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SkepticJ
2005-Jan-21, 01:43 AM
This old and sadly not getting funding right now because the Advanced Propulsions Concepts isn't getting funding at the moment. Any way, what do you make of it? --> http://science.howstuffworks.com/electromagnetic-propulsion.htm

Andreas
2005-Jan-21, 01:48 AM
From what I gather, this is a reaction-less drive. Won't work.

Kizarvexis
2005-Jan-21, 01:51 PM
From my understanding of the How Stuff Works article, the two biggest problems are as follows.

Can the magnet survive the vibrations? Which seems is much easier to solve than can the magnet be forced to vibrate only in 1 direction?

It seems nice in theory, but I would guess the second part will be the impossible part.

Kizarvexis

Sticks
2005-Jan-21, 02:03 PM
Plus the powers that be will not want you putting a nuclear reactor in space. Remember the protesters against the launch of Cassini - Huygens ?

Nergal
2005-Jan-21, 02:46 PM
(C)an the magnet be forced to vibrate only in 1 direction?

Vibration (http://searchbox.hyperdictionary.com/searchbox.aspx?define=vibration): (emphasis mine)

\Vi*bra"tion\, n. [L. vibratio: cf. F. vibration.]
1. The act of vibrating, or the state of being vibrated, or
in y motion; quick motion to and fro; oscillation,
as of a pendulum or musical string.

2. (Physics) A limited reciprocating motion of a particle of
an elastic body or medium in alternately opposite
directions from its position of equilibrium, when that
equilibrium has been disturbed, as when a stretched cord
or other body produces musical notes, or particles of air
transmit sounds to the ear. The path of the particle may
be in a straight line, in a circular arc, or in any curve
whatever.

By definition, "vibrations" are not uni-directional. Granted, that's a nitpick, as vibration may not be the most applicable term for what is occuring.

I agree though that the real hitch in making this work is finding a way to channel the "vibrations" into something useful.

Eta C
2005-Jan-21, 03:27 PM
I agree with Andreas, this sounds like a reactionless drive, that is one that moves the craft without ejecting propellent. Unfortunately, this sort of thing violates all sorts of conservation laws (not to mention Newton's second and third). Unless these vibrations are used to eject some kind of propellent, this drive will go nowhere.

joema
2005-Jan-21, 03:35 PM
Plus the powers that be will not want you putting a nuclear reactor in space. Remember the protesters against the launch of Cassini - Huygens ? However there have already been 50 launches of nuclear RTGs or actual nuclear reactors into space.

The planned Jupiter Icy Moons Orbiter will use a uranium fission reactor to power ion engines:

http://www.jpl.nasa.gov/jimo/

John Dlugosz
2005-Jan-21, 08:30 PM
Any way, what do you make of it? --> http://science.howstuffworks.com/electromagnetic-propulsion.htm

Bunk.

Either he's leaving out something important (interaction with the solar wind? why a picture featuring the heliopause?) in which case the reporting is bad to the point of rendering the article useless, or it's the kind of stuff that's often peddaled by hucksters.

Evan
2005-Jan-21, 08:48 PM
Putting a uranium fission reactor in space is a lot safer than a plutonium RTG. A uranium reactor that has never been operated has no daughter radionuclides present, only uranium which is less toxic than lead. Also, the radioactivity level of uranium is extremely low as is reflected by the half life of 4.5 billion years for 238 and 704 million for 235. You could safely carry a uranium fuel pellet in your pocket. Plutonium 239 at 24,000 years is much more active and far more toxic.

If a worst case accident happened and the contents of a uranium reactor that had not been operated were spread about no cleanup would be indicated.

kg034
2005-Jan-22, 08:13 AM
Putting a uranium fission reactor in space is a lot safer than a plutonium RTG. A uranium reactor that has never been operated has no daughter radionuclides present, only uranium which is less toxic than lead. Also, the radioactivity level of uranium is extremely low as is reflected by the half life of 4.5 billion years for 238 and 704 million for 235. You could safely carry a uranium fuel pellet in your pocket. Plutonium 239 at 24,000 years is much more active and far more toxic.

If a worst case accident happened and the contents of a uranium reactor that had not been operated were spread about no cleanup would be indicated.

Unless, of course you were to breathe in some of the fine uranium dust :)...and have a bit of uranium create a nice little home in your lung alveolae....and then endure the ensuing nice little alpha bombardment of exposed tissue...for the next 4.5+ bil yrs!

joema
2005-Jan-22, 04:08 PM
Just keep in mind at least 1.7 METRIC TONS of Plutonium 239 have already been vaporized into the atmosphere during the 423 atmospheric nuclear bomb tests. Likewise a large quantity of U-235 and other Uranium isotopes.

