Slashdot Mirror
NPR Talks Skyhooks
David writes "NPR's Talk of the Nation this past week featured Brad Edwards, President of Carbon Designs Inc., to talk about their plans to develop an elevator that would lift people to an object orbiting in outer space. The project's homepage details their plans and ambitions. The discussion expands on callers' concerns about such problems as commercial airliners running into the super long cable or if it would act as a conduit for lightning."
Does the audio program mention the word "skyhook"?
Why bring up the Aussie 70's supergroup?
Wow, never read about something like this on Slashdot before. (Actually, I think the Space Elevator idea is very cool)
I hope this isn't going to be anything like the escalator to nowhere...
What does this button do...
Wow, our society has changed. The concept of airliners being uninformed of the location of these cables or whatever they are is just plain stupid. Of course they will know that they're there. Not to mention, even if they didn't know, the chance of a collision is fabulously small.
People should be more worried about if this is the best way to spend money or not. Personally, I think it's a pretty sweet idea and I'd be totally for supporting it. Looks quite awesome, actually!
Would Not Like to be stuck if that elevator breaks down :|
Here is some money that NASA could "invest" in another x-prize like compitition. Get some innovation back into the space game. Maybe once China starts blasting some people towards Mars the US will get off its ass again.
The more you know, the less you understand.
From TFA:
We firmly believe that the set of technologies that underlie the infinite promise of the Space Elevator can be demonstrated, or proven infeasible, within a 5 year time-frame. And hence our name. Elevator:2010. we promise to get an answer for you by then.
Message 5 years from now:
42
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
The longest song in my MP3 collection is 22:43 (Autobahn by Kraftwerk - even on topic, sort of...) Is that long enough for the ride up? How many quarters do I need to put in the slot?
This issue is a bit more complicated than you think.
Don't space elevators have to be built along the equator?
Space elevators are, by far, the biggest form of snake oil in our time. It may become the biggest form of snake oil ever.
You can mod me any way you like but, anyone that invests in a space elevator deserves the loss that they are guaranteed!
According to the website, the elevator will move at 200 mph. Considering that our atmosphere is roughly 380 miles, I'm going to have to listen to Kenny G for almost 2 hours!
*Don't space elevators have to be built along the equator?
I thought this as well, but no, they don't. A rough diagram of a space elevator would be:
O--------
Where the "O" is the Earth. Imagine, right before "tying down" the base of your elevator, you drag i "up" a few dozen degrees to New York. The farther North you go, the more of an angle it will have, but it's not unstable so long as it's anchored.
The first thousand miles of the climb would be like a very steep gondola ride.
Pulp Audio Weekly - Geek News and Reviews
Perhaps it isn't snake oil but, rather smoke and mirrors. I can't help but recall the promise of mining manganese nodules from the sea floor in the 1970's. It turned out to be a cover story for building a spy ship to recover a sunken Soviet submarine. Perhaps the space elevator is a cover story for some other spy operation.
Did you just hear a helicopter? Was it black?
Is this a reference to some sci-fi movie or something? I don't get it.
I guess the old prank of jumping onto a crowded car and pushing all the buttons would be a no-no...
Seeing bad movies only encourages them. Watch responsibly
Motherfucking Kraftwerk! That kicks ass.
It always comes up, but protecting a space elevator is really
simple to solve. Put the base in the ocean, and stick a carrier task force there to protect it.
We already have an example to follow. Fort Knox has a tank combat training ground there, and plenty of tanks stationed there permanently. Good luck trying to raid the place.
Terrorist attacks are dangerous because they could happen anywhere, but that doesn't mean that we can't make a single known place extremely secure from that sort of thing. If it is decided that no aircraft will approach within 100 miles of a space elevator, a single carrier task group could enforce that easily. Revenues from the space elevator would easily pay for the security force too, and it'll still be the cheapest way to get something into space.
Fascism trolls keeping me up every night. When I starts a preachin', he HITS ME WITH HIS REICH!
If you travel to fast you become vaporware.
This has been tried before, it was called the Tower of Babble,grab a Bible and see how the story ends...
I have been using Google Suggest for a while now. I was wondering what is the criteria or threshold of search popularity for a phrase/word before it enters the Google Suggest database?
