Attacking Darius:

Jonathan_S wrote:But, of possible interest to this sub-thread, it specifically mentions them using "plasma accelerators" driven by their fission plant "for gravitic conversion" (which I think means powering the impeller nodes) and to power their energy mounts)

You may have just supplied the method of propulsion for the superheated plasma, instead of pressure.

cthia wrote:It is certainly possible that the seed plasma needs to come from another reactor. But if that is true then it means that the smaller ships which only have two reactor's can literally end up dead in the water needing a jump from another ship.

Yes, it's possible.

But I imagine that all warships carry a "starter motor" of some sort that can be used to heat up the plasma for the fusion reactors. Civilian models may not have those, for the mass penalty, and because they can count on shore power somewhere, or they can call triple-A.

That would mean it's a two-stage process, like for aeroplanes. Usually, they draw shore power to start their APUs, but they can get started from cold, using batteries or, if in flight, using the ram-jet turbine. When they come to a small airport that isn't going to provide them with power, then they use the engines to start the APU, so they use less fuel and don't drain batteries.

ThinksMarkedly wrote:

cthia wrote:It is certainly possible that the seed plasma needs to come from another reactor. But if that is true then it means that the smaller ships which only have two reactor's can literally end up dead in the water needing a jump from another ship.

Yes, it's possible.

But I imagine that all warships carry a "starter motor" of some sort that can be used to heat up the plasma for the fusion reactors. Civilian models may not have those, for the mass penalty, and because they can count on shore power somewhere, or they can call triple-A.

That would mean it's a two-stage process, like for aeroplanes. Usually, they draw shore power to start their APUs, but they can get started from cold, using batteries or, if in flight, using the ram-jet turbine. When they come to a small airport that isn't going to provide them with power, then they use the engines to start the APU, so they use less fuel and don't drain batteries.

Besides, if this is true, you would never turn off both reactors, one always being kept on while work was done on the 2nd. The worry would single reactor Merchies.

But the current state of single reactor ships just shows the maturity of the technology. the loss of the reactor is not a problem worth worrying about.

In a similiar logic, 4 engine passenger planes were previously dictated on Earth for intercontinental flight. In the 60's 4 or 5 crew members on the flight deck were required to to fly planes. (2 Pilots, 1 navigator, 1 radio operator and 1 engineeer.) Now, double engine planes with 2 crew members can fly nearly 10 thousand miles, why, the Engines are powerful enough and reliable enough that a single engine can limp a plane along reliably, and modern electronics made the nav, radio operator, and engineer positions unnecessary.

ThinksMarkedly wrote:

cthia wrote:It is certainly possible that the seed plasma needs to come from another reactor. But if that is true then it means that the smaller ships which only have two reactor's can literally end up dead in the water needing a jump from another ship.

Yes, it's possible.

But I imagine that all warships carry a "starter motor" of some sort that can be used to heat up the plasma for the fusion reactors. Civilian models may not have those, for the mass penalty, and because they can count on shore power somewhere, or they can call triple-A.

That would mean it's a two-stage process, like for aeroplanes. Usually, they draw shore power to start their APUs, but they can get started from cold, using batteries or, if in flight, using the ram-jet turbine. When they come to a small airport that isn't going to provide them with power, then they use the engines to start the APU, so they use less fuel and don't drain batteries.

Civilian models can start their own reactors, or they're dead if they suffer a reactor trip between the stars.

ThinksMarkedly wrote:But I imagine that all warships carry a "starter motor" of some sort that can be used to heat up the plasma for the fusion reactors. Civilian models may not have those, for the mass penalty, and because they can count on shore power somewhere, or they can call triple-A.

That would mean it's a two-stage process, like for aeroplanes. Usually, they draw shore power to start their APUs, but they can get started from cold, using batteries or, if in flight, using the ram-jet turbine. When they come to a small airport that isn't going to provide them with power, then they use the engines to start the APU, so they use less fuel and don't drain batteries.

Or airplanes using even odder things. The B-52's "cart start" for example - where they used the MXU-4A solid propellant engine starter cartridge; basically a small (and very carefully designed) solid rocket motor. Igniting it to very rapidly produce sufficient (not too) hot gas to spin up the turbines to the point where they can self-sustain. (And creating an impressive cloud of black smoke as a byproduct)

Useful if you need to emergency scramble your strategic bombers without keeping their APUs running or leaving them all simultaneously hooked to shore power.

Apparently those same cartridges could also be used to start the F-4C Phantom II, the F-100 Super Saber, F-105 Thunderchief, F-111 Aardvark, and KC-135 Stratotanker; though most of those planes are long out of inventory.

Theemile wrote:Besides, if this is true, you would never turn off both reactors, one always being kept on while work was done on the 2nd. The worry would single reactor Merchies.

I was thinking of battle damage. You don't want to get a destroyer or light-cruiser stranded after a battle if both reactors shut down, if you can relight them.

But as you said, it might be that this condition is so uncommon, that the damage required to cause both to scram is so great, that it's not worthwhile having the starter motor aboard.

But the current state of single reactor ships just shows the maturity of the technology. the loss of the reactor is not a problem worth worrying about.

In a similiar logic, 4 engine passenger planes were previously dictated on Earth for intercontinental flight. In the 60's 4 or 5 crew members on the flight deck were required to to fly planes. (2 Pilots, 1 navigator, 1 radio operator and 1 engineeer.) Now, double engine planes with 2 crew members can fly nearly 10 thousand miles, why, the Engines are powerful enough and reliable enough that a single engine can limp a plane along reliably, and modern electronics made the nav, radio operator, and engineer positions unnecessary.

