How feasible would it be to generate nuclear energy in outer space

[Causarius]

...and deliver it to Earth, as an effort in harm reduction from the dangers that nuclear technology presents?

 

Are the resources available to get sufficient nuclear reactors in orbit, and could a viable method of transportation of the product back to Earth be possible?

 

 

 

I have this idea of giant cables reaching out from the planet like tendrils with a nuclear power plant at the end of it, and was just wondering what radical solutions to mitigate the negative aspects of nuclear energy there might be.

[Cap'n Refsmmat]

It would probably be easier to put large solar panels in orbit and deliver the energy back to earth. Nuclear power in space brings the question, "How do I launch nuclear fuel into orbit without the risk of the rocket exploding on takeoff?"

[Horza2002]

As Cap'n Refsmmat has said, the issue would be how do you prevent the radioactive material scattering over a very large area of the planet if anything went wrong.

[Cap'n Refsmmat]

Also watch out for incidents like Kosmos 954:

 

http://en.wikipedia.org/wiki/Cosmos_954

[triskaidekaphile]

i think trying to cool it might also be problem since its in an insulating vacuum

 

 

[keelanz]

i think trying to cool it might also be problem since its in an insulating vacuum

 

 

 

cooling in space is a LOL

 

i hear it gets chilly in winter up in space

[SMF]

Cooling is a big problem in space because there can be no conduction or convection, only radiation.

 

As for generating power in space, in Japan Mitsubishi Electric and IHI Corp. are working on a space based solar power plant. Similarly, in California Solaren and PG&E are working on solar powered space based electricity generation.

http://inhabitat.com/japan-plans-21-billion-solar-space-post-to-power-294000-homes/

http://cleantech.com/news/4361/solarens-plan-outer-space

SM

[CaptainPanic]

I see few practical problems that we cannot overcome. My main question is: WHY?

Why not build the reactor on the surface, if the electricity is needed down here anyway?

It would probably be easier to put large solar panels in orbit and deliver the energy back to earth. Nuclear power in space brings the question, "How do I launch nuclear fuel into orbit without the risk of the rocket exploding on takeoff?"

I think an explosion on take-off is not a major issue. We can build containers that can withstand practically any explosion.

It's the heat of re-entry and/or impact that can burn up almost anything... Still, I think we can even design something that can withstand that, and keep a nuclear fuel in its container.

 

Cooling is a big problem in space because there can be no conduction or convection, only radiation.

 

Although that is true for the entire spacecraft, it is not true for the nuclear reactor itself.

You can have water cooling like any other reactor... and the water must then be cooled by radiation, which is no problem, as long as you point your (very large) radiator away from the sun, and coat its backside (which is pointed towards the sun) with a highly reflective material.

[SMF]

CaptainPanic, why such a big difference between a spacecraft and a reactor? We are only talking about 100 degrees C, but a huge output. SM

Edited April 12, 2011 by SMF

[CaptainPanic]

CaptainPanic, why such a big difference between a spacecraft and a reactor? We are only talking about 100 degrees C, but a huge output. SM

What I meant to say is that the reactor is inside the spaceship/spacestation. So, the reactor is cooled by the spaceships/spacestation water system, and then the water system cools itself with radiators.

 

You do not want to cool a nuclear reactor directly with radiation...

[SMF]

CaptainPanic. I was just thinking that trying to radiate heat to condense water vapor for the generator cycle might take a monster radiator because condensing steam is done at such low temperatures. I suppose you could use a fluid for the turbines that condensed from a vapor at a very high temperature. SM

[keelanz]

man....cant is the cancer of wont, any practicalities just need to be figured out, cooling really is not the issue.

[CaptainPanic]

CaptainPanic. I was just thinking that trying to radiate heat to condense water vapor for the generator cycle might take a monster radiator because condensing steam is done at such low temperatures. I suppose you could use a fluid for the turbines that condensed from a vapor at a very high temperature. SM

Condensing steam is done at about 100 degrees Celsius, if you keep the pressure at 1 bar (atmospheric).

The ISS also uses radiators to get rid of the heat.

 

Without thermal controls, the temperature of the orbiting Space Station's Sun-facing side would soar to 250 degrees F (121 C), while thermometers on the dark side would plunge to minus 250 degrees F (-157 C). There might be a comfortable spot somewhere in the middle of the Station, but searching for it wouldn't be much fun! (source)

 

Waste heat is removed in two ways, through cold plates and heat exchangers, both of which are cooled by a circulating water loop. Air and water heat exchangers cool and dehumidify the spacecraft's internal atmosphere. High heat generators are attached to custom-built cold plates. Cold water -- circulated by a 17,000-rpm impeller the size of a quarter -- courses through these heat-exchanging devices to cool the equipment.

 

"The excess heat is removed by this very efficient liquid heat-exchange system," said Ungar. "Then we send the energy to radiators to reject that heat into space."

 

Still, I do not understand why anyone would want to put a nuclear reactor in orbit anyway (not if the goal is to supply the earth with power).

[SMF]

CaptainPanic, I strongly agree with your attitude regarding nuclear power generation in space, but my interest in the heat radiation problem is still not satisfied. This is because it seems to me that the International Space Station only has to deal with waste heat from electrical devices that are powered by a solar panel array that one could find on a very opulent solar home in California. The amount of heat from a sizable commercial reactor/generator would be, I think, somewhere around three orders of magnitude of what is generated on the ISS. This would probably require piping and radiators that would be too massive to even think about putting into orbit. I think the problem is practical, not theoretical, but there may be something I don't understand. SM

[CaptainPanic]

CaptainPanic, I strongly agree with your attitude regarding nuclear power generation in space, but my interest in the heat radiation problem is still not satisfied. This is because it seems to me that the International Space Station only has to deal with waste heat from electrical devices that are powered by a solar panel array that one could find on a very opulent solar home in California. The amount of heat from a sizable commercial reactor/generator would be, I think, somewhere around three orders of magnitude of what is generated on the ISS. This would probably require piping and radiators that would be too massive to even think about putting into orbit. I think the problem is practical, not theoretical, but there may be something I don't understand. SM

I think you understood just fine.

 

I think that the ISS has about 8 kW of power, while a full-size nuclear plant can be around 1 GW. That's a factor of 125000, or five orders of magnitude.

Those radiators would be massive... and there would be a lot of piping involved, because you need to pump around a lot of water (I'm guestimating that it's about 1 m3/s).

 

I would guestimate that you can radiate about 1 kW/m2 of heat if a radiator in space points away from the sun. So, you would need about 1,000,000 m2 of surface area (1 square kilometer). Pretty big indeed.

 

Providing cooling water for a 1 GW power-unit is always a very large operation... which is why companies like to get cooling water from the sea or a river. It saves a tremendous amount of money. Without river/sea water, they need to build cooling towers, often more than one, which are huge (100 m high) structures.

[SMF]

With a little web research I have gleaned a little additional information regarding what CaptainPanic and I have been talking about that I feel I should add for accuracy, and that might be interesting to you all. The ISS actually has a pretty big PV solar power array. The station has eight 23KW arrays, so the power input is much bigger than a large system for an expensive California home that I mentioned previously for comparison. This much energy is more in the range of PV systems in my area that have been erected on a brewery, a winery, and a local community college to save money on electricity. This is still miniscule relative to the heat generated by a commercial gigawatt nuclear plant that would require a large and prohibitively expensive radiative cooling system that would have to be lifted to and assembled in orbit. SM