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#76 2007-02-12 00:43:42

Martin_Tristar
Member
From: Earth, Region : Australia
Registered: 2004-12-07
Posts: 305

Re: Lunar economics etc

I see you , can't see change GCNRevenger (and non-believers) , every business today needs a website for marketing their business to potential and existing clients.  That's what the Internet has changed business life and in society look at the blogs, podcasts, rss feeds and more that provide real-time information to people across the world. The wired world has become as essential as the car or electricity was 80-100 years ago .

Space is the next frontier for human evolution , and what we need is a reusable sustainable platform for launching into space without effecting the environment and atomsphere to much. Its time to stop the waste within the current launch platforms. We need to construct, assembly, supply and resupply of the vehicles without a large cost being incurred like current platforms. Our designs must incorporate recycling aspects to use the spent components into other vehicles in space or planetary bodies. ( multiple uses for multiple missions in orbit or on-planet reducing the per unit cost per vehicle commissioned) This requires the development of vehicle engines, systems and maintenance programs that can be updated and / or altered depending on the use required for the component.

Variations in design should add the overall flexibility and provide benefits over the lifecycle of the vehicle, with new advances in electronics , power systems, communications and information systems,  each component must be backwards compatible to reduce cost and wastage in space or surface activities.

When you look at the larger picture of how to build into space for permanent settlements for humanity and not tourist / explorer missions you work on the issues that impede the expansion of space ,not leave them in the too hard basket like you do, and hope for someone 50 - 200 years down the track to fix them, fix them now with our primative technology and then development better and better technologies when we are out there.

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#77 2007-02-12 22:58:23

Tom Kalbfus
Banned
Registered: 2006-08-16
Posts: 4,401

Re: Lunar economics etc

The problem with the Moon's sunlight isn't strength, its that it doesn't shine half the month over much of its surface. Only a hand full of certain mountain tops are continuously lit, and even then only from low in the horizon and only at the summit. If the minerals you are digging for aren't present near these mountains, then getting electricity to them might not be practical. On Mars, you can get power any place you like year-round, albeit less efficiently. Having to basically abandon or close down a Lunar base every week or two for want of power is a serious issue.

The Sunlight is just as intense as if it were received on the equator. The percentage of Lunar real estate is tiny when compared to the entire Lunar Surface, but the moon is huge, in real terms compared to us, alot of sunlight can be received continuously at the Lunar North and South Pole. I don't see any reason for the immediate future, why we'd want to locate a base anywhere else. On the Moon's poles you can get sunlight continuously, just like in space. The Moon also provides a nice well shielded area for astronauts to live, bury the habitat deep enough and it will be well protected from both comic rays and Solar flares. Lunar rock isn't the best shielding material, but if you have enough of it, it will work.

I reject the idea that PGM prospecting and some of the mining can be done efficiently by remote, especially for figuring out which rocks to mine. This is better done by humans, with stereoscopic vision, better dexterity, and having the "analysis" as you go instead of waiting on Earth. Manned "hoppers" powered by domestic LOX and imported Hydrogen or pressurized rovers will visit promising sites, take/test samples, and so on. Much of the actual digging will probably have to be overseen or partially controlled on site too.

PGMs are a sufficient, and probably only, real justification for any sort of Lunar industrial activity. If fusion power ever happens, He3 would only be an extremely expensive "premium" fuel for special applications, and there is enough of it here on Earth for that sort of thing.

Like traveling to the rest of the Solar System using fusion rockets, Mars too? A helium-3 fusion rocket may get you to Saturn, where there is even more helium-3. A spaceship can dip into the fringes of Saturn's atmosphere and collect more helium-3 without completely slowing down from orbital velocity. With enough passes, sizable amounts of helium-3 could eventually be collected from there. Probably a fusion rocket could maintain orbital velocity so the scooper ship doesn't completely deorbit, and the fusion rocket doesn't have to accelerate that much to do so. Only a small portion of the scooper ship's orbit is in the fringes of the atmosphere, the rocket can accelerate for most of its orbit around Saturn and then decelerate, when its in the fringes of the atmosphere again. With each pass, the scooper ship can collect more helium-3. Collect enough, and it can bring its load back to Earth, and the way to start this process is to obtain helium-3 on the moon, and also have a helium-3 fusion rocket.

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#78 2007-02-12 23:27:12

Austin Stanley
Member
From: Texarkana, TX
Registered: 2002-03-18
Posts: 519
Website

Re: Lunar economics etc

Like traveling to the rest of the Solar System using fusion rockets, Mars too? A helium-3 fusion rocket may get you to Saturn, where there is even more helium-3. A spaceship can dip into the fringes of Saturn's atmosphere and collect more helium-3 without completely slowing down from orbital velocity. With enough passes, sizable amounts of helium-3 could eventually be collected from there. Probably a fusion rocket could maintain orbital velocity so the scooper ship doesn't completely deorbit, and the fusion rocket doesn't have to accelerate that much to do so. Only a small portion of the scooper ship's orbit is in the fringes of the atmosphere, the rocket can accelerate for most of its orbit around Saturn and then decelerate, when its in the fringes of the atmosphere again. With each pass, the scooper ship can collect more helium-3. Collect enough, and it can bring its load back to Earth, and the way to start this process is to obtain helium-3 on the moon, and also have a helium-3 fusion rocket.

The problem is that He3 isn't really that much better than conventional fusion fuels.  We've disscussed this a few times before.  Sure it has the margianly better specific energy than other fusion fuels, and produces no (or at least very little) neutron radiation, but this isn't enough to off-set it's mind blowing cost.  D-D fusion is only margianly more difficult to achive than D-He3, produces only moderate Neutron radiation, and has nearly as good specific energy.  But most importantly while He3 will likely cost upwards of tens thousands of dollars per-gram, deutrium can litteraly be bought right now, over the internet, for less than $1/L WITH the tank it came in included.

