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Do we actually need SD(P)s?

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Re: Do we actually need SD(P)s?
Post by Theemile   » Thu Apr 02, 2020 3:07 pm

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Somtaaw wrote:They definitely use Hydrogen because it's even more available than Helium, and they use it because that one fuel source is also used in multiple locations. Specifically, it's the fusion reactor bunkerage for the starships themselves and their emergency thrusters, it's used in pinnaces & assault shuttles for thrusters and fuel for both fusion plants (hip pockets for the pinnaces, miniaturized ones for the assault shuttles).


It's also described during one of Honor's dinner parties with High Ridge as PM, by Henke that Honor's strategy at Hades during her final action (when she came out of the sun), that she used so much hydrogen for her "no wedge" burn for intercept, if she had to fight normally Honor's whole fleet might have run out of power mid-fight and thereby lost their wedges.

And when Honor's pinnace was shot down by the Armsmen working for Steadholder Burdette (Flag in Exile) there were 2 sets of hydrogen fuel tanks. One set were on ejectible fuel pods which caused big explosions upon impacting the surface (after the pinnace had already crashed), and the second set were deep inside the hull and they blew up due to fires. This heavily suggests they do in fact keep the hydrogen as uncompressed gas, since they had time before the fires & hydrogen gas mixed and blew the entire pinnace up. If it were compressed hydrogen, Honor would have been dead, still inside the crashed pinnace before she ever even realized she was on the surface.


If memory serves, Honor had left 8 hours remaining on the BCs and 6 for the CAs. Enough for a fight, but no way to run.
******
RFC said "refitting a Beowulfan SD to Manticoran standards would be just as difficult as refitting a standard SLN SD to those standards. In other words, it would be cheaper and faster to build new ships."
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Re: Do we actually need SD(P)s?
Post by ThinksMarkedly   » Thu Apr 02, 2020 5:01 pm

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Somtaaw wrote:They definitely use Hydrogen because it's even more available than Helium, and they use it because that one fuel source is also used in multiple locations. Specifically, it's the fusion reactor bunkerage for the starships themselves and their emergency thrusters, it's used in pinnaces & assault shuttles for thrusters and fuel for both fusion plants (hip pockets for the pinnaces, miniaturized ones for the assault shuttles).


Indeed, hydrogen is more available than helium (10x more by count, 3x more by mass). But there's still sufficient helium in gas giants to make Helium-3 fusion reactors economically viable. Not to mention you could extract them from the stars themselves (and in the process lengthen the life of your star).

Gas thrusters can use helium too, though of course that won't be as efficient as hydrogen, with the specific impulse of helium being lower. But again, economically viable and possibly worth it to use an inert, noble gas than the very reactive hydrogen.

It's also described during one of Honor's dinner parties with High Ridge as PM, by Henke that Honor's strategy at Hades during her final action (when she came out of the sun), that she used so much hydrogen for her "no wedge" burn for intercept, if she had to fight normally Honor's whole fleet might have run out of power mid-fight and thereby lost their wedges.

And when Honor's pinnace was shot down by the Armsmen working for Steadholder Burdette (Flag in Exile) there were 2 sets of hydrogen fuel tanks. One set were on ejectible fuel pods which caused big explosions upon impacting the surface (after the pinnace had already crashed), and the second set were deep inside the hull and they blew up due to fires. This heavily suggests they do in fact keep the hydrogen as uncompressed gas, since they had time before the fires & hydrogen gas mixed and blew the entire pinnace up. If it were compressed hydrogen, Honor would have been dead, still inside the crashed pinnace before she ever even realized she was on the surface.


Right, I do remember now that the bunkerage is specifically mentioned to be of hydrogen.

Given that helium is readily available and has no such volatility, one would expect that they use hydrogen only because the safety measures are more than adequate to compensate for the increased risk.
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Re: Do we actually need SD(P)s?
Post by ThinksMarkedly   » Thu Apr 02, 2020 5:04 pm

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Theemile wrote:If memory serves, Honor had left 8 hours remaining on the BCs and 6 for the CAs. Enough for a fight, but no way to run.


And yet they still accelerated hundreds of thousands of tons of warships at hundreds of gravities using nothing but old-fashioned rockets. The Physics of this battle must be glossed over.
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Re: Do we actually need SD(P)s?
Post by cthia   » Thu Apr 02, 2020 5:15 pm

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Theemile wrote:
cthia wrote:Oops.

