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BigJim
2003-Apr-06, 05:06 PM
Due to the change of topic in this board, I have renamed it. The question: Should nuclear reactors be used for spaceflight?

Glom
2003-Apr-06, 08:55 PM
Chemical propellants can only get us so far. We need to use the nuclear option. And for everyone nuclear engine built for scientific missions, that a bit less fissile material to be turned into a nuclear weapon.

g99
2003-Apr-06, 09:00 PM
You will still have to get around the naysayers in Florida (or wherever you choose to launch it). Someone will come out saying that "I don't want that thing blowing up over my house. Radiation is going to kill us all if it does."

Depending on what they use to launch it, i might be one of them. Even if i am further north and west than it would probobly ever reach.

I know it won't turn into a bomb, but the chance of spreading the plutonium over a long range does scare me.

I would be all for it if they launched from a sea based platform or a isolated (and uninhabited) island platform. Plus if it is near the equator, it probobly would be cheaper to run anyways.

Colt
2003-Apr-06, 09:23 PM
What about Bikini Atol? The tan isn't only from the Sun. :P -Colt

Glom
2003-Apr-06, 11:01 PM
Well g, your sacrifice will not be in vain. :D

On Apollos 12 thru 17, they carried a plutonium rod to run the RTG on the ALSEP. This was contained inside a protective cast for the transit so that if the rocket blew up, there would be no contamination. Good thing too. Apollo 13's plutonium rod is currently located at the bottom of the Marianas Trench, I think. But it is cocooned safely inside the cask where it can't hurt anyone. There are ways to ensure protection.

nexus
2003-Apr-06, 11:52 PM
I'm a strong believer in nuclear power, to solve energy problems on Earth and anywhere else it could be used (Including Space), however, I would think the most major damage caused by a nuclear incident in space would be an EMP blast, I've read that one might be generated by a nuclear explosion in space, I'm not sure if thats still an excepted theory, but the damage caused by a large EMP blast would be catastrophic (Say bye-bye to most satalites at the very least).

DStahl
2003-Apr-06, 11:54 PM
The RORSAT reactors are very briefly described on this page (http://www.globenet.free-online.co.uk/ianus/npsm2.htm#2_2_1):

"The reactor core consists of 37 cylindrical fuel elements with 31.1 kg of highly enriched (90%) uranium-235 embedded in a beryllium casing. The cooling liquid for the reactor is liquid sodium-potassium. The thermo-ionic converter uses the dissipated heat to create electrical energy with an efficiency as low as 2 to 4%."

The later Russian TOPAZ reactors:

"'TOPAZ-2 small-sized nuclear power system with a thermionic converter represents a power source developed around a nuclear reactor and a thermionic heat-to-electricity converter.'"

"'Advantages: high power and reliability; long lifetime; small overall dimensions; complete radiation safety; the possibility to fully discharge the fuel and to store/ship it separately from the system; the possibility of final fuel loading directly during the system pre-flight preparation.'"

"'Application: space power systems. ... Characteristics of the reactor core: height, mm 375; diameter, mm 260; uranium charge, kg up to 27; guaranteed lifetime, yr over 3.' [KURCHATOV]"

SNAPSHOT (SNAP-10A) was apparently the only US nuclear reactor launched, and I haven't found details on the reactor type. The website linked above says,

"'SNAP-10A operated at more than 500 W for 43 days. Since 1979, many objects separating. The only U.S. space reactor flown, a test flight in 1964, used uranium-235 as the fuel.' [TRW, page 90, emphasis added]" --emphasis on the web page, DS

"Technical information about the SNAP-10A, the amount of U-238 used, or the effect of the continuing disintegration of the satellite mentioned in the TRW Space Log 1996 was not given in the sources available at the time of writing."

I think BigJim is aware of this, but just for background: the rest of the US space probes used a modest amount of nuclear material to generate electricity (in a unit called an RTG) and did not carry actual nuclear reactors. A NASA spokesman talking to a PBS reporter said, "This is not a nuclear reactor. They are nuclear batteries. They’re not used for propulsion. It’s not a nuclear power plant. We don’t have any nuclear reactions going on. We simply use the isotope to generate heat, and from the heat we generate electricity for the spacecraft."

Colt
2003-Apr-07, 12:02 AM
We also use nukebats in buoys which are left along for along time and solar power is not viable. -Colt

BigJim
2003-Apr-07, 12:09 AM
Yes, I do know about RTGs. I find it humorous when anti-nuclear groups, instead of confronting war, poverty, starvation, and disease, attempt to block the exploration of space. Remember all the panic when Cassini launched? I called these people's theory "Cassini Radiation And Plutonium"-get it?

Thank you for finding data on the reactors. I wonder how the Soviets were able to make what seems to me to be a HTGCR (High Temperature Gas Cooled Reactor) fit inside a satellite. And 90% U-235? Wow! That's really dangerous. Now, don't get me wrong, I am all for nuclear power for space exploration, but 90% U-235 could easily explode like an A-bomb! That is weapons-grade material!

Also, in response to

You will still have to get around the naysayers in Florida (or wherever you choose to launch it). Someone will come out saying that "I don't want that thing blowing up over my house. Radiation is going to kill us all if it does."

Depending on what they use to launch it, i might be one of them. Even if i am further north and west than it would probobly ever reach.

I know it won't turn into a bomb, but the chance of spreading the plutonium over a long range does scare me.

I would be all for it if they launched from a sea based platform or a isolated (and uninhabited) island platform. Plus if it is near the equator, it probobly would be cheaper to run anyways

I just briefly want to say something about RTGs. As DStahl pointed out,
US space probes used a modest amount of nuclear material to generate electricity (in a unit called an RTG) and did not carry actual nuclear reactors. A NASA spokesman talking to a PBS reporter said, "This is not a nuclear reactor. They are nuclear batteries. They’re not used for propulsion. It’s not a nuclear power plant. We don’t have any nuclear reactions going on. We simply use the isotope to generate heat, and from the heat we generate electricity for the spacecraft

The RTGs are fueled by the decay of Pu-238. Now, an average RTG contains about 100,000 Curies of radiation. On a personal level, this is not a trivial amount- you certainly would not want this much radioactive material around your house. However, on a more global scale, it is utterly insignificant. If an RTG were to explode and be dispersed into Earth's biosphere, instead of sinking into the Atlantic like a brick, which it would actually do, the 100,000 Curies represents less than 1 one-hundreth of one percent of a typical nuclear bomb test, and an even smaller fraction of the half dozen or so sunken nuclear submarines rusting away on the seafloor, like the Kursk and the Thresher. The claim that an exploding or reentering RTG poses a threat to people is simply untrue.

Also, thanks for answering my original question, which was the point of this board! However, I think now we can delve into a deeper and more interesting question:

Should nuclear fission reactors be used for spaceflight? Why or why not?

Colt
2003-Apr-07, 12:21 AM
Magnetic fusion reactors would be better.. -Colt

BigJim
2003-Apr-07, 12:26 AM
Agreed, but they are much too complicated and heavy to see service in spacecraft in the near future. For a discussion of tokamaks, go to the "Tokamak reactor" (I think that is the title) board in the "Against Mainstream" section.

Colt
2003-Apr-07, 06:44 AM
I am talking about a spherical reactor, small and basically self-contained. -Colt

David Hall
2003-Apr-07, 07:31 AM
...and an even smaller fraction of the half dozen or so sunken nuclear submarines rusting away on the seafloor, like the Kursk and the Thresher.

The Kursk at least, is not rusting on the seafloor any longer. They just broadcast a big Discovery channel special here about how they recovered the wreckage.

Just a nitpick. :-)

Glom
2003-Apr-07, 12:45 PM
I think RTGs are rather good. Could they be run off the refuse from fission reactors?

kucharek
2003-Apr-07, 12:52 PM
I think RTGs are rather good.

Uh, the efficiency factor of RTGs can make you whince. RTGs are nice for long-term electrical energy low-output stuff, but no good for anything that's related to propulsion.

Harald

ToSeek
2003-Apr-07, 02:29 PM
I think RTGs are rather good.

Uh, the efficiency factor of RTGs can make you whince. RTGs are nice for long-term electrical energy low-output stuff, but no good for anything that's related to propulsion.

Not entirely true: NASA is looking at using RTGs to power ion drives, something called radioisotope electric propulsion (REP). It would be slow, but it would get you there.

Meanwhile, I do think we need to look at nuclear options in space. We're going to be hard put to do any serious exploration of the outer solar system using chemical rockets.

Glom
2003-Apr-07, 03:57 PM
Uh, the efficiency factor of RTGs can make you whince. RTGs are nice for long-term electrical energy low-output stuff, but no good for anything that's related to propulsion.

I was not necessarily thinking of just propulsion, but also for electrical power as well.

DStahl
2003-Apr-07, 07:05 PM
I'm not very well informed on this, but it seems to me that any launch of nuclear material involves a risk. Maybe we can minimize the risk if the nuclear fuel can be transported in a well-hardened, shielded container and then inserted in the reactor in orbit?

It's ironic that we have built so many devices specifically designed to hurl plutonium payloads long distances and smash them into populated areas of the Earth, and yet we worry about launching even a single nuclear reactor into space.

Thumper
2003-Apr-07, 07:27 PM
It's ironic that we have built so many devices specifically designed to hurl plutonium payloads long distances and smash them into populated areas of the Earth, and yet we worry about launching even a single nuclear reactor into space.

Wow, that point just hit me like a frying pan over the head. (Stops, reads it again, shakes head slowly).

Well put DStahl.

Glom
2003-Apr-07, 07:34 PM
A corollary to your point DStahl. For every gram of plutonium or whatever we launch into space for use on spacecraft, that's a gram less of plutonium that will be turned into a nuclear bomb.

BigJim
2003-Apr-07, 07:59 PM
A few comments:


I'm not very well informed on this, but it seems to me that any launch of nuclear material involves a risk. Maybe we can minimize the risk if the nuclear fuel can be transported in a well-hardened, shielded container and then inserted in the reactor in orbit?

This is one of the reasons why we don't have reactors in space yet. The shielding required would weigh so much that it would put severe penalties on the mission. On Apollo missions, there was a small rod of spent reactor fuel that powered an RTG for the ALSEP. On Apollo 13, there was a great deal of concern that the reentering fuel rod could cause harm, but the fuel rod was packaged in a heavy cermaic cask to prevent this sort of accident.

However, the cask was extremely heavy (does anyone know how much?) and cut heavily into the LM weight allowances, which were already unimaginably tight for such a relatively flimsy craft.

In the same vein, heavy shielding for reactors, while a good bonus, is very difficult to put on cash and weight strapped missions. Also, inserting the fuel inorbit would just complicate things, since the fuel is being transported anyway.

