BS: Space Elevator in work

Subject: RE: BS: Space Elevator in work
From: HuwG
Date: 29 Sep 08 - 01:51 AM

I've been re-reading Kim Stanley Robinson's "Red Mars". Robinson's cable was ten meters in diameter. It weighed six billion tons. Its anchor point in orbit was an asteroid named "Clarke", which weighed seven and a half billion tons.

Clarke would have been outside the asynchronous orbital altitude of 17,049 Km, measured from the surface. My calculator bashing suggests that Clarke is very roughly 2944 Km beyond the asynchronous orbit, at an altitude of 19,993 Km.

The system can be treated as a single mechanical unit with its centre of gravity at the asynchronous altitude.

When the terrorists pulled the cable out of Clarke, the cable suddendly became a separate unit with a cen

Subject: RE: BS: Space Elevator in work
From: HuwG
Date: 29 Sep 08 - 02:05 AM

Ack! Damn' submit button!

To continue, the cable suddenly becomes a separate unit, with its centre of gravity 9,900 Km above the surface. I'll have to sleep on this, to work out how conservation of energy affects matters, but I suspect the cable will immediately acquire apparent horizontal velocity in the direction of the planet's rotation i.e. the cable will appear to fall forwards, rather than be dragged around by the planet. Once this forward motion is acquired, it will be combined with the downward acceleration due to gravity to indeed wrap the planet.

I suspect that even if I am wrong, the cable will have sufficient rigidy to prevent it simply falling vertically and creating a pan-scrubber which would undoubtedly make the "Guiness Book of Records".

Subject: RE: BS: Space Elevator in work
From: beardedbruce
Date: 29 Sep 08 - 07:21 AM

A significant point not yet discussed:

IF the upper end point is used as a s/c launch point, the object falling off of it will have a velocity in excess of the orbbital velocity at that distance- ie, it will get a boost towards whatever destination it has, as soon as it separates from the "elevator"


Not a bad investment- both access to orbit and a launch capability to the rest of the solar system.

Subject: RE: BS: Space Elevator in work
From: GUEST,beardedbruce
Date: 03 Oct 08 - 11:54 AM

updated 1 hour, 37 minutes ago

   'Space elevator' would take humans into orbit

Story Highlights
Japan group has more than 100 engineers trying to design a space elevator

Carbon nanotube would be used as a wire to lift the elevator into space

Western Australia and the Galapagos Islands are potential locations for base station

Group sets the 2030s as a target to begin construction, although it could be later

By Mike Steere
For CNN

   
LONDON, England (CNN) -- A new space race is officially underway, and this one should have the sci-fi geeks salivating.

The project is a "space elevator," and some experts now believe the concept is well within the bounds of possibility -- maybe even within our lifetimes.

A conference discussing developments in space elevator concepts is being held in Japan in November, and hundreds of engineers and scientists from Asia, Europe and the Americas are working to design the only lift that will take you directly to the one hundred-thousandth floor.

Despite these developments, you could be excused for thinking it all sounds a little far-fetched.

Indeed, if successfully built, the space elevator would be an unprecedented feat of human engineering.

A cable anchored to the Earth's surface, reaching tens of thousands of kilometers into space balanced with a counterweight attached at the other end is the basic design for the elevator.

It is thought that inertia -- the physics theory stating that matter retains its velocity along a straight line so long as it is not acted upon by an external force -- will cause the cable to stay stretched taut, allowing the elevator to sit in geostationary orbit.

The cable would extend into the sky, eventually reaching a satellite docking station orbiting in space.

Engineers hope the elevator will transport people and objects into space, and there have even been suggestions that it could be used to dispose of nuclear waste. Another proposed idea is to use the elevator to place solar panels in space to provide power for homes on Earth.

If it sounds like the stuff of fiction, maybe that's because it once was.

In 1979, Arthur C. Clarke's novel "The Fountains of Paradise" first brought the idea of a space elevator to a mass audience. Charles Sheffield's "The Web Between the Worlds" also featured the building of a space elevator.

But, jump out of the storybooks, fast-forward nearly three decades and Japanese scientists at the Japan Space Elevator Association (JSEA) are working seriously on the space-elevator project.

JSEA spokesman Akira Tsuchida told CNN his organization was working with U.S.-based Spaceward Foundation and a European organization based in Luxembourg, to develop an elevator design.

The Liftport Group in the U.S. is also working on developing a design, and in total it's believed over 300 scientists and engineers are engaged in such work around the globe.

NASA is also holding a $4 million Space Elevator Challenge to encourage designs for a space elevator than can work.

Tsuchida said the technology driving the race to build the first space elevator is the quickly developing material carbon nanotube. It is lightweight and has a tensile strength 180 times stronger than steel cable. Currently, it is the only material with the potential to be strong enough to use to manufacture elevator cable, according to Tsuchida.

"At present we have a tether which is made of carbon nanotube, and has one third or one quarter of the strength required to make a space elevator. We expect that we will have strong enough cable in the 2020s or 2030s," Tsuchida said.

He said the most likely method of powering the elevator would be through the carbon nanotube cable.

So, what are the major logistical issues keeping the space elevator from being anything more than a dream at present?

Massachusetts Institute of Technology (MIT) Aeronautics and Astronautics Professor, Jeff Hoffman, said designing the carbon nanotube appeared to be the biggest obstacle.

"We are now on the verge of having material that has the strength to span the 30,000 km ... but we don't have the ability to make long cable out of the carbon nanotubes at the moment." he said. "Although I'm confident that within a reasonable amount of time we will be able to do this."

Tsuchida said one of the biggest challenges will be acquiring funding to move the projects forward. At present there is no financial backing for the space elevator project and all of JSEA's 100-plus members maintain other jobs to earn a living.

