Posted on 02/15/2006 10:24:11 AM PST by Neville72
In January, LiftPort team members deployed a mile-long tether with the help of three large balloons in the Arizona desert (N Aung/LiftPort Group)Related Articles A slim cable for a space elevator has been built stretching a mile into the sky, enabling robots to scrabble some way up and down the line.
LiftPort Group, a private US company on a quest to build a space elevator by April 2018, stretched the strong carbon ribbon 1 mile (1.6 km) into the sky from the Arizona desert outside Phoenix in January tests, it announced on Monday.
The company's lofty objective will sound familiar to followers of NASA's Centennial Challenges programme. The desired outcome is a 62,000-mile (99,779 km) tether that robotic lifters – powered by laser beams from Earth – can climb, ferrying cargo, satellites and eventually people into space.
The recent test followed a September 2005 demonstration in which LiftPort's robots climbed 300 metres of ribbon tethered to the Earth and pulled taut by a large balloon. This time around, the company tested an improved cable pulled aloft by three balloons.
Rock solid To make the cable, researchers sandwiched three carbon-fibre composite strings between four sheets of fibreglass tape, creating a mile-long cable about 5 centimetres wide and no thicker than about six sheets of paper.
"For this one, the real critical test was making a string strong enough," says Michael Laine, president of LiftPort. "We made a cable that was stationed by the balloons at a mile high for 6 hours…it was rock solid."
A platform linking the balloons and the tether was successfully launched and held in place during the test. LiftPort calls the platform HALE, High Altitude Long Endurance, and plans to market it for aerial observation and communication purposes.
But the test was not completely without problems.
The company's battery-operated robotic lifters were designed to climb up and down the entire length of the ribbon but only made it about 460 m above ground. Laine told New Scientist that the robots had worked properly during preparatory tests and his team is still analysing the problem.
Carbon nanotubes In March, LiftPort hopes to set up a HALE system in Utah's Mars Desert Research Station and maintain it for three weeks. Then, later in the spring, Laine says he wants to test a 2-mile (3.2-km) tether with robots scaling to at least half way up.
Laine aims to produce a functioning space elevator by 2018 – a date his company chose in 2003 based on a NASA Institute for Advanced Concepts study, which said an elevator could be built in 15 years. "This is a baby step, but it's part of the process," he says of LiftPort's recent test.
The idea is to build the actual elevator's ribbon from ultra-strong carbon nanotube composites and to have solar-powered lifters carry 100 tonnes of cargo into space once a week, 50 times a year.
Beams and climbers Laine sits on the board of the California-based Spaceward Foundation, which partnered with NASA to put on two space-elevator-related competitions that were the first of the agency's Centennial Challenges programme – the Tether Challenge and the Beam Power Challenge.
The first is designed to test the strength of lightweight tethers while the beam challenge tests the climbing ability and weight-bearing capability of robots scaling a cable. Laine’s team is not competing in the NASA challenges so there is no conflict of interest.
In October 2005, none of the competition entrants performed well enough to claim the twin $50,000 purses. But the challenges are scheduled to take place again in August 2006 with $150,000 top prizes. Nineteen teams have signed up for the beam power challenge so far and three will compete in the tether challenge.
Ben Shelef, founder of the Spaceward Foundation, hopes the competitions will drum up interest and drive technological innovation. He told New Scientist he is pleased to hear of LiftPort's successful test. "A journey of a thousand miles starts with a single step," he says.
Waste of money and time.
If your future-predicting abilities are as good as your understanding of basic physics, I'm almost certain it will eventually be built. If the Wrights had listened to people like you we'd still be taking a 4 day train trip to cross the country, instead of a 4 hour flight.
YOu have a helium balloon that is perfectly bouyant. It floats at a constant rat - doesn't go up or down with a static atmospheric pressure.
You have a string with a wieght tied to it...the wieght is on the ground and you give the ballon a slight push to give it a bit of pressure to tighten the string.
Now, put a fan to the middle of this string... what happens, the ballon is forced to move down....
In the vacuum of space, there isn't any opposing force to stop this balloon from returning. Infact, gravity will cause the ribbon to continue to move downward.
Your ball and string principle works well when you have equal amounts of gravity effecting the objects in question... But in this theory, you do not...
You have a helium balloon that is perfectly buoyant. It floats at a constant rate - doesn't go up or down with a static atmospheric pressure.
You have a string with a weight tied to it...the weight is on the ground and you give the balloon a slight push to give it a bit of pressure to tighten the string.
Now, put a fan to the middle of this string... what happens, the balloon is forced to move down....
In the vacuum of space, there isn't any opposing force to stop this balloon from returning. In fact, gravity will cause the ribbon to continue to move downward.
The weight of the cable to the outer atmosphere would. Your ball and string principle works well when you have equal amounts of gravity effecting the objects in question... But in this theory, you do not...
The only other feasible way - unlikely though, is to set up a target satelite and start building from both ends...
Here's the practicality of this dumb idea...
Command control to maintenance,"We have a stuck robot at 15,000...". "maintenance,"Is that feet or miles this time"? Control,"lemme check". Command,"Miles". Maintenance,"Ok, fire up the shuttle, here we go again....".
You have a helium balloon that is perfectly buoyant. It floats at a constant rate - doesn't go up or down with a static atmospheric pressure.
You have a string with a weight tied to it...the weight is on the ground and you give the balloon a slight push to give it a bit of pressure to tighten the string.
Now, put a fan to the middle of this string... what happens, the balloon is forced to move down....
