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JHSV

Grey Havoc

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According to Tim Colton over at Maritime Memos, the USN has taken over full control of the JHSV program, so all operational JHSVs will be Navy.

More details here: http://www.coltoncompany.com/images/JHSV_Transfer_MOA.pdf
 

seruriermarshal

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USNS Spearhead (JHSV 1) After Sea Trials
 

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Grey Havoc

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http://www.dodbuzz.com/2013/04/22/navy-adds-high-speed-troop-carrier-to-fleet/
 

Grey Havoc

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Triton said:
Can we move this topic to the "Military" board now that this class has entered production?

We could merge it with this older short thread: http://www.secretprojects.co.uk/forum/index.php/topic,12621.0.html
 

Triton

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Cutaway drawing of Austal JHSV.

Source:
http://media.defenceindustrydaily.com/images/SHIP_JHSV_Westpac_102m_MRSV_Cutaway_lg.jpg
 

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Sea Skimmer

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Ton for ton the things already cost as much as LCS, while being entirely unarmed and entirely built to civilian specifications. Why on earth would you want a combat version?
 

Triton

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cluttonfred said:
Wow, have there been any proposals for combat vessels based on this design? Who needs LCS?!?

The Spearhead-class Joint High Speed Vessel (JHSV) has a different mission than the LCS. The JHSV can transport a United States Army or United States Marine Corps company (typically 80-to-250 troops) with their vehicles at speeds of 35-45 knots (65-83 km/h; 40-52 mph).

Someone with greater marine engineering knowledge than me can probably explain why monohulls are the preferred configuration for larger warships. The Independence class and the Spearhead class are also made largely of aluminum. The Freedom class is a semi-planing steel monohull with an aluminum superstructure.
 

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Sea Skimmer said:
Ton for ton the things already cost as much as LCS, while being entirely unarmed and entirely built to civilian specifications. Why on earth would you want a combat version?

Because it is built largely of aluminum, will the JHSV also have potential problems with cracks and danger of catching fire if hit? Aren't these catamaran aluminum ferries being used as military transport ships just because of the speed advantage over steel monohulls?
 

Triton

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http://youtu.be/mavkMHfMSao

Source:
http://www.air-defense.net/forum/index.php?topic=10538.30
 

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Sea Skimmer

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Triton said:
Because it is built largely of aluminum, will the JHSV also have potential problems with cracks and danger of catching fire if hit? Aren't these catamaran aluminum ferries being used as military transport ships just because of the speed advantage over steel monohulls?


Effectively the entire thing is aluminium, same for the trihull LCS. Steel ships also crack, that's a ship structural design issue not a matter of steel vs aluminium. Fires rarely burn aluminium, they can however melt it.

The point of JHSV is to be a high speed connector between a secure forward base at which conventional sealift ships and just random cargo ships can unload, and an unsecure/undeveloped forward area. That forward area might be a recently captured port, or it might be a Mobile Landing Platform from which the cargo can be transhipped on LCACs and LCUs. They were funded with army and navy money. Escorting JHSV is actually one of the few places were the high speed of LCS actually makes tactical sense.

A side advantage of JHSV is simply that it is small. It can thus use many ports around the world which could simply never hold a larger vessel. Its basically a supplement to the US Army operated LCU 2000 class LCTs and the LST sized Logistical Support Vessels. The size is more like an LCU 2000, but it has a realistic long range capability like an LSV, and is three-four times as fast so far more missions can be accomplished. Downside is no beaching capability what so ever, but floating causeways and other systems exist to provide a means to unload over a beach. One might also use an LCU 2000 which can ride on certain prepositioned ships, or one of the smaller USN LCUs that fit on amphibious warfare ships for this purpose.
 

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Everytime I see a flatdeck I think of dozens of VLS's for anti-air and strike missiles as one configuration.
 

Sea Skimmer

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Strike length Mk41 VLS is 25.25ft tall. The cargo deck on JHSV is only 16ft high, and only lower hull structure is under it, while the upper superstructure is the only crew space on the thing. Slight problem making that fit. You want air warfare capability, now you need sensors, a lot more men and power ect... cost spiral has commenced. Meanwhile if you added some weapons, you would not be able to add aircraft which are one of the most useful features of a warship. It isn't for nothing that LCS is based around y its air capabilities. Configurations like this and of this size were studied in the run up to the two LCS variants. They are too small and limited to be useful for the price. You want a pure missile platform with high speed, buy a plane.

Or at least, do it right and make an SL-7 into an arsenal ship.
 

Triton

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Sea Skimmer said:
Or at least, do it right and make an SL-7 into an arsenal ship.

Algol class vehicle cargo ships, also known as Fast Sealift Ships (FSS) or SL-7s, are currently the fastest cargo ships in the world, capable of speeds in excess of 33 knots (61 km/h).

