Exactly my point! Please understand that I'm not discouraging research. I'm discouraging things that make no economic sense, such as building things on the moon when it's far cheaper to build them here and ship them up.
Well, I strongly disagree with the ISS having supplies shipped up and down - I think they should be trying to close several of the open loops on the ISS, because in the long run, it's just a waste. That's part of the problem - people are taking much too short of a view on it.
Now, that being said, they are trying to close several loops (water, oxygen, etc.) but money keeps getting cut from those programs because no one expects the ISS to stay up there for very long. Because it's a cash cow. Because it requires resupply. Because it's nowhere near a closed system. Because no one expects it to be there very long....
Then it's buying overpriced materials, as I previously mentioned.
Only unless the upkeep cost makes the cost prohibitive, and if it does, that implies you need to do more research to maintain it with less money.
That's CHNP out of CHONP (the minerals needed for life).
Who said anything about life?
A crazy assumption at this point in time if you know anything about photovoltaic cell construction.
It's not that crazy. There's some research being done into things like this - it's just that there's no real economic incentive other than trivial grants from NASA. Granted, that research is in its infancy - right now they just produce the substrate - but to rule it out as crazy is a little much. Don't you think someone's going to win the Centennial Challenge for oxygen production in the next few years? I'd imagine that shortly after that would be solar cells.
(read Edwards' research on the subject that he did for his space elevator study - it's a small fraction of 1% efficiency).
That's because of size constraints of the climber (you miss portions of the beam). Microwave power beaming back in the 70s (ground-to-ground, granted) was about 56% efficient. The receiver needs to be much larger than the transmitter, for obvious reasons. The efficiency quotes that he had were 50% conversion losses, 30% absorption losses. That's 15% efficient. The remaining loss is due to the inefficiency in beam size.
Cheap space power is a myth for the exact same reason that lunar aluminum is prohibitively expensive until we get cheap access to space: launch costs are just too darn high.
Depends on the lifetime of the satellites, and also upon the expected cost increases of fossil fuels. Most people, when considering expenditures, don't usually take into account the fact that you might also be reducing the trade deficit (and possibly benefitting the local economy in other ways).
Which means that it can be economical for the government to sponsor the program, even if it seems like the program costs more money than it's worth.
Which is why I put a star by it. I couldn't remember offhand what would be the proper name for it. If you treat the entire process as a chemical black box, it's very like a catalyst - something that's needed, but you never really see it. Is there a name for a recoverable reactant?
If you spend 20B$ to produce a 30,000kg/yr lunar aluminum production plant, with maintenance costs of 1B$/yr, you will never, ever repay it even ignoring the costs of getting your materials off the moon.
It depends on where the $20B is spent. If it's spent on the moon, sure, then it needs to be purely amortized, and the cost will look horrendous. But if $19B in research is spent to develop a self-maintaining plant which can be built and shipped to the moon for $1B, which do you quote as the cost? $20B or $1B? What if the technologies developed with that $19B find their way elsewhere into industry (as they inevitably will) that wouldn't've originally been developed?
Also, what if the plant itself uses its own resources to replicate itself? Then the initial seed of $20B, plus $1B a year, can easily repay itself by replicating itself if the replication time is fast enough. It'll need other resources as well, and it may need more from Earth, but if the marginal cost is low enough, it's just a barrier-to-entry.
And, curiously, it's not really surprising that most of your objections come from saying "it's too expensive." Of course it is. We don't have any infrastructure there yet. The first thing that needs to be done is figure out ways to extract resources efficiently. Which is being done.
It's also just ridiculous to say that it will never pay for itself, because you don't know the secondary benefits that are going to come from it. A lunar environment has constraints that don't exist on Earth. We do tons of things here which are stupid, but there are no pressures to do otherwise, and humans are lazy.
We don't do research on closed systems. We just don't care, for the most part, because it's cheaper to do something else immediately. But closed systems (autonomous, self-replicating, and self-maintaining) will almost always win out in the long run. Heck, it's cheaper to lift ISS supplies back and forth rather than try to close food, water, or oxygen. The only thing they even bothered recycling right from the beginning was urine, because it was done on Earth for other reasons.
But, of course, as time goes to infinity, it's always cheaper to have a closed system rather than one that needs to be resupplied. That being said, if the marginal cost of developing the improved efficiency is high enough that it exceeds the resupply cost for, say, the lifetime of the Earth, obviously you're wasting resources.
You only gain low tensile strength (and thus mass) requirements.
Over an Earth-based space elevator, sure! But compared to other lunar launch systems, you gain simplicity and upkeep cost. You obviously don't have the fuel for a rocket launch, but you will have power in spades (assuming you can manufacture solar cells on the moon), and building a many-km long mass railgun is not what I'd consider "easy to build or assemble."
you're looking at 20B$
What, $20B is expensive? Eh. We pissed roughly half a trillion to a trillion dollars back during Apollo, and it's not like we're not pissing away large amounts of money now, too. It's not really "wasted" money, especially considering most of the money will go to US universities and companies. And thus back to the US government itself.
If we spent a ridiculous amount of money on a space power/hydrogen fuel cell infrastructure to replace the foreign oil that we use, it could actually save the government money in the long run by reducing the trade deficit. It's difficult to know what's a "good" idea in the long run unless you know what real pressures you're going to face in the long run.
If you accept that it's unrealistic, why did you mention it?
Because it's currently unrealistic. But your original post made it sound as if you absolutely needed to use the Hall process, which isn't true. If someone's smart enough to find a way to avoid serious corrosion from chlorine, then the subchloride process becomes feasible.
No, it's not. It's a reducing agent. You can recover the carbon, but it is not a catalyst (a component which remains unaltered and unconsumed in its entirity by the reaction)
Carbon's a catalyst (*) in the full process that was quoted. It's a reducing agent in the carbochloride portion of the process, but it's unconsumed in the full process since it's split from the carbon dioxide and recovered.
(*: well, close to one. It at least mediates the reaction and is unconsumed by the process. But it is specifically recovered so I'm not sure it qualifies as a catalyst.)
You're not seeming to understand the concept of amortization, so let me explain.