Another, more feasible idea is to have an NTR (Nuclear Thermal Rocket) rocket launch the payload into space, and the advantage of using the NTR (900 Isp) would allow heavy shielding of the reactor. Go to www.astronautix.com/engines/nervantr.htm, www.space.com/businesstechnology/nuclear_power_000718.html , www.fas.org/nuke/space/c04rover.htm and www.uic.com.au/nip82.htm for information on NTRs.


Not entirely true: NASA is looking at using RTGs to power ion drives, something called radioisotope electric propulsion (REP). It would be slow, but it would get you there.


There are three types of electric propulsion, REP, SEP (Solar electric propulsion) and NEP (Nuclear electric propulsion). Of the NEP is by FAR the most efficient and powerful, with a much higher thrust than the SEP and a much, much, MUCH higher thrust than the REP. NEP would also have enough power after the thrust (which would be higher than any chemical rockets) to power multi-kilowatt communications systems, instead of the 40 W of radiated energy we use now, in addition to high power science such as radar and laser studies.


The Kursk at least, is not rusting on the seafloor any longer. They just broadcast a big Discovery channel special here about how they recovered the wreckage.

Yes, I saw that special. I wonder how I forgot that.




I am talking about a spherical reactor, small and basically self-contained.
That would be great for spaceflight, but that is exactly what I am talking about: Tokamaks now are huge and heavy. A Saturn V could probably barely, if at all, put one into LEO (can anyone do the calculations?). A spherical tokamak would be the perfect space power source and should be the standard power and engine source within 50 years.

Keep in mind that any launch of a space fission reactor would be over an ocean (The Atlantic from Kennedy, the Sea Launch platform, the Kourou site, the Chinese sites) except Bakinour, and I would not want to launch a fission reactor on a Proton or Soyuz. Even if it did break up, like I explained, it would not be a major hazard, although some shielding probably is in order. But then again, consider this:
There have been 317 nuclear bombs tested just by the United States. This released a total of about 330 trillion curies of radiation
A fission reactor space with about 10 mWe should carry about 1 million curies or so, and the total radiation we get from the 330 trillion curies is about 5 mrem; this is less than you get from eating Brazil nuts each year. Now, 1 million curies on this scale is almost nothing. [/b]

Colt
2003-Apr-07, 08:01 PM
The thing about nuclear missiles is that they are meant for destruction. If one explodes (not detonates mind you) on launch the contamination is incomparable to the damage if that missile's brethren do not reach their targets and stop other missiles from launching.

On the other hand, anything launched by NASA or the Russians is sure to be much safer than most of the ICBMs. If those explode they could just fish the container with the nuclear material out of the water. -Colt

daver
2003-Apr-07, 08:35 PM
A spherical tokamak would be the perfect space power source and should be the standard power and engine source within 50 years.
]

Did i miss something? I thought that no controlled fusion reactor (spheromak or takomak or inertial confinement or whatever) had attained anything other than theoretical breakeven; that the cases where theoretical breakeven had occurred were using fuel combinations that would not be used in a production reactor and were only used in those reactors because the reactor was being decomissioned.

BigJim
2003-Apr-07, 09:02 PM
BigJim wrote:

A spherical tokamak would be the perfect space power source and should be the standard power and engine source within 50 years.
]


Did i miss something? I thought that no controlled fusion reactor (spheromak or takomak or inertial confinement or whatever) had attained anything other than theoretical breakeven; that the cases where theoretical breakeven had occurred were using fuel combinations that would not be used in a production reactor and were only used in those reactors because the reactor was being decomissioned.

Well, as I explained on another BABB post,

There are two main kinds of thermonuclear fusion that we could achieve. One, which is what we are experimenting with now and which we occasionally use in thermonuclear bombs, is deuterium-tritium fusion. Deuterium, a hydrogen atom with a neutron, and tritium, a hydrogen atom with two neutrons, are the easiest atoms to fuse. Deuterium tritium or D-T fission creates a helium-4 atom and a neutron, as well as 17.6 million million electron volts (MeV), about ten million times the energy burning coal releases.

The helium-4 nucleus created, also known as an alpha ray, is a charged particle, and the magnetic field of a tokamak confines it in the magnetic field, and as it collides with surrounding deuterium and tritium it heats the plasma. However, the neutron is uncharged and collides with the wall of the tokamak. Some of the neutrons will collide with a lithium blanket, creating more tritium, and the heated walls could turn a generator, but eventually the wall of the tokamak would need to be replaced.

The other kind of fusion, D-He3 or deuterium-helium 3 fusion, creates 18 MeV of energy, one hydrogen nucleus, one helium-4 nucleus, and no neutrons. So, clearly, this type of fusion is preferable as it creates more energy and does not require the costly and dangerous replacement of radioactive walls. However, D-He3 fusion is harder to start than D-T fusion. The larger problem with D-He3 fusion, though, is that He-3 does not exist on Earth. The solar wind has put it into lunar soil with about 4 ppb on average. While not much per unit of soil, over the whole moon this is more energy than all the fossil fuels on Earth. This is a reason for spaceflight and lunar colonization. There is also a great deal of He-3 in the outer planets, and it can be mined from their atmospheres.

The reason neither D-T nor D-He3 reactors currently exist is that the reaction needs to produce energy at a rate equal to the power being using externally to heat the plasma. This condition is called "Breakeven" and was first reached in 1997. The next step, called ignition, requires about 4 times more energy but can heat itself, and is the last remaining barrier to nuclear fusion plants.

Once this technology becomes available, though, it will by FAR be better than other power forms. It produces no pollution, cannot melt down, creates far more energy than any other natural source, and it should be fairly simple to build the facilities once the technology is acquired.

I'm not really sure what you mean by theoretical as opposed to real breakeven, but breakeven has been reached in tokamaks. Perhaps what you mean by not having used the fuel in a real production tokamak relates to D-T and D-He3 fusion. The only tokamaks on Earth have used D-T fusion. The first generation of tokamaks will likely be D-T. The second and better generation will use D-He3 fusion.

Try epub.iaea.or.at/fusion/ and fusedweb.pppl.gov/ for more information.

ToSeek
2003-Apr-14, 03:37 PM
Article about propulsion power sources (http://www.firstscience.com/site/articles/power.asp)

ToSeek
2003-Apr-14, 03:39 PM
And another (http://www.firstscience.com/site/articles/rocket.asp)

daver
2003-Apr-14, 11:11 PM
The reason neither D-T nor D-He3 reactors currently exist is that the reaction needs to produce energy at a rate equal to the power being using externally to heat the plasma. This condition is called "Breakeven" and was first reached in 1997. The next step, called ignition, requires about 4 times more energy but can heat itself, and is the last remaining barrier to nuclear fusion plants.


I'm not really sure what you mean by theoretical as opposed to real breakeven, but breakeven has been reached in tokamaks. Perhaps what you mean by not having used the fuel in a real production tokamak relates to D-T and D-He3 fusion. The only tokamaks on Earth have used D-T fusion. The first generation of tokamaks will likely be D-T. The second and better generation will use D-He3 fusion.

Try epub.iaea.or.at/fusion/ and fusedweb.pppl.gov/ for more information.

What i had dimly recalled was one of the Euopean fusion experiments. They (if i remember correctly) had been running their tokamak with straight deuterium, but had one final run with D-T. That one, as you explained, had achieved breakeven. I thought that the ratio of energy in to fusion energy out was quite a bit higher than 4, though.

crazy4space
2003-Apr-15, 05:38 PM
[quote="BigJim"]Does anybody know what type of nuclear reactor (e.g. Boiling Water Reactor, Pressurized Water Reactor) the SNAPSHOT mission and the RORSAT missions used?

I think (smell the smoke) that we are going about this the wrong way. I saw on the Discovery channel where we are redoing all of the electrical experiments that we did in the early 40's - what these guys were doing was working on getting rid of the gravity around the airplane. Amazing enough they were working with counter rotating magnets and have already levitated thousands of pounds - now we can generate millions of more volts than we could back then. I sure hope one of these smart kids can figure this out.

My initials are on the moon because Gene Cernan put them there.

daver
2003-Apr-15, 06:33 PM
[quote=BigJim]Does anybody know what type of nuclear reactor (e.g. Boiling Water Reactor, Pressurized Water Reactor) the SNAPSHOT mission and the RORSAT missions used?

I think (smell the smoke) that we are going about this the wrong way. I saw on the Discovery channel where we are redoing all of the electrical experiments that we did in the early 40's - what these guys were doing was working on getting rid of the gravity around the airplane. Amazing enough they were working with counter rotating magnets and have already levitated thousands of pounds - now we can generate millions of more volts than we could back then. I sure hope one of these smart kids can figure this out.

My initials are on the moon because Gene Cernan put them there.

Do you have more details? It sounds as if you were saying that Discovery reported an anti-gravity machine from the 40's. Or are you talking about magnetic levitation? Magnetic levitation may be good for trains, it might be good for a 0th stage for a space launcher, but i can't think of any other application for space flight.

crazy4space
2003-Apr-15, 08:46 PM
Do you have more details? It sounds as if you were saying that Discovery reported an anti-gravity machine from the 40's. Or are you talking about magnetic levitation? Magnetic levitation may be good for trains, it might be good for a 0th stage for a space launcher, but i can't think of any other application for space flight.


Daver, What they were trying to do was create a magnetic field that would encompass the entire airplane. The way I understood it they started with the magnetic levitation and worked their way to a new theroy. Sends the mind reeling. What if it were possible. How much fuel would it take to reach orbit if your plane were weightless? How safe would this be vs. rockets?

My initials are on the moon because Gene Cernan put them there.

Glom
2003-Apr-15, 10:10 PM
If you're spacecraft was located on the magnetic equator, you could attach a big coil to it oriented horizontally, magnetically shield half of it (I think you use soft iron or something), then run a large current through it such that the current is running eastward through the unshielded half. By Flemming's left hand rule, your spacecraft would shoot skyward. When it has gained sufficient altitude, you could rotate the coil about an axis that runs parallel with the B-field lines round to the east side of the spacecraft and this would change the direction of the induced force to an easterly vector which would drive your spacecraft into orbit. Yes, it's that simple. :wink:

daver
2003-Apr-15, 11:51 PM
Daver, What they were trying to do was create a magnetic field that would encompass the entire airplane. The way I understood it they started with the magnetic levitation and worked their way to a new theroy. Sends the mind reeling. What if it were possible. How much fuel would it take to reach orbit if your plane were weightless? How safe would this be vs. rockets?

My initials are on the moon because Gene Cernan put them there.

