Reythia
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Re: Gliese 581 - Habitable?
Haha! As soon as we can see it, Firle, which will probably be a long time coming. 
I keep telling them, I'm willing to be on the spaceship going there! ...Of course, I've said that about Mars too, and here my feet are, still firmly planted on good ole Earth.
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1/7/2008, 10:56 pm
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Reythia
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Re: Gliese 581 - Habitable?
Well, the odd thing is, Mars isn't REALLY a dream. It's perfectly acheivable with today's technology -- and engineers and scientists have known that for at least thirty years! But for some reason, the government and society at large doesn't want to believe that. It's really quite strange.
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1/8/2008, 7:03 pm
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Reythia
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Re: Gliese 581 - Habitable?
Agreed. 
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1/8/2008, 7:25 pm
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Blitzen
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Re: Gliese 581 - Habitable?
Couldn't we get natural resources off the moon or mars? I'm not sure what, but there is always scifi stories of lunar mines and things so there must be something up there we want.
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7/1/2008, 10:00 pm
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Loud G
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Re: Gliese 581 - Habitable?
Very cool article! That is exciting 
--- Reading: Mistborn
Writing: Eriadhin
"Life is like a book, except it takes longer to get to the climax."
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7/2/2008, 2:19 pm
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Reythia
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Re: Gliese 581 - Habitable?
quote:
Blitzen wrote:
Couldn't we get natural resources off the moon or mars? I'm not sure what, but there is always scifi stories of lunar mines and things so there must be something up there we want.
Well, yes. But at what cost? Now, if you're going to make a Lunar or Martian base, then you definitely want to mine the surfaces of those planetary bodies for building materials. (Most modern Mars missions involve doing this.) But it costs a LOT of money to get equipment up to the Moon or Mars, and more to bring materials back to Earth. (Stupid gravity gradient!) And there's really not much up there that we can't manufacture more easily down here.
In the long run, mining near-Earth asteroids will probably be cheaper, since there's no (noticable) gravity field around those asteroids to push against when you go to bring the materials home. Also, some of the older asteroids are made of rather interesting (and potentially lucrative) elements that are rare on the surface of the Earth. Mind you, in order to do this, we'd need some "practice" missions first -- probably the first would be a simple sample-and-return mission. Alas, though plans for such missions have existed for a decade (probably longer), funding does not.
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7/2/2008, 3:57 pm
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QS2
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Re: Gliese 581 - Habitable?
Sample return id plenty sophisticated enough for a near earth asteroid though, we've brought stuff back from the moon and comets after all.
Which gets us I guess to the real problem, no one yet is willing to pay the amount required to make space mining and other such activities affordable. Though in better news, space solar power is starting to draw increasing attention and even perhaps a little funding.
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7/7/2008, 2:10 pm
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Reythia
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Re: Gliese 581 - Habitable?
quote:
QS2 wrote:
Though in better news, space solar power is starting to draw increasing attention and even perhaps a little funding.
Amusing, that. Do you know the SIZE of the solar power setups you'd need to do the type of things most people are thinking of with space solar power?
Moreover, you've heard the classic ideas of either paving the Moon with solar recievers or setting up an orbiting band of recievers, right? Well, okay, let's pretend that somehow you did one or the other (completely ignoring the major technical difficulties of Moondust, heat-produced deformation, and formation flying). How are you going to get that energy back down to Earth???
Mostly, people talk about "beaming" it down, via some wavelength, in a laser-type form. Here's my question: let's say you build a device that can transfer all that solar energy into electrical energy and transport it via electromagnetic radiation down to a reciever on the Earth. What about that most famous biproduct of all energy transfer, HEAT?
When you transfer electricity through a wire, you heat up the wire, right? Well, if you transfered energy through the air, you'd heat up the air. And a lot of energy means a lot of heating.
I somehow fail to see how directly heating our planet's atmosphere aids in the search for "clean" energy that will DECREASE global warming!!
Plus, what about all the poor little birdies that fly in the way of your energy beam? *Zzzzzzert!* KFC, anyone?
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7/8/2008, 7:23 pm
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QS2
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Re: Gliese 581 - Habitable?
