?

Thinksmarkedly wrote:I might agree but that's irrelevant because it's not two thirds of the volume. From the drawings we've seen, the three drive rings together occupy at a third of the missile's volume. So shedding two of them would reduce your volume by a quarter or a fifth.

penny wrote:That calculation might be a bit premature. The volume occupied by the drive rings does not necessarily indicate the volume of the missile that would be rendered inert when a particular drive ring is spent. As a matter of fact, don't stages (even in multi-drive missiles) have differently rated burn times? Anyway, I would hesitate associating and guestimating the inert volume of a missile based on the volume occupied by its drive ring.

As an example that is included solely to accompany my thoughts.

Five-Segment Solid Rocket Booster The SLS booster is the largest, most powerful solid propel-lant booster that will ever fly. Standing 17 stories tall and burning approximately six tons of propellant every second, each booster generates more thrust than 14 four-engine jumbo commercial airliners. Together, the SLS twin boosters provide more than 75 percent of the total SLS thrust at launch.

If our very own booster rockets burn that much fuel every second then surely the infrastructure associated with the far longer burns of HV missiles (capacitors and accompanying electronics) occupy a formidable volume. Multidrive missiles got much longer than the volume occupied by the drive rings over their long history of development. No?

But yeah, I might be a tad bit overly optimistic about a missile possibly shedding two thirds of its volume. But I've always been an open-minded sort. And as stated upstream, I will remain optimistic about the volume of a missile that might be shed if some entity were to specifically design its missiles to separate after a spent stage. Capacitors, associated electronics and other gizmos just might be as volume intensive as the chemical fuel aboard our very own booster rockets since the range and burn time of the missiles in the HV are far longer. So who knows. I shall remain opti– … enthusiastically optimistic.

What is the burn time of the various stages of multistage missiles? Anyone know?

Jonathan_S wrote:But that's not how Honorverse missiles work.
The cataphract, being a 2-stage missile does appear to drop it's SDM-derived first stage when it launched the CM-derived stage grafted onto it's nose -- and the Cataphract is also the only missile we know of that can have more than 1 acceleration during it's flight.
(The MWW talked about a possible 4-drive system defense missile for the RMN which had a CM derived final drive; and so would have had differing accelerations. But we've never seen such a thing actually deployed)

But for everybody else's DDMs and MDMs you have to set all drives to the same settings before launch. MWW responded to a thread speculating about mixed acceleration launched and said, in effect, 'nope. they currently can't work that way. there's some effect that prevents you from setting an adjacent drive ring to a different acceleration setting'

I know they don't currently work that way, and I know that currently all drives have to be set for the same acceleration; but again, that might be the effect caused by the static nature of the compensator whose compensation effect cannot be changed on the fly because the volume to be compensated is normally not going to change. But it will change if spent drives are separated. IOW, perhaps they might be made to work that way. If a Cataphract can do it, why can't any multistage missile, and eventually MDMs. Anyway, when the range of multi-drive missiles changed, the drive rings didn't get bigger, only the missile body did. No? Is there a link to one of MaxxQ's drawings?

Jonathan_S wrote:So for DDMs (or MDMs) you could have all drives all set to half-power (which is their normal usage); giving (for the RMN) 46000g for up to 180 seconds each. Or you could have all drives set to full-power; giving 92000g for up to 60 seconds each.

Half power:
DDM
29.2 million km continuous powered range
0.54c terminal velocity

MDM
65.7 million km continuous powered range
0.81c terminal velocity

Full power:
DDM
6.4 million km continuous powered range
0.36c terminal velocity

MDM
14.6 million km continuous powered range
0.54c terminal velocity

Thanks for the trouble, but I was more interested in whether all drive stages had the same capability on any particular setting. IOW, are all stages equal? From your post I gather they are.