I didn't see the episode; i'm trying to guess what they might have been showing. It could be that they were playing with some sort of magnetic levitation--rapidly changing magnetic fields under the airplane could set up a short-range repulsive force. I don't see much point to that, unless they were looking at an alternative to a steam catapult or JATO for launching aircraft--they could levitate them and accelerate them based on hardware built into the runway, allowing for wheels-up launches. That seems pretty dangerous, especially for piston-engined aircraft where the steel bits in the engine would be attracted while the aluminum bits (particularly the tail) would be repelled. Power failures part-way through the launch would be nasty. It'd also play hob with the navigational bits (maybe they could use flux gate compasses instead of magnetic ones).

Anyway, if this was what they were doing, i see no space applications. The effect is short range (unless you're planning on converting Australia to a giant electromagnet), and the craft still need to get up to orbital velocity. A subcontinental array might help in getting above a good portion of the atmosphere, but a maglev track up Pike's Peak or Mauna Loa would do the same (the astronomers might not care too much for the Mauna Loa idea) and be a LOT cheaper.

Glom
2003-Apr-24, 04:38 PM
From Space.com (http://www.space.com/businesstechnology/technology/prometheus_tech_030423.html).


On May 3, a protest of "NASA Plutonium launches and warfare in space" is slated outside the gates of the Kennedy Space Center in Florida. :evil:

Warfare in space! Have they never heard of the 1967 Outer Space Treaty. I don't like this idea of linking the two. Using nuclear power in space for scientific purposes has concerns simply for the risks involved in launching fissile and radioactive materials. But the idea of putting that in the same camp as some nutcase wanting to start nuclear space warfare is downright insulting.

I told some friends about the results of the poll that BigJim has just removed, which scored an almost unanimous support for nuclear power in space, they said that they weren't surprised because the people on this board were more educated that most of the public so they can make a more intelligent judgement. 8)

BigJim
2003-Apr-24, 11:05 PM
From that article:

But the major poster child for Prometheus is the Jupiter Icy Moons Orbiter, or simply known as JIMO.......The spacecraft would orbit three different moons of Jupiter where earlier spacecraft discovered evidence for vast saltwater oceans hidden beneath icy surface layers: Europa, Ganymede and Callisto.

ALRIGHT!

That would be a great mission, that would mostly make up for the cancellation of the Europa Orbiter.


In part, JIMO is a "showoff" mission. That is, NASA wants this Prometheus-push to validate safe and reliable use of electric propulsion powered by a nuclear fission reactor.

"We completely change the way we look at everything if we figure out how to do this," said Sean O'Keefe, NASA Administrator..."This is going to be the catalyst that will get you to that," O'Keefe said.... "If we continue to kind of bump along on gravity assists, sling shots, and hope you get the flyby right…you ain't going anywhere," O'Keefe said.


You go, Sean. A nuclear fission reactor would provide a hugescience return from the outer planets, which could include movies of the Jovian system, high-powered radar, tuanble lasers, three-dimensional mapping - the possibilities are almost endless. In addition, NEP (Nuclear Electric Propulsion) could be employed, which would either increase the speed of the mission, increase the science payload, or allow the mission to be launched on a smaller (Delta-class?) rocket.

This new administrator is great! No more, "faster, better, cheaper" and X-33 cancellations, we're going nuclear! Yeah! :D

But, referring to Glom's group,

Also falling under the group's crosshairs are the soon-to-be-launched Mars Exploration Rovers. Each robot is equipped with Radioactive Heater Units (RHUs) to help machinery survive super-cold Martian nights.

In their view, not only are they a danger if they careen back to Earth due to a launch failure. Even if the robots succeed they'll be planting a loathsome nuclear seed on Mars.


:evil: :evil: :evil:

How DARE they try to stop the MER mission from getting off the ground because they carry a few frecklingourtysdfing grams of plutonium!
The Mars Exploration rovers is NASA's best Mars mission, ever, and they may discover extant life - but, no, let's stop it in the case that a gram or two of plutonium might get released, which would kill everyone on Earth!
If these guys really want to destroy something nuclear, let it be bombs. I have no great love for nuclear bobms, but nuclear fission is our cleanest, most efficient, and best energy source. I recommend the book The Great Nuclear Debate.

End of rant. :)

BigJim [/i]

Glom
2003-Apr-24, 11:26 PM
F****** A, Bubba. And nice rant. 8)

I completely agree. With all the bad things in the world, nuclear weapons, deforestation, biochemical weapons and crap, nasty things going on in Africa and the Middle-East, they pick on a peaceful mission of science and discovery. If a few grams of plutonium were to be dispersed about the atmosphere, the resulting increase in radiation exposure would probably be negligable next to what you'd get on a hike through Dartmoor with all its granite and stuff.

There was an episode of Horizon a while back about the consequences of a dirty bomb attack. It was rather laughable because while they were trying to make the situation sound dire, the dangers posed by such a detonation were far less severe than I had ever imagined. Apparently the risk to people living in London if a bomb were to go off in Trafalgar Square is about one in a thousand times greater. Ahhh!! :roll: My Physics class encounter greater risk when doing radioactivity experiments.

And then these gimps moan about a few grams of plutonium?

It's the classic Radiation Boogey Man. People such as these who are ignorant of what is really going on think, "Nuclear! Must be really bad!" I would have thought they'd be pleased. That's a few grams of plutonium that won't be turned into nuclear weapons. But I thinks it's disgusting the way their ignorance is allowed to threaten proper science and exploration.

daver
2003-Apr-25, 12:54 AM
And then these gimps moan about a few grams of plutonium?


You realize of course that if you lined everyone on earth up in a straight line and accelerated that gram of Pu to 99.999999% the speed of light and aimed it to pass through all their heads that it would wipe out the entire population of the planet?

Hmm, you might have to flatten that gram of Pu out into a 10 cm diameter disc before you accelerated it.

BigJim
2003-Apr-25, 01:51 AM
Actually, it would probably vaporize by the time it hit a few thousand people (just guessing, I don't know what the calculation would be)

newt
2003-Apr-25, 05:58 AM
I'm for using nuclear propulsion, but hey, accelerating particles at peoples' pumpkins on a discussion where some may still have reservations about radiation and all? Better to learn 'em than burn 'em.
Couple of quick links about radiation and risks:

www.ne.doe.gov/pdf/SRPS_safety.pdf

(O.K...that's from the Dept. of Energy; many won't believe them)

and

www.pma.caltech.edu/~chirata/nuke.html

And a couple of interesting papers (that briefly address safety) at this site:

www.newworlds.com/nucpro.html

Cheers (and no, I wasn't taking you seriously).

Pinemarten
2003-Apr-25, 10:10 AM
They should be tried/used unto the point where the technology does more harm than good, and if /when that may happen, be reviewed on the merits, improved upon, and then attempted again.

ToSeek
2003-May-08, 04:23 PM
NASA awards contracts for radioisotope power technology investigations under Project Prometheus (http://www.spaceref.com/news/viewpr.html?pid=11472)

Glom
2003-May-08, 04:24 PM
Good to hear. :D

BigJim
2003-May-11, 05:29 PM
No, no! Not radioisotopes! REACTORS!!!!! :wink:

Madcat
2003-May-14, 02:27 PM
If you accelerated the Pu disc that much, I'll bet the junk that goes flying from the first couple thousand people will get the rest even if the disc does vaporise. Of course, a vaporised disc is probably more lethal than an unvaporised disc. If it's focused right, you might get a shaped charge out of the deal.

BigJim
2003-May-30, 10:15 PM
Facts about common RTG misconceptions (http://www.nuclearspace.com/facts_about_rtg.htm)

Glom
2003-May-30, 10:43 PM
Good article. I strongly support the development of nuclear technology in spaceflight. It's the only way to get us out of this rut.

It's very angering to hear about people protesting legitimate scientific mission because of nuclear payloads, when they have no idea what is actually going on. :evil:

BigJim
2003-May-30, 10:45 PM
Exactly. Remember those "Stop Cassini" morons?

Glom
2003-May-30, 11:09 PM
Of course, I would have thought they'd be pleased. That's one less bit of nukular material that will be used to make nukular weapons. (Yes, I know that the kind of plutonium used isn't fissile, but those nurks don't.)

I asked a friend about what he thought about the result of this poll, which clearly favours the nuclear option. He said he wasn't surprised because he'd imagine that those here would be more intelligent and more knowledgeable of the issues at hand to make a more educated judgement. 8)

ahb
2003-May-31, 12:23 AM
Wait until NASA starts using Z-space. Then we can fly faster than light.

Glom
2003-May-31, 12:37 AM
Bored with Apollohoax.com are we SaturnV? Dare I ask what Z-space is?

daver
2003-May-31, 12:38 AM
Don't we have to finish with X-space and Y-space first?

ahb
2003-May-31, 01:03 AM
Bored with Apollohoax.com are we SaturnV? Dare I ask what Z-space is?

Z-Space: Anti-reality; the opposite of normal space, where faster than light travel is possible. It is divided up into many sectors, of which the center mark is the home world, in sector 0 A 0, and everything else is measured from that. We live in sector 73 J 37, meaning 73 light years above the home world, J, or 9 light years to the right, and 37 lightyears behind it.

BigJim
2003-May-31, 01:41 AM
Please, ahb - this is a thread on nuclear power for spaceflight. If you really want to discuss "Z-space", put it in Against the Mainstream. I am talking about a modern-day power source for spacecraft and Earth, and I have no idea what you are talking about. Please don't try to explain. I'm not going to try to debunk that - as a science teacher of mine once told me, "Your argument cannot be defeated if no one can understand it."

BigJim
2003-Jun-04, 12:21 AM
This says it all. (http://www.nuclearspace.com/a_zubrin.html)

Read that and then just TRY not to like nuclear power for spaceflight.....

Or just try not to attempt to stop MER for its RHUs.... :roll:

Glom
2003-Jun-04, 01:02 PM
Of course, that plan of which he spoke involves Saturn V's, which are longer available.

Someone needs to be fired. :evil:

Glom
2003-Jun-04, 03:38 PM
Here's a NTR question from someone who doesn't know much about it.

It seems as though an NTR works by heating the propellant up to high temperatures and forcing it out the back. Would it be better to use a little heavy propellant or a lot of light propellant? Because here's my thought. Momentum is conserved and never lost. If you accelerate a heavy particle to a relatively low speed, it can have the same momentum as a light particle at a relatively high speed. But to force the relatively light particle to that momentum, you have to give it a lot more energy because of the square relationship. Since there is an inefficiency tax on energy transferred, wouldn't it be better to get the most momentum for the least energy and hence use something heavier? Nitrogen is quite heavy and is very very abundant aswell as being inert so the environmentalists can't get angry.

tjm220
2003-Jun-04, 03:45 PM
Here's a NTR question from someone who doesn't know much about it.