You can safely hold U-235 or Pu-239 in your hand. It's true dust is extremely dangerous, especially Pu.

Evan
2005-Jan-22, 04:12 PM
That doesn't change the fact that a uranium reactor (un-started) is still much safer than a RTG. Depleted uranium is used for bullets and no one seems to be very concerned about cleaning that up. FYI, depleted uranium is U238 that has been processed to remove nearly all U235. It is NOT somehow related to used reactor fuel which is what many think. It is considered as an inert waste product. A fission reactor may contain uranium fuel with between 5 to 20% U235 enrichment (also not a problem). I can't think of a better place to put a reactor than space, heading away from Earth. It seems an ideal use for nuclear power. I am a strong advocate for nuclear power for space missions, as long as they are NOT in LEO. It only makes sense. It is time for some public education. This could make a BIG difference to the space program.

Evan
2005-Jan-22, 04:15 PM
Joema,

I cannot stress strongly enough the difference between unreacted nuclear fuel and that which has fissioned. PU is nasty whatever the case. Uranium, while not benign, is relatively harmless in the unreacted state.

joema
2005-Jan-22, 04:47 PM
Joema,

I cannot stress strongly enough the difference between unreacted nuclear fuel and that which has fissioned. PU is nasty whatever the case.
Yes, my point was worrying about the tiny probability of releasing Uranium from an unstarted reactor seems illogical, since TONS of Uranium and Plutonium have already been released into the atmosphere.

Andrew
2005-Jan-22, 07:05 PM
A fission reactor may contain uranium fuel with between 5 to 20% U235 enrichment (also not a problem).
I was under the impression that, for space applications, it is thought that the reactor fuel should be very highly enriched uranium (i.e. 'weapons grade'), far beyond the level of enrichment required to merely sustain fission. Otherwise, most of the fuel mass is just dead weight.

kg034
2005-Jan-22, 07:28 PM
I can't think of a better place to put a reactor than space, heading away from Earth. It seems an ideal use for nuclear power. I am a strong advocate for nuclear power for space missions, as long as they are NOT in LEO. It only makes sense. It is time for some public education. This could make a BIG difference to the space program.

I holeheartedly agree. As SUV :evil: -lovers would put it, "we need more power"!
It is a must in order to sail the solar system.



That doesn't change the fact that a uranium reactor (un-started) is still much safer than a RTG. Depleted uranium is used for bullets and no one seems to be very concerned about cleaning that up.

Just because no one seems to be very concerned about cleaning it up, doesn't mean that it cannot get into the water supply, food supply, etc....And as far as I know, outside of military training grounds, its been used in public only outside of the US. No incentive to go and clean up there, after you've just used it.

Evan
2005-Jan-22, 09:54 PM
Andrew,

True, a spaceborne reactor should have highly enriched fuel. This is still not a problem as U235 is still nearly as inert biologically and radiologically as U238 as far as potential worst case pollution goes. If it should become scattered in a launch accident no one is going to collect it all and make a bomb with it.



Just because no one seems to be very concerned about cleaning it up, doesn't mean that it cannot get into the water supply, food supply, etc....And as far as I know, outside of military training grounds, its been used in public only outside of the US. No incentive to go and clean up there, after you've just used it.

Without going into politics it is in the best interest of the US to not pollute foreign lands. I am not advocating the use of depleted uranium weapons anywhere.

kg034
2005-Jan-22, 11:36 PM
Just keep in mind at least 1.7 METRIC TONS of Plutonium 239 have already been vaporized into the atmosphere during the 423 atmospheric nuclear bomb tests. Likewise a large quantity of U-235 and other Uranium isotopes.

You can safely hold U-235 or Pu-239 in your hand. It's true dust is extremely dangerous, especially Pu.

Hi Joe, any references for the above numbers? IIRC, plutonium delivers ~ 50mSv/microgram. The concentration in the atmosphere would be small, assuming perfect mixing :)...but the Pu had to go somewhere....

joema
2005-Jan-23, 12:27 AM
Hi Joe, any references for the above numbers...
Various source estimate between 423 and 516 atmospheric nuclear tests. Here's one: http://archive.greenpeace.org/comms/nukes/ctbt/read8.html

PU-239 critical mass is about 10kg: http://www.milnet.com/nukeweap/Chart1.gif

Maximum fission bomb efficiency is 20%. This means 20% of the material fissions, the rest is scattered by the detonation.