Where's my free iPod!? Until then, I'll settle for a kiss...
I find this technology very intriguing. But it took me a long time to realise that they are serious. First time I heard about this I had to check if it was April first.
Anyway, the most interesting thing I heard in this interview was that they said that if you let the elevator go up really far, close to the counter weight, and let go of an object there, it would fly faster than with conventional rockets because of the centrifugal motion.
So that could be used to fling stuff from earth really fast. And since the earth angle varies quite significantly it can be sent to a a great different places.
There is still a large number of directions that one of these objects can't go too, but, still, pretty cool.
The Internet is full. Go Away!!!
% mplayer -ao pcm:file=20050603_totn_03.wav 'rtsp://real.npr.na-central.speedera.net:80/real.n pr.na-central/totn/20050603_totn_03.rm'
Should work if one has mplayer but does not have realplayer.
ZP
We only can learn from our mistakes.
... it's so much more eloquent...
kulakovich
Doesn't an orbit have to go around the center of gravity of what its orbiting? If so, it wouldn't be able to simply always be 'over' NYC. Right?
Yes, an off-equator tower would connect an anchor to an equitorial geosync satellite at an angle. Pitch from an equatorial anchor is 90'; polar pitch is 0'. At about N40' latitude, the cable would appear to head South, rising at 50'. Such a "leaning tower of New York" would stretch across the southern half of the Northern Hemisphere, along the East Coast, the mouth of the Caribbean, and NE South America. The lower part of the tether could include radio equipment working like traditional geosynchronous satellites, but with much less latency, owing to the much lower elevation. Taking the place of the old WTC antennae, which, though higher than practically any other building in the US, still had a relatively close horizon. The question is whether the tether's tensile strength can handle the force vector at 40' to its linear axis, rather than the typical 0' when it's normal to the equator. And whether any sag would make the already longer distance inefficient, either in ascending travel or manufacture (shipping the tether anchored to a ship to be reanchored in NYC) remains to be seen. But the WTC v1.0 was expensive - it would have been cheaper to build it in Puerto Rico or Ecuador. But not nearly as useful to New Yorkers. Let's make one!
--
make install -not war
The satellite is "over" the equator, but where you anchor the cable on the surface of the Earth doesn't have to be on a straight line between the satellite and the center of the Earth.
Pulp Audio Weekly - Geek News and Reviews
The last time I saw skyhooks actually being used was on PBN! http://www.paintball-net.com/
o ticfairytale=}{=FireDrake=}{=The Lost Souls=}
a padded multiterrain insulated suit[skyhooks][refracto]{=DavidRM=}{=Dug=}{=Psych
I want to be retired when I grow up.
Covered a lot of the questions that have popped into my head while reading the previous 947 Slashdot/Space-elevator articles.
Highlights
- Location? Straight south of California near the equator.
- Timeframe? 15+ years
- What if an airliner flew into it? Pretty much screwed. But the location is 400 miles from any air route so shouldn't be a problem.
- How long would it take to get up? A few hours.
- Wouldn't it be a huge lightning rod? Yeah, but that area of the world does not have lightning, so shouldn't be a problem.
- Wouldn't the car that goes up the cable just pull it down and not crawl up it? Yes, but the car is only a few tons and the weight of the cable and weight on the other end was something like a couple thousand tons. So shouldn't be a problem.
There are a lot of "shouldn't be a problem"'s in there that one of them will be a problem. Exciting technology though.
The management of Carbon Designs should vet their workforce and ensure that no Chinese nationals are currently employed. Beijing for many years has sought to militarize space, and accessing this space-elevator technology would enable them to accelerate such nefarious plans.
But I'm waiting for the Space Escalator.
Have you ever run up a flight or two of stairs? Just getting going isn't good enough. You need a sustained input of energy to keep going.
This elevator will propel its payload straight up at 200 mile/h, using solar power? Those are mighty powerful solar panels.
In a nutshell, you have to supply escape-velocity energy to any mass you drag up the thing. No two ways about it.
What it's like to get stuck mid-air on a long lift.
God help you if the elevator goes on the fritz in the midst of your ride!
sigs are for losers (except to point out that sigs are for losers)
If only it could lift people out of Darfur...
(I'm afraid to fly, logic aside, *this* terrifies me.)