Geez, you're snippy.
A lunar outpost has tremendous costs to amortize, plus a continously extreme operating cost due to its continual need for imports from Earth
But that's my point. The entire goal of a lunar outpost has to be to minimize imports. That's what all of the Earthside research has got to go into - making a maintenance-free (well, an external maintenance-free) solution.
We can't do it right now because on Earth, labor and space is cheap. There's no economic incentive to do it - heck, we still use humans for construction, which is retarded. But on the Moon, there is. And so most of the initial cost is going to be spent on Earth, trying to figure out how to use the lunar materials as efficiently as possible with as little material from Earth as possible, and how to make them run essentially forever.
Which is what NASA's doing now. Unless you believe that fundamentally, autonomous resource extraction isn't possible, I can't see how you think that in 15 years we won't have significantly advanced our capabilities for lunar resource extraction, especially when we're actively committed to investing in it.
Then there's the issue of lunar launches. Want to get into that
Space elevator to one of the Earth-Moon Lagrange points. You can do it with commercial fiber that exists now. It'd be a large cost to amortize, but there are few recurring costs and the complexity is lower than a railgun.
then clearly the most abundant elements have the highest chance of eventaully hitting the 'jackpot'.
Actually, no - CHON are the most abundant elements in the universe, not on Earth. Many of the other planets in the solar system are poor in one of CHON - Mars is very nitrogen-poor, for instance, and the Moon is very carbon-poor. Earth is tremendously silicon-rich, but we don't use it instead of carbon because silicon wouldn't work.
The reason that they're used for life has more to do with their chemistry than it does their abundance. The reason that they're abundant has more to do with their nuclear properties than their chemical properties.
It is a coincidence. Well, somewhat of one - their chemical properties and nuclear properties aren't independent. That's the answer to the puzzle, not "life uses the most common materials".
ok, now I'm confused. I thought we were talking about geosyncronous orbits, not the space elevator.
I was talking about the space elevator. The original point was why the space elevator needed to go to GEO. It needs to go to GEO (and beyond) because GEO is where your angular velocity is equal to that on the ground. So you don't need any propulsion.
There's no giant pole for the space elevator.
Er? The space elevator is a giant pole. Ribbon, pole, same thing. It's under a ridiculous amount of tension so it's not like it won't be very, very near vertical.
Blood I can understand - there's a fair amount of different blood chemistries out there.
But photoreceptors and energy storage molecules I'm not so sure about. Everything uses ATP and every plant uses chlorophyll. I'm not sure life could really manage in a phosphorus/magnesium poor area.
and nitrogen. Nitrogen's not exactly a minor element with organic compounds.
Other elements (like sulphur for amino acids, or magnesium for chlorophyll) are very, very rare, and I wouldn't be surprised if you could build a full biochemistry with just CHON - just much more inefficient than our current one. The one thing I'm not sure that life could build with just CHON is a photoreceptor - the metal-free pigments all seem to be accessory pigments only. This, actually, is an interesting point - if it's true, without a photoreceptor, life can't evolve until stars have generated enough metals so they're common. A decent molecule to store energy might be lacking, too (no ATP), but the lack of a photoreceptor seems like it could be more fundamental.
The big coincidence, of course, is that if you exclude helium (chemically inert), those four elements are also the most common in the Universe.
I've always wondered whether or not biochemists have tried building artificial biochemistries with other molecules. It's entirely possible purely CHON precursors to chlorophyll, ATP, etc. existed, but were discarded later as they were less efficient.
In addition to dealing with chlorine loss from the system (trace on the moon), subchloride barely works on Earth. Just ask people involved in the Arvida plant, where it corroded the heck out of their equipment. You'll note that there is no longer an Arvida plant.
Which, curiously, was mentioned in the study I linked. Which is why they recommended high temperature electrolysis.
Where do you get your carbon source for reducing?
Carbon's a catalyst in the process. You just need to split it from the carbon dioxide, which does take power, but is feasible. I did link to that article for a reason...
So you want to use even *more* energy?
Apparently, all of our disagreement comes in the fact that I think the first priority is to create a large infrastructure for power on the moon. Once that's there, then the rest becomes a lot more feasible.
Of course we don't know how difficult it will be to create solar power plants on the Moon. We've never done it. And there's no economic pressure on solar cell plants to reduce their size or complexity (because, as you pointed out, capital costs need to be amortized - even on Earth). Once there is economic pressure, the complexity will be greatly reduced. Necessity, and all that.
Yes, an essentially nonexistant company says that they can do it.
That's a little insulting. Apple Computer was an essentially nonexistent company once, as well.
Space is far more hostile than the Pacific Northwest.
And we're a lot more advanced now.
Mir and the ISS are extremely uncomfortable primarily because they're A) cramped, and B) lack gravity, and C) aren't really engineered to be self-sufficient - all the ISS recovers is water from urine.
A permanent lunar base will very likely have a much more advanced recycling setup, almost definitely including atmospheric processing. Which handles all the "smell" complaints.
Er? What makes the idea of a ridiculously large solar array on the moon so far fetched?
Yah, okay, producing the silicon solar panels we have on Earth might be a bit farfetched, but there's a proposal in at NASA to develop in-situ thin-film solar cells. Even without that, though, it's fairly simple to make mirror surfaces out of lunar soil.
I especially don't agree with the blanket statement that energy won't be available. Electricity might require some work, but heat shouldn't be too hard with the Sun out for half a month at a time.
Lets eliminate aluminum from the picture right now...But just to make it more obvious that this won't happen, aluminum refining involves cryolite.
In... the Hall process. There are other processes (subchloride, Toth process, and high temperature electrolysis) which are possible. In the reference below, they recommended the electrolysis, as you did, but it's not the only one.
(for example, I can't even imagine titanium refining on the surface)
Is there a reason you're deriding ideas like these? The idea of a self-replicating lunar base has been around since 1980, when it was proposed (and turned down).
I agree the most important factor is developing a large power infrastructure - but I fail to see how direct solar (for heating) and photovoltaics (for electricity) wouldn't suffice.
