STL: Alternate Energy Sources?

[gchuck]

I'm trying to design a STL colony ship, and need some input on size of the power plant, and some basic design parameters.

The plan is using some sort of 'non' fusion reactor with an extended life cycle. With a low power demand during flight operations.

Colonists in low berths, originating from Earth during the Vilani wars/pre-ROM period.

Any suggestions?

BTW: its for CT

 

[Proneutron]

what is your propulsion system? That will drive much of the answers

 

[gchuck]

what is your propulsion system? That will drive much of the answers

Low thrust, mainly. I figure some sort of ion/electron drive. Some thing without a lot of 'moving' parts and lots of longevity.

 

[Fovean]

Low thrust, mainly. I figure some sort of ion/electron drive. Some thing without a lot of 'moving' parts and lots of longevity.

Unfortunately not covered in CT, at least to my knowledge. I suppose we could work out rules for decimal-level M-Drives and say they are non-gravitic?... maybe in the 0.01G to 0.1G range?

Although there may be something in Striker which better fits the bill.

 

[mike wightman]

A very large thorium based fission reactor...

 

[gchuck]

Unfortunately not covered in CT, at least to my knowledge. I suppose we could work out rules for decimal-level M-Drives and say they are non-gravitic?... maybe in the 0.01G to 0.1G range?

Although there may be something in Striker which better fits the bill.

The tables in Striker are (at a cursory glance) helpful, but lacking any kind of fission reactors.

Maybe a Bussard ramjet might be the way to go, with jettison-able hydrogen tanks for initial accel.

 

[Proneutron]

Low thrust, mainly. I figure some sort of ion/electron drive. Some thing without a lot of 'moving' parts and lots of longevity.

With that small of Delta-V you'll need either a generation ship or "cold sleep". Which you pick will drive your power and other design considerations.

 

[mike wightman]

Initial thrust will be via beamed power - check out the stelaser propulsion system that Isaac Arthur is a great fan of.

The thorium reactor is for long duration power while out of range of the lasers.

For deceleration the thorium reactor will power an ion engine.

Buzzard ramjets are pure science fantasy.

 

[Proneutron]

The thorium reactor is for long duration power while out of range of the lasers.

Thorium is a short lived fuel compared to enriched uranium like that used in nuke subs. Not a good choice for STL ships

 

[Straybow]

No, Th is not short-lived: half-life is 14 billion years. Uses neutrons from reactor to become Th233 which decays into U233 in a few weeks. U233 fuels reactor. That means large quantities of "fuel" can be stored as Th, nearly inert, for unlimited time, and brought online on demand. It can also be used as radiation shielding.

 

[Proneutron]

No, Th is not short-lived:

I'm not talking about it as itself as itself. As a viable "hot" fuel. smh

 

[gchuck]

So some sort of long duration fission pile, with damn near infinite redundancy,
to maintain the 'colonists' in cold sleep. Minimal constant life support.

Open structure, similar to the Deep Exploration ships from Babylon 5, or maybe Discovery from 2001. Girders and pods and shielding, oh my.

An easy kilometre in length, with nuclear missiles for defense against navigational hazards. Several shuttles and lots of survey drones.

Have I missed anything?

 

[Proneutron]

So some sort of long duration fission pile, with damn near infinite redundancy,
to maintain the 'colonists' in cold sleep. Minimal constant life support.

Open structure, similar to the Deep Exploration ships from Babylon 5, or maybe Discovery from 2001. Girders and pods and shielding, oh my.

An easy kilometre in length, with nuclear missiles for defense against navigational hazards. Several shuttles and lots of survey drones.

Have I missed anything?

Sounds good

 

[mike wightman]

Thorium is a short lived fuel compared to enriched uranium like that used in nuke subs. Not a good choice for STL ships

I think you may need to go check up on what is meant by a thorium reactor...

 

[mike wightman]

I'm not talking about it as itself as itself. As a viable "hot" fuel. smh

That doesn't make any sense, it is a precursor to the 'hot fuel' as you put it.
Thorium absorbs neutrons to become the fuel - go and do some background reading on thorium fuel cycle and thorium nuclear reactors.
It has many advantages over other nuclear fuels, and you are going to need a lot of it for the deceleration at the far end.

 

[Straybow]

I'm not talking about it as itself as itself. As a viable "hot" fuel. smh

Well, that's not what you said. And I still think you're mistaken.

U233, half-life 160k years. I don't think your generation ship is going to take a hundredth of that to get to the destination... so I don't know what you mean about not being a viable "hot" fuel.

The reason why the AEC rejected U233 reactor licensing is because they wanted overlap between civilian and military uranium processing and infrastructure. U233 makes lousy warheads because "poisons" in the decay chain would require frequent reprocessing of pits, and because of fast neutron problems for warhead design.

With Th232 as the latent fuel source, U233 spends little time outside the reactor that would build up poisons, and the poisons that build up in LFTR either precipitate/gas out or are easily removed from the liquid fuel or from the cooled salt.

All other designs that use solid fuel (pellets in rods, or in capsules for pellet beds) have poison problems. A conventional reactor has to reprocess fuel after as little as 1% of the fissionable material has be used. With LFTR, it is the reverse. Almost all the fissionable material can be used up before drawing off the fuel mix to process out the decay or fission products.

In a generation ship, the productivity doesn't really matter for Th. It is so plentiful the used fuel can be set aside for a few weeks to allow Th233 to become U233, the U233 can be extracted as a UF6 gas, and the rest simply ejected.