Lunar Space Elevator Instead?

koa writes "We have all seen articles on building a Space Elevator on the earth, how about this article about experimenting with the Moon first since the technology we have available to us is sufficient, as the Moon's gravity is 1/6th that of Earth's (the cable weight would require less exotic materials such as carbon nano-tubes). One could make a very good argument for commercialization of Space if getting materials to and from the Moon's surface was vastly cheaper and easier."

Comments

Interesting

[Sv-Manowar]

This theory has been investigated in depth in a recent book, http://www.amazon.com/exec/obidos/ISBN=014032870X/ 002-2420335-1812868

Re:Interesting

[CuriHP]

Have you considered actually reading the article? No part of this thing is attached to the Earth. It is a space elevator on the moon, and the moon only.

The point?

[hfis]

I thought the point of an elevator was to provide a launch platform removed from the restricitons of Earth's gravity and atmosphere. These don't exist on the moon, so what's the point?

Waste of money IMO.

Re:The point?

[GammaTau]

Actually Earth's gravity does exist on the moon. It certainly is a lot weaker than what we experience here but it is definitely real and measurable.

Re:The point?

[Garion Maki]

if you want to build somthing verry complicated that could cost several lifes if it failes and that requires knowledge of things you probably woulden't think about if you diden't first try it out, woulden't you want to build a scale moddel somwhere where it can't hurt to manny bystanders to test out the basics?

and it seems like the moon is the easiest scale moddel that is both relative easy to reach and that has both gravity and atmosphere(?) in a smaller scale than earth.
and about bystanders, the only ones who can get hurt would be the people you take with you to construct the thing, and who would be aware of all posible dangers, and the moon inhabitants, all 0 of them...

if you want to test it before you built the real thing on earth, then the moon seems like the best testing ground...
computers can test much, but they can't test things that their programmers aren't even aware of that it exsists (like unknown forces that could work on the elevator)

Re:The point?

[Englabenny]

No, the idea has never really been to put people into space; there are too many problems with this. As noted in the article, the time of the travel and cosmic radiation is a large problem with human transport in elevators. Even more so in the earth case, where we have the van Allen radiation belts. With the elevator in place at the earth, we'd have a tremendous goods shipping facility. Human travel comes much later.

Re:The point?

[div_2n]

I know this is /. and asking people to RTFA is a waste of effort, but just do it and you will have your answer. But since you won't, I will spoon feed you.

The point of the space elevator is to lower the cost of getting things from the ground to space. Even on the moon, you have to use energy to get things off the ground. The moon has resources that could be utilized in space (or Earth). Instead of having to land spacecraft, risk the dangers and use fuel that you have to get from Earth, you can set up a low cost assembly line type of setup where you can easily get the resources to space and inevitably the Earth or ISS.

As someone else pointed out, this would be a great opportunity to perfect the process. And I suspect that with the creation of an elevator on the moon and then one on the Earth, we will see the day when getting to the moon will not require having to get into spacecraft at all except to taxi from the Earth space elevator to the moon elevator. Then maybe one day Mars.

Re:The point?

[jdray]

Actually, per the article, the point would be to have a no-propultion way to get materials off the lunar surface and into an earth orbit where we can use them for construction.

Lunar Space Elevator?

[Anonymous Coward]

Bah! The idea is pure lunacy.

Except....

[Anonymous Coward]

Earth is where all the people and materials are. Building a space elevator on the moon would be like building a superfreeway from one point on antarctica to another point on antarctica: pointless as there's noone around to use it, nor anything to transport over it.

If you are going to just say "move people and materials from earth to the moon, then go from there" - you still have to escape Earth's gravity, which is the f'ing point of the earth-based space elevator to begin with.

Re:Except....

[Garion Maki]

unless...
you build the expencive elevator on the moon and start up a few mining/refining outposts with self suporting habitats.
once those are working good, you can start working on space stations/ships/habitats for a cheaper price, since most of the materials don't need to go past earth's gravity well, only the main part of human labor would need to come from earth.
the big and expencive part of the materials could be cheaply inported from the moon, and in a later stage, when space travel has inproved, you could get that stuff from the asteriod belts etc.

so even tho it might seem like a big and expencive thing to do, it might be verry usefull in the future.

Re:Except....

[TFGeditor]

"Earth is where all the people and materials are. Building a space elevator on the moon would be like building a superfreeway from one point on antarctica to another point on antarctica: pointless as there's noone around to use it, nor anything to transport over it."