I guess you aren't up to date on the latest space solar power technologies. Transmission is indeed solved by electromagnetic radiation, but total losses from space to earth, including atmospheric losses and conversion from wire to radiation and back to wire is only about 10-15%, which is pretty impressive considering that's from over 36.000 kilometers distance. Further more radiation density at the pickup point is only at about cellular phone levels at worst and the receiver is just a very large wire mesh that can in fact for instance just be placed over a field with only something like 1-2% light loss to the plants or whatever else you might want under it.
And of course, due to the ridiculously high efficiency of each stage, heat production is really rather low. Leaving us with only one major obstacle, which is that space solar plants are still rather large if you want to start thinking in megawatts or gigawatts of power. Luckily the launch costs can be somewhat offset though by having what seems to be a roughly 3-4 times high level of solar irradiance in space, not needing complicated servo mechanisms like on earth and being able to use a much lighter structure in space overall.
Never the less, at current launching costs it is not yet as far as I know truly competitive with other power sources, except in a mobile sense, ie, sending power where ever on the planetary surface where you might need it, instead of needing to ship in generators and fuel etc. Which means the military have at the moment some passing interest in it, personally I'm hoping they can reduce launch costs a bit more though as that would make it more interesting for general civilian applications.
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7/9/2008, 3:27 pm
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Reythia
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Re: Gliese 581 - Habitable?
quote:
QS2 wrote:
And of course, due to the ridiculously high efficiency of each stage, heat production is really rather low.
I remain skeptical. You're shooting a large laser through the atmosphere. Even if only a hundredth of a percent of that energy is converted into heat during the transmission, that ends up being a LOT of heat when you consider how much energy there is to start and how long (and often) you plan to do the beaming.
As a side note, given the paperwork we have to go through to use even "eye-safe" airborne laser altimeters, I'd think the paperwork problem for such a setup would be a real pain in the rear! *grrr* Stupid foolish government regs!
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7/9/2008, 5:14 pm
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QS2
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Re: Gliese 581 - Habitable?
Well you would think it a lot of energy considering our cities, but human power consumption is extremely small compared to the total power input from the sun and there all energy we use eventually gets released as heat... All energy produced and used gets released in to the atmosphere anyway. Transmitting power from space to ground would thus effectively change nothing, as total power usage isn't going to be changed due to this.
Also they typically are thinking about a type of microwave frequency (I don't believe it is the one that gets absorbed by water though, for I would suppose obvious reasons), so eye safety need not play a role at all, plus it has to be realized that energy arrives in an extremely diffuse way, thus why they use very large but cheap receptacles. (It is also done this way to avoid solar arrays being weaponised, ie they are incapable of a concentrated beam by design)
Still, no doubt the government will probably still have you fill in a ton of paperwork for who knows what. 
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7/9/2008, 6:41 pm
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Reythia
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Re: Gliese 581 - Habitable?
We use microwave ranging on the satellites I work on, to judge the distance between the two satellites to very high accuracy. Normally the two satellites are about 200km apart. However, halfway through the mission, we had to swap the satellites, to put the one in front in the back and vice versa. When the satellites got within a certain range (it was somewhere between 50-100km), we had to SHUT DOWN the microwave ranging system, because otherwise the energy from the beam would have damaged the other satellite.
That's only from using a little, tiny ranging system powered by a little tiny solar array. A much bigger array would require a much stronger beam.
Moreover, recall that my satellites are in space (~500km altitude). There's not a lot of air there to disperse the beam. Lower in the atmosphere, however, there would be. Dispersion means power loss. Power loss means heat. Moreover, power loss means that in order to get the amount of energy you need to the surface, you have to start with more energy.
quote:
Well you would think it a lot of energy considering our cities, but human power consumption is extremely small compared to the total power input from the sun and there all energy we use eventually gets released as heat... All energy produced and used gets released in to the atmosphere anyway.
Well, remember, the main logic behind collecting all that light in space rather than on the ground is to avoid the loss of energy caused by reflection of the atmosphere. Much of that energy that the laser sends down would NOT have made it through the atmosphere to heat up the planet if we hadn't built the solar receiver.
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7/10/2008, 3:57 pm
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QS2
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Re: Gliese 581 - Habitable?
While your points are all valid, most of the factors you name are in practice of far to negligible in scale. But I'll try to more clearly address them for you.
Space Solar Power power losses as said before is rather minimal and the ground based systems suffer from similar losses and of a comparable level (transmission losses via wire resistance instead of microwave in this case), which means on average that the 3-4 times more solar power in space is what matters. The dispersion doesn't matter, because a concentrated beam was never an intended goal anyway, instead they just build receiver arrays measuring several square kilometers, so even with dispersion near the entire beam gets caught and building an array of this size seems to be fairly cheap, so it doesn't impact cost much.