Thats one of the key advantages of fusion energy, that the fuel is insanely cheap per unit of energy, even if you have to use signifigantly more expensive Tritium (produced by Lithium decay mainly).  D-D fusion is truely absurdly cheap in terms of fuel costs.  He3 fusion throws these advantages away, for only dubious benifits.

Furthermore, I doubt Lunar He3 mining would be practical even if He3 was a desirable fuel.  Instead of trying to recover in in the ppb range from the moon, we would be better of iradiating Lithium and collecting the He3 that would be produced as a decay product (as well as the Tritium, which is a nice bonus).  This is bound to be more economical than trying to mine the stuff on the moon.


He who refuses to do arithmetic is doomed to talk nonsense.

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#79 2007-02-13 11:54:24

Tom Kalbfus
Banned
Registered: 2006-08-16
Posts: 4,401

Re: Lunar economics etc

Like traveling to the rest of the Solar System using fusion rockets, Mars too? A helium-3 fusion rocket may get you to Saturn, where there is even more helium-3. A spaceship can dip into the fringes of Saturn's atmosphere and collect more helium-3 without completely slowing down from orbital velocity. With enough passes, sizable amounts of helium-3 could eventually be collected from there. Probably a fusion rocket could maintain orbital velocity so the scooper ship doesn't completely deorbit, and the fusion rocket doesn't have to accelerate that much to do so. Only a small portion of the scooper ship's orbit is in the fringes of the atmosphere, the rocket can accelerate for most of its orbit around Saturn and then decelerate, when its in the fringes of the atmosphere again. With each pass, the scooper ship can collect more helium-3. Collect enough, and it can bring its load back to Earth, and the way to start this process is to obtain helium-3 on the moon, and also have a helium-3 fusion rocket.

The problem is that He3 isn't really that much better than conventional fusion fuels.  We've disscussed this a few times before.  Sure it has the margianly better specific energy than other fusion fuels, and produces no (or at least very little) neutron radiation, but this isn't enough to off-set it's mind blowing cost.  D-D fusion is only margianly more difficult to achive than D-He3, produces only moderate Neutron radiation, and has nearly as good specific energy.  But most importantly while He3 will likely cost upwards of tens thousands of dollars per-gram, deutrium can litteraly be bought right now, over the internet, for less than $1/L WITH the tank it came in included.

Thats one of the key advantages of fusion energy, that the fuel is insanely cheap per unit of energy, even if you have to use signifigantly more expensive Tritium (produced by Lithium decay mainly).  D-D fusion is truely absurdly cheap in terms of fuel costs.  He3 fusion throws these advantages away, for only dubious benifits.

Furthermore, I doubt Lunar He3 mining would be practical even if He3 was a desirable fuel.  Instead of trying to recover in in the ppb range from the moon, we would be better of iradiating Lithium and collecting the He3 that would be produced as a decay product (as well as the Tritium, which is a nice bonus).  This is bound to be more economical than trying to mine the stuff on the moon.

Have you considered the reactor cost? Reactors become irradiated by all the free neutrons, and that makes the walls of the reactor brittle. If the reactor doesn't last as long, thats going to increase the cost of using Deuterium/Trintium fuel. Also the neutron reaction products can't be captured and directed into a rocket exhaust as they can't be channeled by magnetic fields, this reduces the efficiency of a Deuterium/Trintium rocket as you need more fuel mass, and need to fuse more of it to heat the same amount of reaction mass. I think Helium-3 reactors would be longer lived, and you can spread its fixed cost over a greater abount of fuel fused, so this inpart compensates for Helium-3s higher fuel cost as you have to replace the reactor less often.

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#80 2007-02-13 16:48:11

Austin Stanley
Member
From: Texarkana, TX
Registered: 2002-03-18
Posts: 519
Website

Re: Lunar economics etc

Have you considered the reactor cost? Reactors become irradiated by all the free neutrons, and that makes the walls of the reactor brittle. If the reactor doesn't last as long, thats going to increase the cost of using Deuterium/Trintium fuel. Also the neutron reaction products can't be captured and directed into a rocket exhaust as they can't be channeled by magnetic fields, this reduces the efficiency of a Deuterium/Trintium rocket as you need more fuel mass, and need to fuse more of it to heat the same amount of reaction mass. I think Helium-3 reactors would be longer lived, and you can spread its fixed cost over a greater abount of fuel fused, so this inpart compensates for Helium-3s higher fuel cost as you have to replace the reactor less often.

With proper selection of reactor materials neutron radiation is not that signifigant a problem.  Neutron activation isn't going to cause a fusion reactor to crumble over night.  Indeed, I would be much more worried about potential material fatigue from exposure to Such high temperature plasma then neutron flux.  The biggest problem is that exposed materials have to be disposed of as low-level nuclear waste, but in the end this not that great a cost, at least not compared to He3 costs.

But if we are going to consider D-He3 fusion, we should not compare it simply with D-T fusion, but with D-D fusion which is achiveable at about the same temperatures.  D-D fusion produces considerably less neutron radiation than D-T and has a better power/weight ratio (almost as good as that as D-He3) and uses no expensive fusion fuels (indeed, you could potentialy collect He3 from the reactor if you wished).

Furthermore, D-He3 is not completely aneutronic either.  Some D-D reactions will occur, producing some Neutron radiation.  He3-He3 fusion would be completly aneutronic but you're fuel requirments would double, and you lose the specific power advantage.  It also requires an even higher temperature.  If you were to consider it, you might as well consider something like p-B11 which is also completely aneutronic.  While it's ignintion temperature and containment requirments are higher then D-D or D-He3, the gap is not as big as that bettwen D-T and D-D fusion.