Jonathan_S wrote:I say "up to" because while you can't pick a different acceleration once the drive is active you're free to turn a drive off early; and I assume that would apply to any of a DDM or MDM's drives. It's just that you can't ever turn it back on; so running less than the maximum time just gives you shorter range and lower velocity. The only drive that isn't normally run for its full duration is the final drive; and that's just because most engagements aren't made at the maximum possible range -- so the missile reaches its target with time still left on its final drive.

RMN missiles in particular aren't going to be shedding significant volume if they drop spent drive rings because, in almost the complete opposite of your solid rocket fuel example, they use the same power source (the microfusion power plant) to power all their drives. The reactor is way bigger than the fuel tanks; so even if you split the fuel into 2 or 3 tanks so you could drop an empty tank with its expended drive ring they'd still take up a pretty small fraction of the missile volume compared to the reactor itself.

You certainly guessed where I was headed. A smaller reactor servicing each stage.

Jonathan_S wrote:(Other people's capacitor powered MDMs could be a bit different, as you might be able to split into 3 capacitor banks -- one per drive -- and drop them when empty. Though even that's likely requiring more initial space in the missile as 3 separate banks each run to empty are going to be less efficient at storing energy that one big capacitor bank that's shared across the drives.

I don't think I can agree with the less efficient notion. Power is usually loss with distance. Hence, step-up transformers. A more contained setup should be more efficient, not less. That is presently the case with all of our current applications and electronics.

At any rate, what exactly is contained inside the huge volume of the separate stages of multi-drive missiles that can't be discarded. At any rate, only multi-drive missiles might be off the table, not multistage missiles.

penny wrote:I know they don't currently work that way, and I know that currently all drives have to be set for the same acceleration; but again, that might be the effect caused by the static nature of the compensator whose compensation effect cannot be changed on the fly because the volume to be compensated is normally not going to change. But it will change if spent drives are separated. IOW, perhaps they might be made to work that way. If a Cataphract can do it, why can't any multistage missile, and eventually MDMs. Anyway, when the range of multi-drive missiles changed, the drive rings didn't get bigger, only the missile body did. No? Is there a link to one of MaxxQ's drawings?

Huh? MDMs never got longer ranged.

The RMN MDM, whether the original capacitor powered ones, or the new smaller Mk23 microfusion powered ones had exactly the same continuous powered range. 3 drives; each capable of 180s @ 46000g for a combined range of just over 65 million km. (And they always had the ability to coast before bringing up the final drive; for theoretically unlimited range)

That said, until Apollo came around your chance of hitting at beyond about 45 - 50 million km was low enough most fleets saved their ammo and didn't use the last 15-20 million km of a MDM's continuously powered range range. But that has nothing to do with how far the MDM's drives could take it.

penny wrote:

Jonathan_S wrote:So for DDMs (or MDMs) you could have all drives all set to half-power (which is their normal usage); giving (for the RMN) 46000g for up to 180 seconds each. Or you could have all drives set to full-power; giving 92000g for up to 60 seconds each.

Half power:
DDM
29.2 million km continuous powered range
0.54c terminal velocity

MDM
65.7 million km continuous powered range
0.81c terminal velocity

Full power:
DDM
6.4 million km continuous powered range
0.36c terminal velocity

MDM
14.6 million km continuous powered range
0.54c terminal velocity

Thanks for the trouble, but I was more interested in whether all drive stages had the same capability on any particular setting. IOW, are all stages equal? From your post I gather they are.

Yes. All the drives on an MDM are identical and have identical endurance and acceleration. (A cataphract, again, is different because it uses a different (and shorter ranged) mechanism). And each drive on an MDM appears to have the same endurance and acceleration as the drive of the (noticeably smaller) single-drive missile of that same navy. Doesn't seem to matter if it's a tiny LAC missile, a small DD/CL missile, a bigger CA/BC missile, a large SD/DN capital missile, a DDM, or an MDM -- all have 180s @ 46000g. [well, older drives were slower; but that's the current state of the art for all of them]

(The exceptions are the CM derived Viper, 75s @ 130000g, and the ERM and LERM, 225s @ 46000g)

penny wrote:

Jonathan_S wrote:I say "up to" because while you can't pick a different acceleration once the drive is active you're free to turn a drive off early; and I assume that would apply to any of a DDM or MDM's drives. It's just that you can't ever turn it back on; so running less than the maximum time just gives you shorter range and lower velocity. The only drive that isn't normally run for its full duration is the final drive; and that's just because most engagements aren't made at the maximum possible range -- so the missile reaches its target with time still left on its final drive.