"Iinsightful" my elbow. Doesn't anybody RTFA anymore?

FTFA: So, what would you do with a space elevator connected to the Moon? "Plenty," says Pearson, "there are all kinds of resources on the Moon which would be much easier to gather there and bring into orbit rather than launching them from the Earth. Lunar regolith (moon dirt) could be used as shielding for space stations; metals and other minerals could be mined from the surface and used for construction in space; and if ice is discovered at the Moon's south pole, you could supply water, oxygen and even fuel to spacecraft."

If water ice does turn up at the Moon's south pole, you could run a second cable there, and then connect it at the end to the first cable. This would allow a southern Moon base to deliver material into high-Earth orbit without having to travel along the ground to the base of the first elevator.

Re:Except....

[Mr2cents]

Indeed, soil is mainly SiO2, I don't think it's difficult to split it into Si and O2. With the silicium you could make solar cells (they are made in a vacuum so the moon is naturally suited for that), and the O2 can be used for breathing or as rocket fuel. The hydrogen is much lighter than the oxygen, so even if you would have to transport it from earth it would still be profitable. And instead of transporting the hydrogen, you might send hydrocarbons like methane, butane or octane. Then you get some carbon to the moon as well, and it's a lot easier to handle than liquid H2.

Re:Except....

[Shaiken]

A space elevator has to be equatorial. Without centifugal 'force' it won't stay up.

Re:Except....

[AndroidCat]

It would like when they were building the first highways across America. The company would build a "seedling mile" of good highway along a stretch of crummy road near some town. After people tried that mile of good road in the middle of a stretch of washboard, it was a lot easier to get them to vote for the taxes to pave more of it.

Re:Except....

[AndroidCat]

It provides a cheap way to get lunar materials into useful Earth orbit. If a lunar base is to be more than re-planting the flag or a geek paradise, then it has to do something. A pipeline for air, water and fuel to their customers in Earth orbit would be a start. Over time, more complex manufacturing could be done there.

The resources invested in it would be small compared to a lunar base, and since no one would be riding it (too slow), there wouldn't be fatal accidents.

Re:Except....

[AndroidCat]

The Earth does have plenty of dirt and water -- but some fool stuck it all at the bottom of a gravity well where it's not very useful.

Re:Except....

[AndroidCat]

In the case of a lunar cable, it's hung over the hump between the Moon and Earth's gravity wells with enough mass on the Earth side of the L1 point to balance the cable down to the Moon.

Moonbase would be in the always-lit north

[hattig]

So you'd also need to built a transport route between the northerly moon base and the equatorial lunar elevator. I suppose that would be a lot less effort than building a bloody lunar elevator though, given that we haven't even been to the place in around 30 years.

There's a good reason to build a terran elevator. For a start, we live on this damn planet! I think that the logistical problems of building an elevator on the moon will outweigh the material problems of building one on earth.

Of course, it could be that it becomes cheaper and easier to simply launch ships from Earth in the future, making an elevator redundant.

Re:Moonbase would be in the always-lit north

[ironduke-particle]

So you'd also need to built a transport route between the northerly moon base and the equatorial lunar elevator. I suppose that would be a lot less effort than building a bloody lunar elevator though, given that we haven't even been to the place in around 30 years.
Northerly moon base? The best-argued location I ever saw was for the lunar south pole; permanent sunlight, water, and constant ambient temperatures of -20degC.

But, yes, a lunar space elevator would have to have an equatorial ground station, and the lunar equator is far from the best place for a moonbase.

Re:Moonbase would be in the always-lit north

[danila]

RTFA. The logistical problems consist of launching 7 tons of kevlar cable to the L1 point 250 000 km from Earth. I am not saying there are no technological obstacles to overcome, but compared with Cassini probe or Mars rovers this is a piece of cake. There are existing rockets with that launch capacity, it doesn't take long to get there, it's cheap, easy and we get to test the space elevator prototype. There is simply no reason not to do it in the next few years.

Mistake

[sconeu]

Unless we have a working lunar colony/base, it's useless.

The whole point of the elevator was to make it easy to get out of Earth's gravity well. To get to a lunar elevator, you still have to do that.

First things first...

[bani]

...how about long term stays on the lunar surface? As in months or years.

How about a lunar colony instead of a freaking space station?

Would seem to be a prerequisite for anything approaching a lunar space elevator.

And long term lunar stays would provide valuable practice for something like a martian colony.

