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LiftPort Wants To Build Space Elevator On the Moon By 2020
Zothecula writes "When the late Neil Armstrong and the crew of Apollo 11 went to the Moon, they did so sitting atop a rocket the size of a skyscraper that blasted out jets of smoke and flame as it hurtled skyward. For over half a century, that is how all astronauts have gone into space. It's all very dramatic, but it's also expensive. Wouldn't it be cheaper and easier to take the elevator? That's the question that Michael Laine, CEO of LiftPort in Seattle, Washington, hopes to answer with the development of a transportation system that swaps space-rockets for space-ribbons. LiftPort ultimately wants to build a space elevator on Earth, but the company isn't planning on doing it in one go. Instead, Laine and his team are settling for a more modest goal – building an elevator on the Moon by 2020. This is much easier. For one thing, there’s no air on the Moon, so no icing problems. Also, the lower gravity means that no unobtainium is needed for the ribbon. Kevlar is strong enough for the job. And finally, there’s very little in the way of satellites or debris to contend with."
That problem is that there is no way to create a lunar-centric orbit where the upper terminus of the ribbon hovers over a fixed position. So any tether can not be fixed to the ground. So lifting anything with that tether will involve something like a skyhook catch, except it will be at orbital velocities.
They're forgetting the single most important part of a space elevator: It needs to actually be useful.
What are we going to do with a space elevator on the moon? We don't go there for a very good reason: Its expensive as hell. Making the cheap and easy part a little cheaper an easier isn't going to change the fact that the entire rest of the trip is prohibitively expensive.
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Wouldn't we need to get back to the Moon, establish some sort of colony there, and create the industry and infrastructure just to build such a thing in the first place? I can't see this all happening in the next 8 years.
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Well I'm not so sure... It would make transport on and off the surface cheaper. This would in turn make it more economical to conduct mining operations on the the moon--which is presently our easiest to access source of Helium-3.
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They said Space elevator. Space elevator "orbiting the moon" are your words. This link shows exactly what they are attempting to do: http://www.gizmag.com/lunar-elevator/23884/pictures#2
The moon does not rotate. When you look at the moon the same side of the moon always points to the earth. So, the ribbon would need to be held stable by Earths gravity to some extent (it seems).
Our moon does rotate, with a period equal to its revolutionary period about the earth. This kind of synchronization is common with moons of planets, and is caused by tidal forces between the moon and the planet.
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My orbital mechanics sucks, but apparently smarter people have thought this through. It's not as intuitively simple as a tether between the Earth's equator and a geostationary satellite, but the physics does work:
http://en.wikipedia.org/wiki/Lunar_space_elevator
My issue is that this is yet another fancy space project that presupposes an earth to high-orbit launching capability we don't have, nobody is seriously working on, and would seem to require more financial support than anybody has the will to deliver.
If somebody can crack this nut, then we can start talking about lunar space elevators, missions to other planets, and other fun stuff. But until that happens, all these fancy proposals are just so much hot air.
A lunastationary orbit would have a radius of ~384400 km (the distance from Earth to the Moon).
If you put the upper point at L1 or L2, you'll still have to put an anchor farther out to keep tension on the cable. Which may or may not be really useful, but it's an interesting idea, anyway.
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Space elevators also allow you to bring things gently DOWN from orbit. How's that mass driver gonna work for ya?
It could work quite well. Mass drivers can decelerate as well, and can recover and convert the kinetic energy to electricity in the process.
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There's plenty worth lifting off the moon, if we can do it. There's water for starters, plus plenty of raw materials for making high quality metals, ceramics, semiconductors and so on. If you can send them into a low Earth orbit then you'll probably find you can beat the per-kilo costs of launching similar material from Earth, what with the big gravity well and atmosphere and all. If you can undercut an entire planet then I'd call that a worthwhile business opportunity. Can't see how a space elevator helps much, but there's plenty worth lifting off the moon.
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You put LiftPort on the front page and forget their KickStarter campaign?
It started on the 23.08, and in 5 days it's raised $27.514 of the 8000 goal.
http://www.kickstarter.com/projects/michaellaine/space-elevator-science-climb-to-the-sky-a-tethered
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The mining machines wouldn't necessarily need to be: massive, transported via the tether, and/or come down fully assembled. Not everything has to start out on massive scales. For instance consider the state of global shipping back in the 18th century then compare that to the early 21st. Or farming in the 18th vs. 21st. Normally things start out small and gradually build out as technology and resources develop. Staging things is simply an engineering problem which if Curiosity is any indicator we seem to be getting pretty good at. Even during the Apollo missions we were dropping some pretty serious hardware down onto the moon. Powering these machines can come from any number of technologies from mundane to exotic. We already have well proven solar and RTG technologies, there are a few rather interesting possibilities using in-situ resources as well. For instance using the newly discovered water with the aluminum in the regolith to produce hydrogen for fuel. The Aluminum Hydroxide byproduct has its own interesting uses. The obvious one is of course simply using the mined He-3 for fusion power (whenever we get that one figured out).
