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Fission plants doesn't perform well in space because they require heat engines to do work upon a generator. The reason this is so is because the waste heat has

by ohiovr 4y ago

Fission plants doesn't perform well in space because they require heat engines to do work upon a generator. The reason this is so is because the waste heat has to be dealt with in order to work. There is no air or water to dump this excess heat into so the only other alternative is to use radiation to radiate IR or incandescence away from the working fluid after it has been used to run a turbine or piston engine. The problem with that is, this way of dealing with heat removal isn't very fast at the temperatures that most boilers operate in. And the reason is because rte of the loss of energy from a blackbody depends on the fourth power of it's temperature. Thank you Hyper-physics site for explaining the pieces parts to me. What if we had a heat engine that could? That is a tall order because even refractory solids weaken and soften with temperature. What about droplet cooling? Unless the vapor pressure is absolutely minimal, too much working fluid will be lost.

Trouble_007 4y ago
search: 'Temperatures of Outer Space'
- ohiovr 4y ago
  Here is a clue: It is easier to make a high altitude plane than it is a rocket, yet no one has made a nuclear electric propelled propeller aircraft before. https://en.wikipedia.org/wiki/Nuclear-powered_aircraft https://en.wikipedia.org/wiki/Nuclear-powered_aircraft. Temperatures are pretty darn cold there too.
  - Trouble_007 4y ago
    >Temperatures are pretty darn cold there too. The average temperature of distant, empty interstellar space is considered to be 2.73° Kelvin above absolute zero. 2.73° Kelvin = -270.42° Celsius = -454.75° Fahrenheit. - I consider this temperature to be really damm cold!
    - ohiovr 4y ago
      Still doesn't seem to help with radiation emission because the rate of energy loss by a body is still the fourth power of it's temperature. And even at a such a fantastic sounding advantage, it only gets approaches competitive results in respect to air cooling at a surface temperature beyond 2000 C. The Russians were the only ones to achieve a megawatt range continuous reactor in space by dealing with waste heat transmission on a surface that was above 1500 C. The way they did it was by using a thermionic converter which is a heat engine that uses electrons as a working fluid. No one has matched the specs of their thermonic converters and interest in the technology is very small. It is also extremely hard to pull off because 1500 C is just the "cold" end! The hot end must be significantly hotter and this temperature is even hotter than some of our best refractory ceramics can withstand under the physical stress they undergo. Not only that, but these temperatures cause evaporation of the electrodes. The heat regime causes many hard problems that have no easy solutions. I'll tell you I went down this rabbit hole for nearly a year after watching a simple demonstration of a torch powering a fan using a thimble sized converter. Even if you are at the top of the field in materials science research, there is little that has not been tried to make it more practical. But in case you are interested, the work function is the key property that could enable easier designs.
      - Trouble_007 4y ago
        OK, For our interstellar deep-space probe. As we get better at space-Origami (well... unfolding really), envisage a flexible, combined Solar Sail [0], Solar Cell array [1] (both requires a Suns energy), and heat-sink [2] for the cold side of a Thermopile [3], heat being provided by radioactive decay. To provide our electric power for onboard systems and of course propulsion. ---- [0] Solar Sail : https://en.m.wikipedia.org/wiki/Solar_sail https://en.m.wikipedia.org/wiki/Solar_sail [1] Solar Cell Array : https://en.m.wikipedia.org/w/index.php?search=Solar+Cell+array&title=Special:Search https://en.m.wikipedia.org/w/index.php?search=Solar+Cell+arr... ^^(The above is purposely a search of wikipedia)^^ [2] Heat Sink : https://en.m.wikipedia.org/wiki/Heat_sink https://en.m.wikipedia.org/wiki/Heat_sink [3] Thermopile : https://en.m.wikipedia.org/wiki/Thermopile https://en.m.wikipedia.org/wiki/Thermopile Edit to add; Science Direct » Topics » earth-and-planetary-sciences » solar-sail : https://www.sciencedirect.com/topics/earth-and-planetary-sciences/solar-sail https://www.sciencedirect.com/topics/earth-and-planetary-sci... OOPS! edit again; fix 'requires a Suns light' to 'requires a Suns energy'

by ohiovr 4y ago

Trouble_007 4y ago

search: 'Temperatures of Outer Space'

ohiovr 4y ago
Here is a clue: It is easier to make a high altitude plane than it is a rocket, yet no one has made a nuclear electric propelled propeller aircraft before. https://en.wikipedia.org/wiki/Nuclear-powered_aircraft https://en.wikipedia.org/wiki/Nuclear-powered_aircraft. Temperatures are pretty darn cold there too.
- Trouble_007 4y ago
  >Temperatures are pretty darn cold there too. The average temperature of distant, empty interstellar space is considered to be 2.73° Kelvin above absolute zero. 2.73° Kelvin = -270.42° Celsius = -454.75° Fahrenheit. - I consider this temperature to be really damm cold!
  - ohiovr 4y ago
    Still doesn't seem to help with radiation emission because the rate of energy loss by a body is still the fourth power of it's temperature. And even at a such a fantastic sounding advantage, it only gets approaches competitive results in respect to air cooling at a surface temperature beyond 2000 C. The Russians were the only ones to achieve a megawatt range continuous reactor in space by dealing with waste heat transmission on a surface that was above 1500 C. The way they did it was by using a thermionic converter which is a heat engine that uses electrons as a working fluid. No one has matched the specs of their thermonic converters and interest in the technology is very small. It is also extremely hard to pull off because 1500 C is just the "cold" end! The hot end must be significantly hotter and this temperature is even hotter than some of our best refractory ceramics can withstand under the physical stress they undergo. Not only that, but these temperatures cause evaporation of the electrodes. The heat regime causes many hard problems that have no easy solutions. I'll tell you I went down this rabbit hole for nearly a year after watching a simple demonstration of a torch powering a fan using a thimble sized converter. Even if you are at the top of the field in materials science research, there is little that has not been tried to make it more practical. But in case you are interested, the work function is the key property that could enable easier designs.
    - Trouble_007 4y ago
      OK, For our interstellar deep-space probe. As we get better at space-Origami (well... unfolding really), envisage a flexible, combined Solar Sail [0], Solar Cell array [1] (both requires a Suns energy), and heat-sink [2] for the cold side of a Thermopile [3], heat being provided by radioactive decay. To provide our electric power for onboard systems and of course propulsion. ---- [0] Solar Sail : https://en.m.wikipedia.org/wiki/Solar_sail https://en.m.wikipedia.org/wiki/Solar_sail [1] Solar Cell Array : https://en.m.wikipedia.org/w/index.php?search=Solar+Cell+array&title=Special:Search https://en.m.wikipedia.org/w/index.php?search=Solar+Cell+arr... ^^(The above is purposely a search of wikipedia)^^ [2] Heat Sink : https://en.m.wikipedia.org/wiki/Heat_sink https://en.m.wikipedia.org/wiki/Heat_sink [3] Thermopile : https://en.m.wikipedia.org/wiki/Thermopile https://en.m.wikipedia.org/wiki/Thermopile Edit to add; Science Direct » Topics » earth-and-planetary-sciences » solar-sail : https://www.sciencedirect.com/topics/earth-and-planetary-sciences/solar-sail https://www.sciencedirect.com/topics/earth-and-planetary-sci... OOPS! edit again; fix 'requires a Suns light' to 'requires a Suns energy'