He who refuses to do arithmetic is doomed to talk nonsense.

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#81 2007-02-13 17:08:16

Austin Stanley
Member
From: Texarkana, TX
Registered: 2002-03-18
Posts: 519
Website

Re: Lunar economics etc

Sorry for the double post, but I forgt to reply to the space specific concurns about He3.

In a space application, the utility of He3 becomes even less I think.  It remains as expensive as ever, but in pretty much any fusion rocket designed for interplantary travel the fusion reaction is going to serve mainly as a heat source.  The bulk of the propulsion will be done via hydrogen (or some other medium, most likely hydrogen) that is used to dilute it.  Otherwise you get really fantastic specific impulse but little to no thrust.  Thus the specific impulse of the rocket is more dependant upon what you use to dilute the reaction with then what the reaction actually uses.

Also, the dilutant serves as a pretty good neutron absorption source.

And even more also, since fusion engines performance is going to be fairly dependant on the engines weight, a  more power dense fusion reaction (ie one with higher ignition and containment levels) may actually be a better choice such as p-B11, as it will pack more energy per gram of engine weight.  And in a fusion engine your engine is likely to outweigh your fuel source (D or He3) anyways, so this is fairly signifigant.

::Drat, didn't want to triple post, and forgot another important point::

Also imporant is that in a diluted fusion rocket, the energy from the Neutron radiatoin can be harnesed to a good degree, as it will interact with and heat up the fusion fuel.  Some will probably still escape, but a good fraction of it can be captured in this way.


He who refuses to do arithmetic is doomed to talk nonsense.

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#82 2007-02-13 19:48:14

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,934

Re: Lunar economics etc

Here is the take by the AIAA/SCTC and their Position Statement, at least there is a set of goals...

The AIAA/SCTC paper emphasizes human settlement of the Moon; development of lunar observatories, energy and resources uses; and sustained, active encouragement of private and international enterprise. It recommends the establishment of the scientific and industrial capabilities of a permanent lunar settlement and development of the commercial revenue sources on the Moon.

Recommendations in the paper cover the early period (present 2015), mid-period (2015-2025) and far period (2025-2050). The SCTC also calls for the United States to work with international partners to pursue free-market rules to the development of space; international conventions on property and mineral rights; and land management conventions to include provisions for homesteading.

ROBUST IMPLEMENTATION OF LUNAR SETTLEMENTS WITH COMMERCIAL AND INTERNATIONAL ENTERPRISE [MOON BASE 2015]

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#83 2007-02-13 20:50:30

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Lunar economics etc

No, "lots of solar power" on the Moon isn't as easy as it sounds. If you put the arrays on polar mountain tops, they will have to be sun-tracking, increasing their cost & complexity and decreasing their efficiency. The problem as far as longitude, that is the sun sitting very low on the horizon, is a simple one: if you put arrays on the summit, the sunward-side ones will simply block and shadow the rest. The "effective" area of the mountain top is vastly reduced by the angle at which the sun lies.

I doubt that Aluminum/Oxygen rockets are terribly practical, you can't make a "hybrid style" engine since the Aluminum burned on the surface is tightly bound to the rest of the metal, and the oxide "ash" does not come off, preventing combustion of any more Aluminum under it. Aluminum dust and LOX slurries probably aren't terribly stable since the metal would simply settle out and clog the engine up, besides the fact that it would be very dangerous to handle. Pushing aluminum powder into a combustion chamber under pressure is not going to happen either. The high mass of the exhaust product (Al2O3) will also severely limit efficiency.
_______________________________________________
Austin Stanley is totally correct about the prospects of He3 as a fusion fuel, its always been only marginally better than cheap old Deuterium (which, BTW, is supposed to be plentiful on Mars). If you can't make a reactor that will burn D+D and still make more power than it consumes, any combination of He3 will not make much difference.

In either event, Lunar He3 mining is mostly a red-herring to stoke up the idea of massive Lunar industry for a "futuristic" material that will "solve all our problems" (IE energy) here on Earth. Extracting it in useful quantities (tonnes yearly?) is not going to happen. Consider that for 1MT of He3 from Lunar dust at - say - 100ppb you need to mine ten million tonnes of ore, assuming 100% extraction even after you dig/disrupt/unbury the He3.

A tonne too much? Remember, fusion reactors are always probably going to have a high fuel consumption, since so much of their output is consumed in just maintaining the reaction. And, while the stuff has good energy density per gram, its also really light, so you are going to need a lot of it.

One contention though is the "dilution" of the superhot fusion plasma with Hydrogen limits its efficiency, which is only partly true. What limits "thermal" engines, rockets which derive all the propellant velocity from expansion of a gas, is how hot and how light the gas is. Hydrogen is the best gas available as far as how heavy it is of any possible fuel, so the question is one of temperature.

What limits temperature when you are supply heat from another source (eg reactor) is basically how hot you can make the gas before your engine melts. Engines like VASIMR are arranged such that the superhot gas doesn't touch much of anything, which greatly reduces the thermal "strain" on the engine, and enables fairly high efficiency (10,000sec+ Isp).

The catch, of course, is the details: for a power plant of a given output, the efficiency of an engine and the thrust are inversely related. So if you don't have a big high-output power source, even a highly efficient engine won't have enough thrust to get you anywhere. The problem with that is, if you have a huge reactor, isn't that going to impact your payload and/or travel time severely?

