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The space tether experiment, a joint venture of the US and Italy, called for a scientific payload--a large, spherical satellite--to be deployed from the US space shuttle at the end of a conducting cable (tether) 20 km (12.5 miles) long. The idea was to let the shuttle drag the tether across the Earth's magnetic field, producing one part of a dynamo circuit. The return current, from the shuttle to the payload, would flow in the Earth's ionosphere, which also conducted electricity, even though not as well as the wire.
[...]The first attempt at the tether experiment ended prematurely when problems arose with the deploying mechanism, but the one on February 25, 1996, began as planned, unrolling mile after mile of tether while the observed dynamo current grew at the predicted rate. The deployment was almost complete when the unexpected happened: the tether suddenly broke and its end whipped away into space in great wavy wiggles. The satellite payload at the far end of the tether remained linked by radio and was tracked for a while, but the tether experiment itself was over.
[...] Later vacuum-chamber experiments suggested that the unwinding of the reel uncovered pinholes in the insulation. That in itself would not have caused a major problem, because the ionosphere around the tether, under normal circumstance, was too rarefied to divert much of the current. However, the air trapped in the insulation changed that. As it bubbled out of the pinholes, the high voltage ("electric pressure") of the nearby tether, about 3500 volts, converted it into a plasma (in a way similar to the ignition of a fluorescent tube), a relatively dense one and therefore a much better conductor of electricity.
The instruments aboard the tether satellite showed that this plasma diverted through the pinhole about 1 ampere, a current comparable to that of a 100-watt bulb (but at 3500 volts!), to the metal of the shuttle and from there to the ionospheric return circuit. That current was enough to melt the cable.
As the broken end whipped away from the shuttle, the plasma established electric contact with the ionosphere directly. The satellite on the distant end monitored the current: after about half a minute it stopped, then it reignited and flowed again for about another half minute, stopping for good when (presumably) all the trapped air was gone.
[...]But on Feb. 25 after the 12 mile tether began producing electricity an unexpected overload in electrical energy fluctuating between 2 and 10 times that which predicted due to inaccurate estimates in the electrical charge in the earths magnetic field, ionosphere, and possibly space radiation fried the tethers conductor cable and it broke severing it from the space shuttle..."
"This arcing produced significant burning of most of the tether material in the area of the arc," the board found. The tether was designed to carry up to 15,000 volts DC and handle tensile forces of up to 400 pounds (1780 newtons). It used super-strong strands of Kevlar as a strength-providing member, wound around the copper and insulation. However, postflight inspection of the tether end which remained aboard Columbia showed it to be charred. The board concluded that after arcing had burned through most of the Kevlar, the few remaining strands were not enough to withstand forces being exerted by satellite deployment.
Extensive, rigorous tests performed in support of the
investigation established that undamaged tether would not arc,
even when subjected to electrical potentials much higher than
the 3500 volts experienced during the mission.
Scientists and engineers at NASA's Marshall Space Flight Center are developing a test model (left) of such a device that will use Earth's magnetic field to make a rocket stage re-enter the atmosphere in a few days instead of months. If it works, then America will have a powerful new tool to keep satellites up - even to explore the solar system - without using rockets.
It could even trim $2 billion a year off the cost of operating the International Space Station.
It won't quite work the same as a Space Coupe with steerable magnets. Instead, ProSEDS will use a 20 km (12-mile) extension cord that plugs into the magnetosphere and turns the cord into an electric motor that slowly raises or lowers a satellite's orbit.
The concepts behind ProSEDS - the Propulsive Small Expendable Deployer System - are derived from the Tethered Satellite System flown on the Space Shuttle in 1995 and 1996. Although the tether broke as it reached its 19.6 km (12-mile) length on its 1996 flight, scientists gathered a great deal of data about tether behavior during five hours of operation.
When further analysis suggested that several ProSEDS key performance parameters could not be met, NASA decided not to fly the ProSEDS mission. It is thought that this decision was due, at least in part, to the feeling that the tether lifetime would not be sufficient to accomplish mission goals. It was expected that particle impacts on the tether would compromise the insulating properties of the insulated portion of the tether before mission science goals could be met. In addition, tightening of ISS safety requirements required an alteration of the ProSEDS orbit to such an extent that ProSEDS mission requirements and equipment performance could not be made to satisfy the emerging ISS safety requirements within the constraints of time and budget.
That was kind of the idea, to generate a large voltage, even going back to the previous tether experiment STS 46 which was planned to generate 5000 volts, as Zorgon posted about in 2008:
originally posted by: Arken
Do You remember the Tether Experiment, the STS-75 Tethered Satellite System deployment in 1996? Something went wrong, but the scientists were able to detect something amazing, measure and test before the satellite went adrift in space: An ENORMOUS amount of ENERGY...
Why we never heard something new about this epochal break thorough? Why no new developments in energy production from it?
So we DID hear about it and anybody who wanted to know what the tether experiments were about could find the information like Zorgon did.
originally posted by: zorgon
below is the full report of the OTHER tether experiment STS 46 and you thought.....
...
Speeding through the magnetized ionospheric plasma at
almost 5 miles per second, a 12-mile-long conducting tethered
system should create a variety of very interesting plasma-
electrodynamic phenomena. These are expected to provide unique
experimental capabilities, including the ability to collect an
electrical charge and drive a large current system within the
ionosphere; generate high voltages (on the order of 5
kilovolts) across the tether at full deployment; control the
satellite's electrical potential and its plasma sheath (the
layer of charged particles created around the satellite)
Yet NASA reports... and Lockheed reports... and commission reports have all this info easily (well okay not THAT easily ) found in public sites?
originally posted by: Arken
a reply to: theantediluvian
Thanks for the add-on
The thing about energy is you not only have to produce it, you have to deliver it to a customer or user. That's not easy to do when the source is in orbit and the customers are all on Earth. The ISS already has solar panels. I'm not sure what you expect.
originally posted by: Arken
Do You remember the Tether Experiment, the STS-75 Tethered Satellite System deployment in 1996? Something went wrong, but the scientists were able to detect something amazing, measure and test before the satellite went adrift in space: An ENORMOUS amount of ENERGY...
Why we never heard something new about this epochal break thorough? Why no new developments in energy production from it?
originally posted by: nataylor
1 amp at 3500 volts is not an enormous amount of energy. That's about what two and a half household vacuum cleaners would use.
problem is, if the wires are close to each other, they'll essentially short circuit each other, as the principle depends on the free flow of electrons at the end of the tether. If a number of tethers are all connected to one central capacitor, they'll have a tendency to orient themselves all in the same direction, so they'll end up too close to each other even if they start out far apart.
originally posted by: VoidHawk
True, but imagine if the tether had multiple wires, and they were all feeding into a massive capacitor. As a pulse the energy could be enormous, maybe large enough to feed a mega powerful laser device that could destroy any target it was aimed at, be it in space or on earth!
It would be much easier and cheaper to use some solar panels if you're looking to generate a couple kilowatts of electricity.