Full Version: [News] To space, and beyond!
| QUOTE (Dog) |
| So Cray, Mars has two moons, but you mentioned that it "wobbles" a lot more than earth. Because it's closer to Jupiter, or because its moons are too small? |
In fact, I was recently informed that it's both issues. Jupiter flips Mars around over the course of millions of years and Mars doesn't have a big moon to stabilize it.
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| (BTW: Do you work or study in the field? I'd like to refer to some of what you said, but I'd like to know who I'm referring to.) |
No, I'm just an amateur who reads a lot of science books. Per my .sig, my education is actually in materials engineering; I'm currently employed with a contractor to prevent the US Army from rusting away. If you have specific questions, I can either google up some authoritative links or ask one of the guys in my group, who got a masters in Space Systems Engineering.
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| Another thing I read is that the fanciful elevator would have to be built on or near the equator. So, if anyone's going to use a space-elevator project in their game, there's bound to be some political considerations. |
Actually, you can make off-equator elevators. It's just harder and requires yet stronger materials. This has an example of an off-equator lunar elevator:
http://www.nasa.gov/centers/goddard/images...ar_elevator.jpg
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| I don't know if it's been mentioned, but there was a book titled Mining The Sky that covered this concept. My brothers (who tend to follow things like science and econimics) claimed that the author had No Friggin' Clue™ what sort of staggering costs this endeavor would require. |
Yes. Many asteroid mining proposals tend to be hopeless optimistic. A book that inspired a generation of aerospace engineers, "The High Frontier" by Gerard K. O'Neill, is similarly hopelessly optimistic about turning profits from solar power satellites, using vast numbers of shuttle launches, building huge space stations inexpensively, etc.
And to think, I dropped out of engineering school. Probably the smartest thing I ever did....
www.permanent.com also makes good claims about asteroid mining.
I truthfully think they're an excellent source of resources, but I think the Space Elevator is necessary first.
I truthfully think they're an excellent source of resources, but I think the Space Elevator is necessary first.
The article seems to be ignoring two problems with the nanotubes as well.
a) They state that the nanotubes would be "bonded" together to create the super-cable for a space elevator. Even if the nanotubes are strong enough, is the bonding?
b) A cable gets effectively weaker and less capable of bearing a load the longer it is. Even at "100 times stronger than steel" nanotubes won't have near the tensile strength to serve as the cable material.
-karma
a) They state that the nanotubes would be "bonded" together to create the super-cable for a space elevator. Even if the nanotubes are strong enough, is the bonding?
b) A cable gets effectively weaker and less capable of bearing a load the longer it is. Even at "100 times stronger than steel" nanotubes won't have near the tensile strength to serve as the cable material.
-karma
If you could link looped nanotubes together like a chain (quite a trick admittedly), and then braid those chain filaments together, would that create a strong fiber? I'm not really sure.
Never did buy the whole space elevator concept, personally. Think anti-gravity is more plausible!
Never did buy the whole space elevator concept, personally. Think anti-gravity is more plausible!
| QUOTE (KarmaInferno) |
| a) They state that the nanotubes would be "bonded" together to create the super-cable for a space elevator. Even if the nanotubes are strong enough, is the bonding? |
If the bonds are at the ends of nanotubes carrying the main tensile load, then you can figure the actual material strength is about 1/4 to 1/2 its theoretical strength. Strength of parallel bonds to prevent fibers from separating don't require significant strength.
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| b) A cable gets effectively weaker and less capable of bearing a load the longer it is. Even at "100 times stronger than steel" nanotubes won't have near the tensile strength to serve as the cable material. |
It could work if you accept high taper factors.
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| If you could link looped nanotubes together like a chain (quite a trick admittedly), and then braid those chain filaments together, would that create a strong fiber? |
Not exactly. Carbon nanotubes' primary strength is along their length, not sideways. Bending the tubes into chain links puts loads horizontally on the fibers, which will part easily.
Graphite, the soft stuff of pencil "leads," is nearly as strong as carbon nanotubes along the correct molecular plane. Graphite fibers go to pains to orient the correct planes along the length of the fiber, but they can still be cut with steel scissors.
Right, you write with the point of the pencil, and it dulls, but it holds.
You write with the pencil leaning too far to the side, and *snap*.