Get your Unix fortune now!
What kind of damage can the ribbon sustain if a small meteorite or space junk impact it? No big deal or total failure?
Authority questions you. Return the favor.
http://www.isr.us/video/SE-INTRO_Final-1stream-384 .wmv
Covers the basics of the elevator, what it looks like, how it works, etc...
The question of how this thing is powered never popped into my head before, but the video shows that they will use a lazer shot from the base station. Crazy stuff.
I could probably use that to find myself a life...
As long as you're maypoling near the bottom (which introduces a railroad switch like complexity to runners traveling up/down the elevator), you may as well maypole near the middle where satellites are most likely to hit the elevator, so that the platform on the ground (sea or mountaintop) doesn't have to be moving around. You simply rotate, say, two cables 10 kilometers apart, 90 degrees as needed to avoid collisions, death rays and the like.
At that point, maypoling should be used at the top too, in reverse, so that there only needs to be a standard width for the cables, making them cheaper to manufacture over a highly tapered single cable. If the same machinery used to build suspension bridges and other things can be used for the space elevator, the sales volume will make it even cheaper.
Having to negotiate intersections introduces an extra complexity, slows down the speed of travel and adds extra weight, but it may become a desirable complexity at some point if it allows simultaneous up/down travel (i.e. more capacity), can be extended to make travel easy between elevators, etc.
More importantly, Bill Clinton was featured on this past Friday's TOTN.
Mod this down, but it was a great show and a must listen.
The question is whether the tether's tensile strength can handle the force vector at 40' to its linear axis, rather than the typical 0' when it's normal to the equator.
First, no flexible cable is going to experience a force in any direction but along its length, or it will change shape until the force is along its length.
Second, in an equatorial elevator, there is no force at the lower end (the end effectively "floats"). The issue with a non-equatorial tether is that there are tremendous forces trying to move that end towards the equator, so you need a very strong anchor (not needed at all for an equatorial tether), and a stronger cable, which is heavier, which increases the load, which requires a stronger cable, and so on. And the anchor needs to be attached to something, and rock ain't made of nanotubes, so you'll have to distribute the force somehow -- I don't think this is going to be tied to the top of some building in Manhattan.
I think it's a bit premature to propose such a challenge before we even have an equatorial elevator working.
it's not unstable so long as it's anchored
As if that part is somehow easy? The forces on the anchor are tremendous in such a situation, and the forces on the cable are increased, so it needs to be stronger.
"Being inside a nuclear fireball isn't dangerous as long as you're wearing protective clothing."
Of course your first point is a restatement, as an answer, of the "question" (issue, really) that I posted, which you quoted.
The other point is the details of that issue. How much heavier would a 40'N cable have to be than a 0' cable? Therefore, how much force is exerted on the anchor? And how much volume of harborbottom much is needed to exceed that force, including the cargo loads, and possibly even variables like lunar tides and other perturbers? If the cable is anchored to a giant sack of muck in the harbor, or farther out to sea, that would both distribute the force across the sack's surface, and contain the weight to anchor.
FWIW, I suggested the harbor, not the top of a building. Our suspension bridges here in NYC are anchored in big blocks sunk into the riverside mud. The skyhook website claims an (assumedly equatorial) tether would weigh only 1000 tons. If a 40'N tether isn't orders of magnitude "heavier" in force pulling the anchor point, such an anchor seems possible.
As for the prematurity, one thing you learn early in NYC is to start asking for what you want ASAP. Why wait for the previous guy to get out of the way, when they're already listening to the next orders? At either the deli or the skyhook counter.
--
make install -not war
One weakness of the plan, as I see it, is the all or nothing nature of the plan. A less risky plan that could be a stepping stone to a space elevator is to start with a much smaller rotating tether in orbit.
Imagine a thousand mile long tether in orbit with its center of gravity 600 above the earths surface. In addition to orbiting the earth The tether would rotate about its center of gravity at a rotation speed such that its speed relative to the earths surface at its ends closent approch would be zero.
A rocket would have to ascend to 100 miles up and rondezvous with a a tether end that, for the moment, is stationary. It would remain atteached to the tether while the tether rotated 180 degrees about its center of gravity. At tht point the rocket would be 1100 miles above the earth and traveling at about twice orbital velocity. If the rocket detatched at this point would would be well above escape velocity.