The climber's power needs are pure physics unless the efficiency is truely terrible. If no one has thought of it yet: Power = efficiency*Mass*Gravity Coef*d(Height)/dt
Efficiency (both rolling and motor) and mass, as well as their dependence on desired speed, are all dependent on the climber design.
Plus you haven't even addressed reliability.
Several technologies already exist to power the climber without wires.
Do you even comprehend the power requirement for a multi-ton lifter? It's really, really big. Like, megawatt-size big.
SERIOUSLY we aren't even CLOSE. Most business models I have seen have you concentrating on the key technological break-through,
You can't say how close we are to the cable. Nor can you really say what's required, as it depends on how good the cable will eventually get.
It's not like they're not working on the cable, for crying out loud. They're just working on it in parallel. They announced a few months ago (maybe a year...) the construction of a nanotube factory in New Jersey, for one.
For some reason people consider making a strongly-bonded cable of defect-free nanotubes a bigger "breakthrough" than a superreliable, superlightweight, highly efficient robot that can be powered by a ground-based laser and lift a huge amount of weight.
I don't get it. When have we ever built a robot that's traversed 100,000 km with absolutely zero failures? Why do people think this will be easy? Why do people think that this won't take years upon years of slow engineering design? That robot needs to travel up and down that 1500 m ribbon thirty thousand times in order to simulate one trip. And that doesn't even take into account the vacuum and thermal issues!
You only get *realistic* taper factors at over 100GPa.
Incidentally, here is a paper from the research director at LiftPort regarding minimum tensile strength. Taper for a 50 GPa cable is ~10. A 50 GPa cable is very heavy - ~450 tonnes - but it's absolutely not unreasonable. Especially for a government.
50 GPa is still much stronger than current materials, absolutely. But it's far more reasonable than 100 GPa.
"Pretty much" only scores with horseshoes and hand grenades
The Shuttle SRBs shut off at nearly the same altitude as balloons reach. Scientific balloons are up at 40-50 kilometers. At that point, you're above 99.9% of the atmosphere. If you really wanted to, you could get almost arbitrarily high - it's just a question of how large you'd like the balloon to be. Like I said. But you don't use balloons instead of the SRBs, because the SRBs supply humongoid amounts of velocity as well.
To orbit, you have to get all the way out of the atmosphere
To orbit, you need velocity. Whether or not there's atmosphere only tells you how long you're going to orbit for as your velocity bleeds away thanks to air resistance.
Heck, the Space Station is still in the atmosphere, and it's orbiting.
There are a whole host of ways to get things to high altitude, but none of them really work clearly better than rockets because you need velocity - that is, none, save the space elevator, which accelerates very, very very gently over a very, very long cable.
Orbiting tethers, for instance, could pick up a payload off of a balloon-launched payload. That'd get you to a high altitude, but in order to pick up the velocity required, the payload would experience a supremely ridiculous amount of stress when the tether picked it up.
Or you could launch a rocket off of a balloon-supported platform. But again, the stress would be insane because the amount of velocity you need to gain in such a short time is so high.
Or we could build a really, really tall tower. But unless we get out really, really far, that tower won't do a tiny bit of good, because the (angular) velocity you need is so freaking high that, again, the stress would be nuts. Or you'd use a rocket - but the fuel savings on the rocket wouldn't be that large.
The atmosphere is essentially gone by 50 km. It's down 3 orders of magnitude. At 100 km, it's down 6 orders of magnitude. At 150 km, it's down 9 orders of magnitude. But even building a gigantic tower out to 150 km wouldn't significantly help with launching a spacecraft. You'd still need a rocket.
Actually no. At geosynchronous height you still need orbital speed.
Yah, yah, it should've said "angular" velocity there, not velocity. I do, however, commend you on saying that in one paragraph rather than 5 as the other poster did.
The cost savings in terms of delta-v are not enough to justify the ridiculous expense of setting up such a system, not to mention the unbelievable amount of electrical power it would take to run the thing.
Well, the fuel savings would be recurring, and the initial expense is fixed, so it would pay for itself, and the power required really would be negligible compared to the fuel savings cost.
But the fuel savings may not be enough to justify the enhanced stress you're putting the system through.
You could lower the stress by increasing the rail length, but you'd have to increase it by like a factor of 10, which might be pretty much impossible, especially when you consider the fact that the track has to slope upwards pretty much its entire length. Now you're trying to build something that's 10 km long, sloping significantly upwards, and which can support an ungodly huge weight.
It's just not an obvious cost savings. Which is why NASA isn't dumping a bunch of money into it. It could be a cost savings, which is why they're dumping some money into it.
Sure, the angular velocity of an object in geosync is the same as one on the ground, but that means nothing.
Except for the fact that it means you can grab onto something on the ground and use it to let you move faster.
The only reason a space elevator is cheap is because it steals momentum from the earth.
Because the angular velocity is low enough. We steal momentum from the Earth all the time for rocket launches - we launch in the direction of the Earth's rotation (which pushes the atmosphere back, which slows the Earth down).
It's just that at the Earth's surface, the angular velocity required for orbit is way, way higher than what you can take from rotation. At geosync, it's not.
balloons do NOT get above "99.9%" of the atmposphere.
You know, would you please make sure you know what you're talking about first? Because maybe, just maybe, the person you're talking to has built something which went up on a balloon to over 99.9% of the atmosphere. Ever think about that?
And I have, for the record. Technically it was an LDB balloon, but the float altitudes are basically the same. It's just a question of whether or not the atmosphere was pressurized or not.
That site says 99%, but that's actually a little low (they're simplifying it). The height for an LDB flight is about 40 km. Atmospheric density there is about 1 to 2 x 10^-6 g/cm^3. Atmospheric density at ground level is 1.2E-3 g/cm^3.
Dividing, I get that the atmospheric density at float is - gasp one part in a thousand, or 99.9% of the atmosphere is below you.
Do you even have any idea how high up that is?.1% atmosphere is REALLLLLLY high
The intent, as clearly indicated in previous posts, is not to launch something directly into orbit via rail gun.