I know that's grossly simplified, but the analogy works.
You write with the pencil leaning too far to the side, and *snap*.
I know that's grossly simplified, but the analogy works.
| QUOTE (Fire Hawk) |
| Right, you write with the point of the pencil, and it dulls, but it holds. You write with the pencil leaning too far to the side, and *snap*. |
Heh. That'll work.
Actually, I was thinking that writing with a pencil is an example of the soft side of graphite (it just smears on something as soft as paper), while ultra-strong carbon fiber composites were an example of how graphite can handle a lot of tension.
| QUOTE (Cray74) |
| Not exactly. Carbon nanotubes' primary strength is along their length, not sideways. Bending the tubes into chain links puts loads horizontally on the fibers, which will part easily. |
Yeah fair point. But if memory serves, isn't it theoretically possible to generate fullerene-style structures that aren't simply tubes or balls? So could you perhaps synthesize a toroidal carbon structure that's meant to be that shape, rather than just bend a tube into one? And then, perhaps, find a way to synthesize, in situ- at the end of the chain- a new carbon toroid? And ok, even if it not a toroid then some other kind of fullerene-inspired carbon unit that could be linked together strongly?
Just a thought. Probably not the place for it, but hey. As a geneticist I'm better on the field of organic macromolecules, but I see organic molecular networks finding all sorts of wacky ways to synthesize wacky structures with wonderful properties, so that's why I'm open to the possibility.
Still don't buy the space elevator idea though! Even with the strongest thinnest cable imaginable, just think of the wind strain over such a long length. Even if it didn't break the cable, it'd be constantly pulling the top end back down to Earth. And if something did break the whole system would come crashing down with horrific and expensive consequences. Nope, can't see it ever being built! But the carbon technology would still be pretty useful for other things.
| QUOTE (Witness) |
| But if memory serves, isn't it theoretically possible to generate fullerene-style structures that aren't simply tubes or balls? |
Yes.
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| So could you perhaps synthesize a toroidal carbon structure that's meant to be that shape, rather than just bend a tube into one? |
The end result would be the same. The load would still be applied perpendicular to the main load-bearing direction of the fullerene.
You'd be better off trying to figure out how to generate continuous nanotubes for 25000 miles length, which, IMO, isn't quite as impossible as it sounds.
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| Still don't buy the space elevator idea though! Even with the strongest thinnest cable imaginable, just think of the wind strain over such a long length. |
The wind loads aren't significant compared to the cable's own tension-related loads. Imagine a suspension bridge cable in the wind. The load the cable carries keeps it in place against winds.
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| Even if it didn't break the cable, it'd be constantly pulling the top end back down to Earth. |
That's why the elevator puts its center of mass above geosynchronous orbit, so the cable is always being pulled away from Earth because it wants to move to a higher orbit. Wind loads might slightly (very slightly) cause the bottom 0.08% (~20 miles of 25000) of the cable's length to curve a bit, but that would be fought by the enormous tension that the cable is under. Try plucking one of a grand piano's string at its base - does it stay curved?
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| And if something did break the whole system would come crashing down with horrific and expensive consequences. |
That depends where the break is. The portion of the elevator above the break would just drift upward and westward, as its orbit would be somewhat longer than Earth's day.
(In theory, if you kept the elevator's center of mass perfectly at geosynchronous orbit and ignored outside forces like the moon and sun, you wouldn't even need to anchor the elevator. It would just float almost stationary above the ground.)
The portion of the elevator below the break would fall, but the effects would be comparable to have a suspension bridge cable fall. Most of it would hit the ground at speeds substantially below orbital velocity, even with a very high break. It'd certainly be messy at ground zero, but the damage would be a very narrow narrow strip.
| QUOTE (Cray74) |
| The end result would be the same. The load would still be applied perpendicular to the main load-bearing direction of the fullerene. |
I still feel you could arrange the structure appropriately somehow, but yeah ok.
| QUOTE (Cray74) |
| That's why the elevator puts its center of mass above geosynchronous orbit, so the cable is always being pulled away from Earth because it wants to move to a higher orbit. |
Ah, good point. Thanks for the explanation.
There's another thing I was wondering about. I haven't thought this through but my gut feeling is that- particularly with very long carbon nanotubes, which I believe are highly conductive- wouldn't you get all kinds of energy flow running down that tube due to differential charges? Could that be a problem?