RMN missiles in particular aren't going to be shedding significant volume if they drop spent drive rings because, in almost the complete opposite of your solid rocket fuel example, they use the same power source (the microfusion power plant) to power all their drives. The reactor is way bigger than the fuel tanks; so even if you split the fuel into 2 or 3 tanks so you could drop an empty tank with its expended drive ring they'd still take up a pretty small fraction of the missile volume compared to the reactor itself.

You certainly guessed where I was headed. A smaller reactor servicing each stage.

That'd be a really good trick since the microfusion reactor is already as small as the RMN can make it. (If they could make a smaller one they'd have made a smaller Mk23 and fit more of them into a pod)

penny wrote:

Jonathan_S wrote:(Other people's capacitor powered MDMs could be a bit different, as you might be able to split into 3 capacitor banks -- one per drive -- and drop them when empty. Though even that's likely requiring more initial space in the missile as 3 separate banks each run to empty are going to be less efficient at storing energy that one big capacitor bank that's shared across the drives.

I don't think I can agree with the less efficient notion. Power is usually loss with distance. Hence, step-up transformers. A more contained setup should be more efficient, not less. That is presently the case with all of our current applications and electronics.

At any rate, what exactly is contained inside the huge volume of the separate stages of multi-drive missiles that can't be discarded. At any rate, only multi-drive missiles might be off the table, not multistage missiles.

Whether it's more efficient or not depends on the discharge curve of the capacitor. (And also if there's extra space lost to packaging to form 3 separate detachable capacitors instead of one 1 big one)

Certainly for batteries using more cells together, so you're pulling more lightly from each, lets you extract more usable power than taking the same size and capacity of cells but fully draining one before pulling any from the next. One big battery pack is just more efficient for power storage than sequentially using multiple small packs; even if the total kWh is the same.

penny wrote:I know they don't currently work that way, and I know that currently all drives have to be set for the same acceleration; but again, that might be the effect caused by the static nature of the compensator whose compensation effect cannot be changed on the fly because the volume to be compensated is normally not going to change. But it will change if spent drives are separated. IOW, perhaps they might be made to work that way. If a Cataphract can do it, why can't any multistage missile, and eventually MDMs. Anyway, when the range of multi-drive missiles changed, the drive rings didn't get bigger, only the missile body did. No? Is there a link to one of MaxxQ's drawings?

Jonathan_S wrote:Huh? MDMs never got longer ranged.

OOPS! Pardon my Shannon!

That should have read, when SDMs got longer ranged (by becoming MDMs) didn't the missile grow much longer than an additional drive ring, then two?

Jonathan_S wrote:RMN missiles in particular aren't going to be shedding significant volume if they drop spent drive rings because, in almost the complete opposite of your solid rocket fuel example, they use the same power source (the microfusion power plant) to power all their drives. The reactor is way bigger than the fuel tanks; so even if you split the fuel into 2 or 3 tanks so you could drop an empty tank with its expended drive ring they'd still take up a pretty small fraction of the missile volume compared to the reactor itself.

penny wrote:You certainly guessed where I was headed. A smaller reactor servicing each stage.

Jonathan_S wrote:That'd be a really good trick since the microfusion reactor is already as small as the RMN can make it. (If they could make a smaller one they'd have made a smaller Mk23 and fit more of them into a pod)

True. And that would be a neat trick. I never said the RMN could do it. Or would do it. Tum ... te tum ... tum tum.

Look what a new pair of eyes (Grayson) did for the RMN's power source. Now what do I imagine that a new pair of eyes (MAlign) can do for the current GA's power source. Hmm.

