Slashdot Mirror
Space Elevators: Low Cost Ticket to GEO?
Crocuta writes "The current issue of Science
News features a cover story
that discusses the current developments in space elevator technology. NASA has been
working on such devices for many years, but private companies such as Highlift Systems are now jumping on the space
elevator bandwagon, no doubt seeing the huge potential profit in a low cost per pound
delivery system. PhysicsWeb has a somewhat
older, but much more technical article
on the formation and structure of the carbon nanotubes that form the basis of the proposed
tether cables. With a development like this, we could shoot entire boy bands into space and make
the world a better place."
This story is a repeat that I've seen at least one other time here on /.. If I recall correctly, the cable is very unlikely to snap, but if a terrorist were to break it, the cable would fall to the ocean and there wouldn't be any devastating impact.
That would still be very expensive, but immensely less expensive than using the current methods of reaching orbit for comparable amounts of cargo.
Of course, my estimates are open to dispute, and I could be wrong. But I don't care: the space elevator is cool!
After a cruise through tropical waters, you arrive at a large, anchored platform in the middle of the Pacific Ocean
The very first few lines of the article. The anchor would be a modified oiling platform, not a tower in ecuadro, Brasil or Peru (which, BTW, are NOT anti-american). This platforms are located outside any countries jurisdiction.
There are two kinds of people in the world: Those with good memory.
Here are some more links to info on our very own Slashdot:
Here
Here..
Here..
and Here
Here's a nice sized (15MB) report done by NASA. They talk about all sorts of problems that need to be worked out to make get this project off the ground http://www.niac.usra.edu/files/studies/final_repor t/pdf/472Edwards.pdf
free ipod? yeah.
The equator DOES NOT pass through India or Venezuala ..
.. and relatively friendly.
The equator passes through 13 countries: Ecuador, Colombia, Brazil, Sao Tome & Principe, Gabon, Republic of the Congo, Democratic Republic of the Congo, Uganda, Kenya, Somalia, Maldives, Indonesia and Kiribati.
Equador and Brazil are both relatively close
Tits are nice, but I'm all about an oxygen supply.
Finally, math books without any of that base 6 crap in them.
Well to be truthful, if it matters, it won't really matter. If the thing is made of "nano tubes" some fucker flies a plane into it all we will do is hose it off and go right back to business.
Supporting World Peace Through Nuclear Pacification
For example, the base tower would have to be 31 miles high, according to this article. Which is 90 times higher than the current tallest structure on earth, the CN Tower in Toronto, Canada is only 1/3 of a mile (about 170 stories) high.
There is also talk about using carbon nanotubes to make up the cable. The pricetag, 40 billion dollars (see 2nd link).
Panama
You don't need to tether the end, you can still get some very healthy benefits with a partial elevator. Deals with a lot of the security issues too. Cargo craft only need to fly to the low end and ride the rotation to the top where they can slingshot off. Using the Earth's magnetic field and solar power means it's self-stabilising too. More detail and better writing at; Free David Brin Short Story
Just a minor clarification on the parent...
The "slingshot effect" is only useful for trajectory changes. [cut] Due to conservation of energy, when you approach a planet and slingshot away from it, you end up with the same velocity on the way out as the way in.
This is correct enough, but for those who haven't taken an orbital mechanics class, I thought I'd chip in a little bit more info. The 'slingshot' effect seems to work since you (the object) is changing frames of reference into- and out of the planet being used. (The other frame being with respect to the sun.) Additionally, you have to do the approach from the 'backside' so the planet pulls you forward on your way by (assuming you want to gain speed; otherwise enter on the front-side to slow down).
Once you leave the sphere of influence of the planet itself though, and are only under the dominant effect of the sun (i.e., changed frames of reference) you have changed net velocity (speed as well as direction).