I've heard a concept for an elevator type I believe is known as a "Skyhook," where the elevator doesn't descend all the way to Earth, remaining instead in orbit (possibly mobile), while things from Earth headed upwards are lifted to the "lowest floor" of the elevator by plane, theoretically saving on a lot of stress and strain. Not sure how valid this is, though.
| QUOTE (Witness) |
| I still feel you could arrange the structure appropriately somehow, but yeah ok. |
By the time you're able to modify nanotube ends to some specific shape while forming a cable on the scale of an elevator, you can just link nanotubes end to end, essentially welding them together.
| QUOTE |
| There's another thing I was wondering about. I haven't thought this through but my gut feeling is that- particularly with very long carbon nanotubes, which I believe are highly conductive- wouldn't you get all kinds of energy flow running down that tube due to differential charges? Could that be a problem? |
It's an engineering consideration. Lightning strikes can be a concern near the base. Otherwise, the only energy going through the cable should be what the operator puts into it. The elevator will be stationary in the Earth's magnetic field, so it won't generate electricity that way.
| QUOTE |
| I've heard a concept for an elevator type I believe is known as a "Skyhook," where the elevator doesn't descend all the way to Earth, remaining instead in orbit (possibly mobile), while things from Earth headed upwards are lifted to the "lowest floor" of the elevator by plane, theoretically saving on a lot of stress and strain. Not sure how valid this is, though. |
Depending on how big you make it, the skyhook can be much more feasible than an elevator because the stresses are lower. For example, if it's just a couple thousand miles long, it can reduce the velocity a rocket needs to reach to get to orbit to mach 15 or so. Since rocket fuel use is exponential, that can have dramatic benefits on fuel savings and huge cargo increases. You're also not so firmly tied to an equatorial orbit.
http://members.aol.com/Nathan2go/SPELEV.HTM
http://members.aol.com/Nathan2go/lunavat.htm
The so-called lunar rotovator is very near-term feasible, very feasible. The cables might be individually less than 100 tons (easy to deliver even from Earth), though the system really benefits from some source of material other than from the Earth or moon (like an asteroid).
| QUOTE (Cray74) |
| It's an engineering consideration. Lightning strikes can be a concern near the base. Otherwise, the only energy going through the cable should be what the operator puts into it. The elevator will be stationary in the Earth's magnetic field, so it won't generate electricity that way. |
So solar wind and the Van Allen belts won't induce a potential difference between the two ends?
If you're sufficiently far from the poles, that should only be a problem during really strong sunspot activity.
| QUOTE (Witness) |
| So solar wind and the Van Allen belts won't induce a potential difference between the two ends? |
Oh, right, the Van Allen belts have different charges. That might induce a current.
Again, it's something that can't be overlooked, but nanotubes (graphite, basically) aren't very conductive and the charge sources (the belts) are vacuum-diffuse. It should be a manageable problem.
Looks like they can be conductive, dependent on radius. But yeah I guess it's manageable if it doesn't generate enough heat to compromise the filament.
EDIT: Graphite's actually pretty conductive too, isn't it?
EDIT: Graphite's actually pretty conductive too, isn't it?
| QUOTE (Witness) |
| EDIT: Graphite's actually pretty conductive too, isn't it? |
Graphite can be fairly conductive for a non-metal, though it's not going to be challenging copper or silver anytime soon. Bulk nanotubes will probably be similar to graphite in electrical conductivity, even if some nanotubes can be tricked to show dramatic conductivity.
Lift-port is looking for people will to donate their farm space to provide space for a tether platform. I thought it was a neat idea. What's especially neat is that they're tying it to wind power.
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| Interested in clean, green, renewable wind power to reduce energy costs? Do you know that meteorological data is critical to siting wind turbines? Liftport is seeking opportunities to utilize its ballooned meteorological HALE platforms to help site wind turbines. We are seeking farms or vineyards who will allow us to fly a meteorological HALE platform at low altitude on their property. This can be a much simpler and more cost effective method to help site wind turbines than current standard data collection methods. Liftport is currently particularly interested in property in New England, Washington and in the vicinity of Southern New Jersey. If you know someone who would be interested in installing a Liftport HALE platform on their farm or vineyard please send the location's full mailing address, point of contact, telephone number, email address and the current electricity provider to andrew.becker@liftport.com. |
Might as well let any friends in those locations know. The sooner they get a volunteer (network, people, network!) the sooner research gets started.
