Since I have two minutes, here are my humble predictions

[Skipjack]

I agree, but I think that below a certain size it will be difficult to justify the effort. After all a Polywell costs roughly a 100 mio USD (it will most likely be less after a while, but WB8 will be 100 mio USD, which is a number that we know).
So at what ship- size does a 100 mio USD engine make sense?
Of course the Navy does not care about money, but civilian naval ships have to be cost effective. There were a few superfreighters built that were nuclear powered. None of them was costeffective.
Anyway, I am not going to argue against this having a very beneficial effect on the marine transportation and navies of the world.
It will definitely have, all I am saying is that it is save to assume that anything that is efficiently powered by a fission reactor will be more efficiently powered by a polywell/BFR.... provided it works as we hope it will.

[djolds1]

I am not quite sure how large a ship has to be to accommodate an polywell that produces enough power.

Tell me how big the BFR is, and I will accommodate that space in the design of the ship. Most "Small Boys" (frigates and destroyers) in the U.S. Navy today are powered by LM-2500 gas turbine engines. 2-4 per vessel. $1Mill+ each (I don't know the real number, could be several million each). And they are basically jet engines, gulping gas down at prodigious rates...

Reference design in the QED "Booster" papers:

Core of 5m radius, 10,000MWth, pB11. Add +1m radius for the direct conversion system, 90% conversion efficiency.

PS. Are you the mumbles who worked up & released some figures on the Orion propulsion system some years back?

Duane

[MSimon]

Oh yeah, I agree it is important and a big deal for the navy. That is what I said after all! I am not quite sure how large a ship has to be to acommodate an polywell that produces enough power. One also must not forget that you need specialists to operate this thing. This is expensive and might not make sense for to small a vessel. But hey, I wont argue if someone wants to put it into a small vessel.

The specialist don't have to be trained as well as fission Nukes because the dangers are a lot lower. No significant stored fuel. Too much fuel in the reactor chokes the reaction. Too little starves it.

Keeping the reactor cool for 3 days after shut down is not a requirement. A minute or two should do it (15 minutes at most).

The key cost of the power generation is $1/ watt. Given an operating supply of 15 MW @$.50/ watt. The minimum size is probably around 15 MW net. i.e about 15,000 HP. Say around 5,000 HP for ships electrical needs and 10,000 SHP for propulsion.

[Skipjack]

Well, we will see. As I said, it is safe to assume that all fission reactors in ships will be replaced by BFRs, everything else depends on to many factors, that I do not dare to predict it. I think it might even be save to assume that they will retrofit many ships that had fission reactors for BFRs (those that can from floorplan, structure, etc POVs).
Question: How many people do you think will be needed to operate a BFR? I mean continuously and without interruptions?

[Jboily]

Oh yeah, I agree it is important and a big deal for the navy. That is what I said after all! I am not quite sure how large a ship has to be to acommodate an polywell that produces enough power. One also must not forget that you need specialists to operate this thing. This is expensive and might not make sense for to small a vessel. But hey, I wont argue if someone wants to put it into a small vessel.

A high power BFR is easier to produce, because the losses become negligible very quickly with size and power. The development cost of a commercial 100Mw reactor will be in the $B, but the production and operation cost will be much lower then power turbines.

I think minimal net power that would make sense with a direct p-11b conversion to electricity will be about 2MW, and could be contained within a cylinder 4 meter in diameter and 4 meter high. Most of the size requirement is because of the high voltage, the BFR WB radius would be less the ½ meter. A 20Mw reactor would not be much bigger, just a few centimeter more.

I think a small reactor would not cost much less then a bigger one. Past a critical size and power level, the cost would be scaled linearly with the power, like motors and transformers. Actually, the p-11b direct conversion BFRs will be much simpler to manufacture and operate then power turbines.

I think a small reactor would not cost much less then a bigger one. Past a critical size and power level, the cost would be scaled linearly with the power, like motors and transformers.

