Posted on 01/16/2006 9:53:39 AM PST by Paul Ross
> The overwhelming reason space elevators are (in theory) far less expensive than rockets is because rockets have to accelerate their propellant with them. That's it.
Tell me: how does the payload get up the elevator? Seems to me that a beamed-energy system is needed to power the climber. Where does the energy come from? Who builds and maintains the laser, and how much do they get paid? How much energy *total* is required to climb up to GEO, and how does that compare to the energy requirements for a rocket?
You're the only one I've seen making the argument that lifting will be just as expensive with a space elevator as with the controlled explosions burning up chemical rocket fuel propelling things to orbit. I've read a great deal about the concepts to include items from NASA engineers and other engineers and no one makes the argument you're making. Given what I've gathered I must disagree with your assessment. The whole reason that NASA and others are looking at space elevators is the reduced cost of getting material to orbit.
Read the rest of the Wiki entry. I also urge you to read up on the subject. A simple Google search will lead you to several papers from NASA and other organizations.
The beamed energy system is one proposed method of powering a crawler. There are other methods. The amount of energy is simply the amount needed to mechanically pull the weight the distance required. Are you putting forth the argument that it would cost the same to move a certain amount of weight by train as it would to by rocket launch? That is really the comparison here.
> You're the only one I've seen making the argument that lifting will be just as expensive with a space elevator as with the controlled explosions burning up chemical rocket fuel propelling things to orbit.
I'm not makign that arguement. I'm simply pointing out that this technology is not a panacea, and has definite limitations. It is, for example, *worthless* for quick-response systems or military applications and the transportation of heavy items.
I never proposed that it could be used for quick-response systems. However, it is far more efficient at moving heavy objects to orbit to include weapons platforms for the military.
>> Tell me: how does the payload get up the elevator? Seems to me that a beamed-energy system is needed to power the climber. Where does the energy come from? Who builds and maintains the laser, and how much do they get paid? How much energy *total* is required to climb up to GEO, and how does that compare to the energy requirements for a rocket?
>Read the rest of the Wiki entry.
Non-responsive. I was hoping to see if *you* have in fact studied up on the topic, and were able to consider the plusses and minuses.
> A simple Google search will lead you to several papers from NASA and other organizations.
No need. I have a big fat binder at home with numerous Air Force, AIAA, NASA and other technical papers and conference proceedings on the topic.
> I never proposed that it could be used for quick-response systems.
Then if you want to do away with rockets... what exactly were you planning on using?
> it is far more efficient at moving heavy objects to orbit to include weapons platforms for the military.
Incorrect. The payloads that an elevator will be able to carry will be fairly small, at least for the foreseeable future.
> The amount of energy is simply the amount needed to mechanically pull the weight the distance required.
Ahhh... no. It is that *plus* the numerous efficiency losses. Consider:
1) Your energy production facility (say, a nuke plant) produces X megawatts.
2) Your laser is, say, 20% efficient at converting electricity to light.
3) You lose 10% of that due to atmospheric scattering.
4) Your crawler converts 80% of the incident laser light to electricity.
5) The onboard motors are 75% efficient at converting electricity to motive power.
6) You lose (handwave) percent to mechanical losses.
7) You lose a *lot* to gravity losses, as you're goign straight up the whole time.
In the end, you are *maybe* a couple percent efficient at turning nuclear power into payload kinetic energy. But lets say you don't care, because nuke plants are a dime a dozen and electricity is too cheap to meter. Woo! But...
Rocket engines are routinely above 90% efficient at turning the chemical energy into kinetic. Gravity losses are at most 25 or so percent, drag losses even less. So if electricity is cheap, then production of chemical fuels (LOX and LH2, LOX/kero, LOX/CH4, whatever) is also cheap, even without petrochemcial feedstocks. I myself built a suitcase-sized machine that made methanol out of water, carbon dioxide and electricity... not that hard.
>Are you putting forth the argument that it would cost the same to move a certain amount of weight by train as it would to by rocket launch?
Are you putting forth the arguement that a train going horizontally has anything to do with a train going *vertically,* while grabbing onto some of the slipperiest materials yet devised by Man?
Did I say I want to do away with rockets? I only said that they were inefficient, impractical, and expensive to do heavy lifting on any reasonable scale into orbit to support the construction of large space stations and adequately shielded and equipped interplanetary vehicles and to get heavy construction, fabrication, and other equipment up there to construct a lunar colony. The long traversal time on the elevator and its pass through the Van Allen belt may make it somewhat impractical or dangerous for humans to use for transportation. I repeat, MAY. Supplemental rocket launches may be necessary and chemical rockets will certainly be needed to propel ships and payloads to and from the moon and within the solar system.
