Talk:Short-range Defensive Water Cannon

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I'm very curious about what these look like and where they're placed. I imagine they went through a couple revisions ... the first being placed atop the Drake Building, then improvements prior to being fitted to the Firehawk. They're probably mostly behind hatches, but we need a picture to accompany that article!

Let's see what we can learn from that article that might give us clues to the form. It uses electromagnetic fields to focus a high-pressure water stream. That's interesting. Is it an electromagnetic nozzle that employs diamagnetism to confine the stream and thus accelerate it? Water is a weak diamagnet, so the energy pumped into that nozzle will have to be tremendous ... not necessarily "ramp up the MAM reactor" tremendous, but it isn't trivial, either! Of course, that magnetic field might be invaluable in protecting the nozzle from abrasion.

What pressurizes the water canons? One solution would have a central pressurizer running high-pressure water to various places around the ship. The water is then forced through narrower-diameter fittings, aimed by a 2-degree-of-freedom armature, and then further confined and ejected at the nozzle. Alternatively, the cannons might draw from a lower-pressure water supply line, pressurize at the cannon, then aim and fire.

When is the YAG added to the stream? It would be easiest to do this before going through the pressurizer, injecting the YAG as a slurry and then dispersing it throughout the ship. This means the YAG is always present in the water cannon stream and cannot be switched off, nor can that high-pressure water supply be used for any other utility. The abrasive YAG would also wear on moving parts in the cannon and even abrade the interior of the entire high-pressure line. I'd recommend injection at just before the nozzle. This would require a high-power compressor fitted to the cannon itself. The water cannon would then have two modes of operation: standard fire-fighting and pirate suppression [snicker], and YAG-enhanced lethality. YAG injection at the cannon would likely be very noisy, giving an audio indication when the enhanced stream is in use. --Leon 09:38, 5 April 2011 (EDT)


The link to the industrial water jet cutter wiki page should shed some light on the basic pressurization mechanics. The additional conceit here to use a system like a magnetohydrodynamic drive to propel the water without resort to moving parts, and the projection of the EM field to some distance from the nozzle in order to project the jet to a useful range. Beyond that range, the jet rapidly breaks up and is harmless. That terminal pressurizer would indeed be a separate unit for each turret (with the YAG being added immediately before that step), since such high pressure is not required for any other purpose. The cannon indeed shrieks like a banshee when fired in YAG mode, in contrast with a rumbling hiss in fire-fighting mode.

I envisioned it looking something like a CIWS turret, but the barrel might be somewhat longer than that shown, and have some visible bracing trusses. --Dwayne 04:40, 6 April 2011 (EDT)


WOW! That thing is huge! Have a look at this Anti-Pirate Water Cannon video. This thing has, I believe a 120 meter range (this one does, anyway), and is very small. Note the two cylindrical motors -- this would be the 2 DoF I mentioned above, allowing the cannon to aim at anything in an up-down, left-right direction.

Magnetohydrodynamics makes more sense than simple electromagnetics and we might want to flesh this out more in your description once we have the details nailed down. Basically, we're going to be using salt water directly from the ocean, electrifying it so that it can be manipulated and accelerated as it moves through a magnetic field, then constricted through a nozzle to exert higher pressure. It would be cool if the nozzle utilized diamagnetism somehow, anyway, just to make it more science-fictiony and for the purpose of reducing wear on the nozzle from the YAG.

So here's a proposed example system; the details at each stage are open for discussion:

Water is first collected from inlets located adjacent to the thruster turrets and pumped into three stainless-steel, pressurized vessels that have a 2,000 gallon volume each. The vessels allow debris to settle before being pushed through Pressurized Sea Water Supply (PSWS) pipes, and provide a reservoir in the event of interruption of supply such as might occur if the intakes become clogged or the Firehawk is in drydock. Note that these tanks provide the basis for the ship's entire salt water circuit utility.

Each tank is kept pressurized to 65 PSI and water is supplied from them to each water cannon via 4-inch stainless steel pipes. These supply lines couple to the water cannon intake manifold. YAG slurry injection from one of two local, 40 gallon storage tanks introduces an abrasive on demand at the top of the intake manifold using a jet-powered, high-pressure pump.

Electrodes at the base of the cannon are supplied by the ship's high-amperage bus to electrify the sea-water/YAG mix. This electrification allows electromagnetic coils to exert force on the water contained in the canon's 12-inch trunk, accelerating the water without requiring moving parts.

