AsteroidMining writes:
"After the terrestrial space elevator (which cannot be built with existing materials) got a little press, Space.com has focused on the Lunar Space Elevator (which can be built with existing tether materials, such as Zylon string), based on the LiftPort Group's plans to build one. In the article, Charles Radley (a LiftPort adviser) lays out the case for opening the Moon to commercial development using a Space Elevator. He says it represents 'game-changing technology' and that 'the lunar elevator could reduce the cost of lunar mining of some commodities to a par with terrestrial mining.'
In the interests of full disclosure I am involved in the technical design of the LiftPort Lunar Space Elevator and would be glad to discuss it here."
(Score: 5, Interesting) by Fluffeh on Wednesday March 05 2014, @10:36PM
From my understanding of a space elevator, they are big. Like REALLY big. While we might have the technology available to us right now to build one in a lower gravity well such as the moon, wouldn't it be pretty much impossible to actually LIFT that amount of material out of the earth's gravity well to get it constructed on the moon in the first place?
(Score: 0) by Anonymous Coward on Thursday March 06 2014, @04:34AM
We don't have the technology to lift the entire ISS into orbit in one go, either.
(Score: 5, Informative) by AsteroidMining on Thursday March 06 2014, @10:15AM
The "default" prototype LiftPort Lunar Space Elevator (LSE) (which is at this point primarily a reference for further engineering studies) is indeed big, 278,544 km long. It is, however, not that massive. The default model is sized to a single launch of the SLS, with a string mass of 41,761.6 kg and a total mass sent to the Lagrange Point of 48,700 kg (not counting the SLS upper stage, which is not thrown away but used as part of the counterweight*).
The string is thus very thin (the area is at no point > (1 mm)^2). The maximum force on the string is only 517 Newtons; if you can pick up a 50 kg sack here on Earth, you could hold this LSE together, at least for a little while.
This prototype design has a payload mass of 128 kg, and so (with a climber mass of 50 - 75 kg) could deliver or pick up 50 - 75 kg of material in a single trip, and maybe 2 or 3 times that in a month in the beginning. The challenge will be to send / retrieve enough value to make it worthwhile to expand the elevator's capacity.
*In space elevator design, you can trade length for counterweight mass. More counterweight means you need less string.
(Score: 0, Troll) by EvilJim on Wednesday March 05 2014, @10:45PM
LiftPort's concept for building the lunar space elevator infrastructure calls for using a climbing vehicle that scoots up and down a ribbon-shaped, tethered cable that's part of an anchor station secured to the airless moon.
do they realise the moon orbits the earth? you cannot teather both ends unless you want to fuck up the tides and test the strength of the teather. or are the going to let the earth end roam free and whip violently through cities then attempt to catch it at the moment it whips past their pickup station?
(Score: 0) by Anonymous Coward on Wednesday March 05 2014, @10:48PM
> do they realise the moon orbits the earth?
I'm sure they will adjust their plans once they realize that!
(Score: 2) by EvilJim on Wednesday March 05 2014, @11:04PM
ha, despite convention, I actually read the rest of the article after posting the quote and quip above and they're talking about having a pico gravity station at the end of the tether whipping around the earth, hopefully at higher than city altitude but that still leaves you with all the risk of a rocket exploding while trying to get your cargo to and from the pico gravity station so they'll make it marginally cheaper on the fuel side but still with the exact same risks we have with current rocket delivery methods. I think a tether attached to the earth and whipping around leo or further out sounds theoretically better.
(Score: 2, Insightful) by mattyk on Wednesday March 05 2014, @11:17PM
The goal isn't to make getting to the moon cheaper, it's to make getting _from_ the moon cheaper. I.e. mining. It's probably relatively easy to set up dumb drop-shops to spam materials onto the terrestrial surface from space. Save the more careful, more expensive trips for the ones with people on board.
Once we invent super magic strong-rope we can set up our terrestrial elevator, and *then* we can talk about cheap two-way traffic.
(Score: 3, Funny) by EvilJim on Wednesday March 05 2014, @11:21PM
can we vote on where these drop-shops are going to be located? or at least make a few 'mistakes' in the calculations? I know a few good places to hurl some crap from space onto.