As for the heating of the atmosphere, it isn't really relevant either, the amount of power is fractionally small compared to solar luminance and it doesn't change the actual amount of power released in the atmosphere really. because our current power production methods all release energy that would otherwise not have been released on the surface. So in effect the amount of energy released in the atmosphere won't change, regardless of the power source we are using. The only one perhaps that would change that is solar power on the ground, but even that increases surface albedo. Overall thus planetary heating due to power usage or loss isn't an issue of any real importance.
The microwave interference from a Space Solar Plant as it crosses the 36000 kilometers from geostationary though, would I suppose be a navigational hazard in space and the receptor area. I hadn't thought of that, but it would probably be something you definitely wouldn't want to stray in to, or perhaps you'll have have to make future satellites resistant to microwave radiation?
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7/10/2008, 4:56 pm
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Reythia
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Re: Gliese 581 - Habitable?
quote:
QS2 wrote:
The microwave interference from a Space Solar Plant as it crosses the 36000 kilometers from geostationary though, would I suppose be a navigational hazard in space and the receptor area. I hadn't thought of that, but it would probably be something you definitely wouldn't want to stray in to, or perhaps you'll have have to make future satellites resistant to microwave radiation?
We already try to make our spacecraft resistant to most radiations. Microwave isn't overly damaging on a short-term or occasional basis, but a few years in orbit under such a beam would cause major problems.
Moreover, I've often wondered: what about the plant life under that platform? I mean, by making it geostationary, you're forcing it to stay directly above the same location. Admittedly, a square (for simplicity's sake) that's 6000km on a side isn't HUGE in space... but it's still pretty dang big! I realize that light will defract around it, so that the area that's permanently underneath won't be totally dark, but still, you're going to have a fairly large area of very shadowy weather -- permanently. I've often wondered how wise that would really be. I know my biologist sisters would have some major qualms about it.
Moreover, is geostationary orbits really the best choice? By definition, they're about 36000km from the surface and ONLY OVER THE EQUATOR. Tell me, how is this going to help non-equatorial countries?
Basically, I think a lot more thinking needs to be put into this idea before I'd jump behind it. Just call me skeptical.
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7/11/2008, 8:21 pm
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QS2
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Re: Gliese 581 - Habitable?
The reason for the altitude, is part based on more space being free their, in part so you don't have to constantly cycle your beam to different reception areas, as well as that a lot of the planet is visible from so high. Also because there rarely is any night in that orbit at that altitude, taking in to account the earths tilt compared to the sun, except for brief periods in autumn and spring. And because the sun defracts around the platforms at such altitude sufficiently so that light loss even for very large installations tends to be far below 1% (I thought), for those few rare times it does occlude anything during autumn and spring.
As for a lot being put in to the idea, well let us say this isn't a spur of the moment idea, since the 70s when a very large study was done by NASA every few years people review the situation and update plans to see how realistic it is to try now (Including I think NASAs late update in the late 90s). With rising oil prices, maybe peak oil nearby and global warming, further interest is obviously mounting in this concept.
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7/11/2008, 9:39 pm
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Reythia
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Re: Gliese 581 - Habitable?
I know. One of the guys I eat lunch with is a retired NASA engineer. He and a former prof of mine both worked on the theory in the 70s and 80s. For the record, they've both grown skeptical of the ideas since then, mostly because they think other emerging technologies would be more effective. Much of my skepticism comes from them, I admit.
quote:
The reason for the altitude, is part based on more space being free {there}
HUH? Free space in geostationary? Not on your life! That's the most crowded orbit there is, QS. I've a friend (a former master's student with me) who gets paid to figure out where the safest places in geosynchronous (including geostationary)orbits are to insert new satellites. It's become standard practice to plan a "deorbit" stage of any satellite mission, since the space up there is getting rather crowded. Frankly, it's not really a big issue for most orbits, but it IS a huge issue for geostationary ones. The reason: because there's only the ONE geostationary orbit, versus infinite others (ie: different altitudes and different inclinations). Only so many satellites comfortably fit in one orbital slot -- and geostationary is getting pretty full. I'd suspect there would be a LOT of complaining from scientists, various militaries, and commercial companies if we decided to start placing large installations in geostationary orbits.
