and large moons are like landlocked cities in Alaska or Siberia. You can run train tracks out to them and fly in supplies, but the cost will be painful - compare shipping 70,000 tons of ore on a Great Lakes bulk freighter to shipping 70,000 tons of ore on 747s.

No, I didn't forget them. I dismissed them earlier in the thread as too optimistic. If they're present, life is easier but still not perfect.

That's incorrect. Once you're in Earth orbit, it still takes about as much effort (~3230m/s) to escape Earth's gravity well as it does to reach orbit from Mars' surface.

Further, if you use a low thrust means of climbing out of the gravity well (e.g., ion rockets), the required change in velocity is doubled (~6460m/s).

Similar situations apply to any astronomical object. Getting to orbit is, energetically speaking, only half way to escape velocity. In terms of velocity, orbit is only 70.7% of the way to escape velocity (for high-impulse rockets).

Basically, once you're in orbit the gravity well still has some fight left in it.

Instead of a compact counterweight on the space elevator, you can just extend the space elevator tens of thousands of kilometers further beyond geosynchronous orbit. The far end of the elevator will be moving well above orbital velocity for that altitude. A spacecraft can be "flung" off the end. The energy for this ejection is taken from Earth's rotation.

Alternately, you can use a series of rotating tethers to fling payloads around and reboost the tethers by a variety of means: high efficiency, low thrust engines (SR has some form of fusion rocket, based on the Probe Race fluff); interactions with Earth's magnetic field; braking returning payloads after launching other material; etc.

http://www.tethers.com/MXTethers.html

Artificial gravity works fine on asteroids. There are several options available:

**A rail habitat that circles the equator of the habitat, a train of habitats.
**A rotating wheel or cylinder built on the surface or in the interior of the asteroid.
**The Cole habitats, which melts and inflates the asteroid into a sphere or cylinder that can be rotated for gravity (Cole habitats are crap, though. Atmospheric pressure would blow them apart because of the crappy, impure materials used in their construction.)

In higher gravity asteroids, or even on places like the Moon or Mars, you can use rotating habitats. However, the wheel needs to tilt outward a bit so the rotational "gravity" and natural gravity add up to a single gravity vector (i.e., so the floor doesn't seem tilted to occupants.)

You end up basically building a spinning space station on the asteroid, which is convenient - there's no shipping to be done, unlike for stations built in open space. Plus, radiation shielding is easy if you build inside the asteroid, and you don't have to worry about finding reaction mass to spin up large rotating habitats.

For further gamer-friendly info, I'd recommend picking up GURPS Transhuman Space "In the Well" and "High Frontier."

Also, scan to the highlighted words "track" and "habitat" here. There are some diagrams of a rotating track habitat on the asteroid Eros.

I really doubt any asteroid could handle 1G of spin. Most seem to be big balls of gravel and dust. Others, even if they're made of solid rock, aren't going to stay together after billions of years of being pounded by meteors and other impactors. All those faults and fractures...

Spinning a couple of mountain-sized wads of dirty, stone-laden metal up to 1G is begging for trouble. Less trouble than a typical stony asteroid, let alone a dust ball, but it's a lot of effort and energy that isn't necessary. You're looking at creep problems, the iron flowing like taffy under its own incredible weight, nevermind the anchors and tethers that join the spheres together.

Each 5-mile diameter ball of iron and rock (at about 6g/cc) is about 2 trillion tons. Spinning that up to 1G would take a lot of energy (nevermind the epic engineering challenges of spinning 4 trillion tons at 1G) that isn't needed.

As John pointed out...why not just build a space station out of the asteroid material? The frame of a 2km diameter toroidal station can be about 10,000 tons, comparable with a small oceangoing ship.

raises the dead

I just came across this article about the physical chemistry experiements I mentioned a couple months back. That is likely the basis for what those kooks on Coast to Coast were talking about. Although I find quite dubious this claim about calculations not being able to account for all the hydrocarbons accessed and used, this article again mentions the small known deposits of methane that appear to be abiogenic.

As for how water gets down that far, marble is the metamorphic form of limestone which is a sedimentary rock. Meaning it was in the presence of water at one time and often it still has water in it's vugs, the small version of limestone caves. Since the normal source for limestone is marine life, shells and coral, I'm not sure exactly how that rock is down that far, it must be very, very early sedimentary rock and just has billions of years of rock piled on top of it. I don't really know of any other source of limestone other than marine life, but then again I don't have a geology degree. I'll try ask around with geologists and paleontologist I know. If it is marine life sourced it might also contain biological source methane as well as abiogenc methane.

I thought that was a mistake at first. Now I'm not sure....

There's a really good description of a space elevator in Kim Stanley Robinson's Red Mars series.

So Cray, Mars has two moons, but you mentioned that it "wobbles" a lot more than earth. Because it's closer to Jupiter, or because its moons are too small?

(BTW: Do you work or study in the field? I'd like to refer to some of what you said, but I'd like to know who I'm referring to.)

Another thing I read is that the fanciful elevator would have to be built on or near the equator. So, if anyone's going to use a space-elevator project in their game, there's bound to be some political considerations.