Advanced Fission

[aramis]

Heh, at one point I was trying to figure out what slapping a diesel-electric generator in a container like they use for disasters would look like, if you were stuck at a TL7 C/D/E starport and didn't want to wait for a replacement power plant.

Ugly cost in fuel space, but even worse costs in 'lifesupport'- keeping the IC aspirated would be a major strain and would require a LOT of extra oxygen and scrubbers.

For hydrogen, it multiplies "fuel" mass by 9 and volume by
LH2 density: 0.0708 So 14.12 kL
LO2 Density: 1.41, and 8x as much needed, so 8/1.41 so 5.67 kL
1.6Td and 9 tons per ton of Hydrogen fuel.

For Kerosene 2.56:1 by mass; Kerosene density 0.81-1.0, but we'll use RP1 0.81...
so, per ton of Kerosene mass: 1.235 kL
And we need 2.56 tons LOX: 1.81 kL
So, per Td, 4.5 kerosene and 11.7 LOX tons in 14 kL and 16.2 tonnes mass.

For safety, the kerosene needs to be exhausted to space

 

[Ishmael]

I think the focus should not be on how much energy can be liberated from a given fuel, but on how efficiently the released energy can be harvested for practical use.

Single-cycle steam turbines are ~33% efficient, so you have to liberate 3 Mw of energy to get 1 Mw to use, and the other 2 Mw have to be radiated away. Combined-cycle plants are maybe twice as efficient.

As tech goes up, so does energy harvest efficiencies, regardless of the source of energy.

 

[infojunky]

Hmmm. I'm sure that's the game intent or what it looks like as an outcome from our TL 7.8 perspective, but I prefer plausible gameplay options and a feel.

It was more the Image that came to my head when you brought up Locomotives.

The Idea was a Solid State high tech heat source surrounded by locally supportable machinery.

 

[kilemall]

I think the focus should not be on how much energy can be liberated from a given fuel, but on how efficiently the released energy can be harvested for practical use.

Single-cycle steam turbines are ~33% efficient, so you have to liberate 3 Mw of energy to get 1 Mw to use, and the other 2 Mw have to be radiated away. Combined-cycle plants are maybe twice as efficient.

As tech goes up, so does energy harvest efficiencies, regardless of the source of energy.

The 10% back of the envelope figure I came up with would be an increase of something like 200% over today's systems. So, already there.

Also takes care of a lot of the thermal buildup problem people are on about if we have thermogenic systems with absorptive properties.

 

[kilemall]

For hydrogen, it multiplies "fuel" mass by 9 and volume by
LH2 density: 0.0708 So 14.12 kL
LO2 Density: 1.41, and 8x as much needed, so 8/1.41 so 5.67 kL
1.6Td and 9 tons per ton of Hydrogen fuel.

For Kerosene 2.56:1 by mass; Kerosene density 0.81-1.0, but we'll use RP1 0.81...
so, per ton of Kerosene mass: 1.235 kL
And we need 2.56 tons LOX: 1.81 kL
So, per Td, 4.5 kerosene and 11.7 LOX tons in 14 kL and 16.2 tonnes mass.

For safety, the kerosene needs to be exhausted to space

Whew, I was just thinking aggressive reuse not carting all the extra oxygen.

 

[aramis]

Whew, I was just thinking aggressive reuse not carting all the extra oxygen.

You cannot reuse oxidizer. violates thermodynamics big-time.

If you have anything other than a fusion plant or a breeder fission plant, what goes in in low-entropy/high potential energy (fuel and oxidizer) comes out high entropy and low PE. Costs more to separate than it generates. (again, due to thermodynamics).

 

[kilemall]

You cannot reuse oxidizer. violates thermodynamics big-time.

If you have anything other than a fusion plant or a breeder fission plant, what goes in in low-entropy/high potential energy (fuel and oxidizer) comes out high entropy and low PE. Costs more to separate than it generates. (again, due to thermodynamics).

Er.

I'm assuming U-238, which is a plentiful radioactive relatively speaking so you just have the initial purification from the ore, and a 10% efficiency which is 200x whatever ratio you are thinking with U-235 or other extant radioactive processes.

$100-$300 kg for U-238, even in our pre-stellar tech.

http://nuclearinfo.net/Nuclearpower/WebHomeAvailabilityOfUsableUranium

Arguably the ND is sucking down power to force fission, but they aren't exactly power hogs for projecting the 'shedding field' presumably at least 50 km off, this is a higher rate of neutron shedding but MUCH shorter projection range and concentration.

What's not a payoff now can be with cheaper tech.

And re: oxidizer, again limited thinking in terms of just current mechanical forms. What about bioprocessing, engineered life that processes the carbons out?

 

[aramis]

Er.

I'm assuming U-238, which is a plentiful radioactive relatively speaking so you just have the initial purification from the ore, and a 10% efficiency which is 200x whatever ratio you are thinking with U-235 or other extant radioactive processes.

$100-$300 kg for U-238, even in our pre-stellar tech.

http://nuclearinfo.net/Nuclearpower/WebHomeAvailabilityOfUsableUranium

Arguably the ND is sucking down power to force fission, but they aren't exactly power hogs for projecting the 'shedding field' presumably at least 50 km off, this is a higher rate of neutron shedding but MUCH shorter projection range and concentration.

What's not a payoff now can be with cheaper tech.

And re: oxidizer, again limited thinking in terms of just current mechanical forms. What about bioprocessing, engineered life that processes the carbons out?

As I said, breeder reactor.

 

[Straybow]

Liquid Flouride Thorium Reactor

Look it up. Inherently stable design, literally makes its own fissionable fuel (U233) from mildly radioactive source (Th232).

Thorium is actually more abundant in Earth's crust than lead

 

[Straybow]

I'm not certain that the tetraflouride is stable enough to make a gas core reactor, but assuming so an inherently stable design would be tricky since the liquid salt would require a smaller volume for criticality.

 

[aramis]

The nice thing about the molten salt reactors is that the thermal working fluid is also catalyzing the fission process - if it's not there, the fuel stops fusing, so if it overheats, it self-moderates.

 

[Timerover51]

Liquid Flouride Thorium Reactor

Look it up. Inherently stable design, literally makes its own fissionable fuel (U233) from mildly radioactive source (Th232).

Thorium is actually more abundant in Earth's crust than lead

I seem to remember reading somewhere that India has experimented with a thorium breeder reactor, but I am not positive about that. I know that there was some research done in the late 1970s on the subject, and it does make quite a bit of sense. One problem is that the critical mass for U-233 is on par with that of Pu-239, so a design gets a bit trickier.