An interesting experiment

[Jarvo]

The mass of material required for such an elevator (while smaller than an Earth-centric one) must be pretty large compared to the mass that 1 rocket could launch to the Lagrange point.

I'm glad I haven't heard many fearful and wildly speculative comments about space elevators. The most obvious one would be 'what if the cable breaks?'. Any Chicken Littles in our society would assume that lengths of the cable will fall, crushing sections of cities.

A lunar elevator would show that such fears are unfounded.

It would also be good to work out design bugs.

Big difference between theory and practice

[Timesprout]

Sounds like one of those ideas that are theoretically possible but utterly impractical to implement.

Yes the elevator could be built. What exactly are we so desperate for we can only get from the moon? Oh thats right, nothing, at least nothing that makes the expense of this endeavour currently worthwhile. The cable may be inexpensive but who wants to pay to put the lunar base in place and get the heavy mining equipment up there, cos that aint gonna be cheap. Also it conveniently fails to explain how we actually get material back to Earth from the L1 point. Maybe it is to be pushed into a decaying orbit by the climbing robots and we take our chances?

For a second I thought ....

[Gopal.V]

I thought we were going to use the moon to anchor this to , instead of the typical big bulky sattellite.

Relocating to the Moon won't help the project a bit if the raw materials (whatever) has to be brought from Earth . A mining/harvesting camp on Moon would be at least a few decades away, until then this can wait on the backburner. An orbital platform harvesting asteroids for heavy metals would rock ! (literally) . Would be nearer to earth and it would put solar sails in the domain of practical rather than as Sci Fi book fodder.

Hmm... all the differential equations in Rocket Science confuse the hell out of me . I suppose the space elevator doesn't have the rocket's exponentially growing weight problem ?. (Now I know why they say "It ain't rocket science)

I'd rather vote on the space catapult to launch rockets at Mach 3 (or higher) with something (jet aeroplanes or Maglev rails on mountains) . If the initial acceleration can be supplied by ground based non-moving power equipment, the rocket could go a looong way in reducing weight.

Sadly the word space Catapult brings into mind unnecessary images of North Elbonia and .....

The point of building on the moon

[Legion303]

Tons of people are complaining that this is a useless gesture, as the ultimate point is to transfer material out of earth's gravity well. But they're missing the point of building on the moon first. Think of it as a proof-of-concept. Once we have a working elevator in place, we can then test its performance and learn a great deal about how to eventually build one on earth.

Space Solar Power Satellites

[Baldrson]

Given the geopolitical pressure cooker over energy resources there is a lot to be said for Gerard K. O'Neill's proposal to use lunar materials to fabricate space solar power satellites. The Lagrange-point elevator could replace the mass driver in O'Neill's system and since the mass driver was the most problematic aspect of the proposal it may turn out that O'Neill's proposal just became a lot less risky.

An effect of O'Neill's proposal is the creation of space settlements which could house thousands of times the land area of the Earth from asteroidal materials alone. The creator of the space-settlement FAQ, Mike Combs, says in that FAQ to the question "Is space settlement a solution to the overpopulation problem?":

Probably not. No space transportation system we can imagine (although that might be a significant qualifier) could keep up with the number of babies being born.

This is ironic since O'Neill himself described just such a transportation system and projected depopulation of Earth to require an infrastructure not much larger than that supporting the commercial airlines.

Sure, you could, but...

[david.given]

...the top of the elevator has to be in geostationary orbit, because the entire elevator is attached to the ground. The moon rotates once every thirty days. You can calculate, using this equation:

orbital_radius^3 = (3,600^2 * surface_gravity * surface_radius^2 * orbital_period^2) / 2*pi^2

...the height of the elevator, therefore; for the moon it's 190000km. In other words, five times higher than one on Earth! That's nearly half-way to Earth; the gravitational disturbances from Earth's much greater mass could well make the whole thing infeasible.

Re:Sure, you could, but...

[ZorbaTHut]

"A lunar space elevator would work differently than one based on Earth. Unlike our own planet, which rotates every 24 hours, the Moon only turns on its axis once every 29 days; the same amount of time it takes to complete one orbit around the Earth. This is why we can only ever see one side of the Moon. The concept of geostationary orbit doesn't really make sense around the Moon.

There are, however, five places in the Earth-Moon system where you could put an object of low mass - like a satellite... or a space elevator counterweight - and have them remain stable with very little energy: the Earth-Moon Lagrange points. The L1 point, a spot approximately 58,000 km above the surface of the Moon, will work perfectly."