Jonathan_S wrote:(Other people's capacitor powered MDMs could be a bit different, as you might be able to split into 3 capacitor banks -- one per drive -- and drop them when empty. Though even that's likely requiring more initial space in the missile as 3 separate banks each run to empty are going to be less efficient at storing energy that one big capacitor bank that's shared across the drives.

penny wrote:I don't think I can agree with the less efficient notion. Power is usually loss with distance. Hence, step-up transformers. A more contained setup should be more efficient, not less. That is presently the case with all of our current applications and electronics.

At any rate, what exactly is contained inside the huge volume of the separate stages of multi-drive missiles that can't be discarded. At any rate, only multi-drive missiles might be off the table, not multistage missiles.

Jonathan_S wrote:Whether it's more efficient or not depends on the discharge curve of the capacitor. (And also if there's extra space lost to packaging to form 3 separate detachable capacitors instead of one 1 big one)

Certainly for batteries using more cells together, so you're pulling more lightly from each, lets you extract more usable power than taking the same size and capacity of cells but fully draining one before pulling any from the next. One big battery pack is just more efficient for power storage than sequentially using multiple small packs; even if the total kWh is the same.

penny wrote:OOPS! Pardon my Shannon!

That should have read, when SDMs got longer ranged (by becoming MDMs) didn't the missile grow much longer than an additional drive ring, then two?

Oh. Yes. The original capacitor powered Mk41 MDM was definitely bigger than just the length of 2 extra drive rings as it also had to squeeze in sufficient capacitor volume for triple the energy -- though I believe it grew in both length and girth.

While we don't think we know the exact dimensions, in White Haven's diatribe against them in IEH (before Honor pulls him up short) he says the launchers for them will take up 12% more space and the new missiles size would effectively reduce magazine capacity by 18%.

(Once Haven developed MDMs theirs were, IIRC, somewhat larger -- sufficiently so that they never bothered with missile launchers for them and used them as a pure pod-based weapon. But again no actual dimensions)

We then know that the RMN's microfusion powered Mk23 MDM was smaller than the earlier Mk41; but I don't think we know how much smaller; which means we don't know how it compares in size to an SDM.
(Though we know that sitting in size between an SDM (which is small enough to be carried by DDs, CLs, and smaller CAs) and the full up MDMs we have the microfusion powered Mk16 DDM. It's enough smaller than an extra four can get squeezed into a standard pod (14 Mk16s vs 10 Mk23s) -- though most of that gain must be from more efficient packing; rather than a straight 31% decrease in size -- as that would make it smaller than an SDM! And we know it isn't)


Still, when even the obsolete big MDMs are no more than 18% larger than an SDM that's not much extra volume to potentially drop if you went to a physically staged design.

It's interesting that we've got RMN 4 missiles of differing sizes:
* SDM (capacitor)
* DDM (microfusion)
* Mk31 MDM (microfusion)
* Mk41 MDM (capacitor)
and yet each one has identical performance from its drive(s). Across that entire size range the each drive pushes its missile for 180s @ 46000g. Missile size (within reason, up to at least +18%) doesn't appear to affect drive performance.


It's also interesting that the break-even between capacitors and microfusion seems to fall between 225 and 360 seconds of drive runtime. The Mk14 and Mk36 ERM and LERM still use capacitors; presumably because microfusion would push up their size -- but for the Mk16 DDM (with a pair of 180s drives) the microfusion is more compact; so that's the smallest missile that uses it.

I have to assume that's because for microfusion you have a large minimum fixed size because that's as small as you can make the reactor machinery; but then each additional second of extra runtime requires far less size growth than capacitors because reactor fuel is vastly more power dense. So the size vs power trendline for it would start high up the size axis and then climb slowly; while the trendline for capacitors would start much lower on the size axis but grow much faster; with the two lines crossing somewhere at or before the power required for 360s.

