Orbital energy

[AtomSplitter]

Does anyone think that it might be possible to harness the kinetic energy of an object in orbit and change it to electrical energy? If so, could we built special staions to orbit and harvest? or could we use the moon?

[insane_alien]

you do realise that by taking the kinetic energy of something in orbit and converting it to electricity will cause the object to lose orbit and crash into the earth don't you?

[AtomSplitter]

In that case, use an uninhabited planet. that solves that problem, and if we choose one with a stronger gravity, surely the energy gained would be greater?

[insane_alien]

you also realise that in getting something INTO orbit we have to put that much energy into it?

 

so it doesn't really generate any energy over all.

[AtomSplitter]

is it was an object taken from a low gravity planet, then surely it would take less energy to get it off the planet than it would produce in falling to one with a much stronger gravity?

 

If, for example we take a large chunk of mass from a planet with a weak gravity and use a set amount of energy to propell it out of it's orbit and through space to another plantet where the energy is removed when it is in orbit will that energy not be greater than the energy required to get it there?

[Klaynos]

or use a natural moon that's already there

 

The space shuttle actually lowers a long cable to create energy on board, it only does this when it wants to slow and drop into a lower orbit though...

[AtomSplitter]

wouldn't that cause massive destruction and possibly render the planet useless as the impact may destroy the planet?

[Klaynos]

I doubt a moon from orbit could "destroy" a planet... Especially as most of it's energy would be harvested in this idea....

[AtomSplitter]

if a moon collided with a planet it is possible that its orbit may be ever so slightly altered and that may result in a chain of events that could lead the planet crashing into another (THAT would be a good energy producer) or into a sun. surely it is reasonable then to limit the size of objects that you want falling into a planet so as to not disturb it overly much? or would it not matter?

[swansont]

Does anyone think that it might be possible to harness the kinetic energy of an object in orbit and change it to electrical energy?

 

Yes.

 

http://science.ksc.nasa.gov/shuttle/missions/sts-75/mission-sts-75.html

[AtomSplitter]

i couldnt find anything on that link but thx anyway, im not very good at finding things! do you (swansont)think that havind a moon collide with a planet could be a very bad thing?

[D H]

The space shuttle actually lowers a long cable to create energy on board, it only does this when it wants to slow and drop into a lower orbit though...

The Shuttle has released a long cable with a satellite on the end, twice. The goal was to generate electrical power, not change the orbit. TSS-1 flew on STS-46. Mechanical problems arose after releasing only 256 meters of cable. The engineers went back to the drawing board. TSS-1R flew on STS-75. This time they managed to release 19.7 kilometers of cable before the cable broke. Two strikes and you're out. NASA has not flown a tether experiment on the Shuttle since.

[Martin]

Atom splitter, the topic of the thread is using orbital energy to generate electricity. Let's focus. It's interesting. You asked a good question.

Does anyone think that it might be possible to harness the kinetic energy of an object in orbit and change it to electrical

energy?

 

Swansont gave you a direct answer. Pointing to an interesting NASA experiment which does just that, in a very clever way. The answer to your question is:

Yes.

 

http://science.ksc.nasa.gov/shuttle/missions/sts-75/mission-sts-75.html

 

Now it is up to you to follow up and actually explore the link! Did you really try?

 

i couldnt find anything on that link but thx anyway, im not very good at finding things! do you (swansont)think that havind a moon collide with a planet could be a very bad thing?

 

The scheme for the electric generator is right there in the press kit, one click away.

http://science.ksc.nasa.gov/shuttle/missions/sts-75/sts-75-press-kit.txt

It does exactly what you asked about and it is described clearly. A rather elegant method. Here's a quote from the press-kit:

The conducting tether's generator mode will produce

electrical current at a high voltage, using the same basic

principle as a standard electrical generator. A small

portion of the mechanical energy of the Shuttle's more than

17,500-mile-an-hour orbital motion will be converted into

electrical energy as the electrically conducting metal

strands in the tether's core pass through Earth's magnetic

field lines.

 

The conductive outer skin of the Tethered Satellite

will collect free electrons from the space plasma, and the

resulting voltage will cause the electrons to flow down the

conductive tether to the Shuttle. An electron accelerator,

also called an electron gun, will then eject them back into

space. Scientists expect the electrons to travel through the

ionosphere to complete the loop required to close the

circuit, just as a wire must close the circuit between the

positive and negative poles of a car battery before current

will flow. They will use a series of interdependent

experiments -- conducted with electron guns and tether

current-control hardware along with a set of diagnostic

instruments -- to assess the nature of the external current

loop within the ionosphere. This also will shed light on the

processes by which the circuit is completed at the satellite

and the Shuttle.