In other words, RTFA.

Re:Sure, you could, but...

[barawn]

The moon rotates once every thirty days.

It also orbits the Earth once every thirty days - in other words, it's locked in a 1:1 resonance with the Earth. This is of great benefit in this case!

A little background:

Space elevators need to remain stationary with respect to the body that they'll be attached to. With the Earth, that means you need to be rotating at the same speed as the Earth - in other words, GEO.

With the Moon, however, you can either be rotating as fast as the Moon, or orbiting as fast as the moon, because the moon rotates at the same angular speed as it orbits! And there are 5 places where that occurs - the Lagrange points.

From any one of those points, the Earth and the Moon are stationary in the sky - that is, you don't see either of them moving with respect to each other. Since the Moon's rotation is defined by its orientation with respect to the Earth, therefore, you don't see the Moon rotating. That is, you're in something that's exactly the same as GEO.

Of the 5 Lagrange points, obviously L3 is silly - it's on the opposite side of the Earth as the Moon. So that won't work.

L2 is similarly silly - it's on the opposite side of the Moon as the Earth. Could be useful for sending things to interstellar space, but not for Earth-Moon transits.

So you're left with L1, L4, and L5. Obviously if you're talking about getting things from the Earth to the Moon, you'd want the one that's deepest into Earth's gravity well - and that's L1, "gravitationally halfway" between the Earth and the Moon. And that's what's being proposed.

One helpful thing is that L1 is unstable - orbits tend to drift away from there. However, an elevator tethered to the moon at least anchors one of the unstable directions (radially towards the moon/away from the moon), and I'm not sure if the perpendicular direction is unstable as well. So it may be that an elevator in that position is stable, and that unpowered objects will tend to move away from the elevator. You'd have a natural deflection mechanism. Pretty interesting!

Actually, a combination of an L1 and an L2 elevator could be quite interesting, though you'd have to build something like a railway around the Moon. Once you do that, though, you could go out past the L2 point, and you could sling yourself into interplanetary space. I'd have to work out how much of a boost you could get, but Mars orbit seems quite reasonable.

It's not as good as a terrestrial elevator (because the Earth rotates so quickly, so you can steal more of the Earth's angular momentum), but it's certainly currently feasible.

Re:Sure, you could, but...

[Alsee]

L1 is unstable... I'm not sure if the perpendicular direction is unstable as well

The instability is only directly along the earth-moon axis. Imagine a triangle based on the earth, moon, and the object. The earth-moon axis is the base of the triangle, and the other two sides of the triangle represent the earth's and moon's gravitational pulls. The two sides of the triangles nearly balance except that they both pull in the same direction back towards the axis.

So a counter weight on the earth side of the point will pull towards the earth (and be stabilized by the moon anchorage) and be stable in all other directions.

Releasing a payload from either the counterweight on one side of the L-point or from anywhere on the cable itself on the other side of the L-point gives you a choice of which way to "fall away". And during that "fall-away" any any off-axis thrust would be amplified. A very good place to start from making it easy to "fall" off into different orbits in any direction.

And if you are willing to accept travel times on the order of months you can use the chaos points of the three-body system to loop around the earth and moon and get a major gravity-kick towards almost any orbit you like, almost for free.

L2 is similarly silly - it's on the opposite side of the Moon as the Earth. Could be useful for sending things to interstellar space, but not for Earth-Moon transits.

I believe L2 is also off-axis-stable, only instable along the axis. Assuming so:

Once you are out of the gravity well and into lunar orbit it really doesn't much matter which side of the moon you're on. In orbit you can naturally coast from one side to the other. Any thrust involved would be negligable compared to kicking mass over to an earth-centered orbit. But as I mentioned above, if time is not a factor you can use three-body chaos to manage that orbit tranfer almost for free.

-

Re:how to design against terrorists?

[Troed]

BOO TERRORISTS!

You must be american. Get over it - or take some lessons from countries (Spain, England) that have had "terrorists" to deal with for many years - and you don't see them going bananas over it and mentioning it in all sorts of contexts.

Re:orbit

[Matrix9180]

next time RTFA
oh, right... this is /.

Geosynchronous orbit?

[mowler2]

The masscentrum of the elevator must lie in the geosynchronous orbit. Does the moon have a geosynchronous orbit around itself (due to the slow rotation, 1 rotation in 20-something days)?