It seems as though an NTR works by heating the propellant up to high temperatures and forcing it out the back. Would it be better to use a little heavy propellant or a lot of light propellant? Because here's my thought. Momentum is conserved and never lost. If you accelerate a heavy particle to a relatively low speed, it can have the same momentum as a light particle at a relatively high speed. But to force the relatively light particle to that momentum, you have to give it a lot more energy because of the square relationship. Since there is an inefficiency tax on energy transferred, wouldn't it be better to get the most momentum for the least energy and hence use something heavier? Nitrogen is quite heavy and is very very abundant aswell as being inert so the environmentalists can't get angry.

Can't we just fire environmentalists out the back since they too are quite massive, abundant and after a brief time inert? :D (BTW I'm kidding)

BigJim
2003-Jun-04, 08:45 PM
Let's see - after environmentalists, hydrogen is the best propellant for NTR. All the proposals I've seen involve hydogen. Does anyone know why? I think something about its lightness makes it desirable, but I can't seem to remember why. I think, though that it is because the exhaust velocity of the rocket is the deciding factor in adding velocity to the spacecraft, and hydrogen is easy to accelerate because it is light. Hydrogen will be moving the fastest after going through a nuclear reactor, and the high exhaust velocity will allow for a high delta-v. Typically it is possible to reach a speed twice that of your exhaust velocity (except in the rockets in which the exhaust is light, like photon anitmatter rockets.)

Glom
2003-Jun-04, 09:05 PM
But the point I was making before is that it isn't about the velocity of the exhaust, but it's momentum. You can get the same momentum from a high speed light exhaust and a slow speed heavy exhaust. But with a high speed low exhaust, you need to give it more energy because unlike momentum which is velocity-linear, energy is velocity-square. So what I'm saying is, wouldn't it be better to use a fuel that gives you the same momentum but for less energy?

WorseAstronomer
2003-Jun-05, 07:04 PM
It's the classic Radiation Boogey Man. People such as these who are ignorant of what is really going on think, "Nuclear! Must be really bad.

I'm sure I'm not telling you anything you don't already know, but I remember reading somewhere that your standard MRI is really an NMRI, meaning NUCLEAR Magnetic Resonance Imaging. But, they dropped the, "N," for fear that people would decline the procedure if they knew that, "nuclear" was involved.

These are probably the same people that go to the beach to enjoy a nice sunny day, not knowing they're basking in the radiation from the biggest nuclear reactor in the solar system.

Glom
2003-Jun-05, 09:11 PM
:lol: to all points WA.

daver
2003-Jun-05, 11:17 PM
But the point I was making before is that it isn't about the velocity of the exhaust, but it's momentum. You can get the same momentum from a high speed light exhaust and a slow speed heavy exhaust. But with a high speed low exhaust, you need to give it more energy because unlike momentum which is velocity-linear, energy is velocity-square. So what I'm saying is, wouldn't it be better to use a fuel that gives you the same momentum but for less energy?

All right. Let's assume you're carrying a ton of propellant. You run it through your reactor, which imparts a certain temperature (energy) to it. Let's say m*v*v = 100, just for giggles. So if you run with a propellant of molecular weight 1, you get a velocity of 10. If you run with a propellant of molecular weight 100, you get a velocity of 1. So with the first fuel you have a total momentum of 1 ton * 10 (whatever our velocity units were), with the second your total momentum is 1 ton * 1 (velocity unit).

Of course, the situation is worse than that--you have the rocket equation to worry about., with its exponential component based on exhaust velocity.

This is a pretty simplistic argument--there are other complicating factors.

BigJim
2003-Jun-07, 12:11 AM
What do you think of the proposal? Just TRY, JUST TRY to take it apart.

wedgebert
2003-Jun-07, 04:04 AM
Here's how I think we should get nuclear power going in space.

Take someone rich (like Bill Gates) and see if they will donate a few billion (or find a few rich folks for a billion each). Then take that money to an island nation near the equator.

Use the money to hire the scientists and engineers you need, but don't tell them what you're doing. Also obtain any fissionable materials needed from the black market.

Develop and build the spacecraft in as much secrecy as possible. Have everyone sign such strict NDAs that it would be very very hazardous to ones health to break it :)

Finally, once you've built the craft and trained a few pilots. Just launch the darned thing. Don't wait for permission and ask for protests by people with nothing better to do with their weekdays than protest things they know nothing about, or for countries like the U.S. to get involved.

Just send a message from orbit saying "I told you it would work"

Glom
2003-Jun-07, 04:11 AM
Getting it done before the anarchist nurks know it's happening sounds like a good idea, but the covert development of nuclear technology could get us on terrorism list.

Here's a thought. Maybe Saddam Hussein is actually doing that. That's where all the WMDs went. He's development an NTR with them. Anthrax powered.

wedgebert
2003-Jun-07, 04:27 AM
Somehow I doubt that a bunch of geeks sitting on an island, lead by some other geeks is going to set off too many alarms.

BigJim
2003-Jun-07, 02:32 PM
But if we do that, we won't get teh public approval that the program would need. Developing NTRs in secret would probably frighten the anti-nukyular activists, because "of course, if the engines wouldn't kill us all, they wouldn't do the tests in secret." If we want NTRs to usher in a new era of unmanned outer solar system and manned inner solar system exploration, the public should know, too.

I assume that was a tongue-in-cheek suggestion?

Maybe we should consider e-mailing one of those "Stop Cassini" fools who still has a website up. Should be fun.

Glom
2003-Jun-07, 05:31 PM
Stop Cassini fools? :evil: :evil: :evil: :evil: Ignorant, anarchist nurks.

BigJim
2003-Jun-07, 05:46 PM
Well, instead we could e-mail the ignorant, stupid, arrogantly innane Stop Cassini anarchist anti-nukyular (insert word here).

Have you ever noticed that Michio Kaku is always supporting the anti-nukyular crowd? He seems to be a good writer in other fields, but I hate him in this one. A lot of the things he says are lies, plain and simple.

Tuckerfan
2003-Jun-07, 08:00 PM
What get's me are the protestors who bash the pro-nuclear rocket folks by saying, "Well, you don't live here! You don't have to worry about the fallout if one of those things blow up on launch." Hey, guys, I'd love to live in Florida, especially near the Cape where I could watch the launches from my yard. Of course, I can't afford to live there :evil:, but if any of the anti-nuke folks would be willing to set me up in such a place with a good paying job, I'll be happy to move. I'll even put a banner up in the front yard that says, "Go Nukes!" :D

BigJim, have ya got a cite for Michio Kaku being anti-nuclear? Not that I doubt you, but I've got a friend who's a big Michio Kaku fan who'd be interested in seeing that.

BigJim
2003-Jun-07, 08:19 PM
Have I?

http://www.animatedsoftware.com/cassini/mk9707fl.htm http://www.animatedsoftware.com/cassini/mk9708so.htm
http://www.animatedsoftware.com/cassini/kg9328jp.htm
(warning- that is the anti-nukyular Stop Cassini anarchist website)

http://southmovement.alphalink.com.au/antiwar/kaku.htm

Tuckerfan
2003-Jun-07, 09:06 PM
Have I?

http://www.animatedsoftware.com/cassini/mk9707fl.htm http://www.animatedsoftware.com/cassini/mk9708so.htm
http://www.animatedsoftware.com/cassini/kg9328jp.htm
(warning- that is the anti-nukyular Stop Cassini anarchist website)

http://southmovement.alphalink.com.au/antiwar/kaku.htmThanks. I've e-mailed him the links, it'll be interesting to see what his reaction is.

Glom
2003-Jun-07, 09:54 PM
I'm sorry. I don't have the stomach to look at them right now.

BigJim
2003-Jun-07, 10:27 PM
Don't upset it, Glom. Never even think about going to that website. There was a hilarious conversation on the NuclearSpace message board (have you considered joining it? I might) with anti-Cassini and anti-nukyular moron that I read a few weeks ago, but unfortunately upon checking it for the link they announced that now to read or post you need to register and be approved, blah blah blah. The wrong way to run a bulletin board on a website whose purpose is to educate people on the topic of nuclear power.

Tuckerfan, a simple search with the terms "Michio Kaku stop Cassini" will turn up hundreds of links, all that you would ever want.

Glom
2003-Jun-07, 10:35 PM
Thanks for the warning. Can you describe what that conversation was about?

BigJim
2003-Jun-07, 11:01 PM
I don't remember a huge amount of it - that is one of the reasons why I will subscribe there - I want to read it again. Even if you don't feel like posting there, just register to read the conversation. Yes, it's that funny. Basically, one of the site members had e-mailed a "Stop Cassini" anti-nukyular activist, and he got trememndously funny replies. They were debunked, JayUtah style, and the Stop Cassini moron then resorted to insults and profanity. I remember one message which the pro-Cassini person sent to the anti-Cassini which essentially said, "I haven't used any profanity, please stop using it, let's keep this conversation clean." The reply was full of, well, certain words which should not have been used. Register to read it. It'll be worth it.

BigJim
2003-Jun-08, 01:07 AM
Disregard my last post - the NuclearSpace bulletin board has been reopened to everbody! Read the conversation here. (http://pub97.ezboard.com/fnuclearspacefrm5.showMessage?topicID=50.topic)

wedgebert
2003-Jun-08, 02:39 AM
Disregard my last post - the NuclearSpace bulletin board has been reopened to everbody! Read the conversation here. (http://www.neopets.com/browseshop.phtml?owner=nasa_girl24)

Why am I playing Neopets now?

Glom
2003-Jun-08, 11:27 AM
Starting reading one of the threads. Very, very good. I was very concerned, angered, enraged, upset, driven to a homocidal rampage, to learn that the anti-nukyular lobby actually caused us to waste three hundred years worth of nuclear fuel. :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil:

Glom
2003-Jun-08, 11:38 AM
And there are a lot more smileys where those came from.

BigJim
2003-Jun-08, 02:51 PM
Sorry - I don't know how my link broke - I never linked there. Standby.

OK. It's fixed. You can read the conversation now. I now have the correct link.

Glom
2003-Jun-08, 05:52 PM
I was just over at nuclearspace.com and reading some of the threads about school kids in Aberdeen attacking PETA for denying them the right to milk. Also an African group is protesting Greenpeace for attempting to hinder their attempts to get out of poverty.

These anarchist nurks won't be happy until we're living in caves again. But even then, they won't permit us to eat anything and will just allow us to die of the cancer due to exposure to the ionisation radiation coming from the granite walls of our cave.

David Hall
2003-Jun-08, 06:41 PM
Now Glom, don't get too worked up over these guys. Remember, most of them are working from a desire to do good and help the world. The problem is that many of them are short-sighted and don't understand the idea of risk/benefit analysis.