This is where the power-per-weight of the reactor is a major issue, and even when we do have fusion power, the reaction may be highly efficient, but the reactor will be an awful lot of dead weight. Even later, advanced fission power plants may win out for a long time indeed.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#84 2007-02-13 20:58:14

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Lunar economics etc

Oh, and on the issue of neutron radiation damage: I think this problem is largely overstated, it takes a huge dose to cause much damage, nuclear fission reactor parts resist massive neutron radiation doses already, and they have to hold much more pressure than a fusion reactor, likely at a higher temperature too.

The guts of a fusion reactor just can't be allowed to get terribly hot, or else the confinement magnets and fuel injectors/removers would melt.
_________________________________________________
Oh! Almost forgot, if we put a big solar power plant on top of a really tall mountain, how do we get power to PGM sites that are not close to said mountain?


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#85 2007-02-14 22:22:59

RedStreak
Member
From: Illinois
Registered: 2006-05-12
Posts: 541

Re: Lunar economics etc

Oh! Almost forgot, if we put a big solar power plant on top of a really tall mountain, how do we get power to PGM sites that are not close to said mountain?

Microwave transmission.  It has been tested in the past via sets of Japanese satellites.  Aforementioned mountain set on the high ground out to have great line-of-site transmission.

Silly GCN...tricks are for kids.  tongue

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#86 2007-02-15 14:58:06

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Lunar economics etc

Meh, the Moon's small size means its radius of curvature is tighter, hence shorter maximum line-of-sight condition. Bouncing a multimegawatt beam off a satellite in an unstable Lunar orbit ain't going to happen, its a totally different animal than watt/kilowatt scale power between two closely spaced formation flying satellites. It wouldn't be continuous either.

L1 or any of the LaGrange points are almost half way back to Earth too, and you just aren't going to focus microwaves over that sort of distance without massive losses. The LaGrange points aren't 100% stable either.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#87 2007-02-15 15:04:43

cIclops
Member
Registered: 2005-06-16
Posts: 3,230

Re: Lunar economics etc

L1 or any of the LaGrange points are almost half way back to Earth too, and you just aren't going to focus microwaves over that sort of distance without massive losses. The LaGrange points aren't 100% stable either.

L1 in the Earth Moon system is 61,500 kms from the centre of the moon, still a long way but far less than halfway.


Let's go to Mars and far beyond -  triple NASA's budget !   #space channel !!    - videos !!!

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#88 2007-02-16 04:54:06

Grypd
Member
From: Scotland, Europe
Registered: 2004-06-07
Posts: 1,863

Re: Lunar economics etc

He3 does have some advantages over the use of D-D fusion reactors. For a start there is a lot less radiation and this means there is less effect on the shielding and degradation of the fusion bottles. We are trying to get away from having tonnes of radioacive material needing to be buried in secure sites for thousands of years.

Another advantage is that the He3 reaction can be contained a lot easier by magnetic fields. Also the reaction is a lot more efficient for power generation since it does not reguire the heating of a liguid and the powering of turbines. The HE 3 reaction a direct electricity supply is garnered from the reaction.

This means that the He3 plants will be a lot smaller than needed for normal D-D or Nuclear plants and that is a definite advantage. Especially if it comes to using aboard spacecraft and even warships here on Earth.


Chan eil mi aig a bheil ùidh ann an gleidheadh an status quo; Tha mi airson cur às e.

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#89 2007-02-16 05:08:39

Grypd
Member
From: Scotland, Europe
Registered: 2004-06-07
Posts: 1,863

Re: Lunar economics etc

Microwaves can be sent along towers. So there is not as much need to send them up to Lunar orbit and back. There is also the possibility that we use good old fashioned laid cables. At one metre deep the regolith of the Moon is a constant tempature of -20 and we have cables that act very efficiently at that tempature. Much more efficient than we have here on the Earth with its constant tempature changes.

Solar tracking is important for the first solar farms planted on the Moon as we will need the energy but since these are likely to be directly deployed from the Earth they can be sent modules designed for the purpose. But with the first base on the Moon going to be nearby there is not a problem. As we spend more time and are able to develop the Moon a bit using insitu materials then we can start making our own solar cells automatically. As we create the less efficient but tolerant solar cells from just regolith then we put them on A frames so the sun hits them from whatever angle it is at. As we spread the farms further and further around the Moon there will reach a point guite guickly where the sun is always shining on one site or another. Then we have constant electricity.

This can be easily done without the use of people since robots operated from the Earth can do the job and the assembling of simple A frames easily. We have already developed machines that using simulated lunar regolith make sheets of simple solar cells. Digging and laying cable is another thing that we can easily have robots do.


Chan eil mi aig a bheil ùidh ann an gleidheadh an status quo; Tha mi airson cur às e.

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#90 2007-02-16 07:02:14

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Lunar economics etc

He3 does have some advantages over the use of D-D fusion reactors. For a start there is a lot less radiation and this means there is less effect on the shielding and degradation of the fusion bottles. We are trying to get away from having tonnes of radioacive material needing to be buried in secure sites for thousands of years.

Another advantage is that the He3 reaction can be contained a lot easier by magnetic fields. Also the reaction is a lot more efficient for power generation since it does not reguire the heating of a liguid and the powering of turbines. The HE 3 reaction a direct electricity supply is garnered from the reaction.

This means that the He3 plants will be a lot smaller than needed for normal D-D or Nuclear plants and that is a definite advantage. Especially if it comes to using aboard spacecraft and even warships here on Earth.

No!

This is what me and Stanley are explicitly telling you is not true. He3 does not enable you to use significantly less strong magnetic compression fields/bottles/etc. Using He3 to boost Deuterium fusion is also not completely neutron-free either, so the reactor core will become radioactive still. And, frankly, there is no possible way you could possibly collect enough of it anywhere in the inner solar system to make pure-He3 fusion practical. Parts-per-billion in the Lunar soil is all we need to know that its never going to happen.