The first-stage accelerator consists of eight electromagnetic coils, also powered by the ship's high-amperage bus. These are tripped in rapid, repeating sequence to accelerate the water/YAG mix into the constriction and articulation assembly.

First-stage constriction reduces the diameter of fluid flow from 12 inches to four inches, boosting water pressure to ? PSI. The articulation assembly consists of two rotating flanges manipulated by high-torque DC motors powered by the ship's low-amp, low-voltage bus and controlled by sub-systems monitored by DCSI.

Final-stage acceleration is accomplished along a three-foot stainless steel barrel grounded to the ship's hull and coated with a non-conductive sheath. Sixteen coils, similar to those used in the first-stage accelerator, but smaller in diameter ring the barrel, giving it its characteristic profile. At this point, water is being drawn from the PSWS at a rate of nearly 1500 gallons per minute.

The seawater/YAG mixture then meets terminal constriction in the form of a final electromagnetic coil. No longer electrified, the water is susceptible to diamagnetic forces and the electromagnetic coil, powered directly from the ship's high-amp bus, squeezes the exhaust jet down to less than 2 inches in diameter. Nozzle satellite electromagnets, controlled by local subsystems, fine-tune the exhaust jet's coherence dynamically, maximizing for range and stream consistency.''

Your description makes it sound like there are several of these fitted to the Firehawk (the original Drake 4, plus additional units). Obviously, they can't be too big, but components of the system outlined above can be fitted below deck, to help conceal them and help your modeler from losing even more sanity over this project.--Leon 08:37, 6 April 2011 (EDT)


I cited the Goalkeeper chiefly for its profile. Obviously the water cannon turrets wouldn't need to be so large, since they wouldn't be housing a GAU-8 cannon, ready ammo, and a fire control radar. They would, however, still need to hold the electromagnetic coils, associated electronics, and some sort of visual fire-control system, so they'd be substantially larger than the simple nozzle of a firefighting/pirate-discouraging hose.

Your general specs seem reasonable. I hadn't envisioned the lethal YAG/water stream as being more than .1-.2cm in diameter, though. That's still substantially larger than industrial water jet cutters, and smaller diameter makes higher pressure easier to reach (we're probably looking at something like 100Kpsi here). In spite of the small bore, the damage inflicted would still be enhanced by the continuity of the stream (something like a continuous aqua-laser). The final phase narrowing of the stream down from several inches would probably be purely magnetically produced, such that it and the YAG supply could simply be switched off to function as a conventional high-output firefighting cannon.

As for the number, I think as many as eight or ten might be necessary for full coverage of the ship. The electromagnetics and YAG supply probably dictate fixed placements, otherwise they might go mobile. Some sort of drone platforms like that are probably part of the flight deck equipment anyway. --Dwayne 19:29, 6 April 2011 (EDT)



Wow. A one millimeter stream projected over a 150 meter range?! Is that even possible without the stream breaking down almost immediately into a spray? I used to use Reynolds numbers calculations at D&Z, and as the diameter goes down, so too does the Reynolds number (and thus the tendency for turbulence), but I don't know when the flow transforms from a stream to a spray and under what conditions. In a pipe, a Reynolds number greater than about 2300 is no longer laminar ... but in the air? Wow.

I'm just not sure how to treat this realistically. The nozzle is going to have to have some kind of concentrator/deconcentrator arrangement and the use of electromagnetism (either as MHD or diamagnetics) gives it a cool, high-tech edge and allows us to visually "fake" the design while handwaving some description of how the magnetic fields are doing all the work.


That was indeed the original conceit -- the projected EM field would operate as a sort of invisible EMD barrel extension. If you think it more practical to have a larger stream leave the physical barrel, with the projected EM field focusing it on the desired target, then so be it. That version would require some sort of radar or laser ranging component on the individual cannon, though. Force field and gravitic components would make this all much tidier, but as the invention is supposed to predate Mindy's access to Adventurer components and Trek Tech, it's not really an option.