Longer tethers would reduce G forces and avoid the need for the first 100 mile step. The ultime version of the tether would have a CG in geosynchronous orbit and aon end on the ground.
http://www.unmuseum.org/spaceelevator.htm
I thought Dr. Edwards went through some interesting verbal gymnastics at one point to avoid mentioning anyone else by name ..
...funding to do it, from private sources, from commercial sources. But since it's new, it always takes a bit of time to be accepted.
FLATOW: Is there a business here? Is this a private project, much like the space plane was?
Dr. EDWARDS: Well, right now the space elevator--up until a couple of years ago, very, very few people knew about it. And so it's really
just getting started. There's a couple hundred researchers now that have sort of taken up the torch and are working on it at a number of
locations, including Los Alamos National Laboratory, some private companies, some people at MIT, various locations. And right now,
there's not a dramatic amount of funding for it, and that's part of what we're working on is to get...
FLATOW: Yeah.
Dr. EDWARDS:
FLATOW: Right. How...
Dr. EDWARDS: Usually people look at first thing they think is it's crazy.
FLATOW: That didn't stop a lot of people from making what they said they would.
Dr. EDWARDS: Yeah.
Okay, sure, Edwards is running a startup and looking for funding but it can't hurt to tip the hat a bit to your competitors. If 'competitors' is even the proper word for an industry that by and large doesn't exist. Granted, I'm biased in that regard.
Display some adaptability.
'nuff said. That may well pay for building it.
One of the issues that I keep reading about a space elevator is how the cart will be provided energy to move up. Well, how about a space goldola instead of a space elevator. Why not have the orbiting mass have a pulley connected to two pulleys on the ground with each at a seperate ground (or ocean) station seperated by several kilometers. The accute triangle that this system would create would allow a space gondola to ride up a moving cable without getting entangled. The cable, of course, being moved by the ground station allowing the gondola to carry more weight. The gondolas could also be returned to earth rather than discarded into space when the orbiting mass becomes massiv enough. Another benefit is the ability to easily repair a camaged cable. As the cable passes through each ground station a L.A.S.E.R. could scan the cable for small fractures and they could be repaired. The cable could be thickened in the same fashion by adding more layers to the existing cable as it passes through the ground stations. And another benefit of this three pulley system is in the event of a catastrophic failure of the cable. If the cable breaks at a single point, the breaks can be applied at the orbiting mass and at the ground stations. No matter where a single break is the mass will be connedted to at least one ground station. Space gondolas, w00t!
Welcome to the land of the free...pay toll ahead...no photography...please open your bag...
I thought space elevators with cables were out (due to the tensil strength the cable should have) and space fountain were in (since easier to build, not just buildable on the equator, etc.)
http://en.wikipedia.org/wiki/Space_fountain
I can't think of another monumental way to get into space or back to Earth, as in you go up, you come down, the framework stays in place (in theory).
I always was put off the notion of space travel because of a few things: the huge amount of research, fuel and luck neccesary to get the rockets into space, the danger of not being able to get back far into the voyage, and the rather uncomfortable way you need to crash back on Earth at the end.
Space Elevators are always there once built. They provide the possibility of new resources if you can get one to a source that can be mined. The possibility of space tourism for the non-billionaires could be possible at some point in future. And they are cool.
In conclusion: I &heart Space Elevators.
Why build a skyhook? You know Dash Rendar's just going to fly by and blow it up...
#define QUESTION ((bb) || !(bb))
> Put the base in the ocean, and stick a carrier task force there to protect it.
/ nr.html
Better yet, put it on Nauru.
http://www.cia.gov/cia/publications/factbook/geos
With the phosphates gone, the international money laundering (er banking) industry dismantled, and nothing else on the horizon, this could be just what this island nation needs.
Finally something that severe isolation is good for.
XJS*C4JDBQADN1.NSBN3*2IDNEN*GTUBE-STANDARD-ANTI-U
in which case all you have to overcome is friction. (a la Traction Elevators, Paternosters, Funicular Railways, etc.)
I believe that the glass elevator floated. This is supported by a large ribbon. There is a difference. Oh what's that? You were just being a sarcastic jackass to be funny? OK.
