Artificial fission star

[mcbethcg]

Here is a goofy idea.<br /><br />How about an artificial star, orbiting a cold moon or world, to provide additional warmth supplimenting the sun? Perhaps many artificial stars.<br /><br />They would be nothing more than a huge mass of radioactive materials, acting as a reactor at a very high temperature, at least partly gaseous. They would have to be big enough to have enough gravity to keep itself together. Mix it with lead or something so that the 'atmospere' of vaporized heavy metals would act as a radiation shield, but would be heated from below and reradiate the heat.<br /><br /> Assuming that enough radioactive materials exist, Is it otherwise possible?

 

[mikeemmert]

A sphere of plutonium 238 the size of a golf ball is red hot from alpha decay.<br /><br />I don't know how much uranium it would take to glow from alpha decay. I do know that the uranium mines in Grants, New Mexico are pretty hot.<br /><br />Plutonium 238 has a half life of 87 years and uranium has an average (three isotope) half life of 4.5 x 10^9 years, so uranium decays about 52 million times slower than plutonium 238. To a first approximation you need 52 million golf-ball sized quantities of uranium to have a mass that glows red hot. But, if you use the square-cube law, a solid uranium sphere will glow red hot with a considerably smaller quantity. I'll let you calculate that. I don't know how big a golf ball is (google that), but plutonium has a density of about 16 grams per cubic centimeter and uranium, about 18.<br /><br />You would have to use a mixture of uranium and it's decay products exactly like what is found in uranium ore. That's because all but one of these decay products (lead) are themselves radioactive and have different half-lives than uranium, so if you started with pure uranium, the decay products will cause the sphere to overheat.<br /><br />Think about that. You don't just not need to process the uranium, you <i>shouldn't</i> process the uranium. It's a lot cheaper that way.<br /><br />Is there enough uranium? You bet there is. It's a common substance. You only need a few tens of thousands of tons. You might even have to dilute it. That's simple, use raw ore instead of metallic uranium. No machinery, no special building techniques...sounds doable to me.<br /><br />I haven't calculated any of this, but the calculations are very simple.<br /><br />It's your project. Have fun.

 

[mcbethcg]

Too bad I don't know the math.

 

[dragon04]

How would you control the reaction? <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[mlorrey]

This is actually a pretty good idea for warming up cold planets. Putting one in orbit around Mars, for instance, would significantly aid a terraforming project, is a smarter idea than my idea of dumping nuke waste in volcanic craters.<br /><br />Building one large enough to provide, say, 0.1 solar flux, should be sufficient to trigger a cascade CO2 outgassing sufficient to produce an earth-normal atmospheric pressure, with equatorial temps typical of temperate climates on earth.<br /><br />The object should probably orbit in a long orbit, of 20-30 days duration, like our moon. This would provide room for a martian skyhook, and provide a gravitational tide that may help restart martian tectonic processes.<br /><br />Given this, its orbit would likely be about 100,000 miles from the planet. At that distance, its emittance area would cover 3.14 x 4 x 10^10 miles^2, or just over 125.6 billion square miles. Given that the cross sectional area of Mars is (at 2,097 miles in radius) 12,560 miles^2, Mars would intercept 0.000001% of the emitted energy of such an object. In order for Mars to receive 0.1 solar flux (about 140 watts/meter^2), which is about 362,598,335 watts / mile^2, the artificial sun would need to emit 45,542,350,932,148,224,000.00 watts, or about 45 million petawatts. This power requirement demands 1,366,270,527,964 tons of uranium.<br /><br />The reaction would likely be self moderating based on the materials you put into it to start with. This is not unusual, there have been naturally occuring nuclear reactors found by geologists that burned out long ago, the most well known being one in Ghana that occured a billion years ago, which was actually four separate reactor 'cores' in different areas of a large uranium formation. These natural reactors burned for more than a million years each and had an average power rating of about 25 kw. <br /><br />The tonnage demands for such a fission star could be signficantly reduced if the fission core were surrounded by a refle

 

[mcbethcg]

My idea was that it would be a lump without structures. Too hot to have structures, in fact, and that it would self moderate naturally.<br /><br />As temperatures increased, it would expand, causing the the reaction to dampen. A little more excess temperature, and radioactive elements would take up gaseous form, further dampening the reaction. <br /><br />The main problem would be that I would not want the gaseous uranium to blow away in the solar wind. This would require significant gravitational pull, I am afraid.