USNS Algol (TAKR-287) is pictured below.

Would an arsenal ship be considered an auxiliary ship with the prefix USNS? Be classified as an ammunition ship (T-AE) and named for volcanoes? Would it travel with a Carrier Strike Group (CSG) or Expeditionary Strike Group (ESG) and need to be built to military specifications rather than merchant ship specifications such as the merchant ship-based Algol class (ex Sea-Land Exchange class)?

Source:
http://www.fas.org/man//dod-101/sys/ship/takr-287-algol.jpg
 

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bobbymike

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My preference is a converted helicopter carrier that deck could house hundreds of missiles including the ATK intermediate range global strike missile
 

Abraham Gubler

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Sea Skimmer said:
Strike length Mk41 VLS is 25.25ft tall. The cargo deck on JHSV is only 16ft high, and only lower hull structure is under it, while the upper superstructure is the only crew space on the thing. Slight problem making that fit.

You’d be crazy to fit Mk 41 VLS to a catamaran. Mk 41 design is all about turning the hot gas exhaust of a rocket motor 180 degrees. So it is exhausted from the ship upwards. On a catamaran with VLS cells located between the hulls this is entirely superfluous. You could just use a straight through VLS based on the Mk 48 system that opens a hatch on the top of the canister for the missile to fly and the bottom for the exhaust to vent. This would enable a considerable weight and reasonable volume saving compared to Mk 41 VLS.

As to the length of the missile canister there is no problem making that fit inside a high speed catamaran hull. They are built as sea frames and extending the super structure to fully enclose a battery of VLS is no problem. As to consuming the accommodation space there would be little need for a large number of humans on a catamaran missile ship compared to a catamaran ferry. So they could be accommodated in the superstructure above the hulls. Same for the bridge which could be located aircraft carrier style offset to starboard.

Sea Skimmer said:
You want air warfare capability, now you need sensors, a lot more men and power ect... cost spiral has commenced. Meanwhile if you added some weapons, you would not be able to add aircraft which are one of the most useful features of a warship. It isn't for nothing that LCS is based around y its air capabilities. Configurations like this and of this size were studied in the run up to the two LCS variants. They are too small and limited to be useful for the price. You want a pure missile platform with high speed, buy a plane.

Sure thing if you want to build a frigate but if you want a small, low profile arsenal ship able to get in close to shore yet still carry ~500 full size, strike length VLS canisters then a high speed catamaran will do it. Much better than the SL7 floating target.
 

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Triton said:
Sea Skimmer said:
Or at least, do it right and make an SL-7 into an arsenal ship.

Algol class vehicle cargo ships, also known as Fast Sealift Ships (FSS) or SL-7s, are currently the fastest cargo ships in the world, capable of speeds in excess of 33 knots (61 km/h).

Would an arsenal ship be considered an auxiliary ship with the prefix USNS? Be classified as an ammunition ship (T-AE) and named for volcanoes? Would it travel with a Carrier Strike Group (CSG) or Expeditionary Strike Group (ESG) and need to be built to military specifications rather than merchant ship specifications such as the merchant ship-based Algol class (ex Sea-Land Exchange class)?

Such a ship would only be USNS if it belonged to Military Sealift command and was manned by Civilian mariners. I think that's unlikely. We've had the discussion about designations before in the ArShip thread. I suspect a new designation would have been created (AAS, perhaps), or an existing one improperly reused (AS for Arsenal Ship, even though it repeats the Submarine Tender designation.)

The DARPA/USN ArShip capabilities document called for much higher levels of survivability than would be provided in a merchant ship hull specification. It was seen as a combatant, not an auxilliary, and would have been a very high-value target.
 

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Abraham Gubler said:
You’d be crazy to fit Mk 41 VLS to a catamaran. Mk 41 design is all about turning the hot gas exhaust of a rocket motor 180 degrees. So it is exhausted from the ship upwards. On a catamaran with VLS cells located between the hulls this is entirely superfluous. You could just use a straight through VLS based on the Mk 48 system that opens a hatch on the top of the canister for the missile to fly and the bottom for the exhaust to vent. This would enable a considerable weight and reasonable volume saving compared to Mk 41 VLS.


You'd also need a much stronger hull to hold it since you punched so many holes into the double skin vehicle deck that's holding the entire ship together. I doubt trapping so much rocket exhaust between aluminium hulls would be very popular.

As to the length of the missile canister there is no problem making that fit inside a high speed catamaran hull.


So your talking about a new ship already. Your proposal for 500 missiles would already far exceed the payload of JHSV even if they were merely cargo. Engage cost increase, and the relevance


Sure thing if you want to build a frigate but if you want a small, low profile arsenal ship able to get in close to shore yet still carry ~500 full size, strike length VLS canisters then a high speed catamaran will do it. Much better than the SL7 floating target.