In the vacuum of space, there isn't any opposing force to stop this balloon from returning. In fact, gravity will cause the ribbon to continue to move downward.
The weight of the cable to the outer atmosphere would. Your ball and string principle works well when you have equal amounts of gravity effecting the objects in question... But in this theory, you do not...
The only other feasible way - unlikely though, is to set up a target satelite and start building from both ends...
Here's the practicality of this dumb idea...
Command control to maintenance,"We have a stuck robot at 15,000...". "maintenance,"Is that feet or miles this time"? Control,"lemme check". Command,"Miles". Maintenance,"Ok, fire up the shuttle, here we go again....".
I love aircraft...If the Wrights didn't do it I would have. I have been involved with aerodynamics and Space for a long time before working on computers, working with airlines and NASA at Wallops Island (Eastern Shore, VA)Conestoga project.
I do not claim to have future predicting capabilities...
However I am certain that this idea will not work. better to build a halfway station and build out that way, no tethering to the earth... that would be catastrophical...
Why haven't we fired a cable to earth from the shuttle to see if it can be done... I mean it's orbit is certainly closer to earth to test, it's mass is big enough to similate a counterweight...
I am not telling anyone to not believe, I am saying look at reality...
OMG. I don't even know how to respond to this level of ignorance.
(Note: I said ignorance, not stupidity.)
Robert
Do you want to give this a try? Your ability to explain technical matters is exemplary, and may possibly be up to the task of bring Zavien up to speed.
I suppose I could try, but I'm not as proficient as you seem to be.
AGAIN, because you MUST use geostationary orbit, which the shuttle cannot obtain.
I don't know how much more of this I can take.
BTW, have you contacted NASA yet regarding the reason satellites won't stay in orbit? Their being no "anti gravity" to keep them up and all that?
I am not ignorant to Geo synch orbits. This ...elevator isn't going into a geo stationary orbit. I understand that the concept of a geosynch is being used, but it is not possible with out the use of rockets to keep it in orbit, adjustments and such...
BTW, It's gravity that keeps those birds in orbit, but also the residual velocity to keep it just out of range (use of Newton here)...
However due to the mass of said object is smaller than earth, they require additional adjustments to keep them from coming in contact of the surface... hence the reason we can stand on Terra firma -
and why can't the shuttle maintain a geosynch orbit? The size of a counterweight would have to be much larger than the shuttle to handle the weight of the cable for that distance. ever fly a kite? was the string ever go straight or did it curve because of weight?
Bet that thing falling down
I would think they would want to put the base of that thing on a mountaintop instead of of the coast of Florida or some Carribean island (for a really secure foundation of a mountain of hard rock, and to get a head start on the height) some where out West (Colorado or some such).
Sounds more like a ribbon to me.
OK, look, I'm not a science teacher and explaining this well is beyond my ability. But clearly a lot of very smart people believe there is no barrier to building to a space elevator, in theory. The only real barriers are practical - strong enough materials, protection against terrorists, space debris, and so on. Do a search on Google and read up on it. The people who are thinking about this are a lot smarter than me, and presumably you, too, and they believe it's possible, at least in theory.
Is it practically impossible? Maybe, maybe not. I suspect it'll be a lot more than 15 or 20 years before one is built, if ever. But I could be wrong. Back in 1980 who envisioned the WWW, or even the common powerful desktop computers that we have, or that the Soviet Union would be gone in 10 years?
Let's assume a desired maximum payload height of 22,000 miles and maximum weight/mass of 100 tons. That means we'll need a pulley at 44,000 miles supporting both the payload and the 100 ton counterweight.
The ribbon extends to 62,000 miles. Place a weight/mass there such that the centripetal force equals 200 tons plus the weight/mass of the ribbon. You could now disconnect the ribbon from the ground.
The rising payload will need to be accelerated horizontally and the descending counterweight decelerated. Lots of wasted energy.
Well done!
"and why can't the shuttle maintain a geosynch orbit?"
Because it isn't capable of achieving a geosynch orbit. It is not capable of carrying enough fuel into low-earth orbit to boost itself into a geosynch orbit. If it could reach geosynch orbit and shoot a cable towards earth, it would have to shoot out a counterweight in the opposite direction at the same time, to keep its centre of gravity at the geosynch point.
BTW, geosynch sattelites will not fall out of orbit without constant adjustments. But due to the pull of the moon and other bodies its orbit will eventually become elliptical and non-geo-synch. OK, I suppose the orbit might eventually become elliptical enough for the sattelite to start running into some thin atmosphere and start bleeding off some of its energy, at which point it would start to lose altitude and inevitably fall out of orbit.
As a physicist, I won't argue with that.
The idea IIRC is to start at geosynch and work both ways. Kinda like building a sandcastle on a teeter-totter.
The tension on the structure will be greatest somewhere along the length and near zero where it attaches to earth. Even with the new miracle material the thickness at the point of greatest tension will be substantial.
"The system must remain in equilibrium, once set up. This means a counterweight to the payload."
Not really - there's no reason you can't add more mass to the system. The energy to acclerate the payload horizontally as it climbs comes, in the end, from the earth's angular momentum - every bit of mass we send up the space elevator will steal of bit of the earth's momentum. I suspect we would have to send a significant amount of the earth's mass up it before it would affect the angular velocity of the earth's rotation, though, and given how massive the earth is I don't think that's likely to be a problem.
C'mon, guys, some very smart people have figured this out and can show that it is workable, at least in theory. I think we can take their word on that part, at least.
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