[blaisepascal]

Well, we will see. As I said, it is safe to assume that all fission reactors in ships will be replaced by BFRs, everything else depends on to many factors, that I do not dare to predict it. I think it might even be save to assume that they will retrofit many ships that had fission reactors for BFRs (those that can from floorplan, structure, etc POVs).

I think, after it's been proven to work and developed to the point of being able to put into ships, it's more likely that new ships (possibly all new Navy ship contracts) would be build than existing ships retrofitted.

Retrofitting an existing fission-powered ship may be too big a job to be worth doing.

Retrofitting large fossil-fueled ships might be worth it, assuming it can be made to fit in existing spaces. Someone recently mentioned a 5m-radius reactor, which would translate (including shielding, direct conversion layer, etc) into a minimum size of about 15-20m diameter. The Panamax width is 33m, so the reactor would occupy the middle-half of the width of the ship. I'm not a naval engineer, so I don't know if this is a problem. It seems like it would on smaller ships.

Question: How many people do you think will be needed to operate a BFR? I mean continuously and without interruptions?

My guess would be a very small number. Most monitoring functions would be computerized based on the millisecond control speed; there aren't many moving parts; etc. I doubt it would need constant human monitoring during day-to-day operations. If I were on board a military vessel and had the crew, I'd assign 6 people to it, so two would always be on duty. If I were on board a commercial vessel, it might be a part-time duty of one person. But these are guesses.

[Mumbles]

Of course the Navy does not care about money...

I would beg to argue that statement...

I'm in the Navy, and we worry about money every day! Whether it is reduced OPTAR (training funds - read fuel for airplanes and ships), or in my current acquisition job, managing the program budget throughout the FYDP (fiscal yeard defense plan). Let's just say everyone worries about money...

Be Safe
Mumbles

[Mumbles]

PS. Are you the mumbles who worked up & released some figures on the Orion propulsion system some years back?

Duane

Duane-
No, I have never discussed either of the Orion space propulsion systems - the nuclear rocket nor the current space capsule.

Be Safe
Mumbles

[djolds1]

Retrofitting an existing fission-powered ship may be too big a job to be worth doing.

Agreed. Fission reactors proper can be very compact. The electrical generation turbines are another matter.

Retrofitting large fossil-fueled ships might be worth it, assuming it can be made to fit in existing spaces. Someone recently mentioned a 5m-radius reactor, which would translate (including shielding, direct conversion layer, etc) into a minimum size of about 15-20m diameter. The Panamax width is 33m, so the reactor would occupy the middle-half of the width of the ship. I'm not a naval engineer, so I don't know if this is a problem. It seems like it would on smaller ships.

Did a quick check yesterday. The US Arleigh Burke class destroyers and foreign derivatives have beams of 18 to 20 meters, depending on the production batch.

The Direct conversion system is cited as being +0.5 to 1 meter radius. I defaulted to the larger figure for caution's sake. pB11 fuel should allow near zilch shielding. For a milspec system figure the tightest possible dimensions for the vacuum chamber (say +0.25m), the grids, and the DCS. Accept some inefficiency in return for effectiveness.

Someone remind me - the minimum pB11 grid is 3.5m radius, for the 100MW demonstrator, yes? If a conventional ship needs a 10,000 MWth/ 9000 MWe (10 GIGAWatts thermal, 9 GIGAWatts electrical) reactor any time in the next 20 years, I'll eat my sweaty used underpants on live webcast.

Diameter = 2*(3.5+0.25+0.5) = 8.5m

Question: How many people do you think will be needed to operate a BFR? I mean continuously and without interruptions?

My guess would be a very small number. Most monitoring functions would be computerized based on the millisecond control speed; there aren't many moving parts; etc. I doubt it would need constant human monitoring during day-to-day operations. If I were on board a military vessel and had the crew, I'd assign 6 people to it, so two would always be on duty. If I were on board a commercial vessel, it might be a part-time duty of one person. But these are guesses.