All true, but you missed two points:
BZZT!!! No, you're forgetting that the planet has its own velocity, which a spacecraft can steal. When a spacecraft slinshots around a planet, its velocity on the way out is the same as its velocity on the way in, but this the the velocity RELATIVE TO THE PLANET. If the spacecraft approaches the planet head-on, and does a 180 degree slingshot around the planet, then (ideally) its final velocity RELATIVE TO THE SUN is equivalent to its initial velocity plus two times the planet's orbital velocity. Energy is conserved, because the energy gained by the spacecraft is stolen from the planet.
That's "Mr. Soulless Automaton" to you, Bub.
Will the wire generate power?
Yes, but only in the milliwatts.
Tim
Omnia vestra castrorum habetur nobis.
Equator, since (a)the Earth is an oblate spheroid and the Equator is higher than the poles (b) slingshot effect wouldn't apply at the poles. Same logic explains the Russian sea launches which allow rockets to save a chunk of fuel by getting as equatorial as possible and the French using Guyana for Ariadne.
The reason is sheer length -- even if the cable were as conductive as gold, it would have a resistance from the ionosphere down to the Earth's surface of tens of kilo-ohms (see same paper).
Actually, the "free" energy is taken directly from the rotational inertia of the earth itself. So this would slightly increase the length of our day, but only VERY VERY slightly. When you consider the mass of the earth and how fast it spins, you could power all of humanity for much longer then you could imagine before the earth's day was noticably different.
Also, the earth's rotational speed changes gradually anyway...
http://kered.org
The units on the Kelvin scale are officially known as "kelvins".
Google sez:
kelvin (K): A unit of thermodynamic temperature, taken as one of the base units of the International System of Units (SI). The kelvin is defined by setting the thermodynamic temperature of the triple point of water at 273.16 K. Note 1: The kelvin was formerly called "degree Kelvin." The term "degree Kelvin" is now obsolete. No degree symbol is written with K, the symbol for kelvin(s). Note 2: In measuring temperature intervals, the degree Celsius is equal to the kelvin. The Celsius temperature scale is defined by setting 0 C equal to 273.16 K.
Note how there is no degree symbol when writing a tempetature in Kelvins.
From:
http://lamar.colostate.edu/~hillger/temps.htm
we can see
The kelvin (K) temperature scale is an extension of the degree Celsius scale down to absolute zero, a hypothetical temperature characterized by a complete absence of heat energy. Temperatures on this scale are called kelvins, NOT degrees kelvin, kelvin is not capitalized, and the symbol (capital K) stands alone with no degree symbol.
Here's a NASA article on ProSEDS - a shuttle experiment to generate power by dragging a conductive tether through the upper atmosphere. In the initial experiment, the tether generated twice the predicted current, even though the tether didn't deploy properly. If I understand the physical principle behind it correctly, the higher the field differential between the ends of the tether (i.e, the longer the cable), the higher the current generated. A tether extending over many kilometers would be an outstanding power source -- although it's difficult to predict all the possible environmental implications (still, much less than burning tons of fossil fuel everyday.) Also, as with a conventional dynamo/motor, by feeding electricity into the tether, you can use it for propulsion - raising or lowering a vehicle through the upper atmosphere without expending propellant.
Useless.
:
.
You'd have the same problem as with any other potential field
You get access to particle X at extremity X0 of some energy potential field Y, compared to extermity X1
However, in order to use this energy, you have to put something (a wire) between X0 and X1(the two ends of your elevator). This something(wire) however will receive the same field effect, and will cost you the same exact energy amount.
In plain terms, you've got to ship back those electrons to the top of the wire, to get electricity. The more easily they came down, the harder it gets to send them back.
Otherwise, you could do the same in airplanes. Airplanes, while travelling trough the magnetic field of earth build a good potential difference between their wing tips. If you try to use it, though, the wire you put will build the same voltage, preventing you from using this energy.
BTW, that's also why you can't shield gravity.
HTH
J.
There's and interesting, informal dicussion group for this kind of thing at space-elevator@yahoogroups.com