Did you stop reading there? That paragraph was designed to say "can't launch directly into orbit." The next paragraph was designed to say "this is why launching a rocket this way is bad" - because in the end, you're not saving that much fuel anyway.
I actually left off a sentence there, too - sorry about that. I had intended to say that if you use the railgun to replace the SRBs, you'll only get a weight savings of about 20-30% - because the vast majority of the mass of the Shuttle is in the main tank and fuel, which can't be replaced (because of the first paragraph, which is why that one's in there).
Which means in the end, for a launch system like the Shuttle, railguns would lower the launch mass by 20-30%, while increasing the launch stress by an order of magnitude. This isn't an obvious tradeoff.
which requires more thrust, which requires more fuel, which causes more weight...repeat as needed...is better than a system which adds enegy to the rocket without the rocket having to take it with it
Why? You have to consider that the reason we've had launch failures with rockets are often due to the stress they undergo during launch. Now you're upping that launch stress by a factor of ten. Why is it better to launch less, under more stress, than launch more, under less stress?
Frankly, you're the first person I've *ever* heard say this is a bad idea
I didn't say it's a "bad" idea. It's just not orders-of-magnitude better than normal launches. It's probably comparable to normal launches in terms of the final cost. You seem like you're trying to make it sound as if it's guaranteed tremendously better. It's not.
NASA's previous projects on this (Maglev) were designed to take something up to about Mach 0.8, which would save about 25% of the initial fuel. Unfortunately it would also require 6-10 gees of acceleration, which means that while you need less fuel, you need shock absorption and stronger structural materials. Given that a large number of rocket failures occur due to the stress of a launch at one gee, putting a rocket through 10 gees is not exactly safe.
Let me be clear here. All I'm saying is that electromotive/magnetic launch systems are not clearly better than a rocket launch system. They save fuel and mass compared to a rocket launch system, but they require more stress support, more design safety, and likely more abort mechanisms. In the end, it's not clear that the additional complication of dealing with such a high acceleration are worth the 25% reduction in fuel mass.
If it was clear that it was better, they'd be being built. But they're not clearly better. Which is why they're still in design phases.
Some guy that's clearly in left field on/. or rocket scientists?
How, precisely, do you know that I'm not a rocket scientist?
I'm not, for the record. My advisor, however, is, as are several people I've worked with. And they're where I got those opinions from.
And what's the big deal with "rocket scientist" anyway? You don't want to talk to a rocket scientist. You want to talk to an engineer.
it appears to me that you hold the belief that if you go straight up from the Earth, you'll keep rotating in line with the point you launched from on the surface.
I will if I keep holding onto a giant pole. Which is what this is.:)
You're telling this to a person who's followed every bit of news she can get her hands on about SWNTs (and to a lesser extent, MWNTs and non-carbon nanotubes, plus novel interlinked structures).
Wait, so you do know how to build the cable? You should get in touch with these people!
You took that comment the wrong way - it wasn't meant as "you don't know what you're talking about" it was meant as "since we don't know how to build it, we don't know how hard it is going to eventually be." Unfortunately the two have the same wording.
I encourage you to check out spelsim or the gizmonics calculator. A 50GPa elevator weighs ten times as much as Edwards' calculation, and Edwards' calculation wasn't cheap.
Edwards's calculation was feasible for a business. A 50 GPa elevator would be feasible for a government. And I have checked out spelsim. I know the deal. I just have different views on "feasible" than you do. What was the estimated total cost of Apollo in modern dollars? $200B or so? And the US GDP is 4 times larger than it was then (adjusted for inflation). Feasible for the US, today, is roughly $1 trillion dollars. (*)
*: Now, whether or not it's sane to invest $1T in a space elevator - that's a different matter. Many people would argue that it wasn't sane to invest in Apollo either. I also know if you use percentage of GNP for Apollo - ~3%, and the years it took - ~10, you get about oh, half a trillion or so in current dollars. Close enough for me. And I know the reason we invested in Apollo was for military reasons. Don't shatter my deepfelt optimism that one day we'll invest as much money in exploration as we did in a giant pissing match.
The climbers are.
The climbers are not realistic present-day. Did you read the presentations from the Space Elevator conference on climber design? There were concerns that they might be impossible from power dissapation concerns. And the reliability requirements were way, way above what exists anywhere else.
You can't go out and buy the climbers off the shelf. Therefore it makes sense to figure out exactly how much work they'll need to get working. Which... is what they're doing.
Plus, as I said, the climbers block the development of the power system, since the power system needs to know how much power the climbers need.
Frankly, I'm really baffled by the derision. If it takes 20 years to figure out the cable, then they have 20 years to develop the climber. Which means it costs less per year, so it can be funded via simpler methods - including volunteer time.
Using something like a rail gun has huge advantages which can potentially reduce the weight
In order to seriously reduce the weight, you need to supply a large amount of the velocity. Any additional velocity you want to supply via a rocket also means more weight because you need to carry its fuel.
Let's say you wanted to replace the shuttle launch system. Well, you can't launch something into orbit directly using a railgun. The velocity is just way too high. Not with 10 km of track, not even with 100 km of track. With 100 km of track, you still need an acceleration of ~70 gees to get to escape velocity. That's 70 times higher than the Shuttle at launch, and will kill the crew.
Let's say that you then say, okay, I'll just replace the SRBs. Makes sense. Get rid of the in-atmosphere stage, right? In order to go from the Shuttle to the Shuttle+main tank, you up your weight by a factor of ten. Which means you need ten times the force to do it.
Having said that, the potential is great,
On an airless planet - like the Moon. Not on Earth. For every complicated system it replaces, it requires another one.
I'm not saying it's not possible. I'm just saying it's not nearly as beneficial as you think it is.
Slashdot Mirror
Exactly my point! Please understand that I'm not discouraging research. I'm discouraging things that make no economic sense, such as building things on the moon when it's far cheaper to build them here and ship them up.
Well, I strongly disagree with the ISS having supplies shipped up and down - I think they should be trying to close several of the open loops on the ISS, because in the long run, it's just a waste. That's part of the problem - people are taking much too short of a view on it.