"Because we don't have a material which has enough strength to construct space elevator yet, it is difficult to change people's mind so they believe that it can be real," he said.

Hoffman feels international dialogue needs to be encouaraged on the issue. He said a number of legal considerations also would have to be taken into account.

"This is not something one nation or one company can do. There needs to be a worldwide approach," he said.

Other difficulties for space-elevator projects include how to build the base for the elevator, how to design it, and where to set up the operation.

Tsuchida said some possible locations for an elevator include the South China Sea, western Australia, and the Galapagos Islands in the Pacific Ocean. He said all of those locations usually avoided typhoons, which could pose a threat to the safety of an elevator.

"As the base of space elevator will be located on geosynchronous orbit, [the] space elevator ground station should be located near the Equator," he said.

While JSEA has set a time frame of the 2030s to get a space elevator under construction -- and developments are moving quickly -- Hoffman acknowledges it could be a little further away than that.

"I don't know if it's going to be in our lifetime or if it's 100 or 200 years away, but it's near enough that we can contemplate how it will work."

Building a space elevator is a matter of when, not if, said Hoffman, who believes it will herald a major new period in human history.

"It will be revolutionary for human technology, and not just for space travel. That's why so many people are pursuing it," he said. "This is what it will take to turn humans into a space-bearing species."

Subject: RE: BS: Space Elevator in work
From: NightWing
Date: 03 Oct 08 - 10:03 PM

HuwG said, "One [space elevator] on earth had to be bifurcated ('Y' shaped) near the base so that one leg was anchored in Trinidad and the other in Tobago."

Trinidad & Tobago are on a single island, about 80 km across, located about (VERY!!! roughly) 5° (five degrees) north of the equator. If the ends of a bifurcated space elevator were located both in--more or less--the same place like that they would act as a single end ... 5° OFF the equator. As it orbited it would swing through a curve from 5° north to 5° south on a 24-hour cycle. Hard to get on or off an elevator that's moving about 25 km/hr (on average).

Instead Robinson's bifurcated space telescope had one end in T&T and the other that far SOUTH of the equator. La Paz (in Bolivia), Cuiabá, or Brasilia (both in Brazil) are three possible choices. (I don't remember where Robinson had his, although I just read the trilogy a couple months ago.)

BB,
NightWing

Subject: RE: BS: Space Elevator in work
From: GUEST,beardedbruce
Date: 07 Oct 08 - 07:09 AM

refresh

Subject: RE: BS: Space Elevator in work
From: Zen
Date: 07 Oct 08 - 09:19 AM

Whilst it might be theoretically possible to design such a tethered structure, in practice no materials currently exist with the necessary tensile strength... even carbon nanotubes would fall somewhat short of what would be required. If a way could be found to produce the current favoured candidate material, carbon nanotube fibres (ideally single-walled from a mass point of view) in sufficient quantities and with sufficient lengths to be woven, braided and bound into a tether with the required mechanical characteristics there could still be potential problems such as the likely electrical conductivity of such a cable.

I'm not dismissing the idea per se but the quoted Japanese target of 2030 would seem a little optimistic given current technology.

Subject: RE: BS: Space Elevator in work
From: McGrath of Harlow
Date: 07 Oct 08 - 05:52 PM

Trinidad & Tobago are on a single island,

No they aren't. Here's a map, courtesy of the CIA. (I know the CIA don't always get things right, but this time they did.)

Subject: RE: BS: Space Elevator in work
From: gnu
Date: 01 Jan 11 - 06:06 PM

Pie in the sky?


Sorry if this was posted previously.

Subject: RE: BS: Space Elevator in work
From: Slag
Date: 02 Jan 11 - 03:36 AM

The "Crawlers" or elevator cars would have the capability to micro examine and do repairs to the cables. The cable itself might act as an electrostatic inducer and supply some or all the current necessary to operate the powerful engines required to move massive loads up and down or, more correctly, in and out of Earth's gravity well. An absolute "no-fly" zone of a thousand miles radius might be established to repel crazies from assaulting the machine. Similar restrictions on all water borne vessels. Space junk and meteoroids would be an ever constant source of danger as the cables are completely immovable but here, stand-off sheilding could be employed and maintained as are low-orbit satellites. Vessels docking and undocking with the counter weight ( a small metalic asteroid perhaps ) would also present engineering problems and, potentially, a great hazzard, should an accident occur. The escapablility of the crawlers, especially smaller ones for living passngers only, is easily handled. Cargo only crawlers would need the 1000 mile buffer zone to avoid immediate damage to Earth, other than the anchor points. Twenty thousand and some odd miles of sharp and ridgid nano-carbon cables would present an enormous hazzard to Earth dwellers. It would fall at super-sonic speeds and slice through most materials it encountered.

If we Earthlings had the ability to do this project it should first be attempted on the Moon where unforseen problems would not endanger Earth's inhabitants. The prototype would be beneficial to Lunar enterprizes in much the same way a space elevator would directly benefit Earth. Regardless we need an established permanent presence in the Earth Moon system to even begin and maintain the industries needed to accomplish such a grand endeavor.

Subject: RE: BS: Space Elevator in work
From: GUEST,Shimrod
Date: 02 Jan 11 - 09:35 AM

"Twenty thousand and some odd miles of sharp and ridgid nano-carbon cables would present an enormous hazzard to Earth dwellers. It would fall at super-sonic speeds and slice through most materials it encountered."

Yep! I once saw a few tons of scaffolding collapse from a 4 or 5 storie building. The energy released by this event was amazing with 18 ft scaffolding poles tied into knots! The effect of a collapsing space elevator doesn't bear thinking about.