> it is far more efficient at moving heavy objects to
orbit to include weapons platforms for the military.
Incorrect. The payloads that an elevator will be able to carry will be fairly small, at least for the foreseeable future.
Those who are familiar with the space elevator concept predict costs of around a couple hundred dollars per pound. The Space Shuttle can lift 25 tons, once in a blue moon, dangerously, for about $40,000 per lb given what I could gather via Google. One space elevator concept would lift 20 tons at $200 per lb. Once you get one elevator constructed, the construction of others would be relatively elementary and multiple elevators would be in use simultaneously. The cost, per lb, to get an item to orbit would drop with each new elevator. Lifting material to orbit would become relatively safe and economical and routine. And that is the point.
> I only said that they were inefficient, impractical, and expensive to do heavy lifting on any reasonable scale into orbit to support the construction of large space stations
Yes, that's what happens when you *never* *friggen* *launch*. But the sort of market that would support a space elevator would also support more versatile heavy lifters.
> Those who are familiar with the space elevator concept predict costs of around a couple hundred dollars per pound. The Space Shuttle can lift 25 tons, once in a blue moon, dangerously, for about $40,000 per lb given what I could gather via Google.
Trust me, son, if you want to win an arguement regarding the potential costs of space transportation systems with someone who works with space transportation systems, bringing up the Space Shuttle as the benchmark of rockets will only get you laughed at. It's like using an armor-plated, jet-powered Italians sport concept car to prove that automobiles are inefficient means of transportation. The Shuttle does not show what rockets are like; it shows waht *bad* rockets are like.
> One space elevator concept would lift 20 tons at $200 per lb.
Uh-huh. And this is based on what actual engineering? I seem to recall that the Space Shuttle would cost $50 million per flight and woudl require no more than two weeks to turn aroudn for the next flight. And then reality hit. What makes you think that a space elevator which, unlike the Shuttle, is *right* *at* the edge of what is physically possible, would be able to attain the lowest possible prices?
That's correct. Just a lot of expensive engineering.
I noticed that you ignored my questions and changed the subject, but here is one more that you'll ignore. If you have $100,000 in research money to spend, where do you think you will get more for it, putting it into private industry as buying stock in a company or paying it as tax to government?
You space heads are all alike in one regard. You all want someone else to foot the bill for your grandiose pipe dreams. You, like all statists, think that you know best how to spend the money that other people busted their buns for. In that regard you are no different than some "homeless advocate" or some militant welfare queen or Hillary Clinton and her tax based "health care" or any other government looter who has some hair brained scheme that no one would pay for except when forced at gunpoint by the government.
> If you have $100,000 in research money to spend, where do you think you will get more for it, putting it into private industry as buying stock in a company or paying it as tax to government?
A piddly $100,000? Private industry. But a billion? Government R&D. FOr the simple fact that the government has the capability to carry out or direct research projects that private industry would *not* tackle.
> You, like all statists, think that you know best how to spend the money that other people busted their buns for.
Blah, blah, blah. Do you get this twitchy when someone suggests that DARPA or an Air Froce or Army research lab should study such-and-such? Are you still cheesed off about the billiosn spent on the Manhattan project? Couldn't private industry have done it better?
You make my case for me. Government R&D is typical Marxist central planning. Use up a vast quantity of money and you might get something good and you might not, but you don't have any way to tell because there aren't any price signals attached. Further you will never see the true costs. Like I said pay for your own fantasies or if there is so much value in space, form a company to exploit it and get rich.
> Government R&D is typical Marxist central planning.
Blah, blah, blah. Do you get this twitchy when someone suggests that DARPA or an Air Froce or Army research lab should study such-and-such? Are you still cheesed off about the billiosn spent on the Manhattan project? Couldn't private industry have done it better? What about the DARPAnet? Shouldn't you be boycotting the Internet in protest? Or are you just a hypocritical Marxist?
Do you always bray this much when someone suggest that you pay for your own toys?
... internet ... Look at the difference in the government internet and the current version. Do you seriously contend that we wouldn't have had the internet without the government or your hero Al Gore?
Or are you just a hypocritical Marxist?
Me = libertarian/conservative want the space heads to pay for their own space fantasies
You = statist/marxist want someone else to pay for your unworkable fantasies
> your hero Al Gore?
Go back to DU, you dishonest troll. You serve no purpose here.
You're the DU troll and a rude dishonest ass as well. Let's see YOU
As you said in so many words a while back, the real difference between liberals and some self-described "conservatives" boils down to little more than the shape and size of their unconstitutional special interests.
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