(Score: 1) by mattyk on Wednesday March 05 2014, @11:09PM
It's tethered to the moon, not to the earth. You should scroll down a little in TFA (there's even a picture!)
(Score: 3, Funny) by EvilJim on Wednesday March 05 2014, @11:23PM
come on, that flies in the face of convention... reading TFA I'm talking about. :) I like to be well uninformed when making snap judgements.
(Score: 1) by SlimmPickens on Wednesday March 05 2014, @11:58PM
I just want to point out this isn't as stupid as it sounds. While the Loony elevator isn't going to be whipping past cities or even geostationary satellites, it does stretch more than half way back to Earth and therefore could interfere with an Earth-based elevator.
(Score: 2) by EvilJim on Thursday March 06 2014, @12:15AM
I beg to differ, I'm far stupider than I sound.
(Score: 3, Informative) by romlok on Thursday March 06 2014, @04:53AM
But it still comes nowhere near Earth geostationary orbit. An Earth-based space elevator needs to have its centre of mass around GEO, so it only needs to stretch an equal distance beyond GEO to remain stable - and that's only if the mass beyond GEO is entirely ribbon material, with no counterweight used.
According to the diagram in the article, the moon-elevator is planned to come to about 135,000km from Earth. GEO is about 36,000km, so that leaves a likely minimum separation of over 60,000km distance between the two elevator ends.
(Score: 1) by SlimmPickens on Thursday March 06 2014, @05:45AM
Fair point, however if we had some very special cables we might want them longer so we can fling stuff around the solar system.
(Score: 1) by wonkey_monkey on Thursday March 06 2014, @03:43AM
Who said anything about tethering the other end to the Earth?
(Score: 3, Interesting) by carguy on Thursday March 06 2014, @09:09AM
> Who said anything about tethering the other end to the Earth?
With a tall enough tower, you could tether from a point above the South Pole (of Earth) to the moon. Requires a very strong pivot and tether-length-adjuster on top of the tower...North Pole is the other option, but would have to be anchored to the sea bottom with ice moving on the surface.
Too bad the Earth's axis of rotation is tipped 22-odd degrees to the Lunar orbit.
(Score: 2, Interesting) by AsteroidMining on Thursday March 06 2014, @10:34AM
No, you could not have a static elevator going from the Earth to the Moon; that is not what is being discussed here. The LSE would be long, but it would not come close to the Earth.
The far end of the elevator would be in cisLunar space, held taut by the Earth's gravity (the tidal force). Once you get sufficiently far from the Moon along the elevator (~ 220,000 km), sending something to Earth is simply a matter of letting it go (it will re-enter the Earth's atmosphere 1.4 days later).
The Phobos Anchored Mars Space Elevator (PAMSE) would have a relative velocity (on average) of 550 m / second, or about Mach 1.2, at the Mars end (the tip would also rise and fall about 200 km each orbit due to the eccentricity of the Phobos orbit). This elevator would actually be technically easier to build than the Lunar Space Elevator (well, except that Mars is so blasted far away), but figuring out how to best get material from the surface to the elevator is an interesting puzzle.
(Score: 1) by Grishnakh on Thursday March 06 2014, @11:30AM
They want to build a space elevator on Mars using Phobos as a counterweight? According to my reading of Wikipedia, Phobos, while ridiculously small for a moon (so small it isn't even round), isn't *that* small; its surface area is about the same as the state of Delaware. It also orbits the planet faster than the planet spins on its axis, so the big challenge is you'd need to slow it down some. I don't see how we'd be able to have a significant effect on something with a mass of 1E16kg with our current technology.
(Score: 2) by EvilJim on Thursday March 06 2014, @05:17PM
besides that, the aliens residing inside Phobos would be pissed! just look at what they did to that probe that got too close.
(Score: 2) by EvilJim on Thursday March 06 2014, @05:21PM
I love how I got modded troll for this, there are some fantastically educational comments coming out of it.
(Score: 2, Interesting) by rich0 on Wednesday March 05 2014, @10:56PM
If you actually built a lunar space elevator capable of lunar escape velocity you could basically hurl boulders at anything on earth with incredible velocity. Granted, it would only be useful against fixed targets as you'd have days to dodge incoming fire. However, if your goal was to level a general region you could just shotgun it with rocks from heaven.