I always love it in SciFi novels when their space elevators snap because of a terrorist attack or one failed component in an insanely long chain of parts.
Fantastic.
Seeing it hasn't been brought up yet, no material strong enough to build the elevator yet exists. It is not yet clear whether it is even possible to do so. Carbon nanotubes may be strong enough, but nobody has yet been able to assemble them together into a "ribbon" of the strength required yet.
Any sufficiently advanced technology is indistinguishable from a rigged demo
--Andy Finkel (J. Klass?)
I am continually amazed that each of the 50 times the space elevator has been mentioned recently how many Slashdotters seem to have heard about it for the first time!
/.? Where are all the geeks?
Is it just me or are more and more non-technical people deluging news site such as
At the time, it was better known as Babel. It wasn't named Babble until the people could no longer understand each other.
Later of course, Babel and Mabel got together and had lots of Baby Bels. The runt of the family was nicknamed Deci Bel.
Time flies like an arrow. Fruit flies like a banana.
The ribbon is 62,000 miles long
The climbers travel at a steady 200 miles per hour
That's one hell of an elevator trip. The new opportunities this provides for artists of Elevator Music alone should make this venture worthwhile for someone.
If you want a picture of the future, imagine a boot stamping on a human face forever.
- George Orwell
...some wiseass physics research team will unveil inertia/gravity control systems capable of turning old oil tankers and freighters into space capable cargo vessels and start hefting whole space stations at once with the greatest of ease.
If my grammar and spelling are off, I am [distracted/tired/careless] (take your pick)
Wouldn't that have the velocity to cause some serious damage?
I accept your definition, albeit without clarifying the dimensions of each.
As I understand it, a hoytether is a millimeter-scale (micro) structure whereas maypoles are meter or potentially kilometer-sized (macro) structures. What I was intending to propose near the middle section was a two-cable maypole of hoytether-based cables, NOT maypoles instead of hoytethers. Now, if a reverse, hierarchical maypole can be used near the top to provide a tapering effect, that doesn't preclude one from using hoytethers for each of the cables. The weight distribution or energy release characteristics may well be better for such a scheme.
One thing that I also left out is that, for the middle section, I was thinking, not in terms of a single maypole with two cables hanging down, but one where the cables meet back up again to form a reverse maypole at the bottom, similar to how train tracks accomplish the same feat. (Let the analogies of this to the transcontinental railroad begin...)
Further, I am not proposing maypoles as a solution to aircraft impacts (although indeed a million little cables hanging down would be difficult to knock out, wouldn't they?). Primarily, I see them as a way of making it possible to affix an SE to a mountaintop while still allowing the structure to dodge orbiting objects with predictable orbits.
I think electromagnetic gun launch to space, EGLTS, is a good idea for SCRATS, Safe Cheap Reliable Access to Space.
The coilgun or Earth to Space Mass Driver, doesn't match the Space Elevator's estimated price to high Earth orbit, it beats it by a hundred times.
The entire ETSMD installation would be in the ground, and in bad weather it can just be covered with a tarpaulin and everybody's happy.
Shock G forces might be around 30G, with various considerations about that, with the live passenger enclosure just crashing within the pod.
Safer, cheaper, and more reliable: ETSMD.
Ross F.
There seems to be plenty on the website about taking a payload into space, but absolutely nothing about coming back down again.
In my first college physics class just about every problem said to assume that the pulley has no mass and no friction. So frictionless and massless pulleys must exist. Right?
Don't count on it buddy.
If China sends any sinonauts to Mars, they will be doing it with the money they made selling us money to cover the interest on our debt. It would be an indication that the money we would have spent on our space program, will be instead have been sent to China to support theirs.
Sure glad we have our space exploration policy all in order. This Bush team is sure an impressive supporter of space exploration compared to teams past, where all they did was go to the moon and back.
1) How much drag (in Newton-meters) would such a structure produce?
2) Would such forces tear apart most materials?
3) Are there any materials which could withstand such forces without deformation or failure?
I'm staggered by the /.ers who seem to think this is news.
. asp
The Space Elevator was first proposed in 1895! Technical details were being considered in the 1960s. A simple Google will provide lots of references - here's one for starters: http://www.sciencenews.org/articles/20021005/bob9
You can see that different groups have been undertaking research and making proposals for most of a human lifetime.
