Catapult Ski Jump (retrofit?)

[ouroboros]

I was generally under the impression that while a steam catapult could be integrated with a ski jump on a carrier, the technical difficulty and cost made it unattractive, at least concepts that actively had a curved catapult track embedded in the ski jump hump itself. With the recent successful launch of a Hornet with EMALS, the wheels in my mind started turning again.

From what I understand, EMALS is essentially a linear motor with some guide rails. As such it doesn't suffer from the curved track limitations of a steam catapult. As far as linear motors are concerned, examples of curved tracks do exist, such as roller coaster rides and subways, though understandably the power and speed involved are not necessarily comparable.

If such there are no geometry constraints then, why not integrate a ski jump with EMALS? Is there an undefined issue regarding nose gear forces that makes this unattractive?

Regarding a retrofit, on existing flat deck ships such as helicopter carriers and existing short decked carriers, would a drop in ski jump module, with associated electrical gear housed in the hump, be attractive? I would imagine a lot of vessels would have insufficient power available, so you would also end up fitting the hump with one or more marine gas turbines (or perhaps a bank of microturbines) to provide power.

 

[Rickshaw]

Alternatively you could have a ski-jump which elevates through the use of hydraulic rams, allowing the use of either CTOL or STOL aircraft be used on the one ship. On a helicopter carrier, the use of such an elevating ski-jump would gain an extra helicopter landing spot when its lowered to normal deck level.

 

[Pioneer]

I like the way you both think!!

For a long time I have wondered about the feasibility of a catapult/skijump combo
With a EMALS/skijump combo arrangement, would this mean theoretically that that a heavier aircraft (or heavier warload) aircraft could be launched over a shorter distance (saving important deck space on small carriers like Invincible / Príncipe de Asturias / Giuseppe Garibaldi classes of light carriers)? For this normally means a full deck run, which hinders normal deck ops!

Alternatively you could have a ski-jump which elevates through the use of hydraulic rams, allowing the use of either CTOL or STOL aircraft be used on the one ship. On a helicopter carrier, the use of such an elevating ski-jump would gain an extra helicopter landing spot when its lowered to normal deck level.

I must admit, I have thought about this idea/theory even more over the years!! ;D
This arrangement and operational flexibility could be the answer to the USN's reluctance of skijumps on its LHA's/LHD's! (But then again the USN brass has alway's seen this (as per the SCS concept!) as a threat to its large carrier operations and acquisition!
I for one would love to see such a system installed on the RAN's new Canberra Class (Spanish Juan Carlos I Class) LHD's (But then again we are speaking about the Australian government and the ADF :'( )

 

[lastdingo]

You would save only a few metres T/O length by adding catapult features into the ski jump - not worth the effort.

 

[Abraham Gubler]

There's nothing wrong with using the full deck run of a STOVL carrier to launch a fighter, it hinders nothing. The STOVL carrier doesn't need to use its deck run part of the flight deck to spot aircraft before or after takeoff. Aircraft (including helicopters) are only positioned there for takeoff or landing. Aircraft being turned around are spotted on the starboard side of the flight deck. The ski jump with STOVL aircraft remains the most time, crew and fuel efficent way to get naval aircraft into the air. Adding a catapult to it will ruin the process for no return.

 

[F-14D]

The reasons why ski jumps are not used on Gators and on CVNs in the US actually make sense.

On a catapult equipped (be it steam, EMALS or the more advanced PMALS) CVN, they really don't offer any advantages. Want to gain that extra lift benefit? Just crank the cat up to throw the plane off the front of the boat harder. What you lose is deckspace available for parking. It's not at all uncommon to see a CVN launching off the starboard bow cat while there are planes parked on top of the port cat. With a ski jump, not only do you lose a good portion of that space, you also can't park as close to the takeoff area. A carrier with no catapults, of course, would be a different thing.

For the Marines, a similar situation applies. The AV-8B can launch with sufficient fuel and payload without the ski jump. The jump would, of course increase this, but it would also cost two-four helo operating spots. They don't think it's worth it, especially given they'll be using helos more than they'll be using the Harriers/F-35s.

There may also be a secondary concern. If you enable the STOVL to fly off with too much extra payload, the USN might decide at times to use the Marines' LH_ ships as mini carriers to relieve the CVNs.

Bottom line: for the USN/USMC ski jumps' acknowledged assets are outweighed by their liabilities.

 

[Arjen]

There may also be a secondary concern. If you enable the STOVL to fly off with too much extra payload, the USN might decide at times to use the Marines' LH_ ships as mini carriers to relieve the CVNs.

An interesting point, possibly more appropriate on a political forum.

 

[F-14D]

There may also be a secondary concern. If you enable the STOVL to fly off with too much extra payload, the USN might decide at times to use the Marines' LH_ ships as mini carriers to relieve the CVNs.

An interesting point, possibly more appropriate on a political forum.

Not really political. That secondary concern has been expressed by some in USMC before, including in print. Note how that for some years now, USMC F/A-18 squadrons have been assigned to CVNs for normal air wing operations, which is not what Marine Air is for. The USN gets to fill out its carrier decks while using part of the Marines' budget.

 

[Arjen]

The USN gets to fill out its carrier decks while using part of the Marines' budget.

Most likely with the consent of the politicians. If the marines draft specifications for hardware with the intent of denying secondary use of that same hardware by the navy, politicians should be interested.

 

[F-14D]

The USN gets to fill out its carrier decks while using part of the Marines' budget.

Most likely with the consent of the politicians. If the marines draft specifications for hardware with the intent of denying secondary use of that same hardware by the navy, politicians should be interested.

The politicians don't really get that deep into it. They basically define the Navy's role and what they want it to do then decide how much money they want to provide. Congress/the Administration rarely matches one to the other. Often there's not enough of the latter to accomplish the former. Since the Marines are part of the Navy and their budget is part of the Navy's it is not unheard of for the Navy to accomplish some of its roles using Marine assets and money (you-know-what rolls downhill). A parallel example would be how F-14s went in and out of Reserve squadrons. When the regular navy looked like it would come up short in the next FY for air ops, they'd transition a Reserve squadron to the Tomcat for a time, since the Reserves budget is a separate line item. Then when the money became available in the regular NAVAIR budget, they'd reassign the planes back to the regular "side".

The Marines don't draft specifications to deny USN use of their hardware. Remember, USN controls their budget, and the LH_s are Navy ships. The potential use of them as auxiliary carriers is only a secondary concern. The ships are designed to perform the mission the Marines need. For that mission, the ski jump doesn't offer enough extra to overcome the deckspace it costs.

 

[Arjen]

For that mission, the ski jump doesn't offer enough extra to overcome the deckspace it costs.

I agree.