Now, that being said, they are trying to close several loops (water, oxygen, etc.) but money keeps getting cut from those programs because no one expects the ISS to stay up there for very long. Because it's a cash cow. Because it requires resupply. Because it's nowhere near a closed system. Because no one expects it to be there very long....
Then it's buying overpriced materials, as I previously mentioned.
Only unless the upkeep cost makes the cost prohibitive, and if it does, that implies you need to do more research to maintain it with less money.
That's CHNP out of CHONP (the minerals needed for life).
Who said anything about life?
A crazy assumption at this point in time if you know anything about photovoltaic cell construction.
It's not that crazy. There's some research being done into things like this - it's just that there's no real economic incentive other than trivial grants from NASA. Granted, that research is in its infancy - right now they just produce the substrate - but to rule it out as crazy is a little much. Don't you think someone's going to win the Centennial Challenge for oxygen production in the next few years? I'd imagine that shortly after that would be solar cells.
(read Edwards' research on the subject that he did for his space elevator study - it's a small fraction of 1% efficiency).
That's because of size constraints of the climber (you miss portions of the beam). Microwave power beaming back in the 70s (ground-to-ground, granted) was about 56% efficient. The receiver needs to be much larger than the transmitter, for obvious reasons. The efficiency quotes that he had were 50% conversion losses, 30% absorption losses. That's 15% efficient. The remaining loss is due to the inefficiency in beam size.
Cheap space power is a myth for the exact same reason that lunar aluminum is prohibitively expensive until we get cheap access to space: launch costs are just too darn high.
Depends on the lifetime of the satellites, and also upon the expected cost increases of fossil fuels. Most people, when considering expenditures, don't usually take into account the fact that you might also be reducing the trade deficit (and possibly benefitting the local economy in other ways).
Which means that it can be economical for the government to sponsor the program, even if it seems like the program costs more money than it's worth.
This is basic chemistry terminology
Which is why I put a star by it. I couldn't remember offhand what would be the proper name for it. If you treat the entire process as a chemical black box, it's very like a catalyst - something that's needed, but you never really see it. Is there a name for a recoverable reactant?
If you spend 20B$ to produce a 30,000kg/yr lunar aluminum production plant, with maintenance costs of 1B$/yr, you will never, ever repay it even ignoring the costs of getting your materials off the moon.
It depends on where the $20B is spent. If it's spent on the moon, sure, then it needs to be purely amortized, and the cost will look horrendous. But if $19B in research is spent to develop a self-maintaining plant which can be built and shipped to the moon for $1B, which do you quote as the cost? $20B or $1B? What if the technologies developed with that $19B find their way elsewhere into industry (as they inevitably will) that wouldn't've originally been developed?
Also, what if the plant itself uses its own resources to replicate itself? Then the initial seed of $20B, plus $1B a year, can easily repay itself by replicating itself if the replication time is fast enough. It'll need other resources as well, and it may need more from Earth, but if the marginal cost is low enough, it's just a barrier-to-entry.
And, curiously, it's not really surprising that most of your objections come from saying "it's too expensive." Of course it is. We don't have any infrastructure there yet. The first thing that needs to be done is figure out ways to extract resources efficiently. Which is being done.
It's also just ridiculous to say that it will never pay for itself, because you don't know the secondary benefits that are going to come from it. A lunar environment has constraints that don't exist on Earth. We do tons of things here which are stupid, but there are no pressures to do otherwise, and humans are lazy.
We don't do research on closed systems. We just don't care, for the most part, because it's cheaper to do something else immediately. But closed systems (autonomous, self-replicating, and self-maintaining) will almost always win out in the long run. Heck, it's cheaper to lift ISS supplies back and forth rather than try to close food, water, or oxygen. The only thing they even bothered recycling right from the beginning was urine, because it was done on Earth for other reasons.
But, of course, as time goes to infinity, it's always cheaper to have a closed system rather than one that needs to be resupplied. That being said, if the marginal cost of developing the improved efficiency is high enough that it exceeds the resupply cost for, say, the lifetime of the Earth, obviously you're wasting resources.
You only gain low tensile strength (and thus mass) requirements.
Over an Earth-based space elevator, sure! But compared to other lunar launch systems, you gain simplicity and upkeep cost. You obviously don't have the fuel for a rocket launch, but you will have power in spades (assuming you can manufacture solar cells on the moon), and building a many-km long mass railgun is not what I'd consider "easy to build or assemble."
you're looking at 20B$
What, $20B is expensive? Eh. We pissed roughly half a trillion to a trillion dollars back during Apollo, and it's not like we're not pissing away large amounts of money now, too. It's not really "wasted" money, especially considering most of the money will go to US universities and companies. And thus back to the US government itself.
If we spent a ridiculous amount of money on a space power/hydrogen fuel cell infrastructure to replace the foreign oil that we use, it could actually save the government money in the long run by reducing the trade deficit. It's difficult to know what's a "good" idea in the long run unless you know what real pressures you're going to face in the long run.
Personally, I just look at the amount
If you accept that it's unrealistic, why did you mention it?
Because it's currently unrealistic. But your original post made it sound as if you absolutely needed to use the Hall process, which isn't true. If someone's smart enough to find a way to avoid serious corrosion from chlorine, then the subchloride process becomes feasible.
No, it's not. It's a reducing agent. You can recover the carbon, but it is not a catalyst (a component which remains unaltered and unconsumed in its entirity by the reaction)
Carbon's a catalyst (*) in the full process that was quoted. It's a reducing agent in the carbochloride portion of the process, but it's unconsumed in the full process since it's split from the carbon dioxide and recovered.
(*: well, close to one. It at least mediates the reaction and is unconsumed by the process. But it is specifically recovered so I'm not sure it qualifies as a catalyst.)
You're not seeming to understand the concept of amortization, so let me explain.
Geez, you're snippy.
A lunar outpost has tremendous costs to amortize, plus a continously extreme operating cost due to its continual need for imports from Earth
But that's my point. The entire goal of a lunar outpost has to be to minimize imports. That's what all of the Earthside research has got to go into - making a maintenance-free (well, an external maintenance-free) solution.