(Score: 5, Informative) by Fluffeh on Wednesday March 05 2014, @11:51PM
You might enjoy watching a show called Babylon 5. Pay close attention during the Centauri, Narn war. Centauri spaceships tow asteroids (tens to hundreds of meters in size) in from the Narn homesystem asteroid belt towards their home planet and basically untether them to drop onto surface targets. Don't worry about missiles, nukes or bombs. The velocity of the impact does the same thing a LOT more cheaply.
(Score: 3, Informative) by AsteroidMining on Thursday March 06 2014, @10:36AM
"The Moon is a Harsh Mistress," R.A. Heinlein (1966).
(Score: 2, Interesting) by anubi on Wednesday March 05 2014, @11:02PM
Since you indicated you are in on the design team of this thing... what I am concerned with is geostationary orbit of the spaceborne end of the elevator.
How high is this for the Moon? ( For reference, the geostationary orbit is 22,236 miles above the equator on Earth. You will find things like DirectTV satellites there.. so that people can put their dish on the roof of their house, point it, and leave it. )
I take it you intend to use some of the rotational inertia of the moon to provide the energy to lift the payload, as inserting the payload into orbit not only requires the force against gravity to lift it to elevation, but also the kinetic energy to accelerate it to escape velocity, which as I understand is how fast the object has to travel so that the centrifugal force exerted on it exactly cancels the gravitational force the moon exerts on it. I would think a small angle ( from perpendicular to surface ) on the tow rope between the moon and its spaceborne receiving platform would transmit the force to accelerate the payload. ( this would infer the spaceborne end is higher than geostationary orbit and is actually being held in place by this tether. )
This sounds like quite an interesting project to work on. I envy you. I ended up working for an aerospace company that got bought out by an investment group and had the RadioShack thing happen. All the top brass seemed to have their eye on margins and bonuses, and all the excitement and thrill of actually doing something new and creative became something that, if you were lucky, was tolerated. Many of did not last long under that kind of environment - some of us never returned to doing anything useful.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 2, Interesting) by anubi on Thursday March 06 2014, @12:05AM
Still looking at your article...I am still confused on something... maybe you can clear it up?
We can say the moon is in orbit around the Earth. Would the statement that the Earth is in orbit around the moon also be appropriate, given you are standing on the moon as a point of reference? Now, I know I have made a mess of celestial mechanics by stating such as the Earth has far more mass than the moon and I have committed my own point of reference to one heck of a spirally path in relation to everyone else in the solar system... but for now I am only considering my relationship to Earth.
The same side of the moon faces the earth at all times? Would that imply that if I stood on the Earth-facing side of the moon, the Earth would not appear to move? I could see the Earth rotating, but it would not rise or set as we on Earth see the moon rising and setting against the horizon.
If the Earth was indeed in the same place in the "sky of the moon", much like a DirectTV satellite is in the same place in the sky of the Earth at all times, would that not imply the Earth is in a geostationary orbit around the moon?
I do not believe the mass of an object influences the distance to geostationary orbit... that is both a basketball and a freight train in a geostationary orbit would be at the same altitude?
But you would not want to tether to the Earth, because unlike seeing the same face of the moon from Earth, the Earth is spinning and would quickly wind up and "reel in" any tether you attempted to attach?
Yet, in order to provide a bit of tension on the tether, so that you do not have to continually provide thrust to counter the effect of gravity, you would have to station the receiving end of the tether beyond geostationary orbit - so that the centrifugal force would exceed gravitational force ( such force being a tension on the tether )?
The only alternative I see is continually fueling some provider of thrust to maintain tension. That's gonna get expensive.
I likely have a misunderstanding somewhere... can you show me what I am missing?
Now, if we could spin the moon up a bit, which would lower the geostationary orbit, it looks do-able to me.
( I am going for illustration here and do not mean to be funny ) If I spun the moon up enough, I could lower the geostationary orbit all the way down to the moon's surface, at which point rocks and whatever on the moon's surface would literally float away and be flung off into space...
