Apollo defense possibilities

SWM wrote:

Jonathan_S wrote:Hmm. It occurs to me that a pure escort missile defense LAC should be within League construction capabilities.

Now if they don't make any breakthroughs in node development the LACs would be barely as fast as their wallers. That would make it more annoying to use them as a screen, but probably isn't a dealbreaker.

It's not the nodes that make Shrikes faster than destroyers--it is the power generator. Old-style LACs simply couldn't generate enough power to take full advantage of the acceleration their inertial compensators could handle. The breakthrough was the Grayson fission generators.

Just to nitpick, that's not what House of Steel seems to say (though I admit the other place that mentions the acceleration improvement, a passage in Honor Among Enemies, doesn't state why the old LACs had "weaker impeller wedges")

House of Steel wrote:Perhaps most notably, the Series 282 was the first LAC to mount an impeller ring powerful enough to accelerate it to the limits of its inertial compensator.

Is there somewhere else, that I'm not remembering at the moment, that said the problem was power production and not the nodes themselves?

Jonathan_S wrote:

SWM wrote:It's not the nodes that make Shrikes faster than destroyers--it is the power generator. Old-style LACs simply couldn't generate enough power to take full advantage of the acceleration their inertial compensators could handle. The breakthrough was the Grayson fission generators.

Just to nitpick, that's not what House of Steel seems to say (though I admit the other place that mentions the acceleration improvement, a passage in Honor Among Enemies, doesn't state why the old LACs had "weaker impeller wedges")

House of Steel wrote:Perhaps most notably, the Series 282 was the first LAC to mount an impeller ring powerful enough to accelerate it to the limits of its inertial compensator.

Is there somewhere else, that I'm not remembering at the moment, that said the problem was power production and not the nodes themselves?

Hm. The Cimeterre was almost as fast as the Shrike, and they did it without beta-squared nodes. There is no mention of using more powerful nodes. The difference in acceleration between Cimeterre and Shrike appears to be the improved inertial compensator, which Haven also did not have. The text says:

By ruthlessly suppressing the energy armament and accepting such a vast decrease in life support--and by eliminating over half of the triple-redundancy damage control and repair systems routinely designed into "real" warships--Clapp had managed to produce a LAC hull which came amazingly close to matching the performance of the Manties' designs. It's less efficient inertial compensator meant its maximum acceleration rate was more sluggish, but it was actually a bit more nimble and maneuverable than the observational data suggested the Manty LACs were.

The loss of the energy armament means less power consumption, which fits, but it is not clear how reducing redundancy and life support directly affects the acceleration of the LAC. It is possible they used the extra volume to build a bigger generator, but that is not stated. It could, instead, be that they used the volume to fit bigger nodes.

Since Haven had not made any developments in node design, it is clear that the limitation on old-style LACs was not that no one could build a good enough LAC node. So either the old wimpy acceleration was either a design choice, or it was because they couldn't fit big enough nodes, or they couldn't fit in enough power.

Remember, fusion plants generate more power than fission plants. If anything, a Cimeterre is overpowered with regards to its generation capability versus its energy requirements.

SWM wrote:

Jonathan_S wrote:Hm. The Cimeterre was almost as fast as the Shrike, and they did it without beta-squared nodes. There is no mention of using more powerful nodes. The difference in acceleration between Cimeterre and Shrike appears to be the improved inertial compensator, which Haven also did not have. The text says:
By ruthlessly suppressing the energy armament and accepting such a vast decrease in life support--and by eliminating over half of the triple-redundancy damage control and repair systems routinely designed into "real" warships--Clapp had managed to produce a LAC hull which came amazingly close to matching the performance of the Manties' designs. It's less efficient inertial compensator meant its maximum acceleration rate was more sluggish, but it was actually a bit more nimble and maneuverable than the observational data suggested the Manty LACs were.
The loss of the energy armament means less power consumption, which fits, but it is not clear how reducing redundancy and life support directly affects the acceleration of the LAC. It is possible they used the extra volume to build a bigger generator, but that is not stated. It could, instead, be that they used the volume to fit bigger nodes.

Since Haven had not made any developments in node design, it is clear that the limitation on old-style LACs was not that no one could build a good enough LAC node. So either the old wimpy acceleration was either a design choice, or it was because they couldn't fit big enough nodes, or they couldn't fit in enough power.

It's less mass. The redundant equipment and life support that was removed (air tanks and converters and air scrubbers, whatever life support in the Honorverse is) is less mass on the ship. It also saves on the power requirements for those systems. Less mass means an easier time accelerating and not having to power the systems, means they can use the power for other things.

Duckk wrote:Remember, fusion plants generate more power than fission plants. If anything, a Cimeterre is overpowered with regards to its generation capability versus its energy requirements.

It should, but there seem to be some weird scaling effects when you get down to LAC size.

I wouldn't be surprised either way if some future book or post from RFC picked either technology as implemented in LACs provided more power. (Although maybe you were pulling from the tech bible and this was the official word of weber answer)


Making fission plants win in power output in LACs would seem to require undersizing or throttling down the fusion plant significantly (presumably in a desperate effort to eek out acceptable endurance from their insufficient bunkerage). But like I said I wouldn't be surprised if we were told that was the case. (But equally wouldn't be surprised if we were told that fission plant equipped LACs had to be designed around a lower power budget)

We've already gone over this. Fusing H to He yields far more power by mass. Like 100 liters is equal to thousands of tons of refined plutonium.

kzt wrote:We've already gone over this. Fusing H to He yields far more power by mass. Like 100 liters is equal to thousands of tons of refined plutonium.

The question right now isn't energy per mass, but energy per second.

That, too, has been discussed, and Duckk is right that ship fusion generators give more power than LAC fission generators.

What I can't recall is whether the old LACs before Cimeterre and Shrike also used ship-sized fusion generators, or the smaller fusion generators used on pinnaces (which give less power than LAC fission generators).

SWM wrote:

kzt wrote:We've already gone over this. Fusing H to He yields far more power by mass. Like 100 liters is equal to thousands of tons of refined plutonium.

The question right now isn't energy per mass, but energy per second.

That, too, has been discussed, and Duckk is right that ship fusion generators give more power than LAC fission generators.

What I can't recall is whether the old LACs before Cimeterre and Shrike also used ship-sized fusion generators, or the smaller fusion generators used on pinnaces (which give less power than LAC fission generators).

I recall they used ship style GRAVMAKs.

But for the fission breakthrough to work there pretty much had to be some horrifically bad scaling issues cramming those fusion plants down into a LAC.
(Like way over half the power output getting eaten as overhead just to run the GRAVMAKs -- something like that)

Jonathan_S wrote:But for the fission breakthrough to work there pretty much had to be some horrifically bad scaling issues cramming those fusion plants down into a LAC.
(Like way over half the power output getting eaten as overhead just to run the GRAVMAKs -- something like that)

IIRC, a scaling problem has been confirmed, but the big advantage of the Fission-powered LACs is the space saved in bunkerage (fuel storage) and the increase in endurance not having to refuel every day permits.

Weird Harold wrote: but the big advantage of the Fission-powered LACs is the space saved in bunkerage (fuel storage) and the increase in endurance not having to refuel every day permits.

Which is where physics says "not so much". If you are refueling your fusion reactor every week you'd be refueling a fission reactor every hour.