The idea that the neutron flux from a D-D reaction will make the core "crumble" or something is nonsense jibberish, regular fission reactors experience similarly powerful neutron flux, but hold up against much greater forces and temperatures than the pressure vessel of a fusion reactor will, and thats cheap old steel.

And while the core will become radioactive after long periods of time, it will be pretty weak radiation. Neutron radiation just isn't going to make the core's parts really severely hazardous, neutron radiation doesn't do that. In fact, much of the radiation is short lived, and dissipates in days or at most a few years. It is absolutely not a problem unless you are a completely paranoid science-rejectionista Greenpeace lemmings.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#91 2007-02-16 17:06:49

Grypd
Member
From: Scotland, Europe
Registered: 2004-06-07
Posts: 1,863

Re: Lunar economics etc

But He3 reactions can be easily held by magnetic fields unlike a D-D reaction. And you will note I did not state it was radiation free as D-D reactions will occur as well but it is the He3 Deutrium reactions that interest us.

I have never thought that the Moon could provide what we need but we do have the Gas giants where He3 is a lot more common. To the point where if we can go after it we will get enough to keep us running for tens of thousands of years.

D-D reactions are hard to keep stable, Magnetic fields struggle to contain them and they tend to damage the reaction vessels. He3 reactions are a lot easier to control and as such wear on the vessels will reduce.

If Fusion is ever to work it must have plants that operate day in and day out for weeks providing energy and as such the containment vessels as well as the means to get the heat transfered will be irradiated in a D-D fusion reactor. An He3 reduces the need for Turbines and all that extra eguipment to work. This should make an He3 reactor a lot simpler and simple works.


Chan eil mi aig a bheil ùidh ann an gleidheadh an status quo; Tha mi airson cur às e.

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#92 2007-02-16 23:37:49

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Lunar economics etc

You are simply wrong grypd, D+He3 fusion is in fact much harder to fuse than regular D+T fusion and is little easier than D+D fusion as far as temperature. Where do you get this idea that D+D fusion is "hard to contain" or "hard to keep stable?" in fact because there are fewer electrons per fuel atom similar nucleus-densities are possible at a third less pressure.

While D+D/D+T do throw off a lot of neutrons, this is not necessarily a bad thing: D+He3 suffers a problem that these don't, which is D+He3 radiates a large proportion of its total energy release (about 5/6ths of it) as X-ray and Gamma rays, which are neither reabsorbed by the plasma nor really useful for power. This would also require heavy shielding for use in a space application to protect the crew.

Neutron radiation on the other hand is easy to stop with propellant on a space ship (Hydrogen) or light shielding (inches of plastic or water) plus has a handy trick: the neutrons can be captured by water from the primary coolant loop to heat it up. Handy, no? With space ships, the neutron radiation could pre-heat the Hydrogen propellant too.

And that water becomes radioactive? No problem, put it in a tank and sit on it for a few years, and the Tritium in it decays and goes away. Then its just regular water again, maybe a little heavy in harmless Deuterium. This might actually be the preferred way to get the energy out of a fusion reactor instead of betting on some Star Trek superhigh temperature MHD generator.

And you say that neutron-producing fusion will wreck the reactor? How do you know that? Who told you? How do they know? It takes a really terrific dose of neutron radiation to damage solids much, neutrons tend to fly right through most elements except Hydrogen and a few others. Simply don't build your reactor out of them. Modern-day fission reactors absorb pretty big doses of neutrons too, and have to contain 1000F water under high pressure (which requires far more force than a fusion reactor) for about a century or so without even the barest hint of a chance of failure. And thats with plain old steel alloys. Earth reactors, irrespective of their space counterparts, have no mass restrictions either.

As far as spacecraft, I think you are not getting the whole idea very well, that the efficiency of the fusion fuel is not very important for any type of propulsion except interstellar: no type of fusion reactor can probably fuse enough fuel such that the "leftovers" will provide useful thrust, you'd have unholy-high specific impulse, but no push. This means, as Austin Stanley pointed out, that you will have to "dilute" the fusion plasma. By mixing it with some "dead weight" matter to add some bulk, you do get a great deal more thrust, but your efficiency suffers.

When you do that, the actual fusion fuel becomes a small part of the total propulsion consumables mass (fusion fuel + diluent), so even if He3 were far more efficient it wouldn't decrease this total much. What does make a big difference is how heavy the reactor+shielding is and with D+T fusion being considerably easier (and hence lighter reactor), plus handy neutron radiation instead of gamma/x-ray (and can preheat hydrogen), then He3 doesn't make as much sense.

And finally, getting the stuff: for either space propulsion or large-scale power generation, all estimates point to tens to hundreds of tonnes required for D+He3 fusion. Producing it on Earth would require a whole industry to make He3 that would possibly consume more power than it produced (and is a smaller but significant problem for D+T too vs D+D). Getting it in tonne quantities from gas giants is a pipe dream, that its not super-plentiful by industrial standards and getting it will consume much of the energy its worth.

To end on the topic of the thread, the He3 idea is killed by the simple math, that there really isn't much of it there in the soil. People who say that there is and its useful and extractable are simply liars (inc. China, Russia) or ignorant. Its that simple, and its this simple: He3 on the Moon exists approximately one part in a hundred million. So if the Earth needs, say, 100MT every year you will simply have to dig up an unrealistic mass of Moon dust...

...ten billion tonnes of it...