If anything goes wrong, it shuts down and all radioactivity goes *poof.*

No danger.

Now I think you can run DHe3 on the smaller radius DD scale grids. DD and DHe3 "burn" at nearly the same energies. Moderately higher neutronicity for DHe3 but nowhere near that of DT. The tighter reactor would probably be preferable for military systems. Would require some neutron shielding.

Duane

[Skipjack]

Mumbles, I am sorry that came over a little different from what I wanted it to sound. Lets say that when it comes to national security, money is less of an issue than for a commercial container cargo ship.
Assuming that you guys are right and it wont make sense to retrofit old nuclear powered ships with BFRs, then I would say that it will take even longer for BFRs to take over the fleet.
A nuclear aircraft carrier is in service for what? 50 years (the USS Enterprise will be by the time she is decomissioned)?
So that will take a while. Same goes for the nuclear subs. The USS Skipjack was in service for almost 40 years. This would mean that it would take at least 50 years from the point the first ship powered by a BFR will enter service until all ships in the navy are outfitted with this system. This sounds like an awful long time to me, especially when you assume a much much lower operating cost than nuclear or gas turbine propulsion.

[MSimon]

Mumbles, I am sorry that came over a little different from what I wanted it to sound. Lets say that when it comes to national security, money is less of an issue than for a commercial container cargo ship.
Assuming that you guys are right and it wont make sense to retrofit old nuclear powered ships with BFRs, then I would say that it will take even longer for BFRs to take over the fleet.
A nuclear aircraft carrier is in service for what? 50 years (the USS Enterprise will be by the time she is decomissioned)?
So that will take a while. Same goes for the nuclear subs. The USS Skipjack was in service for almost 40 years. This would mean that it would take at least 50 years from the point the first ship powered by a BFR will enter service until all ships in the navy are outfitted with this system. This sounds like an awful long time to me, especially when you assume a much much lower operating cost than nuclear or gas turbine propulsion.

Actually BFR could be refitted on carriers during refueling. I think they go 5 to 10 years between refuels now. The cores get loaded with B10 to reduce reactivity (prompt critical is such a nuisance) and make the cores last longer.

I think a refit is possible. We won't know until the WB-100 is glowing.

Submarine reactors are on the order of 60 to 100 MWth. The Enterprise used to have 8 reactors of that size. I think newer carriers have 2 with 4X the power out.

http://www.naval-technology.com/projects/nimitz/

The nuclear-powered carrier has two General Electric pressurised water reactors driving four turbines of 260,000hp (194MW) and four shafts. There are four emergency diesels of 10,720hp (8MW).

That is 800 MW at the shaft. Figure 2.4 GWth. For something in the Nimitz class.

[MSimon]

pB11 fuel should allow near zilch shielding.

Actually it is only about 1/2 as much as a fission reactor.

[MSimon]

I agree, but I think that below a certain size it will be difficult to justify the effort. After all a Polywell costs roughly a 100 mio USD (it will most likely be less after a while, but WB8 will be 100 mio USD, which is a number that we know).
So at what ship- size does a 100 mio USD engine make sense?
Of course the Navy does not care about money, but civilian naval ships have to be cost effective. There were a few superfreighters built that were nuclear powered. None of them was costeffective.
Anyway, I am not going to argue against this having a very beneficial effect on the marine transportation and navies of the world.
It will definitely have, all I am saying is that it is save to assume that anything that is efficiently powered by a fission reactor will be more efficiently powered by a polywell/BFR.... provided it works as we hope it will.

It all depends on the time value of the cargo. I believe the US Navy rents 40 knt supply ships.

[Skipjack]

40 knots? That seems pretty fast to me.
What supply ship makes 40 knots (sustained)?

[MSimon]

40 knots? That seems pretty fast to me.
What supply ship makes 40 knots (sustained)?

http://www.hydrolance.net/page9.htm

*

The listed speed in the article was 39 kt. The US Navy is renting such vessels for troop/vehicle transport.