We can't do it right now because on Earth, labor and space is cheap. There's no economic incentive to do it - heck, we still use humans for construction, which is retarded. But on the Moon, there is. And so most of the initial cost is going to be spent on Earth, trying to figure out how to use the lunar materials as efficiently as possible with as little material from Earth as possible, and how to make them run essentially forever.
Which is what NASA's doing now. Unless you believe that fundamentally, autonomous resource extraction isn't possible, I can't see how you think that in 15 years we won't have significantly advanced our capabilities for lunar resource extraction, especially when we're actively committed to investing in it.
Then there's the issue of lunar launches. Want to get into that
Space elevator to one of the Earth-Moon Lagrange points. You can do it with commercial fiber that exists now. It'd be a large cost to amortize, but there are few recurring costs and the complexity is lower than a railgun.
then clearly the most abundant elements have the highest chance of eventaully hitting the 'jackpot'.
Actually, no - CHON are the most abundant elements in the universe, not on Earth. Many of the other planets in the solar system are poor in one of CHON - Mars is very nitrogen-poor, for instance, and the Moon is very carbon-poor. Earth is tremendously silicon-rich, but we don't use it instead of carbon because silicon wouldn't work.
The reason that they're used for life has more to do with their chemistry than it does their abundance. The reason that they're abundant has more to do with their nuclear properties than their chemical properties.
It is a coincidence. Well, somewhat of one - their chemical properties and nuclear properties aren't independent. That's the answer to the puzzle, not "life uses the most common materials".
ok, now I'm confused. I thought we were talking about geosyncronous orbits, not the space elevator.
I was talking about the space elevator. The original point was why the space elevator needed to go to GEO. It needs to go to GEO (and beyond) because GEO is where your angular velocity is equal to that on the ground. So you don't need any propulsion.
There's no giant pole for the space elevator.
Er? The space elevator is a giant pole. Ribbon, pole, same thing. It's under a ridiculous amount of tension so it's not like it won't be very, very near vertical.
The highest ranked 2 candidates in that list are just 4 ly away from Earth, at Rigil Kentaurus
Rigil Kent is more commonly known by its Bayer designation, Alpha Centauri.
Blood I can understand - there's a fair amount of different blood chemistries out there.
But photoreceptors and energy storage molecules I'm not so sure about. Everything uses ATP and every plant uses chlorophyll. I'm not sure life could really manage in a phosphorus/magnesium poor area.
carbon/hydrogen/oxygen
and nitrogen. Nitrogen's not exactly a minor element with organic compounds.
Other elements (like sulphur for amino acids, or magnesium for chlorophyll) are very, very rare, and I wouldn't be surprised if you could build a full biochemistry with just CHON - just much more inefficient than our current one. The one thing I'm not sure that life could build with just CHON is a photoreceptor - the metal-free pigments all seem to be accessory pigments only. This, actually, is an interesting point - if it's true, without a photoreceptor, life can't evolve until stars have generated enough metals so they're common. A decent molecule to store energy might be lacking, too (no ATP), but the lack of a photoreceptor seems like it could be more fundamental.
The big coincidence, of course, is that if you exclude helium (chemically inert), those four elements are also the most common in the Universe.
I've always wondered whether or not biochemists have tried building artificial biochemistries with other molecules. It's entirely possible purely CHON precursors to chlorophyll, ATP, etc. existed, but were discarded later as they were less efficient.
In addition to dealing with chlorine loss from the system (trace on the moon), subchloride barely works on Earth. Just ask people involved in the Arvida plant, where it corroded the heck out of their equipment. You'll note that there is no longer an Arvida plant.
Which, curiously, was mentioned in the study I linked. Which is why they recommended high temperature electrolysis.
Where do you get your carbon source for reducing?
Carbon's a catalyst in the process. You just need to split it from the carbon dioxide, which does take power, but is feasible. I did link to that article for a reason...
So you want to use even *more* energy?
Apparently, all of our disagreement comes in the fact that I think the first priority is to create a large infrastructure for power on the moon. Once that's there, then the rest becomes a lot more feasible.
Of course we don't know how difficult it will be to create solar power plants on the Moon. We've never done it. And there's no economic pressure on solar cell plants to reduce their size or complexity (because, as you pointed out, capital costs need to be amortized - even on Earth). Once there is economic pressure, the complexity will be greatly reduced. Necessity, and all that.
Yes, an essentially nonexistant company says that they can do it.
That's a little insulting. Apple Computer was an essentially nonexistent company once, as well.
Yah, but it's no fun that you can't stay overnight. What's the fun of going to the best observing spot in the world if you can't use it?
It's like telling people
"Hey, come see Ford Field, site of the Super Bowl (*)"
(*) visitation hours do not include the Super Bowl
Space is far more hostile than the Pacific Northwest.
And we're a lot more advanced now.
Mir and the ISS are extremely uncomfortable primarily because they're A) cramped, and B) lack gravity, and C) aren't really engineered to be self-sufficient - all the ISS recovers is water from urine.
A permanent lunar base will very likely have a much more advanced recycling setup, almost definitely including atmospheric processing. Which handles all the "smell" complaints.
Energy on the moon will be *expensive* as heck
Er? What makes the idea of a ridiculously large solar array on the moon so far fetched?
Yah, okay, producing the silicon solar panels we have on Earth might be a bit farfetched, but there's a proposal in at NASA to develop in-situ thin-film solar cells. Even without that, though, it's fairly simple to make mirror surfaces out of lunar soil.
I especially don't agree with the blanket statement that energy won't be available. Electricity might require some work, but heat shouldn't be too hard with the Sun out for half a month at a time.
Lets eliminate aluminum from the picture right now...But just to make it more obvious that this won't happen, aluminum refining involves cryolite.
In... the Hall process. There are other processes (subchloride, Toth process, and high temperature electrolysis) which are possible. In the reference below, they recommended the electrolysis, as you did, but it's not the only one.
(for example, I can't even imagine titanium refining on the surface)
NASA can.
Is there a reason you're deriding ideas like these? The idea of a self-replicating lunar base has been around since 1980, when it was proposed (and turned down).
