Author Topic: Development and Testing of Space Fission Technology at NASA-MSFC  (Read 4505 times)

Offline rdale

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    The Early Flight Fission Test Facility (EFF-TF) at NASA-Marshall Space Flight Center (MSFC) provides a capability to perform hardware-directed activities to support multiple inspace nuclear reactor concepts by using a non-nuclear test methodology. This includes fabrication and testing at both the module/component level and near prototypic reactor configurations allowing for realistic thermal-hydraulic evaluations of systems. The EFF-TF is currently performing non-nuclear testing of hardware to support a technology development effort related to an affordable fission surface power (AFSP) system that could be deployed on the Lunar surface. The AFSP system is presently based on a pumped liquid metal-cooled reactor design, which builds on US and Russian space reactor technology as well as extensive US and international terrestrial liquid metal reactor experience. An important aspect of the current hardware development effort is the information and insight that can be gained from experiments performed in a relevant environment using realistic materials. This testing can often deliver valuable data and insights with a confidence that is not otherwise available or attainable. While the project is currently focused on potential fission surface power for the lunar surface, many of the present advances, testing capabilities, and lessons learned can be applied to the future development of a low-cost in-space fission power system. The potential development of such systems would be useful in fulfilling the power requirements for certain electric propulsion systems (magnetoplasmadynamic thruster, high-power Hall and ion thrusters). In addition, inspace fission power could be applied towards meeting spacecraft and propulsion needs on missions further from the Sun, where the usefulness of solar power is diminished. The affordable nature of the fission surface power system that NASA may decide to develop in the future might make derived systems generally attractive for powering spacecraft and propulsion systems in space. This presentation will discuss work on space nuclear systems that has been performed at MSFC's EFF-TF over the past 10 years. Emphasis will be place on both ongoing work related to FSP and historical work related to in-space systems potentially useful for powering electric propulsion systems.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090001896_2008048234.pdf

Offline simonbp

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The second-to-last slide mentions current work on gas-core fission reactors! That would be a breakthrough...

Simon ;)

Offline scienceguy

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Is one of the biggest difficulties with nuclear power in space the need to cool the steam that's used to spin the turbine? Since space is cold, couldn't you just send coolant outside and cool it so it can cool the steam?
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Online Mark S

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Is one of the biggest difficulties with nuclear power in space the need to cool the steam that's used to spin the turbine? Since space is cold, couldn't you just send coolant outside and cool it so it can cool the steam?

On Earth, heat from reactors and steam turbines is dumped by convection (or conduction) to large external heat sinks, such as the atmosphere or cooling ponds.

In space, you can't use a heat exchanger, there is nothing to exchange heat with.  Instead, you have to radiate the heat away with large radiators, which is much less efficient.

Mark S.

Offline nomadd22

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Is one of the biggest difficulties with nuclear power in space the need to cool the steam that's used to spin the turbine? Since space is cold, couldn't you just send coolant outside and cool it so it can cool the steam?

Space isn't cold. In fact it's harder to dispose of excess heat because there's no medium for convection. You have to radiate it all. You might build a one megawatt reactor that weighs 500 pounds and need four times that much mass in radiators to get rid of the heat.
 Where's that room temp superconductor Niven wrote about?

Offline Lars_J

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Where's that room temp superconductor Niven wrote about?

In the same place were you can find the 'unobtainium' used to construct Ringworld.  ;D (Ok, not quite the same implausibility level)
« Last Edit: 01/21/2009 08:20 pm by Lars_J »

Offline simonbp

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You might build a one megawatt reactor that weighs 500 pounds and need four times that much mass in radiators to get rid of the heat.

Take a look at JIMO, the most realistic nuclear spacecraft ever proposed, and compare the size of the reactor and the radiators...

Simon ;)

Offline Bejowawo

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Is one of the biggest difficulties with nuclear power in space the need to cool the steam that's used to spin the turbine? Since space is cold, couldn't you just send coolant outside and cool it so it can cool the steam?

On Earth, heat from reactors and steam turbines is dumped by convection (or conduction) to large external heat sinks, such as the atmosphere or cooling ponds.

In space, you can't use a heat exchanger, there is nothing to exchange heat with.  Instead, you have to radiate the heat away with large radiators, which is much less efficient.

Mark S.


IMHO first you would use the heat for process heat and possibly for habitat heating.

For the residual heat, would it be possible to dig or drill some holes in the lunar soil, bury some pipes carrying a heating medium and get rid of the heat this way - just like a heat pump on earth but the other way round.

Would that be a possibility?

Offline kevin-rf

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IMHO first you would use the heat for process heat and possibly for habitat heating.

For the residual heat, would it be possible to dig or drill some holes in the lunar soil, bury some pipes carrying a heating medium and get rid of the heat this way - just like a heat pump on earth but the other way round.

Would that be a possibility?