And thats assuming you can capture every last gram. Even Earthly production via Tritium decay would beat Lunar mining hands down, plus leaves not a single gram for space propulsion.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#93 2007-02-17 01:18:31

Austin Stanley
Member
From: Texarkana, TX
Registered: 2002-03-18
Posts: 519
Website

Re: Lunar economics etc

But He3 reactions can be easily held by magnetic fields unlike a D-D reaction. And you will note I did not state it was radiation free as D-D reactions will occur as well but it is the He3 Deutrium reactions that interest us.


D-D reactions are hard to keep stable, Magnetic fields struggle to contain them and they tend to damage the reaction vessels. He3 reactions are a lot easier to control and as such wear on the vessels will reduce.

I'm not sure what you mean here.  D-D fusion about twice as hard as He3-D, but both are about an order of magnitude more dificult than simple D-T.  This is determined by their Lawson Critera.  Which is the product of a reactions optimal plasma density, temperature, and rate at which energy is lost (or confinement time).  He3 is not intrinsicly easier to contain then anyother sort of fusion fuel.  It has a better Lawson Critera primarily because it has no (or at least very few) neutron to lose heat with.  And so it's optimal conditions are a bit better than D-D fusion (and signifigantly better than p-B11) but again, considerably worse than D-T.  If "ease of containment" is the deciding issue, then D-T wins hands down.

If Fusion is ever to work it must have plants that operate day in and day out for weeks providing energy and as such the containment vessels as well as the means to get the heat transfered will be irradiated in a D-D fusion reactor. An He3 reduces the need for Turbines and all that extra eguipment to work. This should make an He3 reactor a lot simpler and simple works.

Any reactor is going to have to be shut down from time to time for maintance, this is just simply the way life works.  That is why nuclear fission reactors are always built in twos or threes (or more).  The same will be true for fusion reactors.  Heck, it's true for pratical any large scale power-plant.

I am far from convinced that the irradiation is going to be a big enough factor to offset the many order of magnitude increased cost of He3 fuel.  Fuel for D-D (and to a lesser extent fission and D-T) is so low as to barely even enter into the costs.  But that is because even Uranium is less than $100/kg.  We would be lucky to get He3 for 1,000 as much.  So at $100,000/kg and 10MW/kg, that's $10/kW for fuel alone.   Coal produces ~10kW/kg and cost $50/MT so ~$200/kW.  Plug in whatever you assume for He3 costs for your own comparision, but I can't imagine it being competative.


He who refuses to do arithmetic is doomed to talk nonsense.

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#94 2007-02-17 07:26:44

maxie
Member
From: Europe
Registered: 2005-02-15
Posts: 84

Re: Lunar economics etc

Coal produces ~10kW/kg and cost $50/MT so ~$200/kW.

0.005 $/KW ?

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#95 2007-02-17 15:03:56

Grypd
Member
From: Scotland, Europe
Registered: 2004-06-07
Posts: 1,863

Re: Lunar economics etc

You are simply wrong grypd, D+He3 fusion is in fact much harder to fuse than regular D+T fusion and is little easier than D+D fusion as far as temperature. Where do you get this idea that D+D fusion is "hard to contain" or "hard to keep stable?" in fact because there are fewer electrons per fuel atom similar nucleus-densities are possible at a third less pressure.

While D+D/D+T do throw off a lot of neutrons, this is not necessarily a bad thing: D+He3 suffers a problem that these don't, which is D+He3 radiates a large proportion of its total energy release (about 5/6ths of it) as X-ray and Gamma rays, which are neither reabsorbed by the plasma nor really useful for power. This would also require heavy shielding for use in a space application to protect the crew.

Neutron radiation on the other hand is easy to stop with propellant on a space ship (Hydrogen) or light shielding (inches of plastic or water) plus has a handy trick: the neutrons can be captured by water from the primary coolant loop to heat it up. Handy, no? With space ships, the neutron radiation could pre-heat the Hydrogen propellant too.

And that water becomes radioactive? No problem, put it in a tank and sit on it for a few years, and the Tritium in it decays and goes away. Then its just regular water again, maybe a little heavy in harmless Deuterium. This might actually be the preferred way to get the energy out of a fusion reactor instead of betting on some Star Trek superhigh temperature MHD generator.

And you say that neutron-producing fusion will wreck the reactor? How do you know that? Who told you? How do they know? It takes a really terrific dose of neutron radiation to damage solids much, neutrons tend to fly right through most elements except Hydrogen and a few others. Simply don't build your reactor out of them. Modern-day fission reactors absorb pretty big doses of neutrons too, and have to contain 1000F water under high pressure (which requires far more force than a fusion reactor) for about a century or so without even the barest hint of a chance of failure. And thats with plain old steel alloys. Earth reactors, irrespective of their space counterparts, have no mass restrictions either.

Perhaps its my fault but the damage I was refering to the reactor vessels is not Inferred Radioactivity but that of Thermal radiation. D-D reactions are very hard to keep away from the reactors side so damage and wear is intense. D-T reactions do not interest me as that will Never be allowed to be the defacto fusion reactor. It may be the first reactor fuel but we will move to something that costs less to handle and to store the byproducts from. It may be easier to start fusion reactions but the inert Lithium and the use of what is a nuclear weapon trigger product will stop its use as a universal fusion fuel. Not only that but we will need fission reactors to just make the fuel as even with some being made during the neutron reaction with the lithium it will still not be enough. Then we get to the real problem that of the leaking of radioactive materials and that is what Tritium is and it will leak and certainly more than any current nuclear station is allowed to.

Then we have the inferred radiation which will be 100 times stronger than any nuclear power plant so the reactor vessel will suffer irradiation at a rate of 100 times that of a nuclear reactor and as such the increased cost of storage and replacement of the fusion reactor.