I will also admit that many of them are a bit fanatical about their approach as well. They don't want or know how to go about achieving a balance. They want it all, and can't see how they are actually hurting things with their all-or-nothing approach. It's all black-and-white to them. It's those fanatics who cause the most problems.

wedgebert
2003-Jun-08, 07:05 PM
Now Glom, don't get too worked up over these guys. Remember, most of them are working from a desire to do good and help the world. The problem is that many of them are short-sighted and don't understand the idea of risk/benefit analysis.

I will also admit that many of them are a bit fanatical about their approach as well. They don't want or know how to go about achieving a balance. They want it all, and can't see how they are actually hurting things with their all-or-nothing approach. It's all black-and-white to them. It's those fanatics who cause the most problems.

It don't PETA will be happy until all humans are slaves to animals. I remember when "terrorists" strapped a bomb to a donkey and sent it into Israel or Palastine or somewhere. Well PETA wrote a letter to whatever side sent the bomb protesting the use of the donkey.

Everytime PETA protests something, I make it a point to go buy a honey baked ham. I like ham.

Glom
2003-Jun-08, 07:36 PM
Suicide donkeys? What an original concept.

David, I understand what you're saying. I was sent into a homocidal rampage when I read a thread at the forum at nuclearspace.com.


What of nuclear wastes? Here as elsewhere, one has to unlearn what one has been told. When the uranium in a nuclear fuel rod has been spent, it remains radioactive, and is immersed in pools of cooling water for a few months to allow the short-lived radioactivity to go down. The spent rods are shipped in sealed casks to fuel reprocessing facilities, which separate out the uranium and plutonium. There is no physical problem with all this - a reprocessing center can handle many tons of fuel per day. The problem in the United States has been not physical but political. The Carter administration was filled with people who wanted us to perform miracles and go solar immediately. They hindered offshore
oil drilling and, to vanquish nuclear power, prohibited further recycling of nuclear residues. As a result, these residues-which today constitute a 300-year source for our nation's electricity needs - started to accumulate at power plants. The anti-nuclear lobby, which caused this accumulation in the first place, now claims that these "wastes" are a main reason why we should shut the plants down. When sealed and packaged to U.S. specifications, this material is not dangerous - it is far safer than open wastes from oil or coal.

This was extremely outraging. The anti-nukyular camp are almost conspiracist in their logic. Our development of space technology has been hindered by these naysayers, who are possessed of irrational fears and refuse to have their misconceptions corrected.

David Hall
2003-Jun-08, 08:02 PM
Suicide donkeys? What an original concept.

David, I understand what you're saying. I was sent into a homocidal rampage when I read a thread at the forum at nuclearspace.com.

(snip)

This was extremely outraging. The anti-nukyular camp are almost conspiracist in their logic. Our development of space technology has been hindered by these naysayers, who are possessed of irrational fears and refuse to have their misconceptions corrected.

I fully agree. In fact, I almost added something in my last post about the conspiracist nature of some of them. It is indeed very maddening. I'm as upset as you over how we've been held back by the closed-minded.

There are probably only a few real nuts causing most of the trouble. The majority are just ignorant followers who have been hoodwinked and whipped into a frenzy by these fanatics. They would probably understand if they had some real education about the matter. But then again, things like nukular power are rather complicated concepts for the average person to understand.

Wedgebert, I've heard about the PETA donkey thing, as well as other idiotic stuff they've put out recently such as wanting to change the name of the Green Bay Packers (because meat packing is bad, you know). :roll: While I actually have a lot of sympathy for animal rights (I do volunteer work occasionally at an animal shelter here), I think PETA has been taken over by the worst kind of liberal vegan fanatic type and have lost their sense of reality. Once again, it's the few who are ruining the thing for more rational-minded folk.

wedgebert
2003-Jun-08, 08:23 PM
Wedgebert, I've heard about the PETA donkey thing, as well as other idiotic stuff they've put out recently such as wanting to change the name of the Green Bay Packers (because meat packing is bad, you know). While I actually have a lot of sympathy for animal rights (I do volunteer work occasionally at an animal shelter here), I think PETA has been taken over by the worst kind of liberal vegan fanatic type and have lost their sense of reality. Once again, it's the few who are ruining the thing for more rational-minded folk.

mmmm Ham

BigJim
2003-Jun-09, 02:18 AM
In relation to what David Hall and Glom said:

You have to understand the mindset of the anti-nukyular activist. To them, nuclear power is black and white: anything nukyular is bad, no matter what the frack you tell them. They are similar to the moon hoaxists, only in this case they see nukyular power instead of NASA as absolute evil to oppose no matter what the facts. THe book The Great Nuclear Power Debate really convinced me that nuclear power is the way to go. If you like nuclear power, be sure to pick it up at your library. It's a quick, fun read, but it is also true.

The anti-nukyular power activists don't care that coal plants are more radioactive than nuclear ones; that the Capitol bulding is more radioactive than a nuclear plant is legally allowed to be; that the only proven deaths from nuclear power were at the poorly designed Chernobyl plant, but it is a proven fact that over 50 people a day die from the pollution caused bu coal and oil plants. They don't care that the heating power of a gram of uranium is similar to that of something like ten million tons of coal, that coal mining causes thousands of deaths, or that coal power plants require trainloads of fuel a day, and that nuclear power plants need a few truckloads per year. They also fail to realize the advantages of NTRs or NEPs, explained in the article I linked to a while ago, and that Yucca Mountain will cost $58 billion, mostly due to them (note that this is approximately three times the cost of a manned Mars mission).

Basically, if I wanted to stay safe from radiation, I would replace all coal plants with nuclear ones.

Of course, you also have to understand that the anti-nukyular activists think that nuclear plants can explode like bombs. :roll:

wedgebert
2003-Jun-09, 02:28 AM
This is what happens when people learn just enough information to become dangerous.

They read that nuclear fission generates radiation when in opertion. They don't learn that they also have a lot of shielding designed to stop the radiation for irradiating everyone who works there.

Look at it this way, think of how much the company would lose in health insurance if every employee developed cancer. That's not good for turnover either.

And a nuclear plant, COULD explode like a bomb. If you somehow trapped all the water inside, it could conceivable build up enough pressure to explode. Last time I checked though, we don't drop steam-powered bombs because it's not all that powerful. Someone might have to replace a valve or something...

BigJim
2003-Jun-09, 02:33 AM
But that would be a steam explosion, not a nuclear one. There would not be a fission-bomb type explosion. I am not sure if the containment structure could withstand such an explosion, but I think it could. But the chances of such an explosion happening are almost zero. A pipe or something would burst. We're also assuming that the fuel rods cannot be dropped in.

Glom
2003-Jun-09, 11:47 AM
Oil power is such a waste as well. Oil is too valuable to just be burnt. They should use it to make plastics and things. Oil for plastics, fissile material for power.

It is frightening see such a waste of precious resources. I am genuinly in fear for our future thanks to these anarchist nurks. The ironic thing is that they go on talking about protecting the environment and then they advocate the most damaging thing of all: wasting resources.

BigJim
2003-Jun-09, 10:29 PM
This is what aggravates me about them.

I would like to ask (maybe I will e-mail) an anti-nuclear power environmentalist some questions.

They say they are interested in saving power and human lives. That's fine. Then we should go nuclear. First off, it is undisputed fact that coal and oil plants cause more deaths from pollution than nuclear plants ever have. Second, it is fact that coal plants release more radiation than nuclear plants. Third, fossil fuels will soon run out.

So why would you want to declare nuclear power off-limits? That is, if I may say so, just plain nuts. That means that we run fossil fuel plants to exhaustion, and then what do we have (large scale)? Solar and wind. That's it. I believe I remember reading somewhere that 13 square miles of solar panels would be comparable to the power output from a single nuclear reactor, taking up about 400 acres. 13 square miles. That's preposterous. To produce the amount of power that we use today from strictly solar and wind, the generators would have to cover much of the Earth. This would exacerbate, not alleviate, the problem of overpopulation. And, it would cost a tremendous amount of money. With nuclear, we have at least several hundred to thousands of years of clean, safe power available. If properly built, nuclear plants are extremely safe. (Chernobyl was poorly designed; At Three Mile Island the extensive safeguards at the plant prevented any proven injuries from occuring.) Nuclear power is our only large scale power option once fossil fuels run out, and it also happens to be clean and safe.

But let's say we developed a magical fossil fuel saving machine that will give us 500 more years of fossil fuels. Even then, it would be ridiculous not to go nuclear. Spaceflight would be crippled. To mine helium-3 from Luna, we need nuclear power to power our equipment; to mine it from the outer solar system, we need NEP. Nuclear power is the only viable power option for the next 100 years of serious space exploration. Solar panels do not provide enough and only work well in the inner solar system; fuel cells would be too large; batteries are not efficient enough or long-lasting enough. Fossil fuels only exist on Earth. The only viable alternative for solar system colonization is nuclear fission, until we get helium-3 (and to get that, we need fission). When bulit properly, a nuclear fission reactor can operate extremely safely, and the only pollution it creates is heat. Nuclear fission reactors are the only logical solution. Especially for a Mars human exploration mission this holds true; with a nuclear reactor, such a mission could make from 10 to 100 times as much power as a similarly designed mission with solar or fuel cell power; the advantages of nuclear would also allow in-situ propellant production and power for high-energy experiments such as radar and microwaves for getting water from the Martian regolith. The data rates would be so much higher that not using a reactor would be simply ridiculous.

Without nuclear power, the future of humankind is uncertain. Will we have the power to colonize space and meet our future needs? I think not. Nuclear power is the solution to our power needs of the near future.

wedgebert
2003-Jun-09, 11:44 PM
I agree with most of that, except the part about needing fission to get Helium-3.

The Moon contains enough He3 to power our world for centuries, so conceivablely we could skip fission power altogether.

However, since reliable fusion technology is most likely decades away, it doesn't make sense to wait that long so I say we should do two things.

1: Ignore the naysayers and go ahead and start using nuclear power for space flight, both for power generation and propulsion.

2: Establish a lunar colony and start stockpiling helium-3 ahead of time. No point waiting until we need it. I'd rather spend some money now and have a few years worth stockpiled than have the technology but only enough fuel to send occasional probes.

Plus, I'm sure that having an useable supply of the stuff would make research a lot easier. Currenty the US supply of He3 is only a few liters. If we had a few tons of the stuff, it would be more accessable to researchers.

BigJim
2003-Jun-09, 11:56 PM
I agree with most of that, except the part about needing fission to get Helium-3.

The Moon contains enough He3 to power our world for centuries, so conceivablely we could skip fission power altogether.