If the RMN could shrink the reactor size they'd build microfusion powered ERMs or even SDMs. (Yes they require a bulkier launcher -- but the extra power they make available for jamming, decoys, and other ECM makes the missiles with microfusion more capable than their capacitor powered counterparts -- so I think it'd be worth installing if it didn't drive up missile size)



I also find it interesting that ERM and MDM tech haven't been combined.
For the full up 3-drive MDM it would have been pointless. Their continuous powered range already exceeded practical control. But if you could have boosted the Mk16's drives from 180s each to 225s that would have boosted its capability from 29 million km and 0.54c to 45 million km and 0.68c!
But we don't know why they weren't combined. It's possible that there's something about the extended range drives that's currently incompatible with the baffle tech; or it's possible that it would have pushed the missile size up just enough that you couldn't have packed the extra 4 into a pod. (Or, its possible RFC simply didn't think about or want to deal with it )

Where is the microfusion reactor in the missile located again? And what volume of the missile does it occupy?









P.S. BTW Jonathan. Your previous posts are amazing. Like eye candy. I'd tell you to keep it up ... but then you always do. And ... it's like you read my mind on several points.


Thanks.

penny wrote::idea:

Where is the microfusion reactor in the missile located again? And what volume of the missile does it occupy?

I don't think we've been explicitly told, but I assume the reactor and its fuel tanks fit into the mid-body section where the capacitors normally go.

Poking around I rediscovered the diagram of a missile internals from the armor essay in IFF, and that's of an old Mk-13 cruiser grade SDM. I can't recall every seeing another, so that's probably all we have; however I'd assume that most anti-ship missiles are laid out similarly.

In that Mk-13 diagram is shows the internal organization to be (from the tail of the missile moving forward to its nose):
* Telemetry receiver
* Thrust vectoring RCS
* Impeller drive module (including the impeller rings and what looks like internal engineering components)
* RCS fuel tank
[To this point this is roughly the after 1/3rd of the missile]
* Superconducting capacitor rings & (inside them) control moment gyroscopes
[the capacitors for this SDM appear to take up 1/4 of its length - so at this point we're just short of 60% of the length of the missile]
* (detachable) laser head lasing rods & forward RCS fuel tank [the tank appears to be nestled alongside the lasing rods; so takes up no additional length]
* forward thrust vectoring RCS
* laserhead control system
* 15 Mt warhead
* multi-spectrum sensor package

I'd think that a DDM or MDM would still need most of those things (though the warhead would be bigger, you'd have a larger impeller drive module, and a reactor + tankage instead of capacitors). And I'd also think you probably can't move them around too much, so the middle is kind of what's left to squeeze power into.
(The telemetry needs to be at the back to receive the signals coming 'up the kilt' from the ship that launched it; the fore and aft RCS needs to be far enough from the middle to have leverage to pivot the missile, the laserhead/warhead package needs to be up near the nose and the sensors are on the nose)

penny wrote::idea:

Where is the microfusion reactor in the missile located again? And what volume of the missile does it occupy?

The reactor is somewhere that can't and won't be separated, because that would leave the missile without power, which is pointless. The reactor must travel with the missile to the end and detonation.

The reactor fuel (hydrogen or helium) need not travel all the way to the end. We don´t know how much volume the tanks require, though.

We do know that wedge geometry requires the rings to be at the tail end of the missile body. You can't have the tanks behind them, so they must necessarily be forward of it. And since they're forward of all three rings, you can't jettison them.

That leaves only the two spent rings that could be dropped.

BTW, we've never been told whether the rearmost ring is the first to be activated or the foremost one is.

ThinksMarkedly wrote:

penny wrote::idea:

Where is the microfusion reactor in the missile located again? And what volume of the missile does it occupy?

The reactor is somewhere that can't and won't be separated, because that would leave the missile without power, which is pointless. The reactor must travel with the missile to the end and detonation.

The reactor fuel (hydrogen or helium) need not travel all the way to the end. We don´t know how much volume the tanks require, though.

We do know that wedge geometry requires the rings to be at the tail end of the missile body. You can't have the tanks behind them, so they must necessarily be forward of it. And since they're forward of all three rings, you can't jettison them.