1) Large plane full of innocent people changes course and flies close to the cable.
2) Nobody knows who is really piloting the plane - maybe it's a terrorist, maybe not.
3) US fighters have only a few minutes to react and shoot it down, killing everyone on board.
4) Anti-US riots erupt across Europe and Asia
How exactly would this "dissuade" someone who hates America and is willing to lose his life?
Well by then aliens will have bombarded the earth with nuclear waste and we won't be putting gravity control on some junky old tanker.
No, we'll find the battleship Yamato in the Pacific. That'll show those nuclear waste launching aliens who's boss.
you could perhaps spool out a cable and then fly in a circle or similar manuvure to 'sweep' a much larger area (or perhaps more importantly enscribing a circle, with the greatest lower bound to its radius)
Which should take care of hitting it if you know where it is.
How fragile is this thing? How much tolerance does it have in its tensile and compresive strength moduli. Is its behaviour described well by classical descriptions such and bulk and youngs moduli. The tolerance is not an order of magnitude or any comfortably sized buffer, so maby many more will have to be built (easy after the first).
It would be cool if it just sliced the wing off, like william gibsons nano wire.
I had expected someone to bring up the Arthur C. Clark story "The Lathe of Heaven". Clark was not only a SF writer he was also an engineer scientist. He invented the idea of a space elevator. Read his SF book "The Lathe of Heaven" to get the original idea and some of the problems associated with a space elevator, it's also a good read. For some real scientific reading, check out the book: "The Space Elevator: A Revolutionary Earth-to-Space Transportation System" by Bradley C., Ph.D. Edwards, Eric A. Westling. These 2 books should answer most, if not all of the questions regarding the physics and engineering of a space elevator.
As for music, that's why you have an iPod...
Suitcase nukes exist, sort of. While it's not quite something you'd carry in a suitcase, the Special Atomic Demolition Munition was a 1-kiloton nuke that weighed about 68 kilograms. You're not going to carry it in your suitcase unless you're He-Man, but you could certainly fit into the trunk of your car, even a French one ;) However, the odds of a terrorist group being able to build a nuke this small are fairly minimal without being handed the design by somebody else.
The resources and experience required to build a nuclear weapon are also somewhat less than is commonly believed; this article on the former South African nuclear program gives some idea of the minimum budget required for the job from scratch- tens of millions of dollars, but not hundreds. I should add that I'm highly skeptical that any terrorist group could coordinate this kind of money and people, in secret, for long enough to pull such an accomplishment off.
Finally, uranium, even enriched uranium, or plutonium is pretty hard stuff to detect; they just don't emit very much radiation until you push them into a critical mass! Bruce Schneier's blog links to an extensive report on the topic; he also links to news reports about how the detectors they have bought detect so many false alarms as to be essentially useless. Maybe the three-letter agencies have something better (for instance, looking for chemical traces of radioactive material rather than radiation itself), but if it is it's kept pretty secret.
Still, you're basically right. Terrorists aren't going to be whipping up nukes to send through the mail any time soon.
Any sufficiently advanced technology is indistinguishable from a rigged demo
--Andy Finkel (J. Klass?)
Why do you say that the centre of mass must be in gso. is it because you think this would result in the minimum tension(or perhaps no tension cause the centre of mass has no NET forces on it?). Im pretty sure this is incorrect.
;)
;)
Lemme see if i can get us a diagram.
_Diag 1:Somewhere on the R axis_
removed due to fucking lame filter
Let, R_a be the radius of the earth. R_b the distance from the centre of the earth to the end of the cable. Oh and obviously the origin is at the centre of the earth, and you call yourself an xian.
Now if we consider some infinitessimal portion of the cable, dr, at the point r.
removed due to fucking lame filter
Let p(r) be the radius of the cable. and for simplicity lets assume that the cable is the volume formed by a cylindrical revolution of the profile defined by p(r). We want p(r) as opposed to a constant radius cause we probably want a taper, generalization is good
The forces on the infinitessimal portion are going to be;
F_gQ----*po**----QF_c
T_1Q----*int*----QT_2
**replace Q's with greater thans and less thans cause slashdot takes my symbols !! fuck this. why doesnt mathml work yet. you call yourself hackers. why cant i embed a browser inside texmacs and use it to render and edit tex inside a webpage... all the hard work has been done. texmacs supports embedding a terminal. then imagine running irssi (for example) and chatting on irc inside texmacs and having it render any tex and allow you to enter math directly. This is what I really really really really want. Hack this up and you would become a hero overnight, trust me. Might even massively increase the accessability of math. Just imagine how often you would like to insert some concise integral or something and you have to hack it up in ascii. ahem, back to the derivation.