Why exactly do you want to get a undefended ship with over a half billion dollars of very long range ammunition on board close inshore? So you can strike a mine and have it completely obliterated? Or do you want defenses too so this can become even more expensive, but remain helpless in the face of submarines and mien warfare from lack of aircraft? Your proposing a concept that has no valid mission at all and will have an all up cost approaching the billion dollar range.


At least an SL-7 or LMSR type hull at least can hide among distant merchant traffic, which will work fine given its long striking range and has the endurance to respond to global threats without refueling and replenishing constantly, JHSV has theater range at best, and its big enough to withstand a mine or torpedo without being certainly destroyed. The latter hull is also not that much more expensive then the stock JHSV, as opposed to the much enlarged one you want, yet could mount more VLS cells then anyone would ever feel like paying to fill. It'd also still have space to act as a transport on the side, which is nice since the arsenal ship role will be seldom ever be used.
 

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Sea Skimmer said:
You'd also need a much stronger hull to hold it since you punched so many holes into the double skin vehicle deck that's holding the entire ship together. I doubt trapping so much rocket exhaust between aluminium hulls would be very popular.

The exterior decking on these ships is not the primary hull strength they have cross beam members that hold the ship together. They look like girder sets until they add the cladding. So no problem with the hull piercing. As to the rocket exhaust it goes straight down into the ocean which is the best heat sink on the planet and as the ship is moving forward even at 20 knots its only a few seconds before that particular area is no longer enclosed on the sides by the hulls.

Sea Skimmer said:
So your talking about a new ship already. Your proposal for 500 missiles would already far exceed the payload of JHSV even if they were merely cargo. Engage cost increase, and the relevance

As I said before these ships are built as sea frames with customisable upper decks. AUSTAL and their rivals INCAT offer various mixes of truck, car, passenger and now even rail car type fitouts on the seaframe design. 500 SM4 (LASM) a reasonable indicative land attack weapon with their canisters would weigh around 800 tonnes. JHSV is a 103m seaframe that provides a deadweight of around 800 tonnes when outfitted as a ferry (no helo deck or side ramp). Remove the reinforced floors for trucks and cars, their internal ramps, seating and amenities for 866 passengers and there is enough weight for the VLS.

Sea Skimmer said:
Why exactly do you want to get a undefended ship with over a half billion dollars of very long range ammunition on board close inshore? So you can strike a mine and have it completely obliterated? Or do you want defenses too so this can become even more expensive, but remain helpless in the face of submarines and mien warfare from lack of aircraft? Your proposing a concept that has no valid mission at all and will have an all up cost approaching the billion dollar range.

Who said it would be undefended? Why can’t you sacrifice some of the payload weight for some self defence capability like RAM and the like? Also the hull form lends itself well to being stealthified. As to being inshore it would be there to provide prompt fires to ground forces. I always thought offensive support to expeditionary forces was pretty important. And as to the cost of a billion dollars maybe if you used this for something completely different like a TLAM carrier but there is no need for such as there are plenty of TLAMs in the fleet.

It depends what mission obviously you customise this for as to its utility. Frigate or strike destroyer (TLAM) are obvious fails. But as seabased artillery providing a large bank of VLS to be fitted with an appropriate land attack weapon or if your taste goes in other directions >1,000 tonnes worth of guns and ammo (a couple of AGS Lite) it has utility. Because in this case its strengths support the mission and its weaknesses do not compromise it.
 

Grey Havoc

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On a related note: http://www.militaryphotos.net/forums/showthread.php?227353-HSV-2-Swift-EX-USN-for-sale
 

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Wow, that would make one heck of a little cruise ship or, better yet, a fantastic yacht for the filthy rich. Check out the "Refit Design Concepts" to the right of the page in the link above. I am not quite sure what a "Shadow Yacht" is, but I want one!
 

Grey Havoc

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http://www.bloomberg.com/news/articles/2016-01-14/navy-s-fast-sealift-ships-can-t-stand-buffeting-from-high-seas
 

marauder2048

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Oh lovely. The leaks from Gilmore's sieve organization signal that budgetary silly season is upon us.
 

Grey Havoc

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http://snafu-solomon.blogspot.ie/2016/10/breaking-huthis-reportedly-hit-and.html

22 crew, including a number of Australians, are reported to have died. A C-802 missile seems to have been used.
 

Grey Havoc

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https://twitter.com/MbKS15/status/783705414743552004?lang=en

Bit of a miracle it is/was still afloat (albeit barely).
 

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One of the upsides of the catamaran. The buoyancy is mostly in the pontoon sidehulls, and those wasn't affected by the missile hit.
 

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Basic analysis. Everyone seems agreed that it was probably a C802 http://www.hisutton.com/HVS-2%20Swift%20hit.html
 

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