I guess earth lies in its geosynchronous orbit, since we always see the same side of the moon, but an elevator from earth to the moon would be a little bit long, eh? :) (likewise if the elevator is placed on the other end of the moon). Seemes like it is best to start with earth after all?

Re:how to design against terrorists?

[jacksonj04]

Think about this - carbon nanotubes are lightweight and burn up rather nicely. The highest you're going to get to break an elevator cable is a few km above the surface. The bit above the break stays in orbit due to a combination of forces, the bit below will fall and burn if it's high enough to gain enough speed to be dangerous.

And of course if you anchor the elevator offshore (makes most sense for security anyway) then all you're going to get is a splash.

Did Anybody RTFA?!

[TFGeditor]

The comments on this topic make it clear few, if any, RTFA. 90 percent of the comments should be modded "Redundant" since the article answers the very questions posed.

Geekdom sure ain't what it used to be.

Geez you guys

[Rhinobird]

To everyone that says a lunar elevator would be useless right now, did you read the article? He says we can make this thing right now. With current materials, and launch cababilities. All that it needs is money and people to build the flipping thing and it can be done. Now.

And just because it's on the moon and not earth, doesn't mean it can't be quite useful. Imagine being able to send lunar rovers with return capabilities without having to give them heavy expensive fuel for the return trip. Just hop on the elevator and from L1, just a small thruster push and back it comes.

Re:how to design against terrorists?

[barawn]

All modern designs must address not just the engineering (is the cable strong enough) and the economics (is moon dust worth the cost of the elevator) but also acts of terrorism.

A terrestrial cable would be 100,000 km long.

Planes fly at about 10 km.

SpaceShipOne just climbed to 100 km.

Anything a terrorist does to a cable will be done to less than 0.01% of the cable.

Get a clue - terrorists can't do anything more than annoy a space elevator. Anything they can do is recoverable.

Terrorist!

[mangu]

I guess "The Moon is a Harsh Mistress" will be one of the first books to be banished and burned once the revised PATRIOT act goes into effect ;p

But you are absolutely right. Having no atmosphere, the Moon is the ideal place to put a railgun. Besides Heinlein, many other authors have used that concept, among them Gerard K. O'Neill, who popularized the L5 orbit concept.

Doesn't anyone read the actual article?

[Fraser Cain]

I wrote the article, and now I'm reading through the Slashdot comments, and they're killing me. Didn't anyone actually RTFA?!?

Let me clear these up...

1. The cable would be 58,000 km long. This is the distance from the Moon to the L1 point, which is the balance point of gravity between the Earth and Moon. The Earth pulls the elevator straight using its gravity. If you looked at the Moon from the Earth, the space elevator would always be at exactly the same place on the Moon, always pointed directly at us, like we're tugging at it with the Earth's gravity. This has nothing to do with centrifigal force, like an Earth-based elevator where the counterweight keeps the cable taut.

2. Because of low gravity on the Moon, you could build the elevator with commercially available materials on the market today, like Kevlar or M5. The cable would be light enough that it could be launched on a single heavy lift rocket available from Arianespace, Boeing or Lockheed Martin.

One launch = one lunar space elevator

3. You could connect a second cable to the Moon's south pole, so the two cables form a V, and then bring up water ice from the south pole. This would put water, air and rocket fuel into high Earth orbit at a fraction of the price of bringing it up from Earth.

4. As you make the cable longer, it allows you to kick objects into high-Earth orbit. You could transfer materials from the Moon into orbit for relatively little fuel.

Re:Doesn't anyone read the actual article?

[Jetson]

The cable would be 58,000 km long. This is the distance from the Moon to the L1 point, which is the balance point of gravity between the Earth and Moon.

The cable would have to be much longer than that. As the cable is extended toward the surface of the moon, a counter-weight would have to be extended toward the earth so that the elevator's center of gravity would stay at L1 (or else the whole structure would fall to the moon's surface). Once the elevator reached the curface of the moon, the counter-weight would have to be extended yet further in order to offset the weight of the objects traversing the cable. The total length would have to be more than 120,000km.

The concept also doesn't mention coriolis force. The shortest cable would be one that anchors to the lunar surface direcly below L1, however objects travelling on the cable will impart a force onto the cable at 90 degrees to their direction of travel. The base would therefore be best located east or west of the ideal point depending on whether the net traffic on the cable is upward or downward.

Re:Doesn't anyone read the actual article?