But its that thing about having the same face of the moon facing me on Earth at all times that has me confused on this approach... there is likely something I am not seeing.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 1) by maxim on Thursday March 06 2014, @01:39AM
Geostationary orbit is impossible high on the moon, however there is earth around which makes things possible. instead of tethering to GEO (or shall I say LEO), its possible to tether to L2 point between earth and the moon (point between earth and moon where gravity of both cancel out) and its both close enough to moon and good to transfer goods from it to the earth.
On earth you could theoretically also use earth/sun L2 point but I guess its further away that geostationary orbit distance is.
(Score: 3, Informative) by anubi on Thursday March 06 2014, @02:43AM
Thanks!
Now I understand. That long tether shown in the diagrams is simply to drop into Earth's gravity well so they can use Earth's gravity to provide the force to hold the receiving platform aloft. I knew there was something I wasn't seeing... that was it.
Finally, now it all makes perfect sense to me. That's gonna be one very long rope!
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 2, Interesting) by AsteroidMining on Thursday March 06 2014, @10:46AM
It is not geostationary orbit. The Lunar Space Elevator is primarily held taut by Earth tides, not rotation (centrifugal force).
The equivalent points to a geostationary orbit are the Earth-Moon Lagrange Points 1 and 2 (EML-1 and EML-2), that leads to a possible near side elevator and a far side elevator. For the Near Side Elevator, EML-1 is (on average) 56,283 km from the mean Lunar surface. When you get to that altitude, you are in orbit, and could just float off the elevator platform.
I came up with the idea for a "picogravity lab" in that location; it would be orders of magnitude quieter than the ISS, as drag would be totally absent, and sunlight almost continuous.
(Score: 1) by anubi on Thursday March 06 2014, @09:42PM
That's a beautiful design, Asteroid!
I have a question about a scenario. Let me define two objects.. one I will call a "mass" which is to be lowered into Earth's gravity well via the tether, thereby recovering some energy, which is to be used to lift the "load" from the moon.
When that first object, "mass" reaches the end of the tether, and should it be released, would that mass go into some sort of orbit around the Earth, or would it drop on into Earth? My gut feeling is that the released mass would assume an elliptical orbit of Earth, but I have not run the numbers ( actually I am quite ignorant in this arena and do not even have anything to run them on! ).
This whole concept makes me think of it as a "mass syphon" pump. Very ingenious.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 1) by laserfusion on Thursday March 06 2014, @09:00AM
and,
Maybe other launch costs from Earth can be reduced with this too. Cheap on-orbit refuelling could be made possible with fuel supplied from the moon. In some kind of reusable system.
The boost in rare earth elements mining and raw materials will also surely have positive effects on the economy.
(Score: 1) by dargaud on Thursday March 06 2014, @09:15AM
In a fist step, I'd like to see a proof of concept in the form of a satellite with 4 parts: the ribbon (or wire), a ground anchor, the counterweight and a climber. Make it as small as possible so it can all be launched by conventional means as a one-shot mission. This would test several crucial techs, in particular unspooling the cable in space, anchoring, dynamically placing the counterweight, etc... I wonder if this is possible with a, say, 10 ton payload from Earth. It doesn't matter if the climber can't have a payload.
Once you can do that, then yes, build a real one to bring back... err, dust from the moon.
(Score: 2) by Grishnakh on Thursday March 06 2014, @11:34AM
I don't see how you can build a "proof of concept" without actually building a real space elevator. As I understand it, the typical SE design actually calls for starting out with a very thin ribbon, then after getting that in place using that to add some more ribbons for redundancy or extra capacity.
(Score: 0) by Anonymous Coward on Thursday March 06 2014, @10:05AM
Laine's credo on the group's website: "There is a profound difference between difficult, very, very hard, and impossible."
There are profound differences between "difficult", "very, very hard", and "impossible".
(Score: 1) by germanbird on Thursday March 06 2014, @06:47PM
I've always thought space elevators were a cool concept and I don't doubt that the research being done for this is worth it, but what is the benefit here? Is reaching escape velocity for the moon that costly of a venture? Are there other things besides fuel costs that I'm not thinking of that this helps with?
(Score: 1) by G-forze on Friday March 07 2014, @07:39AM
How about getting the fuel to the moon to begin with? And if you produce the fuel on the moon, hauling it up to the Galactic Gas Station at L1 nearly for free would be no small thing.