Aquatic Standards Discussion

Toshiro

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#1
The engines I designed are able to work underwater as MHD Drives. However, there have been disagreements on the speeds and use on the discord. My application on the Plumeria refit (link is wip, will change on approval) has the ship being able to submerge and go 300 kph with shields down and 800 kph with shields up (since these shields can change their geometry and be used to supercavitate). The Plumeria has submerged in RP, specifically the Eucharis.

Some people dislike the idea of spaceships submerging in general, citing Professor Farnsworth from Futurama saying that they're only built to handle atmospheric pressures between 0 and 1. I think some planets have thicker atmospheres, and don't necessarily subscribe to this thinking, but I am wondering how how much depth is possible. (I think that water pressure increases by one atmosphere every 10 meters/33 feet, though 'atmosphere' could mean the water pressure at sea level? That's unclear). I am also not married to these Plumeria speeds, but I feel like standards should be defined. The Plumeria is, at least, an aerodynamic/hydrodynamic shape.

Perhaps some standards can be established here? Please provide input. I am open to changing the Plumeria 2E's listed speeds. They're just based on Discord recommendations.
 
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Zack

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#4
Some people dislike the idea of spaceships submerging in general, citing Professor Farnsworth from Futurama saying that they're only built to handle atmospheric pressures between 0 and 1. I think some planets have thicker atmospheres, and don't necessarily subscribe to this thinking
I think its important to understand why the pressure is a problem for starships that can otherwise survive anti-tank weapons.

Starships are built to have more pressure on the inside than on the outside.

This is part of the reason why aluminum cans are so strong before they've been opened. All that pressure pushing on the thin outer skin reinforces the whole thing.

Another thing to keep in mind is that because the pressure is greater on the inside, generally you're going to build all your external doors to open inward. This means all the pressure from the ship is forcing those external doors closed. Your doors are also probably a bit bigger than the hole they are covering, so all that pressure helps force that overlap closed so nothing leaks out.

If you flip this around, and all the pressure is on the outside of the ship, you now have to design everything to account for that. Your poor engineers have to massively over engineer all the coverings, doors, inlets, and sensitive outer parts to withstand being pushed together by outside pressure and pushed apart by interior pressure. Just like any door, it is a lot easier to push open than to pull open.

You also have other problems when moving at speed under water like cavitation eating away at anything exposed to fluid moving across it. This will damage your stealth coatings, your radiators, your sensors, and even your armor.

It is also very likely that your areodynamic shapes don't work so well when submerged, again due to pressure.


Of course you could turn on your shields and negate this whole problem by just not actually being in the water, and holding a bubble of air around the craft at the right pressure... but still.

Unshielded is probably a very slow top speed: maybe 200kmph

Shielded: Probably a mach 1 or 2?

And any ship designed to supercavitate would likely just use their atmospheric top speed.
 
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Toshiro

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#6
The fact there are so many different interpretations shows why this discussion is so necessary.

I suspect a maximum depth for spaceships should also be defined. Zack's recommendation is a good starting point, though some might think it a bit high. Unless he meant Mach in relation to airspeed. The Mach number for water is a far higher speed. I set an upper limit of 800 kph (shielded) on the Plumeria to be safe. Can drop unshielded from 300 kph to 200 kph.
 
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Zack

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#7
Yeah, the numbers I gave are uninformed guesses. Don’t take them too seriously.

I just used Mach because it’s something people are familiar with.
 
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Toshiro

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#8
I've adjusted the speed as stated above. 200 kph (unshielded) to 800 kph (shielded). I'm not keen on seeing much above that...
 

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#9
Given the construction methods used in SARP. Starships would be able to be submerged. When you consider the hull materials used, depth wouldn't be an issue unless they try to go to the Marianas trench.

However, the propulsion systems would most likely be very inefficient. The engines are optimized to propel the ship in space, and atmosphere. Both of which are very thin compared to water.
 

Toshiro

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#10
True, though the Plumeria 2E's Multi-Stage Aether Drives are designed to use magnetic fields (normally used for Aether exhaust control) to manage propulsion in magnetic mediums( water) as a magnetohydrodynamic drive. So the Plumeria 2E concept, in regards to engine output, has an advantage over previous designs in such operation.

The engines themselves have already been approved.
 

Zack

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#11
As stated above, the materials and construction methods don’t really matter as much as how the ship was designed. If your engineer didn’t consider taking the ship underwater then it is very likely the ship will flood when taken underwater.
 

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#12
If the engines were designed to be used for underwater, then you have it covered. Personally I would shut down those engines and use gravitics to move through the water. But that is just me. :)
 

Toshiro

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#13
Okay. I'm going with 200 kph unshielded and 800 kph shielded, for a spaceship with a secondary UW mode. Relatively shallow operation.

What about actual submarines designed for it though?
 

Zack

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#14
Classified, but slow.

Modern subs are all using either sewback propellers or ducted propellers because they are quieter. They are also slower than regular propellers.

These subs also go slower to reduce noise, especially from cavitation from the propeller moving too fast through the water.

So as a useful, reasonable, underwater speed I think a low number is pretty good.

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But when it comes to sprinting, you’re probably looking at the same speed we use for normal atmospheric flight, or maybe a bit slower. We can already hit Mach 2-3 under water using supercavitation today but that comes with its own problems, namely it is super hard to see anything while super cavitating.

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A super tech SARP ship, maybe with some highly advanced shield tech may be able to move the water out of the way, and then put it back without too much disruption and hit some really high speeds.