I know that, but there is a catch. To get the helium-3, you need to mine it, which would require a small system of bulldozers, trucks, ovens, and convyor belts - and guess what would power them. My point is, once you have the helium-3, it can be used as our primary energy source, but first you have to get the helium-3, and the power needed to get the helium-3 requires fission.

But I do agree that helium-3 will become the energy source for all of our needs, including spacecraft and power generation. Even helium-3 tankers will be powered by helium-3 engines.


2: Establish a lunar colony and start stockpiling helium-3 ahead of time. No point waiting until we need it. I'd rather spend some money now and have a few years worth stockpiled than have the technology but only enough fuel to send occasional probes.

If there's no market, the cost of mining the helium-3 would be so high as to be unrealistic. Be patient. Once we have the demand, no one will care what the environmentalists say; they want their power, they get it.

daver
2003-Jun-10, 12:42 AM
Re: Solar power figures

Well, here in California we get an average of 5-6 kWh of sunlight per square meter per day. Assuming (1) 10% efficient solar cells, (2) 6 kWh of insolation, (3) 100% efficient ridiculously high capacity batteries (don't laugh so hard, you'll pull something), you get 25 watts/square meter. One gigawatt would need 40,000,000 square meters, or 40 square kilometers. Plus, of course, the space needed for the batteries. If the solar plant was just being used for daytime peak power you might be able to get a gigawatt out of only 15 square kilometers.

I have no idea what the environmentalists want us to do about the base load. Wind is obviously unsuitable for more than a few percent of it. I suppose they want us to live like my grandparents used to--electricity for a few hours a day, biofuels for the rest.

Tuckerfan
2003-Jun-10, 02:55 AM
Re: Solar power figures

Well, here in California we get an average of 5-6 kWh of sunlight per square meter per day. Assuming (1) 10% efficient solar cells, (2) 6 kWh of insolation, (3) 100% efficient ridiculously high capacity batteries (don't laugh so hard, you'll pull something), you get 25 watts/square meter. One gigawatt would need 40,000,000 square meters, or 40 square kilometers. Plus, of course, the space needed for the batteries. If the solar plant was just being used for daytime peak power you might be able to get a gigawatt out of only 15 square kilometers.

I have no idea what the environmentalists want us to do about the base load. Wind is obviously unsuitable for more than a few percent of it. I suppose they want us to live like my grandparents used to--electricity for a few hours a day, biofuels for the rest.Well, if Bush hadn't killed this (http://www.energylan.sandia.gov/sunlab/faqs.htm) project, solar power might be a lot more viable.

Glom
2003-Jun-10, 03:38 PM
I have no idea what the environmentalists want us to do about the base load. Wind is obviously unsuitable for more than a few percent of it. I suppose they want us to live like my grandparents used to--electricity for a few hours a day, biofuels for the rest.

As I said here (http://www.badastronomy.com/phpBB/viewtopic.php?p=98907#98907).

FREEDOM FOR FISSION

crazy4space
2003-Jun-10, 04:55 PM
[quote="BigJim"] Third, fossil fuels will soon run out.

This is a good question - I have often had this argument regarding wheather fossile fules are finite or renewable?

What is Helium-3 ?

daver
2003-Jun-10, 05:48 PM
Well, if Bush hadn't killed this (http://www.energylan.sandia.gov/sunlab/faqs.htm) project, solar power might be a lot more viable.

There was a "solar" power plant, built using solar power subsidies, with a natural gas backup generator. The plant ended up only selling electricity from the natural gas generator (the solar part was essentially a boondoggle). I'm not sure that the site your link refers to was the plant i was describing or not. If so, Bush did the right thing in shutting it down. Pilot plants to try to improve the economics are fine, alleged production plants that just use the solar power subsidy to build a fossil fuel plant are a crock.

daver
2003-Jun-10, 05:53 PM
[quote=BigJim] Third, fossil fuels will soon run out.

This is a good question - I have often had this argument regarding wheather fossile fules are finite or renewable?

What is Helium-3 ?

That's been discussed quite a bit the past few months--you might try doing a site search. He3 is a fuel for fusion that produces no neutrons when it undergoes fusion. As such, it is inherently clean. Unfortunately, He3 is hard to find--there is some on the moon, there is quite a bit in Jupiter's atmosphere, or it can be made by bombarding other stuff with neutrons.

BigJim
2003-Jun-11, 02:41 AM
What is Helium-3 ?

There are two main kinds of thermonuclear fusion that we could achieve. One, which is what we are experimenting with now and which we occasionally use in thermonuclear bombs, is deuterium-tritium fusion. Deuterium, a hydrogen atom with a neutron, and tritium, a hydrogen atom with two neutrons, are the easiest atoms to fuse. Deuterium tritium or D-T fission creates a helium-4 atom and a neutron, as well as 17.6 million million electron volts (MeV), about ten million times the energy burning coal releases.

The helium-4 nucleus created, also known as an alpha ray, is a charged particle, and the magnetic field of a tokamak confines it in the magnetic field, and as it collides with surrounding deuterium and tritium it heats the plasma. However, the neutron is uncharged and collides with the wall of the tokamak. Some of the neutrons will collide with a lithium blanket, creating more tritium, and the heated walls could turn a generator, but eventually the wall of the tokamak would need to be replaced.

The other kind of fusion, D-He3 or deuterium-helium 3 fusion, creates 18 MeV of energy, one hydrogen nucleus, one helium-4 nucleus, and no neutrons. So, clearly, this type of fusion is preferable as it creates more energy and does not require the costly and dangerous replacement of radioactive walls. However, D-He3 fusion is harder to start than D-T fusion. The larger problem with D-He3 fusion, though, is that helium-3 does not exist on Earth. The solar wind has put it into lunar soil with about 4 ppb on average. While not much per unit of soil, over the whole moon this is more energy than all the fossil fuels on Earth. This is a reason for spaceflight and lunar colonization.

The reason neither D-T nor D-He3 reactors currently exist is that the reaction needs to produce energy at a rate equal to the power being using externally to heat the plasma. This condition is called "breakeven" and was first reached in 1997. The next step, called ignition, requires about 4 times more energy but can heat itself, and is the last remaining barrier to nuclear fusion plants.

Once this technology becomes available, though, it will by FAR be better than other power forms. It produces no pollution, cannot melt down, creates far more energy than any other natural source, and it should be fairly simple to build the facilities once the technology is acquired.

crazy4space
2003-Jun-11, 10:42 PM
[quote]What is Helium-3 ?

There are two main kinds of thermonuclear fusion that we could achieve. One, which is what we are experimenting with now and which we occasionally use in thermonuclear bombs, is deuterium-tritium fusion. Deuterium, a hydrogen atom with a neutron, and tritium, a hydrogen atom with two neutrons, are the easiest atoms to fuse. Deuterium tritium or D-T fission creates a helium-4 atom and a neutron, as well as 17.6 million million electron volts (MeV), about ten million times the energy burning coal releases.

I think I saw something like this in Popular Science - they were taking lasers and pointing them at a Deuterium pellet and trying to get fusion. From what I remember all they could muster was a few microseconds. My question is once you achieve fusion how do you contain it? An electro magnetic field?

wedgebert
2003-Jun-12, 12:09 AM
I think I saw something like this in Popular Science - they were taking lasers and pointing them at a Deuterium pellet and trying to get fusion. From what I remember all they could muster was a few microseconds. My question is once you achieve fusion how do you contain it? An electro magnetic field?

Yes, when you reach the temperatures needed for fusion to ignite, all your matter has turned into plasma. Plamsa is matter that has had the electrons stripped from them. Thus plamsa has a charge and can be contained by electro-magnetic fields.


The other kind of fusion, D-He3 or deuterium-helium 3 fusion, creates 18 MeV of energy, one hydrogen nucleus, one helium-4 nucleus, and no neutrons. So, clearly, this type of fusion is preferable as it creates more energy and does not require the costly and dangerous replacement of radioactive walls.

You're forgetting Deutrium - Deuterium fusion. It's nowhere near as powerful as D-T fusion, but has a few advantages. First off the fuision fuels are common. Tritium is radioactive and thus we have no source for it. Deuterium makes up a small portion of the hydrogen in water. It's said that one gallon of water has enough deutrium to provide the same energy as 300 gallons of gasoline.

D-D fusion can actually undergo two different reactions. The first is
D + D -> He3 + neutron + 3.3 MeV.
The second is
D + D -> T + H + 4.03 MeV

Pretty low compared to

D + T -> He + 17.6 MeV

and worse compared to

D + He3 -> He + H + 18.3 MeV

But notice two things. First is thatthe first two reactions produce the necessary fuels for the last two. Second is that the free neutron produced in the first D-D reaction has a use. Namely that of turning Lithium into

Li + Neutron -> He + T + 4.8 MeV

Basically you surround the D-D reaction with Lithium as a coolant and radiation shield, it absorbs the neutrons and decays into Tritium and Helium.


Finally my last point that I've been building to, which is that, unfortunatly, D-He fusion isn't all it's cracked up to be.

The ignition point for D-He3 is higher than that of D-D, so some of the Deuterium is going to fuse with other Deuterium and so there will be some radiation, but nowhere near as much as a normal D-D or D-T

BigJim
2003-Jun-12, 12:42 AM
Finally my last point that I've been building to, which is that, unfortunatly, D-He fusion isn't all it's cracked up to be.

You're exaggerating the point. True, it does produce some radiation in the form of energetic neutrons, but very, very little, and it does produce a huge amount of energy.


D-D fusion can actually undergo two different reactions.

What governs which one occurs?




D + D -> He3 + neutron + 3.3 MeV.
The second is
D + D -> T + H + 4.03 MeV

D-D fusion is useful in that it can create fuel for D-He3 and D-T reactors, but is comparatively dirty and low-powered. It's easier to get He3 from the outer solar system or the Moon because, first, you need the detuerium for the helium-3 reactors, and second, the neutrons will cause the reactor wall to decay and become radioactive. The second reaction is good, but nowhere near as good as D-T - it produces far lesss energy, as you pointed out. But D-He3 is the most powerful and creates no neutrons. Still, D-D fusion may actually end up being the first generation of operational nuclear fusion reactors, because they are still cleaner and more powerful than nuclear fission.

wedgebert
2003-Jun-12, 02:39 AM
Don't get me wrong, I'm a big proponent of D-He3 fusion, and the necessary lunar colony. If you check a few posts eariler, I was probably the one who brought it up (I try to get a pro-lunar colony post in as often as I can :)

I was just wanted to play devils advocate and point that He-3 isn't as clean as some people (including myself) let on.

I did a little (very little :) fact finding, and according to an article at www.space.com (hhttp://www.space.com/scienceastronomy/helium3_000630.html), Deuterium + Helium-3 fusion produces about 1% of the radiation as D-T fusion (which supposedly releases 80% of it's energy as neutrons).