Numerous fission bombs were bigger than 10kg, and each H-bomb required a fission bomb to trigger it. Some fission bombs were Uranium, but most were Plutonium. But let's use 10kg per bomb as a conservative figure.

80% x 10kg Pu-239 x 423 bombs = 3.4 metric tons. So my previous figure was overly conservative. No matter how you calculate it a huge amount of Plutonium has already been scattered into the atmosphere.

Considering bombs are designed TO release material, and spacecraft RTGs and reactors are designed NOT to release material, and TONS of material has ALREADY been released, the risk/benefit ratio of spacecraft RTGs and reactors seems pretty good.

Evan
2005-Jan-23, 06:37 AM
Actually it only takes a couple of kilos of Pu to make a fission bomb trigger. But, the difference is academic.

No, I cannot give a source. It is still classified. Californium.

kg034
2005-Jan-23, 11:02 AM
thanks, joema.


Hi Joe, any references for the above numbers...
Various source estimate between 423 and 516 atmospheric nuclear tests. Here's one: http://archive.greenpeace.org/comms/nukes/ctbt/read8.html

PU-239 critical mass is about 10kg: http://www.milnet.com/nukeweap/Chart1.gif

Maximum fission bomb efficiency is 20%. This means 20% of the material fissions, the rest is scattered by the detonation.

Numerous fission bombs were bigger than 10kg, and each H-bomb required a fission bomb to trigger it. Some fission bombs were Uranium, but most were Plutonium. But let's use 10kg per bomb as a conservative figure.

80% x 10kg Pu-239 x 423 bombs = 3.4 metric tons. So my previous figure was overly conservative. No matter how you calculate it a huge amount of Plutonium has already been scattered into the atmosphere.

It certainly is a lot of Pu...It would be interesting to estimate the contamination spread of a typical detonation...what percentage of the Pu would fall back to the ground within,say, a 50mi radius, and what amounts could be detected half way around the globe... But, then local atmospheric conditions would also play a role... In all, I just find the 3.4 metric tons of Pu, 500+ atmospheric tests numbers fascinating





Considering bombs are designed TO release material, and spacecraft RTGs and reactors are designed NOT to release material, and TONS of material has ALREADY been released, the risk/benefit ratio of spacecraft RTGs and reactors seems pretty good.
I agree with you, with the emphasis that if we've already dumped so much Pu, it doesn't mean that evey precaution should not be made to not release any more :).
I'm all for fission-powered spacecraft.....Perhaps the SeaLaunch venture might be an interesting launchsite for these.

sarongsong
2005-Jun-27, 08:28 PM
June 27, 2005 (http://www.signonsandiego.com/uniontrib/20050627/news_1n27nuke.html)
"The Bush administration is planning the government's first production since the Cold War of plutonium 238...would produce 330 pounds over 30 years at the Idaho National Laboratory...most of the new plutonium is intended for secret missions and declined to divulge details..."

Tunga
2005-Jun-28, 02:38 PM
I read the original link - its a little confusing, therefore I draw no judgement. There are at least two ways to move an object in space - propulsion and field. Our current spacecraft are designed around propulsion engines. They have limited range because they consume material. In general, that limits design for interstellar travel. The other approach which hasn't and may never be developed is an engine that uses a field for acceleration.

One of the interesting properties of superconductors is their ability to repel magnetic field. It is called the Meissner Effect. They repel either polarity of a magnetic field. I attended a university science fair about a decade ago when they demonstated this effect. They placed a magnet on a superconductor and then cool the superconductor. The magnet hovered about an inch above the superconductor, just floating in the air. I asked what would happen if you substituted a supermagnet in place of a magnet. The TA was willing to experiment. That experiment shot the supermagnet into the ceiling like a bullet and then ricocheted around the room. If this feature of superconductors could be harvested for space flight, it might provide us with an interstellar engine. The sun has a strong magnetic field and there are many objects in galaxy that are significantly stronger.

John Kierein
2005-Jun-28, 03:02 PM
Here's some really cool stuff. Look especially at the spinning copper plate demos.

http://www.amasci.com/neodemo.html

publiusr
2005-Jun-29, 05:08 PM
There is a crazy publication called ELECTRIC SPACECRAFT JOURNAL you might look up on the web.

At least the lifter concept might be good for a Zeppelin--with that surface area the ion wind should be very strong.