FutureTank

Actually the science of builogy says that they, the amphibians, MUST be completely submerged to enable them to subsist. Almost invariably the amphibians feed from the water, and the tactic used by the crocodile species is to attack from a submerged position.


Who is talking about the surf? The so transported infantry have to get to the surf FIRST! The EFV is advertized as being able to deliver infantry in an assault so delivered from "beyond horizon". This is not some abstract distance, bit varies from 21 to as far as 70 nautical miles. What this means is that the EFV with a speed of 15knots would be very observable on the survace (by virtue of the wake it generates) for over an hour at least.

The AAV7 vehicles can not "cross surf zones", but can negotiate some surf heights depending on current and beach conditions. This varies from osean/sea to ocean/sea, and from season to season. In general, the wave needs to be at about 2m, and certainly no larger then 4m. On the other hand the fully amphibious vehicle would also have problems witht he surf on some beaches, but far less so since it can ground itself and use tracks to make it's way up the beach.

I'm not sure how this is relevant to the question.

FutureTank

As I see it, the considerations that go into designing an IFV for marines/naval infantry, many that they are, must in the forst instance ensure the ability of the infantry to at least get to the objective.
Given that the approach to the objective would often be a completely exposed piece of terrain, the job is already made difficult.
The LCACs as expensive and, as are LCU/Ms, are required the rest of the force's gear onto the beach (a logistic operation that would take 5 hours in itself).

Technological complexity is there for a reason, it saves lives. Saved lives ensure there is a preservation of combat power in the force to perform it's mission and achieve stated objectives.

The best way to deny the enemy the ability to engage the marine infantry force before they are ready, in other words to deny enemy the initiative, is to deny the nemy the knowledge about the assaulting force and it's objectives. What his means is the design is not made complex because it displays the skill and knowledge of the engineers, but because the military professionals have included the principles of force security and surprise into the very design of the 'tools of trade', the AAFV.

This would be a first in the history of AFV design.

Of course as I pointed out, this would also require the naval vessels to be redesigned to enable them to deploy the vehicles from concealed in-hull position such as a hull well.

There are other bonuses to having such vehicles.
Such vehicles can also tow their own supplies underwater, removing need for other surface delivery means such as the very expensive and large LCACs, and even more difficult to deploy LCMs. This would allow the average assault force to be increased from one infantry battalion to a reinforced unit where the vertical component can be configured independently (a company) and therefore not reducing the actual amphibious infantry component of the assault.

JCT

Not being such a smart guy, you will have to define builogy for me. A quick google search turns up the term, but no definitions.

Google did find several definitions for amphibious:

Others:
Amphibious - definition from Biology-Online.org
Amphibious Vehicle definition - Army Technology

Initial posts to this thread lacked any reference to crossing the surf, IMHO a key component for naval infantry, however it may be accomplished.

Sounds like a neat capability, but driving the development,cost, and weight of the vehicle through the roof. Not a necessary characteristic in my mind.


Once again, earlier posts discussed breaching buildings, I was providing information on organic USMC rifle company capabilities.

omon

actually almost all t series soviet tanks, can cross lakes, rivers underwater, limit is 5m, and it takes some time to make snorkle ready.

Attached Images

800px-.jpg (81.3 KB, 35 views)

FutureTank

Both definitions are wrong.
The "1. Having the ability to live both on land and in water, as frogs, crocodiles, beavers, and some plants." is wrong because in biology the amphibians are specific species of reptilians, and do not include mamals and flora. The discriptor 'live' is rather lacking. Human beings are also able to 'live' on both, land and in water, and during summer holidays many do :-)
So far as I'm concerned, an amphibian is a species that, though able to survive on land, hunts in or from the water.

"An amphibious vehicle is capable of traversing bodies of water as well as land. Amphibious vehicles include both wheeled and tracked armoured vehicles, as well as army hovercraft, designed to be able to cross rivers or perform beach landings."
A T-55 tank is able to both traverse bodies of water as well as cross rivers and perform beach landings, and yet no one calls it amphibious.
From the engineering perspective the vehicles often termed 'amphibious' only swim on the surface. The Soviet designation of the PT-76 makes this very clear.

An oversight on the part of the initial posters.

Weight would not be much greater then the current solutions. Lesser in fact since the best solution is a cast hull with fewer weld/bolt joints. I don't see cost escalations either since I am not talking about design for a submarine, but a vehicle designed for limited submersion periods only. The vehicles can also be used as additional lifeboats on the vessel since they can be deployed in seconds. In fact the challenfe would be more in designing the naval vessel ability to deploy them.

On the other hand a loss of a single EFV enroute to the beach would not only cost the lives of 20 service personnel (current EFV proposal), but also eliminate all the systems of that vehicle from TO&E of the unit. It seems to me that the possible greater cost of one subsystem in the vehicle would justify the survival of the crew, passengers and other systems.

FutureTank

Yes, thank you...hadn't seen that picute before.

'Snorkle' is also not quite correct as a descriptor of mode of propulsion since it only describes the means of supplying oxygen to the crew compartment. Other then that the tank simply crawls on the bottom of the water course since it lacks buoyancy. I had a very personal description of a tank's 'affinity' for water when one slid off a bridge into 6m of water. The description of "like a stone" was applied to it's immersion technique :-)

Stoner

when the snorkel is not deployed, where is it stored? is it manual deployment or remotely-operated?

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zraver

The assault snorkel is store din atube on the back of the turret on T-series tanks. These shallow water devices are jsut for crosing fords deeper than the drivers hatch. For crossing deeper i am assuming the snorkels have to be brought forward.

FutureTank

it takes about 20 minutes to prepare a tank for deep wading. Aside from errection of the air tube, it also requires the crew to seal the tank against any water penetration.

In a fully amphibious IFV this would be designed in, so no preparation would be required. Oxygen for the crew would be in compressed cylinders stored in/on the vehicle, so of course no external detection of the IFV would be possible by observers.