ToSeek
2003-Jun-12, 03:36 AM
Nukes to the moons of Jupiter (http://www.lockheedmartin.com/news/articles/061003_2.html)

wedgebert
2003-Jun-12, 09:35 PM
I've got an idea.

Let's build an unmanned pulsed fission test probe. Basically it'll just hold enough nuclear bombs to propel the probe into orbit. Of course these'll be pretty small bombs. Since there's no equipment or people on board, we don't need as much radiation shielding so the PulFis can impart enough acceleration to get the probe into orbit.

Then we'll get all the anti-nuklear folks together at the launch site. We'll tell them that we've developed a new nuclear propulsion, that although is a little radioactive, is very efficient. This should draw them like flies.

Then when they're near enough to the probe, we'll evacuate the important people away or have them hid in specially designed (and hidden) bunkers.

Then we'll press the button and blow all the onboard nuclear weapons at once, and rid ourselves of a large portion of the protesters.

Finally, we'll have some pre-filmed footage that "shows" some protesters "sabotaging" the probe and say that's what caused the explosion. Maybe we can blame PETA in some way too.

pmcolt
2003-Jun-12, 09:40 PM
Then when they're near enough to the probe, we'll evacuate the important people away or have them hid in specially designed (and hidden) bunkers.

I for one am shocked! Shame on you, wedgebert, for suggesting such an awful, heinous course of action. Throwing away a perfectly good opportunity to study a new nuclear propulsion system... :wink:

wedgebert
2003-Jun-13, 05:07 AM
Well, that's why I chose pulsed fission. Not much to study, shove bombs out the back and ride the shockwaves. Plus it makes a convient way to "accidently" rid ourselves of the annoying protesters. :)

I still think we should say there's a monkey onboard so PETA shows up as well. Kill two birds with one stone.

Glom
2003-Jun-24, 01:30 PM
FREEDOM FOR FISSION

Just thought I'd say that.

BigJim
2003-Jun-24, 03:17 PM
What do you do when people don't believe the facts because, well, they don't want to? I've experienced this with lunar conspiracists, and now with people against nuclear power.

I was having a discussion with some people I know about power sources, and they made a statement to the effect of, "I'd be happy with any power except for nuclear power." Now of course I would not let such a statement go unchallenged, but a lot of the facts I stated they simply refused to believe (i.e. coal plants release more radiation than nuclear plants, Chernobyl was poorly designed and had none of the safeguards of American plants, no one was proven to be hurt from TMI, etc.) Since they did not seem willing to believe my facts, I asked them what they disliked about nuclear power, and then they changed the subject. :-?

To add to my discomfort, I was at the library yesterday, where they have several shelves replete with anti-nukyular books. But pro-nuclear books? Not one. :-?

Maybe we should write a book. Anybody who knows something about nuclear power supports it. I have not found one person yet who is both against nuclear power and knows how it works, what radiation is, what safeguards are bulit into nuclear plants, what actually happened at TMI or Chernobyl, or the advantages of nuclear versus coal or solar.

Glom
2003-Jun-24, 04:05 PM
For fifty years, the general population has been subjected to the propoganda of the media, doomsayers and fear mongerers. It is disgusting.

daver
2003-Jun-24, 08:52 PM
I was having a discussion with some people I know about power sources, and they made a statement to the effect of, "I'd be happy with any power except for nuclear power."

I was watching some anime over the weekend--Giant Robo. 10 years before the story takes place, scientists had invented what appears to be the perfect power source--small, portable, non-polluting. Now everything, from airplanes to street lights to cigarette lighters, runs off of that power source. Nuclear power is treated with fear and loathing (it turns out that the eponymous Giant Robo is nuclear powered, but that's a secret). An accident occurred during the development of this new power source that killed one third of the population of the planet. Three billion people--poof. And the writers thought that the remaining population would still prefer this power source to nuclear, and still regard nuclear as unsafe. Bizarre.

BigJim
2003-Jul-19, 08:09 PM
This thread seems to have died, but I'm going to try to start it up again with a suggestion. Why don't we invite one of the "Stop Cassini" fools here? It would be hilariously entertaining.

Glom
2003-Jul-19, 09:18 PM
We can't let this thread die. It's a great forum for our rants.

A Stop-Cassini protestor could be interesting.

I suggest we set up a 'Freedom for Fission' movement. Of course, I don't know what we'd do, but it sounds like a good idea.

BigJim
2003-Jul-19, 09:26 PM
I agree with all three of your points. Who shall we invite and who shall do the invitation? I nominate the owner of this site (http://animatedsoftware.com/cassini/), the worst anti-Cassini site. He can be reached at rhoffman@animatedsoftware.com . Who shall do the honors? I doubt he'll listen anyway - most of these people are terrified of facts.

Glom
2003-Jul-19, 09:35 PM
Yet another site dedicated to fear-mongering and doom-saying and allowing ignorance to generate mass hysteria that will prevent progress and the improvement of quality of life!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!

](*,) ](*,)

BigJim
2003-Jul-19, 09:36 PM
Exactly. So should we invite him?

Glom
2003-Jul-19, 09:38 PM
:-({|=

BigJim
2003-Jul-19, 09:53 PM
Very well. I'll keep you posted. Here the message I will send to him:


I would like to bring up a few points about your website. Actually, more than a few. Almost all of the conclusions on it are factually incorrect or extremely exaggerated in one way or another. If you are willing to defend your conclusions, I would like to invite you to take part in the discussion that is taking place at http://www.badastronomy.com/phpBB/viewtopic.php?t=4600&postdays=0&postorder=asc&star t=0 . We are prepared to debate you. Are you willing to take part in a scientific debate about your views, or will you shy away like so many others have? Let us know.

Do you think that will do the trick? Suggested changes?

Glom
2003-Jul-19, 09:57 PM
:-({|=

BigJim
2003-Jul-19, 10:03 PM
Also, don't recommend him to this thread as we've already used terms like Stop Cassini Wackos and threatened to use environmentalists in NTRs.

Is there something wrong with that? \:D/ (Interesting emoticon that I had to use)

We probably wouldn't want to anyway because we are discussing, well, inviting him.

So how would you change it? Post your edited version.

ToSeek
2004-Feb-18, 06:03 PM
NASA’s Nuclear Focus Aimed At 2009 Mars Lander (http://www.space.com/businesstechnology/technology/nuclear_focus_040218-1.html)

Also talks about nuclear propulsion.

Sirius
2004-Feb-19, 03:08 AM
Ok, I havn't read the whole discussion, but:

Unless I have read from a bad source (can't remember where I read it), The two Voyagers are nuclear powered.

russ_watters
2004-Feb-19, 07:31 AM
Ok, I havn't read the whole discussion, but:

Unless I have read from a bad source (can't remember where I read it), The two Voyagers are nuclear powered. We have sent out a number of probes with nuclear power, but none with nuclear propulsion.

daver
2004-Feb-19, 05:51 PM
Ok, I havn't read the whole discussion, but:

Unless I have read from a bad source (can't remember where I read it), The two Voyagers are nuclear powered. We have sent out a number of probes with nuclear power, but none with nuclear propulsion.
The 2009 Mars Lander is still RTG; one of the proposals is a Stirling cycle, which would roughly double the efficiency. Both RTG proposals are higher power than previous designs (I believe). Anyway, Sirius is right; we've been using RTGs in space probes and landers for decades.

It looks as if the 2009 Mars Lander is still using chemical propulsion. The proposed JIMO probe would use a full-fledged nuclear reactor for propulsion and for science once it arrived.

Sirius
2004-Feb-19, 06:30 PM
Ok, I havn't read the whole discussion, but:

Unless I have read from a bad source (can't remember where I read it), The two Voyagers are nuclear powered. We have sent out a number of probes with nuclear power, but none with nuclear propulsion.

Ok... Cool!

ToSeek
2004-Mar-18, 07:17 PM
NASA Partners With Department of Energy for Space Exploration (http://www.spaceref.com/news/viewpr.html?pid=13860)


The Department of Energy's (DOE) Naval Reactors (NR) Program joins NASA in its effort to investigate and develop space nuclear power and propulsion technologies for civilian applications. These activities could enable unprecedented space exploration missions and scientific return unachievable with current technology.

Kevinito
2004-Mar-18, 08:12 PM
Did not Cassini have nuclear power as a power source? I do recall tests done here in Florida if there were a catastrophe (I do recall something about graphite plates).

-Kevin

Hamlet
2004-Mar-18, 08:19 PM
Did not Cassini have nuclear power as a power source? I do recall tests done here in Florida if there were a catastrophe (I do recall something about graphite plates).

-Kevin

Cassini uses 3 Radioisotope Thermoelectric Generators (RTG's) for its power source. They are not reactors but instead use the heat from the radioactive decay of plutonium-238 to generate electricity.

Here's (http://www2.jpl.nasa.gov/galileo/messenger/oldmess/RTGs.html) a link to an explanation of RTG's.

Glom
2004-Mar-18, 08:19 PM
Cassini was powered by a radioisotopic thermoelectric generator, which uses the heat produced by the nuclear decay of a plutonium dioxide rod to generate electricity.

sts60
2004-Mar-18, 08:36 PM
Cassini uses three of the GPHS (General Purpose Heat Source)-RTGs, averaging about 295W electrical power apiece. Nearly 900 W of juice! By comparison, the first radioisotope-powered U.S. satellite, Transit 4A (1961), ran off 2.7W from its SNAP-3B7 generator.

Galileo and Ulysses each used the same kind of RTG as Cassini (2 for Galileo, 1 for Ulysses). The Pluto New Horizons probe will also use the GPHS-RTG.

Cassini also carries 117 Lightweight Radioisotope Heater Units (LWRHUs) to heat the spacecraft. They are tiny; each one gives off about 1W of heat initially.

Edited to add: In the field, "nuclear" usually refers to reactors; "radioisotope" generally refers to devices which just have a chunk of PuO2 quietly decaying away (whether for heat or for direct/static or dynamic conversion to electricity).