Are you sure you're not thinking of geosynchronous orbits? Geostationary orbits have to be above the equator (zero inclination) and are always above the same point on the Earth. Geosynchronous orbits can be at any inclination, but still go around the Earth precisely once a day, leading to them passing over the same point on the surface at the same time every day. There are a lot more geosync spots than there are geostationary ones.
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7/13/2008, 7:17 pm
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QS2
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Re: Gliese 581 - Habitable?
No, I certainly didn't mean geostationary, considering in another point of my discussion I was noting the inclination level of geostationary, however I suppose some geosynchronous orbits might be as good or perhaps better then geostationary on the Earth shadow issues.
I suppose in the future we will also one day have to start to make larger installations for geostationary, where you can add several functions into one orbiting craft. I'm not sure how else you'll manage to keep meeting demand for that one particular orbit.
As an aside, I don't suppose you could tell us about some of those other emerging technologies which they thought stood a better chance, could you? (Perhaps even in a separate thread?) 
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7/14/2008, 7:28 am
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Reythia
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Re: Gliese 581 - Habitable?
Well, honestly, I don't see why geostationary is a requirement for the sort of thing you're talking about anyhow. You'd need a repeating orbit -- probably a short-repeat, like something that crosses over the same groundtrack every few days. There are LOTS (infinite, technically) of those orbits, including all the geosynchronous ones (which repeat their groundtracks precisely once per day). The reason I don't think a geostationary orbit is required is that if you're going to spend all the money and go through all the technical (and political) troubles of putting a satellite up there, you're going to want two things:
1.) Multiple groundstations capable of tracking the satellite, sending and recieving instructions, AND recieving the "product" -- solar energy in some sort of beam form, in this case. You've talked about having one groundstation, at least for the reception of power. But what if that groundstation has some sort of temporary failure? Trust me, it happens all the time. Anytime you launch a satellite mission, you really NEED redundancy on the ground. And if you're going to have (at least) two reciever stations, it behooves you to put them far enough apart that a single local event (ie: a storm, a power outage) couldn't knock them both out at once.
2.) A way to store your power onboard the satellite. This idea of a constant stream of energy is all well and good, except that it doesn't work in principle. Ask the guys in charge of the lunar laser ranging astronomical stations, if you don't believe me. Take a trip out to McDonald Observatory or whereever else they have such a set-up (it's a neat trip). Even with the limited energy beams they use, they need to pulse the beam, so as to not overheat their equipment. You'd need to do the same in space, if you wanted to beam energy back down. The thing is, pulsing the energy means that between pulses, you need a place to store the energy. Batteries, basically. Moreover, you'd need to have batteries up there to power the spacecraft itself -- after all, if something happened to disturb the flow of power, you wouldn't want to lose the spacecraft permanently because of it! But most importantly, what about if one of your groundstations goes offline temporarily? What do you do with all that energy? Waste it by beaming it down anyhow? (And potentially causing more trouble for your already-misfunctioning groundstation?) Or waste propellant on the spacecraft to aim the beam safely elsewhere (probably into deep space)? Or store it, until you reach the next groundstation? That's what *I* would plan to do. That involves more (and better) batteries than we use right now.
Which brings me back to my original point. If you are already planning to have a large set of storage batteries on your satellite, then why not plan to USE them? Instead of flying in geostationary orbit and beaming down to one station, why not pick a short-repeat orbit and have several stations? If you can store up your data for a few hours before discharging (and assuming you can discharge quickly enough so the groundstation doesn't get too low on the horizon), then you don't NEED to be in a crowded, expensive geostationary orbit. That seems a wiser proposal to me.
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7/14/2008, 7:10 pm
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QS2
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Re: Gliese 581 - Habitable?
Just as a technical detail, they would want to use a solid state transmitter, which can change angles on the fly as you require it, as such no propellant is needed to change targets, as such you can also easily beam in to deep space if you wanted to, though I wouldn't advise it, cause who knows what you'd hit. Still, I don't expect they'll acquire very large storage ability, because that simply weighs to much. More likely they'll prefer to use a considerable amount of redundant transmitters, which would be lighter I expect, sadly if there is no receiver you'd probably just have throw the energy away, because it isn't economical to store it. Not at gigawatt power levels at least.
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7/14/2008, 8:18 pm
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