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.
Actually that has been addressed, several times. In fact, look up thread just a few posts and you find a few.
That all depends on how fast you lift it, how tight the cable is, and the mass of the assembly.
Never mind all the questions then as they're irrelevant in that type of setup.
Thanks anyway.
The horizontal force you mention is refered to as what's needed to counteract "coriolis" acceleration.
And I was wrong about the counterweight out at 62,000 miles being at a horizontal velocity of 41,000 miles per hour. My brand new calculator tells me that the actual horizontal velocity of the distant counterweight is on the order of 18,000 mph.
So if the tether ever separated, the counterweight would not fly off into space, never to return, but would, instead, loop up in a tremendous eliptical path and pay a splashing visit to the earth a little later, with whatever "tail" was still attached to it following.
And any payload lifted to that height and released would still need rocket assist to achieve escape velocity. Also, any payload attached to the ribbon between 22,000 miles (geosynchronous orbit) and 62,000 miles will be adding to the tension on the Earth anchor.
another space tether:
http://spaceflightnow.com/news/n0709/15foton/
Recoverable craft shot into space for science mission
BY STEPHEN CLARK
SPACEFLIGHT NOW
Posted: September 15, 2007
Russia launched a recoverable capsule crammed with more than 1,300 pounds of international scientific and engineering test experiments on Friday to begin a 12-day excursion in space.
The Foton M3 capsule, loaded with an array of Russian and European payloads, was launched at 1100 GMT (7:00 a.m. EDT) aboard a Soyuz rocket from the Baikonur Cosmodrome in Kazakhstan.
A carrier called FLOYD on the Foton capsule will unreel nearly 19 miles of tether material in the early morning hours Sept. 25. A 12-pound craft called Fotino and a disposable instrumentation box known as MASS will be attached to the end of the tether, which is as thin as a typical fishing line.
Fotino will fly ahead and below the Foton spacecraft during much the automated two-and-a-half hour activation and deployment process. At the time of Fotino’s release, the capsule will be in a gravity-induced backward swing relative to Foton, according to Michiel Kruijff, technical director for Delta-Utec and lead engineer for the YES2 mission.
Fotino will become the smallest spacecraft to re-enter Earth’s atmosphere, and the nearly 20-mile length of the tether will make it the longest ever flown in space.
Tethered delivery systems could provide opportunities for inexpensive return options for small payloads in orbit. Engineers have considered using such systems to return equipment from the international space station, but Kruijff said safety issues will likely thwart those concepts.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.