Part of our conditions are that the cable is in equilibrium... so we assume that these forces sum to zero;Remember where the positive direction was defined;
T_2 + F_c - T_1 - F_g = 0
F_g is the force on the infinitessimal mass due to gravity, and T_1 and T_2 are the tension in each respective direction. F_c is the centrefugal force (fugal from latin for fleeing like a fugitive), for all you centrefugal force dissidents that think that changing to a rotating non inertial reference frame somehow changes anything...
These are all functions of r.
F_g(r) = G_u m_e m(r) / r^2
Where G_u is yo universal gravitational constant. and m_e is the mass of the earth, and m(r) is the mass of the infinitessimal portion of cable at r.
m(r)= ro pi (p(r))^2 dr
where ro is the density of the cable material (and we are going to assume its constant although it may be a significant simplification, someone else can generalise this point)and pi is 3 if you are from Indiana.
F_g(r) = [G_u m_e ro pi (p(r))^2 / r^2] dr
Let g= G_u m_e
Let a= ro pi
F_g(r) = [g a (p(r))^2 / r^2] dr
F_c(r) = m(r) w^2 r
= a (p(r))^2 w^2 r dr
Utilising the equilibrium condition.
T_2(r) + F_c(r) - T_1(r) - F_g(r) = 0
We also have some information about the T functions(boundary conditions);
T_1(r_a)=0
T_2(r_b)=0
Now what are T_1(r) and T_2(r).. I intuit (but someone can correct me) that they are the definite integral of all the contributions to the tension from each half, above and below your position(you would be located at r, i know i am). So;
T_1 = integral on (r_a,r) of [F_g(r) - F_c(r)]
F_g(r) = [g a (p(r))^2 / r^2] dr
F_c(r) = a (p(r))^2 w^2 r dr
F_g - F_c = a (p(r))^2 [g/r^2 - w^2 r] dr
Like wise T_2 = integral on (r,r_b) of [F_c - F_g]
Now the centre of mass is the first moment (i immediately thought the 2nd moment might be closer to the mark cause of the quadratic nature of newtonian gravity). R_cm = position of centre of mass
R_cm = (integral on (r_a,r_b) of [m(r) r] dr) / (integral on (r_a,r_b) of [m(r)]
lmao
A space elevator is not really that hard to make once you have the cable material sussed. And if you can work out some way to make descending cars power the ascending ones then it is also quite energy efficient as well.
Compare that to gravity manipulation: there's no solid evidence that it is even possible, at least at any scale likely to be useful, and even if it is it is likely to consume astronomical amounts of energy to get anything sizable up the gravity well.
Given the kind of moron that would tune-in to the marxist tripe broadcast around-the-clock on NPR, are you surprised?
I cannot wait until CPB gets its federal funding eliminated.
So, you've got this single cable with one, two? elevators which take several hours each to get things into space and then another several hours to get back down and it's supposed to be cheaper than firing them up with rockets?
How does that work? Economically I mean.
As opposed to lots of companies competing to build cheaper rocket or similar technology, launching in parallel.
Deleted
The space fountain (and by extension, the Lofstrom Loop) are so utterly silly to the normal person that they would *never* be built. For one thing, you're essentially talking about shooting a continous stream of bullets into space where you catch them and shoot them back at the ground, in a large circle.
Yes, it could be done; no, there's not a chance in hell that it ever will be.
- Give a man a fire and he's warm for a day, but set him on fire and he's warm for the rest of his life.
Extra cables are indeed a nice thing in space, but there's a mass tradeoff. If you don't regularly affix them to one another, they're not strength-redundant. If you do regularly affix them to one another, the more frequently they're affixed, the better they take an impact, but the mass requirements grow quickly, and with a space elevator, mass requirements are already ridiculously constrained (currently, far beyond anything that we're capable of). That's why I proposed only doing the very tip of the tether - the earth atmospheric intersection point - as a maypole. The length in the atmosphere is almost insignificant compared to the total length.