 

There certainly would be situations (like a small satellite of Jupiter where you don't care if it loses a tiny percent of its energy and orbits a tiny tiny percent closer to Jupiter after many years) where it wouldn't be harmful to convert some of the orbital energy into electric. That is not the issue. It doesnt have to lead to crash. The important thing us understand the means. You asked a question. People have already thought about that question. An answer is known. You are told the answer. Now your job, to hold up your end of the conversation, is to understand the answer.

 

Do you understand how the electricity is generated, in this system? If you don't, shouldn't you ask and get somebody to explain?

Edited October 21, 2008 by Martin

[AtomSplitter]

thank you very much, i found it now! i looked through everything else on that link without succes. Now, just a thought, could we do it in the forseeable future?

[CaptainPanic]

Um...

Orbital energy, isn't that what we more conveniently call tidal energy? I mean, the fact that the moon turns around our earth, and the rotation of the earth itself, cause the tides (ok, the sun is involved too, but less).

 

The movement of all that water must cause some friction. Then, where does this energy come from? I mean, you cannot shamelessly turn the kinetic or potential energy of water into (first electricity and then) heat, and then expect the water to do the same thing tomorrow again... There is a law against that

 

My bet is that we're reducing the rotational speed of the earth... or slowing down the moon. Slowing down the rotation of the earth seems more logical (but I don't know for sure).

 

Therefore, using tidal energy for electricity production is using "orbital energy", isn't it?

 

I've waited a bit before I hijack this thread... but it seems that all previous items have been resolved. Our thread-starter (AtomSplitter) thanks you all... (ok, and he came with another question ).

[Martin]

Um...

Orbital energy, isn't that what we more conveniently call tidal energy?.

 

No, Captain,

Tidal power generation primarily taps the earth's rotational energy. If tide power were harnessed it would have a very slight effect of slowing down the rotation of the earth (very very slightly)

 

It would not tap the moon's orbital energy---would actually pump some in and build it up slightly. I think you have the effect backwards. (think of moon's orbital energy as part kinetic and part potential, taking energy out actually speeds moon up, pumping in slows her down, in any case irrelevant---tidal does not tap moon's orbital energy, it taps earth's rotational, as you thought it might.)

 

Let's stay on topic. Atom posed a nice problem. Tapping orbital energy. Let's stick to that and think about it. It's not the same as rotational. I'd ask you to make another thread if you want to talk about tapping rotational energy.

 

 

thank you very much, i found it now! i looked through everything else on that link without succes. Now, just a thought, could we do it in the forseeable future?

 

I'm glad you found it! Can you picture it? As you picture it, does the tether with the small satellite on the end extend outwards from the Shuttle? Away from the earth--"up" so to speak.

Or does it extend "down" from the Shuttle? In towards the earth.

 

Which do you think? I think upwards. Let's assume that. Here's an exercise using the Righthand Rule.

Suppose the Shuttle is going from west to east, and the earth magnetic field lines are going northwards (geographically, from south hemisphere to north hemisphere), which way do the electrons in the tether cable want to go?

 

It's a nice beginning physics problem. Anybody?

 

Atom, I doubt that it is a way to solve the earth's energy problems. You need something orbiting in a reasonably strong magnetic field, and the moon is not. The body has to ALREADY be orbiting in a strong magnetic field because otherwise it costs energy to establish the orbit. You pay big up front and then tap little by little. But in the solar system there are bodies that are already orbiting in a strong magnetic field. Jupiter satellites come immediately to mind.

 

You say "could we in the foreseeable future?" Sure just as soon as people (or their robot surrogates) find it practical to colonize the Jovian satellites. If that is the foreseeable future then clearly there's no problemo!

 

In my view the fundamental barrier to that sort of colonizing is that we meat-bags are so vulnerable to radiation. The quickest way to colonize an environment like that is to program human souls into robots. Then let the robots experience the thrill of setting up civilization in novel places. They wouldn't be so bothered by things like vacuum, cold, heat, dryness, lethal solar-flare radiation etc etc.

Edited October 21, 2008 by Martin