Kaptain K
2004-Mar-19, 12:35 AM
The Pluto New Horizons probe will also use the GPHS-RTG.
Assuming it ever flies! :evil:

ToSeek
2004-Mar-19, 01:24 AM
The Pluto New Horizons probe will also use the GPHS-RTG.
Assuming it ever flies! :evil:

APL is still plugging away at it. (http://pluto.jhuapl.edu/)

ToSeek
2004-Mar-30, 05:05 PM
Problems with nuclear-powered propulsion: The Myth of Low-Thrust Propulsion (http://www.spacedaily.com/news/nuclearspace-04d.html)

daver
2004-Mar-30, 10:09 PM
Problems with nuclear-powered propulsion: The Myth of Low-Thrust Propulsion (http://www.spacedaily.com/news/nuclearspace-04d.html)

Which makes me wonder a bit about VASIMR. The product of Isp and thrust is proportional to the power requirements of the reactor; a 1000 ton spacecraft accelerating at 1 m/sec**2 with an exhaust velocity of 10 km/sec needs about a 5 GWe reactor. You need about 3.7 km/sec to launch from LEO to a Mars transfer orbit, and about 2.2 km/sec to brake from Mars transfer into LMO. Doubling that (round trip) gives a total delta V of about 11.8 km/sec (I should round up to 12, but I'm taking the log in the next step).

I need to munge the rocket equation a bit (assume a constant g, so the Isp continually increases). However, if you pretend that you're doing this with a 10 km/sec delta V then your mass ratio works out to be about 2.7; actually you should be able to do a bit better than this). Regardless, I don't think it very likely that you could fit a 5 GWe reactor and its cooling system into a c~ 300 ton spacecraft.

So you end up with primarily chemical propulsion, with maybe a slight kick from VASIMR to knock a month or two off your trip. All in all, the high thrust nuclear options look a lot more reasonable.

[edit--I knew I was off by a factor of 1000 but couldn't find it. Now I found it--i was converting km/sec to m/sec twice. Anyway, gigawatt reactor, not terawatt reactor]

Avatar28
2004-Mar-30, 11:14 PM
But isn't that part of the beauty of VASIMR that it can do either high thrust, low ISP (though still better than chemical I believe) or low thrust, high ISP or somewhere in between if desired.

daver
2004-Mar-31, 01:05 AM
But isn't that part of the beauty of VASIMR that it can do either high thrust, low ISP (though still better than chemical I believe) or low thrust, high ISP or somewhere in between if desired.
But the problem seems to be that for most manned applications chemicals work better--VASIMR's high thrust mode isn't near high enough. You end up with a chemical (or NTR) rocket for the initial push out of Earth orbit and for braking into your destination orbit--if you have any spare kilowatts you can use them for a bit of extra push, but it's not going to shave much off of your trip time.

You can go with some sort of hybrid scheme, where you use VASIMR or some other low thrust scheme to push a cycler into a Mars transfer orbit (over a period of maybe a decade); you then use chemical rockets to transfer your crew to the cycler. Because of the slow acceleration of the cycler, you end up requiring perhaps 6 km/sec delta V to go from LEO to mars transfer orbit, as opposed to maybe 3.7 for a chemical rocket. Chemical propulsion yields a mass ratio of around 2.6, whereas an Isp of 1000 would yield a mass ratio of around 1.8 and an Isp of 3000 a ratio of around 1.2.

daver
2004-Mar-31, 07:47 PM
I continued wondering last night about VASIMR and applications.

As you may remember from our last episode, I figured we'd need a reactor in the gigawatt range in order to get a decent acceleration for a Mars mission. As it happens, it would only need this acceleration in relatively short bursts--maybe an hour or so while accelerating into or braking out of the transfer orbits. During the rest of the mission, the reactor could be operated in a much lower-power mode (maybe hundreds of kWe--a bit higher if VASIMR were to be used in its high Isp mode to chop a bit more time off the transfer).

From what little I know of nuclear reactors, one of the problems is cooling. Reactors are extremely inefficient at producing electricity, and produce a lot of waste heat which must be dispersed somehow. This problem is even worse in space, where there's no convenient atmosphere or river to dump the waste heat into--instead, the heat must be radiated away. What I was wondering was whether it would be possible to produce a dual-mode reactor. During its low power mode, it would be cooled by the huge radiator array you see on the JIMO drawings, while during its high power mode it would be cooled by allowing a stream of hydrogen gas to play on the reactor directly, and then exhausting the hot hydrogen gas. Now, of course there's no particular reason why this exhaust gas can't be encouraged to all leave by the same exit, giving you a nice little nuclear thermal rocket. My guess is that the exhaust jet from this rocket would generate more thrust than VASIMR.

So, does anyone know whether it is possible to build a dual-mode reactor--one capable of operating at relatively low power levels (< 1 MW) for long periods of time that can be coerced to run at ridiculously high power levels (GW) for perhaps one-hour bursts?

ToSeek
2004-Mar-31, 08:52 PM
More about JIMO: NASA plans to send nuclear electric powered robot to Jupiter (http://www.spacedaily.com/news/nuclearspace-04e.html)

ToSeek
2004-May-03, 04:18 PM
Benefits of nuclear power: Project Prometheus May Bring Wider Use of Radar Imaging (http://www.space.com/spacenews/businessmonday_040503.html) - more power means more and better science instruments.

eburacum45
2004-May-04, 10:01 AM
Daver'shybrid VASIMR/nuclear thermal system sounds very promising; but I am looking at using propellants found easily on the Moon to avoid shipping them up from Earth.
How about ion drives using abundant lunar magnesium?

And if we consider the hydrogen used to cool the reactor and provide additional thermal thrust- hydrogen is not abundant on the Moon, and any found will probably be needed to make water for life support and for manufacturing.
Oxygen is abundant on the moon, combined with other elements of course- we might consider using that as a coolant, but it crosses my mind that a cooling system using hot oxygen to provide thrust would be quickly corroded away.

On the other hand you might get a spectacular fireworks display behind the spacecraft as the magnesium and oxygen recombined...[/i]

Philipum
2005-Feb-23, 09:15 AM
I've got an idea.

Let's build an unmanned pulsed fission test probe. Basically it'll just hold enough nuclear bombs to propel the probe into orbit. Of course these'll be pretty small bombs. Since there's no equipment or people on board, we don't need as much radiation shielding so the PulFis can impart enough acceleration to get the probe into orbit.



I guess this is nothing else than the ORION project which was cancelled in the 1960's because it involves politically unacceptable manufacturing of nuclear bombs. See what humanity might have done if the project had continued:

http://www.nuclearspace.com/gallery_project_orion.htm[/url]

Philipum
2005-Feb-23, 09:21 AM
What is Helium-3 ?

The reason neither D-T nor D-He3 reactors currently exist is that the reaction needs to produce energy at a rate equal to the power being using externally to heat the plasma. This condition is called "breakeven" and was first reached in 1997. The next step, called ignition, requires about 4 times more energy but can heat itself, and is the last remaining barrier to nuclear fusion plants.

Once this technology becomes available, though, it will by FAR be better than other power forms. It produces no pollution, cannot melt down, creates far more energy than any other natural source, and it should be fairly simple to build the facilities once the technology is acquired.

I am curious about one thing concerning D-He3 fusion.
If it does not emit neutrons, how do you recover the energy which is released in the reaction?
How do you cool your plasma by the way? My first guess would be that the reactor would quickly overheat.

Philipum
2005-Feb-23, 09:25 AM
Maybe we should write a book. Anybody who knows something about nuclear power supports it. I have not found one person yet who is both against nuclear power and knows how it works, what radiation is, what safeguards are bulit into nuclear plants, what actually happened at TMI or Chernobyl, or the advantages of nuclear versus coal or solar.

A good book was written in the 1980's:
"Before it's too late: A Scientist's Case for Nuclear Energy" by Brenard L. Cohen.
It would probably convince anyone who reads it, but unfortunately those who need to be convinced would probably not read such a book.

Philipum
2005-Feb-23, 09:38 AM
This is what aggravates me about them.

I would like to ask (maybe I will e-mail) an anti-nuclear power environmentalist some questions.

They say they are interested in saving power and human lives. That's fine. Then we should go nuclear. First off, it is undisputed fact that coal and oil plants cause more deaths from pollution than nuclear plants ever have. Second, it is fact that coal plants release more radiation than nuclear plants. Third, fossil fuels will soon run out.

So why would you want to declare nuclear power off-limits? That is, if I may say so, just plain nuts. That means that we run fossil fuel plants to exhaustion, and then what do we have (large scale)? Solar and wind. That's it.

(...)

Without nuclear power, the future of humankind is uncertain. Will we have the power to colonize space and meet our future needs? I think not. Nuclear power is the solution to our power needs of the near future.

The anti-nuclar activitsts are against coal and oil burning as well! They claim that solar and wind can solve all energy problem, this might be true if we were to stop consuming energy.
I doubt the environmentalists themselves would be ready to abandon some comfort provided by oil in cars and trucks or cheap nuclear electricity, but there IS a point in trying to minimize stupid wastes of energy.

Solar and wind would be the only left? What about hydro, biomass, geothermic? A combination off all these provides substancial energy resources, though not as much and as cheap as if nuclear is also included.

Ilya
2005-Feb-28, 12:37 AM
I have not found one person yet who is both against nuclear power and knows how it works, what radiation is, what safeguards are bulit into nuclear plants, what actually happened at TMI or Chernobyl, or the advantages of nuclear versus coal or solar.

I can think of one exception -- Dr. Michio Kaku, of "Stop Cassini!" fame. I am quite certain he knows all these things, yet is very anti-nuclear. Or at least was -- Kaku is still prolific in popular science publishing, but I had not heard anything from him on that matter in a long time.

I always found it rather entertaining that anti-Cassini activists found exactly ONE physicist to support their claim. Not even two! And I was also mystified as to why he was supporting them. Either he is a shameless publicity hound, or having been born in Japan, he has a visceral loathing of anything nuclear. More likely former, since some of the things he claimed he HAD to know were untrue. It will be interesting to see whether he starts on again with Pluto Express and Prometheus.

Philipum
2005-Feb-28, 08:06 AM
I know another one: Ted Taylor, nuclear fission weapon designer and pioneer in nuclear space technology. Later in his life, he feared the proliferation of nuclear bomb material. He thought we should stop using nuclear power, and presented a talk about "putting back the nuclear genie into the bottle":

http://www.nci.org/new/ib5196.htm

Philipum
2005-Feb-28, 08:41 AM
Actually, I would like to add a few comments on the subject. The problems related to nuclear power, like safety, weapon proliferation, and radioactive waste management, are much more complex than people usually let express. Some people say ncuelar stuff is EXTREMELY dangerous, tother say it is NOT dangerous AT ALL. Even for experts, I think doubt is natural, considering all subjective inputs and the fact that we can't handle all aspects at once. The reality seems to me to lie in between the extremes.

publiusr
2005-Mar-02, 06:59 PM
Space is the only place nuclear material should be. But if you go nuclear-thermal, you need a lot of heavy hydrogen tankage to avoid leaks. JIMO NEP systems are also heavy-weights.

Once again--this all gets back to the need for heavy-lift rockets, for high mass, and large volume--payloads as well. JIMO was to have been 50-80 tons with an upper stage for it to escape before they pull the rods on the thing.