The JET reactor showed us just how dificult it is too do a D-T reactor as just a single test put the reactor in a state where it had to be remotely operated.

Still the efficiency of the He3 is in the ability to get energy out of the process and though its not the Moon that will provide the fuel it can though help us get it. And it will be a long time before we use this fuel is it not. And by that time the actual political and enviromental pressures will determine if we even bother going to fusion.


Chan eil mi aig a bheil ùidh ann an gleidheadh an status quo; Tha mi airson cur às e.

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#96 2007-02-17 16:37:36

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Lunar economics etc

Your post makes no sense Grypd, D+He3 fusion would cause much more severe thermal stress on the reactor since much more of its energy is released as heat and X-Rays instead of neutron radiation like D+D/D+T (which flies right through the casing of the core mostly and is easy to capture). The high neutron output of the core is a good thing, and makes it easier to get the energy out of the core versus D+He3.

X-Rays are used in fusion bombs to vaporize the tamper of the "secondary" you know too, which would really damage the linings of the core. Good thing D+T doesn't make much X-Ray radiation. But I digress, the point being, you can operate a D+T reactor a small fraction of the temperature of a D+He3 core and still extract as much energy via neutron energy conversion. Actually, for a given density of plasma, D+He3 has 50% higher pressure making it that much harder to contain. D+D is only harder because less of its energy is converted to heat, which would help sustain the reaction, requiring higher burn rates.

I reject your absolutionist stance on the use of Tritium for fusion too: Tritium is not any harder to store than regular Hydrogen, and while some escape is probably likely it simply isn't very dangerous. Its a wimpy short-lived beta emitter, not a long-lived gamma source, and has a half life of only ~4yrs. The "Tritium problem" isn't, not for fusion nor for fission reactors, and is pointed to as a "problem that can't be fixed" as a way for environmental radicals to shut down fission power. It doesn't even extend beyond the reservation for plants, and you can even buy Tritium-powered glow lights in the UK as a novelty item.

I can hardly believe you fell for it that easily.

And use in bombs? Please, you don't need Tritium to make a bomb! Tritium is merely a booster for an atomic bomb, and designs that use it are complicated such that terrorists or rouge states wouldn't even bother with it. The fissile fuel is, has been, and will continue to be the only sensible way to stop nuclear proliferation.

Once we have D+T reactors up and running, we get another benefit too: because they generate significant amounts of neutron radiation, they could probably provide a large fraction of the Tritium they would need from Lithium bombardment. Some of the water used for neutron shielding/capture will also become Deuterated probably, and could be removed to provide the other component. The fuel for the reaction is D+T, but the stuff we actually truck into the plant is mainly Water and Lithium. Very little Deuterium nor Tritium would likely have to be imported.

Helium-3 on the other hand, being ten times at least harder to fuse than D+T, won't be worthwhile in any case: the #1 problem with fusion power is still making more power than is required to sustain the reaction, and here D+T is so much easier than you can use a far smaller and cheaper reactor. Neutron radiation energy is easier to capture/use and might be used to produce more fuel for the reactor anyway, unlike D+He3 that throws away most of its power as deadly X-Ray/Gamma rays.

You would have to operate a D+He fusion reactor by remote too, the Gamma would be too hard to block. Even worse for space ships, is they don't have the luxury to lug the extra Gamma shielding needed to protect the crew.

And what nonsense is this about the Moon "helping" us get He3? Its the ratio of dust to He3 which is the problem, not so much the actual amount of dust, and this won't change no matter how much you want it to. When will a hundred million tonnes of dust become okay to get one tonne of He3? Answer: never.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#97 2007-02-17 17:46:39

Grypd
Member
From: Scotland, Europe
Registered: 2004-06-07
Posts: 1,863

Re: Lunar economics etc

The process to make tritium is used to make higher yield fisible material for nuclear weapons. We cannot allow the whole world to use this process when certain countries will use this to develop bomb material. Heat and electrons is what an He3-D reactor produce.

If we use a deutrium/Tritium fusion reactor the financial advantage of such a device will likely be negated and the costs to operate similar to that of a nuclear plant. Containment of tritium is difficult and it is widely accepted that leaks will not only happen but they will be routine. Heavy neutron production will happen as it has to, to be able to heat water to power turbines.

GCN you state that the He3 reaction will create X ray radiation as far as I have seen this is not the case. In fact the radiation produced is usually Neutron but of a much smaller percentage than that of a D-D or D-T reaction. What are your sources.

He3-D will be hard to do but if we want a cheaper to operate system as long as we have the means to get the He3 out of the gas giants then we have it. Still I will probabily not be alive to see it in operation or any fusion in operation the speed it is going. Containment vessels we currently use cannot hold fusion power so new ones will have to be invented. And yes D-T fusion is less hot.


Chan eil mi aig a bheil ùidh ann an gleidheadh an status quo; Tha mi airson cur às e.

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#98 2007-02-17 20:30:04

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Lunar economics etc

No, you are all wrong

First, Tritium by itself is completely worthless for making bombs, since Hydrogen (fusion) bombs require an Atomic (fission) bomb to initiate the reaction. Thus, you must have high purity Uranium-235 or Plutonium-239 to make a nuclear weapon. Tritium is not a fissile material (able to undergo a fission chain reaction).

And again, you are wrong: D+He3 does indeed produce a large amount of electromagnetic radiation (in the X-Ray region mostly) through something called the Bremsstrahlung effect, which occurs in all fusion reactions through nucleus-electron collisions. This radiation is "powered" by the fusion reaction, and hence consumes some of the energy released by said reaction. The catch is that different fusion reactions release different fractions of their energy as Bremsstrahlung radiation, and D+T releases ~26.5 times less than D+He3. There is no effective way to mitigate this effect with any practical reactor design. Its all there in Wikipedia if you know what you are looking for and looking at.