 

[nexium]

The 45 millon petawatts may be correct, but assuming the fisson reaction is moderated (carbon vapor, perhaps) just below critical mass, the core temperature could be millions of degrees, and the urainium would be half used in a few years, so much less uranium would be needed. <br />With a thick lead vapor atmosphere (or most any other heavy elements) only a few gamma photons would reach Mars. Leathal ultraviolet and solar wind ions might however be a hazard, if the photosphere was hotter than about 6000 degrees k and/or the photoshere gravity less than 1/2 g. 1/2 g would likely require more mass than Mars. <br />Perhaps 45 thousand petawatts would be needed, if Mars is in a circular orbit around this artifical sun with a radius of 12,000 miles, instead of 100,000 miles, but that would interfer with satelites of most types, including the 2 moons of Mars and a martain skyhook. I'm guessing, so do not hessitate to refute, embellish and/or comment. Neil

 

[mcbethcg]

I love you guys. <br /><br />Incidentally- FYI- I picked a lead "atmosphere" because <br /><br />1) The molecular speed would be low at any given heat, hopefully allowing it to form an atmospere that contains few atoms moving at the satelites miniscule escape velocity.<br /><br />2) Heavy atoms would be affected less by a solar wind. <br /><br />Another thing to think about is that the upper atmosphere would always be the coolest, because it would be the radiating surface. So it would be even less likely to try to leave.<br /><br />2)

 

[vogon13]

Crikey!<br /><br />They have a conniption when I want to launch a couple of Orion class starships, but this goes un-challenged?<br /><br /><br /><img src="/images/icons/wink.gif" /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[mcbethcg]

Hey, I love Orion.<br /><br />This is just a new idea. (To me at least) I was just wondering what others thought of it.

 

[mlorrey]

Well, 4.5 terawatts is needed to illuminate a disk the diameter of Mars with 0.1 solar flux. You can scale the illumination amount up or down, but unless you have a focusing structure, all but an extremely tiny amount of the output is never going to reach your planet.<br /><br />I projected a 100,000 mile orbit to simulate a lunar orbital period. If you plan on having a geosynchronous skyhook/tether on your planet, you cannot have this body in a faster orbit below geosynch. If it were in geosynch, it would always illuminate the same side of the planet, and the higher you go the closer to a days rotational frequency you get. Assuming you don't want illumination at the tether's counterbalance station to exceed 1 solar flux, the reactor core should be at least 10% higher than the counterbalance.<br /><br />As Mars areostationary orbit is about 11,000 km above the surface, or 6835 miles, and assuming a counterbalance were located at about 8000 miles (12874 km), then we could use the moon Deimos as the fission pile assembly site. As it is a carbonaceous chrondrite asteroid captured by Mars, it should have sufficient carbon on location to provide moderation for the uranium to be planted there. A supercritical pile should melt its way to Deimos' core and treat the carbon as a massive black body emitter (like a tungsten light bulb filament) to emit a natural spectrum of light without need of additional radiation shielding.<br /><br />Deimos is at 23,000 km altitude, which should result in peak illumination levels at the tether counterbalance of approximately .2 sols.<br /><br />At a 23,000 km altitude (~14,300 miles), the fission star would have to put out 9.3171980223253338689e+17 watts in an unfocused configuration. This is 931,719,802,232,533,386.89 or 932 terawatts output, which would require 2.5357259596235166604e+13 kg or 27,951,594,066.97 tons of uranium.<br /><br />I would highly suggest that this object have a shell built around it, containing the object by a magnetic field

 

[mlorrey]

It isn't new, I read an SF story when I was a kid that proposed just that: turn Deimos into a fission star to warm up and terraform Mars.

 

[mcbethcg]

Any idea what story?

 

[vogon13]

One of Arthur Clarke's, IIRC.<br /><br />Maybe Sands of Mars.<br /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[mlorrey]

No idea, though it was a juvie, about a kid whose father was working on the Deimostar project, which was a secret project by Martian settlers leading a revolution, as Earth used its supply of food and other materials as a means of controlling martian colonists, as well as them having to live in pressure domes which are easily controllable, concentrate the population and allows for them to be eliminated in one fell swoop if need be. The Deimostar made them independent logistically as well as politically.