The main cable should only be able to withstand micrometeorite impacts, in my view, so as not to increase its mass significantly. I agree about the importance of moving the tether for dodging debris, of course - I think that will be critical for any application like this.
We should start dealing in those black-market beagles.
"an ideal platform for your corporate message."
Please! Please no advertisements on this thing! Advertisements are showing up *everywhere* and I'm SO sick of them!
And now they plan to create such a beautiful tool... and you can buy advertising space on it?
(ObFunny: at least there's plenty of space on it, haha)
Free PC version of ChipWits at http://www.breueronline.de/klaus/chipwits/
Moderation -2
50% Flamebait
50% Troll
What kind of insane TrollMods are you? Auditioning to fly planes for the Qaeda?
--
make install -not war
The 100 mile lower limit in my example was selected as an estimate of a point where drag was neglible. If not, change it to a point where it is effectively zero. Remember that the path of the endpoint is essentially straight down to 100 miles and then straight up.
The forces in my 1000 mile example are much less than they would be in the 55,000 mile full space elevator. The point is that the length would be driven by the available materials.
...And if anyone is still worried about lightning, it would be possible to attach the bottom of the cable to a airship which floats above the weather and can control its own ballast and therefore altitude. This would require periodic relief flights from 2 or 3 other airships based nearby, but the technology is off the shelf at this point. If all of the airships are damaged, at the worst case the anchor weights it is holding up sink to some stable equilibrium at ground level.
Not having a base station on the ground also solves problems such as tsunami, atmospheric aircraft (they can't fly that high), and it makes the cable that much harder to find in the first place. The only major catch (that I can think of) is that it requires the base to be near the equator.
"The length in the atmosphere is almost insignificant compared to the total length."
True, but the bottom is also where gravity is pulling at its strongest. Any savings of weight in that section goes a long way to reducing the size of the rest of the cable. Conversely, adding extra mass near the top adds almost no weight because the mass is in microgravity.
In theory, yes, maypoles are going to be less strength redundant, but they can be more spatially redundant. That is, a meteor shower is less likely to take out the whole thing if it is spread out over several kilometers and if the meteors are closely bunched together. Also, consider that repairing or replacing one of several cables is less tricky than repairing the only cable that is holding everything up.
Perhaps maypoles and mountaintop stations will be too fancy for the first elevator, but in preparation for major meteor showers I think they will want to consider those options.
Actually, for the competition, We are only aiming for 1 m/s for 50m up a tether. Power will be supplied by a 1300W (or so) searchlight. Most groups will likely be using sattellite solar panels. In future competitions these are expected to be increased, and presumeably power will eventually be supplied using a laser. The winner will be determined by some combination of climbing speed and payload.
I expect that any groups that can meet the requirements specification (PDF) [http://www.elevator2010.org/site/documents/climbe r_rulebook.current.pdf ] will be in a good position, regardless of speed or payload.
BTW, I'm actually part of a UBC team building a climber, our website is here: http://www.physics.ubc.ca/~climber/index.html
The other issue not addressed is that the Earth's magnetosphere is neither uniform nor static.
It is significantly compressed on the Sunward side, and elongated on the opposite side, through which any geostationary satellite (and hence space tether) would cross on a 24 hour basis.
Additionally, there is significant displacement as a result of variable solar activity (aside: WindowMaker's 'wmspaceweather' dock app is oddly addictive). I believe other events can create flux as well, both external and internal to the Earth.
Given the length of the tether, even minor effects will be significantly magnified.
Nothing remotely of this scale has been attempted. Structures vastly smaller than this scale have had pronounced effects. This includes both tethered satellites, and earth-based power grids, and both have experience unexpected catastrophic failures due to widespread magnetic events, natural (again: solar events, magnetosphere flux) and man-made (nuclear blasts).
What part of "gestalt" don't you understand?
Nothing off the top of my head, though several recent solar storm writeups have mentioned disturbances to the Canadian electrical grid, some years back. Google says Quebec, 1989.
What part of "gestalt" don't you understand?