Few grand adventures into human frontiers are ever "practical" initially and that unfortunately prevents people from seeing what humanity's pioneers and explorers see. In the 1800's no one got what Charles Babbage saw. During the first half of the 1900's very few saw what Konrad Zuse saw. Today no one can miss it and everyone demands it. People too often are quick to see problems as "too hard", too near-sighted to see possibilities, too self-centered to appreciate the benefits to others. You might not get to holiday on Utopia Planitia, or sail the methane seas of Titan but wouldn't it be awesome to initiate the projects now that make that a reality for your progeny? Both incomprehensible business opportunities and human delights await us on this next frontier. What are we waiting for?
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It will certainly be a much cleaner, albeit hugely expensive, non-feasible fuel for the fusion reactors we won't be able to build in 2050 than the cheap and readily available non-feasible fuel we can't extract from ordinary seawater for the fusion reactors we can't build right now.
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Indeed, to be stable the elevator would have to be "stationary" within the rotating Earth-Moon frame, with the top extending past either the L1 or L2 point (towards or away from the Earth) far enough that the force of it "falling away" from the moon would be sufficient to counteract the weight of the cable itself.
Calculating the exact distance of the L1 and L2 points can be difficult, but so long as the masses are significantly different they are at approximately the Hills Sphere radius from the smaller mass M2 at r = R (M2 / 3*M1)^1/3. For the earth-moon system that is about 60,000km from the moon, versus the 36,000 km from Earth that constitutes geostationary orbit. So the elevator would have to be about 60% longer than on Earth, but the much lower gravity means it could be far thinner and weaker, and thus easier to build. Even perfect carbon nanotubes barely have the strength-to-weight ratio necessary for an earth-based elevator, with no room for a safety margin.
Plus for the immediate future at least the liability is much lower on the moon - a failure that drops 60,000 km of cable onto the moon from orbit is unlikely to be a problem beyond the fact that your very expensive elevator is now scrap. Drop 36,000 km of cable onto Earth, enough to to wrap almost all the way around the planet, and you're going to have a heck of a lot of secondary damage.
Personally I prefer the idea of the "tumbling cable" elevator - take just a few hundred kilometers of cable orbiting while tumbling end-for-end with the tips coming down almost to the surface like opposing spokes on a wheel rolling along the Moon's equator and you've got an elevator that will match speeds with various points on the equator on a regular basis, coming almost straight down before momentarily stopping and then hauling snagged payload up at roughly 1/4g. By the time the payload reaches it's highest point it will be moving sufficiently fast to easily escape the Moon's gravity, and depending on the particular orbital trajectories of the cable and Moon at the moment of release, moe than enough to escape the Earth's as well, even to put it on a Hohmann transfer orbit to Mars or Venus. Granted all that extra energy means it's not ideally suited to Earth-Moon transfers, but it sure would be a lot smaller and easier to build (except for the necessary drive system to recharge the angular momentum transferred to the payload), as well as making the Moon a major waystation to our much more interesting planetary neighbors.
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Who needs speed? The elevator would still let you drop big rocks on Earth - sure they're moving slow relative to the top of the elevator when you let them go, but the entire moon is moving at about 1,000km/s relative to the Earth, and once those rocks have fallen the remaining couple hundred thousand kilometers to Earth they'll be moving even faster, more than enough to do massive damage wherever they're aimed. We *might* be able to shoot them down, assuming were willing to expend a space-capable nuke against it, were able to hit the thing given the massive speed it's traveling at (shouldn't be *that* hard to basically stand in it's path), and preferred to have radioactive slag come raining down over a wide area rather than letting the rock vaporize it's target. Of course if several rocks were dropped at once that would be far more difficult.
That's the one big problem with a space-based economy - once you're moving heavy stuff around in orbit *everything* becomes a high-yield weapon, and there's not much anyone on Earth can do to defend against it. It's like the ultimate version of trapping your enemy in a narrow canyon where you can fire down at them from all sides. And if an Earth-moon war should ever break out, well the Moon is almost guaranteed victory - both sides will see any incoming weapons a long way out with plenty of time to intercept - but hitting the Moon requires high-energy launches, while launching from the moon requires only ~1/25 the energy (~1/5 the escape velocity) so they can just throw rocks all day long for the cost of launching one missile, and any debris from intercepted weapons in either direction is far more likely to fall back to Earth than hit the moon.
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Seriously, name one thing that's on the moon that you think is worth trillions of dollars, keeping in mind that its surface is entirely covered in rocks.
Rocks in space.
Seriously, look at the price of titanium on earth - about $7 US per kg for commodity ferro titanium. Look at the price of titanium in low earth orbit - according to Wikipedia, it costs about $4300 US per kg using a Proton rocket (the cheapest non-subsidized launch method listed). There's quite a lot of titanium on the Moon, as well as aluminum, iron, and magnesium.
That's why we want to mine asteroids and the Moon - getting material out of the Moon's gravity well is a lot easier than getting it out of Earth's gravity well (and of course asteroids generally don't have an appreciable gravity well).
If we want a space station that's more than just a few tin cans glued together and can protect its inhabitants from radiation, we need building materials. We can get many of those materials from the Moon. We'd have to learn how to process and smelt them there first, of course, but you have to start somewhere.
He3? Well, maybe later. You don't build a gas station before the invention of combution engines. Water is more valuable, if it can be collected in any serious amount, which we still don't know.
That said, I have my doubts that anyone could put a space elevator on the moon in 8 years. It's just not going to happen. The design phase would take at least half that time.
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