[trixillion]

Actually you would want the center of mass to extend just past the L1 point. Assuming the tether is secured to the Moon, then the tether will hold taught because the saddle equilibria about L1 will always being pulling towards the Earth. Surprisingly, this extra tension is all that is necessary to make L1 a point of stable equilibria because the other two dimensions were stable to begin with. I had done very similar research a few years ago on my own and was unaware of Pearson's work, but came to the same conclusions. The Corialis force has to be taken into consideration but so long as this force is kept below certain limits then it has no effect on the overall stability of the system.

Re:Doesn't anyone read the actual article?

[barawn]

This has nothing to do with centrifigal force, like an Earth-based elevator where the counterweight keeps the cable taut.

Sigh. This has everything to do with centrifugal force. It is exactly the same as a terrestrial space elevator. That's why you could build a cable to L4, or L5, even though gravity doesn't appear to balance there at all. It's all about solving the 3 body problem in a rotating frame.

When we talk about a space elevator for Earth, we're talking about building a cable to geosynchronous orbit. At that point, objects orbiting Earth appear to stay above the same point on the Earth's surface because they rotate with the same angular velocity as Earth.

At the L1 point, objects appear to stay at the same point with respect to the Moon because they rotate with the same angular velocity as the Moon. This doesn't happen at the naive calculation that you'd do to get "lunar synchronous orbit" (which is something like half the distance to the Earth) because the Earth is the dominant gravity player in the Earth-Moon system. That's why you have to solve the 3 body problem, whereas for Earth's GEO case, you can ignore the Moon because Earth rotates so fast and Earth is so massive. But centrifugal force does play a role.

However, the cable is an extended object. From an orbital mechanics point of view, the cable stays at L1 because it's in orbit at L1. From the lunar surface's point of view, though, the cable stays upright because it's taut under a large amount of tension, caused by centrifugal force and gravity.

And on a terrestrial cable, the counterweight doesn't keep the cable taut. You don't need a counterweight. You just need the center of mass roughly at GEO.

Let's get some things clear.

[H01M35]

(Yes, some of you already get this.)

The elevator does not go from the earth to the moon.

The moon is not in geostationary orbit around anything. It rotates to keep the same side towards us.

The top of the elevator would be at Lagrange point L1, which is the point at which Lunar gravity and Earth's Gravity are balanced. It is balanced, but unstable. Stationkeeping would be necessary.

People would rarely use the Lunar Space Elevator for personal transport. It would be only for cargo. (Similar to the long awaited Space Elevator from Earth)

No, you can't ride on it.

No, you can't ride on it.

Getting materials off of the Moon is useful. People can explain how it's useful, but it's like lasers when they first came out. They were described (In National Geographic I think) as a solution without a problem.

It would probably be expensive.

It will, however, help make space exploration/development possible.

If we try to justify it economically right away, we will talk (or laugh) ourselves out of it.

Yes, some of these are editorial.

No, that doesn't bother me.

And for those of you who missed it, the article was good too.

The L-Prize

[Baldrson]

This would make a great prize:

$100M for the first kg of lunar material moved, without rocket propulsion, to a Lagrange point.

One end at L1, not the center of mass?

[wasted]

I am not a physicist or rocket scientist, but a few questions pop out:

The cable would be 58,000 km long. This is the distance from the Moon to the L1 point, which is the balance point of gravity between the Earth and Moon.

Wouldn't the cables center of mass need to be at L1 or slightly above (relative to the Moon), rather than the end of the cable? If one end of the cable were at L1 and the other end on the moon, the moon's gravity would have a greater effect than the Earth's gravity, so the cable would be pulled back down to the moon, correct? Or am I missing something?

Re:how to design against terrorists?

[TheLink]

"Anything a terrorist does to a cable will be done to less than 0.01% of the cable"

"Anything they can do is recoverable"

LOL.

Sneak a nice big bomb into a satellite/space vehicle/payload, put it on one of the lifts and blow it up part of the way.

what resources?

[dspeyer]

Mining the moon is of very limited value.

Almost the entire highlands surface is composed of plagioclase. You can extract glass and maybe aluminum from that. You might be able to create dopes silicates for electronics, but you'd probably need to bring trace elements from earth. The Mare are a little better: they're basalt. You can probably get Iron there, maybe some other metals as well. Maybe not. In general, there won't be much in the may of heavy metals, because the moon doesn't have mantle convection and volcanism to make them accessible. It certainly doesn't have hydrocarbons, which we need a lot of.

We could probably mine the moon for a few things, but most of our materials would still come from Earth.