I agree the most important factor is developing a large power infrastructure - but I fail to see how direct solar (for heating) and photovoltaics (for electricity) wouldn't suffice.
The climber's power needs are pure physics unless the efficiency is truely terrible. If no one has thought of it yet: Power = efficiency*Mass*Gravity Coef*d(Height)/dt
Efficiency (both rolling and motor) and mass, as well as their dependence on desired speed, are all dependent on the climber design.
Plus you haven't even addressed reliability.
Several technologies already exist to power the climber without wires.
Do you even comprehend the power requirement for a multi-ton lifter? It's really, really big. Like, megawatt-size big.
SERIOUSLY we aren't even CLOSE. Most business models I have seen have you concentrating on the key technological break-through,
You can't say how close we are to the cable. Nor can you really say what's required, as it depends on how good the cable will eventually get.
It's not like they're not working on the cable, for crying out loud. They're just working on it in parallel. They announced a few months ago (maybe a year...) the construction of a nanotube factory in New Jersey, for one.
For some reason people consider making a strongly-bonded cable of defect-free nanotubes a bigger "breakthrough" than a superreliable, superlightweight, highly efficient robot that can be powered by a ground-based laser and lift a huge amount of weight.
I don't get it. When have we ever built a robot that's traversed 100,000 km with absolutely zero failures? Why do people think this will be easy? Why do people think that this won't take years upon years of slow engineering design? That robot needs to travel up and down that 1500 m ribbon thirty thousand times in order to simulate one trip. And that doesn't even take into account the vacuum and thermal issues!
You only get *realistic* taper factors at over 100GPa.
Incidentally, here is a paper from the research director at LiftPort regarding minimum tensile strength. Taper for a 50 GPa cable is ~10. A 50 GPa cable is very heavy - ~450 tonnes - but it's absolutely not unreasonable. Especially for a government.
50 GPa is still much stronger than current materials, absolutely. But it's far more reasonable than 100 GPa.
"Pretty much" only scores with horseshoes and hand grenades
The Shuttle SRBs shut off at nearly the same altitude as balloons reach. Scientific balloons are up at 40-50 kilometers. At that point, you're above 99.9% of the atmosphere. If you really wanted to, you could get almost arbitrarily high - it's just a question of how large you'd like the balloon to be. Like I said. But you don't use balloons instead of the SRBs, because the SRBs supply humongoid amounts of velocity as well.
To orbit, you have to get all the way out of the atmosphere
To orbit, you need velocity. Whether or not there's atmosphere only tells you how long you're going to orbit for as your velocity bleeds away thanks to air resistance.
Heck, the Space Station is still in the atmosphere, and it's orbiting.
There are a whole host of ways to get things to high altitude, but none of them really work clearly better than rockets because you need velocity - that is, none, save the space elevator, which accelerates very, very very gently over a very, very long cable.
Orbiting tethers, for instance, could pick up a payload off of a balloon-launched payload. That'd get you to a high altitude, but in order to pick up the velocity required, the payload would experience a supremely ridiculous amount of stress when the tether picked it up.
Or you could launch a rocket off of a balloon-supported platform. But again, the stress would be insane because the amount of velocity you need to gain in such a short time is so high.
Or we could build a really, really tall tower. But unless we get out really, really far, that tower won't do a tiny bit of good, because the (angular) velocity you need is so freaking high that, again, the stress would be nuts. Or you'd use a rocket - but the fuel savings on the rocket wouldn't be that large.
The atmosphere is essentially gone by 50 km. It's down 3 orders of magnitude. At 100 km, it's down 6 orders of magnitude. At 150 km, it's down 9 orders of magnitude. But even building a gigantic tower out to 150 km wouldn't significantly help with launching a spacecraft. You'd still need a rocket.
Actually no. At geosynchronous height you still need orbital speed.
Yah, yah, it should've said "angular" velocity there, not velocity. I do, however, commend you on saying that in one paragraph rather than 5 as the other poster did.
The cost savings in terms of delta-v are not enough to justify the ridiculous expense of setting up such a system, not to mention the unbelievable amount of electrical power it would take to run the thing.
Well, the fuel savings would be recurring, and the initial expense is fixed, so it would pay for itself, and the power required really would be negligible compared to the fuel savings cost.
But the fuel savings may not be enough to justify the enhanced stress you're putting the system through.
You could lower the stress by increasing the rail length, but you'd have to increase it by like a factor of 10, which might be pretty much impossible, especially when you consider the fact that the track has to slope upwards pretty much its entire length. Now you're trying to build something that's 10 km long, sloping significantly upwards, and which can support an ungodly huge weight.
It's just not an obvious cost savings. Which is why NASA isn't dumping a bunch of money into it. It could be a cost savings, which is why they're dumping some money into it.
Sure, the angular velocity of an object in geosync is the same as one on the ground, but that means nothing.
Except for the fact that it means you can grab onto something on the ground and use it to let you move faster.
The only reason a space elevator is cheap is because it steals momentum from the earth.
Because the angular velocity is low enough. We steal momentum from the Earth all the time for rocket launches - we launch in the direction of the Earth's rotation (which pushes the atmosphere back, which slows the Earth down).
It's just that at the Earth's surface, the angular velocity required for orbit is way, way higher than what you can take from rotation. At geosync, it's not.
not the atmosphere was pressurized or not.
BALLOON was pressurized. Dangit.
balloons do NOT get above "99.9%" of the atmposphere.
.1% atmosphere is REALLLLLLY high
:)
You know, would you please make sure you know what you're talking about first? Because maybe, just maybe, the person you're talking to has built something which went up on a balloon to over 99.9% of the atmosphere. Ever think about that?
And I have, for the record. Technically it was an LDB balloon, but the float altitudes are basically the same. It's just a question of whether or not the atmosphere was pressurized or not.
That site says 99%, but that's actually a little low (they're simplifying it). The height for an LDB flight is about 40 km. Atmospheric density there is about 1 to 2 x 10^-6 g/cm^3. Atmospheric density at ground level is 1.2E-3 g/cm^3.
Dividing, I get that the atmospheric density at float is - gasp one part in a thousand, or 99.9% of the atmosphere is below you.