And remember, research has compounding returns.
So, I was just watching TV when lo and behold I hear that the spaceport in New Mexico is, technically, fully functional. The first commercial launch will be next year, and they have about a half dozen clients and programs lined up ranging from Virgin Galactic (Now that was a press conference) and the X-Prize Cup.
Did you see the model for the spaceport?
If you look at it from above, it's Richard Branson's iris. That's right: Branson eyeballing space.
The man has "supervillain" written all over him.
If you look at it from above, it's Richard Branson's iris. That's right: Branson eyeballing space.
The man has "supervillain" written all over him.
If supervillainy is what it takes to conquer space, bring on the death rays and insane laughter!
I often wonder what the 'common man' can do to speed our conquest of space, as a species.
I'd like to be able to put more consumer power towards goods that boost us into space, but it's tough. I mean, other than buying the books, what else is there to buy? Buying the books at least gets the money to the people working on these things (in an indirect way), but also provides moral support.
I'd like to be able to put more consumer power towards goods that boost us into space, but it's tough. I mean, other than buying the books, what else is there to buy? Buying the books at least gets the money to the people working on these things (in an indirect way), but also provides moral support.
Convince Congress to pressure NASA to speed up the process of replacing the space shuttle, so that they can commercialize the landing runways in Florida and California. All other spaceport plans aside in Dubai or Singapore or wherever? They're still plans. The United States already has in place the infrastrucure (physical and legal), facilities and operations for at least three or four commercial spaceports right now. Unfortunately, all but one are owned and operated by NASA. If you really want to see more space travel, the most immediate thing one could do is have those facilities opened up to be used to launch and land private spacecraft.
Aside from that, it is currently a matter of building spacecraft to utilize those spaceports. Clearly it is possible. It just requires the willingness and financial resources to build enough of them to meet the demand.
I just wish Branson's and Richardson's egos had at it during the press conference announcing their involvement. I'd have paid money to see that.
Aside from that, it is currently a matter of building spacecraft to utilize those spaceports. Clearly it is possible. It just requires the willingness and financial resources to build enough of them to meet the demand.
I just wish Branson's and Richardson's egos had at it during the press conference announcing their involvement. I'd have paid money to see that.
NASA? Why the americans? Russians have beaten them in about every space milestone: First object in space, first animal in space, first man in space, first woman in space, first spacecraft on the moon, longest stay in space, etc. Maybe america landed the first man on the moon, but really, if you want fast progress of our species into space certainly the Russians are the team to support.
And you'd need to get rid of Greenpeace or somehow make them oblivious to the massive pollution that launching rockets has on the environment.
There's even a bullfrog that competes for females by belching the loudest and longest. Their population is plumetting. In a recent survey, all the male bullfrogs living near launch sites had severe depression; none of them can match 165 decibel output for 60 seconds, and so they have no chance of attracting a mate and just squat dejected in the sludge.
So by all means, the conquest of space by our species, but think of the frogs!
And you'd need to get rid of Greenpeace or somehow make them oblivious to the massive pollution that launching rockets has on the environment.
There's even a bullfrog that competes for females by belching the loudest and longest. Their population is plumetting. In a recent survey, all the male bullfrogs living near launch sites had severe depression; none of them can match 165 decibel output for 60 seconds, and so they have no chance of attracting a mate and just squat dejected in the sludge.
So by all means, the conquest of space by our species, but think of the frogs!
Why?
Because the U.S. has been subsidizing the Russian space program for 15 years. I figure the time for hesitation is over.
Because the U.S. has been subsidizing the Russian space program for 15 years. I figure the time for hesitation is over.
If the tree bears fruit, water it more.
| QUOTE (SL James) |
| Why? Because the U.S. has been subsidizing the Russian space program for 15 years. I figure the time for hesitation is over. |
...could you explain that? Are you saying subsidizing the Russians is good or bad?
I'm saying invest in the spaceports you have.
1: grab an asteroid (how is beyond me and up to the eggheads at AresSpace to decide)
2: move it to the LaGrange Point (The point where the earth and the sun's gravitational puls negate each other, so stuff doesen't move).