5%?...4?...3? Heck, I give up.

I've seen naval accommodations; it's why I said sardine cans upstream. (Albeit aboard the oldstyle battleships, with no air conditioning and no women). Speaking of women, the Honorverse has so many women and I was thinking they would have separate quarters and separate facilities. Due to your incredulity, I do remember Helen's conversations with the crews, and they were not separate. I was also factoring in the space saved by the use of pods and other general automation. Again, lots of space must have been wasted to be able to gut a ship.

Whatever is responsible for the eggshell factor is the only thing left to account for the capital gains in available space for the design. (Which I do remember was explained, somewhere.) Anyway, even if the women were separate that wouldn't have significantly added to the footprint either.

I did think Honorverse accommodations would be a bit better. Again, until I remembered Helen. (Poor Grayson women...and their armsmen's apoplexy.) Well, more than a bit better as far as environmental systems. The only thing left to explain the sudden windfall of available space to fit pods has to be losing the battle steel and dampening - the thing that turns them into eggshells. Must have been a heckuva lot of battle steel, but bulkheads were only feet thick, as I recall, Not yards. Anyways, I give up the ghost, and the hunt for Red October.


The to biggest contributors to the void we call a pod bay are the missile magazines and the missile feed tubes. The Magazines were nothing but a large volume with racks of missiles, control wiring, plasma plumbing, and automated robotics fetching the appropriate missile to each feed tube. The Feed tubes were, well, tubes to each launcher, with armored cofferdam doors periodically to keep blasts from sneaking up the tunnel unopposed. SDs carried 15-30 thousand, 130 kton missiles, each the size of a large shipping container - remove those and you have (literally) tons of space to play with.

But it had to be significantly more than that. Significantly. Because removing all of that stuff would not have contributed to the eggshell factor. None of that stuff was that crucial to the structure of the ship.

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Re: Do we actually need SD(P)s?
Post by Galactic Sapper   » Thu Apr 02, 2020 5:46 pm

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Somtaaw wrote:And when Honor's pinnace was shot down by the Armsmen working for Steadholder Burdette (Flag in Exile) there were 2 sets of hydrogen fuel tanks. One set were on ejectible fuel pods which caused big explosions upon impacting the surface (after the pinnace had already crashed), and the second set were deep inside the hull and they blew up due to fires. This heavily suggests they do in fact keep the hydrogen as uncompressed gas, since they had time before the fires & hydrogen gas mixed and blew the entire pinnace up. If it were compressed hydrogen, Honor would have been dead, still inside the crashed pinnace before she ever even realized she was on the surface.

I'm almost certain the fuel stores that exploded when the fire reached them were more conventional rocket fuel rather than simple hydrogen gas stores for fusion thrusters. They were intended as fail-safe chemical thrusters, and the explosion described is more akin to a more conventional rocket fuel explosion rather than a hydrogen deflagration (which would depend on atmospheric oxygen rather than being fed by the oxidizer in a conventional rocket fuel). Certainly that explosion is vastly larger than a hydrogen tank of the size described could fuel.
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Re: Do we actually need SD(P)s?
Post by Galactic Sapper   » Thu Apr 02, 2020 6:06 pm

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Somtaaw wrote:Those 2 sources alone probably account for a considerable amount of the "empty space" we think Honorverse ships have to spare, since zero modern ships whether surface or submarine have those needs.

You're missing yet another elephant in the room (hull, actually). My inclusion of the Ohio in tonnage per man was intentional. Imagine a missile sub that carried 240 SSBN's with the same crew size as an Ohio and you'll begin to understand te ratio of machinery to men common to all Honorverse warships, with or without advanced automation.

Just the missiles of a Roland contribute significantly to the tonnage per man. A mark 16 is about 100 tons and the ship carries 1.5 missiles per crewman. Countermissiles add another 12 tons or so each, and the ship carries hundreds of them.

Sag C's carry about 3 Mark 16's per crewman and Nikes are even worse. Several hundreds of tons of the ship mass per crewman
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Re: Do we actually need SD(P)s?
Post by Jonathan_S   » Thu Apr 02, 2020 6:07 pm

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ThinksMarkedly wrote:I don't think a hydrogen explosion is likely, as explained above. However, if the bunkers do store a compressed gas, whether it's deuterium, helium, rupturing the bunker could cause explosive decompression, which would further rip open the hole created by the projectile. That's considerable damage. A water tank wouldn't nearly as much damage, as I don't think it would store water under high pressure. However, it would sublimate when exposed to vacuum.