That leaves only the two spent rings that could be dropped.

BTW, we've never been told whether the rearmost ring is the first to be activated or the foremost one is.

Ah! The lightbulb illuminated the path down which I was headed! Cool!


Well, before we turn the holotank off, let's give the tactically promising application a bit more screen time.

Thinksmarkedly wrote:The reactor is somewhere that can't and won't be separated, because that would leave the missile without power, which is pointless. The reactor must travel with the missile to the end and detonation.

One of my engineering professors once said that oftentimes the solution is better served by how one approaches the problem. The MA seems to have imbibed that notion while they were still in test tubes. Alphas … duh. Oftentimes, when brainstorming, one simply needs to get out of ones own way. And never tell Sonja Hemphill that something won't work, but how it can be made to work.

Having said that, what is truly “the end.” I'll give you a hint. The answer might lie in the same question that I applied to the wedge. When does the reactor outlive its usefulness and becomes a liability? Let's look a bit closer at the problem.

As far as multi-drive missiles go, and an on the spot analysis of the problem, the reactor is certainly needed on its journey up to and including powering the ECM and wedge.*

Remember, the wedge will be dropped soon. After the energy requirements of the ECM has been met (lighting the missile up like a Christmas tree), is the remaining energy requirement really that high? After the wedge is dropped and the missile body housing the reactor has separated, the missile only needs to detonate, which is all of several microseconds.

A smartly packed bank of high density instant discharge capacitors can be tasked to provide that instant power delivery. The reactor can be ejected after the ECM requirements have been met. So, the entire volume of the missile that is housing the reactor can be separated. The reactor consumes a massive one third of the missile body. Add to that the 18 % of the additional volume that may be shed which an SDM grew to become an MDM and voila! The total volume shed should represent a significant decrease in the end-of-run missile body!

Also, why simply separate the stage containing the reactor. It should immediately self destruct. It might mess with enemy sensors. IOW, if the reactor blows after separating, it might have an ECM like effect.

*Once the wedge is running on a missile and a ship, can the wedge run without any reactors? It doesn't really matter in this application because high density instant discharge capacitors are being considered. But I have always been interested in the question. As a kid, I remember being shocked that a car's engine will still run after disconnecting the battery.


P S. I almost forgot! I agree that the order of the activation of the drive rings is not only interesting but might play a crucial role in the success of this application.

However, do consider that the placement of everything will definitely change when reengineering the missile for this tactic.

penny wrote:After the energy requirements of the ECM has been met (lighting the missile up like a Christmas tree), is the remaining energy requirement really that high? After the wedge is dropped and the missile body housing the reactor has separated, the missile only needs to detonate, which is all of several microseconds.

A smartly packed bank of high density instant discharge capacitors can be tasked to provide that instant power delivery. The reactor can be ejected after the ECM requirements have been met. So, the entire volume of the missile that is housing the reactor can be separated. The reactor consumes a massive one third of the missile body. Add to that the 18 % of the additional volume that may be shed which an SDM grew to become an MDM and voila! The total volume shed should represent a significant decrease in the end-of-run missile body!

Also, why simply separate the stage containing the reactor. It should immediately self destruct. It might mess with enemy sensors. IOW, if the reactor blows after separating, it might have an ECM like effect.

I wondered who would take Lord Skimper's place.
So you are adding capacitors, explosives and mechanisms to eject the reactor in order to do what? The wedge is not dropped (if it is dropped at all) until just before the warhead explosion (which also serves to destroy the reactor in a normal missile).

But lets assume that the wedge is dropped minutes before the warhead explosion. During that time the missile is just coasting, so what does it matter how much it weighs when there is no acceleration in any direction?

If the reactor were to separate and immediately explode, then the missile might be hit by shrapnel.

PS: After a car starts, the battery is almost unnecessary; the alternator or generator supplies the electricity for ignition. Consider the old time cars that started with a crank, they did not need a battery at all; since they had magnetos that supplied the spark.