An old saying I have heard many a time, nothing is a better insulator than 100' of rock. The problem with that is you will be pumping heat in and it would not be coming out. Meaning the temperature of you lunar soil will soon be the same temp as your pipes. So much for a radiator. It makes a good way to store heat, but a bad radiator.

During a recent ice storm we tapped our natural gas hot water tank with a garden hose (we had gas, we had water, no power, no heat, no generator) and snaked 150' of garden hose through the house and out to the bath tub. Kept us a nice an cozy 60 degrees in the sub zero temps for a couple of days (Before all the greens start screaming, about the water it was a low flow rate filling the tube every 6 hours or so in an area of the country that has plenty of water).

You would be better off snaking your tube on the surface of the moon than under the ground.

Ever notice that caves stay a constant temperature year round, mid 40's in NY, upper 40's in PA, low 50's in WV... This is why.
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Offline Patchouli

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Where's that room temp superconductor Niven wrote about?

In the same place were you can find the 'unobtainium' used to construct Ringworld.  ;D (Ok, not quite the same implausibility level)

Maybe we should call unobtainium uninventedium since many materials we have now were unobtianium a few decades ago.
If I described carbon fiber to someone from the 40s in the  they would tell me to quit reading so much scifi.
Carbon nano tube would sound like some far out alien technology to someone from the 60s.


A better solution for the turbine loop over steam might be the Organic Rankine cycle.
Or go the other route and run the reactor hotter since radiative cooling works better the hotter the radiator is.
Maybe find a working fluid that operates at around 1000C such as VHTR which uses helium for cooling.

This is a nut that has to be cracked before we can even think about venturing beyond the moon or even be serious about moon bases vs a camp.

« Last Edit: 01/22/2009 05:48 pm by Patchouli »

Offline Patchouli

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IMHO first you would use the heat for process heat and possibly for habitat heating.

For the residual heat, would it be possible to dig or drill some holes in the lunar soil, bury some pipes carrying a heating medium and get rid of the heat this way - just like a heat pump on earth but the other way round.

Would that be a possibility?

An old saying I have heard many a time, nothing is a better insulator than 100' of rock. The problem with that is you will be pumping heat in and it would not be coming out. Meaning the temperature of you lunar soil will soon be the same temp as your pipes. So much for a radiator. It makes a good way to store heat, but a bad radiator.

Ever notice that caves stay a constant temperature year round, mid 40's in NY, upper 40's in PA, low 50's in WV... This is why.

Actually that's much more a function of thermo mass vs insulation with the rock.
« Last Edit: 01/22/2009 05:54 pm by Patchouli »

Offline blazotron

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IMHO first you would use the heat for process heat and possibly for habitat heating.

For the residual heat, would it be possible to dig or drill some holes in the lunar soil, bury some pipes carrying a heating medium and get rid of the heat this way - just like a heat pump on earth but the other way round.

Would that be a possibility?

An old saying I have heard many a time, nothing is a better insulator than 100' of rock. The problem with that is you will be pumping heat in and it would not be coming out. Meaning the temperature of you lunar soil will soon be the same temp as your pipes. So much for a radiator. It makes a good way to store heat, but a bad radiator.

Ever notice that caves stay a constant temperature year round, mid 40's in NY, upper 40's in PA, low 50's in WV... This is why.

Actually that's much more a function of thermo mass vs insulation with the rock.


It's actually a function of thermal diffusivity, which is the ratio of thermal conductivity to heat capacity.  Wikipedia has a pretty good, although brief, page on it.  Copper and aluminum have thermal diffusivities about 100 times higher than rock, for reference.  The thermal diffusivity of the earth's crust is so low compared to the heat flux from the air and solar radiation that diurnal temperature swings of the air affect only the first few inches of soil.  Seasonal temperature swings only affect the first few feet.  Thus, below the first few feet, the temperature of the earth is constant at the annual average temperature for whatever area you are in.  Since caves are typically tens to hundreds of feet deep over most of their length, they remain at the constant temperature of the earth.  The farther north you go, the colder the average temperature is, which is why kevin-rf's examples of cave temperatures are different for different latitudes.  Here in California, we have caves from sea level to more than 10000 ft, and the average temperature is affected by altitude as well as latitude.  We have caves from with temperatures in the 60's down to the low 30's.

However, this does not mean that you cannot conduct heat into the lunar crust.  Such in-ground heat exchange is becoming more and more common on earth and works well.  The heat _does_ conduct away, just more slowly than in say water (where you get convection).  The thermal conductivity simply determines the length of pipe you need to bury and the volume of rock it needs to be buried in to dissipate the required amount of heat at steady state.  At steady state, the temperature of the rock drops smoothly from the temperature of the pipes to the average local temperature the farther you get from the pipes.  This temperature drop is what drives conduction of heat from the pipes outward into the rock.  You simply need to have enough pipe that is sufficiently spread out that the steady state conduction rate is enough to dump the heat load you have.

[edited for clarity]
« Last Edit: 01/28/2009 07:41 am by blazotron »

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