3: ...
4: Profit!
2: move it to the LaGrange Point (The point where the earth and the sun's gravitational puls negate each other, so stuff doesen't move).
3: ...
4: Profit!
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| 3: ... |
3. Then a miracle occurs.
| QUOTE (SL James) |
| I'm saying invest in the spaceports you have. |
So...keep investing in existing Russian and American spaceports?
I think the implication is that the Russians have their spaceports, and we have ours, and we should be investing in the ones we have.
| QUOTE (Shrike30) |
| I think the implication is that the Russians have their spaceports, and we have ours, and we should be investing in the ones we have. |
I got that impression, but I wanted to be sure before I responded.
| QUOTE (Muskie @ May 17 2006, 12:49 AM) |
| 1: grab an asteroid (how is beyond me and up to the eggheads at AresSpace to decide) 2: move it to the LaGrange Point (The point where the earth and the sun's gravitational puls negate each other, so stuff doesen't move). 3: ... 4: Profit! |
wrong article: a LaGrange point is more accurate. There are 5 Lagrangian (also libration) points for a two-body system orbiting a fixed point, like the earth-moon-sun combination. L1 and L2 are closest; L4 and L5 have better gravitational advantages (Unlike L1 and L2, they're 'uphill' from everywhere else in the immediate system, making them ideal from a military standpoint as the top of a gravity well is the ultimate high ground). L3, on the far side of the sun, is pretty suboptimal no matter which way you look at it. (I suppose you could be hiding something from prying eyes)
The Earth/Luna/Sol system, you may note, is actually a three-body system, and, as such, gives you ten Lagrange points, five each anchored by Earth-Luna and by Earth-Sol.
The big advantage of L4 and L5 (those're 60 degrees ahead and behind the smaller body, in the same orbit) is that they're stable... L1 through L3, if you nudge something even slightly off it, it'll no longer be in a stable configuration, and it will continue to slide away. If you nudge something off L4 or L5, the mechanics of the orbit will cause it to self-correct... it'll slide back, and end up in a close orbit around the actual Lagrange point. And the gravitational influence of other bodies in the system - especially Jupiter - means enough nudging that if you want something to stay at one of the unstable Lagrange points, it's going to have to do active station-keeping (not as much as it would at a random point in space, but some). Things just naturally fall into the L4 and L5 points and stay there, however... there are quite a few asteroids and moons in the system that hang out around the L4/5 points of various bodies.
The unstable ones have their uses, though... for example, NASA's got a solar observatory satellite parked at the Earth-Sol L1 (between Earth and Sol), where it gets an uninterrupted view of the sun.
The big advantage of L4 and L5 (those're 60 degrees ahead and behind the smaller body, in the same orbit) is that they're stable... L1 through L3, if you nudge something even slightly off it, it'll no longer be in a stable configuration, and it will continue to slide away. If you nudge something off L4 or L5, the mechanics of the orbit will cause it to self-correct... it'll slide back, and end up in a close orbit around the actual Lagrange point. And the gravitational influence of other bodies in the system - especially Jupiter - means enough nudging that if you want something to stay at one of the unstable Lagrange points, it's going to have to do active station-keeping (not as much as it would at a random point in space, but some). Things just naturally fall into the L4 and L5 points and stay there, however... there are quite a few asteroids and moons in the system that hang out around the L4/5 points of various bodies.
The unstable ones have their uses, though... for example, NASA's got a solar observatory satellite parked at the Earth-Sol L1 (between Earth and Sol), where it gets an uninterrupted view of the sun.
Well, while we're nitpicking on LaGrange knowledge... 
| QUOTE |
| The big advantage of L4 and L5 (those're 60 degrees ahead and behind the smaller body, in the same orbit) is that they're stable... |
They're stable if the two bodies forming them differ in mass by more than a factor of 25. For example, the Earth is 81 times more massive than Luna, so its L4 and L5 points are stable. However, the Pluto-Charon L4/L5 points are not.
| QUOTE |
| The unstable ones have their uses, though... for example, NASA's got a solar observatory satellite parked at the Earth-Sol L1 (between Earth and Sol), where it gets an uninterrupted view of the sun. |
They're also waystations on low energy, low speed routes through the solar system.
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