Wasn't the Lockheed Constellation dubbed "the most reliable tri-engine" because one was always faulty? I know I've seen this phrase before, but I can't find it any more to confirm it was about the Connies.

The interesting thing is that the twin-engine reliability isn't THAT old. Just look at the fact that Airbus designed the A380 with 4 in the 1990s. Twin-engine jets were limited to 120 minutes between diversion airports well into the 2000s, as not all authorities accepted 777's ETOPS-180 rating. Now, the A350 has ETOPS-370. The other thing is that many of those newer aircraft can actually fly pretty well with just one engine, at least as far as required to reach safe harbour.

But that's civilian craft. They're not expected to go into battle and have extreme redundancy to cope with battle damage. They have redundancy (like three separate hydraulic systems), just not to the extreme.

Loren Pechtel wrote:Civilian models can start their own reactors, or they're dead if they suffer a reactor trip between the stars.

That's the question Theemile is posing above: how likely is that to happen? Because if the reliability of a reactor is over 5 nines with proper maintenance, then they're not going to carry the starter motor.

Five nines, or even eleven nines, isn't 100%. It means there's still a non-zero chance of it happening, even for the five-way redundant Galactics of Out of the Dark (their MTBF was measured in centuries, but was finite). If it does happen, then that crew is going to die, but that's no different than a twin-engine aeroplane suffering a dual-engine failure further than its glide path to any safe landing. But it's so unlikely that the passengers and crew accept the risk.

And besides, the starter motor is not a guarantee either. A double fault could mean that it also fails when needed.

Dauntless wrote:don't know about the rest of this but artificial grav was not used by most of the RMN in this time. As far as I know only HMS Casey used it, the rest of the RMN used spinning sections for gravity.

no idea how this affects things but the ships in this battle are not the ships of Honor's RMN where every ship has grav plating for artificial Gravity.

cthia wrote: Consider that the reactor needs hot plasma to kickstart itself. It cannot heat the plasma in which it uses to feed itself if the reactor is cold.

Therefore, some other method must be available to heat the plasma. And I see no point in having superheated plasma coursing thru the veins of the ship until it is needed at specific nodes.

That goes double for having superheated plasma just outside the reactor's containment area that could receive damage and cause a dangerous chain reaction in "arm's length" of the reactor.

Therefore, I see no need for the reactor to be pushing out super hot plasma (rather than simply the neutral gas to make it) if it is not needed so soon in the effluent flow.

Also, I am not suggesting that the electromagnetic current can contain the plasma, rather than simply super heat it, whereas pressure or some other mechanism moves it along.

The passage about the reactor possibly blowing when the surge of energy hits also verifies my worry about a long fuse acting as a trigger and leading back to the reactor.

There is a lot more that can be gleaned and posited from that textev.

Add to this what dauntless posted one klick upstream!

These two posts raise a fundamental problem for me: why are there plasma pipes running through the ship?

From Dauntless: if they did not have artificial gravity containment, then what keeps the plasma in the pipes? Electromagnetic forces only work if the plasma is charged and has problems unless every hot atom is ionized.

From Cthia: if the plasma is not supplied hot from the reactor, then why not generate it only where it is needed?

And yet we know there are plasma pipes, even in the "Manticore Ascendant" days. Beats me.

On the question of a starter reactor: could a main reactor be started from the output of a reactor using laser initiated fusion? In not, then is it possible that all reactors in a ship are only shut down when that ship is at a service point; where outside plasma can be supplied. We know that there are points where plasma can be supplied outside the hull (RFC talked about plasma outlets). So in an emergency could one ship jump start another?

No, there is a lot 'this does not follow' in some of the deeper issues of the honorverse.

There is a reason they don't use advanced batteries. A modern battery can store somewhere between 0.1-0.25 KWhr per kilo. Assume honorverse batteries are 2 orders of magnitude better, so 25 KWhr kilo. So 90 megajoule per kilo seems like a good ballpark. That's roughly equal to a kilo of TNT. So they want a lot more power

The plasma has to be highly energetic to provide the kind of power density that is talked about. You can't do this with the plasma power density of the solar corona. Highly energetic means very damn hot. And, since energy capacity of something hot is dependent on mass, it also has to be dense. This means under significant pressure. Very hot and dense under high pressure means that it really wants to expand.

Reactors doing H-H fusion are running at 15 million K and a density of 160 tons per cubic meter, and produce little power per unit mass. To run efficiently (like honorverse ships need) they need to run at closer to 100 million K.

So basically the plasma pipe is full of stellar core material, but much hotter than an actual star core. Leaks are umm, bad.

kzt wrote:Reactors doing H-H fusion are running at 15 million K and a density of 160 tons per cubic meter, and produce little power per unit mass. To run efficiently (like honorverse ships need) they need to run at closer to 100 million K.

So basically the plasma pipe is full of stellar core material, but much hotter than an actual star core. Leaks are umm, bad.

FYI the HMS Minotaur diagrams at the end of EoH and AoV say her reactors, item (14), are
"Isler Corporation GRAVMAK (Gravity-Magnitnaya)
              Fusion Reactor Burning Hydrogen/Boron-11 Mix"

But the two copies of that diagram appear to be literally the only place Boron is mentioned in the books -- and I've no idea how the temperatures of Hydrogen/Boron-11 would compare to H/H. (Though the boron fuel should be significantly lower in neutron production)