Do you even have any idea how high up that is?
Yah. 40 km.
The intent, as clearly indicated in previous posts, is not to launch something directly into orbit via rail gun.
/. or rocket scientists?
Did you stop reading there? That paragraph was designed to say "can't launch directly into orbit." The next paragraph was designed to say "this is why launching a rocket this way is bad" - because in the end, you're not saving that much fuel anyway.
I actually left off a sentence there, too - sorry about that. I had intended to say that if you use the railgun to replace the SRBs, you'll only get a weight savings of about 20-30% - because the vast majority of the mass of the Shuttle is in the main tank and fuel, which can't be replaced (because of the first paragraph, which is why that one's in there).
Which means in the end, for a launch system like the Shuttle, railguns would lower the launch mass by 20-30%, while increasing the launch stress by an order of magnitude. This isn't an obvious tradeoff.
which requires more thrust, which requires more fuel, which causes more weight...repeat as needed...is better than a system which adds enegy to the rocket without the rocket having to take it with it
Why? You have to consider that the reason we've had launch failures with rockets are often due to the stress they undergo during launch. Now you're upping that launch stress by a factor of ten. Why is it better to launch less, under more stress, than launch more, under less stress?
Frankly, you're the first person I've *ever* heard say this is a bad idea
I didn't say it's a "bad" idea. It's just not orders-of-magnitude better than normal launches. It's probably comparable to normal launches in terms of the final cost. You seem like you're trying to make it sound as if it's guaranteed tremendously better. It's not.
NASA's previous projects on this (Maglev) were designed to take something up to about Mach 0.8, which would save about 25% of the initial fuel. Unfortunately it would also require 6-10 gees of acceleration, which means that while you need less fuel, you need shock absorption and stronger structural materials. Given that a large number of rocket failures occur due to the stress of a launch at one gee, putting a rocket through 10 gees is not exactly safe.
Let me be clear here. All I'm saying is that electromotive/magnetic launch systems are not clearly better than a rocket launch system. They save fuel and mass compared to a rocket launch system, but they require more stress support, more design safety, and likely more abort mechanisms. In the end, it's not clear that the additional complication of dealing with such a high acceleration are worth the 25% reduction in fuel mass.
If it was clear that it was better, they'd be being built. But they're not clearly better. Which is why they're still in design phases.
Some guy that's clearly in left field on
How, precisely, do you know that I'm not a rocket scientist?
I'm not, for the record. My advisor, however, is, as are several people I've worked with. And they're where I got those opinions from.
And what's the big deal with "rocket scientist" anyway? You don't want to talk to a rocket scientist. You want to talk to an engineer.
it appears to me that you hold the belief that if you go straight up from the Earth, you'll keep rotating in line with the point you launched from on the surface.
:)
I will if I keep holding onto a giant pole. Which is what this is.
I love LiftPort forums.
This pretty much summarizes a lot of what I said, more cleanly.
People are not recognizing the difficulty in building a climber like this. It's just insulting.
You're telling this to a person who's followed every bit of news she can get her hands on about SWNTs (and to a lesser extent, MWNTs and non-carbon nanotubes, plus novel interlinked structures).
Wait, so you do know how to build the cable? You should get in touch with these people!
You took that comment the wrong way - it wasn't meant as "you don't know what you're talking about" it was meant as "since we don't know how to build it, we don't know how hard it is going to eventually be." Unfortunately the two have the same wording.
I encourage you to check out spelsim or the gizmonics calculator. A 50GPa elevator weighs ten times as much as Edwards' calculation, and Edwards' calculation wasn't cheap.
Edwards's calculation was feasible for a business. A 50 GPa elevator would be feasible for a government. And I have checked out spelsim. I know the deal. I just have different views on "feasible" than you do. What was the estimated total cost of Apollo in modern dollars? $200B or so? And the US GDP is 4 times larger than it was then (adjusted for inflation). Feasible for the US, today, is roughly $1 trillion dollars. (*)
*: Now, whether or not it's sane to invest $1T in a space elevator - that's a different matter. Many people would argue that it wasn't sane to invest in Apollo either. I also know if you use percentage of GNP for Apollo - ~3%, and the years it took - ~10, you get about oh, half a trillion or so in current dollars. Close enough for me. And I know the reason we invested in Apollo was for military reasons. Don't shatter my deepfelt optimism that one day we'll invest as much money in exploration as we did in a giant pissing match.
The climbers are.
The climbers are not realistic present-day. Did you read the presentations from the Space Elevator conference on climber design? There were concerns that they might be impossible from power dissapation concerns. And the reliability requirements were way, way above what exists anywhere else.
You can't go out and buy the climbers off the shelf. Therefore it makes sense to figure out exactly how much work they'll need to get working. Which... is what they're doing.
Plus, as I said, the climbers block the development of the power system, since the power system needs to know how much power the climbers need.
Frankly, I'm really baffled by the derision. If it takes 20 years to figure out the cable, then they have 20 years to develop the climber. Which means it costs less per year, so it can be funded via simpler methods - including volunteer time.
Bleah, that last part is wrong. It's like 9000 miles per hour.
Using something like a rail gun has huge advantages which can potentially reduce the weight
In order to seriously reduce the weight, you need to supply a large amount of the velocity. Any additional velocity you want to supply via a rocket also means more weight because you need to carry its fuel.
Let's say you wanted to replace the shuttle launch system. Well, you can't launch something into orbit directly using a railgun. The velocity is just way too high. Not with 10 km of track, not even with 100 km of track. With 100 km of track, you still need an acceleration of ~70 gees to get to escape velocity. That's 70 times higher than the Shuttle at launch, and will kill the crew.
Let's say that you then say, okay, I'll just replace the SRBs. Makes sense. Get rid of the in-atmosphere stage, right? In order to go from the Shuttle to the Shuttle+main tank, you up your weight by a factor of ten. Which means you need ten times the force to do it.
Having said that, the potential is great,
On an airless planet - like the Moon. Not on Earth. For every complicated system it replaces, it requires another one.
I'm not saying it's not possible. I'm just saying it's not nearly as beneficial as you think it is.