Realistically, of course, there'd be limits to how much pressure and energy one could put into a water stream without converting it into a plasma gun, but here we just have to add a bit more handwavium to the mix. Perhaps charging the water could temporarily polymerize it in some fashion, letting it cohere like some sort of railgun-propelled Silly String? --Dwayne 01:48, 7 April 2011 (EDT)



It's interesting that you suggest the addition of a doping substance to polymerize the water stream ... I seem to recall something about that from a long time ago, but don't remember the context well enough to find it. In any event, I think we can assume any such agent to be part of the YAG slurry. I'll also move the YAG injection point, described above to be far too early in the acceleration process, to just prior to the concentrator/deconcentrator and we'll be good enough to go. From that, I'll draw up a rough P&ID (process and instrumentation diagram -- really, just a graphical version of what's described above), and then we should be good to start modelling the thing. I'll send you simple "volume studies" until we get to a design we both like and agree on, then flesh that out and put a bunch on the Firehawk.

With about eight to ten emplacements, I'm thinking two on the overhead, not far from the phasers (possibly to hose them down as part of an active cooling system), four on the bulwark, one forward, two aft. There are probably two models -- the Mark I from the original Drake building retrofitted to work with the ship, and the Mark II, designed from the start for shipboard use. I doubt that means anything, but it's an interesting bit of color and if you agree, the slight visual distinction will add to the realism of the finished models.

This is one of those diverting little side-projects that result in so many useful discoveries. We now know the Firehawk has a treated pressurized seawater supply utility. That makes sense for any vessel, and is probably commonplace, but I never considered it before. We've also begun to flesh out some of the power utilities available on-ship. Then there's those robotic firefighters you found. Obviously we have a few of those on board! I think I've mentioned using robotic arms instead of cranes in various places for deck servicing and support vessel deployment/recovery -- I'm not sure that distinction is too important, but I want to get that down in writing as something to think about when we get to the appropriate areas. --Leon 06:08, 7 April 2011 (EDT)


I wasn't actually suggesting doping the water, I was thinking something more in the Fringe Science territory of getting the water itself to act as a polymer, if only temporarily, by charging or "resonating" it in some fashion. The conceit would be that something like "polywater" is possible, but only while the water is carrying a powerful AC current that affects its latent diamagnetism in some fashion. When the water leaves the projected EM field that extends its concentrated stream, it loses its charge and reverts to its normal characteristics, immediately breaking up into a harmless spray (it might also add a harmonizing electric bass hum to the shriek of the firing water cannon).

The idea of the YAG abrasive itself acting as a polymerizing agent, or being doped with a polymerizing agent, has the elegance of relative simplicity, whereas high-energy polymerization of water offers the entertaining mad scientist overtones of bending the laws of time and space in order to swat a fly, so I'm torn as to which appeals to me more. If you're more comfortable with the "conventional" approach, by all means go ahead with it, since the only real objective of all of this is just a picture/3D model of the cannon. --Dwayne 18:25, 7 April 2011 (EDT)


Really, what we're talking about here is something that could be called, "Tesla's Water Pistol", right?

And don't be so dismissive of this effort as intended only to produce a picture! I think we're getting a lot more out of it. We're actually getting a cross-section of some important systems of the Firehawk itself. A complicated machine like the Firehawk, any other ship, or even a modern factory -- is an accumulation of interconnected systems weaving through each other like the circulatory, skeletal, nervous, and muscular systems of an organism. What started out as, "How do we shoot down super-pirates?" has grown into an exploration of the anatomy of the Firehawk. We'll get some pictures out of it, yes. Maybe even some animations! But we'll also have a better comprehension of the Firehawk as a place and as a character in the System 4ce universe. We now know, for example, that pressurized, treated sea water is available as a utility throughout the ship. It certainly has to be distinguished from pressurized freshwater, hot pressurized freshwater, and high-pressure steam. Are the outlet faucets simply marked or painted a different color? Are the threads different so that you can't attach a freshwater service to the sea water utility? The answers to these questions provide detail and color to the setting.

We two, you and I, are the Franz Josephs of the System 4ce world, carefully scrutinizing all available evidence and meticulously diagramming how it looks and functions.

No, not of Austria. Of The Star Trek Technical Manual. --Leon 12:48, 8 April 2011 (EDT)


"Tesla's Water Pistol" is quite apt, as Mindy shares much of his research style (driven by a highly developed "mental CAD/CAM" capability) and tendency to "think outside the box".

And by all means it's enjoyable and informative to pursue these little thought experiments of ours, though somewhat inconvenient to be distracted by them while trying to prepare for an actual game... --Dwayne 04:26, 9 April 2011 (EDT)

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