Again, I reject your simplistic and irrational view about Tritium storage: its a gas, we can store gasses pretty well now, there is nothing magical or special about it. In fact it acts much like Hydrogen or Helium. We make and store much nastier gasses all the time, Boron Trifluoride, Uranium Hexafluoride, Hydrogen Fluoride, Phosgene, etc etc and these are a whole different world of deadliness than mildly radioactive Tritium. Why aren't you whining about them? Shouldn't we force the closure of all those industries that use them then? If need be, we could even store the Tritium as a solid or liquid by binding it to something like was done for large Hydrogen bombs.

Some leakage is bound to occur, but I maintain that we are good enough now at storing it that its not a hazard if very small leaks occur because its not a terribly dangerous radiation source. A little bit won't hurt anyone. I reject your baseless notion that there will be "routine" leaks either, which is insulting to the tremendously disciplined nuclear engineers. Only if you parrot the mindless environmental radical position that "no leaks or even risk of leaks are acceptable" could you possibly speak against Tritium storage & handling.

We don't need, nor even want Helium-3 fusion, even if we could get the stuff.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#99 2007-02-18 14:43:24

Grypd
Member
From: Scotland, Europe
Registered: 2004-06-07
Posts: 1,863

Re: Lunar economics etc

No, you are all wrong

First, Tritium by itself is completely worthless for making bombs, since Hydrogen (fusion) bombs require an Atomic (fission) bomb to initiate the reaction. Thus, you must have high purity Uranium-235 or Plutonium-239 to make a nuclear weapon. Tritium is not a fissile material (able to undergo a fission chain reaction).

But it is a major method to develop more effective bombs. But there is also the need to develop nuclear reactors so that Tritium production can occur. For fusion to be an effective replacement power source for electricity generation then most countries in the world will have to use it. This means even those countries that we have a real objection to will have to have the right to create breeder reactors just so they can power there Fusion reactors. This nuclear waste storage not only poses a security risk for the world but also will be expensive to store.

And again, you are wrong: D+He3 does indeed produce a large amount of electromagnetic radiation (in the X-Ray region mostly) through something called the Bremsstrahlung effect, which occurs in all fusion reactions through nucleus-electron collisions. This radiation is "powered" by the fusion reaction, and hence consumes some of the energy released by said reaction. The catch is that different fusion reactions release different fractions of their energy as Bremsstrahlung radiation, and D+T releases ~26.5 times less than D+He3. There is no effective way to mitigate this effect with any practical reactor design. Its all there in Wikipedia if you know what you are looking for and looking at.

According to Wikipedia the hotter the plasma the less there is a loss of energy from Bremsstrahlung radiation as it is caused by the effect of electrons hitting other electrons or Ions that are cooler. It will be present in all Fusion reactors including D-T, D-D and D-He3 but the best method to mitigate is to have a much hotter Fusion reactor.

Again, I reject your simplistic and irrational view about Tritium storage: its a gas, we can store gasses pretty well now, there is nothing magical or special about it. In fact it acts much like Hydrogen or Helium. We make and store much nastier gasses all the time, Boron Trifluoride, Uranium Hexafluoride, Hydrogen Fluoride, Phosgene, etc etc and these are a whole different world of deadliness than mildly radioactive Tritium. Why aren't you whining about them? Shouldn't we force the closure of all those industries that use them then? If need be, we could even store the Tritium as a solid or liquid by binding it to something like was done for large Hydrogen bombs.

Some leakage is bound to occur, but I maintain that we are good enough now at storing it that its not a hazard if very small leaks occur because its not a terribly dangerous radiation source. A little bit won't hurt anyone. I reject your baseless notion that there will be "routine" leaks either, which is insulting to the tremendously disciplined nuclear engineers. Only if you parrot the mindless environmental radical position that "no leaks or even risk of leaks are acceptable" could you possibly speak against Tritium storage & handling.

We don't need, nor even want Helium-3 fusion, even if we could get the stuff.

It is not my view that Tritium loss will be a constant thorn in the process it is the view of the EFDA-JET team. They have designed means to limit the loss but cannot stop all. It will be at present a constant leak due to not having a process to stop all loss. Invent one and you certainly can make a lot of money especially since it is an extremely expensive product they are leaking.

GCN you state I am whining but unless you find a means to solve this issue you will find another group of people quite willing to use it as a means to stop fusion getting off the ground. Simplistic and Irrational you scream but so what, it is still a radioactive gas probabily going to end up leaking. Coal plants produce a lot more radiation than any nuclear plant but where are the protestors. Staking out the front door of your local nuclear plant. It is this belief that has basically stopped new nuclear plants from being created for a long time.

Only if you parrot the mindless environmental radical position that "no leaks or even risk of leaks are acceptable" could you possibly speak against Tritium storage & handling.

I dont have to from your very post is all that is needed. GCN the problem with your view of the world is that you dont understand perception. The perception of radiation is always negative. Public perception is in one word negative. It is almost impossible to get permission to do anything if the view of those who matter is negative from the start.


Chan eil mi aig a bheil ùidh ann an gleidheadh an status quo; Tha mi airson cur às e.

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#100 2007-02-18 15:01:16

maxie
Member
From: Europe
Registered: 2005-02-15
Posts: 84

Re: Lunar economics etc

No, you are all wrong

First, Tritium by itself is completely worthless for making bombs, since Hydrogen (fusion) bombs require an Atomic (fission) bomb to initiate the reaction.

Considering muon-catalysed fusion and powerful lasers that are available today, this may no longer be true. We might not even know it...

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