Though if you hit a large water tank with a giga- to exawatt energy beam you'll probably get an impressive steam "explosion" from it.
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Re: Do we actually need SD(P)s?
Post by ThinksMarkedly   » Thu Apr 02, 2020 10:41 pm

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Jonathan_S wrote:Though if you hit a large water tank with a giga- to exawatt energy beam you'll probably get an impressive steam "explosion" from it.


How long do the regular graser beams last? A millisecond? An exawatt graser beam would deliver a petajoule of energy. 1 kg (1 L) of water needs roughly 4.2 kJ of energy to increase 1 K in temperature. So to go from room temperature to boiling (some 80 K), you need 336 kJ/kg. One PJ of energy could (literally) vapourise 2.97 billion kg of water = 2.97 million tonnes.

But not all of the energy is delivered to the water. First, it's dissipated before even reaching the hull. Second, it dissipates sublimating the hull itself. Third, water is a more or less poor heat conductor, so the beam would flash-boil only the water immediately surrounding the beam. And fourth, the beam would continue to heat the steam itself, which is an even poorer heat conductor. It would probably go all the way to plasma, at which point it becomes a good heat conductor.

But yes, such a steam would explosively expand. The only thing is that it would follow the path of least resistance and expand mostly through the holes created by the beam (axially), instead of through the rest of the water tank.

Then again, what we described for water is pretty much true for any solid or liquid part of the ship. The biggest damage of a graser beam is to turn the matter it hits into a beam of plasma that will continue to do damage.
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Re: Do we actually need SD(P)s?
Post by Loren Pechtel   » Thu Apr 02, 2020 10:54 pm

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kzt wrote:
Loren Pechtel wrote:
Of course you can saturate an old-school ship. I'm assuming the defenders are aware of what's going on and counterdesign--and I'm saying the podnaught design gives up more than the increase defenses to counter a podnaught. An innovation that might very well be useful in war due to the surprise factor isn't so useful in peacetime because your enemies will see what you're up to and counterdesign.

The one place where it might be of value is a fleet action if they could concentrate fire on a single ship--but my impression of the old fashioned missiles is that wasn't really how it worked. At substantial range you were only hoping to hit the enemy, not a particular ship.

I'm not convinced that anyone would react until someone they care about gets hammered by these crazy new ships.

The scientist has 32 tubes, with an implied 30 second cycle time. So squadron fires 256 missile every 30 seconds. They had 16 CMs and 32 PDLCs, so it appears reasonable to say they are designed to defend against themselves.

So they can handle 512 missiles per minute. A single BC(P) can deliver 240 missiles per minute. So a squadron of them delivers almost 4 times the missiles they are designed to handle. They go winchester after like 5 minutes, but each will have fired almost 3000 capital ship missile.

So even without trying to target just one ship the volume of fire distributed across all the Scientists seems likely to result in a very bad day for them, which will get worse then the SDs the BCs are escorting are included and then they close to energy range on the damaged fleet.

Fire control is an issue, but I suspect that not so much at SDM range.


You're still missing my point. Yes, pod ships defeat current designs. What I'm saying is that adding enough PD to those Scientists to let them defend against podlayers will take less away from them than was taken from the pod layers. A force of uprated Scientists will generally survive closing on a force of podlayers and will then blow it to bits when they reach energy range.

In the old school time each defense unit got multiple engagements against the incoming missiles and the missiles had to close to point blank range, making them easy pickings for the defense installations. Also, the missiles will be very close to each other in the last part of their flight, you are limited in how many missiles per salvo or they'll just destroy each other.

Now, however, the point defense gets only one engagement and must get a kill at far greater ranges. The missiles are also spread much farther apart, you can fire an awful lot more without fratricide.
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Re: Do we actually need SD(P)s?
Post by Loren Pechtel   » Thu Apr 02, 2020 11:00 pm

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Somtaaw wrote:Well surface ships don't have to budget tonnage towards "air tanks" of compressed Oxygen, or Air Scrubber plants. Even subs don't have to make a huge dedication to air scrubbing, because they can always employ water electrolysis on seawater to get brand new oxygen almost as needed.


No, they need good air scrubbing. Making oxygen isn't enough, not only would it be a major fire hazard but if you didn't reduce the pressure in the sub you would end up damaging everyone's lungs. Pure oxygen at sea level pressure has a safely limit of IIRC 16 hours.
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